Compositions – Electrically conductive or emissive compositions – Metal compound containing
Reexamination Certificate
1999-09-08
2001-06-05
Gupta, Yogendra (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Metal compound containing
C252S500000, C252S509000, C252S510000, C252S519200, C252S521500, C523S427000, C523S437000, C523S457000
Reexamination Certificate
active
06241915
ABSTRACT:
TECHNICAL FIELD
This invention pertains to epoxies, epoxy systems, and methods of forming conductive adhesive connections between electrical nodes.
BACKGROUND OF THE INVENTION
Electrical circuits are frequently constructed by adhering components of the circuit to interconnects with conductive epoxy. The conductive epoxy is initially provided in an uncured, and non-conductive form. The epoxy comprises conductive materials, such as metal flakes, which are spaced too far apart in the uncured form of the epoxy to create conductance. As the epoxy cures, it shrinks and the conductive particles come in contact with one another to transform the epoxy into a conductive form. The transformation from a non-conductive form of epoxy to a conductive form occurs gradually over time, rather than as a step function. The epoxy progresses from being non-conductive, to being partially conductive, to being fully conductive over a period of from one to two hours.
In some circuits, batteries and integrated circuit chips are physically and electrically interconnected with conductive epoxy. Unfortunately, during the curing of the epoxy there is a period when the epoxy is partially cured and during which a low current flows from the battery to the chips. The low current can turn the chips “on” at lower than desired current flow. When the chips turn on at such low current flow, there is an undesired battery drain, and, frequently, a “latch-up” of the chips whereby the chips are rendered non-operable. Accordingly, it is desired to develop alternative methods of adhering chips and batteries to substrates whereby the low-current flow is substantially alleviated.
SUMMARY OF THE INVENTION
The invention encompasses epoxies, epoxy systems, and methods of forming conductive adhesive connections between electrical nodes.
In one aspect, the invention encompasses a method of forming a conductive adhesive connection. First and second nodes are provided. A liquid conductive epoxy is provided between the first and second nodes. The liquid conductive epoxy has sufficient conductivity that a 15 mil length sample of the liquid conductive epoxy having cross-sectional dimensions of 50 mil by 2 mil has a resistance of less than about 100 ohms along its length while having a viscosity of less than about 100,000 centipoise (cps). The liquid conductive epoxy is cured to form a conductive adhesive connection between the first node and the second node.
In another aspect, the invention encompasses a method of forming a conductive adhesive connection. First and second nodes are provided. A liquid conductive epoxy mixture is provided between the first and second nodes. The liquid conductive epoxy mixture is formed by mixing a first liquid and a second liquid. The liquid conductive epoxy mixture has sufficient conductivity that a 15 mil length sample of the liquid conductive epoxy having cross-sectional dimensions of 50 mil by 2 mil has a resistance of less than about 100 ohms along its length between about 10 minutes and about 20 minutes of mixing the first and second liquids. The liquid conductive epoxy is cured to form a conductive adhesive connection between the first node and the second node. In yet another aspect, the invention encompasses an epoxy system. The epoxy system includes a first liquid comprising a hardener, a second liquid comprising a base epoxy, and a third liquid comprising a concentration of an ionic salt. The first, second and third liquids are configured to be mixed together to form a liquid epoxy which will cure to form a conductive adhesive bond.
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Kumar Krishna
Lake Rickie C.
Gupta Yogendra
Hamlin Derrick G.
Micro)n Technology, Inc.
Wells, St. John, Roberts Gregory & Matkin P.S.
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