Hi Doug.
1. We are using Loctite as our glue supplier and have no problems with their products.
2.  We are using a stencil process to apply the glue.  There are pros and cons to this as there are with any processes.  One of the advantages is that if the board is fairly large, the time to print the glue is only seconds and you can use an existing paste printer to do so (no additional capital is needed).  But, the disadvantage is that all glue heights are the same regardless of package.  When using an X-Y dispenser, you can control the amount of glue with size of nozzle, time, and pressure.  The disadvantage to the X-Y method is that if the nozzle clogs, it can be difficult to identify which dots are missing.
3.  The biggest problem with a glue process is handling -- making sure the components do not get dislodged prior to wave.  Other problems that pop up include bonding strength issues introduced when a components have mold release or other contaminants on them, or, problems with the cure profile.

Also, waving some components can be a problem too especially if they are shadowed by others or run thru the wave in such a was as to cause them to shadow themselves.  SOT-23's can be difficult in this aspect.

-Carrie

-----Original Message-----
From: McCall,Doug [mailto:[log in to unmask]]
Sent: Wednesday, March 05, 2003 10:17 AM
To: [log in to unmask]
Subject: [TN] Glue suppliers for chip-on-wave assembly


Hi all,

We have a couple of products that have come our way that are
designed for glue-on-wave (i.e. 0805; SOT23 and some SOIC's)
being glued at SMT and then flow-soldered in-amongst a whole
lot of through-hole leads (500 leads on one of the assemblys).

Clearances round the PTH leads make a pocketed flow-solder
pallet not possible.

1) What manufacturers of glue do you guys recomend/use??
2) Does anyone use stencil printing of the glue onto the
   board before SMT or use x-y application??
3) What issues are there generally (boards are designed for
   this process);

Generally any comments are welcome.

Thanks for your inputs,

Douglas I McCall,



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