February 15, 2007

Folks, we have some military OEM'S that are switching from Type UR conformal coating to Type AR.  The main reason for the switch is because it is hard to remove Type UR coating in event of a rework, and certain chemicals sold by the coating manufacturers for UR coating removal are highly conductive and have caused problems since the cleaning process did not adequately remove them.  The other reason is we wanted a coating that could be easily removed in event product failed in the field so we could do ATE to quickly find the source of the problem.  Our product is used in a military application but it is contained in a cabinet that is dust tight.  We have some assemblies that are not coated at all with no known problems.

Do any of you folks use Type AR for military product, and if so, what are your experiences using the coating?  I have heard about problems using alcohol for coating removal since it goes where you do not want it to go.  I have also heard that if a spray process is used, it takes 4 or more passes on each side of the board to achieve the minimum J-STD-001 thickness.  At least one source indicated using AR may cause some solder joint reliability issues.

Any info you have would be a help.  Thanks.

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