Hi Dean,

I've gotten them by trying to cure the coating too quickly, the coating
skins over before all the solvents have worked their way out. But here's a
good Humiseal link that gives some various causes and ways to eliminate
them:

https://blog.humiseal.com/simple-techniques-to-avoid-bubbles-in-conformal-coating#:~:text=For%20example%3A%20curing%20too%20fast,vapor%20under%20the%20coating%20surface.


Steve

On Thu, Jul 16, 2020 at 10:56 AM Stadem, Richard D <[log in to unmask]>
wrote:

> One of the client companies I work for builds extremely high-reliability
> propulsion control systems. For them, bubbles in the coating between
> fine-pitch ASIC leads are a defect condition. We are exploring options for
> elimination of the bubbles.
> The bubbles are not present in the sprayed on coating, and we have tried
> lightly brushing the leads to further "thin out" the coating before the
> CCAs go into the curing oven. No webbing or bubbles are seen at that point
> but manifest themselves after curing.
> I am not an expert at coating but I do know a bit about it. I was
> wondering just what might be the cause of the bubbles, and how to prevent
> them from happening? Any information is greatly appreciated!
> dean
>


-- 
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133

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