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REQUEST FOR PROPOSAL

FOR

3G30A SOLAR CELL

ASSEMBLIES

AND

ALLIED MATERIALS FROM AZUR SPACE

May, 2016

ISRO SATELLITE CENTRE BANGALORE

RFP For Triple Junction Solar Cells i

CONTENTS

1. PREAMBLE ............................................................................................................... 1 2. SPECIFICATIONS / PERFORMANCE REQUIREMENTS ....................................... 1 2.1 DESCRIPTION OF SCA ............................................................................................ 2 2.2 SCA CONSTITUENTS .............................................................................................. 2 2.2.1 SOLAR CELL ............................................................................................................ 2 2.2.1.1 SUBSTRATE AND EPILAYERS ............................................................................... 2 2.2.1.2 ANTI REFLECTION COATING (ARC)...................................................................... 3 2.2.1.3 FRONT CONTACT .................................................................................................... 4 2.2.1.4 REAR CONTACT ...................................................................................................... 4 2.2.2 BYPASS DIODE ........................................................................................................ 5 2.2.3 SERIES INTERCONNECT ........................................................................................ 6 2.2.4 COVER GLASS ......................................................................................................... 7 2.2.5 BARE CELLS ............................................................................................................ 8 2.2.6 SEMI-BARE CELLS .................................................................................................. 8 2.3 SCA MASS ................................................................................................................ 9 2.4 SCA ELECTRICAL OUTPUT .................................................................................... 9 2.5 SCA RADIOMETRIC PROPERTIES ...................................................................... 10 2.6 WORKING STANDARDS ....................................................................................... 10 2.7 POSITIVE END TERMINATIONS ........................................................................... 11 2.8 NEGATIVE END TERMINATIONS ......................................................................... 12 2.9 REPAIR INTERCONNECTS/ INTERCONNECTS FOR PULL TESTS .................. 13 2.10 VISUAL INSPECTION CRITERIA ........................................................................... 13 2.11 SCA FUNCTIONAL CHARACTERISTICS ............................................................. 13 2.11.1 RELIABILITY ........................................................................................................... 13 2.11.1.1 FAILURE RATE....................................................................................................... 13 2.11.1.2 LIFE REQUIREMENTS ........................................................................................... 14 2.11.2 ENVIRONMENTAL REQUIREMENTS ................................................................... 14 2.11.3 PHOTON IRRADIATION REQUIREMENTS ........................................................... 14 2.11.4 REVERSE CHARACTERISTICS REQUIREMENTS .............................................. 14 2.12 MATERIALS AND PROCESSES ............................................................................ 15 2.13 BENDING RADIUS ................................................................................................. 16 2.14 SCA BOWING ......................................................................................................... 16 2.15 CLEANLINESS AND MARKING ............................................................................ 16 2.16 WORKMANSHIP ..................................................................................................... 17 2.17 INTERCHANGEABILITY AND UNIFORMITY OF PRODUCT ............................... 17 2.18 QUALIFICATION AND HERITAGE ........................................................................ 17 2.19 PARTICIPATION AND CO-OPERATION ............................................................... 18 2.20 STORAGE ............................................................................................................... 18 2.21 TRANSPORTATION ............................................................................................... 18 3. PRODUCT ASSURANCE RELIABILITY AND TESTS .......................................... 19 3.1 QUALIFICATION AND ACCEPTANCE TEST REQUIREMENTS ......................... 20 3.1.1 QUALIFICATION REQUIREMENTS....................................................................... 20 3.1.1.1 PROCESS IDENTIFICATION DOCUMENT (PID) .................................................. 20 3.1.1.2 PRODUCTION CONTROL ...................................................................................... 21 3.1.1.3 QUALIFICATION TESTS ........................................................................................ 21 3.1.2 PANEL LIFE-TEST COUPON ................................................................................. 32 3.1.3 LOT ACCEPTANCE TESTS(LAT) ........................................................................... 33 3.2 QUALIFICATION TESTS AT ISRO ........................................................................ 35 4. TEST METHODS AND CONDITIONS .................................................................... 37 4.1 VISUAL INSPECTION ............................................................................................. 37 4.2 DIMENSIONS .......................................................................................................... 37 4.3 SCA MASS .............................................................................................................. 37 4.4 ELECTRICAL PERFORMANCE ............................................................................. 38 4.5 TEMPERATURE COEFFICIENTS .......................................................................... 39 4.6 WELDED CONTACT INTEGRITY .......................................................................... 39 4.7 CONTACT UNIFORMITY ........................................................................................ 39 4.8 THERMAL CYCLING TEST .................................................................................... 40

RFP For Triple Junction Solar Cells ii

4.9 HUMIDITY ................................................................................................................ 40 4.10 IRRADIATION ......................................................................................................... 41 4.10.1 PARTICLE IRRADIATION ...................................................................................... 41 4.10.1.1 ELECTRON IRRADIATION & PROTON IRRADIATION........................................ 42 4.10.2 PHOTON IRRADIATION ......................................................................................... 44 4.10.3 PHOTON IRRADIATION (SHORT DURATION) ..................................................... 45 4.10.4 UV IRRADIATION (FOR SCA ONLY)..................................................................... 45 4.11 RADIOMETRIC PROPERTIES ............................................................................... 45 4.11.1 SOLAR ABSORPTANCE ....................................................................................... 45 4.11.2 HEMISPHERICAL EMITTANCE ............................................................................. 45 4.12 CONTACT AND COATING ADHERENCE ............................................................. 46 4.12.1 TAPE PEEL TEST ................................................................................................... 46 4.13 INTERCONNECT FATIGUE ................................................................................... 46 4.14 SPECTRAL RESPONSE ........................................................................................ 46 4.15 REVERSE BIAS SCREENING ................................................................................ 47 4.16 ANGLE OF INCIDENCE TEST ............................................................................... 47 4.17 SHADOW TOLERANCE TEST ............................................................................... 47 4.18 BY PASS DIODE/SCA LIFE TEST ......................................................................... 48 4.19 THERMAL VACUUM SOAK ................................................................................... 48 4.20 CAPACITANCE MEASUREMENT ......................................................................... 48 5. PACKAGING, DELIVERY AND SCHEDULES ....................................................... 49 5.1 PACKAGING ........................................................................................................... 49 5.2 TRANSPORTATION AND PACKAGING ACCEPTANCE ..................................... 49 5.3 DELIVERABLE DOCUMENTS ............................................................................... 49 5.3.1 DATA/ DOCUMENTS REQUIREDALONG WITH THE PROPOSAL ..................... 50 5.3.2 ALONG WITH PID ................................................................................................... 52 5.3.3 ALONG WITH EACH LOT OF SCA ........................................................................ 53 5.4 HARDWARE DELIVERABLES ............................................................................... 54 ANNEXURE A – ENVIRONMENTAL REQUIREMENTS ................................................................... 56 A1. PRE-DEPLOYMENT ............................................................................................... 56 A2. DURING DEPLOYMENT ......................................................................................... 57 A3. POST DEPLOYMENTS ........................................................................................... 56 A4. RADIATION ............................................................................................................. 57 A4.1. GEO ORBIT ............................................................................................................. 57 A4.1.1. ELECTRON RADIATION ........................................................................................ 57 A4.1.2. PROTON RADIATION ............................................................................................ 58 TABLE 2A: PROTON FLUX - LOW ENERGY ..................................................................................... 58 TABLE 2B :PROTON FLUENCE - SOLAR FLARE ............................................................................ 59 A4.2 PLASMA .................................................................................................................. 59 A4.3 MICROMETEOROIDS ............................................................................................. 59 A4.4 SOLAR RADIATION ............................................................................................... 60

RFP For Triple Junction Solar Cells for Indian Space Program 1 of 61

REQUIREMENT RESPONSE FROM THE VENDOR

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1. PREAMBLE

Indian Space Research Organization (ISRO) is designing, fabricating, testing,

and launching its own satellites for different applications. These satellites are

launched by either own launch vehicle or being launched by other launch

vehicles. These satellites are powered using photovoltaic generated power for

its application. The solar arrays for power generation are also designed,

fabricated and tested in-house. The proposed Solar Cell Assemblies (SCAs)

also called as Cover Glass Integrated Cells (CICs) are to be procured for use

in one or more GEO/ LEO spacecraft.

2. SPECIFICATIONS / PERFORMANCE REQUIREMENTS

This chapter gives the details of the specification and/or performance

requirements of the hardware being procured viz.

♦ Cover glass Integrated cells (SCAs)

♦ Hand held working standard SCAs (Secondary Standard SCAs)

♦ Positive end terminations

♦ Negative end terminations and

♦ Interconnects for pull tests

♦ Repair Interconnector

♦ Coverglass

♦ Bare Cells



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♦ Semi-bare cells - Fully fabricated super epi-wafers up to rear

contact metallization and ready for dicing.

An assessment on all specifications of hardware mentioned in this document

as provided by vendor will be done by ISRO.

2.1 DESCRIPTION OF SCA

The SCA and each constituent of the SCA offered shall be fully qualified to

meet the qualification and heritage requirements mentioned in 2.18. Each SCA

shall consist of:

• A monolithic and epitaxially grown n/p triple junction solar cell on Ge-

substrate,

• with built-in discrete Silicon bypass diode (SIBD)/ Monolithic diode, which

is integrated to the cell for protection of the self (mother) cell or the

neighboring cell.

• A series interconnect welded to the front contact to carry the power with

adequate redundancy and

• Cover glass bonded to the solar cell using DC 93500.

2.2 SCA CONSTITUENTS

2.2.1 SOLAR CELL

2.2.1.1 SUBSTRATE AND EPILAYERS

The solar cell shall consist of a mono crystalline germanium substrate of 40



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mm x 80 mm nominal size & Smaller size cells around 10 cm2 and 140

microns nominal thickness with two cropped corners with various suitably

doped and epitaxially grown layers which constitute the triple junction solar

cell. The vendor shall specify the following details about the solar cells.

• Nominal, minimum and maximum dimensions of the solar cells.

• Nominal, minimum and maximum thickness of the Ge substrate

• Nominal, minimum and maximum thickness of the solar cells

• Resistivity of the Ge substrate

• Cross sectional drawing of the solar cell specifying the materials and

polarity of all the layers of the solar cell such as nucleation layer, buffer

layer, BSFs, windows, tunnel junctions, cap layer, contacts and anti-

reflection coating (ARC) including active solar cell junctions.

2.2.1.2 ANTI REFLECTION COATING (ARC)

The front surface of the solar cell shall have multi-layer ARC of TiOx and

Al2O3. The coating material shall be designed to maximize the end of life

electrical output from the SCA. The ARC shall not delaminate, deteriorate

and/or degrade the performance of the SCA during fabrication, testing, storage

and use of the SCAs to fabricate solar panels. The vendor shall specify the

ARC material, its thickness and optical properties including the solar cell

reflectance curves. Vendor shall also specify the total uncoated AR-area as a



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percentage of the cell area.

2.2.1.3 FRONT CONTACT

The front contact geometry shall consist of pads for interconnection and

gridlines for current collection and reducing series resistance. The front

electrical contact of the solar cell shall be made of suitable contact material

and compatible for resistance welding process. The outermost layer of the

contact shall be silver of 5 µm (nominal thickness) and shall have an Au flash

on top of around 50 – 100 Å. The front contact shall be free of solder. The

vendor shall specify the following:

• Composition of the front contact and gridline material.

• Geometry of the front contacts and gridlines

• Location of the front contact pads in the solar cell

• Nominal, minimum and maximum thickness of each metal layer

• Front contacts and gridline area as a percentage of the solar cell area

• Surface roughness

2.2.1.4 REAR CONTACT

The rear electrical contact shall be deposited throughout the back surface of

the cell and shall be made of suitable contact material such that the outer layer

is silver of nominally 5 microns thickness with gold flash and compatible for

resistance welding process. The rear contact shall be free of solder. The



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vendor shall specify the following.

• Composition of the rear contact

• Nominal, minimum and maximum thickness of each layer

• Surface roughness of the rear contact

2.2.2 BYPASS DIODE

The bypass diode shall be a discrete/monolithic diode attached to the solar

cell. The bypass diode shall protect the solar cell from all electrical stresses

induced by full or partial shadow of the SCA, induced by other SCAs

connected in series and parallel and those induced by the test and switching

electronics. The interconnection between the solar cell and the bypass diode

shall be fully space qualified preferably with redundant interconnections at

both cathode and anode sides. In addition, the diode current carrying capacity

shall have sufficient de-rating to carry the light generated current and also to

carry the switching transients induced by Power Control Unit (PCU) due to the

solar cell junction capacitance. The vendor shall specify the following:

• Diode construction including materials used and thickness.

• Interconnection between solar cell and diode including the location of the

diode in the SCA.

• Diode-solar cell interconnect material, thickness, and geometry and weld

location.

• Electrical parameters including, current capacity, forward voltage drop at



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specified currents, PIV, leakage current at specified reverse voltages,

reverse recovery period and junction capacitance.

• Visual inspection criteria for diode acceptance.

• Flight heritage / Qualification of the bypass diode including when used as

a part of the SCA proposed.

• Documentary evidence for compliance to the functional requirements

after experiencing the environments specified in Annexure1.

• The Diode I/C shall be compatible with ISRO lay-down process in which

RTV S 691 / equivalent adhesive covers 100% of the area beneath the

diode and diode I/C

2.2.3 SERIES INTERCONNECT The series interconnect shall be made of 25 µm nominally thick silver plated

kovar (i.e.15 µm (nominal) thick Kovar with a nominal of 5 microns thick silver

coating on all sides) with a Au flash like cell rear contact. The interconnects

are attached to the p and n cell contacts by multiple cell welds. Interconnect

shall be compatible for resistance welding to the solar cell described in para

2.2.1 and shall be free of solder. The series interconnect shall be designed to

meet the following requirements:

• Shall have two or three tabs per cell + one tab for diode, each capable of

carrying the full solar cell generated current.

• Shall have two prongs per tab and shall be welded on top front contact



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pad

• Shall have stress relief loops to withstand fatigue induced by thermal

loads due to the mismatch between the SCA and solar panel substrate

with CFRP face sheets during GEO (2025 thermal cycles between

+130°C and -165°C and 4500 cycles between +130°C and -100°C)

missions.

• Shall be designed such that it should not abrade / puncture Kapton

insulation of 50 microns thickness.

• Shall be easy to handle.

• Shall not deform/damage due to handling and transportation.

The vendor shall provide the following details related to series interconnect:

• Dimensional drawing of the proposed interconnects with tolerances.

• Material and thickness of interconnect, including coatings if any.

• Interconnect flight heritage/ qualification of the proposed Interconnect life

for 15 year GEO mission shall be supported by the ground coupon test or

any other test and necessary analysis.

2.2.4 COVER GLASS

The cover glass shall be made of cerium oxide stabilized micro sheet of CMX

type from M/s Qioptiq, coated with MgF2 antireflection coating. The cover glass

maximum size shall be chosen by the vendor to cover the solar cell and by-

pass diode fully with the cover glass overhang not exceeding 250 micron on



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any side. The cover thickness shall be 150 ± 20 micron. Inverted coverglasses

with the ARC oriented toward active cell area are not permissible and

coverglasses shall have an etch symbol/ edge stain to ensure proper

installation. Cover glass shall be bonded to the cell with DC 93500 adhesive.

The thickness variation of the SCA after cover glass bonding shall be

controlled to ensure uniform glue line thickness over the solar cell area and

between SCA to SCA. The vendor shall provide the following details of the

cover glass and cover glass bonding adhesive:

• Nominal, minimum and maximum dimensions of the cover glass.

• Minimum and maximum overhang on each side of the SCA

• Nominal, minimum and maximum glue line thickness of cover glass

bonding adhesive. The cover glass bonding adhesive thickness

variations within a SCA and from SCA to SCA shall be minimum.

Allowable variation shall be specified by the vendor.

2.2.5 BARE CELLS

The bare cells shall have the same dimensions and shall be chosen from the

same MOCVD production lot/batch of SCAs to be delivered under this

contract.

2.2.6 SEMI-BARE CELLS The fully fabricated epi wafers up to the rear contact metallization and ready

for dicing (semi- bare cells) shall have the same contact configuration as the

SCAs and shall be configured for dicing two bare cells from one wafer. Vendor



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shall specify the edge exclusion to be considered while dicing the cell from the

wafer. These wafers shall be chosen from the same MOCVD production

lot/batch of SCAs to be delivered under this contract. The process and

qualification used in semi-bare cells shall be same as those for the SCAs.

2.3 SCA MASS

The vendor shall specify the average, minimum and maximum SCA mass.

2.4 SCA ELECTRICAL OUTPUT

Each SCA shall be capable of converting artificial or natural radiant solar

power as found outside the earth's atmosphere (1367 W/m2, WMO Spectrum)

into electrical power. The electrical performance of the solar cell/ SCA shall be

measured as per 4.4. The vendor shall specify a test voltage VT. The SCA

power output is defined as the product of VT and current at VT, henceforth

referred to as IT at 28°C. Vendor shall specify the SCA efficiency at VT

considering the solar cell active area and also considering the area of the

rectangle of sides equal to the maximum length and breadth of the cover

glass. The shipping lot average efficiency of SCAs considering the solar cell

area shall be greater than 28% at 28°C under 1 AM0. The minimum efficiency

of any SCA at 28°C under 1 AM0, in a shipping lot shall be within 95% of the

average efficiency. No SCA in the shipping lot shall have a Vmp lesser than VT-

50mV. The SCAs shall be grouped based on current at VT at 28°C with a



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bandwidth of 5mA.

The vendor shall specify the following electrical parameters of the SCA:

• Lot average, maximum and minimum efficiency of the SCAs as defined

above.

• VT (test point voltage) & Current at Vmp/2 and (Vmp +Voc)/2 [email protected] and I

@2.55V.

• Sun simulator(s) used and its spectral composition comparison with AM0,

over the wavelength band of interest, in the form of a tables and plots.

2.5 SCA RADIOMETRIC PROPERTIES

The solar absorptance in the non-operating condition and total hemispherical

emittance of the SCA top surface shall be specified by the vendor.

2.6 WORKING STANDARDS

A set of secondary working standards that include one full SCA and three

other SCAs consisting each any one of the top, middle or bottom junctions

with the other junctions simulated optically (i.e. iso type top, middle or bottom

junctions). The working standards calibration shall be traceable to a Shuttle /

balloon flown primary standard of the same type as the SCAs under

measurement. The working standard set shall be used to set the solar

simulator for electrical evaluation of the SCAs. The vendor shall provide the

following information related to the working standards:

• Cross section drawing including material and thickness of the various



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layers in each of the four SCAs that constitute a set of working

standards.

• Working standards calibration procedure specifying the primary

standard reference.

• Full I-V characteristics and spectral response in the form of a table

and plots for the full set of four SCAs of the working standards.

• Full dark I-V characteristics with digital data for the full set of four

SCAs of the working standards. This can be optional and shall be

discussed with vendor.

• Measured values of Series and Shunt Resistance of the four SCAs of the

working standards.

• A calibration certificate for each of standard SCAs supplied.

2.7 POSITIVE END TERMINATIONS

• These are assembly of interconnects and a terminal bus bar to be used

as the solar cell string positive termination with a provision to solder/ weld

multiple wires. The interconnect part shall be similar to the series

interconnect of the SCA and all specifications of 2.2.3 shall be applicable.

The termination part shall be a separate piece with provision for wire

termination and the interconnect part welded/ weldable to it. Silver plated

positive end terminations (bus bars) shall be made of Kovar material. The

positive end terminations shall be 75 μm (3 mil) thick kovar base material



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with 5 µm silver plating on each side and shall have Au flash like cell

rear contact. It requires three tubules at located such that the

interconnect and wire welding/ soldering don't affect each other. Material

of the positive end termination shall be the same as series interconnects.

The design of the positive end termination shall take into account the

aspects of translational and rotational forces encountered by it in the

panel during thermal cycling. The vendor shall provide data on the

positive end termination in similar lines as specified for the series

interconnect in 2.2.3. The component drawing shall be provided. Vendor

is free to offer an alternate design for the positive end termination to meet

the functional requirements specified.

2.8 NEGATIVE END TERMINATIONS These are similar to the positive termination without the interconnect part such

that after welding to the SCA series interconnect they provide wire welding/

soldering interface for the string negative termination. The design of the

negative end termination shall take into account the aspects of translational

and rotational forces encountered by it in the panel during thermal cycling. The

vendor shall provide data on the negative end termination in similar lines as

specified for the series interconnect in 2.2.3. The component drawing shall be

provided. Vendor is free to offer an alternate design for the positive end

termination to meet the functional requirements specified.



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2.9 REPAIR INTERCONNECTS/ INTERCONNECTS FOR PULL TESTS These are series interconnects used in the SCAs without the stress relief

loops. The vendor shall provide data on the interconnects for pull test, in

similar lines as specified for the series interconnect in 2.2.3. The series

interconnects; end terminations and Pull test interconnects when welded/

soldered shall have pull strengths per tab of 300 gram force and 150 gram

force when pulled at 0°and 45°respectively.

2.10 VISUAL INSPECTION CRITERIA Vendor shall provide its own standard visual inspection (VI) criteria for the

hardware being procured like solar cell, interconnects, bypass diode,

coverglass and its bonding process. The VI criteria shall be discussed with

ISRO and mutually agreed upon before the contract.

2.11 SCA FUNCTIONAL CHARACTERISTICS

2.11.1 RELIABILITY The SCA and allied material shall meet the operational requirements given

below. Reliability shall be considered of prime importance in the design and

manufacture of the CSAs and allied material.

2.11.1.1 FAILURE RATE

Each SCA shall have an average failure rate of less than 1x 10-9 failures per

hour.



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2.11.1.2 LIFE REQUIREMENTS

The CIC shall meet the requirements specified in this document for use in

GEO as well as LEO missions after storage for a maximum of five years under

specified conditions, in addition to the various tests on ground and

the manufacturing process of the solar array.

The CIC and the allied material and processes shall be compatible with ISRO

lay-down process in which adhesive (RTV S 691) covers 100% of the area

(grouting) beneath the CIC, series I/C and bypass Diode I/C.

GEO Requirements: 2025 thermal cycles between +130°C and -165°C and

4500 cycles between +130°C and -100°C

LEO requirements: (45000 cycles between +110°C and -100°C) missions

2.11.2 ENVIRONMENTAL REQUIREMENTS

Environments generally seen by the SCA and interconnects as a part of the

solar array are detailed in the Annexure 1. The SCA and the allied materials

shall be designed to meet the performance requirements before, during and

after exposure to the environments specified.

2.11.3 PHOTON IRRADIATION REQUIREMENTS

SCA design/manufacturing process shall be such that the SCAs shall not

degrade when exposed to standard AM0 spectrum throughout the mission life

of 15 years in GEO with 50% safety margin as specified in 2.11.1.2.

2.11.4 REVERSE CHARACTERISTICS REQUIREMENTS

The reverse characteristics of the SCAs shall be such that no SCA will have



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any permanent damage resulting in degradation of I at VT after the SCA is

biased in the reverse.

2.12 MATERIALS AND PROCESSES

The selection, documentation, qualification, approval and control of all parts,

materials and processes for the SCAs and allied materials shall be in

accordance with the reliability and quality assurance provisions of chapter 3.

All the SCAs and allied materials supplied to the specifications of this

document shall allow assembly after shipment handling and storage for 5

years and thereafter meet all the requirements. No material should be used in

the manufacture of SCAs, which are not compatible with the following

processes.

• Assembly into modules by parallel gap resistance welding.

• Bonding of the modules to a 50 microns thick Kapton insulator over a

CFRP substrate using Wacker-Chemie RTV-S-691 Silicone. No oil,

grease or similar material, including adhesive tapes shall come in

contact with any portion of the SCAs and allied materials during

manufacture and testing.

• All the materials used in fabrication of SCAs and the allied material

shall be magnetically clean except interconnect in the solar cell contact.

However, these should not affect the solar array performance.

• Materials shall comply with the flammability, out gassing and other

requirements of NASA, ESA or ASTM applicable standards.



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• Cleaning solvents used in fabrication of solar cells shall not leave traces

of corrosive ions that can affect the performance of the cell, e.g.

chlorides, fluorides, sulphides, etc.

2.13 BENDING RADIUS

• The bending radius of the SCA, in a solar panel, shall be less than or

equal to 2 meters. When bent to 2 meter radius, the cell electrical and

mechanical performance shall not degrade. Vendor shall specify the

bending radius of the SCA being offered.

2.14 SCA BOWING

The SCA when placed with cover glass down free on a stable surface plate

shall not bow more than 250 μm (typical) in either convex or concave. The

vendor shall specify the nominal, minimum and maximum SCA bowing

parameter and shall demonstrate on a minimum of 32 SCAs during lot

acceptance.

2.15 CLEANLINESS AND MARKING

• Each SCA shall be fabricated in a clean environment to allow

weldability, bondability and stability of electrical output under standard

AM0 spectrum. The SCAs as received from the Vendor shall be

weldable by resistance welding and bondable using RTVS 691

adhesive without any cleaning. Each SCA shall have a UID (unique ID)

and a 2D barcode i.e. each Each SCA shall be numbered uniquely so

that traceability of different processes such as MOCVD, evaporation,



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SCA batch information, etc can easily be identified.

• The marking fixed at the center of the rear contact of the cell (away

from the rear weld zone) shall be readable after cleaning with water.

propanol or acetone and any environmental test. The marking shall not

affect the electrical, mechanical and environmental properties of the

SCAs and shall not interfere with the welding and bonding of the SCAs

2.16 WORKMANSHIP

The workmanship shall meet or exceed Vendor' manufacturing and process

standards that are documented and controlled and shall be approved by

ISRO. The vendor shall use only trained and certified personnel and

equipment to realize the SCAs offered.

2.17 INTERCHANGEABILITY AND UNIFORMITY OF PRODUCT

The SCAs shall provide for maximum interchangeability among similar group

of items. All SCAs shall be manufactured as per approved process

identification document (PID). The manufacturing process and materials used

shall be same as those of used in qualification testing of the cell/SCA as

described in chapter 3. No changes in vendors, materials, fabrication

technique, assembly procedures and inspection are allowed. If any change is

warranted, it shall be informed to ISRO for approval. ISRO reserves the right

to insist for additional qualification at the vendor’s cost.

2.18 QUALIFICATION AND HERITAGE

The vendor shall provide documentary evidence on the qualification status of



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the SCAs and allied material for use on commercial geo-stationary (15 years)

spacecraft and / or 5 years in low earth orbits as per existing industry

standards. The SCA offered by the vendor shall be from the regular cell

production line of the heritage space solar cell. The qualification shall be

demonstrated through in-flight heritage and/or ground testing.

2.19 PARTICIPATION AND CO-OPERATION

Vendor is expected to facilitate the participation of ISRO representatives

during design review, fabrication, qualification and lot acceptance. If any of the

tests done at other than Vendors premises, Vendor shall agree and facilitate

ISRO′s participation. ISRO reserves the right to position a resident engineer at

the vendor premises for the duration of manufacture and testing of hardware

deliverable under this contract. Vendor shall confirm concurrence and facilitate

this.

2.20 STORAGE

Each SCA shall meet all the requirements of this document after storage for a

minimum period of five years. Vendor shall specify the storage

conditions/procedure.

2.21 TRANSPORTATION

The SCAs and the allied material shall be transportable by air/ship and road,

when packed as per Chapter 5 of this document.


REQUIREMENT RESPONSE

FROM THE VENDOR

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3. PRODUCT ASSURANCE RELIABILITY AND TESTS

The vendor quality assurance requirements shall have applicable documents

for maintaining the overall quality, in addition to the tests and test philosophies

described herein:

The vendor shall be responsible for verifying all the requirements of this

specification in accordance with the following product assurance and reliability

specifications. The vendor shall also be responsible for compliance with all the

requirements of Chapter 2.0. One or more of the following methods shall

carry out verifications:

A. Analysis

B. Demonstration

C. Inspection

D. Test

Any specific test performed by ISRO instead of the vendor shall not relieve

vendor of the responsibility of compliance with all the requirements of

Chapter 2.0. The qualification and acceptance tests shall be carried out in

accordance with the test procedures approved by ISRO. Records of all tests

and equipment used shall also be maintained. ISRO reserves the right to

witness all or any of the tests. Records shall be maintained for at least 10

years in the form of permanent files and to be made available to ISRO for



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scrutiny as and when required. Failure or non-conformance during any stage

of qualification, manufacture or testing shall be immediately informed to ISRO.

A report giving details of failure, failure analysis, remedial action and impact of

the failure on schedules and performance of the SCAs shall be submitted to

ISRO and approval shall be obtained.

3.1 QUALIFICATION AND ACCEPTANCE TEST REQUIREMENTS

3.1.1 QUALIFICATION REQUIREMENTS

3.1.1.1 PROCESS IDENTIFICATION DOCUMENT (PID)

Vendor shall submit for approval, the Process Identification Document (PID)

describing the steps necessary to meet the requirements spelt out in Chapter

2. In order to optimize cost, quality and schedules these steps should utilize

the existing procedures, which have been established over the years as a

result of in-house programs. In case of variations to comply with the

requirements, the same may be proposed in details and sequence. The PID

should include, though not necessarily limited to the following:

• A detailed specification showing component parameters and other

data to fully describe the SCA, its components and the allied materials

proposed to be supplied.

• A detailed flow chart, showing all processing steps involved in the

production of the SCAs and the allied materials. A list of QA checkpoints

during manufacture of the SCAs shall be included.

• A product flow chart, including the qualification and acceptance tests.



REMARKS IF ANY

• Mechanical drawing of the SCAs and the allied materials, which complies

with the specifications and reflects the hardware configuration when

delivered.

3.1.1.2 PRODUCTION CONTROL The vendor shall have complete traceability and lot control over the complete

production flow line beginning from the wafer stage to SCA. The vendor shall

have SPC (statistical process control) charts for all materials, process and

tests. The lot control shall include information and traceability of wafer lot

used, the raw material, processing information, date of processing, operator

and equipment used to realize the SCA. ISRO reserves the right to station a

resident engineer at VENDOR’s facility for the period of the contract, to

monitor the hardware manufacture.

3.1.1.3 QUALIFICATION TESTS The qualification tests to be performed on SCAs shall demonstrate that the

SCAs satisfy the test requirements described below. Vendor shall provide

documentary proof that the SCAs being offered have successfully undergone

the ground qualification tests, meeting or exceeding the international

standards such as ECSS*-E-ST-20-08C, AIAA**S-111-2005, etc. The test

conditions shall equal or exceed the ground, launch and in orbit conditions so

as to locate the deficiencies and margins. However, ISRO reserves its right

to conduct a Type Approval Test (TAT) if deemed necessary. The TAT has to



REMARKS IF ANY

be conducted in presence of ISRO representative at vendor’s premises. The

typical TAT sequence shall include but not limited to the following. The tests

shall be conducted in the sequence indicated and shall demonstrate

compliance with the respective requirements. Tests of group A, C and G shall

be conducted on bare cells while group F tests, shall be conducted on series

interconnects. The remaining tests shall be conducted on SCAs. Vendor

shall quote for TAT giving the breakup in price for each test group. ISRO

reserves the right to conduct any or all of these tests.

*ECSS : European Cooperation for Space Standardization

** AIAA : American Institute of Aeronautics and Astronautics

The significant requirements of the groups are as follows:

Group A - Top contact welding and thermal cycling.

32 bare cells with series interconnects welded to the top contact

Initial pull test on 10 similar samples shall be used as reference value.

Test Sequence Para Reference Appearance 4.1

Dimension 4.2

Mass 4.3

Electrical Output 4.4



REMARKS IF ANY

Top contact welding 4.6

Appearance 4.1

Electrical output 4.4

Thermal cycling 4.8

Appearance 4.1


Photon Irradiation 4.10.3

Appearance 4.1


Contact Integrity 4.6



REMARKS IF ANY

Group B - Rear contact welding and thermal cycling 32 SCAs with series interconnects welded to the rear contact

Initial pull test on 10 similar samples shall be used as reference value.

Test Sequence Para Reference

Appearance 4.1

Dimension 4.2

Mass 4.3


Diode Characteristics TBD*

Welding 4.6

Appearance 4.1


Thermal cycling 4.8

Appearance 4.1


Diode characteristics TBD*


Appearance 4.1


Contact Integrity 4.6



REMARKS IF ANY

* The test process shall be mutually agreed between the vendor and ISRO. Group C Particle Irradiation: Group C1- Particle Irradiation (Electron) - 36 bare cells .


Appearance 4.1

Dimension 4.2

Mass 4.3


Radiometric Properties 4.11

Temperature Coefficients 4.5

Spectral Response 4.14


Electron Irradiation 4.10.1.1

Photon irradiation 4.10.3

Appearance 4.1


Radiometric properties 4.11





REMARKS IF ANY

Group C2 - Particle Irradiation (Proton) - 84 bare cells.


Appearance 4.1

Dimension 4.2

Mass 4.3


Diode characteristics TBD*





Proton Irradiation 4.10.1.2


Appearance 4.1







REMARKS IF ANY

Group D - Humidity - 32 SCAs


Dimension 4.2

Mass 4.3


Humidity 4.9

Tape peel test 4.12.1

Appearance 4.1


Thermal Vacuum Soak 4.19

Appearance 4.1



Appearance 4.1


Tape Peel Test 4.12.1

Group E - UV Irradiation - 32 SCAs



REMARKS IF ANY


Dimension 4.2

Mass 4.3

Group F - Interconnect fatigue (32 Series Interconnects)


Appearance 4.1

Dimension 4.2

Interconnect fatigue 4.13

Group G - Contacts, AR coating integrity-32 bare cells


Appearance 4.1

Dimension 4.2

Mass 4.3



Appearance 4.1


Coating Adherence 4.12

Group H - Angle of Incidence, Shadow Tolerance Test-32 SCAS



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Dimension 4.2

Mass 4.3


Angle of Incidence 4.16

Appearance 4.1


Shadow Tolerance 4.17

Appearance 4.1


Group I - Photon Irradiation Test-32 SCAs


Appearance 4.1

Dimension 4.2

Mass 4.3



Appearance 4.1




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Group J - BYPASS Diode/ SCA Life Test-32 SCAS


Dimension 4.2

Mass 4.3


Bypass Diode/ SCA Life Test 4.18

Appearance 4.1


Group K – Diode Electrical Performance Test (to be specified by the vendor) Group L – Diode Environmental Test (to be specified by the vendor) For the external bypass diode offered, the vendor shall provide documentary

evidence that the diodes as sub-assembly components have been qualified

fully on ground. The tests on the bypass diodes shall include performance

evaluation tests and environmental tests. These tests shall generally be

particle irradiation test on the diode (which includes proton and electron

irradiation), post particle irradiation performance evaluation, UV irradiation

test, thermal soaking and cycling, humidity, panel level thermal cycling and

reverse voltage test and any other tests deemed necessary for the shunt

diode performance evaluation.



REMARKS IF ANY

The vendor shall also provide the following details

i) Lot number and batch number details of the diode

ii) Lot Acceptance Test (LAT) results of the diode.

iii) Screening of these diodes.

iv) Storage aspects of these diodes.

v) Preferred interconnection.

The samples for the TAT may be selected by the internal QA at random, from

the first production lot of TBD size. After selecting the TAT test samples with

necessary spares, the remaining SCAs of this first lot shall be delivered to

ISRO for its own qualification testing including those for the lay-down process.

The remaining SCAs production shall be authorized only after successful

completion of the TAT at vendor and tests at ISRO.

The TAT samples shall contain SCAs from each group of current classification

such that the average power output of the samples at 28°C measured under

WMO standard AM0 spectrum is equal to the lot average. The samples

selected for each group shall have representation of a minimum two MOCVD

and two evaporation lots. If more than one type of reactor, evaporation/ARC

unit is planned for production, samples processed by each type of unit shall be

included. In the event of accidental damage to sample, SCAs prior to the

completion of the test sequence, each such SCA shall be replaced by a new

SCA of the same lot and the new SCAs shall be subjected to all the tests of

that sequence. Failure to meet the requirements of this specification of any



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group during qualification testing will call for retesting at the cost of vendor

with a new sampling plan mutually agreed with ISRO. The failures shall be

analyzed and suitable corrective actions shall be implemented accordingly.

The vendor shall demonstrate the qualification so as to verify the implemented

corrective actions would satisfy the qualification requirements.

The vendor shall provide the non-conformance report and the management of

non-conformances.

3.1.2 PANEL LIFE-TEST COUPON

Four numbers of Flight quality panel coupons manufactured by the vendor /

ISRO including circuits of SCAs and the positive and negative end

terminations proposed and samples of repaired SCAs will be subjected to an

accelerated thermal cycling life test as per 2.11.1.2., to demonstrate

the capability to survive the GEO / LEO orbital environment. The coupon

substrate will be provided by ISRO. 5 TVAC before and after cycling. The

coupon will also undergo tests to verify its performance in the acoustic,

vibration, and shock environments of Annexure 1.

Coupon ESD tests: One of the fabricated coupons shall be subjected to ESD

tests as per ECSS or AIAA test methods that can be agreed upon at the time

of contract finalization.

The Test coupons fabrication cost, accelerated life testing cost and ESD test

cost shall be quoted by the vendor with item wise breakup. The configuration



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of the coupon and test plans shall be mutually agreed between ISRO and the

vendor at the time of contract. ISRO reserves the right to carry out any or all

the tests specified.

3.1.3 LOT ACCEPTANCE TESTS (LAT) Lot Acceptance tests (LAT) shall be performed by vendor for every 10000

CICs shipped to ISRO as per test methods described in Chapter 4.0 and shall

be witnessed and certified by ISRO or a third party, agreed mutually between

ISRO and the vendor. The acceptance tests are described in table below:

1. For SCAs, BARE CELLS, SEMI-BARE CELLS

REQUIREMENT Test Method

SCAs

Bare Cells

Semi-Bare Cells

SAMPLE SIZE

Appearance 4.1 √ √ √ 100% In process

Identification 4.1 √ √ TBD 100% In process

Dimensions 4.2 √ √ TBD LTPD-7 – No failure

Bowing 4.2 √ √ † LTPD-7 – No failure

Mass 4.3 √ √ √ 100 samples per lot

Electrical output 4.4 √ √ TBD 100% In process

Contact uniformity 4.7 √ √ † In process,

on wafer edges



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Weld Contact

Integrity Test

(Rear)

4.6 √ † † LTPD-7-No failure

Humidity # 4.9 √ † † LTPD-7-No failure

Photon Irradiation 4.10.2 √ † † LTPD-7 No failure

Contact & Coating

Adherence

4.2 √ † † In process,

on wafer edges

Reverse Bias

Screening

4.15 √ √ TBD 100% In process

2. For ALLIED MATERIALS and RAW MATERIALS

MATERIAL SAMPLE SIZE

Series

Interconnect*

The results of the acceptance tests carried out by the sub-

contractor(s) and the incoming inspection by vendor shall

be included in this lot EIDP.

Positive End

termination*

Negative End

termination*

Interconnect for

pull test*

Bypass Diode*

Ge Wafer

Coverglass

Cover glass



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bonding adhesive

(DC 93500)

# Except the humidity test and Weldability tests, all other acceptance tests are nondestructive and hence the tests may be conducted on samples selected

from the shipping lot. Weldability tests are to be carried out on 32 SCAs and

32 weld samples have to be realized from them. Humidity test are to be

carried on 32 SCAs. The humidity and Weldability SCA samples shall be long

to the same manufacturing lot as the shipping lot but not part of the shipping lot.

* Vendor to specify.

ISRO reserves the right to carry out any additional test(s) mentioned in

qualification test plan if necessary, after discussing with the vendor. The

acceptance test plan, sample size for such tests shall be finalized after

discussion.

3.2 QUALIFICATION TESTS AT ISRO

• A development model Panel/ Coupon will be fabricated by ISRO using

flight representative CFRP substrate and the first lot SCAs supplied by



REMARKS IF ANY

the vendor. This panel will be subjected to qualification level acoustic,

vibration and thermovac cycling. The test conditions and acceptance

criteria will be supplied to the vendor and in case of failure in any of

these tests, vendor will assist ISRO in resolving the problem.



FROM THE VENDOR

REMARKS IF ANY

4 TEST METHODS AND CONDITIONS The in-process, qualification and acceptance tests for the SCAs and allied

materials manufactured according to the required specification shall be

performed in accordance with the test methods and test conditions specified

in this chapter.

4.1 VISUAL INSPECTION

The SCAs shall be visually inspected using stereo zoom microscope of 10x

magnification. The inspection criteria for 40mm X 80mm cells nominal

dimension shall be provided by vendor and shall be mutually agreed upon as

mentioned in 2.10. The SCAs shall also be inspected using EL

(electroluminescence) technique and vendor shall provide the acceptance /

rejection criteria.

4.2 DIMENSIONS

The overall dimensions of the cell, the dimensions of the cover glass, its

position, interconnect and its position shall be measured with optical

templates or in a profile projector for conformance to the drawings.

4.3 SCA MASS Weighing the samples with an accuracy of within ± 1.0%, and dividing by the



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number of samples shall determine the average SCA mass.

4.4 ELECTRICAL PERFORMANCE The electrical performance of the SCAs shall be measured under 1 AM0

(1367 W/m2, WMO spectrum) illumination simulated by a class A sun

simulator, whose spectral response over the wavelength band of interest

closely matches that of the sun at 1AU from the sun in all the three

wavelength bands. The sun simulator intensity shall be set to match the Isc

and Voc at 28°C, using a set of secondary standards traceable to a balloon

flown primary standard (or any Govt. / non Govt. organization with history of

carrying out such balloon flight experiments. Vendor shall ensure that the

secondary standards are evaluated under class A solar simulator whose

spectral composition is close to WMO e.g. ESA/ESTEC) of the type

identical to the SCA being measured.

After setting the intensity and temperature, four reference SCAs of the type

under measurement shall be evaluated. The set-up shall be considered ready

for electrical evaluation of SCAs/ solar cells, if the Isc and IT of the reference

SCAs match within 1% of their standard value and the Voc matches within

1°C in temperature setting. Otherwise, the exercise shall be repeated after

adjusting the sun simulator intensity again. Suitable load and data acquisition

units shall be used for evaluating the SCAs/ solar cells.



REMARKS IF ANY

4.5 TEMPERATURE COEFFICIENTS The open circuit voltage, short circuit current, maximum power, the current

and voltage at the maximum power point, the fill factor and the efficiency shall

be measured between +28°C & +100°C and between +28°C & -50°C to

determine their first order temperature coefficients. Measurement shall be

made at 5 different temperatures in each of the two ranges.

4.6 WELDED CONTACT INTEGRITY The welding procedure adopted shall not degrade the output current of the

SCA including the diode. Series interconnects welded to the front contact of

the bare cell and the bypass diode and rear contact of the SCA including the

diode shall be tested, by pulling the interconnect tabs both in 0°and 45°. The

cell, diode or SCA shall be clamped to Unitek micro-pull tester or equivalent

such that the restraining force is applied on at least 40% of the cell/SCA area

and pulled at a speed not exceeding 40 mm/min. Minimum acceptable pull

strength per tab is 300 gram force and 150 gram force when pulled at @0°

and 45° respectively.

4.7 CONTACT UNIFORMITY The contact thickness uniformity for each fabrication lot shall be within

specified limits as defined in PID. Front and rear contact thickness shall be

measured using a Beta scope or equivalent. Measurement shall be carried



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out for each evaporation batch (metallization lot).

4.8 THERMAL CYCLING TEST

The SCAs/cells/diode shall be subjected to the following tests:

• Prior to thermal cycling, samples shall be subjected to a high

temperature soak at +150°C in an inert atmosphere for one hour.

• 50 thermal cycles –100°C to +150°C in vacuum, 30°C/minute,

maximum average temperature rate, no dwell is required.

• 2025 thermal cycles from –175°C to +130°C in an inert atmosphere

with 30°C/minute, maximum average temperature rate, no dwell

is required.

During the post thermal cycling electrical evaluation as per 4.4, the power

degradation due to the test shall be within 2%. This and weld strength

specifications shall be met on every SCA/cell/diode. Vendor shall specify the

acceptance criteria for the bypass diodes.

4.9 HUMIDITY

The SCAs shall be stored for 96 hours in a chamber at a temperature not less

than 65°C and relative humidity 95±5% at ambient pressure. Subsequently

the cells shall be dried for 2hrs at 80°C. Following the exposure the SCA

electrical output measured as per 4.4 shall not degrade more than 2%. It

shall also meet the requirements of tape peel test as per para 4.12.1



REMARKS IF ANY

4.10 IRRADIATION

4.10.1 PARTICLE IRRADIATION

Electrical evaluation of the radiation test samples before and after irradiation

shall be carried out by standard third party lab like JPL or SPASOLAB.

Test Condition:

Measure I-V data of the solar cells at +28°C before and after proton radiation.

Requirements:

• Establish normalized radiation degradation curves for Voc, Isc, Vmp, Imp,

and Pmp, including nominal and 90% confidence values.

• Subsequently the cells shall be subjected to Photon Irradiation Test as

in 4.10.3.

• Spectral Response (SR), External quantum efficiency (EQE), Internal

quantum efficiency (IQE), Temperature Co-efficient and Radiometric

properties to be measured before and after radiation of the samples.

Data to be provided:

• Remaining factor of all the parameters for each fluence.

(i.e. Ratio of EOL and BOL efficiencies for each fluence level)

• Establish EOL Eff. vs. Blue/Red ratio curve for each fluence.

• Each new reactor shall be validated at one energy/fluence, and

The vendor shall also provide the following data related to the cells used for

this test (i.e. Electron irradiation & Proton irradiation) along with the



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corresponding population averages.

• Blue/Red Ratio

• BOL Efficiency

• Voc

4.10.1.1 ELECTRON & PROTON IRRADIATION

Vendor shall provide the results of electron and proton irradiation testing of

the proposed solar cell for the following energies and fluences (typical).

Vendor shall also include in the price bid as option, the pricing for carrying out

these tests.

Electron and Proton Irradiation Test on the cells shall be carried out as

follows:

For each irradiation level a minimum of 12 cells shall be taken. These cells

shall be selected such that, they are from 3 different current classes namely

maximum, average and minimum and from 2 evaporation lots and from a

minimum of 2 MOCVD reactors in case more than one reactor is used for

production of deliverable lot. Electron and proton uniformity shall be

maintained at ±10% and temperature maintained at 20°C±10°C during

irradiation. The test shall be performed in accordance with JPL standard

procedures as published in JPL Publication 92-09 at a standard facility, which

has a heritage of being used for space quality solar cell irradiation. If any,

alternative standards established by other space agencies are used details

shall be provided. Subsequent to the electron irradiation, the cells shall be



REMARKS IF ANY

subjected to 8Hrs photon irradiation as in 4.10.3.

The vendor shall furnish the degradation factors for power, current and

voltage at the fluence levels defined earlier in addition to the omni directional

electron relative damage co-efficient (RDC) as function of electron energy

and shielding thickness.

SR, EQE, IQE, temperature coefficients and radiometric properties should

also be measured before and after the test.

The energy and fluence table for Electron irradiation test is given below:

Samples

Energy (MeV)

Fluence per cm2

12 0.6 2x1013

2x1014

1x1015

2x1015

12 1 3x1013

1x1014

5x1014

1x1015

12 12 1x1013

1x1013

5x1013

1x1014



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The energy and fluence table for Protron irradiation test is given below:

SAMPLES ENERGY FLUENCE PER CM2

1E10 3E10 1E11 3E11 1E12 3E12 12 20 KeV X X X X X X 12 50 KeV X X X X X X 12 100KeV X X X X X X 12 300KeV X X X X X X 12 1MeV X X X X X X 12 3MeV X X X X X X 12 10MeV X X X X X X

4.10.2 PHOTON IRRADIATION

The SCA samples shall be subjected for 48 hrs of standard AM0 spectrum

exposure under a suitable solar simulator. The cells shall not show

degradation more than 2% from the original current at load point voltage as a

result of photon exposure.



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4.10.3 PHOTON IRRADIATION (SHORT DURATION)

The SCA samples shall be subjected for 8 hrs of standard AM0 spectrum

exposure under a suitable solar simulator. The cells shall not show

degradation more than 2% from the original current at load point voltage as a

result of photon exposure.

4.10.4 UV IRRADIATION (FOR SCA ONLY)

SCAs shall be subjected to a UV equivalent of 1000 sun hours of WMO

standard AM0 spectrum, under minimum of 10-5 Torr vacuum, at temperature

≤ 40°C. Within 48 hours after the completion of the irradiation, the samples

should be electrically evaluated, as per 2.4 and the average short circuit

current degradation shall not exceed 2%.

4.11 RADIOMETRIC PROPERTIES

4.11.1 SOLAR ABSORPTANCE

The spectral reflectance of electromagnetic energy shall be measured from

0.28 to2.5 micrometers with Edwards’s type integrating sphere equipment or

equivalent. The test data shall be integrated over the solar irradiance and the

integral subtracted from unity to yield the solar absorptance.

4.11.2 HEMISPHERICAL EMITTANCE

Measure spectral reflectance in the wavelength ranges from 2.0 to 26

micrometers and integrate over 300K planckian radiator functions. The

measured data should comply with the requirement of 2.5.



REMARKS IF ANY

4.12 CONTACT AND COATING ADHERENCE

The cells shall be exposed to a relative humidity of 95 ± 5% at a temperature

of 95°C for a period of 2 hours. Before and after this test, tape peel test as

described below shall be conducted on the cell front side.

4.12.1 TAPE PEEL TEST

Scotch brand Magic transparent tape No.810/ 600 with an adhesion to steel

value equal to or exceeding 33 grams per cm width shall be placed on the

surface to be tested. The tape shall be rubbed well ensuring that it adheres

firmly to the surface and stripped at 90° to the surface. Not more than 1% of

rear contact, 5% of the AR coating shall be removed by the tape and there

shall be no peeling of top contact pads.

4.13 INTERCONNECT FATIGUE

The interconnect loop in the form to be used in SCAs shall be subjected to

the mechanical flex test to establish the interconnect fatigue life. The

configuration of the flex test and the deflection shall be jointly worked out by

the vendor and ISRO after studying the proposed interconnect drawing.

4.14 SPECTRAL RESPONSE

The spectral response (SR) of the SCAs shall be measured by comparison of

the short circuit current of the test cell with the output of a spectral standard

of known relative spectral response under monochromatic irradiation.

• At various discrete wavelength intervals between 0.3 and 2



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micrometer using narrow band interference filters or

• By means of a high intensity monochromatic light, for continuous

recording between 0.3 and 2 micrometer wavelengths. The

minimum spectral irradiance shall be 100 microwatts/cm2.

EQE and IQE of SCAs shall also be measured similarly following the

standard protocol.

4.15 REVERSE BIAS SCREENING

Reverse bias screening test for the cell shall be spelt out by the vendor to

assess that the solar cell shall not degrade due to reverse bias applied on the

cell. The vendor shall specify test specification, test methodology and

allowable degradation criteria. Samples failed once shall not be subjected for

retest. The supplier shall also provide the yield of the reverse bias screening

test. The screen shall be performed on the 100% samples selected for ISRO.

4.16 ANGLE OF INCIDENCE TEST

SCAs should be taken from random current classes and should be subjected

to angle of incidence tests. The I-V characteristics of the SCAs shall be

measured at 0°, 20°, 40°, 60° and 80°.

4.17 SHADOW TOLERANCE TEST

The mean IT of SCAs shall not decrease by > 2 % and any individual SCA IT

shall not degrade by more than 3%, when subjected to partial shadowing.

This condition shall be simulated by reverse biasing the test samples to 1.22



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Isc at 90 + 5°C/ -0°C for 30 minutes in dark.

4.18 BY PASS DIODE / SCA LIFE TEST

Qualification test SCAs shall be subjected to 3000 Reverse Bias Cycles

from 1.1 Isc for 30 Secs to zero mA for 30 sec in a Thermo Vacuum Chamber

(



FROM THE VENDOR

REMARKS IF ANY

5 PACKAGING, DELIVERY AND SCHEDULES 5.1 PACKAGING

The SCAs and allied materials shall be packed in containers of design

approved by ISRO with adequate protection from damage during transport

and handling. Special care should be given for interconnects. The

containers shall be heat sealed in an airtight water proof barrier as per MIL-B-

22191, together with sufficient bagged, activated dry desiccant as per MIL-D-

3464 and tarnish inhibitor to prevent contamination to assure compliance as

per chapter 2.0. A card type humidity indicator scaled 10 to 80% of relative

humidity shall be placed in each sealed bag. Any packaging or desiccating

material used shall not affect the electrical and mechanical properties of the

SCAs and allied materials. The vendor shall submit a packaging and storage

plan for ISRO approval prior to the first lot shipment.

5.2 TRANSPORTATION AND PACKAGING ACCEPTANCE

Inspection of the packaging for shipment shall be as per 5.1 of this

document. Contents of the damaged containers will be rejected. In case, the

humidity indicator accompanying the SCAs indicates a humidity level greater

than 40%, the defective container shall be rejected. Any SCA, which does not

meet one or more of the acceptance test requirements, shall be rejected.

5.3 DELIVERABLE DOCUMENTS

The following documents shall be submitted in the form of permanent files at



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the appropriate time. All documentation shall be in English.

The quotation shall contain the following.

• Technical Data on the proposed SCA as per 5.3.1

• Export Control Document requirements of the proposed SCAs.

• Quotation for

o the proposed SCA

o Allied Material as per of 5.5 (Sl. No. 3 to 10)

o Lot Acceptance Test (LAT) as per 3.1.3

o Type Approval Test (TAT) giving group wise breakup

o Life test Coupon Fabrication as per 3.1.2

o Life test Coupon testing as per 3.1.2

o ESD test on Coupon As per 3.1.2

• For preparation of the quotation, commercial guidelines shall be

followed.

5.3.1 DATA/ DOCUMENTS REQUIREDALONG WITH THE PROPOSAL

The technical proposal shall include but not limited to the following.

1. A compliance matrix for this proposal in a spreadsheet.

2. Description of the hardware offered including necessary drawing

and images.

3. Manufacturing & Qualification / flight heritage.

4. Comparison of the qualification status of the hardware offered



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against standard international specifications.

5. I-V characteristics of a typical SCA with lot average efficiency

specified in the form of a table and plot at 28°C to 60°C and

110°C under standard AM0 spectrum before and after

irradiation with 1x1014 1 MeV electrons/cm2 and 5 x1014 1 MeV

electrons/cm2.

6. Bending radius of the SCA at maximum curvature.

7. Quality manual

8. Cross sectional diagram of the SCA with thickness of the

different layers.

9. Product assurance plan including fabrication and process control

aspects reliability analysis. Non-conformance control and

approval of configuration control and traceability.

10. Maximum Panel size and test levels of CFRP qualification panel

tested by vendor for qualifying the triple junction SCAs.

11. Qualification test reports on the SCA and allied materials

including the bypass diode.

12. Documentation of bare cells, semi-bare cells, and cover glass.

13. Absolute typical spectral response of the proposed solar cell.

14. Remaining factor of the parameters Isc, Imp, Vmp, Voc and Pmp

for each of the fluence levels 3x1013, 1 x 1014, 5 x 1014, and 1 x



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1015 of 1MeV electrons /cm2. (i.e. Ratio of EOL and BOL

efficiencies for each fluence level).

15. Details of solar simulator used to evaluate the triple junction

solar cell.

16. Export Control Document requirements of the proposed SCA.

5.3.2 ALONG WITH PID

All documentation shall be submitted as three hard copies and one copy in

electronic form. The PID as per 3.1.1.1 shall be submitted on receipt of the

contract document. The PID shall include all the details specified in Chapter

2.0 of this document. The PID shall be accompanied by the following

documentation.

1. The omni directional relative damage coefficients of the triple

junction solar cells as a function of the shielding thickness for the

following electron and proton energy ranges. Electron 40 KeV to

7 MeV. Proton 100 KeV to 200 MeV.

2. Blue/ red ratio of the proposed solar cell at the beginning of life

and after experiencing 5E14 and 1E15 equivalent 1MeV electron

fluence.

3. List of materials used, with their quality levels derating criteria

and failure rates.

4. Cell diffusion capacitance as a function of voltage and

temperature (28°C, 65°C and 110°C at BOL and after irradiation



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at 1 x 1015 and 5x10141MeV electrons).

5. Dimensional drawings of all hardware with tolerances.

6. Spectrum of the sun simulators used by the vendor in the form of

a table and plot.

7. Calibration procedures for the secondary standards.

8. Thermal conductivity of the solar cell.

9. Thermal coefficient of expansion of the solar cell.

10. Packing and storage conditions for the SCAs.

5.3.3 ALONG WITH EACH LOT OF SCA

The following documentation shall accompany every deliverable lot. All

documentation is to be submitted as three hard copies and one copy in

electronic form.

1. The entire acceptance test records and results shall accompany

each shipment of SCA.

2. The vendor shall provide measured performance data (Voc, Vmp,

Isc, Imp, IT, I at 1.2V, I at 2.55V and measured Vr during reverse

bias screening)) for all delivered SCAs in electronic format.

3. A certificate from the vendor that the lot has successfully passed

the acceptance tests shall accompany each deliverable lot.

4. Standard SCAs (set of four) I-V characteristics measured as per

specification and spectral response in the form of a table and



REMARKS IF ANY

plots (with digital data in excel).

5. Waivers and non-conformances during cell/ SCA manufacture by

vendor or Sub-contractor and dispositions thereof.

6. Quality control results in the form of Statistical Process Control

(SPC) Charts for the various processes including SCA making.

5.4 HARDWARE DELIVERABLES ISRO decides the no of SCA’s to be procured as per the requirement. Vendor has to

quote from 10000 to 100000 SCAs in slabs of 10000 SCA’s. The no. of shipments be

mutually agreed between vendor and ISRO, First shipment to last shipment time

period is 24 months.

Sl. No ITEM Quantity

1 SCAs Number of allied materials required for 10000

SCAs is as follows

2 Secondary Standards Set (Each set consisting of 3 sub cells and 1 full cell)

3 sets

3 Positive end terminations (consists of 1busbar and interconnects equal to the number of

2000 sets



REMARKS IF ANY

interconnects in the SCA)

4 Negative end terminations

2000

5 Interconnects For Pull Test (equal to the no. of interconnects in the SCA)

2000 sets

6 Repair Interconnects (equal to the no. of interconnects in the SCA)

2000 sets

7 Germanium Substrates (4 inch and 6 inch)

50 each

8 Smaller size cells area around 10 cm2

1000


ANNEXURE A – ENVIRONMENTAL REQUIREMENTS

The SCA and the allied materials shall be designed to meet the performance

requirements before, during and after exposure to the environments specified

below. The environments experienced during fabrication, transportation and

storage of the SCAs and allied materials shall be significantly less severe

than them.

A1. PRE-DEPLOYMENT A. On Ground : Relative humidity (Rh) of 70% max at 760 ± 25 mm of

Hg barometric pressure over 23± 5°C temperature range

B. In Space : -180°C to +125 °C (10 cycles).

C Acoustic noise : 146 dB overall for 2 minutes.

D. Sine vibration : 30g peak, 20-50 Hz; 10g peak, 50-100 Hz

E. Shock : 113g @ 200 Hz increasing to 450g @ 400 Hz;

450g max. @ 400 to 500 Hz;

600g max.@ 1600 to 4000 Hz.

A2. DURING DEPLOYMENT A. Barometric pressure : < 1.0 x 10-10 Torr

B. Temperature : -180°C to +125°C

A3. POST DEPLOYMENTS


A. The SCA shall be designed and manufactured to withstand 15 years of

GEO life (2025 thermal cycles between +130°C to -165°C and 4500

thermal cycles between +130°C and -100°C)

B. Barometric Pressure less than 1 x 10-10 Torr.

A4. RADIATION A4.1. GEO ORBIT

A4.1.1. ELECTRON RADIATION The minimum-trapped electron environment in synchronous equatorial

orbit, which the SCAs shall account, for, based on the AE-8 model is presented in Table 1.

TABLE 1: ELECTRON FLUENCE AE-8¸ MAX MODEL Energy Level

(> MeV) Flux: e/cm2/sec

0.04 4.6 x 107

0.1 4.2 x 107

0.5 4.0 x 106

1.0 4.9 x 105

1.5 1.2 x 105

2.0 4.1 x 104

2.5 1.1 x 104

4.0 4.9 x 103

4.5 1.6 x 103

4.0 4.5 x 102

4.5 1.2 x 102


5.0 4.5 x 101

A4.1.2. PROTON RADIATION

Table 2(A) describes the low energy proton environment, which the design

shall account for, for time averaged integral flux spectrum. The estimate for

the high-energy proton spectrum, which represents the solar flare Content of

the 20th cycle, is shown in table 2(B)

TABLE 2A: PROTON FLUX - LOW ENERGY

Energy Level

(> MeV) Flux: p/cm2/sec

0.01 2.74 x 107

0.03 2.0 x 107

0.05 1.51 x 107

0.07 1.12 x 107

0.10 7.21 x 106

0.20 1.64 x 106

0.30 6.54 x 105

0.40 2.61 x 105

0.50 1.04 x 105

0.60 4.17 x 104

0.70 1.65 x 104

0.80 6.52 x 103

0.90 2.58 x 102

1.00 1.02 x 102


1.25 1.00 x 102

1.50 9.85 x 100

TABLE 2B: PROTON FLUENCE - SOLAR FLARE Energy Level

(MeV) Fluence : p/cm2/cycle

1 1.2 x 1011

4 5.5 x 1010

10 4.28 x 1010

30 9.78 x 109

60 2.95 x 109

100 6.69 x 108

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