The present invention relates to a resistor manufacturing method, and a resistor.
Patent Literature 1 discloses an invention that relates to a resistor, and a method of manufacturing the resistor. The resistor disclosed in Patent Literature 1 includes a resistive body, electrode plates which are positioned at both sides of the resistive body, respectively, and bent toward the lower surface side of the resistive body, and an electrically non-conductive filler interposed between the resistive body and the electrode plates.
The filler serves to adhere the resistive body to the electrode plates. In the resistor as disclosed in Patent Literature 1, heat propagates from the resistive body to the electrode plates via the filler to secure a heat dissipation property.
Patent Literature 1: Japanese Patent No. 4806421
In Patent Literature 1, the filler in the uncured and unsolidified state is disposed on the surface of the resistive body, and the electrode plates are bent to be in contact with the filler. Thereafter, the filler is cured and solidified.
In Patent Literature 1, as the filler in contact with the bent electrode plates is uncured, the filler exhibits high fluidity. The high fluidity is likely to cause the thickness variation of the filler between the resistive body and the electrode plates. Accordingly, the resistor disclosed in Patent Literature 1 has a problem that the heat dissipation property or adhesive strength is likely to vary.
The present invention has been made in consideration of the above-described problem. Especially, it is an object of the present invention to provide a resistor manufacturing method, and a resistor for suppressing the thickness variation of the thermally conductive layer intervening between the resistive body and the electrode plates.
A resistor manufacturing method according to the present invention includes a step of forming an uncured first thermally conductive layer on a surface of a resistive body, a step of curing the first thermally conductive layer, a step of laminating an uncured second thermally conductive layer on a surface of the first thermally conductive layer, and a step of bending electrode plates respectively disposed at both sides of the resistive body, curing the second thermally conductive layer, and performing adhesion between the resistive body and the electrode plates via the first thermally conductive layer and the second thermally conductive layer.
A resistor according to the present invention includes a resistive body, electrode plates which are respectively disposed at both sides of the resistive body, and bent toward a lower surface side of the resistive body, and a plurality of cured thermally conductive layers intervening between the resistive body and the electrode plates.
Unlike the generally employed method, a resistor manufacturing method according to the present invention ensures that the thickness variation of a thermally conductive layer between a resistive body and electrode plates is suppressed. The method allows manufacturing of a resistor while suppressing variation in the heat dissipation property and the adhesive strength.
An embodiment according to the present invention (hereinafter simply referred to as an “embodiment”) will be described in detail. The present invention is not limited to the following embodiment, but may be implemented in various modifications within a scope of the present invention.
(Resistor Manufacturing Method)
Referring to the drawings, a resistor manufacturing method of the embodiment will be described in the order of the manufacturing steps.
In steps as shown in
In the step as shown in
In the embodiment, each thickness of the resistive body 2 and the electrode plate 3 is not limited. For example, the resistive body 2 may be formed to have the thickness ranging from several tens of μm to several hundreds of μm approximately. The resistive body 2 may be formed to have substantially the same thickness as, or different thickness from that of the electrode plate 3.
In the embodiment, existing material may be used for forming the resistive body 2 and the electrode plate 3 in a non-restrictive manner. For example, it is possible to use metal resistance material such as copper-nickel and nickel-chrome, a structure formed by applying a metal film onto the surface of an insulating base, a conductive ceramic substrate and the like for forming the resistive body 2. For example, it is possible to use copper, silver, nickel, chrome, and composite material thereof for forming the electrode plate 3.
When bonding the electrode plates 3 to both sides of the resistive body 2, respectively, each end surface of the resistive body 2 may be brought into abutment on the corresponding end surface of the electrode plates 3 as shown in
The resistive body 2 and the electrode plates 3 may be integrally formed. That is, it is possible to use the single metal resistance plate as the same material for forming the resistive body 2 and the electrode plates 3. Alternatively, plating of the metal material with low resistance is applied to the region to be formed as the electrode plate 3 on the metal resistance plate so that the electrode plate 3 is formed on the surface of the metal resistance plate.
In the steps as shown in
The uncured first thermally conductive layer 4 may be in the form of a film or a paste. In the case of the film, the uncured thermally conductive resin film is stuck on the surface of the resistive body 2. In the case of the paste, the uncured thermally conductive resin paste is applied to or printed on the surface of the resistive body 2. Alternatively, the first thermally conductive layer 4 may be formed by executing the inkjet process.
In the embodiment, the thickness of the first thermally conductive layer 4 is not limited. The thickness may be arbitrarily specified in consideration of the thermal conductivity of the resistor as the finished product, and secure fixation between the resistive body and the electrode plates. Especially, in the embodiment, there are two or more thermally conductive layers to be interposed between the resistive body and the electrode plates. It is therefore preferable to adjust the thickness of the first thermally conductive layer 4 in consideration of the number of layers. For example, preferably, the thickness of the first thermally conductive layer 4 is in the range from approximately 20 μm to 200 μm.
The term “uncured” refers to the state where the layer is not cured completely. Specifically, the uncured state where the layer has not been completely cured represents that curing reaction hardly proceeds to exhibit fluidity at the same level as that in the initial formation stage, or the state of the purchased product for shipment. The term “cured (completely cured)” refers to the state where the layer has lost the fluidity owing to accelerated polymerization due to linkage of molecules. For example, when the first thermally conductive layer 4 is formed as the thermally conductive resin film, the pre-processing (temporary crimping) is executed after placing the first thermally conductive layer 4 on the resistive body 2 as shown in
When using the thermally conductive resin film for the first thermally conductive layer 4, the first thermally conductive layer 4 is in the uncured and solidified state. The term “solidified” refers to the state of having become solid.
Meanwhile, when using the thermally conductive resin paste for the first thermally conductive layer 4, the first thermally conductive layer 4 is in the uncured and unsolidified state. The term “unsolidified” refers to the state where the solid component is partially or entirely dispersed in the solvent such as slurry and ink.
In the embodiment, the first thermally conductive layer 4 may be formed only on the surface of the resistive body 2 as shown in
As
Then the heating process is applied to the uncured first thermally conductive layer 4 for complete curing. At this time, the use of the thermally conductive resin paste for the first thermally conductive layer 4 may facilitate solidification and curing. The determination whether or not the layer has been completely cured may be made in accordance with the cure degree, viscosity, thermal processing condition and the like. It is possible to use the cure degree to be calculated from the calorific value derived from the measurement utilizing the differential scanning calorimeter. Complete curing refers to the condition where the cure degree is equal to or higher than 70%, or refers to the condition generally called stage C.
As the uncured first thermally conductive layer 4 is cured, the thermally conductive layer having the film thickness hardly fluctuating is securely formed on the surface of the resistive body 2, or on the surfaces of the resistive body 2 and the electrode plates 3 before the electrode plates 3 are bent in the subsequent step.
Although it is not intended to limit the thermal processing condition for completely curing the first thermally conductive layer 4, it is preferable to apply the heating process to the first thermally conductive layer 4 at the temperature ranging from approximately 150° C. to 250° C. for approximately 0.5 to 2 hours. The heating temperature and the heating time required for curing may vary depending on the material for forming the first thermally conductive layer 4. If the first thermally conductive layer 4 is the purchased product, the curing condition is specified in accordance with the heating temperature and the heating time as prescribed by the manufacturer. For example, the heating temperature and the heating time of the resin used for the experiment to be described later are specified to be in the range from approximately 160° C. to 200° C., and approximately 70 to 30 minutes (the lower the heating temperature becomes, the longer the heating time is set) for appropriate adjustment.
In the embodiment, subsequent to the step as shown in
In the embodiment, it is possible to use either the same or different material for forming the first thermally conductive layer 4 as or from the material for the second thermally conductive layer 5. It is also possible to use the thermally conductive resin film, or the thermally conductive resin paste for the second thermally conductive layer 5. Accordingly, the second thermally conductive layer 5 formed as the thermally conductive resin film is in the uncured and solidified state. Meanwhile, the second thermally conductive layer 5 formed as the thermally conductive resin paste is in the uncured and unsolidified state.
In an exemplified case, the thermally conductive resin film may be used for the first thermally conductive layer 4, and the thermally conductive resin film or the thermally conductive resin paste may be used for the second thermally conductive layer 5. For example, it is preferable to use the same thermally conductive resin film for both the first thermally conductive layer 4 and the second thermally conductive layer 5 for improving productivity of the resistor.
The total value of thicknesses of the first thermally conductive layer 4 and the second thermally conductive layer 5, which are laminated is appropriately adjusted so that the interval between the resistive body 2 and the electrode plates 3 is brought into a predetermined range after the electrode plates 3 are bent in the subsequent step.
When using the thermally conductive resin film for the second thermally conductive layer 5, the pre-processing is executed as described above so that the second thermally conductive layer 5 is fixed to the first thermally conductive layer 4.
As
As the belt-like bonded body 1 as shown in
The resistor intermediate 10 is constituted by the resistive body 2 having a rectangular outer shape, and the electrode plates 3 each having a rectangular outer shape provided at the respective sides of the resistive body 2. The outer shape of the resistor intermediate 10 as shown in
As
As
As
Meanwhile, likewise the structure as shown in
The second thermally conductive layer 5 in the uncured state is heated to be completely cured. The term “complete curing” refers to the explanation that has been already described as above.
In the embodiment, it is preferable to completely cure the second thermally conductive layer 5 while pressing the bent electrode plates 3 toward the resistive body 2. That is, as
Then in the step as shown in
It is possible to affix a seal on the surface of the surface protective layer.
As
(Resistor)
The resistor 11 manufactured through the above-described manufacturing steps includes the resistive body 2, the electrode plates 3 disposed at both sides of the resistive body 2, respectively while being bent at the lower surface side of the resistive body 2, and the plurality of cured thermally conductive layers 4, 5 intervening between the resistive body 2 and the electrode plates 3 as shown in
A total value of thicknesses of the plurality of thermally conductive layers 4 and 5 that intervene between the resistive body 2 and the electrode plates 3 ranges from approximately 50 μm to 150 μm. Each thickness of the thermally conductive layers 4, 5 is adjusted to have the total thickness thereof within the above-described range so that heat dissipation property from the resistive body 2 to the electrode plates 3 via the thermally conductive layers 4, 5 may be appropriately improved. That is, compared with the case where the thermally conductive layer is constituted by the single layer, the thermally conductive layers 4, 5 of the embodiment allow the thickness between the resistive body 2 and the electrode plates 3 to be made more uniform, and variation in the heat dissipation property may also be suppressed. This makes it possible to provide the resistor 11 with improved heat dissipation property. The total value of thicknesses of the thermally conductive layers 4, 5 is adjusted to be within the above-described range to allow improvement in tight contactness between the resistive body 2 and the electrode plates 3. This makes it possible to appropriately prevent the failure such as peeling of the electrode plate 3 from the thermally conductive layer, or crack generated in the thermally conductive layer.
The resistor manufacturing method of the embodiment is characterized in that, after completely curing the first thermally conductive layer 4, the uncured second thermally conductive layer 5 is laminated on the first thermally conductive layer, and thereafter, the electrode plates 3 are bent, and the second thermally conductive layer 5 is cured.
Execution of the above-described manufacturing steps allows suppression of variation in each thickness of the thermally conductive layers 4, 5 between the resistive body 2 and the electrode plates 3 compared with the generally employed steps. That is, upon execution of the heating process after bending of the electrode plates 3, the first thermally conductive layer 4 of those thermally conductive layers has been already cured, thus hardly causing the film thickness fluctuation. At this time, the second thermally conductive layer 5 has been uncured. However, the second thermally conductive layer 5 partially constitutes the thickness between the resistive body 2 and the electrode plates 3. The variation in the thickness of the thermally conductive layer resulting from fluidity of the second thermally conductive layer 5 may be made smaller than the case where the entire thermally conductive layer between the resistive body 2 and the electrode plates 3 is in the uncured state.
As described above, in the embodiment, it is possible to suppress variation in the thickness of the thermally conductive layer between the resistive body 2 and the electrode plates 3. This makes it possible to make the thickness between the resistive body 2 and the electrode plates 3 further uniform, and to suppress variation in the heat dissipation property, thus manufacturing the resistor 11 with excellent heat dissipation property. The further uniform thickness between the resistive body 2 and the electrode plates 3 may suppress generation of a gap or the like between the resistive body 2 and the electrode plates 3, resulting in improved adhesive strength.
The uncured and solidified material, specifically, the thermally conductive resin film may be preferably used for forming at least any one of the first thermally conductive layer 4 and the second thermally conductive layer 5.
When using the uncured and unsolidified material, specifically, the thermally conductive resin paste for forming both the first thermally conductive layer 4 and the second thermally conductive layer 5, the thickness between the resistive body 2 and the electrode plates 3 is likely to vary. That is, intrinsically, the use of the thermally conductive resin paste is likely to vary the thickness in the state where the paste is applied. Consequently, the use of the thermally conductive resin film in the uncured and solidified state for forming at least one of the first thermally conductive layer 4 and the second thermally conductive layer 5 makes it possible to suppress the thickness variation between the resistive body 2 and the electrode plates 3 more effectively. The use of the thermally conductive resin film for forming both the first thermally conductive layer 4 and the second thermally conductive layer 5 allows adjustment of the thickness between the resistive body 2 and the electrode plates 3 so that the thickness is made further uniform.
For example, the thermally conductive resin film is used for forming the first thermally conductive layer 4 to adjust so that the thickness between the resistive body 2 and the electrode plates 3 is within a predetermined range. Meanwhile, the thermally conductive resin paste is thinly applied to form the second thermally conductive layer 5 to adhere the electrode plates 3. This makes it possible to easily adjust the thickness within the predetermined range while suppressing variation in the thickness between the resistive body 2 and the electrode plates 3, and to securely adhere the electrode plates 3.
In the steps as shown in
The present invention will be described in more detail based on an example implemented to exhibit the advantageous effect of the present invention. However, the present invention is not limited to the example as described below.
In an experiment, the following resin was used, and the thermal analysis was carried out using a differential scanning calorimeter (DSC).
[Resin]
Polyimide/Epoxy Resin
[Differential Scanning Calorimeter]
DSC8231 manufactured by Rigaku Corporation
The DSC curve and the DDSC curve were obtained at the temperature elevation rate of 10° C./min in the experiment.
As
In accordance with the experimental result, the applied temperature was measured to be in the range from 160° C. to 220° C.
The temperature was fixed to 170° C. to obtain the curing start temperature and the curing end temperature from the DSC curve in accordance with the holding time. The obtained experimental results are shown in
The above-described experimental result has clarified that the resin to be used as specified above was cured under the condition at 170° C. for approximately 60 minutes. The curing condition coincided with the curing condition recommended by the resin manufacturer.
As the curing condition is established at 170° C. for 60 minutes, the curing condition in the temperature range as shown in
The resistor according to the present invention with excellent heat dissipation property allows reduction in its height. The resistor may be surface mounted so as to be mounted to various types of circuit boards.
The present application claims priority from Japanese Patent Application No. JP2017-237820 filed on Dec. 12, 2017, the content of which is hereby incorporated by reference into this application.
Number | Date | Country | Kind |
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JP2017-237820 | Dec 2017 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2018/045456 | 12/11/2018 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2019/117127 | 6/20/2019 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4933811 | Dorlanne | Jun 1990 | A |
5563572 | Hetzler | Oct 1996 | A |
5802709 | Hogge | Sep 1998 | A |
6316726 | Hidaka | Nov 2001 | B1 |
7190252 | Smith | Mar 2007 | B2 |
8912876 | Gomi | Dec 2014 | B2 |
9728306 | Lu | Aug 2017 | B2 |
11011290 | Abe | May 2021 | B2 |
20060197648 | Smith | Sep 2006 | A1 |
20090224865 | Tanaka et al. | Sep 2009 | A1 |
Number | Date | Country |
---|---|---|
H11-162721 | Jun 1999 | JP |
2004-128000 | Apr 2004 | JP |
2008-532280 | Aug 2008 | JP |
4806421 | Aug 2011 | JP |
2015-008316 | Jan 2015 | JP |
2017-0074367 | Jun 2017 | KR |
Entry |
---|
International Search Report, dated Mar. 5, 2019 by the Japan Patent Office (JPO), in International Application No. PCT/JP2018/045456. |
Partial Supplementary European Search Report, dated Aug. 2, 2021, by the European Patent Office (EPO) in European Patent Application No. 18887518.1. |
Number | Date | Country | |
---|---|---|---|
20200395150 A1 | Dec 2020 | US |