Brad, Since years we are using tented vias with drill (not final) sizes of 12mil and smaller. Just lately we had the issue of tholder thieving on a board below a 1mm BGA with vias between the balls. The manufacturer decided to have a relatively large solder mask opening. He obviously needed this large opening since the mask was displaced such that the wall of a via not exactly centered between BGA balls was exposed on the side of the connecting BGA pad resulting in no solder mask bridge between partially tented via and connecting pad. This already was enough to cause solder thieving! My experience is the opposite of what these articles state.
Regards, Emanuel --- MPL AG www.mpl.ch Emanuel Zimmermann [EMAIL PROTECTED] Manager R&D Phone: +41 56 483'34'34 Taefernstrasse 20 Fax: +41 56 493'30'20 CH-5405 Daettwil --- [EMAIL PROTECTED] wrote on 08.12.2005 01:31:32: > Okay a lot of you out there have a lot more experience with BGAs and > micro sized devices than I have, I wanted to see if any of you have > heard of this issue. I know that I have only heard the opposite until today. > > What I was told today is that Linear Technology and some other > Semi technical articles are stating that for small vias (13mils or > smaller), one does not have to tent vias on BGAs or worry about vias > in pads because the hole is so small that it will not thieve solder > from the pad/joint. Now this goes against all I have ever heard > because all the talk of BGAs has always concerned themselves with > solder thieving from the pads and tenting vias/dogbones to stop > this. Now my thinking is that maybe that is old school and only an > issue on the larger/older BGAs where one may be using larger vias. > But with some of these new microBGAs you would be very hard pressed > to use anything larger than a 13 mil finished via hole. And with a > hole this small it is smaller than most solder paste balls and the > surface tension of the solder may restrict solder flowing into the > hole when it is reflowed. > > Comments? Anyone confirm or refute this claim? > > Sincerely, > Brad Velander > Senior PCB Designer > Northern Airborne Technology > #14 - 1925 Kirschner Road, > Kelowna, BC, V1Y 4N7. > tel (250) 763-2329 ext. 225 > fax (250) 762-3374 > > > > > ____________________________________________________________ > You are subscribed to the PEDA discussion forum > > To Post messages: > mailto:[email protected] > > Unsubscribe and Other Options: > http://techservinc.com/mailman/listinfo/peda_techservinc.com > > Browse or Search Old Archives (2001-2004): > http://www.mail-archive.com/[email protected] > > Browse or Search Current Archives (2004-Current): > http://www.mail-archive.com/[email protected] > > ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
