Hi guys,
Recently I encountered a solder crack issue on my PCB and was wondering if anyone else has ever encountered such (I am sure someone here would have).
The problem is caused by an IC which has 48pin TSOP package, possibly with an alloy42 lead frame (CTE = 5 ppm/degC). Cause of high-temperature requirements, my PCB is polyimide (Arlon85: CTE = ~19 ppm/degC). I was testing temperature cycles (-20degC to +125degC, ramp = 3degC/min) on this PCB and after a few thousand cycles, the solder started developing cracks. I've tried SAC305, SN63, and HMP(Pb93.5) so far and now testing Au80 as a last resort.
One solution might be to change PCB material, but that would need extra qualifications. I was reading about CIC and CBM, but CIC is magnetic and such. Any recommendations here?
Another solution might be to mount this IC on a custom package (to match CTEs appropriately). Keep leads to be Copper (CTE = 17 ppm/degC) and match package material to alloy42. But again, extensive qualification would pursue.
Thanks for the ears
Recently I encountered a solder crack issue on my PCB and was wondering if anyone else has ever encountered such (I am sure someone here would have).
The problem is caused by an IC which has 48pin TSOP package, possibly with an alloy42 lead frame (CTE = 5 ppm/degC). Cause of high-temperature requirements, my PCB is polyimide (Arlon85: CTE = ~19 ppm/degC). I was testing temperature cycles (-20degC to +125degC, ramp = 3degC/min) on this PCB and after a few thousand cycles, the solder started developing cracks. I've tried SAC305, SN63, and HMP(Pb93.5) so far and now testing Au80 as a last resort.
One solution might be to change PCB material, but that would need extra qualifications. I was reading about CIC and CBM, but CIC is magnetic and such. Any recommendations here?
Another solution might be to mount this IC on a custom package (to match CTEs appropriately). Keep leads to be Copper (CTE = 17 ppm/degC) and match package material to alloy42. But again, extensive qualification would pursue.
Thanks for the ears