using mlo’s to build vertical contact space …mlo aligned and placed on pcb 5. reflow the...

25
Presentation to Southwest Test Workshop 2002 Using MLOs to Build Vertical Technology Space Transformers Bill Fulton and Bill Pardee Wentworth Laboratories

Upload: others

Post on 13-Aug-2020

3 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

Presentation toSouthwest Test Workshop 2002

Using MLOs to Build Vertical Technology Space Transformers

Bill Fulton and Bill PardeeWentworth

Laboratories

Page 2: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 2

Overview1. Terminology2. Benefits of MLOs vs MLCs3. MLO Basics4. MLO Variables5. MLO Manufacturing Challenges6. Processing MLO for Use as Space Transformer7. Test Verification 8. Reliability9. Performance Data10. Conclusions

Page 3: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 3

Terminology/Acronyms 1. ST – Space Transformer2. MLO – Multi Layered Organic3. MLC – Multi Layered Ceramic4. BGA – Ball Grid Array5. FR4 – Fiber Glass6. ePTFE – Expanded Polyetraflouroethylene7. CRES – Contact Resistance8. C4 – Controlled-Collapse Chip Connection 9. CTE – Coefficient of Thermal Expansion10. OSP – Organic Solderability Perservative

Page 4: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 4

Benefits of MLO vs MLC

1. Design/Manufacturing Time

i. MLO – customer supplied at time of order

ii. MLC – lead time of up to three months

Page 5: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 5

Benefits of MLO vs MLC2. Cost

i. Typical MLO package – $15 - $50ii. Custom designed MLC – NRE $10,000 -

$15,000, $5,000 – $10,000 each (10 piece minimum)

3. Tighter Pitches (BGA side)i. Minimum pitch MLC 1.0 mm (typical)ii. Minimum pitch MLO 0.6 mm (typical)

Page 6: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 6

MLO BasicsApplication “Flip Chip” Packaging for1. Microprocessors2. ASICs3. DSPs4. Memory –

Flash and DRAM

Page 7: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 7

MLO Basics1. Design: Determined by customer’s

packaging group2. Vendors

i. 3M (W.L. Gore)ii. IBMiii. Fujitsuiv. Ibidenv. Kyoceravi. NTK

Page 8: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 8

MLO Basics

3. Compositioni. FR4 – most commonly used fiberglass-type materialii. ePTFE – newer material

1. resin composite – uniform structure throughout2. better machinability with laser3. better CTE matching4. ideal for dense arrays, tighter pitch size – device

side

Page 9: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 9

Typical MLO Assembly

Underfill

MLOSolder paste and spheres

PCB

Page 10: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 10

MLO Variables

1. Thickness2. BGA Pitch3. Pad Composition4. Solder Mask Opening5. Metal Stiffener Rings6. C4 Pitch7. Flatness

Page 11: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 11

MLO Manufacturing ChallengesStructural integrity

Problem - BGA pattern voids under C4 areaSolution - Underfill on BGA side

BGA PitchProblem - Accommodate smaller pitch requirements

• 1.27 mm – past• 1.00 mm – today• 0.80 mm – soon• 0.60 mm – future Solution - Create custom fine pitch solder stencils

Page 12: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 12

MLO Manufacturing ChallengesPad Composition

Problem – OSP and solder on padsSolution – Remove and plate with nickel and gold

Solder Mask OpeningProblem – Solder mask opening too smallSolution – Remove solder mask (proprietary process)

Page 13: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 13

MLO Manufacturing ChallengesMetal Stiffener Ring

Problem – C4 pads recessed below stiffener Solution – Stepped Cobra® head

Stiffener

C4 pad

area

Step

Page 14: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 14

MLO Manufacturing ChallengesC4 Pitch

No issue with current fine pitch contact technology

FlatnessProblem – Warping of extra-thin MLOs Solution – Custom lap at assembly

Page 15: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 15

Processed C4 Pad

Solder mask

C4 pad

Page 16: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 16

MLO Processing

Unprocessed MLO –soldermask still on

pad area

Processed MLO –solder mask

cleared from PAD area

Page 17: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 17

MLO Processing Preparation1. Remove solder

2. Remove solder mask exposing pad3. Nickel and gold plate

Solder Solder Mask

Page 18: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 18

Post-Processing Inspection

1. Visually inspect C4 pads for damage2. Verify alignment of C4 pads within .0003”

in true position3. Measure flatness of C4 area – .0005”or

less4. Measure flatness on entire MLO – .0015”

or less5. Test for allowable leakage <5 nA @5VDC

Page 19: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 19

Bonding MLO on Probe CardBGA Attach1. Equipment:

i. Solder Stencil Printer –apply solder to BGA pads

ii. Programmable Reflow Oven

2. Fixturing: i. BGA Alignment

Placement Tool– align and place

MLO to PCB

Page 20: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 20

Bonding MLO on Probe CardBGA Attach Techniques1. Apply solder paste and solder spheres to

BGA pads2. Reflow solder 3. Apply solder paste to PCB4. MLO aligned and placed on PCB5. Reflow the assembly in programmable oven 6. Apply underfill to MLO7. Inspect

Page 21: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 21

Completed Space Transformer

Page 22: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 22

Verification of Probe Card

Final Assembly Test1. Leakage2. Bulk Planarity3. Overdrive leakage4. Alignment5. Full planarity & CRES

6. Wire Check7. Components

Page 23: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 23

Performance Data

Typical Pad Wear

1 million touchdowns

Initial condition

Page 24: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 24

Performance Data

MLO Lifetime Performance as Measured by Path Resistance and Planarity

0

0.5

1

1.5

2

0 200000 400000 600000 800000 1000000

Touchdowns

CRes ohms Planarity Values mil

Page 25: Using MLO’s to Build Vertical Contact Space …MLO aligned and placed on PCB 5. Reflow the assembly in programmable oven 6. Apply underfill to MLO 7. Inspect 6/10/02 Wentworth Laboratories,

6/10/02 Wentworth Laboratories, Inc. 25

ConclusionMLO/ST technology benefits:1. Fast turnaround as compared to custom-

designed MLC2. Lower cost probe card cost due to lower ST

costs3. Closer match to actual “real world” application

due to similarity of materials 4. Performance equal to more expensive MLCs5. Ideal, cost-effective solution for short-runs of

ASICs and other specialty devices