For my guess I'll go with either too thick, or contamination on the panel making it try to dewet.
Questions: is this a new problem on a product you have been successfully coating until now? Have you measured the thickness to ensure it is within normal range?
Suggestion: Could you do two thinner coats and let it flash off a bit between coats?
regards,
Graham Collins
Halifax Production Engineering
L-3 communications Electronic Systems
(902) 873-2000 ext. 6215
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Wednesday, May 05, 2010 3:59 PM
To: [log in to unmask]
Subject: [TN] Wrinkling of conformal coating
Dear Technos,
Back to orange peeling, this time concerning conformal coating, please see http://ipc-technet.groupsite.com/galleries/photo/124230
The coating is applied with an Asymtek Century machine and is a Conap 1170 acrylic.
ˇ The board is left curing in ambient temperature, no acceleration. Starting with an even coating, in about 20-30 minutes the liquid seems to move towards a certain area (no rippling at this moment). After another 10-15 minutes the rippling effect sets in.
ˇ We thought that due to the almost 2 minutes lag between the coating of the first and last image, the drying of the coating layer is not even and the one side curing first pulls on the liquid at the other end. So we've cut the panel in 2, accelerated the machine, the problem is still there.
ˇ The boards are laid as flat as possible, maybe not perfectly horizontal, but not worse than others with the same coating, that do not show any issue
ˇ Just to make it more difficult: grabbed a non-populated panel from the stores, coated it, placed on the same flat surface, and guess what: no issues.
The PCB has Taiyo PSR 4000 MP soldermask.
So I would need your guidance in clarifying where is this coming from and how to fix it.
Thank you,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] <mailto:[log in to unmask]>
W | www.digico.cc <http://www.digico.cc/>
N'imprimer que si nécessaire - Print only if you must
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
