[SI-LIST] Re: Vias on decoupling pads
- From: Ivor Bowden <ivor@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 06 Apr 2004 09:57:47 -0700
You can plate vias shut, but it is not generally recommended because
contaminates such as etching solution can get trapped inside causing
problems later.
Ivor
On 4/6/2004 9:41 AM, Vincenzo Kreft-Kerekes wrote:
> 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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