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November 2007

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Subject:
From:
Peter Swanson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Peter Swanson <[log in to unmask]>
Date:
Wed, 21 Nov 2007 15:58:44 -0000
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Peter,

You don't say how many of these you are making, but with that proviso:

1) A single part "chipbonder" or surface mount adhesive like the one
mentioned will require a substantial heat bump to cure.

2) Rather than an epoxy, maybe a methacrylate adhesive would be better -
often less brittle, but good all round adhesion. Something like Araldite
2022 is a two part product, but in a cartridge, so easy to apply. Might
still me a bit smelly through....

3) If you have,  or can justify the purchase of the equipment, then a UV
acrylic adhesive does this job well. No mix, fast cure, good adhesion,
choose your viscosity and the right resiliency to give the stress
relief. 

Regards,
Peter

--------------------------------------------------------
Peter Swanson           [log in to unmask]
INTERTRONICS                http://www.intertronics.co.uk
Tel: +44 1865 842842                   Oxfordshire, England

INTERTRONICS is dedicated to providing quality material, consumable 
and equipment solutions to the high technology, high performance 
assembly industries, incorporating outstanding levels of technical 
support and customer service.

Read our news! http://www.intertronics.co.uk/blog/blog.htm

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 21 November 2007 13:28
To: [log in to unmask]
Subject: Re: [TN] Epoxy application

Hello, Peter
I have a client using Loctite 3621 epoxy in a very similar application.
It bonds to the mylar sleeving very well. Try it.  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter L
Sent: Tuesday, November 20, 2007 6:00 PM
To: [log in to unmask]
Subject: [TN] Epoxy application

Hello,
 
I would like to ask for opinion on an epoxy application. We apply RTV to
bond and secure 2 electronic devices on a PCB. 

But after noticing the RTV bond breaking off during vibration test, our
customer has specs in a 5min 2-part epoxy (made by
http://www.devcon.com/techinfo/5_MINUTE_FR.pdf) to replace the RTV. The
problem is that the Devcon epoxy is fast cure, requries 2 part mixing,
and carries a strong, irritating odor. I would like to move away from
using Devcon and expect that there must be more process friendly epoxy
for such application.

The 2 materials to be joined were a flat ferrite inductor and round
capacitor having a PVC sleeve. Due to positioning of the 2 devices there
is generally a ~0.25" gap between them for the epoxy to fill. The epoxy
bead deposit is about .75" long x 0.5" wide. (see following link to the
assembly
http://members.shaw.ca/ppwlee4/Epoxy_appl.JPG)

I am looking for recommendation of a suitable epoxy to allow:
 
- 5-10 min working life before it starts curing
- process friendly (smell, preferrable no pre-mix)
- good adhesion to the component/PCB surfaces.

Any suggestion is appreciated. Thanks.


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