[SI-LIST] Re: Vias on decoupling pads
- From: steve weir <weirsp@xxxxxxxxxx>
- To: gtang@xxxxxxxx, <vincenzo@xxxxxxxxxxxxxx>,<Raymond.Anderson@xxxxxxx>, <si-list@xxxxxxxxxxxxx>,"'Sol Tatlow'" <Sol.Tatlow@xxxxxxxxxxxxxxx>,"'Patrick Jabbaz'" <patrick@xxxxxxxxx>
- Date: Tue, 06 Apr 2004 23:27:28 -0700
George, do they have any problems with wetting of the solder in the
assembly reflow operation after reflowing before component attachment?
Regards,
Steve.
At 10:54 PM 4/6/2004 -0700, George Tang wrote:
>One of the assembly house that we have been using informed us that they have
>found a way to fill the via holes by reflowing the solder on a blank board
>first. But this will only work for vias of discrete components and not
>BGAs, since too much solder under BGAs can cause adjacent balls to short.
>It seems that conductive via plugging is still needed for small pin-pitch
>BGAs.
>
>Best regards,
>
>George
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Vincenzo Kreft-Kerekes
>Sent: Tuesday, April 06, 2004 9:41 AM
>To: Raymond.Anderson@xxxxxxx; si-list@xxxxxxxxxxxxx; 'Sol Tatlow';
>'Patrick Jabbaz'
>Subject: [SI-LIST] Re: Vias on decoupling pads
>
>
>Is there a critical aspect ratio for drilled through vias at which the
>solder wicking becomes self-limiting to get an "auto-plugging" effect or
>would the via diameter have to be so small that it won't even plate? And I'm
>assuming there's not much point in first reflowing the board without
>components to fill the vias, i.e. plugging for the resource challenged?
>
>Best,
>Vincenzo
>
>-----Original Message-----
>From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx]
>Sent: Tuesday, April 06, 2004 12:00 PM
>To: vincenzo@xxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: Re: [SI-LIST] Re: Vias on decoupling pads
>
>Vincenzo Kreft-Kerekes wrote:
> > I've always wondered about this, from both the design and manufacturing
> > standpoint, how is a via-in-pad any different from a via with a
>non-circular
> > capture pad? Why would you use a microvia instead of lets say a 14 mil via
> > in the center of a 40x40 mil 0603 pad which would practically be a large
>via
> > capture pad with corners? Why would a fab house worry about the shape of
>the
> > capture pad, they don't seem to handle octagonal capture pads for through
> > hole vias differently? Or plane stitching vias with practically board size
> > capture pads? Thanks a lot for your help.
> >
> > Best,
> > Vincenzo
> >
>
>The issue is with the solderability of components to the pads after the
>bare pcb is fabbed.
>
>If the via hole is too big or unfilled, your solder may wick down the
>hole causing insufficient solder on the pad.
>
>
>-Ray
>
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