Patent Application
20130120104
1. Field of the Invention
The present invention relates to a resistor, and more particularly, to a current sensing resistor.
2. Description of the Prior Art
Current sensing resistors have been used in the electronic industry for many years, and are formed on the basis of the Kelvin theory or the 4-wire theory. The current sensing resistor is mainly used for application of low resistance, and has the advantages of low temperature coefficient and high heat dissipation performance when compared with general resistors. A conventional current sensing resistor (such as the U.S. Pat. No. 5,999,085) adopts a structure where a metal plate with fixed resistance is a middle portion and each of the two opposite terminals of the plate is fixedly connected to a side portion with high electrical conductivity. Each of the pair of side portions has a slot, dividing each of the pair of side portions into a current terminal and a sensing terminal. The length of the slot may be used for deciding the stability of resistance of the current sensing resistor.
The conventional current sensing resistor is formed through the fixed connection of different materials of metal or alloy, which is time-consuming during manufacturing and is also difficult to control the material characteristics of the metal or alloy. Moreover, other methods such as soldering or adhering are inevitably used during the fixed connection process, and the use of extra materials renders that the conventional current sensing resistor is incapable of fully demonstrating the material characteristics of a resistor substrate. As a result, the stability of resistance of the current sensing resistor is affected.
Therefore, a current sensing resistor made through an integral molding method is required in the market, allowing such current sensing resistor to be formed by only one material of metal or alloy. Therefore, the characteristics of the metal or alloy may be fully demonstrated, and it will also be easier to select the corresponding metal or alloy according to the required resistor characteristics. In this manner, manufacturing is more convenient, and the stability of resistance of the current sensing resistor is further improved.
In order to achieve the above objectives and efficacies, the present invention adopts an innovative technical means and an innovative method.
An embodiment of the present invention provides a current sensing resistor, which is made by a highly electrically conductive metal plate, and the metal plate includes: a middle portion; a first portion, located at one side of the middle portion, having a first slot; and a second portion, located at the other side of the middle portion opposite to the first portion, having a second slot; where each of the first portion and the second portion is divided into a current terminal and a sensing terminal by the first slot and the second slot respectively, and the current terminals of the first portion and the second portion have a length that is greater than that of the sensing terminals of the first portion and the second portion; characterized in that the middle portion has a middle slot and the length of the middle slot can be used for controlling the stability of resistance for the current sensing resistor.
Another embodiment of the present invention provides a method for manufacturing a current sensing resistor, which includes: forming at least one resistor substrates on a highly electrically conductive metal plate through stamping, where the resistor substrate has a middle slot at a middle portion and has a slot at each of the two side portions of the middle portion; forming a passivation layer at the middle portion of the resistor substrate; and forming a conductive layer at the two side portions of the resistor substrate.
In order to make the aforementioned objectives, features and advantages of the present invention more comprehensible, exemplary embodiments with accompanying drawings are described in detail below.
a is a diagram of a relationship between the magnitude of current flowing through a current sensing resistor and the magnitude of resistance of the current sensing resistor according to an embodiment of the present invention;
b is a diagram of a relationship between the magnitude of current flowing through a conventional current sensing resistor and the magnitude of resistance of the conventional current sensing resistor;
c is a diagram of a relationship between the temperature and the magnitude of resistance of a current sensing resistor according to an embodiment of the present invention; and
Current flowing through the current sensing resistor 100 mainly passes through the current terminal 106. Therefore, the length of the current terminal 106 should be greater than that of the sensing terminal 108, and the length of the current terminal 106 is selected according to the magnitude of the current.
In an embodiment, the current terminal 106 and the sensing terminal 108 of the pair of side portions 104 may include a conductive layer (not shown), so that four terminals of the current sensing resistor 100 may be connected to an external circuit. In a preferable embodiment, the material of the conductive layer may include Cu, Ni or Sn.
In an embodiment, the material of the metal plate may have a low resistance coefficient and a low resistance-temperature coefficient. The material of the metal plate may be selected according to the characteristics (such as the resistance coefficient or the resistance-temperature coefficient) of the desired current sensing resistor 100. In a preferable embodiment, the material of the metal plate may include Cu—Mn alloy, Ni—Cu alloy or Mn—Cu—Sn alloy.
In another embodiment, the middle portion 102 may be covered with a passivation layer (not shown), for protecting a resistor body portion of the current sensing resistor 100. In a preferable embodiment, materials such as either resin or a high polymer material may be used for the passivation layer.
a is a measurement result according to an embodiment of the present invention, and a relationship between the resistance of the current sensing resistor 100 and the current passing through the current sensing resistor 100 is measured. An abscissa represents the current, and a unit thereof is ampere; an ordinate represents the magnitude of resistance of the current sensing resistor 100, and a unit thereof is milliohm. In the present invention, when the current passing through the current sensing resistor 100 is increased from 1 ampere to 30 amperes, the resistance of the current sensing resistor 100 is changed only by 0.004 milliohm.
In addition,
Referring to
In another embodiment, electrodes of the resistor may be connected to an external conductive element 406 in Step S46 of the method, such that the resistance of the current sensing resistor may be measured and/or the stability of resistance may be adjusted by controlling the length of a middle slot.
According to an embodiment of the present invention, the material of the metal plate 402 may include Cu—Mn alloy, Ni—Cu alloy or Mn—Cu—Sn alloy, and the conductive layer may be formed by plating Cu, Ni or Sn.
In another embodiment, in Step S44 of the method, a trademark, a resistance or a related pattern is marked on the passivation layer.
In another embodiment, Step S45 and Step S46 of the method may be interchanged, if required, and the above steps merely demonstrate one of the embodiments.
The technical content and features of the present invention have been described; however, persons of ordinary skill in the technical field of the present invention can still make variations and modifications without departing from the teachings and disclosure of the present invention. Therefore, the disclosed embodiments are not intended to limit the present invention. Modifications and variations made without departing from the present invention shall fall within the scope of the present invention as specified in the following claims.
100 Current sensing resistor
102 Middle portion
104 Side portion
106 Current terminal
108 Sensing terminal
110 Middle slot
402 Metal plate
404 Passivation layer
405 Conductive layer
406 Conductive element
| Number | Date | Country | Kind |
|---|---|---|---|
| 100141692 | Nov 2011 | TW | national |
