Steve,
        the other penny drops! A deposition of 0.006 - 0.008" will not
result in a reflowed solder height of 0.006 - 0.008". The solder paste
reduces by the volume of organics/flux that was present and the solderballs
reflow to form a homogeneous mass. So you will not have the same column
height of solder on your tab pad.
        I don't have all the answers but the footprint information is what
our footprint reference states it should be. It doesn't however give me
enough information to tell what the height of their tabs would be above the
board.

Sincerely,
Brad Velander.

Lead PCB Designer
Norsat International Inc.
Microwave Products
Tel   (604) 292-9089 (direct line)
Fax  (604) 292-9010
email: [EMAIL PROTECTED]
http://www.norsat.com

See us at Booth 323 at Satellite 2002 in Washington, DC March 6-8.



-----Original Message-----
From: Steve Baldwin [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, March 05, 2002 4:53 PM
To: Protel EDA Forum
Subject: Re: [PEDA] TSSOP Power Pad



>  I checked the source we use for our footprints and on the TSSOP 28
> pin devices with the bottom tab, they suggest a pad the same size as
> the tab and their common solder paste deposition of 0.006 - 0.008

Ah ! The penny drops. That corresponds to the distance between 
the base of the package and the board so as soon as it wets, it'll 
pull the package down just right.

Thanks,

Steve.

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