Electronics Forum | Mon Jul 04 01:30:24 EDT 2011 | rickysanchez
we encounter bubbles on silicone coating after oven curing.what to do to avoid bubbles?
Electronics Forum | Wed Jul 06 15:52:36 EDT 2011 | duso02
Ricky What silicone coating are you using? Are you using at as a coating or as a potting? In other words how thick are you applying it.
Electronics Forum | Tue Jul 05 16:14:06 EDT 2011 | blnorman
Is this an addition-cure silicone? We once had coating bubbling caused by the evolution of the solvent in the paste flux under leadless components.
Electronics Forum | Wed Jul 06 20:05:02 EDT 2011 | rickysanchez
we are using the silicone Dow Corning JCR6101UP. we use it to coat the whole die including the wires.
Electronics Forum | Mon Jul 04 20:10:05 EDT 2011 | rickysanchez
1.The bubbles appear only after the oven curing.before curing no bubbles encounterred. 2.The bubbles were very small, and can be found around the die in between the die and the epoxy. 3.Curing time is 150 degC for 4 hours.
Electronics Forum | Mon Jul 11 11:40:11 EDT 2011 | blnorman
According to the datasheet, this is a LED encapsulant, is that how you are using it? It also had a section on compatibility, which indicates that it is an addition-cure silicone prone to cure inhibition.
Electronics Forum | Tue Jul 05 17:43:43 EDT 2011 | davef
We agree. As Bill says, given that you seem to have bubbles in a restricted area and not broadly dispersed across your board, this seems to indicate an interaction between process materials, rather than a cure or thickness issue.
Electronics Forum | Thu Jul 07 10:07:40 EDT 2011 | duso02
Interesting stuff. I must admit that I am unfamiliar with that product but we use quite a bit of Dow and they are overall excellent silicone coatings. We do nothing but conformal coating here and bubbles are usually from curing to quickly. Without kn
Electronics Forum | Mon Jul 04 14:21:14 EDT 2011 | davef
The three primary causes for bubble generation in solvent-based coatings are: * Air entrapment * Solvent flash-off * Curing the coating too quickly Tell us more about your process including: * When you first notice the bubbles * Extent of the probl
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