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Lead Free BGA AATC Reliability

Lead Free BGA AATC Reliability. Round Robin Testing : UIC, Motorola and Rockwell Collins. BGA Component. Glass Die. Solder Bumps. Encapsulant Layer. 1.27mm pitch, 256 I/O daisy chain 0.030” diameter SMD pads 0.030” diameter spheres (variable alloy) 0.003” encapsulant

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Lead Free BGA AATC Reliability

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  1. Lead Free BGA AATC Reliability Round Robin Testing : UIC, Motorola and Rockwell Collins

  2. BGA Component Glass Die Solder Bumps Encapsulant Layer • 1.27mm pitch, 256 I/O daisy chain • 0.030” diameter SMD pads • 0.030” diameter spheres (variable alloy) • 0.003” encapsulant • 0.016” FR4 substrate • 0.040” glass die • 2.95 grams average weight • Electroless nickel / immersion gold finish

  3. Test Board 6 • 0.062” thick FR4 • Eight BGAs per board • 0.020” (2), 0.022” (4), & 0.024” (2) NSMD pads • Three surface finishes: • Electroless nickel / immersion gold (ENIG) • Copper OSP • Immersion silver (ImmAg)

  4. Assembly - Stencil 5 mil thick Laser cut Stainless steel Nominal Values Note that square, not circular, apertures were used for this experiment.

  5. Assembly - Pastes 4 pastes with compositions identical to the solder balls were used: • Sn/Ag (96.5,3.5); • Sn/Ag/Cu (95.5/3.8/0.7); • Sn/Ag/Cu/Sb (96.2/2.5/0.8/0.5) (Castin), • Sn/Pb (63/37) All pastes were type III or type IV No Clean formulations supplied by the same vendors as those used in the previous study. Assembly - Bake Out All BGA components were pre-baked at 125oC for a minimum of 8 hours prior to reflow.

  6. Lifetime & Data Analysis • Characteristic Lifetime analysis was performed with the use of • Winsmith Weibull Software. Characteristic Lifetime is the number • of cycles required for 63.2% of the sample set to fail. • Lifetime was calculated for each metallurgy-pad finish combination. • PCB pad size and printed paste volume effects were not considered. • Failures not associated with in-plane solder fatigue (as determined by cross sectioning) were excluded from lifetime calculations. • Predicted lifetimes were computed using beta (slope) values from the sample set utilizing the same solder alloy and a confidence level of -95% to produce conservative estimates. • Most failures were removed from the thermal chambers following the onset of events. Event detection behavior not characterized.

  7. UIC SnPb Reflow Profile Peak 219oC Time Above Liquidus = 44 seconds 2.67oC/sec Cooling Nitrogen Atmosphere (O2 < 30 ppm)

  8. UIC Pb-Free Reflow Profile Peak 241oC Time Above Liquidus = 45 seconds 2.55oC/sec Cooling Nitrogen Atmosphere (O2 < 30 ppm)

  9. UIC Temperature Cycle (Air to Air) 0/100C AATC 104 maximum -4 minimum 5 minute ramp 5 minute dwell

  10. UIC Reliability Summary* PCB # Failures / First Failure N63 Solder Alloy Finish # Samples (cycles) (cycles) ENIG 32/32 6801 12715 SnPb Cu OSP 8/8 7335 9850 ENIG 23/28 7598 14600 SnAgCu Cu OSP 0/8 NA >16700 ENIG 24/38 5033 15200 SnAgCuSb Cu OSP 13/21 9555 16500 ENIG 7/32 8928 24700 SnAg Cu OSP 2/2 9398 NA *Adjusted for non-fatigue failures. Test halted following 16700 cycles.

  11. UIC SnPb Data 99 0/100C AATC Lowest N63 ENIG PCB: First Failure @ 6801 Final Failure @ 16698 N63 = 12715 Cu OSP PCB: First Failure @ 7335 Final Failure @ 11066 N63 = 9850 95 CMP205112 90 80 70 60 50 40 30 20 OCCURRENCE CDF % 10 5 2 1 1000 10000 Cycles to Failure CMP205152

  12. UIC SnPb Data Failure Frequency SnPb on ENIG 27 Components Failure Frequency SnPb on Cu OSP 8 Components

  13. CMP205152: First UIC SnPb Failure 0/100C AATC Failure @ 6801 Removed After Cycle 6802 6 Events Detected 4.42 Ohm Initial Resistance 4.78 Ohm Final Resistance ENIG PCB Outer Corner of Package Component Side Solder Fatigue SnPb Solder Fatigue

  14. CMP205112: Final UIC SnPb Failure 0/100C AATC Failure @ 16698 Removed After Cycle 16700 2 Events Detected 5.80 Ohm Initial Resistance 6.38 Ohm Final Resistance ENIG PCB No Joint Isolated by 4 Point Cleaving in Outer Row Potential Cleaving of SnPb Solder Joint

  15. UIC SnAgCu Data 90 0/100C AATC ENIG PCB: First Failure @ 2465 Second Failure @ 7598 N63 = 14600 *No Failures on Cu OSP Through 16700 Cycles* 20300 N63 Prediction 80 70 60 50 40 30 Cu OSP Predicted 20 \WB c=-95 OCCURRENCE CDF % 10 5 CMP205048 2 1 1000 10000 Cycles to Failure CMP205045 (Excluded from Lifetime Analysis: Interfacial Failure)

  16. UIC SnAgCu Data Failure Frequency SnAgCu on ENIG 21 Components

  17. CMP205045: First UIC SnAgCu Failure 0/100C AATC Failure @ 2465 5.1 Ohm Initial Resistance Electrically Open at Removal ENIG PCB Outer Corner of Package Non-Solder Fatigue Failure Enlarged Image Interfacial Failure

  18. CMP205048: First UIC SnAgCu Fatigue Failure 0/100C AATC Failure @ 7598 Removed After Cycle 7633 5.10 Ohm Initial Resistance 5.20 Ohm at Removal ENIG PCB Outer Corner of Package Component Side Solder Fatigue SnAgCu Solder Fatigue

  19. UIC SnAgCu Failure Modes CMP205057 SnAgCu on ENIG 11938 CTF PCB Side Fatigue Failure 5.21 Ohm Initial Resistance 5.99 Ohm Final Resistance CMP205052 SnAgCu on ENIG 10880 CTF Component Side Fatigue Failure 5.17 Ohm Initial Resistance 20.0 Ohm Final Resistance

  20. UIC SnAgCu Failure Modes CMP205034 SnAgCu on ENIG 16700 Cycles to Removal Electrically Good, Non-Failure CMP205036 SnAgCu on ENIG 14115 CTF Electrically Good Joint Cracks Visible in X-ray

  21. UIC SnAgCuSb Data 90 0/100C AATC ENIG PCB: N63 = 15200 Cu OSP PCB: N63 = 16500 80 70 60 50 40 30 20 Glass Delamination (Excluded) OCCURRENCE CDF % 10 5 Excluded Interfacial Failure (Excluded) 2 1 1000 10000 Large Void(s) (Included) Cycles to Failure

  22. UIC SnAgCuSb Data Failure Frequency SnAgCuSb on ENIG 19 Components Failure Frequency SnAgCuSb on Cu OSP 10 Components

  23. Effects of Delamination Delamination is the separation of the underfill material from the substrate and/or the glass die. Primarily occurs during reflow operations. Delamination affects both in-plane and out-of-plane stresses. Some degree of delamination located near the center of the package is acceptable. Delamination may be visible to the naked eye or may require C-SAM to identify. Visible Delamination CMP205126 SnAgCuSb on Cu OSP 2137 CTF Effect of Delamination

  24. Effects of Delamination : Warpage Room Temperature CMP205126 SnAgCuSb on Cu OSP PCB 100 Degrees Celsius

  25. UIC SnAgCuSb Failure Modes CMP205132 SnAgCuSb on Cu OSP 3990 CTF Interfacial Failure 4.51 Ohm Initial Resistance 4.62 Ohm Final Resistance CMP205013 SnAgCuSb on ENIG 6105 CTF Solder Fatigue through Large Voids 5.39 Ohm Initial Resistance 5.70 Ohm Final Resistance

  26. UIC SnAgCuSb Failure Modes CMP205011 SnAgCuSb on ENIG 10921 CTF Typical Failure Cracks on Component and PCB Side Numerous Voids Present 5.93 Ohm Initial Resistance 6.02 Ohm Final Resistance CMP205919 SnAgCuSb on ENIG 16700 Cycles to Removal Electrically Good, Non-Failure Cleaving Observed in Outer Row

  27. UIC SnAg Data 90 0/100C AATC Highest N63 ENIG PCB: First Failure @ 8928 7th Failure @ 15896 24702 N63 Prediction Cu OSP PCB: First Failure @ 1534 Final Failure @ 10204 6/8 Defective No Prediction Provided 80 70 60 50 40 30 20 OCCURRENCE CDF % 10 5 2 1 1000 10000 Cycles to Failure

  28. UIC SnAg Data Failure Frequency SnAg on ENIG 7 Components Failure Frequency SnAg on Cu OSP 2 Components

  29. UIC SnAg Data CMP205074 SnAg on Cu OSP 1534 CTF Glass Delamination CMP205069 SnAg on Cu OSP 4575 CTF Interfacial Failure Electrically Open Upon Failure

  30. UIC SnAg Data CMP205070 SnAg on Cu OSP 10204 CTF PCB Side Solder Fatigue 5.10 Ohm Initial Resistance 40.56 Ohm Final Resistance Cu Thick Cu-Sn Intermetallics Non-reflow Voids

  31. Motorola SnPb Reflow Profile Peak 221oC 1.3oC/sec Cooling TAL = ~115 seconds Nitrogen Atmosphere

  32. Motorola Pb-Free Reflow Profile Peak 242oC 1.2oC/sec Cooling TAL = 46 seconds Nitrogen Atmosphere

  33. Motorola Temperature Cycle (Air to Air) 0/100C AATC 107 maximum -7 minimum 10 minute ramp 5 minute dwell

  34. PCB # Failures / First Failure N63 Solder Alloy Finish # Samples (cycles) (cycles) ENIG 14/14 5885 8495 SnPb Cu OSP 8/8 7631 8730 ENIG 14/16 7356 10290 SnAgCu Cu OSP 7/8 8051 10870 ENIG 7/8 7713 9295 SnAgCuSb Cu OSP 1/8 11261 >13707 ENIG 4/16 7812 15318 SnAg Cu OSP 1/8 13521 >13707 Motorola Reliability Summary* *Adjusted for non-fatigue failures. Based on data accumulated through 13707 cycles.

  35. Motorola SnPb Data 99 0/100C AATC Lowest N63 ENIG PCB: First Failure @ 2959 Final Failure @ 9914 N63 = 8495 Cu OSP PCB: First Failure @ 7631 Final Failure @ 9179 N63 = 8730 95 90 80 70 60 50 40 30 20 OCCURRENCE CDF % CMP205656 10 5 2 1 1000 10000 Cycles to Failure Excluded (Interfacial Failures)

  36. Motorola SnPb Data Failure Frequency SnPb on ENIG 7 Components Failure Frequency SnPb on Cu OSP 4 Components

  37. Motorola SnPb Failure Modes CMP205225 SnPb on ENIG 2959 CTF Interfacial Failure CMP205219 SnPb on ENIG 3020 CTF Interfacial Failure

  38. Motorola SnPb Failure Modes CMP205656 SnPb on ENIG 5885 CTF First Solder Fatigue Failure

  39. Motorola SnAgCu Data 90 0/100C AATC ENIG PCB: First Failure @ 7356 14th Failure @ 11188 N63 = 10290 Cu OSP PCB: First Failure @ 8051 7th Failure @ 12200 N63 = 10870 80 70 60 50 40 30 20 CMP205625 OCCURRENCE CDF % CMP205563 10 5 2 1 1000 10000 Cycles to Failure

  40. Motorola SnAgCu Data Failure Frequency SnAgCu on ENIG 7 Components

  41. Motorola SnAgCu Failure Modes CMP205563 SnAgCu on ENIG 7356 CTF First SnAgCu Solder Fatigue Failure

  42. Motorola SnAgCu Failure Modes Non-reflow Voids Copper Silver Needle CMP205625 First SnAgCu on Cu OSP PCB Failure 8051 CTF

  43. Motorola SnAgCuSb Data 90 80 0/100C AATC ENIG PCB: First Failure @ 7713 7th Failure @ 11062 N63 = 9295 Cu OSP PCB: First Failure @ 11261 14245 N63 Prediction 70 60 50 40 30 \WB c=-95 CMP205455 20 Cu OSP Predicted OCCURRENCE CDF % 10 5 2 1 1000 10000 Cycles to Failure

  44. Motorola SnAgCuSb Failure Modes Cleaving? CMP205455 SnAgCuSb on ENIG 7713 CTF First SnAgCuSb Solder Fatigue Failure

  45. Motorola SnAg Data 90 80 0/100C AATC ENIG PCB: First Failure @ 6945 4th Failure @ 12858 15318 N63 Prediction Cu OSP PCB: First Failure @ 13521 16000 N63 Prediction 70 60 Cu OSP Predicted 50 ENIG Predicted 40 30 20 \WB c=-95 OCCURRENCE CDF % \WB c=-95 CMP205426 10 5 2 1 1000 10000 Cycles to Failure

  46. Motorola SnAg Data Failure Frequency SnAg on ENIG 4 Components

  47. Motorola SnAg Failure Modes CMP205426 SnAg on ENIG 6945 CTF First SnAg Solder Fatigue Failure

  48. Rockwell Data -55 to 125oC Air to Air Thermal Cycle All Components were Assembled to Immersion Silver PCBs All Components were Assembled with SnAgCu (95.5/3.8/0.7) Solder Paste: Alloy Composition % on .022" Pad Sphere Alloy Sn Pb Ag Cu 63Sn37Pb 65.270 34.419 0.263 0.049 96.5Sn3.5Ag 96.432 0.000 3.519 0.049 95.5Sn3.8Ag.7Cu 95.500 0.000 3.800 0.700 Estimated alloy % based on 90% paste transfer and 50% solidified paste volume.

  49. Rockwell Reliability Summary* PCB # Failures / First Failure N63 Solder Alloy Finish # Samples (cycles) (cycles) SnPb ImmAg 16/32 413 1990 SnAgCu ImmAg 13/32 367 2860 SnAg ImmAg 9/31 467 2667 *Adjusted for non-fatigue failures. Based on data accumulated through 2000 cycles. ENIG components

  50. Rockwell Reliability Data ENIG Components on ImmAg PCBs 90 -55/125C AATC ImmAg PCB: SnPb N63 = 1990 SnAg N63 = 2667 SnAgCu N63 = 2860 80 70 60 50 40 30 20 OCCURRENCE CDF % 10 CMP205205 Excluded 5 2 1 100 1000 Cycles to Failure

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