Hi John! We have several designs using 0402 capacitors and resistors in production. Although we haven't look at very many non-square/rectangular pad configurations, our testing results show that EQUAL pad area is a dominate factor in avoiding tombstoning. Some test runs illustrated that just the use of soldermask (over copper) to define the reflowable area of the component pads kept the solder surface tension forces in line to avoid tombstoning. Good Luck. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: ASSY: Are U Square or Round or Oval Author: [log in to unmask] at ccmgw1 Date: 6/10/97 2:17 PM Address, There's been a lot of discussion lately on Tantalum caps. I think all of us have had one or more problems with these types of caps. I like to throw another out on the table. We're planning on minimizing the quantities of 0603 and 0805 tantalum caps that are used on our PCMCIA. We've tried several footprints to minimize the amount of tombstoning to now avail (all lands being square). NOTE: The tombstoning is problematic, but no show stopper. In our new design, we will be using ceramic 0402's quite extensively. To better help the assembly process we're discussing the recommended footprint. I've recommend we continue using a SQUARE/RECTANGLE footprint, since ceramic caps are symetrical, whereas tantalums are not. Our designers are considering using OVAL footprints to minimize tombstoning. They are referencing an article that was written in EE-Times (12/16/96), that discussed Motorola's approach to minimizing tombstoning to under 100ppm's. Motorola noted many variables that could effect the tombstoning even with OVAL land changes. My thinking on this is that a ROUND or OVAL footprint will have more surface tension than a square land, assuming some paste volume is constant, due to the surface area. Are others using OVAL lands to minimize tombstoning or are you having successes with using square lands? Also is anyone using triangle lands for 0402's? Please advise. Thank you John Gulley *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************