Hi Tim,
                My recommendation would be to glue the parts that need to be secure and
then conformal coat after.  If you glue after, all you will really be
gluing is the coating that is on the component.  The glue won't adhere to
the coating like it will to the PCB.  I don't believe there is anything in
the 610 that specifies.

        Just my opinion.
        Connie M. Korth
        Quality Specialist
        Reptron Mfg. Services


-----Original Message-----
From:   Tim McQuay [SMTP:[log in to unmask]]
Sent:   Thursday, May 23, 2002 12:45 PM
To:     [log in to unmask]
Subject:        [TN] Conformal coating / gluing

Hi Folks:
We have a debate regarding sequence of operations when we glue down
components and apply conformal coating to the same board. The IPC-A-610C
does not cover this and I have not been able to locate any other info.
Basicly we want to know, do we glue first or do we coat first. Can someone
please tell us if the bond between silicone glue and conformal coating is
as
strong as between silicone glue and PCB uncoated surface. We are concerned
that heavy components, such as the large caps on some of our boards, would
not be well supported if bonding is done after conformal coating.
We have our own bias but we wanted to hear an outside opinion and/or see a
standard on the topic. The adhesive and coating we use are listed below.
        3-1744 (DOW), SILICONE ADHESIVE - for staking big components
        KE3421 (SHIN-ETSU), SLCN BRD COAT - conformal board coating

Thanks
Tim McQuay
Training Coordinator
Vansco Electronics
Fax: 204-474-1674
e-mail: [log in to unmask]

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