My Production runs a uBGA-liken product, and uses Pallets to support the 0.8mm thick pcb, during the SMT + reflow oven process.
Process/QA see occurs: 1) 0402 unsolder? 2) 0402 tombstone? 3) "uBGA" poor-visual joints (dry joints)?
Took a thermal profile, all process parameter maintained the same : (A) x1 pcba with Pallet support, (B) x1 pcba (same) without Pallet support.
Findings: 1) dipping of profile occurs in (A), 2) Oven zone : heat-transfer problem in (A), 3) non-uniform RAMP rate in (A), 4) heat (energy) dissipation in (A), 5) peak-temperature : (B)-(A)= +10 deg-C difference
Question : 1) To offset the heat-absorb ability of the Pallet, that artifically lowers my pcba temperature, is it advisable to artifically increase the overall, oven zone temperatures? 1b) estimate by +10 deg-C each zone?
2) If decide not to uniform overall increase each oven zone, any ideas how to accurately measure the Pallet heat-absorb rates, during each stage of the oven zone travel?
3) Note : Pallet material is "durapol IGM L 100"?
4) Anyone has experience in Pallet absorption issues, that lowered the overall oven zone temperatures, that resulted in : a) unsolder? b) tombstone? c) uncooked (dry) solder joint?
Appreciate any feedback.
Regards, ianchan 09 june 2001