Alan,

Are you preheating the board? Preheating may help you
obtain hole fill greater than 50%. I agree adding
solder from the top may fill the hole but typically
you end up with "two solder" joints instead of one
contiguous joint.

Tony Di Mauro
Circuit Technology Center
Quality Engineer


--- Alan Kreplick <[log in to unmask]>
wrote:
> Hello Technetters:
>
> I've gone from the WS6536 100% world to IPC's 50%
> hole fill requirement.
> Unfortunately, I have a .150" thick pcb (G10, with
> many layers of ground) that
> must be waved in a selective soldering fixture, that
> is averaging about 33-50%
> hole fill.
>
> The customer is looking at the 50% hole fill spec,
> and touching up to meet this
> requirement (also, they are touching up from the
> topside and cosmetically
> getting 100% hole fill to make them feel happy).
>
> To achieve the current hole fill, my topside
> temperature leaving the preheaters
> is 270F and the bottom-side portions of the board
> that are exposed to the
> preheaters and wave are at 320F (my normal range and
> that recommended by the OA
> flux manufacturer is 180-220F topside).
>
> Also, the speed is 60cm/min (2 f/m), which on my
> machine equals about a 3 second
> dwell @ 482F.
>
> I can get 50% hole fill if I max out my preheaters
> which gives me a top-side
> temp of 320F and bottom-side temp of 370F.  Running
> a board at these
> temperatures just to meet a 50% hole fill
> requirement doesn't make sense.
>
> My theory: if 50% of a .060" thick board (.030") is
> OK, then a 25% hole fill of
> a .150" thick board (.0375") would also be OK.
>
>
> Any thoughts???
>
>
> Al Kreplick
> Sr. Mfg. Eng.
> Teradyne, Inc.
> 978-370-1726
>
>
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