In response to the questions below: 1. Moisture contaminated solder paste may cause solder balling. The moisture may splatter during reflow, leaving solder balls behind. Improper reflow profile or uneven heating may also cause it. If the temperature ramp rate is too high on some areas of the board, this will increase the probability of solder balling. Solder balling may also be caused by excess oxides in the solder paste, inhibiting the solder from bonding together during reflow. 2. Probably not caused by solder mask unless it is moisture laden. 3. Solder balls may be eliminated with Near Equilibrium Heating. With Near Equilibrium Heating the zone temperatures are very uniform and the set point temperatures are not too high, but very close to the desired board temperatures. The CUREFLOW is designed so the ramp up rate is controlled initially where the board temperature is very low. This reduces the chance of solder balls forming. Minimizing the exposure of the solder paste to high temperature and humidity also reduces the chance of solder balling. 4. Could not find anything in the IPC standards on solder balling. Regards, Loren Hillukka Process Engineer ETS, Inc. [log in to unmask] (e-mail) 612-553-0051 (voice) >Good day all, > >I have a question relative to solder balls and hope that someone can >shed some light on this issue. > >1. What causes solder balls? >2. Could solder balls be the result of incompatiability between flux >and soldermask? >3. How do you eliminate solder balls? >4. What is the IPC acceptability standards for solder balls? > >Any feedback would be greatly appreciated. Thanks to all that offer >assistance. > >Best Regards > >################################################################ >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 web site (http://jefry.ipc.org/forum.htm) for additional information. >For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 >################################################################ > > > ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################