Electrical resistors – With cooling gas or liquid circulation
Reexamination Certificate
1999-12-29
2001-01-30
Easthom, Karl D. (Department: 2832)
Electrical resistors
With cooling gas or liquid circulation
C338S206000, C338S208000, C338S329000, C338S322000, C338S325000
Reexamination Certificate
active
06181234
ABSTRACT:
BACKGROUND OF THE INVENTION
Conventional resistors dissipate heat through connecting pins and pads to a printed circuit board, and through their body to the environment. Other known very low value resistors utilize a planar resistor bonded to a metallic substrate with an insulating laminate for mounting on a heat sink. These existing resistors are not suitable for certain applications, such as a very low value high power resistor with a resistance of less than 1 milliohm which must carry high currents. Since the conventional resistors are constructed to conduct the heat generated in them mainly to the printed circuit, such resistors are not well suited for the absorption of high current, continuously or in pulses, without causing an excessive temperature rise of the printed circuit or an equivalent support on which it is mounted. Furthermore, the construction of conventional resistors are generally not suitable for mounting with low thermal resistance to a heat sink for further reduction of temperature rise, low inductance for high frequency applications.
Accordingly, a primary objective of the present invention is a provision of an improved monolithic heat sink resistor.
Another objective of the present invention is a provision of a very low value resistor.
A further objective of the present invention is a provision of a resistor which is useful for the absorption of high current, continuously or in pulses, without causing an excessive temperature rise.
Another objective of the present invention is the provision of a resistor to which an additional heat sink can be mounted with a low thermal resistance of the interface.
Another objective of the present invention is the provision of a resistor having low inductance for high frequency applications.
A further objective of the present invention is the provision of a monolithic resistor having terminal connections for accurate sensing of voltage drop.
These and other objections will become apparent from the following description of the invention.
SUMMARY OF THE INVENTION
A monolithic resistor with heat sinks is constructed of a plurality of metallic foil strips. The center strip is an elongated narrow strip of electrically resistive material, such as nickel chromium alloy. A wide strip of electrically and thermally conductive material, such as copper, is provided on each side of the resistive strip. A plurality of terminal pins are formed in the conductive strips. The terminal pins may be solder coated. The conductive strips have a substantial width, in comparison to the narrow width of the resistive strip, so as to function as a heat sink and increase the heat capacity for pulse applications. The high length to width ratio results in a low thermal resistance. Additional heat sinks may be connected to the conductive strips to further dissipate heat generated by the resistor.
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Advances in Connector Design Using Electron Beam Welded Strip, R. M. Grubb and D.W.M. Williams, Technical Materials, Inc., Lincoln RI (No Date).
EB-welded Dual-Metal Strip Aids Contact Fabrication, Reprinted Nov. 1978 issue of: Electronic Packaging and Production.
Smejkal Joel J.
Szwarc Joseph
Easthom Karl D.
Vishay Dale Electronics, Inc.
Zarley McKee Thomte Voorhees & Sease
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