Kelley, What was wrong with just "simple Dry film tenting"?? And how thick was the product after application? R. Kubes Honeywell DAS (Albq) > ---------- > From: Kelly M. Schriver[SMTP:[log in to unmask]] > Sent: Thursday, October 01, 1998 7:54 AM > To: [log in to unmask] > Subject: [TN] LPI Filled Vias ? > > Good morning TechNet!!!!! > > Here's a challenge for the board fabrication guys and gals: > > Most of our board designs go into severe environment service. For the > past > eight ten years or so, we have been tenting vias with thin dry film solder > mask disks, followed by an LPI overcoat of the entire board (both sides). > The > purpose of all of this is to seal up all exposed conductive surfaces, > particularly those under component bodies, prior to assembly. This leaves > only the termination pads and plated thru holes which receive thru hole > leads > exposed. This has worked out to be a very successful process. > > We arrived at this combined mask application after having tried a number > of > different via fill approaches and just simple dry film tenting. None of > these > were fully satisfactory (bumps, open voids, ruptures, incomplete fill, not > process durable, too costly, not repeatible, etc.). The dry film plus LPI > also turned out to be the only approach that ALL of our board vendors > could > handle reliably. > > Now I am revisiting the process. We have run a few samples using LPI as a > via > plug as well as the overall solder mask. These have turned out to be very > durable in our assembly process. Microsections indicate small voids, less > than 50% of the via volume, which are not a problem to this application. > Board thicknesses range from .040" to .080". Finished vias range from > .008" > to .016" dia. (This covers multiple designs.) > > Now, here's the big question: Could you produce class 2 and 3 boards > with > LPI plugged vias which will not rupture or expose metal during my > soldering > and cleaning processes? (Assume that worst case will not exceed four > solder > and cleaning cycles. Cleaning agents may include DI water, long chain > alcohols or citric acids) Total mask thickness buildup over pads should > not > exceed .0015", in order to not interfere with our stencils. > > For anyone who is actively performing this process or assembling CCAs > using > this process - I would greatly appreciate your inputs. > > Regards - Kelly > > ################################################################ > 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 ################################################################