RoHS Compliant Lead Free PCB Fabrication

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Suggested RoHS compliant lead free PCB fabrication notes and process.

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RoHS Compliant Lead Free PCB Fabrication

  1. 1. Lead Free Cost Reduction
  2. 2. Direct Cost Drivers –High Temp Laminates –Final Finishes 2
  3. 3. Indirect Cost Drivers –Increased Scrap Rate • De-lamination • Solderability –Pre-Baking –Storage / Handling 3
  4. 4. Section 1 Pb-free Assembly Capable Laminate 4
  5. 5. IPC 4101/99 /124 from Isola Group/ Insulectro 5
  6. 6. Current State Audience Poll…… –Common Callouts • IS410 / 370HR • FR4 • RoHS Compliant • 180ºC Tg • 340ºC Td • IPC 4101/126 or /129 6
  7. 7. Polling Question 7
  8. 8. Current State (cont.) Audience Poll…… • Effect of Common Callouts 1. Locked in to laminate by brand name 2. 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
  9. 9. Current State (cont.) 3. Non-Pb Free capable material • FR4 is not capable • RoHS Compliant can include standard FR4 • 180Tg does not guarantee adequate Td 9
  10. 10. Proposed Solution • Mid-Grade Pb-free capable laminates – IPC 4101 / 99 (filled) or /124 (unfilled) • 150 Tg min. • 325 Td min. 10
  11. 11. Benefits – 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
  12. 12. Results (using Isola IS400 as example) 12
  13. 13. Results Test Group Results Decomposition Temperature Test 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
  14. 14. TGA 14
  15. 15. Results Test Group Results Delta TG Test 1 of 1 Method of Determination: DSC TG Scan 1: 150 C TG Scan 2: 154 C Delta Tg: 4C Ramp Rate: 20 C/min Analysis Method: Half Height 15
  16. 16. DSC – (A) 16
  17. 17. DSC – (B) 17
  18. 18. Results Test Group Results Time to Decomposition at Temperature Test 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
  19. 19. T-260 19
  20. 20. T-288 20
  21. 21. Results 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
  22. 22. Moisture Absorption (A) 22
  23. 23. Results 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
  24. 24. 6-X Reflow 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
  25. 25. 25
  26. 26. Results Conditioning As Received Board # 14753-1 Material 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
  27. 27. Coming Soon – FR406HR 27
  28. 28. Section 2 Pb-Free HASL Audience Poll 28
  29. 29. Definition SN100CL -this is a SnCu alloy stabilized with Ni, composed of: • 99.3% Tin • <0.7% Copper • 0.05% Nickel • 60 ppm Germanium 29
  30. 30. Industry Misconceptions • Predictions of HASL’s Demise • Solderability Issues • Short Duration of Usage 30
  31. 31. Benefits 1. Lower Copper Erosion on PCB surface and vias 2. Quick Process 3. Long Shelf Life 4. Cost (< 1/14 ENIG) 5. Forgiving a.) Humidity b.) Handling c.) Temperature 6. Solder Joint Strength 31
  32. 32. Results ( using Florida CirTech HALT example ) Highly Accelerated Life Test 32
  33. 33. Benefits – Solder Joint Strength HALT Test Results 33
  34. 34. Benefits –HALT Test Results 34
  35. 35. Benefits 35
  36. 36. Benefits 36
  37. 37. HALT Test Results 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 @ jim@saturnelectronics.com 37
  38. 38. 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
  39. 39. 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. 40. Polling Question 40
  41. 41. No Standard - Solutions Trigger Event Solderability Issue at Customer 41
  42. 42. No Standard - Solutions • Goal – Establish a Set Criteria 42
  43. 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 43
  44. 44. Pad Size (mils) Min. Thickness 126 x 131 50 uin 29 x 83 80 uin 17 x 36 100 uin 44
  45. 45. 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% 45
  46. 46. Implementation • Specific Design Set-Up – Each Design may require its own specific set-up – Adjustments • Air Knife Pressure • Retract Speed • Dwell Time 46
  47. 47. Implementation • In effect, since the operating window is smaller than with SnPB,……. CONTROL The PROCESS!!! 47
  48. 48. 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 Process 48
  49. 49. 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
  50. 50. • To view the archived version of this presentation, please email jim@saturnelectronics.com • To sign up for our upcoming Lead Free Newsletter, please email jay@saturnelectronics.com 50
  51. 51. Thank You! Saturn Electronics Corporation would like to thank our presenters: Ø Dave Coppens / Isola Ø Terry Staskowicz / Insulectro Ø Glenn Sikorcin / Florida CirTech *Don’t forget to visit the Lead Free Resource Center 51

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