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BGA Bouble sided reflow overlapping

Ron Lahat


BGA Bouble sided reflow overlapping | 5 January, 2000

I have in design a 400mm x 400mm pcb 3.0 mm thick heavily populated with BGAs 50 mil pitch and want to run a double sided reflow process with overlapping BGAs (CS/PS)

1. can I avoid a selective jig for PS BGAs?(weight calculation ?) 2. Is it possible and wise to reflow BGAs that have 100% overlap,one on CS and the other on PS ? 3. Do you know any articles that can help developing a process 4. What about rework when you have overlapping BGAs (CS/PS) ? 5. Need advise on a way to determine the two profiles, should I add to the pcb design features that will help in the process ?


Ron Lahat

I will give feedback on any advise as we progress

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Re: BGA Bouble sided reflow overlapping | 11 January, 2000

What a challenge! I think it all depends on the equipment used. Seems rereflow of BGA isn�t that good (see the advices for wavesoldering BGA populated boards). Although you might check for the tacking force by sending a sample BGA board head over through a second reflow cycle and check the results. Rework also depends on your equipment and I think it takes some effort to get adequate profiles. You should try that first taking a lot of temperature measurements to make sure you don�t damage the boards. Just glue one BGA underneath and measure the temperature while de-/soldering the other ( might look different with vias transporting heat). Or switch to the old method for removal, twist it off (old story told by some guys about IBM). Try to avoid to much soldercycles for the units, two reflow and best only selective wave soldering or pressfit connectors. Avoid exessive overlapping let it be the exception.

Might not help much


PS: What is meant by CS/PS ?

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