Hi !. How about via on pad for BGA with blind vias (10mils dia) access from layer1-2
(4mils) thick. Can any one advise.
Have a nice day.
pod wrote:
> Simply, there will be little solder left as it all runs out the hole. With
> some of the first BGA's I worked with, about 6 years ago, I designed boards
> especially to determine solder drain off. I wanted a better "self aligning"
> feature as no equipment was avaialable then ot place these devices. Ten mil
> through holes, and blind vias, were as small as we could go. The applied
> solder paste went first, then most of the eutectic balls. The high temp
> balls stayed, of course, but had no solder joints formed.
>
> Some in the microwave business claim to require holes in pads. Some
> assemblying them, run the boards through two soldering passes attempting to
> "plug" the holes. Sometimes, this works to a small degree. Mostly, the
> solder joints don't form.
>
> Earl Moon
>
> ----- Original Message -----
> From: Rick Thompson <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, September 21, 1999 2:50 PM
> Subject: [TN] Via in BGA Pad?
>
> > We have a customer who wants us to run a board that uses a 256 pin BGA.
> The
> > problem is, he has placed vias for signal routing in the center of the BGA
> > pads. The vias are plated with a 10mil finished size. There is no solder
> > mask tenting these vias on the bottom of the PCB. I realize this isn't
> > normally recommended, but as they already have the boards, re-layout isn't
> > an option. My question is basically, what types of problems will I have?
> I
> > know I may get wicking of solder through the PTH, but given the hole size,
> > how bad is it likely to be? Anyone have any experience attaching BGAs to
> > this type of pad configuration?
> >
> > Thanks in advance.
> >
> >
> > Rick Thompson
> > Ventura Electronics Assembly
> > 2665A Park Center Dr.
> > Simi Valley, CA 93065
> >
> > +1 (805) 584-9858 voice
> > +1 (805) 584-1529 fax
> > [log in to unmask]
> >
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