Suzanne Nachbor asked:

>We are looking at stencil printing adhesives for chip components instead of
>dispensing due to a high part number count.  I have heard of people printing
>a dot for chips versus a rectangle versus a bow tie.  Is anyone doing this
>and if so any success or failures that you would like to share?

We print Heraeus PD 860002 adhesive with a stencil. Works great.

For SOIC's, we use two round dots 0.060" diameter, and for 1206's one dot
0.040" diameter. This is with a laminated stencil (0.004/0.004", I think),
such that the large apertures are cut through both metal layers, and the
small dots cut through one layer. On the metal layer which is not cut for
small dots, there are openings (like a stepped stencil would have) to
accomodate the squeegee. This produces thicker dots for the SOIC's and
thinner dots for the chips.

You'll need a somewhat softer urethane squeegee, say 60 durometer.

We have a glue dot machine, but this is the _only_ way to do a lot of dots,
IMHO. You can print up into the thousands of dots in a few seconds, and it
works quite well in terms of definition. Cost of the stencil is probably in
the $500 range.

Cleaning the stencil is a minor pain, but with a lint free towel, alcohol,
and some elbow grease, it can be done. You must do this farily quickly
after the end of your print run.

you might contact:

Brian Bauer, Heraeus-Cermalloy 212-825-6050
Bert Deutsch, Utz Engineering 201-778-4239



regards,

Jerry Cupples
Interphase Corporation
Dallas, TX USA


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