Conformal coating for circuit board manufacturing

[Anton Gaidos III <anton_gaidos_iii@firepower.com>]

Okay, here is the list of conformal coatings used in printed circuit
design. I'm not sure what Audi uses
but I certainly know what should be used.
AR = Acrylics
UR = Urethanes
ER = Epoxy resins
SR = Silcones
XY = Paraxylenes

AR: General purpose. Moisture resistant. Poor solvent resistance.
Temperture range -65 - +132C. dielectric constants 2.5 to 2.6. Thickness
.002 - .003. Excellent for rework.
UR: Excellent resistance to solvents, moisture and abrassion. Very
difficult to rework. Temperture
range -65 - +125C. Dielectric constants 3.5 to 3.6. Thickness .002 -
.003
ER: Used where excellent electrical and enviromental protection is
rquired and reworkability is not required. Considered impossible to
rework. Dielectric constants 3.5 to 3.6. Thickness .002 - .003
SR: Good electrical properties and intended for high temperture
applications. Difficult to rework.
Temperture range is 200C. Dielectric constants 2.5 to 2.6. Thickness
.002 - .003
XY: Uniquely suited for fine pitch surface mount parts (You won't be
finding this on your Audi circuit boards!
Anton J. Gaidos, III
PC Design
Motorola Computer Group
"The fortunate man knows how much he can safely leave to chance"