RoHS Compliant Lead Free PCB Fabrication

Lead FreeCost Reduction

–High Temp Laminates–Final Finishes

2

Direct Cost Drivers

–Increased Scrap Rate• De-lamination• Solderability

–Pre-Baking–Storage / Handling

Indirect Cost Drivers

3

Section 1

Pb-free Assembly

Capable Laminate4

5

IPC 4101/99 /124 from

Isola Group/ Insulectro

–Common Callouts• IS410 / 370HR• FR4• RoHS Compliant• 180ºC Tg• 340ºC Td• IPC 4101/126 or /129

6

Current StateAudience Poll……

Polling Question

7

• Effect of Common Callouts1. Locked in to laminate by brand name2. Typically Phenolic materials

• Moisture absorption up to .45% on 0.028” core• Less mechanical strength (interlaminate adhesion)• More prone to de-lamination during assembly• Prone to pad cratering on BGA applications

8

Current State (cont.)Audience Poll……

3. Non-Pb Free capable material• FR4 is not capable• RoHS Compliant can include standard FR4• 180Tg does not guarantee adequate Td

9

Current State (cont.)

Proposed Solution

• Mid-Grade Pb-free capable laminates– IPC 4101 / 99 (filled) or /124 (unfilled)

• 150 Tg min.• 325 Td min.

10

– 15-20% Cost Savings on Raw Materials– Lower Moisture Absorption (0.10%-

0.25%)– Higher interlaminate adhesion

• Peel strength• T-288 >10 minutes

– Higher Copper to Laminate peel strength

11

Benefits

(using Isola IS400 as example)

12

Results

Test Group ResultsDecomposition TemperatureTest 1 of 2

Method of Determination: TGA

Decomposition Temperature: 331 C

Ramp Rate: 10 C/ min

Test 2 of 2

Method of Determination: TGA

Decomposition Temperature: 334 C

Ramp Rate: 10 C/ min

13

Results

TGA

14

Test Group ResultsDelta TGTest 1 of 1

Method of Determination: DSC

TG Scan 1: 150 C

TG Scan 2: 154 C

Delta Tg: 4 C

Ramp Rate: 20 C/min

Analysis Method: Half Height

15

Results

DSC – (A)

16

DSC – (B)

17

Test Group Results

Time to Decomposition at TemperatureTest 1 of 2

Method of Determination: TMA

Time to Decomposition: 35.9 minutes

Isothermal Temperature: 260 C

Test 2 of 2

Method of Determination: TMA

Time to Decomposition: 10.4 minutes

Isothermal Temperature: 288 C

18

Results

T-260

19

T-288

20

Test Group Results

Weight Loss % by TGA

Test 1 of 1

Percent Weight Loss: 0.2%

Start Temperature: 0º C

Stop Temperature: 0º C

Comments: Moisture Method

% Weight Loss = 0.1717%

21

Results

Moisture Absorption (A)

22

Test Group Results

Peel Strength

Condition: Condition A

Peel Strength Side 1: 11.73 lbs/in

Peel Strength Side 2: 10.95 lbs/in

23

Results

Pb-free Assembly Temperature– One board, 3 array– One 4.25 x 9.5L”, Two 4.75 x 9.5L”– Thickness + 0.063– TGA moisture = 0.2534%– 260° Peak Temperature

24

6-X Reflow

25

Conditioning As Received

Board # 14753-1Material IS400

Thickness (mil) 0.063

Conveyor Speed (cm/min) 48

Peak Mean Temp (?C) 259.8

TC Temp Range 3.4

Rising time between 150C - 200C 66.67 (sec)

Time above 217 101

Time above 255 19.69

Passes to Fail 6x-Pass

26

Results

27

Coming Soon – FR406HR

Section 2Pb-FreeHASL

Audience Poll28

DefinitionSN100CL-this is a SnCu alloy stabilized with Ni,

composed of:• 99.3% Tin• <0.7% Copper• 0.05% Nickel• 60 ppm Germanium

29

Industry Misconceptions

• Predictions of HASL’s Demise• Solderability Issues• Short Duration of Usage

30

Benefits1. Lower Copper Erosion on PCB surface and vias2. Quick Process3. Long Shelf Life4. Cost

(< 1/14 ENIG)

5. Forgivinga.) Humidityb.) Handlingc.) Temperature

6. Solder Joint Strength

31

32

( using Florida CirTech HALTexample )Highly Accelerated Life Test

Results

33

Benefits – Solder Joint StrengthHALT Test Results

34

Benefits –HALT Test Results

35

Benefits

36

Benefits

Lead-Free HASL, with all different solderpastes pooled together, required the most energy (G-force + thermo-cycling) to break the solder joints.

Since this test takes out the failure effect of the components, we can conclude that lead-free HASL solderjoints outperform all other surface finishes, including SnPb HASL.

Our thanks go to Tim Murphy of Thomson Lab Services and Florida CirTech for the report abstract.

For a full report, please contact James Kelch @ [email protected]

37

HALT Test Results

Drawbacks• Not Planar

• Not Ideal for extremely fine pitch applications

• Past Solderability Issues• HASL and Flow: A Lead-Free Alternative

addresses this in the February ’08 issue of

Request a copy from James Kelch or visit the

Lead Free Resource Center on our website.

38

Drawbacks, cont.• Thermal Cycle

– SN100CL requires a Thermal Cycle in addition to Thermal Cycles in Assembly

• No Set Industry Standards– Neither the IPC nor Nihon Superior had developed a

Thickness Acceptability Criteria when SN100CL was introduced Audience Poll

39

40

Polling Question

Trigger Event Solderability Issue at Customer

41

No Standard - Solutions

42

No Standard - Solutions• Goal

– Establish a Set Criteria

43

Thickness Criteria• Generic Thickness Requirement

• Not proper to have only one– Smaller Pads receive thicker solder deposition

• Solution• Minimum Alloy Thickness should be

segregated by Ranges of Pad Size

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Pad Size (mils) Min. Thickness

126 x 131 50 uin

29 x 83 80 uin

17 x 36 100 uin

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Implementation• Alloy Control

• Lower copper content of alloy increases solderability• Standard Drossing of solder pot is not enough to

keep copper content below 0.90%• Recommend a 1/4 - 1/3 solder pot dump once weekly

measurement reaches 0.90%

• Specific Design Set-Up– Each Design may require its own specific set-up– Adjustments

• Air Knife Pressure• Retract Speed• Dwell Time

46

Implementation

• In effect, since the operating window is smaller than with SnPB,…….

CONTROL The PROCESS!!!

47

Implementation

SN100CL Study Conclusion

• No Solderability Issues at any customer– Fab Notes

• Fab notes can specify the use of these coupons or range of solder thickness standards

– Forcing your supplier to meet these specs will give you:

»Control over the Process48

Conclusion• By implementing one or both of these

proposed solutions, you can:– Save up to 30% of your bare board cost– Increase performance of your products– Standardize your fab notes to remove risk of

non-performing products– Improve your supply base

49

• To view the archived version of this presentation, please email [email protected]

• To sign up for our upcoming Lead Free Newsletter, please email [email protected]

50

Thank You!

Saturn Electronics Corporation would like to thank our presenters:

Ø Dave Coppens / IsolaØ Terry Staskowicz / InsulectroØ Glenn Sikorcin / Florida CirTech

*Don’t forget to visit the Lead Free Resource Center51