Paul, Five years ago we conduct a study to better understand tombstone at 0603 components ( we had a big problem that time !!! ), but I moved from that company and could remember only the highlights, may be with this information you can apply some experiments to 0402. The experiment were conducted with prototype boards with 11 different pad configuration and 3 types of solder paste Results Capacitors are more sensitive to tombstone than resistors Solder Paste with same comercial characteristcs ( Type 3, 63/37 , No Clean ) gave different results, at that time the best result we get with Alpha Metals 390 DH4 Pad design with more solder volume applied get more tombstone results Pad design with more distance between the two components pads ( center to center ) get more tombstone Different solder profile were not tested but be carefull with fast ramp up. With this experiment we choose the better pad pattern with the better solder paste to solve our problem. You can easily start evaluating different solder paste than goes to pad design. I believe with 0402 you have to be concerned with placement accuracy also. Until the changes at our process were not made we had to use glue at top side process ( we applied solder paste and then glue with a siringe dispense machine ) to avoid tombstone at 0603 component. Like americans says " This is my two cents ... " Jorge Dourado de Santana Maintenance / Process Engr Microtec - Brazil > -----Original Message----- > From: Paul [SMTP:[log in to unmask]] > Sent: 10 de Maio de 1999 19:47 > To: [log in to unmask] > Subject: [TN] Tombstoning 0402 caps.... Help needed. > > Hi All, > I am looking for any information concerning the reduction of > tombstoning. > > The only parameters that we can adjust are the size of the > paste > dot, the type of paste used (any composition as long as it is eutectic > PB/SN), and the reflow profile (two atmosphere choices). > > Since the physical pheomeonon is centered around surface > tension I > am very interested to read about any study that was done that resulted > in > reduced surface tension. > > Currently the process is in the fractional percentages, the > goal > is to go below 100 DPM. > > Thanks, > Paul Gill > Process Engineer > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV > 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################