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Conformal coating bubbles with 1B73

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#63714

Conformal coating bubbles with 1B73 | 8 February, 2011

Conformal coat bubbles using 1B73 and SC-205 nozzle I've read most of the posts on this subject. I'm using the SC-205 (airless) fan nozzle and 400 needle to apply 1B73 mixed with xylene thinner. I have micro bubbles which come directly out of the nozzles and form on the board. If its allowed to sit (5 min) on the line 60-70% will clear. Some will not and some will form into larger bubbles (top of components). To top this off, 1.manufacturing does not wish to let the boards wait. 2. They have a process to flip the board and coat the top side (allows coating to pool with bubbles). I have tried a mixture ratios of 30-60 cps. Is there anyone running a similar process I can get initial machine settings and mixture ratios from? Note: The heat cure is low enough to prevent any additional problems.

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Lou

#63767

Conformal coating bubbles with 1B73 | 16 February, 2011

Have you always used xylene? For our 1B73 we use nothing but 73 thinner from Humiseal or PGMEA at about 50/50 depending on the humidity.

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#63768

Conformal coating bubbles with 1B73 | 16 February, 2011

I've been here approx. 3 months. It was indicated that Xylene has alwas been used but it was never indicated that bubbles were not present in the past (ignored or touchup). I have a sample of Humiseal 73 thinner ordered for testing. We've been thinned down to 40/60 using the Xylene which equates to approx. 20 sec on the zahn 2 cup. Do you use the SC-205 fan nozzle with your mixture?

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#63787

Conformal coating bubbles with 1B73 | 18 February, 2011

I have found that depressurizing the tanks when the machine is not in use reduces bubbles.

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#63789

Conformal coating bubbles with 1B73 | 18 February, 2011

That has also been the standard here. We have a urethane line which pulls a vacuum on the mixture before transfering to the can. I plan on testing this out before receipt of the 73 thinner. I've also received some feedback with indication that the micro bubbles will be present on the initial application and its the mixture thickness and flash-off time which allows these to disapate.

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#63847

Conformal coating bubbles with 1B73 | 1 March, 2011

Update on 1B73 bubbles, Changed over to a mixture of Humiseal 73 thinner with coating (25 sec on Zahn 2) observed a reduction in bubble formation (approx. 20%) but still present.

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#63849

Conformal coating bubbles with 1B73 | 1 March, 2011

If I assume you running a selective coating machine ?

Maybe you have small leak and system is sucking in air creating bubbles in mixture, like a sort of venturi action, just idea, can be a faulty fitting , elbow etc.

Have had this before....

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Lou

#63882

Conformal coating bubbles with 1B73 | 4 March, 2011

Dennis, I'm amazed that you are having this much trouble. Not trying to be a smart-a**, it's just that 73 is usually pretty easy to fix. Is there anyway you could send me some pics of what you are seeing?

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#63886

Conformal coating bubbles with 1B73 | 4 March, 2011

I'll try to get some pictures using the Ersa scope this afternoon. Not sure how to post them,may try to send directly to you.I'll take some immediately after coating then of the same after a flash off period.

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