Hi Technetters,

Does anyone have experience with TSOP-48 crack solder joint?
This is a 6"x8" FR4, Tg 170 deg.C, 80-mil thickness board with total 32 TSOP on both side line up in a 2.5"x4" area. They are mirror-image locations, 16 TSOP on each side.
The board passed first temperature cycle (-40deg.C to 71deg.C) test for the first time. Then customer sends out to do BGA underfilling (Loctite 3653). After underfilling
process finished, the board goes through 2nd identical temperature cycle test. But this time it starts to fail after 5th cycle. Most of TSOP devices on bottom side have crack
joint on one end. But TSOP on top side have much much less failure. The cracks are long the pin contact area. We visit underfilling shop. All the processing temperature is
quite low comparing to reflow temperature. The reflow temperature of TSOP is 210 deg.C peak temp, 80 sec above 183 deg.C and the ramp rate is 2 deg.C/sec. Total reflow time is
less than 6 minutes. No wave soldering process.
So what do you think the root cause is? Any experience and thought are very appreciated.

Thank a million,
Wei Wang
Process Engineer
Sanmina-SCI

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