Many people use a flat coupon, without components, to gauge the thickness they are putting down, using a micrometer, eddy current meter or similar. This is only an approximation and can be used for repeatability / process control. We perform this as standard before each coating job.

It is actually very difficult to measure the thickness of coating on a board due to the effects of the various contours and capillary forces at work. People have used optical inspection equipment, but I suspect this is overkill and beyond the reach of most.

As for the thickness issue, if you put down less than the stated minimum, you have to ask yourself whether your coating operation makes any sense - you have too little coating to afford any real protection, so what have you gained? If you have too great a thickness, you run the risk of damaging component integrity, due to mechanical stresses and strains, particularly during heating/cooling cycles.

IMHO it is difficult to exceed the stated thickness, except with solventless 100% solids materials and some selective coating machines. On a flat coupon, aim to be right in the middle of the spec, and you probably won't exceed the max thickness in a run or the minimum in a "bare" spot caused by capillary.

Please note that Concoat has recently acquired the former Multicore SPCID business. For more information, please visit our new web site www.concoatsystems.com

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Camberley, Surrey, GU16 7PH

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