Precision resistor fabrication employing tapped resistive elements
First Claim
1. A method of fabricating a resistor having a predetermined value of resistance within a precisely-predetermined tolerance range, comprising the following steps:
- (a) providing an elongated resistive element having a plurality of contact pads thereon, said pads having predetermined spacings along said element so as to divide said element into resistive segments, said resistive element constituting a first layer of resistive material, the portions of said first layer which constitute said control pads being covered by a second layer, said second layer being of a material which is different from that of said first layer and which is capable of being bonded to a connecting wire, said segments each having a resistance value which is less than said tolerance range,(b) measuring the resistance of a known number of segments from 1 to m, where m is a whole number, of said resistive segments,(c) calculating the number of said resistive segments necessary to attain said predetermined value of resistance, within a tolerance range equal to the value of resistance of one of said resistive segments, using as a basis the measured resistance of said known number of resistive segments,(d) indentifying a pair of said contact pads which are connected across said claculated number of resistive segments, and (e) connecting conductors to the pads so identified.
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Accused Products
Abstract
Thin film resistors (FIG. 1) are produced on flexible tape 1 to provide at low cost a very wide range of precision resistors having low inductance. A reel of tape 70 coated with resistive material is etched to create a plurality of sinuous resistor patterns 3 and an array of spaced interconnection pads 102 suitable for connection to external leads via intermediate wires. Formation of a resistor of the desired precision value is performed by a selection of two pads, preferably by automated means by a trial and error technique. Prior to pad selection, the resistor can be covered with a material 4 which provides stability of resistance, mechnical protection and facilitation of assembly.
25 Citations
36 Claims
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1. A method of fabricating a resistor having a predetermined value of resistance within a precisely-predetermined tolerance range, comprising the following steps:
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(a) providing an elongated resistive element having a plurality of contact pads thereon, said pads having predetermined spacings along said element so as to divide said element into resistive segments, said resistive element constituting a first layer of resistive material, the portions of said first layer which constitute said control pads being covered by a second layer, said second layer being of a material which is different from that of said first layer and which is capable of being bonded to a connecting wire, said segments each having a resistance value which is less than said tolerance range, (b) measuring the resistance of a known number of segments from 1 to m, where m is a whole number, of said resistive segments, (c) calculating the number of said resistive segments necessary to attain said predetermined value of resistance, within a tolerance range equal to the value of resistance of one of said resistive segments, using as a basis the measured resistance of said known number of resistive segments, (d) indentifying a pair of said contact pads which are connected across said claculated number of resistive segments, and (e) connecting conductors to the pads so identified. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of fabricating a resistor having a predetermined value of resistance within a precisely-predetermined tolerance range comprising the following steps:
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(a) providing an elongated resistive element having first and second sets of taps thereon, said first set being positioned on a first portion of said element the resistive segments between adjacent taps of said first set having a predetermined relatively large resistance so as to divide said element into a first set of resistive segments of relatively high resistance valve, and a second set being positioned on a second portion of said element adjacent said first set of taps and the resistive segments between adjacent taps of said second set having a relatively small resistance so as to divide said element into a second set of resistive segments of relatively low resistance, said second set of resistive segments each having a resistance value less than said predetermined tolerance range, (b) measuring the resistance of a first segment of said resistive element between a first pair of taps in said first set, (c) combining the resistance of sufficient successive additional tapped resistive segments adjacent said first pair of taps so as to attain a value of resistance roughly approximating said predetermined value within the range of the resistance value between adjacent taps of said first set, but less than said predetermined value, (d) measuring the resistance between a first pair of taps in said second set, (e) combining the resistance of sufficient additional tapped resistive segments adjacent said first pair of taps in said second set with the value of resistance attained in step (c) so as to attain a value of resistance finely approximating said predetermined value within the range of the resistance value between adjacent taps of said second set. (f) identifying the taps in said first and second sets which bound said value of resistance finely approximating said predetermined value, and (g) connecting conductors to the taps so identified. - View Dependent Claims (20)
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21. A method of fabricating a resistor having a predetermined value of resistance within a precisely-predetermined tolerance range, comprising the following steps:
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(a) providing an elongated resistive element having a plurality of contact pads thereon, said pads having predetermined spacings along said element so as to divide said element into resistive segments, said resistive element constituting a first layer of resistive material, the portions of said first layer which constitute said pad being covered by a second layer, said second layer being of a material which is different from said first layer and which is capable of being bonded to a connecting wire, said segments each having a resistance value which is less than said tolerance range, (b) contacting a pair of conductive probes respectively to a first of said pads and a second of said pads separated from said first pad by a predetermined spacing and a whole number of said resistive segments, (c) supplying a current through said resistive segments between said first and second pads via said conductive probes, (d) measuring the resistance of said resistive segments between said first and second pads by a calculation using the values of current flowing through and voltage across said resistive segments, (e) comparing the measured resistance of said segments with said predetermined value of resistance and (1) identifying said first and second pads if said measured resistance is within a given tolerance range of said predetermined value of resistance, or (2) moving said second probe to a pad different from said first and second pads if said measured resistance is outside said given tolerance range of said predetermined value of resistance, and repeating said steps (c) and (d) with said first pad and said different pad if the measured resistance therebetween is within said given tolerance range of said predetermined value of resistance, and (f) attaching connectors to the last pads identified. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A method of fabricating a resistor having a predetermined value of resistance which is extremely insensitive to temperature variations, comprising:
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(a) providing a pair of resistors in a common physical association such that both resistors of said pair will experience similar temperature changes in response to ambient temperature variations or self-induced heating, said resistors having temperature coefficients of resistivity of opposite signs, said resistors each including means for making an adjustment of its value of resistance within a predetermined range. (b) determining the temperature coefficient of resistivity of each of said resistors after said resistors are provided in said common physical association, (c) using said determined temperature coefficients of resistivity, computing a pair of values of resistances of said pair of resistors such that when said resistance values of resistance are combined in a predetermined manner, said predetermined value of resistance will be attained, and any temperature induced increase in the value of one of said resistors will be offset by a corresponding decrease in the value of the other of said resistors, and (d) adjusting the value of resistance of at least one of said resistors is that said resistors, when combined in said predetermined manner, will have said computed pair of values of resistance. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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Specification