Lead Free Pcb RoHs Compliant Design, Fabrication, and Assembly Cost Reduction

Lead Free Cost ReductionLead Free Cost Reduction

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L d FLead FreeCost ReductionCost Reduction

Direct Cost DriversHi h T  L i t

Direct Cost Drivers–High Temp Laminates–Final FinishesFinal Finishes

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Indirect Cost DriversIncreased Scrap Rate

Indirect Cost Drivers–Increased Scrap Rate

• De-lamination• Solderability

–Pre‐BakingPre Baking–Storage / Handlingg g

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S ti  Section 1

b fPb‐free Assemblysse b y

Capable LaminateCapable Laminate5

IPC 4101/99 /124 IPC 4101/99 /124 from

Isola Group/ Insulectro

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Current State

C  C ll

Current StateAudience Poll……

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

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Current State ( )

• Effect of Common Callouts

Current State (cont.)Audience Poll……

Effect of Common Callouts1. Locked in to laminate by brand name2  Typically Phenolic materials2. Typically Phenolic materials

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

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• Have you experienced delamination during Lead Free Assembly?Assembly?

• Yes• No

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Poll ResultsPoll Results

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Current State ( )

3. Non‐Pb Free capable material

Current State (cont.)3. Non Pb Free capable material

• FR4 is not capable• RoHS Compliant can include standard FR4RoHS Compliant can include standard FR4• 180Tg does not guarantee adequate Td

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Proposed SolutionProposed Solution

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

 T   i• 150 Tg min.• 325 Td min.

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Benefits– 15‐20% Cost Savings on Raw Materials–Lower Moisture Absorption (0 10%‐Lower Moisture Absorption (0.10%0.25%)Higher interlaminate adhesion–Higher interlaminate adhesion

• Peel strength• T‐288 >10 minutes• T‐288 >10 minutes

–Higher Copper to Laminate peel strength

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ResultsResults

(using Isola IS400 as example)

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ResultsTest Group Results

ResultsDecomposition Temperature

Test 1 of 2 

Method of Determination: TGA

Decomposition Temperature: 331 C

Ramp Rate: 10 C/ min

Test 2 of 2est o

Method of Determination: TGA

Decomposition Temperature: 334 C

Ramp Rate: 10 C/ minRamp Rate: 10 C/ min

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TGATGA

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ResultsTest Group Results

ResultsTest Group Results

Delta TG

Test 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

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DSC – (A)DSC  (A)

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DSC (B)DSC – (B)

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ResultsTest Group Results

ResultsTime 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 CIsothermal Temperature: 288 C

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T 260T-260

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T 288T‐288

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ResultsT G R l

ResultsTest Group Results

Weight Loss % by TGATest 1 of 1

Percent Weight Loss: 0.2%

Start Temperature: 0º C

Stop Temperature: 0º CStop Temperature: 0º C

Comments: Moisture Method

% Weight Loss = 0.1717%

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Moisture Absorption (A)Moisture Absorption (A)

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ResultsTest Group Results

ResultsTest Group Results

Peel Strength

Condition: Condition A

Peel Strength Side 1: 11.73 lbs/in

Peel Strength Side 2: 10.95 lbs/inPeel Strength Side 2: 10.95 lbs/in

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6 X ReflowPb f bl

6‐X ReflowPb‐free Assembly Temperature

– One board, 3 array– One 4.25 x 9.5L”, Two 4.75 x 9.5L”– Thickness + 0.0633– TGA moisture = 0.2534%– 260° Peak Temperaturep

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ResultsConditioning As Received

ResultsBoard # 14753-1Material IS400

Thickness (mil) 0.063( )

Conveyor Speed (cm/min) 48

Peak Mean Temp (°C) 259.8

TC Temp Range 3.4TC Temp Range 3.4

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

Time above 217 101

Time above 255 19 69Time above 255 19.69

Passes to Fail 6x‐Pass

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Coming Soon – FR406HR

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Section 2Pb FreePb‐FreeHASL

Audience Poll30

• Have you ever tried and subsequently abandoned SN100CL?

• Yes• No• Never even tried it.

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Poll Results

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DefinitionDefinitionSN100CL‐this is a SnCu alloy stabilized with Ni, composed of:composed of:

• 99.3% Tin• <0 7% Copper• <0.7% Copper• 0.05% Nickel• 60 ppm Germaniumpp

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Industry yMisconceptions

• Predictions of HASL’s DemiseS ld bili  I• Solderability Issues

• Short Duration of Usage• Short Duration of Usage

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BenefitsBenefits1. Lower Copper Erosion on PCB surface and vias

Q i k P2. Quick Process3. Long Shelf Life4.   Cost

(< 1/14 ENIG)

5. Forgivinga.) Humidityyb.) Handlingc.) Temperature

6. Solder Joint Strength

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Results( using Florida CirTech HALTexample )

ResultsHighly Accelerated Life Test

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Benefits – Solder Joint StrengthJ gHALT Test Results

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Benefits –HALT Test ResultsBenefits –HALT Test Results

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BenefitsBenefits

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Benefits Benefits 

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HALT Test ResultsHALT Test ResultsLead-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 reportOur 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]

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DrawbacksDrawbacks• Not Planar

• Not Ideal for extremely fine pitch applications

• Past Solderability IssuesPast 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 theRequest a copy from James Kelch or visit theLead Free Resource Center on our website.

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Drawbacks  contDrawbacks, cont.• Thermal Cycle• Thermal Cycle

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

• No Set Industry StandardsNo Set Industry Standards– Neither the IPC nor Nihon Superior had developed a Thickness Acceptability Criteria when SN100CL was introduced Audience Poll

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P lli  Q tiPolling Question

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• What is your primary Lead Free finish?

• ENIG• Lead Free HASL• Immersion Silver• Immersion Tin• RoHS Compliant

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Poll ResultsPoll Results

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No Standard ‐ SolutionsTrigger Event 

No Standard  SolutionsTrigger Event Solderability Issue at Customery

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No Standard  SolutionsNo Standard ‐ Solutions• Goal• Goal

–Establish a Set Criteria

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Thickness CriteriaThickness Criteria• Generic Thickness Requirementq

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

• Solution• Minimum Alloy Thickness should be        Minimum Alloy Thickness should be        segregated by Ranges of Pad Size

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Pad Size (mils) Min. Thicknessad S e ( s) c ess

126 x 131 50 uin

29 x 83 80 uin

17 x 36 100 uin17 x 36 100 uin

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ImplementationImplementation• Alloy ControlAlloy Control

• Lower copper content of alloy increases solderabilitypp y y• Standard Drossing of solder pot is not enough to keep copper content below 0.90%

• Recommend a  1/4 1/4 ‐‐ 1/3 1/3 solder pot dump once weekly measurement reaches 0.90%

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Implementation• Specific Design Set‐Up

ImplementationSpecific Design Set Up– Each Design may require its own specific set‐upAdj t t– Adjustments

• Air Knife Pressure• Retract Speed• Retract Speed• Dwell Time

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Implementation• In effect, since the operating window is 

Implementation

smaller than with SnPB,…….

CONTROL The PROCESS!!!

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SN100CL Study Conclusion

• No Solderability Issues at any customer• 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:

C l    h  P»Control over the Process54

Conclusion• By implementing one or both of these proposed solutions  you can:proposed solutions, you can:– Save up to 30% of your bare board costI   f   f    d– Increase performance of your products

– Standardize your fab notes to remove risk of f i   d tnon‐performing products

– Improve your supply base

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

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Thank You!

Saturn Electronics Corporation would like to thank our presenters:

Dave Coppens / Isola Terry Staskowicz / Insulectro Terry Staskowicz / Insulectro Glenn Sikorcin / Florida CirTech

*Don’t forget to visit the Lead Free Resource Center57