Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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Coating Brush Touch-up

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Coating Brush Touch-up | 2 December, 2008

Hey guys, just joined the site and I'm looking for some help.

In our coating department we are running a Asymtek C-740 with a Jet and film coater. The coating that we are using is Humiseal 1B73 acrylic. The problem that we are having is that the CCA will come out of the machine with a minimal amount of bubbles and the bubbles will find their way out of the coating. But when we touch up the boards after automated coating we are getting a ton of bubbles in-between close chip components. Although these bubbles are small our customer is rejecting them.

The bubbles are coming from dragging the brush across the CCA. We are trying to figure out either something to do to the coating/thinner mix or another way of applying the mix to help fix this problem.

So far we've tried using straight 1B73 all the way up to 1 to 1 with 1B73 and 521 thinner with no luck. So if you guys have any ideas or experience that would be great.

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Coating Brush Touch-up | 3 December, 2008

It's your not your mix, it's your technique. Use a small squirt bottle with a syringe tip to apply the material.

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Coating Brush Touch-up | 4 December, 2008

We have the same Asymtek machine, same Humiseal product, same bubbling issue on touch ups. Ive found that very light pressure and a thinner mixture usually yields good results for us. Generally I dip the brush in the mixture and let it drip near where it needs to be then just kind of steer it with the brush. I try not to let the operators brush the surface of the PCB enough so that the bristles deflect. That will certainly induce unwanted air pockets.

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Coating Brush Touch-up | 16 February, 2009

Hey, are you the Phil that work's up the hill? Or the Phil that sits at his desk and doesn't work up the hill?

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Coating Brush Touch-up | 16 February, 2009

LOL..LOL. I can't help but laugh at the name of your link.

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Coating Brush Touch-up | 17 February, 2009

It depends on who's in the office. If someone's in here then I'm the one who works, but if nobody's in here then I just sit at the desk.

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