Mike sagely points out:
"There are also variations of U/V adhesive if you have shadowing i.e. a non-clear path for the light energy to reach the adhesive. In this case you want one capable of secondary cure properties to continue to polymerize after being initiated by the U/V light."
But to clarify, any adhesive which is in a shadowed area will not cure by the reaction to light; the cure does not propagate from exposed areas into the shadowed ones. Curing stops when the curing light is removed (essentially). Shadowed areas will need to be cured by a separate mechanism, like heat, chemical activator, moisture, anaerobic, etc, depending on the adhesive type.
I guess I picked up on the word "initiated" - the cure needs to be started and completed by exposure to the correct wavelengths and intensity of light.
Picky, picky, picky.... <grin>
Peter
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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.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barmuta, Mike
Sent: 27 June 2005 22:06
To: [log in to unmask]
Subject: Re: [TN] Light Cure Adhesives
Phil: U/V cure adhesives work well and are quite fast to cure. One down side is they are usually higher in price than more conventional adhesives.
We have used both Dymax and Henkel/Loctite. The application was for component securement prior to reflow. The products used are somewhat thixotropic to prevent flow after application but are certainly dispensable.
The Dymax was their 621 and 921, the Loctite was 3526.
Speed of cure is dependent on type of adhesive material, thickness of deposit, light intensity, distance from light source and shadowing. But in most cases less than a minute is normal. You can use spot or flood light to cure.
There are also variations of U/V adhesive if you have shadowing i.e. a non-clear path for the light energy to reach the adhesive. In this case you want one capable of secondary cure properties to continue to polymerize after being initiated by the U/V light.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
Sent: Monday, June 27, 2005 10:03 AM
To: [log in to unmask]
Subject: [TN] Light Cure Adhesives
Our current adhesive of choice is RTV. Unfortunately it has a long cure time and may be banned from use in products going to the European Union in the coming years.
Our application is bonding 4 capacitors together. The adhesive needs to be thick (medium to high viscosity) so it won't sag, drip or run before curing.
UV cure would be best from a time standpoint. A "glob" of about 1/4" should be about right for this bonding application. The capacitors have an epoxy coating and the operating temperature is about 50° C maximum submerged in a dielectric oil. Electrical or thermal conductivity is not needed. Method of application is expected to be via small air actuated syringe or similar.
Anyone want to put in their 2¢?
Sales calls offline please.
Phil Nutting
Design for Manufacturing Engineer
Kaiser Systems, Inc.
126 Sohier Road
Beverly, MA 01915
voice: 978-922-9300 x1310
fax: 978-922-8374
e-mail: [log in to unmask] <mailto:[log in to unmask]>
www.kaisersystems.com <http://www.kaisersystems.com/>
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