I've done both manual "dogboning" of via's to the BGA pad as well as just let it do its thing...
With BGA's, the denser and more rows of balls on the BGA the more layers typically required... I really don't suggest solder mask defined pads... Altera and Intel both have written tech sheets about this. Immersion gold surfacing seem more prone to embrittlement issues even when the electroless process is done correctly...and most CM's seem to like imersion gold for fine BGA's. And with metal defined pads, make sure your solder mask is tight enough to avoid exposing traces that go between balls/pads on the top layer. Had many issues with fabs' near their capability misregistering the mask and exposing copper traces under the BGA - dead shorts during reflow were common. In a message dated 1/8/2007 7:52:57 PM Eastern Standard Time, [EMAIL PROTECTED] writes: > > --- Dennis Saputelli <[EMAIL PROTECTED]> wrote: > > > > > i assume you meant '99SE' ? > > > Yes I did mean that as matter of fact. > > > the autorouter for it's time (which was not new even at that time) > > actually wasn't too bad, but it certainly was not made to do BGAs > > it did do a decent job at lined up rows of random wired DIPS :) > > > Well I have wired lots of dips with it, but it had quite a few anoying > bugs in it still. In any case I'm looking at surface mount devices > instead. So how does one do a BGA since it's only contact technically > is the top or bottom layer. Does one employ vias near the pads or > something? > > > i wouldn't get my hopes up about autorouting that thing > > > A 144 pin LFBGA is too much for it? > > > to do a solder mask opening smaller than the pad use a negative > > expansion > > > That is definately helpful. > > > my brain is wired in mils so... > > for a 40 mil pad with a 30 mil opening use > > solder mask expansion of -5 mils > > > I'm so use to converting between the two I almost do it in my head > these days. So that would be the override designation for the > soldermask? (is this defined on the part or in the Design Rules... 99SE > is a bit of a maze it looks like someone kept adding features to > something that started small). > > > what is driving the 'solder mask defined' ? > > i have read both pros and cons about that but everyone i know does > > not do it > > > You mean solder mask over pad instead of mask about pad? It was > mentioned in the package JTAG information so I asked. > > > .125mm is 4.9 mils > > 5 mil trace/space is almost ordinary these days > > > > for BGAs depending on the pitch we sometimes need to go to 4mil trace > > > > 4mil space AKA 4/4 > > > Right FBGA is 0.8 mm which is 31.4 mils. So it's not a big deal to > have such small traces anymore then? > > Stephen > > Stephen R. Phillips was here > Please be advised what was said may be absolutely wrong, and hereby this > disclaimer follows. I reserve the right to be wrong and admit it in front of > the entire world. > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > > ____________________________________________________________ > 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]
