JP2008277584A - Thermoelectric substrate member, thermoelectric module, and manufacturing method of them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric module capable of preventing lamination between a thermoelectric element and an electrode from being easily peeled off and having excellent reliability, to provide a thermoelectric substrate member to be used for the thermoelectric module, and to provide a method for manufacturing the thermoelectric module and the thermoelectric substrate member. <P>SOLUTION: Plurality of first and second electrodes 3, 4 are respectively formed on the opposite surfaces of first and second substrates 1, 2, and N-type thermoelectric elements 5 and P-type thermoelectric elements 6 are arranged so as to be held between the first electrodes 3 and the second electrodes 4. Further, stress buffer layers 7, 8 are respectively arranged between the first electrode 3 and the first substrate 1 and between the second electrode 4 and the second substrate 2. The electrodes 3, 4 are formed with copper plate layers and the substrates 1, 2 are formed with alumina or copper plates or the like. For the stress buffer layers 7, 8, polyimide resin, aramid resin, or epoxy resin can be used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermoelectric module in which a plurality of thermoelectric elements are provided and an object is electronically cooled or heat is converted into electric power by the Peltier effect or Seebeck effect, a thermoelectric substrate member used therefor, and a manufacturing method thereof.

  The thermoelectric module is composed of a p-type semiconductor and an n-type semiconductor microchip (thermoelectric element) containing at least two elements selected from the group consisting of Bi, Sb, Te, and Se on a ceramic substrate with patterned electrodes. The heat is converted into electric power by utilizing the Seebeck effect in which an electromotive force is generated when a temperature difference occurs between the contacts. Alternatively, a thermoelectric module cools or heats (electrically cools) an object by energization using the Peltier effect in which the flow of heat occurs in the same direction as or in the opposite direction to the direction of current by applying a voltage to the thermoelectric element. Is.

  In this case, in any type of thermoelectric module, there is a temperature difference between the thermoelectric elements assembled in the module, and due to the thermal stress between the thermoelectric element and the electrode or the substrate, Delamination becomes a problem.

  As a conventional electronic cooling element, an electronic cooling element is disclosed in which a substrate is made of a flexible resin sheet so as to match the shape of an object to be cooled (Patent Document 1). In the thermoelectric module described in this publication, electrodes 22 and 23 are respectively formed on opposing surfaces of substrates 20 and 21 made of a polyimide sheet so as to schematically show the structure of the thermoelectric module in FIG. The N-type thermoelectric element 24 and the P-type thermoelectric element 25 are connected to both ends in the longitudinal direction of the 22, and the two adjacent N-type thermoelectric elements 24 and the P-type thermoelectric element 25 disposed on the two adjacent electrodes 22. Are connected by a single electrode 23 facing each other, and thermoelectric elements 24 and 25 are connected in series. In this thermoelectric module, since the substrate is a polyimide sheet, it is flexible and is deformed in accordance with the shape of the object to be cooled.

  In addition, a thermoelectric module has been proposed in which an N-type thermoelectric element and a P-type thermoelectric element are embedded in a flexible insulator (Patent Document 2). In this thermoelectric module, an N-type semiconductor element 31 and a P-type semiconductor element 32 are embedded in a flexible insulator 30 such as rubber, plastic or resin, and a hole 33 is formed at a required location. The N-type semiconductor element 31 and the P-type semiconductor are sandwiched between a flexible insulating substrate 36 on which a plastic electrode 34 is formed and a flexible insulating substrate 37 on which a conductive plastic electrode 35 is formed. The element 32 is connected in series.

JP-A-7-202275 JP-A-8-228027

  However, in the prior art described in Patent Document 1, when a cooled object is bonded onto the polyimide layer 21 (20) of this thermoelectric module, voids are likely to occur due to the flexibility of the substrate itself. There is. FIG. 10A is a diagram showing a state in which the object to be cooled is mounted on the substrate, and FIG. 10B is a partially enlarged view thereof. A metallized layer 41 is formed on the polyimide substrate 21, and the heat sink 40 is joined by the solder layer 42. At this time, a void 43 is generated in the solder layer 42 due to the flexibility of the substrate 20, and since the void 43 has a very small thermal conductivity, a high thermal resistance is generated at the interface of the void. For this reason, there exists a problem that module performance falls in the actual use state of a thermoelectric module.

  In the prior art described in Patent Document 2, since there is an insulator between the upper and lower substrates (a low temperature side substrate and a high temperature side substrate as a thermoelectric module), a temperature difference (characteristic important for the thermoelectric module) ΔT) is difficult to obtain.

  The present invention has been made in view of such problems, and even when subjected to thermal stress during actual use, peeling between the thermoelectric element and the electrode is unlikely to occur, and the thermoelectric module having excellent reliability and the thermoelectric module used therefor It is an object of the present invention to provide a substrate member for use and a manufacturing method thereof.

  A thermoelectric substrate member according to the present invention is formed between a pair of substrates, a plurality of electrodes disposed on an opposing surface of the substrate, and the electrodes and the substrate. And a stress buffer layer lower than the Young's modulus of the substrate.

  In the thermoelectric substrate member, the stress buffer layer is, for example, a polyimide resin, an aramid resin, or an epoxy resin. Moreover, the said board | substrate is an alumina or a copper plate, for example.

  The thermoelectric module according to the present invention includes first and second substrates, a plurality of first electrodes and second electrodes disposed on opposing surfaces of the first and second substrates, and the first and second substrates, respectively. An N-type thermoelectric element and a P-type thermoelectric element that are arranged so as to be sandwiched between one electrode and the second electrode, and are connected to one or more of the electrodes, respectively. In the thermoelectric module connected to the N-type thermoelectric element and the P-type thermoelectric element so that the energization direction of the N-type thermoelectric element and the energization direction of the P-type thermoelectric element are opposite to each other, A stress buffer between the first and second electrodes and the first and second substrates, respectively, whose Young's modulus is lower than the Young's modulus of the first and second electrodes and the first and second substrates. It is characterized in that the layers are arranged.

  In this thermoelectric module, the stress buffer layer is, for example, a polyimide resin, an aramid resin, or an epoxy resin. Moreover, the said board | substrate is an alumina or a copper plate, for example.

  The method for manufacturing a thermoelectric substrate member according to the present invention includes a step of applying copper plating or a copper plate to one surface of a stress buffer layer made of a stress buffer material, and a step of attaching a copper plate or an insulating substrate to the other surface, A step of patterning a plurality of electrodes from the copper plating layer or the copper plate by providing a mask on the copper plating layer or the copper plate on one surface and etching the copper plating layer or the copper plate, and a gap between the electrodes A step of cutting the stress buffer layer along a line, dividing the cut, and arranging one or a plurality of electrodes in one stress buffer layer.

  Further, the method of manufacturing a thermoelectric module according to the present invention includes a step of applying copper plating or a copper plate to one surface of a stress buffer layer made of a stress buffer material, and a step of attaching a copper plate or an insulating substrate to the other surface, A step of patterning a plurality of electrodes from the copper plating layer or the copper plate by providing a mask on the copper plating layer or the copper plate on one surface and etching the copper plating layer or the copper plate, and a gap between the electrodes A step of cutting the stress interference substrate along the line and dividing it to arrange one or a plurality of electrodes on one stress buffer layer, and a pair of the obtained thermoelectric substrate members are prepared to face each other A step of joining the electrode and the thermoelectric element with a thermoelectric element interposed between the electrodes.

  According to the present invention, since the stress buffer layer is provided between the electrode and the substrate, even if heat is applied to the substrate from the outside and thermal stress is generated, the thermal stress is buffered by the stress buffer layer. Therefore, it is prevented that a large force acts between the electrode and the thermoelectric element and the both are separated.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a front view showing a part of a thermoelectric module according to an embodiment of the present invention, and FIG. 2 is a plan view showing the same part.

  As shown in FIG. 1, in this embodiment, a pair of substrates 1 and 2 are disposed to face each other, and stress buffer layers 7 and 8 are formed on opposite surfaces of the substrates 1 and 2, respectively. Electrodes 3 and 4 are formed on 7 and 8. In the present embodiment, as shown in FIG. 2, the shape of the stress buffer layers 7 and 8 and the shape of the electrodes 3 and 4 are almost the same, although the stress buffer layers 7 and 8 are slightly larger. One electrode 3 and 4 is disposed on each of the stress buffer layers 7 and 8. The N-type thermoelectric element 5 and the P-type thermoelectric element 6 are sandwiched between the electrodes 3 and 4, and the electrodes 3 and 4 and the thermoelectric elements 5 and 6 are joined by a solder alloy. In this case, an N-type thermoelectric element 5 disposed on the electrode 3 on the substrate 1 side and a P-type thermoelectric element 6 disposed on the electrode 3 adjacent to the electrode 3 are combined into one piece on the substrate 2 side. The electrodes 4 are connected. Similarly, an N-type thermoelectric element 5 and a P-type thermoelectric element 6 connected to one electrode 4 on the substrate 2 side are respectively a P-type thermoelectric element 6 and an N-type thermoelectric element connected to another electrode 4 adjacent thereto. 5 and one substrate 3 on the substrate 1 side. In this way, the N-type thermoelectric element 5 and the P-type thermoelectric element 6 are connected in series by the electrodes 3 and 4, and the electrode 3 at one end and the electrode 4 at the other end of the series connection body are connected. By applying a predetermined voltage therebetween, current flows in the opposite direction between the N-type thermoelectric element 5 and the P-type thermoelectric element 6, and heat is transferred from one substrate 1 or 2 to the other substrate 2 or by the Peltier effect. 1, the target object is cooled on the heat absorption side substrate, and the target object is heated on the heat dissipation side substrate.

  Thus, in the present embodiment, the stress buffer layer 7 is disposed between the electrode 3 and the substrate 1, and the stress buffer layer 8 is disposed between the electrode 4 and the substrate 2. The stress buffer layers 7 and 8 are slightly larger than the electrodes 3 and 4, and one electrode 3 and 4 is disposed on one stress buffer layer 7 and 8.

  In the present invention, the electrodes 3 and 4 can be formed from a copper plating layer or a copper plate. The substrates 1 and 2 are made of alumina or a copper plate, and are basically rigid bodies. Furthermore, a polyimide resin, an aramid resin, or an epoxy resin can be used as the stress buffer layer. This polyimide resin, aramid resin or epoxy resin has a Young's modulus lower than that of the copper plating layer constituting the electrode and the alumina or copper plate constituting the substrate.

  Thereby, even if thermal stress acts on the substrate, the electrode, and the thermoelectric element, the stress buffer layers 7 and 8 prevent the thermoelectric elements 5 and 6 and the electrodes 3 and 4 from being peeled off, thereby improving reliability. A high thermoelectric module can be obtained. In the present invention, since the substrates 1 and 2 themselves basically use a rigid body such as alumina or a copper plate, the thermoelectric module is assembled even though the stress buffer layers 7 and 8 have flexibility. During soldering, voids can be prevented from being generated in the solder layer, and thermal resistance can be prevented from increasing in the solder joint layer.

  The polyimide resin and the aramid resin used as the stress buffer layer in the present embodiment have a relatively low Young's modulus compared to metal and ceramic materials. In addition, these materials can be easily plated with copper and can easily form electrodes. Furthermore, these materials are commercially available and easily available, and also have the advantage of not softening at the soldering temperature. For this reason, these materials are effective as a stress buffer layer.

  Next, the manufacturing method of the thermoelectric module which concerns on embodiment of this invention is demonstrated. 4A, 4B, 5A, 5B, 6, 7A, and 7B show a method of manufacturing a thermoelectric module according to an embodiment of the present invention in the order of steps. FIG. First, as shown in FIG. 4A, a polyimide layer 10 having a copper plating layer 11 formed on one side and a copper plate 12 bonded to the other side is prepared, or on one side as shown in FIG. A polyimide layer 10 is prepared by forming a copper plating layer 11 and bonding an alumina plate 13 to the other surface.

  Next, although an electrode is formed, the manufacturing method in the case of using the double-sided copper plating polyimide layer shown in FIG. However, the same applies to a single-sided copper-plated single-sided alumina plate-bonded polyimide substrate. As shown in FIGS. 5A and 5B, a mask pattern is formed on the copper plating layer 11 on the polyimide layer 10 so as to cover the portion 11a to be the electrodes 3 and 4. And the copper part 11a used as the electrodes 3 and 4 is formed by etching a copper plating layer using this mask pattern as a mask.

  Next, as shown in FIG. 6, in the gap between the copper portions 11a in the polyimide layer 10, a cut 14a extending in the vertical direction is formed by a blade saw.

  Further, as shown in FIG. 7, in the gap between the copper portions 11a in the polyimide layer 10, a cut 14b extending in the lateral direction is formed by a blade saw.

  Thereby, the polyimide layer 10 is separated so as to be one polyimide layer for one electrode, and as shown in FIGS. 1 and 2, on the substrates 1 and 2 (in this case, a copper substrate). The stress buffer layers 7 and 8 made of polyimide are formed, and the substrate with electrodes in which the electrodes 3 and 4 are formed on the stress buffer layers 7 and 8 is manufactured. The stress relaxation effect can be further promoted by dividing the stress buffer layer.

  Next, the substrates 1 and 2 are arranged so that the electrodes 3 and 4 face each other, the thermoelectric elements 5 and 6 are sandwiched between the electrodes 3 and 4, and the electrodes 3 and 4 and the thermoelectric elements 5 and 6 are electrically connected. Bonded with adhesive. Thereby, the thermoelectric module shown in FIGS. 1 and 2 is manufactured.

  Next, a thermoelectric module according to another embodiment of the present invention will be described. FIG. 3 is a plan view showing a part of a thermoelectric module according to another embodiment. In this embodiment, the relationship between the electrodes 3 and 4 on the substrates 1 and 2 and the thermoelectric elements 5 and 6 is the same as that in the first embodiment shown in FIGS. The relationship with the stress buffer layers 7 and 8 is different. That is, in this embodiment, six electrodes 3 are arranged on one stress buffer layer 7, and one stress buffer layer 7 is provided in common for the six electrodes 3. ing. Even if it does in this way, it is effective for the peeling prevention of the thermoelectric element and electrode by a thermal stress, etc., and a manufacturing process is simplified to the extent that the separation process by a dicing saw may be reduced.

  In addition, this invention is not restricted to the said embodiment, For example, you may install several N type thermoelectric elements and several P type thermoelectric elements on one electrode.

The stress buffer layer 7 can be divided by using a separation method using an ultraviolet (UV) laser or a carbon dioxide (CO ₂ ) laser in addition to a dicing saw.

  Next, effects of the embodiment of the present invention will be described in comparison with the characteristics of a comparative example that is out of the scope of the present invention.

(Test Example 1)
The test thermoelectric module has a square surface with a side length of 40 mm and a thickness of 1.5 mm. The number of thermoelectric elements to be mounted is 120 pairs. The material of the thermoelectric element has a composition of Bi _0.5 Sb _1.5 Te _{3 for} the P-type thermoelectric element and Bi _1.9 Sb _0.1 Te _2.6 Se _{0.4 for} the N-type thermoelectric element. These thermoelectric materials are sintered by hot pressing. In the substrate structures of Examples 1 to 4, as shown in FIG. 2, the electrode and the stress buffer layer correspond to 1: 1. The thickness of the polyimide layer as the stress buffer layer is 20 μm, the thickness of the copper plating layer (copper electrode) formed on one surface of the stress buffer layer is 100 μm, and the one attached to the other surface of the stress buffer layer is alumina. In this case, the thickness is 120 μm, and in the case of a copper plate, the thickness is 140 μm. The external dimensions of the thermoelectric module of Comparative Example 1 were the same as those of the example, but the substrate used was a metallized copper electrode (thickness: 100 μm) on one surface of a 0.2 mm thick alumina plate. On the other surface of the alumina plate, a solid copper layer (100 μm) was formed by plating. The thermoelectric module of Comparative Example 1 has a conventional general structure. In Examples 1 to 4 and Comparative Example 1, Sn—Sb solder was used for joining the thermoelectric element and the copper electrode.

  A temperature difference addition test was performed on the specimen for reliability testing. After adding a temperature difference of 150 K to the upper and lower substrates of the thermoelectric module, a thermal cycle test for returning the temperature difference to 0 was repeated. The progress of fracture due to thermal stress was evaluated by the ACR change rate and the maximum temperature difference ΔT change rate of the thermoelectric module. The time required for one thermal cycle was 6 minutes in total: 2 minutes for temperature rise, 1 minute for holding, and 3 minutes for temperature drop. It is.

  As a result, Table 1 below shows the ACR (AC resistance value) increase rate of the thermoelectric module. Table 2 below shows the rate of decrease in ΔT (maximum temperature difference) of the thermoelectric module due to deterioration of thermoelectric characteristics.

  As shown in Table 1 and Table 2, in the case of Examples 1 to 6 of the present invention, even when the thermal cycle is repeated, the ACR increase rate and the decrease rate of the maximum temperature difference are small, and the deterioration of the thermoelectric characteristics is extremely small. . In addition, the thermoelectric module was not broken within the range of the number of cycles tested. On the other hand, in the case of the comparative example 1, the ACR increase rate and the decrease rate of the maximum temperature difference were large, the thermoelectric characteristics were greatly deteriorated due to the thermal cycle, and the thermoelectric module was destroyed in 1500 cycles. Note that the criteria for determining whether or not a module is broken can be considered as a 5% change. That is, if the ACR increase rate or the maximum temperature difference decrease rate exceeds 5%, the Joule heat becomes empirically too high, and the thermoelectric material itself and the interface between the thermoelectric material and the solder layer are cracked. Disappear.

(Test Example 2)
The test thermoelectric module has a square surface with a side length of 40 mm and a thickness of 1.5 mm. The number of thermoelectric elements to be mounted is 120 pairs. The material of the thermoelectric element has a composition of Bi _0.5 Sb _1.5 Te _{3 for} the P-type thermoelectric element and Bi _1.9 Sb _0.1 Te _2.6 Se _{0.4 for} the N-type thermoelectric element. These thermoelectric materials are sintered by hot pressing. In the substrate structures of Examples 5 to 8, as shown in FIG. 3, the ratio of the number of electrodes to the stress buffer layer corresponds to 6: 1. However, the substrate is an alumina plate and the thickness is 0.2 mm.

  The thickness of the polyimide layer as the stress buffer layer of the electrode is 20 μm, the thickness of the copper electrode is 100 μm, and the thickness of the copper metallized layer is 100 μm. As described above, the thermoelectric module of Comparative Example 1 has the same outer dimensions as those of Examples 5 to 8, but the substrate was metallized with a copper electrode on one surface of a 0.2 mm thick alumina plate (thickness: 100 μm). I used something. On the other surface of the alumina plate, a solid copper layer (100 μm) was formed by plating. The thermoelectric module of Comparative Example 1 has a conventional general structure. In Examples 5 to 8 and Comparative Example 1, Sn—Sb solder was used for joining the thermoelectric element and the copper electrode.

  A temperature difference addition test was performed on the specimen for reliability testing. After adding a temperature difference of 150 K to the upper and lower substrates of the thermoelectric module in the same manner as in Test Example 1, a thermal cycle test for returning the temperature difference to 0 was repeated. Then, the progress of fracture due to thermal stress was evaluated by the ACR change rate and the maximum temperature difference ΔT change rate of the thermoelectric module, and the time required for one heat cycle was 2 minutes for temperature rise, 1 minute for holding, 3 minutes for temperature drop as described above. A total of 6 minutes.

  As a result, Table 2 below shows the ACR (AC resistance value) increase rate of the thermoelectric module. Table 2 below shows the rate of decrease in ΔT (maximum temperature difference) of the thermoelectric module due to deterioration of thermoelectric characteristics.

  As shown in Tables 3 and 4 above, in Examples 7 to 12 of the present invention, even when the thermal cycle is repeated, the ACR increase rate and the decrease rate of the maximum temperature difference are small, and the deterioration of the thermoelectric characteristics is extremely small. . In addition, the thermoelectric module was not broken within the range of the number of cycles tested. On the other hand, in the case of the comparative example 1, the ACR increase rate and the decrease rate of the maximum temperature difference were large, the thermoelectric characteristics were greatly deteriorated due to the thermal cycle, and the thermoelectric module was destroyed in 1500 cycles. Thereby, the reliability improvement effect of the thermoelectric module by this invention was confirmed.

It is a front view which shows the thermoelectric module which concerns on 1st Embodiment of this invention. It is a top view of the thermoelectric module of a 1st embodiment similarly. It is a top view which shows the thermoelectric module which concerns on 2nd Embodiment of this invention. (A), (b) is a figure which shows the manufacturing method of the thermoelectric module which concerns on embodiment of this invention. Similarly, it is a figure which shows the next process of FIG. Similarly, it is a figure which shows the next process of FIG. (A), (b) is a figure which similarly shows the next process of FIG. 2 is a front view showing a thermoelectric module described in Patent Document 1. FIG. It is a figure which shows the thermoelectric module of patent document 2. FIG. (A), (b) is a figure explaining the fault of the thermoelectric module of patent document 1. FIG.

Explanation of symbols

1, 2: substrate 3, 4: electrodes 5, 6: thermoelectric elements 7, 8: stress buffer layer 10: polyimide layer 11: copper plating layer 11a: copper portion 12: copper plates 14a, 14b: notches

Claims (8)

A pair of substrates, a plurality of electrodes disposed on opposite surfaces of the substrate, and a stress buffer layer formed between the electrodes and the substrate and having a Young's modulus lower than the Young's modulus of the electrodes and the substrate And a thermoelectric substrate member. The thermoelectric substrate member according to claim 1, wherein the stress buffer layer is a polyimide resin, an aramid resin, or an epoxy resin. The thermoelectric substrate member according to claim 1, wherein the substrate is alumina or a copper plate. A plurality of first and second electrodes disposed on opposing surfaces of the first and second substrates, the first electrode, and the second electrode, respectively. An N-type thermoelectric element and a P-type thermoelectric element that are arranged so as to be sandwiched between the electrodes and are connected to each electrode, respectively, and the first electrode and the second electrode, In the thermoelectric module connected to the N-type thermoelectric element and the P-type thermoelectric element so that the energization direction of the N-type thermoelectric element and the energization direction of the P-type thermoelectric element are opposite to each other, the first and second electrodes A stress buffer layer having a Young's modulus lower than that of each of the first and second electrodes and the first and second substrates is disposed between the first and second substrates. A featured thermoelectric module. The thermoelectric module according to claim 1, wherein the stress buffer layer is a polyimide resin, an aramid resin, or an epoxy resin. The thermoelectric module according to claim 1, wherein the substrate is alumina or a copper plate. Applying copper plating or attaching a copper plate to one surface of the stress buffer layer made of stress buffer material, and attaching a copper plate or insulating substrate to the other surface, and providing a mask on the copper plating layer or copper plate on the one surface Patterning a plurality of electrodes from the copper plating layer or copper plate by etching the copper plating layer or copper plate, and providing a cut in the stress buffer layer along a line passing through the gap between the electrodes. A process for dividing the substrate and disposing one or a plurality of electrodes on one stress buffer layer, and a method for producing a thermoelectric substrate member. Applying copper plating or attaching a copper plate to one surface of the stress buffer layer made of stress buffer material, and attaching a copper plate or insulating substrate to the other surface, and providing a mask on the copper plating layer or copper plate on the one surface Patterning a plurality of electrodes from the copper plating layer or copper plate by etching the copper plating layer or copper plate, and providing a notch in the stress interference substrate along a line passing through a gap between the electrodes. The step of dividing this and arranging one or a plurality of electrodes on one stress buffer layer, and preparing a pair of the obtained thermoelectric substrate members and interposing a thermoelectric element between the opposing electrodes, Joining the thermoelectric element, and a method for manufacturing a thermoelectric module.

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