Electrical resistors – Mechanically variable – Resistance value varied by removing or adding material
Reexamination Certificate
1999-11-16
2001-02-06
Easthom, Karl D. (Department: 2832)
Electrical resistors
Mechanically variable
Resistance value varied by removing or adding material
C338S330000, C338S206000, C338S280000
Reexamination Certificate
active
06184775
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to surface mount resistors. More particularly, it relates to current sense resistors using a metal element. Still more particularly, though not exclusively, the present invention relates to surface mount resistors having an increased mechanical strength.
2. Problems in the Art
Surface mount resistors have been produced in the electronics industry. Their construction has typically been comprised of a flat rectangular resistive metal strip with high conductivity metal terminals welded to the ends of the resistive metal strip to form the electrical termination points. The resistive metal strip may be “adjusted” to a desired resistance value by abrading or by using a laser to remove some of the resistive material. A protective coating, for example epoxy, is then applied over the resistive material to provide protection from various environments to which the resistor may be exposed as well as providing strength to the resistor.
Typical prior art resistors are adjusted to a desired resistance by making lateral plunge cuts from the sides of the resistor material making a serpentine-type pattern. While these plunge cuts result in a resistor with a desired resistance, the lateral cuts across the face of the resistor degrade the mechanical strength of the device, in particular, the beam strength of the device. In some applications, it is desirable to put a physical load on the resistor across the face of the resistive metal. With the prior art employing lateral plunge cuts across the resistive metal, substantially all of the structural strength comes from the epoxy coating rather than the resistive metal. Therefore, it can be seen that there is a need for an improved surface mount resistor having an increased beam strength while still allowing the resistance of the resistor to be adjusted.
Features Of The Invention
A general feature of the present invention is the provision of an improved surface mount resistor and method for making the same which overcomes problems found in the prior art.
A further feature of the present invention is the provision of an improved surface mount resistor and method for making the same having a resistance determined by a pattern of intervening squares.
A further featured of the present invention is the provision of an improved surface mount resistor and method for making the same having a resistance generated with a series of axial cuts in the resistive material.
Further features, objects and advantages of the present invention include:
An apparatus and method for an improved surface mount resistor which utilizes a metal resistant strip or metal resistant film to achieve very low resistance values and high resistant stability.
An apparatus and method for an improved surface mount resistor which has a resistance value determined by the number of square patterns in the current path of the resistor.
An apparatus and method for an improved surface mount resistor which has an increased beam strength as a result of a carefully selected pattern including primarily axial cuts rather than lateral cuts.
An apparatus and method for an improved surface mount resistor which can have a wide array of possible values depending on the pattern of intervening squares generated on the resistor.
An apparatus and method for an improved surface mount resistor which incorporates all of the above features and maintains a surface mount design.
An apparatus and method for an improved surface mount resistor which is economical in manufacture, durable in use, and efficient in operation.
An apparatus and method for an improved surface mount resistor which is easily solderable on a surface mount board.
These as well as other objects, features and advantages will become apparent from the following specification and claims.
SUMMARY OF THE INVENTION
The improved surface mount resistor of the present invention is comprised of a piece of resistive material and two conductive metal pieces metallurgically bonded to the edges of the resistive material. A current path is formed through the resistive material between the conductive metal pieces. Any necessary lateral cuts are restricted to the ends where the beam bending moment is minimal. The current path is formed by making primarily axial cuts into the resistive material such that the beam strength of the resistive material is substantially maintained. The current path may optionally be formed by a plurality of squares where the number of squares determines the resistivity of the surface mount resistor.
REFERENCES:
patent: 2736785 (1956-02-01), Du Bois
patent: 3947801 (1976-03-01), Bube
patent: 4146673 (1979-03-01), Headley
patent: 4268954 (1981-05-01), Sease et al.
patent: 4284970 (1981-08-01), Berrin et al.
patent: 4429298 (1984-01-01), Oberholzer
patent: 4529958 (1985-07-01), Person et al.
patent: 4532005 (1985-07-01), Evans et al.
patent: 4684916 (1987-08-01), Ozawa
patent: 5166656 (1992-11-01), Badihi et al.
patent: 5218334 (1993-06-01), Bartlett
patent: 5287083 (1994-02-01), Person et al.
patent: 6007755 (1999-12-01), Hoshii et al.
Hoffman, “Quick Trim High Aspect Resistor”, IBMTDB, V. 22, No. 5, Oct. 1979 ,p. 1805.
Gerber George V.
Smejkal Joel J.
Easthom Karl D.
Vishay Sprague, Inc.
Zarley McKee Thomte Voorhees & Sease
LandOfFree
Surface mount resistor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surface mount resistor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surface mount resistor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2584075