JP2005072268A - Metallic resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a metallic resistor which can easily and surely mounted to the land of a standard chip component provided to a printed circuit board or the like and can obtain a predetermined resistance value with higher accuracy, and also to provide a method of manufacturing the metallic resistor. <P>SOLUTION: The metallic resistor comprises a rectangular resistance material 11 formed of an alloy for resistance, and electrodes 12, 12 formed of a metal material having higher conductivity bonded to both ends of the resistance material. These electrodes have thick portions 12a and thin portions 12b. The thick portion 12a of the electrode is arranged at the external side of the resistance material 11, while the thin portion 12b of the electrode is arranged at the internal side of the resistance material 11. The surface of the thin portion 12b of the electrode and the surface of the thin portion 11b of the resistance material between the electrodes 12, 12 are covered with an insulating material 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a current detection resistor suitable for detecting, for example, a large current with high accuracy and a method for manufacturing the same, and in particular, a metal in which an electrode made of a high conductivity metal is joined to a resistor made of a resistance alloy. The present invention relates to a resistor structure and a manufacturing method thereof.

It is widely known to use a metal resistor having a very small resistance value on the order of milliohms for detecting a large current. In the detection of a large current using this metal resistor, Ohm's law I is obtained by measuring a voltage drop V across the resistor when a current I is passed through a resistor having a known low resistance value R. = V / R
Can be used to detect the current value I.

  As an example of such a metal resistor, one shown in FIG. 4 is known (see Patent Document 1). In this metal resistor, electrodes 12 and 12 made of a metal having a high conductivity are disposed on both ends of a rectangular resistor 11 made of a resistance alloy. Here, the electrodes 12 and 12 are for connecting to pads disposed on the printed circuit board by soldering, and a current is passed from a pad (current wiring) of the printed circuit board to the resistor, and both ends of the resistor are connected. The voltage generated in the circuit is taken out by a voltage detection wiring connected to a pad on the printed circuit board through an electrode.

JP 2002-57009 A

  By the way, the resistance value of the metal resistor as described above is mainly determined by the length and cross-sectional area of the resistor between the electrodes and the specific resistance of the material. For this reason, in order to obtain a required resistance value, it is necessary to adjust the length between both electrodes and the thickness of the resistor. However, the resistance value of the metal resistor is generally determined by a standard from a relatively low region to a high region. For this reason, when the resistance value is determined, the size of the electrode is limited by restrictions such as the specific resistance of the resistor material and the dimensions of the product.

  However, in general chip parts that are surface-mounted on a printed circuit board, there are standard electrode pad dimensions and inter-pad spacings corresponding to each size. For this reason, there is a problem that the electrode size and the interval for obtaining the required resistance value as described above cannot be matched, and the mounting position of the resistor is shifted during surface mounting.

  The present invention has been made in view of the above circumstances, and can be easily and surely mounted on a land of a standard chip part provided on a printed circuit board or the like, and can provide a required resistance value with high accuracy. An object of the present invention is to provide a metal resistor that can be obtained and a method for manufacturing the same.

  The metal resistor of the present invention is a metal resistor comprising a rectangular resistor made of a resistance alloy and electrodes made of a high conductivity metal joined to both ends of the resistor, Has a thick part and a thin part. Here, the thick part of the electrode is disposed outside the resistor, and the thin part of the electrode is disposed inside the resistor. The surface of the thin part of the electrode and the surface of the resistor in between are preferably covered with an insulating material, and the boundary between the thick part and the thin part of the electrode is connected by a surface having a radius of curvature. Preferably, the resistor is formed with a thin portion between both electrodes arranged at both ends thereof, and the thin portion is a wall having a radius of curvature and serving as a joint portion of the electrode of the resistor. It is preferable to be connected to the thick part.

  According to the present invention, the electrode is provided with a thick part and a thin part. Thereby, the size and interval of the thick part can be adapted to the pad size of a standard chip part. In addition, a metal resistor having an arbitrary resistance value can be manufactured depending on the size of the entire electrode including the thin portion. Therefore, it is possible to arbitrarily set the size of the electrode as a whole in order to adjust the resistance value, etc., and it is possible to obtain a resistor with an arbitrary high-precision resistance value, as well as an electrode for mounting the electrode. The size of the thick part can be adapted to the size of the electrode pad of the standard chip part. Therefore, when mounting the metal resistor, there is no problem that the land pattern and the electrode cannot be matched, and there is no problem that the mounting position is shifted, and stable mounting is possible.

  Further, by connecting the thin portion of the resistor to the thick portion of the resistor with a surface having a radius of curvature, current concentration at the connection portion can be avoided. Moreover, since the thickness of a resistor can be ensured by connecting on a surface having a radius of curvature, thermal conductivity can be ensured. Further, by connecting the thin part of the electrode to the thick part with a surface having a radius of curvature, the thermal conductivity is improved and the characteristic is stabilized.

  In the metal resistor manufacturing method of the present invention, a high-conductivity metal plate serving as an electrode is joined to a resistor composed of a resistance alloy, and a central portion of a portion serving as a rectangular resistor is cut. By removing the metal plate body in that portion, forming a thin portion in the resistor, and cutting a part of the metal plate adjacent to the thin portion of the resistor from the high conductivity metal A thin portion is formed on the electrode. Here, the thin portion of the resistor is preferably connected to the thick portion of the resistor at a surface having a radius of curvature, and the thin portion of the electrode is connected to the thick portion of the electrode at a surface having a radius of curvature. It is preferable to cut to connect.

  According to the present invention, a high-precision metal resistor having an arbitrary resistance value is provided with an electrode (thick part) corresponding to the pad size of a standard chip component, so that surface mounting can be performed easily and accurately. The effect is that it can be done. In general, according to the present invention, there is an effect that a high-precision metal resistor having good mountability can be easily manufactured at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 shows a state in which a metal resistor according to an embodiment of the present invention is mounted on a printed circuit board, and FIGS. 2A and 2B show cross-sectional and bottom surface configuration examples of the metal resistor. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same function, and the duplicate description is abbreviate | omitted.

  As shown in FIG. 1 and FIG. 2 (a), a metal resistor 10 includes a rectangular resistor 11 made of a resistance alloy, and a high-conductivity metal bonded to both ends of the back side of the resistor by clad bonding. The electrodes 12 and 12 which consist of are provided. Here, as a resistance alloy, copper / nickel alloy, nickel / chromium alloy, iron / chromium alloy, manganese / copper / nickel alloy, platinum / palladium / silver alloy, gold / silver alloy, gold / platinum / silver alloy, Etc. are used. Further, copper is preferable as the high conductivity metal constituting the electrode 12.

  The electrode 12 includes a thick portion 12a disposed on the outside of the resistor and a thin portion 12b disposed on the inside thereof. The resistor 11 is provided with a recess 13 between the thin portions 12b and 12b of both electrodes, and this portion is the thin portion 11b of the resistor, and the other portions are the thick portions 11a and 11a. Molten solder layers 17 and 17 are disposed on the lower surfaces of the thick portions 12a and 12a of the electrodes to improve the solderability.

  The surfaces of the thin portions 12b and 12b of the electrode and the thin portion 11b of the resistor are covered (undercoated) with an insulating material 15 such as polyimide resin. Similarly, the upper surface (surface) of the resistor 11 is also covered with an insulating material (top coat) 16 such as an epoxy resin. These insulating materials play a role as an insulating protective layer. The top coat 16 may be omitted.

  The metal resistor 10 is mounted on the printed board 21. That is, the printed circuit board 21 is provided with land patterns 22 and 22, and the thick portions 12a and 12a of the electrode 12 are joined to the portions by, for example, a reflow process of cream solder. Here, the current supply wiring 22 a and the voltage detection wiring 23 are connected to the land pattern 22.

Therefore, a current flows from the current supply wiring 22a to one electrode 12 of the metal resistor 10, a current flows through the resistor 11, and the current supply wiring 22a connected to the other land pattern from the other electrode 12 flows. Current flows out. The voltage of the resistor formed by the flow of this current is taken out by the voltage detection wirings 23 and 23 connected to the land pattern 22. Therefore, in detecting the current I, the relationship between the detected resistance V and the known resistance value R of the metal resistor is
I = V / R
Thus, the magnitude I of the current value can be obtained.

  Here, in this metal resistor, the size of the electrode thick portion 12a is adjusted to the size of the land pattern 22 of the standard chip component, and the distance between the electrode thick portions 12a and 12a is set to the land pattern of the standard chip component. The distance between 22 and 22 is adjusted. Therefore, when the printed circuit board 21 is provided with a land pattern of standard chip parts at the time of mounting, the positions of the electrodes 12 and 12 of the metal resistor 10 can be accurately aligned with the positions of the land patterns 22 and 22. Therefore, it is possible to prevent adverse effects such as misalignment caused by the conventional deviation of the electrode of the metal resistor from the size of the land pattern of a standard chip component.

  2A and 2B show structural examples of a metal resistor in which an electrode thin portion is formed. As described above, the metal resistor 10 adjusts the size of the thick portions 12a and 12a of the electrode 12 to the size of the land pattern of the standard chip component, and also adjusts the interval to the interval of the land pattern of the standard chip component. It is a thing. For example, in the case of a “2B” size chip part, A = 1.6 mm and B = 3.2 mm. In this case, the size and interval of the land pattern of the standard chip component are approximately as shown in FIG.

  In this metal resistor, if the size of the standard land pattern of the standard chip size of A × B is approximately A × D, the size of the electrode thick portion 12a is set to A × D according to this, and the interval is set to E in accordance with the interval of the standard land pattern.

On the other hand, the overall size of the electrode 12 is determined by the required resistance value R of the resistor, the specific resistance ρ of the resistor material, the size A × B of the resistor, and the like. Here, when the thickness of the thin portion 11b of the resistor 11 is t, the resistance value R of the resistor is substantially the cross-sectional area (A × t) of the resistor between both electrodes, the length F, It is determined from the specific resistance ρ. That is,
R = ρ · F / (A × t)
It becomes.

  Therefore, in this metal resistor 10, the distance F between the electrodes 12, 12 is determined in consideration of the specific resistance ρ of the resistor material from the required resistance value R and the thickness t and width A of the resistor thin portion 11b. Can be determined. That is, the interval F can be freely set in consideration of the resistance value and the ease of trimming. The distance E between the electrode thick portions 12a and 12a can be determined according to the size and position of the land pattern of the standard chip component. Thereby, it is possible to design a metal resistor having an electrode thick portion having an arbitrary resistance value and matching the size and interval of the land pattern of the standard chip part. A resistor having a highly accurate resistance value can be manufactured by accurately trimming the thickness t and the width A.

  Next, the curved surface provided at the boundary between the thick part and the thin part of the resistor will be described. That is, the resistor 11 is formed with a recess 13 (thin portion 11b) between the electrodes 12 and 12 disposed at both ends thereof, and the thin portion is joined to the resistor electrode 12 with a surface having a radius of curvature r. It is connected to the thick part 11a which is a part. By connecting the thin portion to the thick portion on the surface having the curvature radius r, current concentration can be avoided and the characteristics can be stabilized. That is, in the case of the conventional example shown in FIG. 4, since a corner portion is formed in this portion, there is a problem that current concentrates in this portion and heat is generated, which is a cause of deteriorating characteristics. Connecting with a surface having a radius of curvature r improves the uniformity of current distribution, prevents local heat generation, and stabilizes the current path to prevent fluctuations in resistance and floating inductance. Is possible.

  Similarly, since the boundary between the electrode thick portion 12a and the thin portion 12b is connected by a surface having a curvature radius r ′, the uniformity of the current distribution can be similarly improved and the heat conduction efficiency can be improved. Can do.

  Next, a method for manufacturing the metal resistor will be described with reference to FIG. First, as shown in FIG. 3A, a high conductivity metal plate (for example, copper) 32 is fixed to a resistor made of a resistance alloy (for example, copper / nickel alloy) by clad bonding. Clad bonding is the fusion of dissimilar metals under uniform pressure, which provides a strong mechanical connection and an electrically uniform bonding surface. A metal resistor having a stable current distribution can be obtained. In the figure, only one portion to be a resistor is shown, but a resistor and a metal plate to be an electrode are formed in a long shape (hoop shape) and cut appropriately in the subsequent steps. Preferably, individual resistors are used.

  Next, as shown in FIG. 3B, an insulating material coating (top coat) 33 made of, for example, an epoxy material is formed on the upper surface of the resistor 31. Note that the covering 33 may be omitted, and in this case, this step is of course omitted. Next, as shown in FIG.3 (c), the molten solder layer 34 is formed in the lower surface of the metal plate 32 used as an electrode. Of course, the molten solder layer 34 may be formed prior to the formation of the top coat 33.

  Next, as shown in FIG. 3D, first cutting for resistance value adjustment and electrode separation is performed. That is, as described above, in order to obtain the required resistance value R, cutting with a grinder or the like so as to obtain the required width F and resistor thickness t, the molten solder layer 34 in that portion, and the metal that becomes the electrode A part of the plate 32 and the resistor 31 is removed. Here, it is preferable to use a grinder or the like having a radius of curvature r at the edge portion, whereby the boundary portion between the thick portion and the thin portion of the resistor 31 is connected by a surface having the curvature radius r.

  Next, as shown in FIG. 3E, second cutting for adjusting the size (A × D) of the electrode thick portion and the interval E is performed. That is, the metal plate 32 serving as an electrode is cut using a grinder or the like so as to form an interval (distance) E between the electrode thick portions 12a and 12a shown in FIG. The solder layer 34 and the metal plate 32 are removed. Thereby, the electrode thin parts 12b and 12b are formed, and it is preferable that the thin part 12b and the thick part 12a are connected by a surface having a curvature radius r '. The surface having the curvature radius r ′ can be formed by providing a portion having the curvature radius r ′ at the edge portion of the grinder, for example. The thickness to be removed must be selected so that the thickness of the thin portion does not affect the uniformity of the current distribution. Of course, the order of steps shown in FIGS. 3D and 3E may be reversed.

  Next, as shown in FIG. 3F, a protective film (undercoat) 15 made of an insulating material made of polyimide or the like is formed on the surfaces of the electrode thin portion 12b and the resistor thin portion 11b exposed by cutting. Thereby, the upper surface of the resistor 31 (11) is provided with an insulating material coating (top coat) 33 (16), the lower surface of the resistor is provided with an electrode 32 (12) having a thick portion and a thin portion, and the electrode A metal resistor having a thickness (A × D) and an interval E in the thickness portion and adapted to the electrode pad size of a standard chip component can be manufactured. In addition, the cutting process which makes each metal resistor from the joined body of a hoop-shaped board | plate material can be performed by either of process (c) thru | or (f), for example.

  In addition, the said embodiment described the one aspect | mode of the Example of this invention, Of course, a various deformation | transformation Example is possible, without deviating from the meaning of this invention.

It is a perspective view which shows the state which mounted the metal resistor of embodiment of this invention in the printed circuit board. 1A is a cross-sectional view, FIG. 1B is a bottom view, and FIG. 1C is a plan view showing an example of a land pattern. It is sectional drawing which shows the outline | summary of the manufacturing process of the metal resistor shown in FIG. It is sectional drawing which shows the structural example of the conventional metal resistor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal resistor 11, 31 Resistor 11a Thick part 11b Thin part 12, 32 Electrode (metal plate body)
12a Thick part 12b Thin part 15 Insulating material (undercoat)
16, 33 Insulation material (top coat)
17, 34 Molten solder layer

Claims (10)

A metal resistor comprising a rectangular resistor made of a resistance alloy, and electrodes made of a high conductivity metal bonded to both ends of the resistor,
The metal resistor comprising a thick part and a thin part.   2. The metal resistor according to claim 1, wherein a thick portion of the electrode is disposed outside the resistor, and a thin portion of the electrode is disposed inside the resistor.   3. The metal resistor according to claim 2, wherein the surface of the thin portion of the electrode and the surface of the resistor between the electrodes are covered with an insulating material.   The metal resistor according to claim 1, wherein a boundary between the thick part and the thin part of the electrode is connected by a surface having a radius of curvature.   The resistor is formed with a thin portion between both electrodes disposed at both ends thereof, and the thin portion is connected to a thick portion which is a joint portion of the electrode of the resistor with a surface having a radius of curvature. The metal resistor according to claim 1, wherein: Bonding a highly conductive metal plate to be an electrode to a resistor made of a resistance alloy,
By cutting the central portion of the portion to be a rectangular resistor, the metal plate body of the portion is removed and a recess is formed in the resistor,
A part of the metal plate adjacent to the concave portion of the resistor is cut to remove the metal plate at that portion, and a thin part is formed on the electrode made of the metal plate with high conductivity. A method of manufacturing a metal resistor.   The metal resistor manufacturing method according to claim 6, wherein the thin portion of the resistor is connected to the thick portion of the resistor through a surface having a radius of curvature.   The method of manufacturing a metal resistor according to claim 6, wherein the thin portion of the electrode is connected to the thick portion of the electrode at a surface having a radius of curvature.   7. The method of manufacturing a metal resistor according to claim 6, wherein after forming the thin part of the electrode, the thin part of the resistor and the thin part of the electrode are covered with an insulating material.   The method of manufacturing a metal resistor according to claim 6, wherein a surface of the resistor is covered with an insulating material.

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