Method for manufacturing thermoelectric module

Abstract

This method comprises: a step for preparing a first board having a first main surface and a second main surface, with a thermoelectric element bonded to the first main surface; a step for applying a bonding material to a prescribed position on a third main surface of a second board having the third main surface and a fourth main surface; a step for aligning the thermoelectric element and the bonding material by disposing the first board on top of the second board, which has been placed so that the fourth main surface is in contact with a bearing surface of a jig, so that the first main surface faces the second board; and a step for bringing the thermoelectric element and the bonding material into contact with each other to bond the first board and the second board to each other via the thermoelectric element and the bonding material.

Description

Thermoelectric module manufacturing method

[0001] The present invention relates to a method for manufacturing a thermoelectric module.

[0002] Thermoelectric modules using the Seebeck effect are known. Patent Document 1 discloses that an upper plate, on the surface of which a bonding material is applied, is positioned on a lower plate, on which a thermoelectric element is bonded, and the thermoelectric element and the bonding material are brought into contact with each other, thereby integrating the two plates. Patent Document 1 also discloses that the upper plate, on which the bonding material is applied, is turned upside down and placed opposite the lower plate.

[0003] Japanese Patent Application Laid-Open No. 2021-150608

[0004] The process described in Patent Document 1 requires a process in which, after applying a bonding material to the upper plate, the upper plate is sucked, lifted, and inverted. To lift the upper plate by suction, a space for suction is required where the upper plate is not coated with bonding material, which requires space that cannot be used as a thermoelectric module.

[0005] An object of the present invention is to provide a technique that is advantageous for improving the manufacturing efficiency of thermoelectric modules.

[0006] In view of the above problems, a method for manufacturing a thermoelectric module according to an embodiment of the present invention includes the steps of: preparing a first substrate having a first main surface and a second main surface, and a thermoelectric element bonded to the first main surface; applying a bonding material to a predetermined position on a third main surface of a second substrate having a third main surface and a fourth main surface; placing the first substrate on top of the second substrate, which is placed so that the fourth main surface is in contact with a mounting surface of a jig, with the first main surface facing the second substrate, and aligning the thermoelectric element and the bonding material; and abutting the thermoelectric element and the bonding material, thereby bonding the first substrate and the second substrate via the thermoelectric element and the bonding material.

[0007] According to the present invention, it is possible to provide a technique that is advantageous for improving the manufacturing efficiency of thermoelectric modules.

[0008] 1A to 1C are cross-sectional views showing a method for manufacturing a thermoelectric module according to an embodiment of the present invention; 1B are cross-sectional views showing a method for manufacturing a thermoelectric module according to an embodiment of the present invention; 1C are cross-sectional views showing a method for manufacturing a thermoelectric module according to an embodiment of the present invention;

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0010] A method for manufacturing a thermoelectric module according to an embodiment of the present disclosure will be described with reference to Figures 1 to 4. As shown in Figure 4, a thermoelectric module 500 of this embodiment has a plurality of thermoelectric elements 300 arranged between a substrate 110 and a substrate 210.

[0011] The substrates 110 and 210 may be insulating substrates. For example, plastic films may be used for the substrates 110 and 210. Examples of plastic films include polyimide films, polyamide films, polyetherimide films, polyaramid films, polyamideimide films, and glass-epoxy sheets. The substrates 110 and 210 may be made of the same material, or may be made of different materials. The thickness of the substrates 110 and 210 may be 1 μm or more and 1000 μm or less, for example, 10 μm or more and 500 μm or less, or for example, 20 μm or more and 100 μm or less. The material used for the substrates 110 and 210 is not limited to plastic. For example, ceramics such as alumina and aluminum nitride may be used for the substrates 110 and 210. Furthermore, the substrates 110 and 210 may be made of a conductive material covered with an insulating layer, such as an aluminum substrate with an alumina layer formed on its surface.

[0012] In the thermoelectric module 500, the thermoelectric elements 300 may be arranged between the substrate 110 and the substrate 210 such that a p-type thermoelectric element 300p (shown in, for example, FIG. 1C) and an n-type thermoelectric element 300n (shown in, for example, FIG. 1C) are electrically connected in series. The thermoelectric elements 300p and the thermoelectric elements 300n are shown using different hatching, as shown in, for example, FIG. 1C. However, as shown in FIG. 4, they do not necessarily need to be alternately arranged, and may be arranged in an appropriate order depending on the configuration of the electrode patterns 111, 211 arranged on the substrate 110 and the substrate 210. The thermoelectric elements 300 may be made of various thermoelectric materials, such as bismuth-tellurium-based, telluride-based, antimony-tellurium-based, zinc-antimony-based, silicon-germanium-based, bismuth selenide-based, silicide-based, oxide-based, and sulfide-based materials. The thickness of the thermoelectric element 300 in the direction sandwiched between the substrate 110 and the substrate 210 may be, for example, 10 μm or more and 1000 μm or less, further, for example, 20 μm or more and 500 μm or less, or, for example, 50 μm or more and 200 μm or less, or further, for example, 80 μm or more and 120 μm or less.

[0013] Next, a method for manufacturing the thermoelectric module 500 of this embodiment will be described. First, a process for preparing a substrate 110 having a main surface 151 and a main surface 152, with a thermoelectric element 300 bonded to the main surface 151, as shown in FIG. 1e, will be described. First, as shown in FIG. 1a, an electrode pattern 111 is formed on the main surface 151 of the substrate 110. Materials such as gold, copper, molybdenum, nickel, aluminum, rhodium, platinum, chromium, palladium, tungsten, and stainless steel, or alloys thereof, can be used for the electrode pattern 111. Alternatively, the electrode pattern 111 may be formed using a paste material containing a solvent and a resin component in addition to a metal material. When a paste material is used, the solvent and resin component can be removed by firing or the like. Examples of the paste material that can be used include silver paste and aluminum paste.

[0014] Examples of methods for forming the electrode pattern 111 include methods for processing a substrate into a predetermined pattern using known physical or chemical processes, primarily photolithography, or a combination of these processes, or methods for forming an electrode pattern using screen printing, stencil printing, inkjet printing, or the like. Examples of methods for forming an electrode without a pattern include vacuum film formation methods, including PVD (physical vapor deposition) methods such as vacuum deposition, sputtering, and ion plating, CVD (chemical vapor deposition) methods such as thermal CVD and atomic layer deposition (ALD), various coating methods such as dip coating, spin coating, spray coating, gravure coating, die coating, and doctor blade methods, wet processes such as electrodeposition, silver halide plating, electrolytic plating, electroless plating, and metal foil lamination, and the like, which are appropriately selected depending on the metal material. Furthermore, when a ceramic such as alumina or aluminum nitride is used as the substrate 110, the electrode pattern 111 may be formed using a DBC method, an AMB method, or the like.

[0015] The electrode pattern 111 is required to have high conductivity. Because electrodes formed by plating or vacuum deposition can easily achieve high conductivity, the electrode pattern 111 may be formed using vacuum deposition methods such as vacuum evaporation or sputtering, as well as electroplating or electroless plating. Depending on the dimensions and dimensional accuracy requirements of the electrode pattern 111 to be formed, the electrode pattern 111 can also be easily formed through a hard mask such as a metal mask. Furthermore, when forming a film using a vacuum deposition method, the film may be formed while heating the substrate 110 to be used, within a range that does not impair the properties of the substrate 110, for the purpose of improving adhesion to the substrate 110, removing moisture, etc. When forming a film using a plating method, a further film may be formed using electroplating on a film formed by electroless plating.

[0016] The thickness of the electrode pattern 111 may be, for example, 10 nm or more and 200 μm or less, or, for example, 30 nm or more and 150 μm or less, or further, for example, 50 nm or more and 120 μm or less. The thickness of the electrode pattern 111 can be set appropriately depending on the resistance value required of the electrode pattern 111. The above-mentioned materials and configuration can also be used for the electrode pattern 211 provided on the main surface 251 of the substrate 210, which will be described later.

[0017] 1B, for example, cream solder is printed on the electrode pattern 111 as a bonding material 112 for bonding the thermoelectric element 300. The cream solder can be applied to the electrode pattern 111 with high precision and in a short time by, for example, screen printing using a stencil plate. Examples of solder materials include known materials such as Sn, Sn / Pb alloy, Sn / Ag alloy, Sn / Cu alloy, Sn / Ag / Cu alloy, Sn / Sb alloy, Sn / In alloy, Sn / Zn alloy, Sn / In / Bi alloy, Sn / In / Bi / Zn alloy, Sn / Bi / Pb / Cd alloy, Sn / Bi / Pb alloy, Sn / Bi / Cd alloy, Bi / Pb alloy, Sn / Bi / Zn alloy, Sn / Bi alloy, Sn / Bi / Pb alloy, Sn / Pb / Cd alloy, and Sn / Cd alloy. The thickness of the bonding material 112 after the reflow process described below may be, for example, 10 μm or more and 200 μm or less, or, for example, 20 μm or more and 150 μm or less, or, for example, 30 μm or more and 130 μm or more, or even, for example, 40 μm or more and 120 μm or more. A thickness that allows for stable formation of multiple bonds between the electrode pattern 111 and the thermoelectric element 300 can be selected as appropriate. The above-described material and configuration can also be used for the bonding material 212 disposed on the electrode pattern 211 provided on the substrate 210 described below. However, if both the bonding material 112 and the bonding material 212 melt simultaneously in the heat treatment process of the bonding material 212 shown in FIG. 3D described below, misalignment may occur, potentially resulting in unstable mounting position. Therefore, the materials and configurations of the bonding material 112 and the bonding material 212 may be selected so that the melting temperature of the bonding material 112 is higher than the melting temperature of the bonding material 212.

[0018] After cream solder is applied as the bonding material 112 on the electrode pattern 111, the thermoelectric elements 300 (p-type thermoelectric elements 300p and n-type thermoelectric elements 300n) are disposed on the bonding material 112, as shown in FIG. 1C. For example, the thermoelectric elements 300 can be disposed on the bonding material 112 using a support 130. The support 130 can be a surface mounting support such as a flip-chip bonder. After the thermoelectric elements 300 are disposed at predetermined positions on the electrode pattern 111 via the bonding material 112, a heat treatment is performed using a reflow furnace or the like, whereby the thermoelectric elements 300 are bonded to the electrode pattern 111 disposed on the substrate 110 via the bonding material 112, as shown in FIG. 1D. The reflow process allows multiple thermoelectric elements 300 to be disposed on the electrode pattern 111 of the substrate 110 with high density and precision. That is, smaller thermoelectric elements 300 can be arranged at closer intervals on the electrode pattern 111. For example, when the surface of the thermoelectric element 300 in contact with the electrode pattern 111 is rectangular, the length of one side of the electrode pattern 111 may be, for example, 0.01 mm to 10 mm, or for example, 0.1 mm to 2 mm, or for example, 0.2 mm to 0.8 mm. Furthermore, the interval at which the thermoelectric elements 300 are arranged may be, for example, 0.01 mm to 5 mm, or for example, 0.04 mm to 1 mm, or for example, 0.08 mm to 0.20 mm.

[0019] Although not shown in FIG. 1c and other drawings, a solder-receiving layer may be disposed between the bonding material 112 and the thermoelectric element 300. A solder-receiving layer may also be disposed between the bonding material 212 (described later) and the thermoelectric element 300. The solder-receiving layer has the function of improving the bonding between the thermoelectric element 300 and the bonding material 112 (bonding material 212) and is directly bonded to the thermoelectric element 300. The solder-receiving layer may contain a metal material. The metal material may be at least one selected from gold, silver, nickel, aluminum, rhodium, platinum, chromium, palladium, tin, and alloys containing any of these metal materials. Among these, gold, silver, nickel, aluminum, or a two-layer structure of tin and gold may be used. From the viewpoints of material cost, high thermal conductivity, and bonding stability, silver, nickel, and aluminum are more suitable as the solder-receiving layer.

[0020] The thickness of the solder-receiving layer may be, for example, 10 nm or more and 50 μm or less, or, for example, 50 nm or more and 16 μm or less, further, for example, 200 nm or more and 4 μm or less, or even 500 nm or more and 3 μm or less. When the thickness of the solder-receiving layer is within this range, adhesion to the surface of the thermoelectric element 300 and adhesion to the bonding material 112 (bonding material 212) are excellent, resulting in a highly reliable bond. Furthermore, high electrical conductivity as well as thermal conductivity can be maintained, resulting in the thermoelectric performance of the thermoelectric module 500 being maintained without any degradation. The solder-receiving layer may be formed as a single layer using a metal material, or may be formed as a multilayer by laminating two or more metal materials.

[0021] The solder-receiving layer can be formed using the metal material described above. The solder-receiving layer is required to have high electrical conductivity and high thermal conductivity in order to maintain thermoelectric performance. Therefore, the solder-receiving layer can be formed using the electrolytic plating method, electroless plating method, or vacuum deposition method described above.

[0022] The above steps may prepare a substrate 110 having thermoelectric elements 300 bonded to its main surface 151. Furthermore, for example, after bonding the thermoelectric elements 300 to the substrate 110, the substrate 110 to which the thermoelectric elements 300 are bonded may be singulated into units having a predetermined configuration (e.g., a predetermined number of thermoelectric elements 300), as shown in FIG. 1 e. Singulation is performed using an appropriate means such as dicing. In the configuration shown in FIG. 1 e, a dicing blade 140 for dicing is illustrated as an example. Hereinafter, even in the case of singulation, a unit including the singulated substrate 110 may be simply referred to as the "substrate 110" or the "substrate 110 to which the thermoelectric elements 300 are bonded to its main surface 151."

[0023] 3A in FIG. 3 shows the substrate 210 of the substrates 110 and 210 that constitute the thermoelectric module 500. The substrate 210 has a main surface 251 and a main surface 252. An electrode pattern 211 is formed on the main surface 251 of the substrate 210. The electrode pattern 211 may be made of the same material as the electrode pattern 111 provided on the main surface 151 of the substrate 110, or may be made of a different material. Furthermore, the thickness of the electrode pattern 211 may be the same as that of the electrode pattern 111, or may be different from that of the electrode pattern 111.

[0024] Next, as shown in 3b of FIG. 3, a bonding material 212 is disposed at a predetermined position on the main surface 251 of the substrate 210. The predetermined position may be on the electrode pattern 211 disposed on the main surface 251 of the substrate 210. Similar to the bonding material 112, cream solder may be used as the bonding material 212. The cream solder can be applied to the electrode pattern 211 with high precision and in a short time by screen printing using a stencil plate, for example. The process of preparing the substrate 210 having the electrode pattern 211 shown in 3a of FIG. 3 and the process shown in 3b of FIG. 3 may be performed in parallel with the process of preparing the substrate 110 having the thermoelectric element 300 bonded to its main surface 151 shown in 1a to 1e of FIG. 1. Furthermore, for example, the processes shown in 3a and 3b of FIG. 3 may be performed after the substrate 110 having the thermoelectric element 300 bonded to its main surface 151 is prepared.

[0025] 3 c, the substrate 110 is placed on the substrate 210, which is placed on the mounting surface 221 of the jig 220 so that the main surface 252 is in contact with the mounting surface 221, with the main surface 151 facing the substrate 210, and the thermoelectric element 300 is aligned with the bonding material 212. The process of placing the substrate 110, with the thermoelectric element 300 bonded to the main surface 151, on the substrate 210 will be described in detail below.

[0026] To place the substrate 110 with the thermoelectric element 300 bonded thereto on the substrate 210, first, as shown on the left side of FIG. 2 , the substrate 110 is lifted from the main surface 151 side using a support 131. The support 131 may be, for example, a surface mounting support such as a flip-chip bonder. The support 131 adheres to the substrate 110 with the thermoelectric element 300 bonded thereto by suctioning an area of ​​the substrate 110 including the portion where the thermoelectric element 300 is bonded. Next, the support 131 is moved upward to lift the substrate 110. The surface of the thermoelectric element 300 that is bonded to the bonding material 212 is not coated with cream solder or the like. Furthermore, the surface of the thermoelectric element 300 that is bonded to the bonding material 212 is protected by a metal layer (e.g., the above-mentioned solder-receiving layer) that is provided when bonding to the bonding material 212, so that contact with the support 131 has little effect on subsequent processes. Therefore, by sucking the substrate 110 from the side of the main surface 151 using the support 131 and adhering it to the support 131, the substrate 110 with the thermoelectric elements 300 bonded to the main surface 151 can be lifted up.

[0027] After lifting the substrate 110 using the support 131, as shown on the right side of FIG. 2 , the lifted substrate 110 is supported from the side of the main surface 152 using the support 132. The support 132 may be, for example, a surface mounting support such as a flip-chip bonder, similar to the support 131. At this time, the substrate 110 supported by the support 131 may be inverted, and then the substrate 110 may be supported by the support 132. Alternatively, for example, the substrate 110 may be inverted while being supported by the support 131 and the support 132. Alternatively, for example, the substrate 110 may be inverted while being supported by the support 132, after the support 131 is removed. The support 132 may support the substrate 110, for example, by adsorbing to the main surface 152 of the substrate 110.

[0028] The substrate lifted by the support 131 is supported from the main surface 152 side using the support 132. Next, after the support 131 is removed from the substrate 110 while the substrate 110 is supported by the support 132, the thermoelectric element 300 and the bonding material 212 disposed on the main surface 251 of the substrate 210 are aligned as shown in FIG. 3C. Consider a case where the substrate 210 with the bonding material 212 disposed on its main surface 251 is inverted and aligned over the substrate 110 to which the thermoelectric element 300 is bonded. In such a case, in order to invert the substrate 210, it is not possible to lift the portion of the main surface 251 of the substrate 210 to which cream solder or the like is applied as the bonding material 212 by suction. This is because the cream solder would be sucked in. Furthermore, if a space for suction is provided on the substrate 210, the utilization efficiency of the substrate 210 would be reduced. On the other hand, in this embodiment, as described above, the substrate 110 to which the thermoelectric element 300 is bonded can be lifted from the side of the main surface 151 on which the thermoelectric element 300 is disposed. This reduces the space that cannot be used for the thermoelectric module 500 in the substrate 110 and the substrate 210. In other words, the manufacturing efficiency of the thermoelectric module 500 can be improved.

[0029] 2 shows a configuration in which the substrate 110 is directly transferred between the support 131 and the support 132. However, the process of arranging the substrate 110 having the thermoelectric element 300 bonded thereto on the substrate 210 is not limited to this. For example, the singulated substrates 110 are stored in a tray or tape reel with the main surface 152 of the substrate 110 facing up using a taping device or sorter, and are then supplied to a device equipped with the support 132, such as a surface mounter. The support 132 may then lift the substrate 110 stored in the tray or tape reel from the side of the main surface 152.

[0030] After aligning the thermoelectric element 300 bonded to the substrate 110 with the bonding material 212 arranged on the substrate 210, the thermoelectric element 300 and the bonding material 212 are brought into contact with each other. Next, by performing a heat treatment using a reflow furnace or the like, the substrate 110 and the substrate 210 are bonded via the thermoelectric element 300 and the bonding materials 112 and 212, as shown in 3d of FIG.

[0031] As shown in FIG. 3d, a plurality of substrates 110 having thermoelectric elements 300 bonded to their main surfaces 151 may be prepared, and the plurality of substrates 110 may be aligned and bonded to predetermined positions on the substrate 210. In this case, after the step of bonding the substrates 110 and 210 via the thermoelectric elements 300, a step of singulating the bonded plurality of substrates 110 and 210 into individual substrates 110 may be further included. This results in the formation of a thermoelectric module 500 as shown in FIG. 4. The singulation may be performed by dicing or the like, similar to the step shown in FIG. 1e. Furthermore, prior to the singulation, a protective member for protecting the thermoelectric elements 300 during the singulation step may be injected between the substrates 110 and 210 from between each of the plurality of substrates 110, so that the spaces between the substrates 110 and 210 are at least partially filled with the protective member. Also, for example, one substrate 110 may be joined to one substrate 210 via a thermoelectric element 300, and function as one thermoelectric module 500, or multiple substrates 110 may be joined to one substrate 210 via a thermoelectric element 300, and function as one thermoelectric module 500.

[0032] As described above, when the substrate 110 and the substrate 210 are joined via the thermoelectric element 300, the substrate 110 joined to the thermoelectric element 300 is inverted and moved onto the substrate 210. This allows the thermoelectric module 500 to be manufactured more efficiently than when the substrate 210 is inverted and moved onto the substrate 110 joined to the thermoelectric element 300.

[0033] Furthermore, the above-described processes are shown assuming surface mounting. Therefore, it is possible to arrange the thermoelectric elements 300 on the substrate 110 with high density and precision, thereby increasing the area ratio of the thermoelectric elements 300 in the resulting thermoelectric module 500. When the performance of the thermoelectric elements 300 is constant, the performance of the thermoelectric module 500 can be proportional to the area of ​​the thermoelectric module 500 in which the thermoelectric elements 300 are arranged. Therefore, by using the manufacturing process of this embodiment, it is possible to efficiently provide a high-performance thermoelectric module 500.

[0034] In the above description, an example has been given in which solder (cream solder) is used as the bonding materials 112, 212. However, the material of the bonding materials 112, 212 is not limited to solder. Other materials may be used for the bonding materials 112, 212 as long as they are capable of electrically and mechanically bonding the electrode patterns 111, 211 and the thermoelectric element 300. For example, a conductive adhesive such as silver paste or an anisotropic conductive film (ACF) may be used as the bonding materials 112, 212.

[0035] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

[0036] 110, 210: substrate, 112, 212: bonding material, 151, 152, 251, 252: main surface, 220: jig, 221: mounting surface, 300: thermoelectric element, 500: thermoelectric module

Claims

1. A step of preparing a first substrate having a first main surface and a second main surface, with a thermoelectric element joined to the first main surface; a step of applying a bonding material to a predetermined position on the third main surface of a second substrate having a third main surface and a fourth main surface; a step of arranging the first substrate on the second substrate placed so that the fourth main surface contacts the mounting surface of a jig, with the first main surface facing the second substrate, and aligning the thermoelectric element and the bonding material; and a step of bringing the thermoelectric element into contact with the bonding material and joining the first substrate and the second substrate through the thermoelectric element and the bonding material. A method for manufacturing a thermoelectric module, characterized by including these steps.

2. The step of alignment includes: a step of lifting the first substrate from the side of the first main surface using a first support tool; a step of supporting the lifted first substrate from the side of the second main surface using a second support tool, removing the first support tool from the first substrate, and then aligning the thermoelectric element and the bonding material. The method for manufacturing a thermoelectric module according to claim 1, characterized by including these steps.

3. The first support tool lifts the first substrate by sucking a region including a portion of the first substrate to which the thermoelectric element is joined. The method for manufacturing a thermoelectric module according to claim 2, characterized by this.

4. In the step of preparation, a plurality of the first substrates are prepared. In the step of joining, the plurality of the first substrates are joined to respective predetermined positions of the second substrate. After the step of joining, the method further includes a step of separating the joined plurality of the first substrates and the second substrate into individual pieces for each first substrate. The method for manufacturing a thermoelectric module according to any one of claims 1 to 3, characterized by including this step.

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