In a message dated 06/14/2000 5:48:48 PM Central Daylight Time,
[log in to unmask] writes:

> Fellow tech netters,
>
>                 I am trying to setup some pull test specs for our expoxy
>  process, we currently using a DEK screen printer and a FUJI FGL2 to
>  dispense glue. Does any one know what are the pull test (in pounds) for the
>  different components (example 0805, 1206, Tantalums, etc)?. I have found
>  that the only way of knowing if a populated board with glue is going to
>  withstand the handling is by having a pull test as a process measurement.
>  Any ideas?
>
>                 Thanks
>
>
>  Jorge Rodriguez
>  Process Engineer
>  Conexant Systems

Hi Jorge!

I'm going to offer my opinions, but they are only that. My opinion of
quantifying the force it takes to separate a component from the epoxy bond is
a little over the top, you could be spending your time doing better things...

The epoxy used to bond components for wave solder has very little strength to
withstand rough handling in the process, and that's where I would concentrate
my efforts if it were me. People need to understand that the boards that have
epoxied components on the bottomside need to be handled very carefully. The
epoxy is only supposed to hold the components on enough to be waved...they
can't be handled in the same way as boards that have soldered components on
them. Of course it's not a good idea to be banging on soldered components
either, but you catch my drift...

I've been through similar situations. The boards come off of wave missing
bottomside components, and the first thing that has been pointed at was; "you
didn't cure the epoxy good enough..." or; "you didn't put enough epoxy
down..." But they have a hard time arguing with me when you can look and see
that the epoxy that was deposited is still on the board and has the imprint
of the component is still in the epoxy...it was obvious that the component
was there and got knocked off...

Epoxy cure is simple...I set 150-degrees C. across all zones in my oven and
set the belt speed to make sure it sees that temp for at least a minute and a
half...simple.

When a lot of people hear the word epoxy, they think that it's the same two
ton strength stuff that you use to repair your broken chair leg with, but
it's not. People need to learn to handle boards very carefully with epoxied
bottomside components....

My two cents...

-Steve Gregory-

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