Claims
- 1. A composite circuit protection device comprising(I) a laminar insulating member; (II) a first laminar circuit protection device; and (III) a second laminar circuit protection device; each of the first and second laminar circuit protection devices comprising (1) a first laminar electrode; (2) a second laminar electrode; (3) a laminar PTC resistive element which (i) exhibits PTC behavior, (ii) has a first face to which the first electrode is secured and an opposite second face to which the second electrode is secured, (iii) defines first and second apertures which run between the first and second faces, and (iv) is composed of a PTC conductive polymer; (4) a third laminar conductive member which (i) is secured to the second face of the PTC resistive element in the area of the first aperture, and (ii) is spaced apart from the second electrode; (5) a fourth laminar conductive member which (i) is secured to the first face of the PTC resistive element in the area of the second aperture, and (ii) is spaced apart from the first electrode; (6) a first transverse conductive member which (a) lies within the first aperture defined by the PTC resistive element, (b) runs between the first and second faces of the PTC element, (c) is secured to the PTC element, and (d) is physically and electrically connected to the first laminar electrode and to the third laminar conductive member, but is not connected to the second laminar electrode; and (7) a second transverse conductive member which (a) lies within the second aperture defined by the PTC resistive element, (b) runs between the first and second faces of the PTC element, (c) is secured to the PTC element, and (d) is physically and electrically connected to the second laminar electrode and to the fourth laminar conductive member, but is not connected to the first laminar electrode; the first and second laminar devices being physically secured together in a stacked configuration, with the laminar insulating member between them; the devices being connected together electrically by interfacial electrical connections which are solder joints composed of a first solder and are between(A) a third or fourth member of the first laminar device and a first or second electrode of the second laminar device, and (B) a third or fourth member of the second laminar device and a first or second electrode of the second laminar device so that when an electrical power supply is connected to (i) one of the electrodes and (ii) the third or fourth laminar member on the same face of the PTC resistive element as the electrode (i), the first and second laminar circuit protection devices are connected electrically in parallel;the composite device (1) being capable of flat connection onto a substrate free of leads, and (2) further comprising layers of a second solder on exposed surfaces of the first or second electrodes and the third and fourth laminar members, the second solder being reflowable at temperatures which do not melt the solder joints.
- 2. A composite device according to claim 1 wherein the first and second laminar circuit protection devices have substantially identical shapes, thicknesses, and resistive elements.
- 3. A composite device according to claim 2 which is symmetrical so that it can be connected either way up on a printed circuit board.
- 4. A composite device according to claim 1 which comprises p substantially identical laminar circuit protection devices, where p is 3 or more; and (p−1) laminar insulating members; the laminar devices being (a) secured together physically in a stacked configuration, with one of the laminating insulating members between each pair of laminar devices, and (b) connected together electrically so that when an electrical power supply is connected to (i) one of the electrodes, and (ii) the third or fourth member on the same face of the PTC resistive element as the electrode (i), all the laminar circuit protection devices are connected together electrically in parallel.
- 5. A composite device according to claim 1 wherein the PTC conductive polymer has a resistivity at 25° C. of less than 5 ohm-cm.
- 6. A composite device according to claim 1 wherein the PTC conductive polymer of the first circuit protection device comprises a different polymer or different filler, or has a different resistivity from the PTC conductive polymer of the second circuit protection device.
- 7. A composite device according to claim 1 wherein the laminar insulating member comprises an electrically non-conductive adhesive.
- 8. A device according to claim 2 wherein the first and second electrodes and the third and fourth laminar conductive members are metal foils.
- 9. A device according to claim 8 wherein each of the first and second transverse conductive members comprises a plating of a metal on the surface of the PTC resistive element which defines the aperture.
- 10. A device according to claim 1 wherein each of the apertures has an open cross section.
- 11. A device according to claim 1 wherein each of the first and second apertures has a cross section which is a half circle.
- 12. A device according to claim 1 wherein each of the first and second apertures has a cross section which is a quarter circle.
- 13. A device according to claim 1 which has a footprint of at most 20 mm2.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to commonly assigned U.S. patent application Ser. No. 08/900,787 filed Jul. 25, 1997 by Graves, Zhang, Chandler, Chan, Fang, Beadling, Siden and Thompson, now U.S. Pat. No. 5,825,397, issued Dec. 22, 1999. Ser. No. 08/900,787 is a continuation of U.S. patent application Ser. No. 08/727,869 filed Oct. 8, 1996, now abandoned, which is a continuation of U.S. patent application Ser. No. 08/302,138, filed Sep. 7, 1994, now abandoned, which is a continuation-in-part of (1) commonly assigned U.S. patent application Ser. No. 08/152,070, filed Nov. 12, 1993, by Graves, Zhang, Chandler, Chan and Fang, now abandoned, which is a file wrapper continuation of U.S. patent application Ser. No. 07/910,950, filed Jul. 9, 1992, now abandoned, and (2) commonly assigned U.S. patent application Ser. No. 08/121,717, filed Sep. 15, 1993, by Fang, Siden, Thompson and Zhang, now abandoned. This application is also related to International Application No. PCT/US93/06480, filed Jul. 8, 1993, by Raychem Corporation, now published as WO 94/01876, which claims priority from U.S. patent application Ser. No. 07/910,950; to commonly assigned U.S. patent application Ser. No. 08/242,916, filed May 16, 1994, by Zhang and Fang, now abandoned in favor of continuation application Ser. No. 08/710,925, now U.S. Pat. No. 5,831,510, issued Nov. 3, 1998, and to commonly assigned U.S. patent application Ser. No. 08/257,586, filed Jun. 9, 1994, by Zhang, Thompson, Toth and Beadling, now abandoned in favor of continuation application Ser. No. 08/808,135, now U.S. Pat. No. 5,864,281, issued Jan. 26, 1999.
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