Alan, Without masking the vias from the bottom prior to wave, you have the potential to either perform a 'second reflow' on the BGA during wave or cause voids/flux entrapment in the joints, or both. The voids can be impressive, 40-50% of the sphere. There has been a lot of discussion both here and on SMTNet regarding vias in BGA pads, with the majority opinion being "Don't Do It!". If you must, plate the vias closed rather then just HASL fill. This will eliminate the wicking/voiding and should eliminate the masking requirement. Mike McMonagle PCA Process Engineering Supervisor K*Tec Electronics 1111 Gillingham Lane Sugar Land, TX 77478 (281) 243-5639 Phone (281) 243-5539 Fax [log in to unmask] > -----Original Message----- > From: Alan Kreplick [SMTP:[log in to unmask]] > Sent: Monday, April 26, 1999 1:44 PM > To: [log in to unmask] > Subject: [TN] BGA Vias > > Hello Technetter's: > > Hey, does the following look familiar? I sent this problem out last > week but > was 0 for 1743. Any responses via Technet or direct would be greatly > appreciated > > Our BGA process (for a mixed-tech pcb) historically was to: > > fill (solder) the vias with a bottom-side stencil > place & reflow the BGA on the top-side > mask the BGA location and wave the thru-hole components > > Note: via fill required for In-circuit Test for their probes and/or > for vacuum. > > Question: What is the risk of exposing the BGA vias to the wave? ie: > reflow the > bga, cause voids, or ???? > > > Thanks in advance, > > Al Kreplick > Sr. Mfg. Eng. > Teradyne, Inc > Boston, MA > 617-422-3726 > > ################################################################ > 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 ################################################################