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Conformal Coating Coupons

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#77410

Conformal Coating Coupons | 17 April, 2017

So I'm starting up a conformal coating process from scratch (again, although it's been about 10 years) and I'm looking for the best option for verifying thickness.

I plan on going the "coupon per setup" route which will encompass both our manual spray as well as automated spray operations.

In the past I've used both metal and glass (lab slides) coupons, but I'm curious if there are any benefits (as well as options) with going with a coupon material that would be closer to the same surface tension as the PCB?

Possibly a masked FR4 coupon? Does anyone have any experience with this? Or possible suppliers?

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#77411

Conformal Coating Coupons | 17 April, 2017

Measurement of Conformal Coating thickness on Printed Circuit Boards [ http://www.defelsko.com/applications/conformal-coating/printed-circuit-boards.htm ]

I receive no benefit from the supplier mentioned above.

IPC-HDBK-830A, 8.11.1 talks to measurement methods:

* Micrometer

* Eddy current

* Ultrasonic

* Optical

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#77421

Conformal Coating Coupons | 18 April, 2017

I appreciate the response, but it doesn't really help answer my question as I've used the methods you've mentioned in the past without much luck.

I'm looking specifically for a source of FR4 coupons, or the like.

Thanks!

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#77422

Conformal Coating Coupons | 18 April, 2017

Can you use a breakaway tab on the board that you're assembling as your coupon?

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#77423

Conformal Coating Coupons | 18 April, 2017

By the time they've reached me/conformal coat they're depaneled (assuming they were panelized at all). Also looked at the tape dot method, but that's a no go as well due to coverage needs.

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Rob

#77427

Conformal Coating Coupons | 19 April, 2017

Hi Phil,

We ask our PCB suppliers for solder samples and any drop out from manufacturing PCBs and use these for profiling, test process runs etc.

If your purchasing team is approachable enough it is worth having the conversation.

I would always want to run a test as close to what I am trying to achieve as possible, and a glass slide has not gone through the same production processes with the same chemicals and residues as the PCB. Nor as I think you mentioned will it have the same surface finish.

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#77433

Conformal Coating Coupons | 19 April, 2017

Thanks for the suggestion Rob, this might work for us in some cases. In most cases though, I'll need multiple coupons per PCB purchase (a coupon per coating "setup").

Currently talking to some PCB suppliers to see if anyone can offer an affordable option, maybe a 2"x2" masked FR4 coupon or something similar. Will report back with results for posterity.

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Rob

#77437

Conformal Coating Coupons | 19 April, 2017

> Thanks for the suggestion Rob, this might work > for us in some cases. In most cases though, I'll > need multiple coupons per PCB purchase (a coupon > per coating "setup"). > > Currently talking to > some PCB suppliers to see if anyone can offer an > affordable option, maybe a 2"x2" masked FR4 > coupon or something similar. Will report back > with results for posterity.

One of our customers uses what you are describing - small FR4 PCBs, but they also fit components to them to better monitor flow and wicking, as in addition to coverage, this is also critical to them.

Else, do you have any obsolete stock you can put through the wash to clean off any residues and use?

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#77544

Conformal Coating Coupons | 5 May, 2017

So I think I've given up a bit on the FR4 coupons due to complexity and having to custom order them every time we'd need a reorder.

In the past I've used aluminum coupons, about the size of a regular business card. Some extensive googling hasn't turned up much yet, maybe I'm using the wrong search terms, not sure.

Anyway, does anyone have a source for something like this? A metal (aluminum or the like) coupon about the size of a business card.

Thanks!

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#77548

Conformal Coating Coupons | 8 May, 2017

For anyone looking this up in the future, I ended up settling on part number "A-2-3.5", an aluminum, smooth finish coupon, 0.025" thick x 2" x 3.5".

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