Form-in-place EMI gaskets
First Claim
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1. A method of making a form-in-place elastomeric EMI shielding gasket, comprising:
- extruding onto a substrate to be gasketed a free-form polymeric thermal additional cure system having a viscosity of from about 100,000 to about 10,000,000 centipoise, and including a resin selected from the group consisting of silicone, siloxane, thermoplastic elastomers and mixtures thereof and an electrically-conductive filler; and
curing the system under atmospheric pressure, thereby forming a gasket having bulk resistivity of less than about 0.050 ohm cm, a force/deflection value of from about 35 N/m to about 267 N/m, a shore A hardness of at most about 90 and a closure force of at most about 5 pounds/linear inch.
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Abstract
A form-in-place, electrically-conductive gasket is disclosed. The gasket, foamed, gelled or unfoamed is made of one or more elastomer resins, such as silicone urethane and/or thermoplastic block copolymers and is either filled with a conductive filler and lined onto a desired substrate or lined onto the substrate unfilled and then coated with a conductive outer layer, such as a silver filled elastomer or a conductive flocked layer. A process and system for making the gaskets are also disclosed.
86 Citations
28 Claims
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1. A method of making a form-in-place elastomeric EMI shielding gasket, comprising:
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extruding onto a substrate to be gasketed a free-form polymeric thermal additional cure system having a viscosity of from about 100,000 to about 10,000,000 centipoise, and including a resin selected from the group consisting of silicone, siloxane, thermoplastic elastomers and mixtures thereof and an electrically-conductive filler; and
curing the system under atmospheric pressure, thereby forming a gasket having bulk resistivity of less than about 0.050 ohm cm, a force/deflection value of from about 35 N/m to about 267 N/m, a shore A hardness of at most about 90 and a closure force of at most about 5 pounds/linear inch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
forming the polymeric thermal addition cure system by forming a mixture of a first species having a first functional group, a second species having a second functional group that is reactive with the first functional group in the presence of a catalyst and heat, a catalyst that catalyzes a reaction between the first and second functional groups, and the electrically-conductive filler.
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3. A method as in claim 2, wherein the forming step comprises:
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mixing together;
a first pre-mixed component including the first species, the electrically-conductive filler, and the catalyst; and
a second pre-mixed component including the first species, the second species, and the electrically-conductive filler.
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4. A method as in claim 3, further comprising:
prior to mixing together the first and second components, adding additional catalyst to the first pre-mixed component.
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5. A method as in claim 2, the catalyst having catalytic action that in the presence of heat catalyzes a reaction between the first and second functional groups, and the electrically-conductive filler inhibiting the catalyst to adversely affect the catalytic activity of the catalyst.
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6. A method as in claim 2, wherein the first species comprises a siloxane polymer including vinyl functional groups, the second species comprises a siloxane cross-linker including reactive hydrides, the electrically-conductive filler comprises a silver-based electrically-conductive filler, and the catalyst comprises a platinum catalyst.
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7. A method as in claim 1, wherein the electrically-conductive filler is a silver-based filler.
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8. A method as in claim 1, wherein the catalyst is a platinum catalyst.
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9. A method as in claim 1, the system further comprising a cure inhibitor.
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10. A method as in claim 1, the system further comprising polymeric microspheres.
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11. The method as in claim 1, wherein the polymeric thermal addition cure system and the substrate are essentially free of primer.
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12. The method as in claim 1, said extruding step comprising extruding onto a substrate the polymeric thermal addition cure system in the form of a bead having a cross-sectional area of from about 0.0004 in2 to about 0.15 in2.
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13. The method as in claim 1, wherein said heating step is carried out at atmospheric pressure.
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14. An EMI shielding gasket formed by the process of claim 1.
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15. The method according to claim 1, wherein the curing step includes curing the system to form a gasket having a shore A hardness of from about 5 to about 80.
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16. The method according to claim 1, wherein the curing step includes curing the system to form a gasket having a shore A hardness of from about 5 to about 40.
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17. The method according to claim 1, wherein the curing step includes curing the system to form a gasket having a closure force of at most about 3 pounds/linear inch.
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18. The method according to claim 1, when the curing stop includes curing the system to form a gasket having a closure force of at most about 1 pound/linear inch.
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19. The method according to claim 1, wherein the curing step includes curing the system to form a gasket in a shape of a bead having a cross-sectional area of from about 0.004 square inches to about 0.015 square inches.
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20. A process for forming a form-in-place conductive EMI shielding gasket on a substrate comprising the steps of:
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providing a substrate to be gasketed;
providing a supply of conductive gasket material comprising a conductive filled resin selected from the group consisting of silicone, siloxane, thermoplastic elastomers and mixtures thereof;
applying the free-form material to the substrate'"'"'s surface in a predetermined pattern; and
curing the material in place upon the substrate under atmospheric pressure to form a gasket having a shore A hardness of at most about 90, a force/deflection value of from about 35 N/m to about 267 N/m and a closure force of at most about 5 pounds/linear inch. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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Specification