Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

POP Flux

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POP Flux | 13 December, 2007

Any recommendations/data on a superior flux to use for Package on Package assembly? Also, any guidelines on flux depth, viscosity, etc... are welcome.

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POP Flux | 21 December, 2007

Hi smtdude- I'm no expert at PoP (yet!) as we've only done a few weeks worth of experiments for a new customer but what i can tell you is 25-50% of the ball height (not diameter) is a good rule of thumb for the flux depth, at least to start. I can say that different fluxes will give you different depths using the same tool so some experimentation will be in order, depending on the flux requirement of your customer. We used a Universal LTFA (Linear Thin Film Applicator) "feeder" for our work. This had interchangeable plates of varying depths, depending on the thickness you want to achieve. We were finding a .012" plate would give us about .007" flux depth, which was in that 25-50%-of-ball-height range I mention above.

It's a neat process and we're looking forward to doing more work with it in the near future. Good luck with your project.

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