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Conformal coating IS-410 boards

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Cmiller

#49213

Conformal coating IS-410 boards | 21 April, 2007

Has anyone experienced a problem with conformal coating adhesion to IS-410 boards?

We are having problems with one suppliers boards. IS-410 boards from other suppliers are fine and all FR-4 boards that I have looked at are fine. We are using Conap 1170 coating. No-clean process and we batch wash the boards using Bioact EC-ultra. We ran a bare panel right out of the package on only one side and the coating was fine. I put the same board through the reflow oven and coated the other side and the adhsion was poor. I will run some more tests with boards in that particular oven today to asses the possibility that the problem may be the oven itself. On the test board I did, I only ran it on a FR-4 profile so I do not believe the issue is with the oven profile. The rep for Conap thinks that there is photo-resist leaching through the soldermask when the boards are reflowed. Has anyone ever heard of this or had a similar problem? Is there any way to remove it? I have used acetone and it did make a noticable diffenence but the boards in question are still much inferior to other boards we are coating. I would love to send all the boards back but of course they are already assembled and our customer is in dire need of them.

I am using a piece of standard masking tape to perform a pull test on the coating. I am cutting small squares in the coating with a razor blade. On most of our boards the coating will not peel at all. On the boards in question, once there is a cut in the coating, it peels right up and not in flakes, it peels up in a sheet.

Any help would be greatly appreciated.

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Cmiller

#49214

Conformal coating IS-410 boards | 21 April, 2007

I coated three other bare boards on one side this morning from two different suppliers. Two of them had exceptional adhesion and one was so-so. I ran them through the reflow oven, coated them and got the same results on the other side, so it does not appear that the oven is casuing a problem but certainly in the case of the problem boards it does appear to be caused by some type of reaction to relow temperatures.

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Cmiller

#49230

Conformal coating IS-410 boards | 23 April, 2007

It appears that the two different boards we are having issues with are the only imersion silver boards that we process. Anyone have simililar issues with imersion silver?

Is Dave F. on vacation? I would be willing to consider input from moon man at this point.

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#49235

Conformal coating IS-410 boards | 23 April, 2007

Your low residue flux may not be compatible with the soldermask

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Brett

#49236

Conformal coating IS-410 boards | 23 April, 2007

Oh, we thought this was just for Dave F. Sorry.

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Cmiller

#49237

Conformal coating IS-410 boards | 23 April, 2007

Dave, we have the same issue running a new bare board through the oven with no paste. If there is an imcompatibility with our flux would it still manifest itself when there is not flux? Im sure there is some residual flux in the oven all the time. We are using a Alpha metals paste, I do not recall the mask at this moment. Is there a database somewhere of known incompatibilities? I will see if we have some boards with the same mask that are not imersion silver and test those. Thanks!

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#49238

Conformal coating IS-410 boards | 23 April, 2007

Sorry to interfere with Dave F, but perhaps your IAg finishes have issues with process residues from the boardhouse.

What is the base material of your ConAP conformal coating - acrylic, silicone, polyurethane?

We do CC (acrylic) and IAg and never had issues.

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Cmiller

#49239

Conformal coating IS-410 boards | 23 April, 2007

Acrylic.

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#49246

Conformal coating IS-410 boards | 23 April, 2007

Well then, maybe it's an incompatibilty between the soldermask and the coating, possibly due to undercuring of the soldermask.

Thoughts are: * Some suppliers provide their thoughts on the compatibility of their product with other suppliers. For instance: Enthone DSR Solder mask and adhesion results with different coatings. http://www.enthone-omi.com/electronics/pdf/Imup7.pdf

* As a word of caution here, we all appreciate that material suppliers might be motivated by different factors than assemblers. There is no guarantee that material A works with material B in a manufacturing process. That is why you must verify a material change on actual product. * A quick scan SM-840C - Qualification & Performance Of Permanent Solder Mask appears to add nothing * Taking a different angle, B.Ritchie on coating over existing process residues. http://www.loctite.com/int_henkel/loctite/binarydata/pdf/elec_Conformal_Coating_Over_Existing_Process_Residues.pdf

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Ricoculous

#49248

Conformal coating IS-410 boards | 23 April, 2007

brett shame on you

pls. leave the experts of this forum free to answer the questions.

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