At 07:55 AM 1/4/2010, Randy wrote:
>Can someone please help me break my paradigm with "filling vias in
>process with solder"? I have difficulty seeing how this works.
I think I posted that -- didn't suggest it was easy or say anything
about variability. Just sayin' it's done by some.
>How do
>you ensure consistent, predictable solder fill in thermal vias during
>assembly? If inconsistent, then you really can't count on it to be there
>since any time it's not there you'll pay for it.
>
>If by some chance you can get solder to fill all vias completely, then
>how do you avoid solder flowing out the opposite end of the vias?
Preventing s/m from flowing out the bottom is the easy part.
Make the soldermask opening 1:1 with drill size or just a mil or two
over drill size. That will effectively foul the s/m flow out of the
hole yet allow venting so gasses escaping the via don't void up into
solder joint on other side.
aka Solder mask "cheater via" or "tentbreaker"
>Protruding solder "bumps" can interfere with solder paste printing if
>bottom (second) side assembly is required. These solder "bumps" can
>also interfere with heat sinking if intimate contact is required in this
>area for heat dissipation.
>
>Regards,
>Randy
>
>
>On Tue, 29 Dec 2009 12:28:35 -0800, Dwight Mattix
><[log in to unmask]> wrote:
>
> >Practically speaking, using "thermal conductive" and "CB100" in the
> >same sentence is an oxymoron.
> >
> >
> >Cu ~= 300 w/mK
> >Solder, Ormet, et al ~= 25 w/mk
> >CB100 ~=3 w/mK
> >
> >Small amount more annular copper, filling with Ormet paste (not a
> >cheaper option though) or filling via in process with solder yields
> >much greater increase in thermal conductivity than CB100.
> >
> >At 11:55 AM 12/29/2009, Joe Lara wrote:
> >>Hello TechNetter's,
> >>
> >>Im currently using Du Ponts "CB-100" Conductive Paste to vill Vias
> >>at $400 per 100G. Is
> >>there a more affordable way of filling vias that call out to be
> >>filled (thermal conductive) and
> >>plated?
> >>
> >>
> >>Best Regards,
> >>
> >>Joe
> >>
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