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Conathane CE 1155-35 Conformal Coating Issues

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Amol

#36843

Conathane CE 1155-35 Conformal Coating Issues | 26 September, 2005

Hi, I am spray coating PCB's with the above mentioned coating. The problem is that as soon as the boards are coated, there are pin holes on the surface that subsequently turn into localized areas of dewet on te PCB (its almost as it the coating is flashing too quickly). I am following the recommended cleaning procedure by Cytec.

The Cytec technical person still maintaines that is contamination of the board, which, after exhaustive review of the cleaning process, i am hesitant to agree. Has anyone faced a similar issue, and what can be some possible solutions??

Any help would be greatly appreciated.

Amol Kane

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PWH

#36845

Conathane CE 1155-35 Conformal Coating Issues | 26 September, 2005

Are you using masking? Conformal coat will de-wet (no pin holes usually, though) due to masking tape adjacent to affected areas if the tape glue chemistry isn't compatible with the conformal coat.

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Amol

#36854

Conathane CE 1155-35 Conformal Coating Issues | 27 September, 2005

I am using masking tape, the 3M high temp blue masking tape. the problem though doesnt seem to be related to the masking tap as i am seeing pin holes and eventual dewets over entire ckt board (its almost as if the board has chickenpox under black light, even on the component surface, as well on PCB surface)

it is a G10 substrate with no solder mask, is this the real problem?

Thanks, Amol

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#36855

Conathane CE 1155-35 Conformal Coating Issues | 27 September, 2005

Amol,

Have you tried to conformal coat a bare board as it comes in from the board shop? If you still have the same results at least you know the problem is not related to your process. If you don't have the problem you need to have a closer look at your cleaning process.

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jimby

#36857

Conathane CE 1155-35 Conformal Coating Issues | 27 September, 2005

surface tension of solder mask material on the board. Need to rough it up prior to board assembly. Use Silica (cabosil) and IPA mixture and rub

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Amol

#36858

Conathane CE 1155-35 Conformal Coating Issues | 27 September, 2005

Thank you patrick and jimb for you suggestions, will try them out and keep you posted.

Amol

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Amol

#36914

Conathane CE 1155-35 Conformal Coating Issues | 30 September, 2005

i tried scrubbing the boards with xylene when they are hot from the bake, the the pockmarking seems to have almost disappeared!

Amol

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