Hi Andrew

I suggest that you have a suitable open soldered pad on each board, measure it with a micrometer before and after costing. The wet comb test really isn’t suitable, it was intended for paints.

I recommend that you get a copy of IPC-CC-830 Conformal Coating Handbook.

Keep in mind that coatings have 3 curing stages:
1	Tack free
2	Dry to handling
3	Fully cured

As it seems you are new to coating, what was the reason behind adopting coating? I ask only because, in many cases, people use a coating to hide a problem, but coatings seal in as well as out.

Graham Naisbitt
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P: +44 12 5252 1500

IPC
Vice Chair 5-30 Cleaning & Coating
Chair 5-32b - SIR & ECM
Vice Chair 5-32e - CAF

GEN3 - Chairman & CEO

> On 14 Aug 2020, at 13:02, Andy H <[log in to unmask]> wrote:
> 
> Hi all,
> 
> I wonder if anyone has any experience or resources in calculating the difference between wet and cured conformal coat?
> 
> Essentially my company is introducing a process control where we use a comb to check the thickness of con-coat on a production 1st off, then when it has cured we use an eddy tester to check the cured thickness.
> Ultimately what we want is a graph or a table, for operators, that indicates if wet comb test = X micrometers then cured will = Y micrometers, we hope to be able to achieve a 'right first time' process.
> 
> We are currently using a 50:50 ratio of coat to thinner but we are also looking at water based coating too.
> 
> Does such graph or table already exist? If not can anyone advise what variables need to be considered into our research?