Gary, Thanks for this information, sounds very valuable. Vasile On 10/1/08, gacrowell@micron.com wrote: > Coincidently, the board house rep was in town today with a new DFM > manual. We've been doing the 0.15mm drill on 0.5mm pitch BGA's, > via-in-pad, filled and plated flat&flush both sides on 40 mil thick > boards. We require flat&flush on both sides because we do automated > micro-probing on the side opposite the mounted BGA. I was surprised > that their manual says those drills can go to 150 mil thick, an aspect > of 25:1. I have no idea how they get those things plated. The rep > claims those are reliable for production boards. We've had good luck > with them on our test fixture boards, but have only done them at the 40 > mil thickness on a few hundred total quantity boards > > What's more, they've just got new drilling machines that can now do, as > part of their standard rules, 0.10mm mechanical drills on 0.4mm pitch > BGA pads on boards up to 62 mils thick. I'm sure I'll have some .4 > pitch parts in the next few months, and will be eager to give that a > try. They claim to be more economical than laser vias. The advantage > for our application is that I can go all the way through the board in a > single via without having to stairstep or stack micro vias. > > Their 'immerging technology' is the same drills on 72mil and 200mil > boards, respectively. 34:1 AR. > > Obviously to do this they have improved positional accuracy - I've never > seen a breakout on a pad. I wouldn't doubt that they are beyond IPC > standards - doesn't matter for our test fixture boards. Wouldn't be the > first time that IPC needed to catch up though. > > The board house we're working with is Gorilla Circuits in San Jose, but > I doubt that they're unique. > > Gary > > > -----Original Message----- > > From: piclist-bounces@mit.edu > > [mailto:piclist-bounces@mit.edu] On Behalf Of Vasile Surducan > > Sent: Monday, September 29, 2008 12:18 PM > > To: Microcontroller discussion list - Public. > > Subject: Re: [EE] BGA board processes > > > > Who is manufacturing for you 0.15mm drill (I gues you're talking about > > mechanical drill not laser drilled nor microvias) with 0.35mm outer > > ring on 40mil thick board ? > > Looks to me is not an IPC standard. > > thx, > > Vasile > > > > On 9/25/08, gacrowell@micron.com wrote: > > > FWIW I've been using 0.2mm (8mil) drilled vias all the time > > on 0.8 pitch > > > BGA's - dogbone from the pads to the offset encroached-mask > > vias. On > > > 0.5 pitch I have used a filled 0.35mm pad via-in-pad, 0.15mm drill, > > > plated flat & flush. Needs .05mm traces to get out. But > > those are on > > > 40mil thick boards. 6mil drills might be a problem on > > thicker. And, I > > > don't know the cost trade-off between microvias and filled > > vias. Also, > > > I am not using either of these methods on > > production-quantity boards. > > > But I can get them fabbed that way, routinely, no problem. > > It's worth > > > discussing with your fabricator/assembler as an alternative to > > > microvias. > > > > > > Gary Crowell, CID+ > > > Micron Technology > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist