Bob,

Sorry to dissapoint you, but dip coating never puts on an even coating on
PCBs.

The coating can puddle on the "top" side of all components as the PCB is
removed. This then can drip to the "bottom" of the part and hang there
during cure.

The last edge to exit the tank is usually thicker than the top edge. The
coating can just drip down to the bottom before it cures.

Varying the withdrawal rate, coating viscosity, cure rate, exit direction,
PCB orientation and panel cleanliness can all affect the above effects.

Do your darker areas fall into the above categories?

ARIC PARR
Sr. Manufacturing Engineer
Eaton Corp
1400 S. Livernois
P. O. Box 5020
Rochester Hills, Mi 48308-5020
[log in to unmask]
248 608 7780
Fax: 248 656 2242
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Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 3/5/99 11:41 AM:
To: Aric Parr@01635@Lectron_RH,
EatonWHQ@CorpMail@WHQCleveOH[C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG],
Luis Arevalo@Automotive Eng@AACOCarolStrmIL

Good Morning,

    I am the QC Manager of Endicott Research Group, Inc in N.Y. I have some
questions regarding the coating requirements located in the IPC610A Rev B
(amendment 1 included). We are using a acrylic polymar coating with
flourescent tracer materials. The question I have is that when we view the
material under a black light we notice that some areas are heavier than
others. The units are being dipped into a pan of material. I have reduced
the amount of thinner used with the acrylic and the coating appears more
even but heavier. Does the tracer have to be even? I would think being
dipped that the consistency is the same. We have stirred the material to
assure that the thinner wasn't seperated from the acrylic. Any input you
can give is appreciated.

Thanking you,

Bob Arciolla

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