Hi Poh,

The thickness is dependent on the size of the openings. You should keep at
least a 1.5:1 ratio between stencil opening and stencil thickness. e.g.: If
opening is .009, thickness must be equal to or less than .006.  If opening
is larger, stencil can be thicker.

We use .006 thick stencil and try to have our openings .010 or slightly
more for better paste release. Those numbersare dependent on the footprint
design. I like for the pads to be bigger than the opening in the stencil.
If you're stuck with a narrow pad on the board, you might have to use a
narrower opening, hence a thinner stencil.

There are probably some solder paste manufactureres out there that have
developed a paste that can be used with a tighter ratio, but I am not aware
of them.

Good luck

Charlie Barker





Poh Kong Hui <[log in to unmask]> on 05/14/99 10:57:07 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Poh Kong Hui <[log in to unmask]>



 To:      [log in to unmask]

 cc:      (bcc: Charles Barker/US/I-O INC)



 Subject: [TN] Stencil Thickness









Hi Technetters,

What kind of stencil thickness you would recommend for 20 mil pitch QFP?

4, 5 or 6 mil ?

Thanks in advance.
Poh

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