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April 1999

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Subject:
From:
"Collins, Graham" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 8 Apr 1999 16:00:31 -0300
Content-Type:
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text/plain (98 lines)
Adhesive can be cured using a reflow solder profile _IF_ the profile has a
slow enough ramp rate to avoid voids formed by entrapped volitiles.
If glue is cured too fast, it can skin over and the remaining volitiles
and/or moisture in the glue can form voids within the glue.  These can trap
flux, solder, whatever... and fail immediately or later, depending on what's
in there.
I saw this happen a couple of years back, and you can also refer to:
"Microcanyons", Circuits Assembly magazine, in the Process Rx column, Dec.
1998 (Doug Pauls and Terry Munson).

regards,

Graham Collins
Process Engineer,
Litton Systems Canada, Atlantic Facility
(902) 873-2000 ext 6215

-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Wednesday, April 07, 1999 3:28 PM
To: [log in to unmask]
Subject: Re: [TN] Can adhesive go thru reflow soldering?


Davis,

I made some tests as follows: I used adhesive and solder paste for the
components on the solder side of double sided assemblies.
So, after printing the solder cream the adhesive has been dispensed.
Naturally, the board is reflowed, with the adhesive uncured, the curing
occurs at a certain stage of the reflowing.
Of course, the curing temperature of the glue is about 150C and the
reflowing cycle was exposing the board to 280C.
I couldn't find any problem with the adhesive after waving the boards, so
the glue didn't crack during the exposure to 280C or the tensions during the
wave soldering.

So the 150C for 90-120 sec is simply the curing cycle, but after curing the
adhesive can suffer reflow and waving. I'm pretty sure of that.

Regards,  Ioan

> -----Original Message-----
> From: Davis Yang [SMTP:[log in to unmask]]
> Sent: Wednesday, April 07, 1999 12:06 AM
> To:   [log in to unmask]
> Subject:      [TN] Can adhesive go thru reflow soldering?
>
> Dear Sir,
>     We have to put adhesive(glue) on PCBA before reflow.  the adhesive
> we are using is LOCTITE 3609. but the spec for the adhesive is 150C
> degree with 90 - 120 Seconds. We want to know if any issue for the
> adhesive to go thru reflow profile? we are worrying about potential
> reliability problem. and the supplier can't give us the answer.
> please give any  advice on the question.
> thanks a lot!
> Davis
>
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