Encapsulant for leads in an aqueous environment

Details Encapsulant for leads in an aqueous environment Encapsulant for leads in an aqueous environment

1998-10-14

2001-03-20

Dye, Rena L. (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C438S035000, C438S068000, C430S280100, C522S103000, C525S522000, C525S523000, C338S275000

Reexamination Certificate

active

06203871

ABSTRACT:

TECHNICAL FIELD
This invention relates to encapsulating electrical leads on an inkjet printhead or other aqueous environment.
BACKGROUND OF THE INVENTION
In the production of a thermal inkjet print cartridge, a printhead is bonded to the flexible tab circuit by means of either wire bonds or tab bonds. These exposed bonds have to be protected against possible mechanical damage and possible chemical damage (due to contact with inks). An encapsulant material ideal for use in an inkjet print cartridge should have very good adhesion to tab circuit material (both polymeric and metal) and very good chemical resistance. This need is met by the present invention.
DISCLOSURE OF THE INVENTION
An encapsulant currently in use, UV 9000 from Emerson and Cuming, is a urethane acrylate system and uses a free radical cure mechanism. This presents an inherent problem. One has to take extra precaution to ascertain that the atmosphere is inert before initiating the cure. In addition, this system is incapable of continuing the cure once the light source has been removed. This sometimes results in leaving uncured material in deeper areas and shadowed areas where the ultra violet (UV) light has been unable to reach.
Many of the commercially available encapsulant materials use a free radical cure mechanism which will have similar disadvantages. Known commercially available materials do not have good chemical resistance to aqueous inks.
The encapsulant material in the present invention uses a cationic cure mechanism. This instantly solves one problem. The need for an inert atmosphere is no longer necessary. In addition, this system is capable of continuing the cure once the source of light has been removed. Some of the other positive attributes of this system are long shelf life (months/years) and a very good pot life (days). A chemical resistance study indicates that this system has very good resistance toward aqueous inks such as the inkjet inks sold by the assignee of this invention. This study was carried out for eight weeks at 60° C.
DISCLOSURE OF THE INVENTION
Electrical leads of an apparatus in an aqueous environment are encapsulated in a thoroughly cured mixture substantially as follows, by weight:
88% bis-phenol A epoxy oligomer;
11% epoxy novolac oligomer; and
10% hexafluoroantimonate salts (as an ultraviolet cure initiator).
In application, the mixture requires no special atmospheres and has a long pot life. In use the cured mixture has excellent resistance in an aqueous environment.


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