Mpark, I have run a few trials using via in pad and found that the solder does wick thru the holes. Even worse if wave is required. How do you design the sm artwork? If the hole is tented isn't there the risk of paste capping an air bubble? Steve Jeremy, I see the wicking of solder thru via holes is problem, thus forms insufficient solder joint fillets. To get around the problem with via holes in SMT pads w/o introducing board cost increase/other fabrication process complications, use a smallest possible via hole size, which is 0.25mm (0.010") and mask bottom side via hole pads with LPISM. This restricts the flow of solder thru via holes and at the same time, allows flux and volatile gas to escape thru them. Mpark NII-Norsat International Inc. >>> Brad Kendall <[log in to unmask]> May 29, 1998 10:10 am >>> As far as getting the initial solder joint to work using this pad you may be successful. You are obviously aware that you will get solder wicking into the via and possibly starving your solder joint, but with a PBGA with eutectic balls you should be fine. However, to rework the joint through a 12-16 mil via? If you apply heat to the via it will pull the solder away from the part because solder flows toward the heat source. If you did force enough solder through the via to heap up and touch the BGA, you have not heated the BGA pad and thus you will not get a good solder joint to the BGA. I guess it is worth a try. But the rework part is questionable. Brad Kendall Hella Electronics Corp. [log in to unmask] on 05/29/98 08:04:26 AM Please respond to [log in to unmask]; Please respond to [log in to unmask] To: [log in to unmask] cc: (bcc: Brad Kendall/Hella North America Inc.) Subject: Re: [TN] BGA Footprint Jeremy, My guess is you will still get some solder wicking down the hole. Anyone else try this yet? But I don't understand why you can't rework your BGAs, not that you should have to rework many anyway. AirVac, SRT, Conceptronics and others make very nice equipment for BGA rework. regards, Bev Christian > ---------- > From: Jeremy POLLARD[SMTP:[log in to unmask]] > Sent: Friday, May 29, 1998 1:00 AM > To: [log in to unmask] > Subject: [TN] BGA Footprint > > Hello, > am hoping that someone out there has experience with BGA footprints. > > We have completed Rev 1 of a double Eurocard PCB, 10 Layers with 7 x 356 > pin BGA devices on board. While everything went well with this run and we > had no problems with ball connections, it is impossible to perform any > rework or modifications if required. > The footprint was the recommended pad with track out to a via or " Dog > bone". On the next revision we would like to do the following, Elimnate > the "dogbone", place a through hole in the actual pad for the ball and > adjust the solder paste stencil so that the volume of paste deposited > allows for the hole through the board. > I would use a hole size of 0.3mm (12mil) to 0.4mm(16mil) certainly no > larger. > This approach should enable us to rework dodgy joints from the solder side > of the PCB > It will also allow us access possibly to test the pins from the BGA. > > Has anyone done this ? > Was it succesfull in a production environment ? > > Many thanks foryour help. > > regards > > jeremy > > ################################################################ > 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 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 web site (http://jefry.ipc.org/forum.htm) for additional information. 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