> I just looked at this a short while ago. I am also using a 388 1.27mm
PBGA,
> by AMD - ELANSC520. We are intending to tent the Vias as the folks on this
> group suggested. I have noticed your Via pad is smaller than we were asked
> to use by our fab house. We were asked to use 0.71mm pad and 0.3mm hole.
0.3mm ~ 12mil, so your via hole is the same.
0.71mm ~ 28 mil, so your via pad is 3mil wider than mine.
I was just going by National Semiconductor's recommended land patterns for
the parts. They seem to recommend a 0.64mm (25mil) pad for the solder
balls. They don't specify how big the via should be, but of course it has
to fit between four pads. I just figured on using the same size for the via
pad. Maybe that's not such a good assumption?
For vias, I normally use 32mil pad, 18mil hole, but BGA is pushing me into
new areas...
Best regards,
Ivan Baggett
Bagotronix Inc.
website: www.bagotronix.com
----- Original Message -----
From: "Colin Weber" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Thursday, August 23, 2001 5:45 PM
Subject: Re: [PEDA] tenting vias
> Ivan,
>
> I just looked at this a short while ago. I am also using a 388 1.27mm
PBGA,
> by AMD - ELANSC520. We are intending to tent the Vias as the folks on this
> group suggested. I have noticed your Via pad is smaller than we were asked
> to use by our fab house. We were asked to use 0.71mm pad and 0.3mm hole.
>
> If your using the same chip, I'd be interested in how it works out for
you?
>
>
>
> At 02:35 PM 22/08/2001 -0400, you wrote:
> >Hello, all:
> >
> >I am designing a board with a 388 BGA chip. I have questions about vias:
> >
> >1) Should I tent the vias under the BGA?
> >2) If (1) is yes, should I tent other vias on the board?
> >3) If (1) is yes, what substance/method is used to tent vias?
> >4) If (1) is yes, what do I tell the PCB fab house to get them to tent
the
> >vias? Is it as simple as "tent the vias"?
> >5) If blind vias are used, do they need tenting also?
> >
> >The BGA has a 1.27mm ball grid. I am considering a 25 mil pad, 12 mil
via,
> >31 mil solder mask opening diameter. Does this sound good? If not, what
> >would you recommend?
> >
> >Best regards,
> >Ivan Baggett
> >Bagotronix Inc.
> >website: www.bagotronix.com
> >
> >
>
>
> Regards,
>
> Colin Weber
>
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