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how to remove bubbles on silicone coating?

Views: 6877

#64582

how to remove bubbles on silicone coating? | 4 July, 2011

we encounter bubbles on silicone coating after oven curing.what to do to avoid bubbles?

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#64583

how to remove bubbles on silicone coating? | 4 July, 2011

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 problem * Coating thickness * Cure profile * ... etc

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#64584

how to remove bubbles on silicone coating? | 4 July, 2011

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.

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#64587

how to remove bubbles on silicone coating? | 5 July, 2011

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.

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#64588

how to remove bubbles on silicone coating? | 5 July, 2011

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.

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Lou

#64597

how to remove bubbles on silicone coating? | 6 July, 2011

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.

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#64599

how to remove bubbles on silicone coating? | 6 July, 2011

we are using the silicone Dow Corning JCR6101UP. we use it to coat the whole die including the wires.

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Lou

#64604

how to remove bubbles on silicone coating? | 7 July, 2011

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 knowing the details of what you are coating, how, etc. I would suggest you contact Dow's tech help. They are a wealth of knowledge on their own products.

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#64634

how to remove bubbles on silicone coating? | 11 July, 2011

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.

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