All,
I get the digest version, so I'm responding after reading a number of messages regarding via sizes. The answer to Brad's original question is yes, via in pad is the recommended connection for fine pitched BGA. Believe it or not, the via size is going to be dictated by the pad size more than by the solder thieving problem. The last one I did had a 6mil hole. We have used 13 mil holes as the largest, and that is the info we have been putting into app notes for our devices. You will also see this with QFN devices that have the large pad used to stabilize the package, as well as adding thermal relief. This tiny pad on devices, such as op amps, can be tied through vias to ground planes to draw off heat from the device. This is one of the places I have used the 13 mil holes. So is it recommended?..yes,..and does it work?....yes. If it really bothers you, plug the holes with silver or epoxy. And by the way, there is lead-free BGA that works well with no-clean flux..or so I'm told by Kester. Dell, Nokia and Motorola are using LF processes, and many of the parts they are using are BGA. One thing to consider is LF parts are going to be the norm in the not too distant future. There may be problems procuring leaded parts so keep this in mind. If you would like to discuss this further, I am willing to do this, just contact me directly. Bob Benjamin DAP - Texas Instruments Tucson, AZ [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]
