Earl - There are some applications where DF Mask is the only solution. Like most systems in this business, they can never completely go away. We maintain a DF capability to serve our customers needs. Keep Smiling Dick Desrosiers Director of Manufacturing Harbor Electronics 3021 Kenneth St Santa Clara, CA 95054 408-988-6544 408-406-3729 (cell) [log in to unmask] -----Original Message----- From: pod [SMTP:[log in to unmask]] Sent: Wednesday, September 15, 1999 3:54 AM To: [log in to unmask] Subject: Re: [TN] Dry Film Mask Issues... Good ranting. Now get rid of the DF for ever and find another way to deal with vias. Earl Moon ----- Original Message ----- From: Stephen R. Gregory <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, September 14, 1999 5:20 PM Subject: [TN] Dry Film Mask Issues... > Hey Ya'll, > > Well, judging from the responses I've read on a number of issues about dry > film mask issues, it almost seems that there are more and more boards being > specified with dry film mask on them. > > This seems to be driven by how well dry film tents vias. I recieved many > responses about via fill, and most of them said that it was better to have no > via fill at all, or if you did, it had better be at least 75%...something > that cannot be guaranteed with LPI masks. > > We all know that LPI mask won't tent vias, but then sometimes because of the > mask characteristics, a via may just try to fill during wave and fill less > than 75%. This is the reason (I feel) that hi-rel companies still continue to > specify dry film. They'd rather make sure that none of the vias fill, and not > even worry about what a pain in the butt it is to try and place and solder a > 300-pin plus QFP without solder bridges with a "windowed" dry film. > > Dry film mask is usually at least 1-2 mils higher than the pad surface, so > when I print, I'm getting a extra mil or two over and above the stencil > thickness because the dry film is holding my stencil up that high above the > pads. From now on, when I'm going to specify a stencil thickness for 20-mil > pitch with dry film masks, I'm going to ask for a 4-mil stencil from now on, > and have my stencil vendor "mickey-mouse" or "dogbone" my 50-mil apertures to > give me the additional volume I need for my J-leaded devices and whatnot. > > The stencil I've been using with the most recent assembly has been 6-mil with > a industry standard aperture reduction and I've been getting mucho bridges > (with this stupid dry film). > > In the past, 6-mil stencil thickness with LPI masks have NEVER been a problem > with bridging from my experience... > > Just ranting is all... > > -Steve Gregory- > > ############################################################## > TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional > information. > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or > 847-509-9700 ext.5365 > ############################################################## ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## TechNet Mail List 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 web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################