Modify the stencil opening for center pad with few square and the area
should be 50% of pad area.

Aquino

On Wed, May 7, 2008 at 8:42 PM, Gumpert, Ben <[log in to unmask]> wrote:

>
> Amol,
>
> I don't know the surface tension of solder off hand, but I would think
> that for a small QFN, the volume of solder would be a better place to
> start. Figure out how high you want the part to sit, and then determine
> the volume of solder that will be under it at that height.
>
> Ben
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Amol (349)
> Sent: Wednesday, May 07, 2008 8:09 AM
> To: [log in to unmask]
> Subject: [TN] Part floating on solder
>
> Dear Technetters,
> I am trying to determine if a small SMT QFN part (it has a rather large
> center ground pad that needs to be soldered) is floating on the center
> pad solder deposit. What is the value of solder surface tension (Sn-Pb)
> that I can use with this? I am trying to balance the part wt with the
> force due to surface tension to prevent floating.
>
> Any help will be greatly appreciated.
>
>
> Thanks,
> Amol
>
>
>
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-- 
Best regards,
Aquino Quek

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