Rick: We ran a fairly in depth study with Kester, looking at the compatibility of their no-clean fluxes and our non-cleaned PCA's with conformal coating(CC). The test used Kester's 256 no-clean solderpaste and the 245 no-clean core solder. We looked at them individually and also combined on the same board. This was done for both acrylic and urethane CC. We did not test Humiseal's 1B31 LOC acrylic. The test consisted of SIR and adhesion. SIR was done on B25 coupons, 65C/85%RH, 168 hours, readings were taken at 1,4,7 days under test conditions and recovery after removal from the chamber. We did not see any significant difference between controls, fluxed/coated and fluxed uncoated boards. They were all within one order of magnitude under test conditions. Visual inspection after SIR testing showed some signs of blistering/vesication on the boards with 256/245 with urethane coating but not on the acrylic. However there was no drop off in SIR on the urethane boards. The adhesion testing was done per ASTM Method D 3359-92a. They were all acceptable however the combined 256 and 245 residues showed the lowest level of adhesion. The 245 alone was better. The acrylic had better adhesion than the urethane. Conclusion: If you are applying the acrylic CC over just the 245 no-clean you "maybe" OK. When you start mixing different flux residues with other conformal coating chemistries you can create a chemical stew that's not compatible. Obviously you also need to consider incoming board cleanliness, contamination added by your handling and processing, adhesive properties of the soldermask, electrical requirements of the board, service life and conditions of the product, etc etc. So you will need to do some testing yourself to qualify the materials and performance. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: Rick Thompson [mailto:[log in to unmask]] Sent: Tuesday, September 24, 2002 10:50 AM To: [log in to unmask] Subject: [TN] Humiseal 1B31 LOC Compatible with No-Clean? Hi, I'm wondering if anyone has experience using Humiseal 1B31 LOC Acrylic Coating over low residue no-clean flux? Specifically, over Kester 245 no-clean used in cored wire? I'm looking for any data that would support use of this coating over the flux residue, adhesion, long-term reliability, etc. If anyone has information they'd care to share it would be greatly appreciated. Thanks in advance, Rick Thompson Sr. SMT Process Engineer SMTEK International, Inc. +1 (805) 532-2800 [log in to unmask] ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------