Yield Improvement Project on Catalytic Bead Sensors

Dr. Rupendra M. Anklekar

November 20, 2012

Situation/Problem Statement: Thermo Fisher Scientific acquired Gas Tech Inc. in 1991

with its operations in California Moved to Franklin, MA in 2002 (consolidation) A small team trained in California before the move None of the process engineers or key people moved Erosion of the sensor manufacturing process resulting

in low yields from ~60% to 20-40% and occasionally 0-10%

Sensor business yielded highest EBITA earnings (70%) Business decision to discontinue the sensor and gas

detection products if the yields could not be improved

Reasons for Sensor Yield Loss

Sensor Technologies: Catalytic Bead (Combustible gas)

Electro-chemical (Toxic gas & Oxygen)

Thermal Conductivity (TC)

Infrared (IR)

Semiconductor (SC)

Photo-Ionization Detector (PID)

Flame Ionization Detector (FID)

Paper/Tape

Sensors for Gas Detection

Principle of catalytic bead sensor Catalytic bead sensors

Low Power – 2.0 V Medium Power – 2.2 V High Power – 6.0 V

Catalytic bead sensor comparison Voltage/current/power Process equipment Platinum wire Chemicals used Chemicals application Application – Portable or Fixed System

6.0 V sensor Yield improvement - Focus

Catalytic Bead Sensors

Consists of a very small sensing element called a ‘bead’◦ Active element (with catalyst) ◦ Reference element (no catalyst)

Made of an electrically heated platinum wire coil which acts as a temperature thermometer ◦ Active: Coated with a ceramic (Alumina) and then with a catalyst

(Palladium/Platinum) ◦ Reference: Coated with a ceramic (Alumina) and then with a glass coating &

deactivator

When a combustible gas/air mixture present◦ Active: Heat is evolved due to combustion which increases the temperature and in-

turn the resistance of the bead (TCR)◦ Reference: Since there is no catalyst there is no combustion and no resistance

change ◦ The change in electrical resistance of the active element with respect to the

reference element is measured using a standard Wheatstone bridge circuit◦ This change in resistance is directly correlated to the combustible gas concentration

and displayed on a meter or some similar indicating device

Nearly all modern, low-cost, combustible gas detection sensors are electro-catalytic bead type

Principle of Catalytic Bead Sensor

Property 2.0 Volt (Low) 2.2 Volt (Medium) 6.0 Volt (High)

Voltage 2.0 V 2.2 V 6.0 V

Current 91 mA 142 mA 242 mA

Power 0.18 W 0.31 W 1.45 W

Platinum Wire Bare Bare Alumina Coated

PlatinumAlumina

0.6 mils/15 µm Φ 1.2 mils/30 µm Φ 2.0 mils/50 µm Φ3.8-4.0 mils/95-100 µm Φ

Winder/Bonder Semi-Automatic Manual Manual

Catalyst Palladium + Platinum

Platinum Platinum

Active BeadReference Bead

40-46 Layers10-12 Layers

20-28 Layers20-28 Layers

18-26 Layers18-26 Layers

Chemicals Application

Alumina DispersionPalladium ChloridePlatinum Chloride

Ceramic Former (30%)Glass Former SolutionPlatinized Alumina Deactivator Solution

Ceramic Former (70%)Glass Former Solution

Platinum Chloride SolutionDeactivator Solution

Application Portables/Genesis Portables/Innova Fixed Systems

Catalytic Bead Sensor Comparison

Catalytic Bead Sensors & Products

GenesisInnova

Catalytic Bead Sensors

Explosion-proof Housing Polyester Housing High Temperature Housing

Fixed Systems

Portable Systems

Sensor Assembly/Test ProcessPt Coil

Weld to 2-Pin Header

Coating of Acrylic Resin in Toluene

Chemicals Application Insulation Firing

Batting/Wrap Support

Chemicals Curing

Element Matching

Weld to 3-Pin Header

Assembly in Flame Arrestor

Pre-Assembly Testing Epoxy Gluing/Curing

Final Assembly in Housing Cementing/Curing

Final Testing

Zero Drift Testing

6.0 V, 2-3 coatings20-30 min. drying

6.0 V, slow voltage ramping and soak for 1 hour

4 days

Maximum 7 boards each of Active and Reference elements and each board holding 14 elements

1 day

1 day

7-10 days

Electrical Offset – 0 +/-20 mV, IP – 5.2-5.65 V Response – 85-140 mV, Noise – </= 1 mV

Identified critical process steps for yield loss Root Cause Analysis Failure Mode Effects Analysis (FMEA) Design and Analysis of Experiments (DOE)

Developed new innovative electrical tests Used correct SPC methodology Put critical in-process specifications

Resistance, current drawn, voltage drop Coil welded to header, after chemicals application and curing

Improved design of processes /components Chemicals application Wrap support Flame arrestor

Simplified processes Removed unwanted/non-value added process steps

6.0 V Sensor Yield Improvements

Upgraded Sensor Lab equipment Improved processes

In-process controls/control plans Developed fixtures/handling aids/visual aids Camera display systems for chemicals application Assembly and test procedures Improved proper handling and packaging of sensors for shipping Identified yield loss due to sensor poisoning by silicones and

specific chemicals/solvents present in the plant Improved testing of sensors

Improved test fixtures, gas flow control and cleanliness for accuracy

Developed zero drift testing for sensor stability Hands-on training

Assembly Testing Applications

6.0 V Sensor Yield Improvements

Short circuit Overlapping coil (2.0 V & 2.2 V) Too compact coil and touching after adding chemicals Loss of insulation, cracking or breakage (6.0 V) High porosity and shorting by catalyst Wrap support touching the flame arrestor

Open circuit Broken coil Coil broken at weld joint

Catalytic bead characterization defects Too small/too large bead size Improper or no glass coverage Incorrect amount of chemicals Incorrect sequence of chemicals Improper curing of chemicals (under curing/over curing)

High electrical offset Improper welding

Unstable/drifting Test results outside specifications

Sensor Failure Mode Effects Analysis

Example: Purity of chemicals

High purity (AR grade) Certified vendors

Correct preparation of chemicals Correct weights/volumes (calibrated analytical balance,

pipettes) Correct sequence of adding chemicals (procedures, Training) No cross-contamination of chemicals (Training)

Chemicals application Correct amounts/volumes (calibrated Matrix dispenser) Correct sequence (automatic dispensing equipment,

procedures, Training) No cross-contamination of chemicals (Training)

Chemicals Application

6.0 V Sensor Process ImprovementsPt Coil

Weld to 2-Pin Header

Coating of Acrylic Resin in Toluene

Chemicals Application Insulation Firing

Batting/Wrap Support

Chemicals Curing

Element Matching

Weld to 3-Pin Header

Assembly in Flame Arrestor

Pre-Assembly Testing Epoxy Gluing/Curing

Final Assembly in Housing Cementing/Curing

Final Testing

Zero Drift Testing

Results/Conclusions: Improved the yields from as low as 20-40% to

80-95% for different sensors Improved the productivity of the Sensor Lab by

~120% for manufacturing the same volume of sensors by reducing the total staff from 12 to 5

Reduced the MRB scrap for sensors and gas detection products from >$110,000 to <$10,000 per year

Provided engineering support for $10-12 million of Industrial Hygiene business per year

Sensor Yield Improvements

Fostered team work and team building Rupendra Anklekar – Senior Project Manager/Consultant / Sensor/

Detector Scientist/Engineer / Senior Process Engineer Jeff Maybruck/Larry Fahey – Manufacturing Engineering Manager Mike Loncar - Production Manager Jayne Clarke - IH Value Stream Leader Van Krikorian/Mike Molinario - Supplier/Product Quality Engineer Brian Faulkner/Todd Muccini – Supply Chain/Materials Manager Aurora Norton/Jill Ligor – Buyer Diane Antosca – Planner Denise Whalen/Judith Lavelle - Production Supervisor Donna Lavelle/Clay Fournier/Maria Don Bourcier - Cell Leads Amy/Jane - Test Technicians Ying, Sophie, Air, Von, Noy, Sai, Seepan, Nog, Christe + 4 part-time

operators - Assembly & Testing

Cross-Functional Team Members

Open for discussion

Questions