Pat McGuine asked:

>We have a new design that has 0805s on the bottom of a board that will be
>wave soldered.  We have done 1206s for years but our dot for the 1206s is
>too large for the 0805s.
>
>We have a Camalot w/ a rotary displacement pump doing the dispensing.  It
>has a mechanical z-axis compensator which allows me to set the height of the
>needle above the board - but not on the fly (micrometer adjustment).  We
>cure the adhesive in an IR oven.
>
>I could use some advise.  I'm looking for answers to these questions:
>Please don't feel like you have to answer all of them, respond to as many
>(or as few) as you would like.
>
>1) What adhesive have you been able to acheive good results with?  What is
>it's rated viscosity if you happen to know it?

Heraeus PD86002

>2) What needle diameter do you use?
>3) Do you try to achieve a dot 2x the needle diameter?  If not, what size
>dot do you strive for?
>4) What is the height of the needle above the PCB?
>5) What air pressure do you use (do you have a rotary displacement pump)?
>6) Do you use a different size dot for 1206s on the same board.  If so, how
>do you achieve the larger dot?

N/A all the above.

I suggest you design a stencil and try printing the dots. If you are mixing
SOIC's you might use a laminated (or stepped) stencil with larger & taller
dots for the IC's. I would think you can print a dot small enough for an
0805.

I think if you call Heraeus or Loctite thay can help you set up an adhesive
printing process; there is really no magic to it (softer squeegee blade -
say 60 durometer). Since we started, our glue dot machine gets a lot more
rest, and we can keep up with the pick and place machines a lot better.

This is one process changeover here that was an instant hit...

regards

Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com


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