Electronics Forum | Wed Mar 27 18:23:01 EST 2002 | kmorris
Does anyone have experience doing conformal coating over Plastic BGA in High-Rel PCB assembly? Is underfill necessary to avoid problems with entrapped air, etc? Our application is a 17x17mm BGA, 256 I/O. We are assembling with a water soluable pas
Electronics Forum | Mon Apr 01 13:00:27 EST 2002 | BTaylor
We had a problem with conformal coating getting under an IC and with Temp. and vibration would cause cracking of the solder bump, underfill solved the problem.
Electronics Forum | Mon Apr 01 20:33:30 EST 2002 | davef
Regarding your underfil ... * What material did you use as an underfil? * What machine and technique did you use to apply the underfil? * What type of component were you underfilling? * What was the end-use environment?
Electronics Forum | Wed Apr 03 10:50:06 EST 2002 | BTaylor
Any time Dave I can tell from your responses you have been around this block as many times as I have.Your right automotive is tough nowadays not only from the quality standpoint, now they want everything for free.
Electronics Forum | Tue Apr 02 11:21:46 EST 2002 | BTaylor
davef I assume this question is for my reply and me. We used a dexter\hysol underfill and a Camalot 5700 to dispense.Single line technique next to a small IC with 14 bumps around the perimeter.The conformal coating was applied with a small brush aro
Electronics Forum | Tue Apr 02 22:52:38 EST 2002 | davef
Tks BT Can't be many places tougher than automotive, 'cept maybe oil field, down pipe. We use Dexter Hysol flow underfills for both 1 thou and 3 thou gaps, but they wouldn't come close to filling under a BGA. Most BGA are sitting about 16+ thou fr
Electronics Forum | Wed Mar 27 21:20:30 EST 2002 | davef
There is two major BGA coating camps. * Camp #1: "We require the coating to be under low stand-off devices but with no filleting. So we apply a thinned dip coat first, and then top-off with a proper spray coat" * Camp #2: "We want no coating under th
Electronics Forum | Thu Aug 27 11:35:07 EDT 2009 | davef
There are many possibilities: * Conformal coat is incompatible with surface residue on the board * Conformal coat is incompatible with solder mask on the board * Moisture is out-gassing from the board * Conformal coat is too thick and does not allow
Electronics Forum | Thu Aug 27 08:34:50 EDT 2009 | floydf
I am having trouble with little air bubbles in my conformal coat. It ranges from a few pin sized bubble to looking like spit. We are using Dow 2620 silicone conformal coat applied with a PVA sprayer machine. The conformal coat comes in bladder bags t
Electronics Forum | Fri Oct 09 16:07:30 EDT 2009 | dlabelle
We use Dow 2620 silicone conformal coat applied with PVA1000 sprayer machine. If used on a daily bases, we have no problem. If we let the machine sit idle for over a week, we will get bubbles in the conformal coating. Sometimes, purging the line w
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