Jeff & Ted,
we have used a dispensing system too and yes, I agree, we are not too happy with the results. Not at the point that it doesn't work, though. I think our problem basicly is that we have selected an entry-level dipensing system. We are applying dots for 50 mil pitch BGAs, mostly using #23 needles. Main problems are: - clogged nozzles whenever there is a minor inconsistency in the paste (air bubbles, etc.) - solder spheres forming slivers within the archimedes screw - it takes an eternity to purge the needle every time you start or stop work - inconsistent dots whenever anything is not 100% right For many boards, we need to clean paste off and start over. However, I have heard of excellent results by people using a high-end machine (an in-line Camelot 5000, if I'm not wrong) which has more bells & whistles built-in. Details like the software control, that allows to precisely set on-, off-, and dwell times for the dot cycle, all sum up to make the difference. So I believe dispensing is still a good choice if you can afford/justify equipment that gives you enough process control and up-time. If I had to start-up again from scratch, I would invest in looking for a dispensing system with: - enough control over process parameters - a rugged construction of the "heart" (basicly the screw, and z-height control) Now a few questions for Jeff: - which BGA stencil device and/or vendor would you recommend, and why - why are stencils "messy and time consuming"? It shouldn't be such a tricky process - or not? - what is that .... "bump the pads with solder" ????? - you too heard somebody suggesting to apply paste to the component as opposed to the PCB?
Bye,
SB
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