rohs compliant lead free pcb fabrication
DESCRIPTION
Suggested RoHS compliant lead free PCB fabrication notes and process.TRANSCRIPT
Lead FreeCost Reduction
–High Temp Laminates–Final Finishes
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Direct Cost Drivers
–Increased Scrap Rate• De-lamination• Solderability
–Pre-Baking–Storage / Handling
Indirect Cost Drivers
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Section 1
Pb-free Assembly
Capable Laminate4
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IPC 4101/99 /124 from
Isola Group/ Insulectro
–Common Callouts• IS410 / 370HR• FR4• RoHS Compliant• 180ºC Tg• 340ºC Td• IPC 4101/126 or /129
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Current StateAudience Poll……
Polling Question
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• 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
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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
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Current State (cont.)
Proposed Solution
• Mid-Grade Pb-free capable laminates– IPC 4101 / 99 (filled) or /124 (unfilled)
• 150 Tg min.• 325 Td min.
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– 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
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Benefits
(using Isola IS400 as example)
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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
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Results
TGA
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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
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Results
DSC – (A)
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DSC – (B)
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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
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Results
T-260
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T-288
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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%
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Results
Moisture Absorption (A)
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Test Group Results
Peel Strength
Condition: Condition A
Peel Strength Side 1: 11.73 lbs/in
Peel Strength Side 2: 10.95 lbs/in
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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
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6-X Reflow
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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
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Results
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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
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Industry Misconceptions
• Predictions of HASL’s Demise• Solderability Issues• Short Duration of Usage
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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
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( using Florida CirTech HALTexample )Highly Accelerated Life Test
Results
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Benefits – Solder Joint StrengthHALT Test Results
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Benefits –HALT Test Results
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Benefits
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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]
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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.
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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
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Polling Question
Trigger Event Solderability Issue at Customer
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No Standard - Solutions
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No Standard - Solutions• Goal
– Establish a Set Criteria
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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
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Implementation
• In effect, since the operating window is smaller than with SnPB,…….
CONTROL The PROCESS!!!
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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
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• 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]
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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