Hi Bob,

Do you have any access to stainless steel pin guages? Maybe you could get
one that fits the hole, then take a sharpie and make a mark that gets you
the depth that you need, then insert the guage and fill the hole from the
other side. I'm thinking that the guage will stop the solder at the depth
you need...maybe.

Steve

On Mon, Jul 9, 2018 at 8:24 AM, Bob Wettermann <[log in to unmask]> wrote:

> All:
>
> We have an assignment where we need to, amongst a variety of induced  board
> and assembly defects, come up with partially filled PTHs.
>
> The objective is to partially fill a PTH on a multilayered, fairly
> thermally massive board and make sure it is filled to approximately 25%,
> 50% and 75% of the height of the barrel. The PTHs have a 2mm hole diameter
> and are 1.57mm in thickness.
>
> We have tried to get this done by blocking a certain portion/depth of the
> holes with liquid solder mask and then getting the solder to flow down into
> the PTH. Subsequent to this we remove the mask. This has not yielded the
> results as the mask does not really get to the right level in the hole. We
> tried selectively adding solder via flux-cored wire and by the time there
> is wetting all around the component lead,  the hole fills up to too high a
> level. Using braid and excavating equipment to remove a small amount from
> the completely-filled hole has also proven to be a challenge as it is
> difficult to uniformly pull solder from the barrel all across its diameter.
>
> One of our thoughts is to have specialty made solder preform "donuts" and
> slide them into the hole.....any other thoughts from the crowd?
>
> Thanks!
> --
> Bob Wettermann
> BEST Inc
>



-- 
Steve Gregory
Kimco Design and Manufacturing
Process Engineer
(208) 322-0500 Ext. -3133

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