Good afternoon, Chan;

If your stencil is .006" thick and you are using a metal squeegee, you should 
RARELY get more that .006" of paste deposited on your boards. I have not done 
critical measurements in a long time, but I would venture to say that, when 
using a good metal squeegee with a good metal stencil, your paste deposition 
would rarely vary more than +/- .0005"...and most of that tolerance would 
probably be on the minus side on large parts caused by scalloping.

Your stencil thickness needs to be somewhere between the tolerance limits you 
mentioned, if that's what you want on the board. Not knowing whether or not you 
have any fine pitch on the board, I can't make a strong recommendation on 
stencil thickness. If you do not have fine pitch, I would suggest you go to a 
.008" thick stainless steel stencil.

Good luck,

Charlie Barker
Mfg. Engr.
Input/Output, Inc.
Stafford, Texas
713/276-3328

ORIGINAL:
From: chanyk @ pacific.net.sg (Chan Yong Kwee) @ Internet
Date: 04/03/96 11:37:00 AM
Subject: Stencil design or Solder Paste?

Good day,
        We have encountered a low solder paste level in the printing
process.  We are using a Metal squeegee on a Metal Screen to print the
solder paste onto the PCB before SMT processes.  
        We were wondering whether the solder paste viscosity is too thick;
or there is a Stencil Design fault.  The SPC chart states the solder paste
thickness should be between 6.5 mil to 8.5 mil.  But we can only achieve
only up to 6.2 mil of solder paste thickness.  Our stencil is 6.0 mil in
thickness.
        Can anyone give me the specifications on the design of Metal
Stencils and give suggestions on how to solve the above problems? Thank you.

Regards,
Chan Yong Kwee
E-mail:[log in to unmask]
Tel    : (65) 746-6617
Pg     : 9-490-6514