That should work well. The vias will fill with resin during lamination.
Then they will be plated over in the following electroless or shadow.
This fills the holes very very well with a nice covered plated mostly
flat surface with no hole. We've done this with 0.008" to 0.012" drilled
holes and it finishes nicely.
Steve Underwood
Engineering Manager
Circuit Center, Inc., 4738 Gateway Circle, Kettering, Ohio 45440
(937) 435-2131 phone (937) 435-7698 fax
[log in to unmask]
On Fri, 24 Sep 1999 15:42:10 +0800 Goh Guan Chye <[log in to unmask]>
writes:
> 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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