We use a CMI CGX-B.  It's an eddy current device, I believe.  The catch is
that you have to measure over bare copper and the unit has to be calibrated
on the same type of subtrate (uncoated ) as you will measure the coating.
Our process is conveyorized (horizontal)with a programmed robot sprayer.
What I've had done is to have FR-4 cut up into 1/2 X 3/4" squares and have
the operator place a square in an area that will be coated. After the drying
oven, the coating on the square is measured using the CMI.  The area where
the  test square sat is touched up.  We have some  designs that have bare
copper areas left on the panel border for measuring and we've also used
copper adhesive tape.  Again, the key is to calibrate on an identical
substrate.  A certified thickness of mylar is used for calibration.  I
believe a beta back-scatter device would also be capable.

George Carroll
Process Engineer
Siemens Energy and Automation
Johnson City, TN

[log in to unmask]

-----Original Message-----
From: Bissonnette, Jean-Francois [mailto:[log in to unmask]]
Sent: Thursday, March 14, 2002 9:58 AM
To: [log in to unmask]
Subject: [TN] Coating thickness


Hi All,

Does anyone now of a technique or system to check conformal coating
thickness after it's dry on production units?  We have a positector to 
measure paint thickness on our enclosures but they're not design to
work on materials like PCB.

Jean-François Bissonnette
Vérificateur, Contrôle de la Qualité
Électronique
Produits et Procédés
Vapor Rail Inc.
10655 Henri-Bourassa O.
St-Laurent, Qc
H4S 1A1

(514) 335-4200 x2021
(514) 335-4231 fax

 <<Bissonnette, Jean-Francois.vcf>> 


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