Jacob, Actually IPC 6012 states the opposite, vias may be completely plugged. If you have access to 6012 look at table 1-1 for plated holes (including vias). When plating is not desired in vias the requirement is typically to tent them with solder mask. Franklin "" wrote: > > > Technetter, > > 1) Is there any spec that says no solder is allowed in via holes > (<22mil) especially the HASL boards? > > I've encountered a numerous of HASL boards with this problem. Due to > the solder in via hole, solder lump will start to form at the annular > ring of the via holes & it causes uneveness solder paste printing as > well as posibilities of damaging the solder paste stencil. The solder > lump will only form after the first IR reflow & with the via hole > facing downward. When it's going for its second round of SMT, the > problem start to appear, bridging. > > 2) Is there any recommended solutions to this problem? > > Another input, most of these boards were plugged either from the > primary or the secondary side. In my case, we'll always mount the > plugged side first & then followed by the other side. > > 3) Is there such a design rule that the process has to go the other > way round? Meaning, mount on the unplugged side first insteads of the > plugged side. > > Regards, > > Jacob Pao (SQE) > ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################