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