Are you 100% cured prior to temperature cycling?

Solvent based systems will outgass for a week or so prior to full cure,
especially with dipped panels. If you temperature cycle begins prior to
full cure, you can outgas or freeze solvent to cause this problem.

Some 100% solids systems may not be fully cured for a few days after
coating. The uncured material can react as above.

Mechanical action from attachment can also crack coating.

Moisture outgassing from the board can also bubble coating.

As an aside, why must the side be coated. The side does not contain any
conductive or corrodable surfaces.


As an aside

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
-------------
Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 8/31/98 10:29 PM:
To: Aric Parr@01635@Lectron_RH,
EatonWHQ@CorpMail@WHQCleveOH[C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG]

The test engineer came back to us to complain that bubbles are found
along the edge of the power modules after going through the temperature
cycling tests. This problems are found on both coated boards. The power
modules are mounted completely flushed onto the board and subject to
conformal coating using the diping method. The coated board undergo QC
to ensure all components are completely coated, inlcuding the edges
around the modules.

What could be the problem?

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section
for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################