Rick, It is likely that the fabricator does not have the equipment necessary to provide a reliable dam between the surface mount pads. Assuming that he is using an LPI there are a lot of process points that would or could make this a difficult proposition. Remembering our first attempts at damming (and damning) the tighter pitched devices it was really hit and miss. We have found that there are some newer masks that make damming easier. Lea Ronal OPSR5900 and Vantico (formerly Ciba Geigy) 77MA or 77MA-1 make processing these tighter geometries easier. Don't know if this helps but I thought I'd put my two cents worth in... Pete Menuez --- Rick Thompson <[log in to unmask]> wrote: > Hi, > > We have a customer who has a board with 20 mil pitch > QFP's on it. The > actual pad size is 11.8 mils wide and there is a 2 > mil gap in the soldermask > around the pads leaving 4.2 mils of solder mask > between the pads. The board > house that is building these says they can't > maintain the soldermask between > the pads and is asking for a window around all leads > in the group or a > tightening of the soldermask openings around the > pads. Before I go to our > customer with this, I'd like to get some feedback on > whether or not this is > unreasonable? Are these dimensions acheivable or > should I ask our customer > for a deviation? > > Thanks in advance, > > > Rick Thompson > Ventura Electronics Assembly > 2665A Park Center Dr. > Simi Valley, CA 93065 > > +1 (805) 584-9858 voice > +1 (805) 584-1529 fax > [log in to unmask] > > ############################################################## > 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 Keach Sasamori at > [log in to unmask] or > 847-509-9700 ext.5315 > ############################################################## __________________________________________________ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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 Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################