Hi Alan, here's what I can come up after 18 months of running boards with 0402. The design: - I had both ENIG and white tin finishes, makes no difference. Didn't run them on HASL, but I would stay away. - pad design is critical. I had a board with 600+ 0402s, both resistors and caps and no tombstoning with pads that are square, 20x20 mils, spaced at 22.5 mils. I had random tombstoning, about 5% of the quantity of the 0402 on a board with different land pattern. - did not see any difference due to glossy or matte solder mask - I didn't see any tombstoning on so called bad thermal design, that is on of the pads connected to a tiny track, while the other connected to trak of the same size like the pad The printing: - critical. Make sure the registration is perfect. - I did not see any difference between home plate apertures and normal rectangles at 100% of the pad. Placement: - critical. Get the best out of your machines, slow them down if necessary, use supports. You need to have the components equally seated on both pads. By the way, normally is the caps that tombstone, since the torque due to the surface tension is bigger because of the height. Reflow: - I use ramp to spike in a convection, 8 active zones, oven. I did not have to play around with the profile, the standard one used for most of the assemblies did a good job. Solder paste: - I didn't need any new paste. The regular one used for bigger parts was OK. It's the normal no-clean CR36 from Multicore. Although is leaving a lot of flux residue, this does not seem to have any influence of the yields. Hope this helps, Ioan > -----Original Message----- > From: Alan Kreplick [SMTP:[log in to unmask]] > Sent: Tuesday, September 25, 2001 4:36 PM > To: [log in to unmask] > Subject: [TN] 0402s > > Hello Technetters: > > I know some of you are already doing 0201s, but I'm hoping you can give me > your "lessons learned" about 0402s. > > Any information on stenciling, placement, reflow, and paste selection > would > be greatly appreciated. > > > Thanks in advance for your responses, > > > Al Kreplick > Sr., Mfg. Eng. > Teradyne, Inc. > 978-370-1726 > > -------------------------------------------------------------------------- > ------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt delivery of Technet send the following message: SET > Technet NOMAIL > Search previous postings at: www.ipc.org > On-Line Resources & Databases > > E-mail Archives > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 > ext.5315 > -------------------------------------------------------------------------- > ------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------