Steve, I use round pads to decrease pad size (increase circuit density). A side benefit seems to be less chance of skew, I don't have numbers on tombstoning/drawbridging, but product hasn't yelled. I have also been tinkering with the idea of other geometries just haven't come across the right application yet. Dan ----- Original Message ----- From: [log in to unmask] To: [log in to unmask] Sent: Tuesday, April 09, 2002 8:12 PM Subject: Re: [TN] 0402 tombstone problem I just heard something not too long ago, that round pads for 0402's are the way to go. Never heard of that before, but just recently received a board for quote that uses round pads for the 0402 components...anybody else ever heard of this? Guess I'll find out how it works inna little while, while pondering why a round pad would work better than a square pad.... -Steve Gregory- Edward, When we do everything correct on 0402 and 0201 and still have components standing-up, we often look to the component terminations and find poor plating. Good luck Dave Fish ----- Original Message ----- From: "Edward S. Wheeler" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, April 09, 2002 10:59 AM Subject: [TN] 0402 tombstone problem > Hi folks, we are running a new board with 0402 parts on it. It seems that > we are having a tombstone problem as well as a problem with parts not > staying centered on the pads. We are currently using 20 mil square pads on > the board, with 20 mils of spacing between them. Our stencil is 6 mils > thick, laser cut and electro polished. The trapezoidal walled apertures are > slightly reduced, 17 mils square, and centered on the pads. It appears the > chip shooter is placing the parts perfectly. We are using eutectic solder > paste with an OA flux, and reflowing the parts using the recommended profile. > > Are there any suggestions any of you might have concerning this size of a > part? Is there a better stencil design, reflow profile, or pad design that > could help us out? I would appreciate any suggestions. > > Thanks. > > Ed