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December 1998

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Subject:
From:
Tom Braswell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 23 Dec 1998 15:22:32 -0500
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Wade,

I would agree with Stephen and Roger,  we use Loctite 3609 on all our PCB's.
I test the strength the same way Stephen does.  We had similar problem with
chip components coming off. QC and Industrial Engineering said it was coming
off during wave solder, but further investigation told me that it was two
problems.
1. Improper handling of PCB after glue cure.
2. Uncured Solder mask
Uncured soldermask problem exhibited loss of components and masking ( mask
peel off ) especially on copper areas.  Contact with our PCB supplier
validated that they "forgot a process".  They recommended a bake of 150 C
for 4 hours. This however can cause some board warp, if not controlled.

Another thought is there any contamination at all on the PCB?

I know some components, IC' and crystals have problems with mold release
agents that will cause components to not be bonded and then fall off
especially on double Reflow.

-----Original Message-----
From: Wade Oberle <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, December 23, 1998 8:58 AM
Subject: [TN] Surface Mount Adhesive


>Dear Technetters,
>        I am having a problem with SMT adhesive sticking to some types
>of solder mask.  Does someone out there have experience with using SMT
>adhesive on glossy boards vs. matte finish boards.  I am using Loctite
>3609 or Epibond 7275 or Epibond 7275-1 with a cure cycle of 145-150
>degrees centigrade for 4-5 minutes.  Is there an SMT adhesive or cure
>cycle that works better with glossy boards?  We seem to have a problem
>with adhesion at room temperature and at wave solder temperatures.  We
>run a standard wave solder profile and have even increased the wave
>speed to 5.75 feet/minute from our norm of 4.5-5.0 feet/minute.  This
>helps but we run the risk of voids and poor solder connections on some
>components.
>If I cure the boards and then use a 'push' tester to measure the force
>required to remove the 'glued' components, is there a standard for
>minimum and maximum expected force for removal?  I have heard of some
>people using a custom socket and a torque wrench to measure the strength
>of the cured adhesive.  Is there a standard specification for this test
>method?  Which test method do you think is best?  The tests mentioned
>above are done at room temperature.  Is there a way to measure the 'hot'
>strength of the adhesive bond?
>
>Thanks in advance.
>
>Wade Oberle
>
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