Natasha,

I am a little confused what you mean by "Glue mask".  SM-817 defines the
glue properties. It is not a process document telling you how to
assemble.

If you are looking to stencil print adhesives and are looking for
aperture design requirements there is a section in IPC-7525A.  

From my experiences you need to match your stencil design to your glue.
I did a study many years ago where we compared aperture sizes and shapes
to glue suppliers.  We compared spread/slump and strength after cure.
From a spread/slump perspective there was quite a variance.  You also
need to match your glue to the height you need to achieve.  If you are
gluing discretes you don't need as much height but if you are looking to
do SOIC's or SMB's (not recommended) you will need to worry more. You
need to make sure you have good contact to the components but you don't
want to compress the glue and cause it to ooze onto the pads.  I also
only glued discretes down to 0603's.  It is also important to look at
you spacing and alignment.  If not you can get shadowing that can
contribute to skips in your wave soldering process.

I hope this is what you are looking for and it helps.



Russell Nowland
Advanced Manufacturing Engineer
Address: 14000 Quail Spring Parkway, Suite 300
Oklahoma City, OK 73134
email: [log in to unmask]
Desk: 405-302-1660
Cell: 405-203-0034
Fax: 405-302-1622

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Natasha Baker
Sent: Monday, June 16, 2008 8:25 AM
To: [log in to unmask]
Subject: [TN] Glue Mask Requirements

Hi All,

I have a question regarding the glue mask when designing PCBs.

I am ordering the IPC SM-817 which provides requirements for surface
mounting adhesives, but am unsure if it will provide requirements
specifically on dimensions for the glue mask.  Are there concrete rules
for
glue mask dimensions?  Or, should the glue mask just follow the
component
outline?  Also, is it always necessary to use a glue mask, or only when
components are placed on both sides of the board?

Best Regards,

Natasha

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