Actually I'm also looking for solder mask with high strength and high temperature. For example, when I repair an open BGA trace. I would need to cover up the repair area with a type of solder mask or epoxy that can withstand high temperature. Another criteria is that the epoxy should be able to be fast cured as I can't leave the board lying around for 3 days in order to reach full cure. Any advice? Rgds, JinSee -----Original Message----- From: Dennis Fritz [mailto:[log in to unmask]] Sent: Wednesday, April 04, 2001 12:52 PM To: [log in to unmask] Subject: Re: [TN] Solder mask for touch up Good idea to use more of the original solder mask for touch up - but a couple of further pointers to help make your life easier. 1. If the original mask is LPI - it is cured with both a photo exposure and a bake. Doubt an assembly shop has UV light of that intensity - so really watch the bake - don't short cut that. The bake at touch-up has to cure as much as combined expose and bake at original fab. Also, be sure this extra bake is not damaging any surface finish conditions - OSP, immersion tin or silver, or forming extra copper/tin intermetallic from the tin/lead solder of a HASL board. If original mask was dry film - you obviously have to use a different liquid mask for touch up. 2. Lots of mask formulations come as two part - resin and catalyst. You have to get both parts from your board fab, and then you have a mixed mask pot life of a few hours. Mix no more than you will use quickly in the touch-up operation. Likewise, most masks are carried in solvent. Some solvent may evaporate from your mixed resin/catalyst, so get some extra solvent from your fab shop. Or, you may want to make a more dilute mask formulation to be able to brush-on touch up areas more easily. 3. If you don't like these complications, you might consider touching up with a one part thermal cure mask from the old days. That stuff is pretty simple. Denny Fritz MacDermid, Inc. ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------- -----