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Conformal Coating Issues

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#66287

Conformal Coating Issues | 9 May, 2012

I had send my coating board to the test lab for adhesion coating test. 3 times send, the result 3times fail. The coating chemical use is Humiseal 1B31. The process is clean the boards at washing process use the Vigon A200 saponifier mix with DI water, Test the cleanlines of teh boards with Omega meter, Result pass, then kept the board at baking for 6 hour with temp 85 degC, finish that then coating the boards use the PVA coating machine with humiseal 1B31 coating material. cure the boards with PVA curing machine. Upon finish that process the I send teh boards to the 3rd part test lab on the adhesion coating test. the result come out from the test labs is all my boards was fail and the coating was peel off.

Any one knowing what's teh problem to my process ? and how to solve it ?

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#66310

Conformal Coating Issues | 10 May, 2012

It's good that you're consistent. Troubleshooting an inconsistent problem is a female dog.

Here's the answer you're looking to find: Some where in the chain: solder resist => fluxer => cleaning (or lack there of) => conformal coating: there is a lack of compatibility. You need to figure-out which is the bad boy. Maybe a good guess is to conformal coat boards at each step in the process and then have them tested.

Don't delude yourself about the absoluteness of the results of your Omega meter testing. Omega meters are process control tools. They indicate whether you're on track or not. Being on track is based upon the guess that someone made when he/she setup the machine.

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#66363

Conformal Coating Issues | 17 May, 2012

Hi Dave,

Thanks on yoru prompt reply,

Can help to share whethere you had knowledge about this issues ?since I had a hot topic on this issues ? is my cleaning is not clean or is the saponifier chemical uyse is not compatable to the humiseal coating proces or any other opportunity that make tset was fail ?

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#66366

Conformal Coating Issues | 18 May, 2012

We us a lot of 1B31 it could be one of the most common coatings out there. We do not clean the boards and do not have an issue. I would check the solder mask compatibly. I would also see how the 3rd party company is testing the boards what criteria or the using. My understand of that product was that it sat on the board and encapsulated it and that it did not etch its way into the board. Another thought make sure you are thinning it properly. You can contact humiseal they are usually helpful.

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#66368

Conformal Coating Issues | 18 May, 2012

Umar

Chapter 7 of IPC-HDBK-830, Guidelines for Design, Selection and Application of Conformal Coatings deals with compatibility of the different materials in the chain.

Have you: * Tested your bare boards at incoming for cleanliness with your OmegaMeter? * Calibrated your OmegaMeter? * Tried a different flux? * Determined what is the difference between the adhesion test that was run by the outside lab and the test that you run prior to sending it to the lab?

As Ka stated above, most of us don't have the capability to perform laboratory testing in-house. We rely on independent testing labs. Here are a few labs that would be good starting points: * Robisan Laboratory; 6502 East 21 St, Indianapolis, IN 46219; 317-353-6249 F357-1270 Susan Mansilla, Technical Director robisan1@aol.com * Trace Laboratories - East; 5 North Park Dr, Hunt Valley, MD 21030; 410-584-9099 F9117 tracelab@connext.net http://www.tracelabs.com * STI, 261 Palmer Road Madison, AL stielectronicsinc.com Mark McMeen * UIC, Martin K. Anselm, Ph.D., Manager, Analytical & Failure Analysis Services 607-779-5077 Anselm@uic.com

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#66371

Conformal Coating Issues | 18 May, 2012

I'll chime in here as well. If you have adhesion problems, 90% of the time it's contamination on the substrate (soldermask, flux residues, cleaner residues, etc.). Like Dave said, omega meter is a test for gross cleanliness, and it's OK for process control, but not for surface contamination testing. Ideally you need ion chromatography, this will tell you the levels of specific ionis species. Most if not all of the labs Dave listed have IC capabilities. Also, what test is used for adhesion? Tape pull test? Bottom line is surface contamination from somewhere, just have to figure out where.

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#66474

Conformal Coating Issues | 31 May, 2012

I use Trace and certainly recommend them. I actually just had this test done last week. Adhesion test per ASTM-3359 Method B. We use Humiseal 1B73, which is similar to what you use.

Is your soldermask "active" enough for this coating? I believe 38 dynes is the recommended threshold.

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#66475

Conformal Coating Issues | 31 May, 2012

I use Trace Labs and certainly recommend them.

I actually just had this test done last week. Adhesion test per ASTM-3359 Method B. We also use Humiseal 1B73, which is similar to the 1B31 you use.

Is your soldermask "active" enough for this coating? I believe 38 dynes is the recommended threshold.

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#66482

Conformal Coating Issues | 1 June, 2012

Hi Norman...

Thansk on yoru input, actually my adhesion test conduct is after pass of IC test. MY IC Test is shown a good result but when go into teh Test adhesion coating then during peel off test my board was failed.

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#66487

Conformal Coating Issues | 1 June, 2012

Neither the Omega meter nor the IC are officially "destructive" tests, but everywhere I worked we treated them that way. The boards were scrapped after the test. The Omega meter can be tested at elevated temps, but the IC sample is extracted at elevated temps (80°C for 1 hour exposure). Bake out would help after the test, but the solvent exposure may have changed things. Omega meter and IC both are testing for ionic compounds/species that are on the board. However, they cannot detect non-ionics. It's possible that something is coming out of the board/compnoents/residues during the test that neither ionic test is picking up, but interferes with adhesion there after. Ionics are a concern because of corrosion or dendritic growth over time, but again, contamination will affect adhesion (be it ionic or not).

Also, the 38 dyne surface energy is a good target (higher surface energy, better bonding), it doesn't necessarily mean you will get good bonding. An application guy from Dow told us years ago that they had tested 2 different materials with the same surface energy, got good bonding to one, but not the other. Not only is mechanical bonding going on, there is also chemical bonding as well. That's why some materials bond well to substrate A, but not B.

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Lou

#66546

Conformal Coating Issues | 8 June, 2012

Umar, it may never be solved. Some coatings just do not stick to some substrates. Have you tried using a different coating? Even changing to 1B31S may be enough. Or 1B73 acrylic. Also, look into Nexus3C.com.

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Plasma Prior to Conformal Coating

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