Manufacturing method for thermoelectric conversion module

Abstract

To provide a manufacturing method for a thermoelectric conversion module that enables high-density mounting by suppressing short circuits between thermoelectric conversion material chips and between adjacent electrodes, as well as connection defects.SOLUTION: A manufacturing method for a thermoelectric conversion module having chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material includes the steps of forming an insulating layer in at least the central region of an electrode provided on one of a pair of substrates and between the electrodes, joining one surface of each of the P-type thermoelectric conversion material chip and the N-type thermoelectric conversion material chip to an electrode via a hot-melt conductive material layer M, and joining the other surface of each of the P-type thermoelectric conversion material chip and the N-type thermoelectric conversion material chip to an electrode provided on the other substrate via a hot-melt conductive material N.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, as one of the means for effectively utilizing energy, there has been a device that directly converts thermal energy into electrical energy and vice versa using a thermoelectric conversion module that has a thermoelectric effect such as the Seebeck effect or the Peltier effect. A known thermoelectric conversion module is a so-called π-type thermoelectric conversion element. A π-type thermoelectric conversion element is configured by providing a pair of electrodes spaced apart on a substrate, with, for example, a P-type thermoelectric element on one electrode and an N-type thermoelectric element on the other electrode, also spaced apart from each other, and connecting the top surfaces of both thermoelectric elements to a common electrode on the opposing substrate. Under these circumstances, there is a demand for improvements in mass productivity and yield in the manufacture of π-type thermoelectric conversion elements. In a thermoelectric conversion module, if a solder material is used as a joining material in the process of joining P-type and N-type thermoelectric elements to the electrodes facing each other on the top and bottom surfaces thereof, solder flow during solder reflow processing may occur when the solder melts, resulting in short circuits between adjacent thermoelectric elements, short circuits between adjacent electrodes, and poor joining between the thermoelectric elements and the electrodes, which may lead to reduced thermoelectric performance and ultimately reduced yield. Patent Document 1 discloses, for example, as shown in Figures 1 to 6 of Patent Document 1, a π-type thermoelectric module in which insulating layers are provided on the top and side surfaces of the second electrode, which is a common electrode, and also on the side surfaces of the solder, n-type thermoelectric element, and p-type thermoelectric element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-123596 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the insulating layer used in Patent Document 1 is provided after the top surfaces of the n-type thermoelectric element and the p-type thermoelectric element are joined to the second electrode serving as a common electrode via solder, and the insulating layer merely serves to prevent short circuits between adjacent second electrodes after the insulating layer is provided. Furthermore, Patent Document 1 is an invention that takes into consideration the possibility of large thermal stress occurring when the temperature difference between one end and the other end of the thermoelectric element increases, which can cause distortion in the thermoelectric element and poor contact between the thermoelectric element and the thermoelectric element wiring pattern. Thus, Patent Document 1 does not take into consideration the effects of solder flow during solder reflow processing between adjacent electrodes when the solder melts.

[0005] In view of the above, the present invention provides a method for manufacturing a thermoelectric conversion module that suppresses short circuits and connection defects between chips of thermoelectric conversion material and between adjacent electrodes, and that allows high-density mounting. The goal is to: [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that, in the manufacture of a thermoelectric conversion module having chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material, an insulating layer is formed in at least the central region of and between the electrodes provided on one of a pair of substrates, and one surface of each of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips is joined to the electrode via a hot-melt type conductive material layer M, and then the electrode provided on the other substrate is joined to the other surface of each of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips via a hot-melt type conductive material N, thereby suppressing short circuits and poor connections between thermoelectric conversion material chips and adjacent electrodes that are caused by the casting of the hot-melt type conductive material when melted, and enabling high-density mounting, and have completed the present invention. That is, the present invention provides the following [1] to [3]. [1] A method for producing a thermoelectric conversion module, comprising the following steps (A) to (E): (A) A step of forming a plurality of electrodes on the opposing surfaces of a pair of substrates, the electrodes connecting chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material, which are spaced apart, alternately in series. (B) forming an insulating layer at least in a central region of the electrode provided on one of the pair of substrates and between the electrodes; (C) a step of placing the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material at a distance from each other on the electrodes provided on one of the substrates, and connecting the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material to the electrodes via a hot melt conductive material layer M by a reflow method. (D) a step of arranging the other substrate of the pair of substrates opposite to one of the substrates so as to sandwich the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material via the electrodes formed on the other substrate. (E) a step of connecting the electrodes formed on the other substrate to the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material via a hot melt conductive material layer N by a reflow method. [2] The method for manufacturing a thermoelectric conversion module according to [1] above, wherein the melting temperature of the thermally fusible conductive material layer M is higher than the melting temperature of the thermally fusible conductive material layer N. [3] The method for manufacturing a thermoelectric conversion module according to [1] or [2] above, wherein the thickness of the insulating layer is 1 μm or more from the surface of the electrode formed on the one substrate opposite to the surface facing the one substrate, and is less than the thickness of the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for manufacturing a thermoelectric conversion module that can suppress short circuits and connection defects between chips of thermoelectric conversion material and between adjacent electrodes, and that allows high-density mounting. [Brief explanation of the drawings]

[0008] [Figure 1]1A to 1C are cross-sectional views illustrating an embodiment of a process for manufacturing a thermoelectric conversion module according to the present invention. [Figure 2] FIG. 2 is a plan view illustrating an example of a pattern of an insulating layer used in the thermoelectric conversion module of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Method of manufacturing thermoelectric conversion modules] The method for producing a thermoelectric conversion module of the present invention is characterized by including the following steps (A) to (E). (A) A step of forming a plurality of electrodes on the opposing surfaces of a pair of substrates, the electrodes connecting chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material, which are spaced apart, alternately in series. (B) forming an insulating layer at least in a central region of the electrode provided on one of the pair of substrates and between the electrodes; (C) a step of placing the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material at a distance from each other on the electrodes provided on one of the substrates, and connecting the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material to the electrodes via a hot melt conductive material layer M by a reflow method. (D) a step of arranging the other substrate of the pair of substrates opposite to one of the substrates so as to sandwich the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material via the electrodes formed on the other substrate. (E) a step of connecting the electrodes formed on the other substrate to the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material via a hot melt conductive material layer N by a reflow method. In the method for manufacturing a thermoelectric conversion module of the present invention, an insulating layer is formed in at least the central region of the electrodes and between the electrodes provided on one of a pair of substrates, and one side of each of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips is bonded to the electrodes via a hot-melt type conductive material layer M by a reflow method. After that, the electrodes provided on the other substrate are bonded to the other side of each of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips via a hot-melt type conductive material layer N by a reflow method. This prevents short circuits and poor connections between thermoelectric conversion material chips and adjacent electrodes caused by the flow of the hot-melt type conductive material during melting, enabling high-density packaging. This can lead to an improvement in yield in the manufacturing process of thermoelectric conversion modules.

[0010] In this specification, "intermediate 1 of the thermoelectric conversion module" means "a component on the upper substrate side of the thermoelectric conversion module immediately before the reflow treatment step in step (C)." Also, "intermediate 2 of the thermoelectric conversion module" means "a component on the upper substrate side of the thermoelectric conversion module immediately after the reflow treatment step in step (C)."

[0011] In this specification, preferred definitions can be selected arbitrarily, and combinations of preferred definitions can be considered more preferred. In this specification, the expression "XX to YY" means "XX or more and YY or less." In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0012] The method for producing a thermoelectric conversion module of the present invention will be described below.

[0013] FIG. 1 is a cross-sectional view illustrating an example of a process according to a method for producing a thermoelectric conversion module of the present invention; 1(a) is a cross-sectional structural view showing an example of an embodiment after electrodes 2b and 2a, which are made up of a plurality of electrodes, are formed and arranged on the opposing surfaces of a pair of substrates, an upper substrate 1b and a lower substrate 1a, in the electrode formation step of step (A), so that chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material (not shown) that are spaced apart are alternately connected in series. 1(b) is a cross-sectional structural view showing an example of an embodiment after forming an insulating layer 4 in at least the central region of electrode 2b provided on upper substrate 1b of a pair of substrates, and between adjacent electrodes (electrode 2b in FIG. 1(a)) in the insulating layer forming step of step (B). An opening 3 made of insulating layer 4 is provided on electrode 2b so that a chip of P-type thermoelectric conversion material and a chip of N-type thermoelectric conversion material spaced apart can be placed thereon. (c) is a cross-sectional view showing an example of the state after a solder material layer 5b as a thermally fusible conductive material layer M is formed at a predetermined position on the electrode 2b in the opening 3 in (b) in the thermally fusible conductive material layer M forming process in step (C). 1(d) is a cross-sectional view showing an example of the state after a chip 6p of a P-type thermoelectric conversion material having a solder-receiving layer 7 and a chip 6n of an N-type thermoelectric conversion material having a solder-receiving layer 7 are placed in predetermined positions relative to the opposing electrodes 2b on the solder material layer 5b in (c) in the step of placing chips of thermoelectric conversion material in step (C). (e) is a cross-sectional view showing an example of the state after the solder material layer 5b in (d) is reflowed at a predetermined temperature and time in the reflow treatment process of step (C) and cooled to a predetermined temperature (the solder material layer 5b solidifies after cooling to become the solder material layer 5b' and becomes thinner). (f) is a cross-sectional structural diagram showing an example of the state after forming a solder material layer 5a as a thermally fusible conductive material layer N at a predetermined position of the electrode 2a on the lower substrate 1a formed in (a) in the thermally fusible conductive material layer N forming process of step (D). 1(g) is a cross-sectional view showing an example of the state after the surface side of the electrode 2a having the solder material layer 5a on the lower substrate 1a side formed in (f) is opposed to the surface side of the chip 6p of P-type thermoelectric conversion material and the chip 6n of N-type thermoelectric conversion material on the upper substrate 1b side formed in (e) in the mounting process of step (D). 1(h) is a cross-sectional view showing an example of the state after the solder material layer 5a in (g) is reflowed at a predetermined temperature for a predetermined time and cooled to a predetermined temperature in the reflow treatment step (E) (the solder material layer 5a solidifies after cooling to become the solder material layer 5a' and becomes thinner, while the solder material layer 5b' maintains its state before and after the reflow treatment). A thermoelectric conversion module is obtained by the reflow treatment.

[0014] <Process (A)> In the method for producing a thermoelectric conversion module of the present invention, step (A) includes an electrode formation step. The electrode formation step is a step of arranging a plurality of electrodes on the opposing surfaces of the pair of substrates to alternately connect chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material that are spaced apart in series. For example, in FIG. 1(a), this is a process of forming electrode 2b on upper substrate 1b and electrode 2a on lower substrate 1a so that chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material that are spaced apart can be alternately connected in series.

[0015] (substrate) The substrate used in the present invention is not particularly limited, and examples thereof include glass, silicon, ceramics, and resin films. From the viewpoint of flexibility, resin films are preferred, and from the viewpoint of heat resistance, heat-resistant resin films are more preferred. The heat-resistant resin film is not particularly limited, but polyimide film, polyamide film, polyetherimide film, polyaramid film, polyamideimide film, or fluorine-based film (polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) is preferred, and polyimide film is particularly preferred because of its high versatility. The thickness of the heat-resistant resin film is preferably 50 to 1000 μm, more preferably 75 to 500 μm, and even more preferably 100 to 200 μm, from the viewpoints of flexibility, heat resistance, and dimensional stability. The glass transition temperature (Tg) of the heat-resistant resin film is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 250°C or higher. Here, Tg refers to the temperature at the maximum point of tan δ (loss modulus / storage modulus) obtained by a dynamic viscoelasticity measuring device (measured in the range of 0 to 500° C. at a temperature rise rate of 5° C. / min).

[0016] (electrode) The electrode used in the present invention is preferably formed of at least one film selected from a vapor-deposited film, a plated film, a film made of a conductive composition, and a metal foil. The metal material used for the electrodes is not particularly limited, but examples thereof include copper, gold, nickel, aluminum, rhodium, platinum, chromium, palladium, stainless steel, molybdenum, tungsten, and alloys containing any of these metals.

[0017] Examples of methods for forming an electrode include a method in which an electrode without a pattern is provided on a substrate, and then processed into a predetermined pattern shape by a known physical or chemical treatment mainly based on photolithography, or a combination of these, specifically a subtractive method, a semi-additive method, a damascene method, or the like. Further, there is also a method of directly forming an electrode pattern by a screen printing method, an ink jet method, or the like using a conductive paste made of a conductive composition containing the above-mentioned metal material or the like. Methods for forming electrodes without patterns include dry processes such as PVD (physical vapor deposition) methods such as vacuum deposition, sputtering, and ion plating, or CVD (chemical vapor deposition) methods such as thermal CVD and atomic layer deposition (ALD), or wet processes such as various coating methods and electrodeposition methods such as dip coating, spin coating, spray coating, gravure coating, die coating, and doctor blade methods, silver halide plating, electroplating, electroless plating, and metal foil lamination, and are selected appropriately depending on the electrode material. The metal foil lamination may be bonded to a chip of thermoelectric conversion material using a solder material as the hot-melt conductive material layer M or N described below. Furthermore, when a ceramic substrate is used, the electrode may be formed using a DBC method, AMB method, or the like. The electrodes used in the present invention are required to have high electrical conductivity, high thermal conductivity, and high dimensional accuracy in order to maintain thermoelectric performance, so it is more preferable to use electrodes formed by plating or vacuum film formation. Vacuum film formation methods such as vacuum deposition and sputtering, as well as electroplating and electroless plating, are preferred because they can easily achieve high electrical conductivity and high thermal conductivity. Depending on the dimensions and dimensional accuracy required for the formed pattern, a pattern can also be easily formed via a hard mask such as a metal mask.

[0018] The thickness of each electrode layer is preferably 1 to 200 μm, more preferably 3 to 100 μm, and even more preferably 5 to 80 μm. When the thickness of the electrode layer is within the above range, the electrical conductivity is high and the resistance is low, resulting in sufficient strength as an electrode.

[0019] <Process (B)> In the method for producing a thermoelectric conversion module of the present invention, step (B) includes a step of forming an insulating layer. The insulating layer forming step is a step of forming an insulating layer at least in the central region of the electrodes provided on one of the pair of substrates and between the electrodes. For example, in Fig. 1(b), this is a step of forming an insulating layer 4 in at least the central region of electrode 2b provided on upper substrate 1b of a pair of substrates, and between adjacent electrodes (electrode 2b in Fig. 1(a)). An opening 3 is provided on electrode 2b so that a chip of P-type thermoelectric conversion material and a chip of N-type thermoelectric conversion material spaced apart can be placed thereon. For example, as shown in FIG. 2(a), the insulating layer 4 has openings 3 so that chips of P-type thermoelectric conversion material and N-type thermoelectric conversion material can be placed on the surface on the electrode 2b side.

[0020] (insulating layer) The insulating layer used in the present invention is preferably formed using an insulating resin. Examples of insulating resins include thermosetting resins such as epoxy resin, urethane resin, bismaleimide triazine resin (BT resin), and phenolic resin, as well as thermoplastic resins such as fluororesin, liquid crystal polymer (LCP), fluoroethylene (PTFE) resin, polyester (PE) resin, and modified polyimide (MPI) resin. For example, the insulating layer, which is a solder resist layer, is preferably formed from a photosensitive resin composition containing a resin selected from epoxy resin, urethane resin, polyimide resin, and polybenzoxazole resin. The insulating layer may contain an inorganic filler such as silica or alumina, or may contain a reinforcing material (core material) such as glass fiber.

[0021] Known methods can be used to form the insulating layer, including, for example, dip coating, spin coating, spray coating, droplet ejection (such as inkjet printing, screen printing, and offset printing), doctor knife, roll coater, curtain coater, knife coater, and lamination. In one embodiment, the insulating layer is preferably subjected to an exposure and development process in order to form openings that expose the electrode surfaces. Examples of the exposure and development process include, when a photosensitive resin is used as the insulating layer, exposing the layer to ultraviolet light or the like through a desired photomask for forming openings, followed by processing using a developer or the like.

[0022] The thickness of the insulating layer is preferably 1 μm or more from the surface of the electrode formed on one substrate opposite the surface facing one of the substrates, and is less than the thickness of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips, more preferably 3 to 200 μm, more preferably 5 to 100 μm, and even more preferably 10 to 30 μm. When the insulating layer is thick in this range, insulation between adjacent P-type thermoelectric conversion material chips and N-type thermoelectric conversion material chips resulting from melt casting, as well as insulation between adjacent electrodes, can be ensured. Furthermore, misalignment of the P-type thermoelectric conversion material chips and the N-type thermoelectric conversion material chips with respect to the electrodes is suppressed.

[0023] <Process (C)> Step (C) is a step of placing a chip of P-type thermoelectric conversion material and a chip of N-type thermoelectric conversion material at a distance from each other on electrodes provided on one of the substrates, and connecting the chip of P-type thermoelectric conversion material and the chip of N-type thermoelectric conversion material to the electrodes via a hot-melt conductive material layer M by a reflow method.

[0024] In the method for producing a thermoelectric conversion module of the present invention, step (C) includes a hot melt type conductive material layer forming step. The step of forming the hot-melt conductive material layer M is a step of forming the hot-melt conductive material layer M at a predetermined position of the electrode provided on one of the substrates. For example, in FIG. 1(c), this is a step of forming a solder material layer 5b as a hot melt conductive material layer M at a predetermined position on the electrode 2b in the opening 3 in (b). Also, for example, as shown in FIG. 2(b), the solder material layer 5b is formed at a predetermined position on the electrode 2b in the opening 3 of the insulating layer 4.

[0025] (Thermal melt conductive material layer M) The hot melt conductive material layer M is used to bond the thermoelectric conversion material chip and the electrode. The melting temperature of the hot-melt conductive material layer M is preferably higher than the melting temperature of the hot-melt conductive material layer N, which will be described later. As a result, when the hot-melt conductive material layer N is reflow-treated, the hot-melt conductive material layer M, which has been reflow-treated prior to this, does not melt and the bond is maintained. For example, a layer containing a solder material, an Ag paste material, a Cu paste material, an Ag sintered material, a Cu sintered material, etc. can be used as the thermally fusible conductive material layer M. Among these, it is preferable to use a solder material layer containing a solder material from the viewpoints of manufacturing efficiency and bonding strength. The solder material may be appropriately selected taking into consideration the melting temperature of the hot-melt conductive material layer N, the heat resistance temperature of the materials other than the hot-melt conductive material layer N that constitute the thermoelectric conversion module, and the electrical conductivity and thermal conductivity of the solder material layer. Examples of known materials include 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. From the viewpoints of lead-free and / or cadmium-free, melting point, electrical conductivity, and thermal conductivity, alloys such as 43Sn / 57Bi alloy, 42Sn / 58Bi alloy, 40Sn / 56Bi / 4Zn alloy, 48Sn / 52In alloy, and 39.8Sn / 52In / 7Bi / 1.2Zn alloy are preferred. Commercially available solder materials include the following: 42Sn / 58Bi alloy (manufactured by Tamura Corporation, product name: SAM10-401-27), 41Sn / 58Bi / Ag alloy (manufactured by Nihon Handa Co., Ltd., product name: PF141-LT7HO), etc. Furthermore, in order to differentiate the reflow temperature from that of the thermally fusible conductive material layer N described below, the melting temperature of the thermally fusible conductive material layer M is preferably 120 to 350°C, more preferably 160 to 300°C, and even more preferably 180 to 250°C.

[0026] Methods for applying the solder material include known methods such as stencil printing, screen printing, dispensing, etc. The heating temperature varies depending on the solder material, resin film, etc. used, but is usually 150 to 370°C for 3 to 20 minutes.

[0027] The thickness of the solder material layer (after heating and cooling) is preferably 2 to 50 μm, more preferably 5 to 40 μm, even more preferably 6 to 35 μm, and particularly preferably 10 to 30 μm. When the thickness of the solder material layer is within this range, adhesion between the thermoelectric conversion material chip and the electrodes is easily achieved. In addition, it is easier to prevent short circuits between the thermoelectric conversion material chips and adjacent electrodes due to solder flow during melting.

[0028] Step (C) preferably further includes a step of mounting a chip of the thermoelectric conversion material. The step of placing a chip of thermoelectric conversion material is a step of placing a chip of thermoelectric conversion material at a predetermined position of the opposing electrodes with a hot melt conductive material layer M interposed therebetween. For example, in FIG. 1(d), this is a step in which a chip 6p of P-type thermoelectric conversion material having a solder-receiving layer 7 on a solder material layer 5b and a chip 6n of N-type thermoelectric conversion material having a solder-receiving layer 7 are placed on opposing electrodes 2b.

[0029] Depending on the application, the arrangement of chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material may be a combination of chips of the same type, or a random combination, such as "NPPN", "PNPP", etc. From the viewpoint of theoretically obtaining high thermoelectric performance, in the present invention, it is preferable to arrange multiple pairs of chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material with electrodes interposed therebetween. The method for placing the thermoelectric conversion material chip on the solder material layer is not particularly limited, and any known method can be used, such as handling one or more thermoelectric conversion material chips using a chip mounter or the like, aligning them with a camera or the like, and then placing them. From the viewpoints of ease of handling, placement accuracy, and mass productivity, it is preferable that the thermoelectric conversion material chips be placed using the above-mentioned chip mounter.

[0030] Step (C) preferably further includes a reflow treatment step. The reflow treatment step is a step of joining a chip of thermoelectric conversion material to a predetermined position of the opposing electrode via a hot melt conductive material layer M. For example, in FIG. 1(e), this is a step in which the solder material layer 5b is reflowed at a predetermined temperature for a predetermined time, cooled to a predetermined temperature, and solidified to form a solder material layer 5b'.

[0031] In the reflow treatment, for example, the thermoelectric conversion module intermediate 1 obtained in FIG. 1(d) is placed in a heating furnace and heated or heated and pressurized. This allows the thermoelectric conversion module intermediate 2 to be obtained. The heating in the reflow depends on the melting temperature of the solder material layer, etc., but is usually performed in an atmosphere of 120 to 350°C for 1 to 60 minutes, preferably in an atmosphere of 160 to 320°C for 5 to 40 minutes. The pressure is preferably 0.05 to 10 MPa, more preferably 0.1 to 5 MPa, and even more preferably 0.2 to 3 MPa.

[0032] <Process (D)> Step (D) is a step of placing one of the pair of substrates opposite the other substrate so as to sandwich a chip of P-type thermoelectric conversion material and a chip of N-type thermoelectric conversion material via electrodes formed on the other substrate.

[0033] In the method for producing a thermoelectric conversion module of the present invention, step (D) preferably includes a hot melt type conductive material layer N forming step. The hot-melt conductive material layer N forming step is a step of forming a hot-melt conductive material layer N at a predetermined position of the electrode provided on the other substrate. For example, in FIG. 1(f), this is a step of forming a solder material layer 5a as a hot melt conductive material layer N at a predetermined position of the electrode 2a on the lower substrate 1a.

[0034] The material used for the other substrate, the thickness of the substrate, etc. are the same as those of the one substrate described above. The material used for the electrode, the thickness of the electrode layer, the method for forming the electrode layer, etc. are the same as those for the electrode used on one of the substrates described above.

[0035] The thermally fusible conductive material layer N can be a layer containing a solder material, an Ag paste material, a Cu paste material, an Ag sintered material, a Cu sintered material, or the like, similar to the thermally fusible conductive material layer M. Among these, it is preferable to use a solder material layer containing a solder material from the viewpoints of manufacturing efficiency and bonding strength. The material used for the solder material layer, the thickness of the solder material layer, the method for forming the solder material layer, etc. are as described above. However, the melting temperature of the hot-melt conductive material layer N is preferably lower than the melting temperature of the hot-melt conductive material layer M. Specifically, the melting temperature of the hot-melt conductive material layer N is preferably 100 to 320°C, more preferably 120 to 250°C, and even more preferably 130 to 200°C. The melting temperature of the heat-melting conductive material layer M is preferably 1 to 200°C higher than that of the heat-melting conductive material layer N, more preferably 10 to 150°C higher, and even more preferably 30 to 100°C higher.

[0036] Preferably, step (D) further includes a mounting step. The mounting process is a process of placing one substrate opposite the other substrate so that the chip of P-type thermoelectric conversion material and the chip of N-type thermoelectric conversion material are sandwiched between the electrodes formed on the other substrate. For example, in FIG. 1(g), this is a process of arranging the surface side of the electrode 2a having the solder material layer 5 on the lower substrate 1a opposite the surface side of the chip 6p of P-type thermoelectric conversion material and the chip 6n of N-type thermoelectric conversion material on the upper substrate 1b, which is the intermediate 2 of the thermoelectric conversion module. As a positioning method, a known method can be used, for example, a method in which alignment marks or the like are provided in advance on the upper substrate 1b side and the lower substrate 1a side, and the alignment is performed by an optical method using a camera or the like, and then the substrates are mounted by a mounting machine or the like. For example, intermediate body 2 of the thermoelectric conversion module on upper substrate 1b may be divided into individual pieces using a dicing device or the like, and mounted on the electrode surface on lower substrate 1a via solder material layer 5a using a flip-chip bonder or the like.

[0037] <Process (E)> In the method for producing a thermoelectric conversion module of the present invention, step (E) preferably includes a reflow treatment step. The reflow treatment step in step (E) is a step of connecting the electrodes formed on the other substrate to the chip of P-type thermoelectric conversion material and the chip of N-type thermoelectric conversion material via the hot melt conductive material layer N by a reflow method. 1(h), for example, the solder material layer 5a is subjected to a reflow treatment, cooled to a predetermined temperature, and solidified. After this process is completed, a thermoelectric conversion module is obtained.

[0038] The reflow treatment is carried out by heating or heating and pressurizing using, for example, a heating furnace, etc. The heating in the reflow treatment depends on the melting temperature of the solder material layer, etc., but is usually carried out for 1 to 60 minutes in an atmosphere of 100 to 320°C, preferably for 5 to 40 minutes in an atmosphere of 120 to 300°C. The pressure is preferably 0.05 to 10 MPa, more preferably 0.1 to 5 MPa, and even more preferably 0.2 to 3 MPa.

[0039] In the reflow treatment for forming the hot-melt type conductive material layers M and N, the reflow treatment temperature for forming the hot-melt type conductive material layer M is preferably higher than the reflow treatment temperature for forming the hot-melt type conductive material layer N. The temperature difference is preferably 1 to 200°C, more preferably 10 to 100°C, and even more preferably 30 to 80°C. By achieving this temperature difference, the chips of P-type thermoelectric conversion material and the chips of N-type thermoelectric conversion material can be positioned with high precision and with high adhesion to the electrodes.

[0040] (Thermoelectric conversion material chip) The chip of the thermoelectric conversion material is not particularly limited and may be made of a thermoelectric semiconductor material or a thin film made of a thermoelectric semiconductor composition.

[0041] (Thermoelectric semiconductor material) The thermoelectric semiconductor material, that is, the thermoelectric semiconductor material constituting the chips of the P-type thermoelectric conversion material and the N-type thermoelectric conversion material is not particularly limited. For example, bismuth-tellurium-based thermoelectric semiconductor materials such as P-type bismuth telluride and N-type bismuth telluride; telluride-based thermoelectric semiconductor materials such as GeTe and PbTe; antimony-tellurium-based thermoelectric semiconductor materials; ZnSb, Zn3Sb 2、 Zn4Sb3 and other zinc-antimony-based thermoelectric semiconductor materials; silicon-germanium-based thermoelectric semiconductor materials such as SiGe; bismuth selenide-based thermoelectric semiconductor materials such as Bi2Se3; β-FeSi2, CrSi2, MnSi 1.73 , Mg2Si and other silicide-based thermoelectric semiconductor materials; oxide-based thermoelectric semiconductor materials; Heusler materials such as FeVAl, FeVAlSi, FeVTiAl, and sulfide-based thermoelectric semiconductor materials such as TiS2 are used. Among these, bismuth-tellurium-based thermoelectric semiconductor materials, telluride-based thermoelectric semiconductor materials, antimony-tellurium-based thermoelectric semiconductor materials, or bismuth selenide-based thermoelectric semiconductor materials are preferred.

[0042] Furthermore, it is more preferable that it is a bismuth-tellurium-based thermoelectric semiconductor material such as P-type bismuth telluride or N-type bismuth telluride. The P-type bismuth telluride has holes as carriers and a positive Seebeck coefficient. For example, Bi X Te3Sb 2-X represented by is preferably used. In this case, X is preferably 0 < X ≦ 0.8, more preferably 0.4 ≦ X ≦ 0.6. When X is greater than 0 and less than or equal to 0.8, the Seebeck coefficient and electrical conductivity increase, and the characteristics as a P-type thermoelectric element are maintained, which is preferable. Also, the N-type bismuth telluride has electrons as carriers and a negative Seebeck coefficient. For example, Bi2Te 3-Y Se YThose represented by are preferably used. In this case, Y is preferably 0 ≦ Y ≦ 3 (when Y = 0: Bi2Te3), more preferably 0 < Y ≦ 2.7. When Y is 0 or more and 3 or less, the Seebeck coefficient and the electrical conductivity increase, and the characteristics as an N-type thermoelectric element are maintained, which is preferable.

[0043] (Solder acceptance layer) In the bonding of the thermoelectric conversion material chip to the electrode, a solder acceptance layer may be provided in advance on the thermoelectric conversion material chip. The solder acceptance layer has a function of improving the bonding property of the solder material layer on the electrode side facing the thermoelectric conversion material chip, and is preferably directly laminated on one surface and the other surface (upper and lower surfaces) of the thermoelectric conversion material chip.

[0044] The solder acceptance layer contains a metal material. The metal material is preferably at least one selected from gold, silver, rhodium, platinum, chromium, palladium, tin, nickel, aluminum, titanium, and alloys containing any of these metal materials. Among these, more preferably, it is a layer containing gold, silver, nickel, aluminum, or either tin and gold, and still more preferably, it is a layer having two layers of nickel and gold. Furthermore, in addition to the metal material, the solder acceptance layer may be formed using a paste material containing a solvent and a resin component. When using a paste material, it is preferable to remove the solvent and the resin component by baking or the like as described later. As the paste material, silver paste and aluminum paste are preferable.

[0045] The thickness of the solder acceptance layer is preferably 10 nm to 50 μm, more preferably 50 nm to 16 μm, and particularly preferably 500 nm to 3 μm. When the thickness of the solder acceptance layer is within this range, the adhesion to the surface of the thermoelectric conversion material chip and the adhesion to the surface of the solder material layer on the electrode side are excellent, and a highly reliable bond can be obtained. Also, not only the conductivity but also the thermal conductivity can be maintained high, so as a result, the thermoelectric performance of the thermoelectric conversion module does not deteriorate and is maintained. The solder-receiving layer may be formed as a single layer using the metal material as is, or may be formed as a multilayer by laminating two or more metal materials. Alternatively, the metal material may be formed as a composition containing a solvent, resin, etc. However, in this case, from the viewpoint of maintaining high electrical conductivity and high thermal conductivity (maintaining thermoelectric performance), it is preferable to remove the resin components, including the solvent, by baking or the like, as the final form of the solder-receiving layer.

[0046] The solder-receiving layer is formed using the above-mentioned metal material. Methods for forming the solder-receiving layer include vacuum deposition methods such as PVD (physical vapor deposition) methods such as vacuum deposition, sputtering, and ion plating, or CVD (chemical vapor deposition) methods such as thermal CVD and atomic layer deposition (ALD), or 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 are selected appropriately depending on the material of the bonding material-receiving layer.

[0047] According to the method for manufacturing a thermoelectric conversion module, it is possible to obtain a thermoelectric conversion module that can be mounted at high density while suppressing short circuits and connection defects between chips of thermoelectric conversion material and between adjacent electrodes. [Example]

[0048] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0049] The thermoelectric conversion modules obtained in the examples and comparative examples were evaluated for electrical resistance and solder leakage between electrode patterns by the following methods.

[0050] (a) Evaluation of electrical resistance The electrical resistance values ​​(Ω) of the thermoelectric conversion modules obtained in the examples and comparative examples were measured by the four-terminal method using a resistance meter (manufactured by Hioki E.E. Corporation, model number: RM3454).

[0051] (b) Evaluation of solder leakage between electrode patterns The thermoelectric conversion modules obtained in the examples and comparative examples were observed using an X-ray inspection device (manufactured by BeamSense, model number: FLEX-M863) to check for solder leakage between the electrode patterns, and the solder leakage between the electrode patterns was evaluated according to the following criteria. ◯: No solder leakage occurred between the electrode patterns, and the electrical resistance value was within the specified range. ×: Solder leakage occurred between the electrode patterns, and the electrical resistance value did not maintain within the predetermined range.

[0052] Example 1 <Fabrication of thermoelectric conversion module> (1) Preparation of the upper substrate structure A printed wiring board was fabricated by etching the copper foil of a copper-clad laminate (Risho Kogyo Co., Ltd., CS-3295, thickness: 60 μm, copper foil thickness: 35 μm) (copper foil electrode size: 0.915 mm × 0.915 mm, thickness: 35 μm) and applying solder resist (Taiyo Ink Mfg. Co., Ltd., product number: PSR2400-G24K) to a thickness of 15 μm above the copper foil. The opening of the solder resist was 0.9 mm × 0.9 mm. Next, solder paste (solder paste material) (manufactured by Kokisha, product number: S3X58-G803, melting temperature: 218°C) was printed (thickness: 10 μm) into the openings of the solder resist on the printed wiring board using a stencil printing device (manufactured by Panasonic, model name: KXF-1G4C). The openings of the stencil mask used for printing the solder paste (solder mask openings) were 0.60 mm × 0.60 mm. Next, a P-type thermoelectric conversion element chip with a gold-plated surface and an N-type thermoelectric conversion material chip (top and bottom surfaces: 0.88 mm × 0.88 mm, thickness: 0.30 mm) were placed on the solder paste using a surface mounter (manufactured by Panasonic, model name: NM-EJM1D) to obtain a thermoelectric conversion module intermediate 1. Next, using a reflow device (manufactured by Tamura Corporation, model name: TNP50-578EM), the solder material was melted by reflow at a peak temperature of 240°C for 10 minutes, and then cooled to room temperature to bond the electrodes on the upper substrate and the thermoelectric conversion material chip, thereby obtaining an upper substrate-side component (thermoelectric conversion module intermediate 2). (2) Separation of the upper substrate components Next, intermediate body 2 of the thermoelectric conversion module was cut into individual pieces using a dicing device (manufactured by Disco Corporation, model number: DFD6362). (3) Preparation of the lower substrate structure Next, solder paste (manufactured by Kokisha, product number: T4AB58-HF360, melting temperature: 140°C) was printed (thickness: 10 μm; no solder resist on the lower substrate side) into the openings of the solder resist of a printed wiring board with the same specifications as (1) using a stencil printing device (manufactured by Panasonic, model name: KXF-1G4C) to obtain a lower substrate side structure. The opening of the stencil mask used for printing the solder paste (solder mask opening) was 0.62 mm × 0.62 mm. (4) Formation of thermoelectric conversion module The individualized upper substrate side was mounted on the lower substrate side using a flip chip bonder (manufactured by Panasonic, model name: FCB3). Next, using a reflow device (manufactured by Tamura Corporation, model number: TNP50-578EM), the solder material was melted by reflow at a peak temperature of 180°C for 10 minutes to bond the lower substrate side and the thermoelectric conversion material chip, thereby obtaining a thermoelectric conversion module (six modules were produced).

[0053] Example 2 A thermoelectric conversion module (one module) was produced in the same manner as in Example 1, except that the opening of the stencil mask when printing the solder paste on the upper substrate side was 0.55 mm x 0.55 mm, and the opening of the stencil mask when printing the solder paste on the lower substrate side was 0.57 mm x 0.57 mm.

[0054] Example 3 Thermoelectric conversion modules (six modules were produced) were produced in the same manner as in Example 1, except that the opening of the stencil mask when printing the solder paste on the upper substrate side was 0.50 mm x 0.50 mm, and the opening of the stencil mask when printing the solder paste on the lower substrate side was 0.50 mm x 0.50 mm.

[0055] Example 4 Thermoelectric conversion modules (six modules were produced) were produced in the same manner as in Example 1, except that the opening of the stencil mask when printing the solder paste on the upper substrate side was 0.45 mm x 0.45 mm and the opening of the stencil mask when printing the solder paste on the lower substrate side was 0.44 mm x 0.44 mm.

[0056] (Comparative Example 1) In Example 1, a thermoelectric conversion module was produced in the same manner as in Example 1, except that a solder resist was also formed on the lower substrate side to a thickness of 15 μm from above the copper foil, and the opening of the stencil mask when printing the solder paste was set to 0.60 mm × 0.60 mm.

[0057] Table 1 shows the evaluation results of the electrical resistance values ​​and solder leakage between patterns of the thermoelectric conversion modules obtained in Examples 1 to 4 and Comparative Example 1.

[0058] [Table 1]

[0059] Table 1 shows that Examples 1 to 4, in which reflow treatment is performed without providing an insulating layer at the center of the electrodes on the lower substrate side or between the electrodes, suppress short circuits and poor connections between chips of thermoelectric conversion material and adjacent electrodes caused by solder casting, compared to Comparative Example 1, in which insulating layers are provided at the center of the electrodes on the upper substrate side and between the electrodes on the lower substrate side and reflow treatment is performed. [Industrial Applicability]

[0060] The method for manufacturing a thermoelectric conversion module of the present invention suppresses short circuits and connection failures between chips of thermoelectric conversion material and between adjacent electrodes, and enables high-density packaging. Therefore, it is conceivable that the method can be used primarily for cooling purposes in the field of electronics devices, such as for temperature control of various sensors, such as CPUs (Central Processing Units) used in smartphones and various computers, image sensors such as CMOS (Complementary Metal Oxide Semiconductor Image Sensors) and CCD (Charge Coupled Devices), and further, MEMS (Micro Electro Mechanical Systems) and other light-receiving elements. [Explanation of symbols]

[0061] 1a: Lower board 1b: Upper board 2a: Electrode 2b: Electrode 3: Opening 4: Insulation layer 5a: Solder material layer N 5a': Solder material layer N (after heating and cooling) 5b: Solder material layer M 5b': Solder material layer M (after heating and cooling) 6p:P-type thermoelectric material chip 6n:N-type thermoelectric conversion material chip 7: Solder acceptance layer

Claims

1. A method for producing a thermoelectric conversion module, comprising the following steps (A) to (E): (A) forming a plurality of electrodes on the opposing surfaces of a pair of substrates, the electrodes connecting chips of P-type thermoelectric conversion material and chips of N-type thermoelectric conversion material, which are spaced apart, alternately in series; (B) forming an insulating layer at least in a central region of the electrode provided on one of the pair of substrates and between the electrodes; (C) a step of placing the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material at a distance from each other on the electrodes provided on one of the substrates, and connecting the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material to the electrodes via a hot melt conductive material layer M by a reflow method; (D) a step of placing the other substrate of the pair of substrates opposite the one substrate side so as to sandwich the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material via the electrodes formed on the other substrate. (E) A step of connecting the electrodes formed on the other substrate to the chips of the P-type thermoelectric conversion material and the chips of the N-type thermoelectric conversion material via a hot melt conductive material layer N by a reflow method.

2. 2. The method for manufacturing a thermoelectric conversion module according to claim 1, wherein the melting temperature of said hot-melt type conductive material layer M is higher than the melting temperature of said hot-melt type conductive material layer N.

3. 3. The method for manufacturing a thermoelectric conversion module according to claim 1, wherein a thickness of the insulating layer is 1 μm or more from a surface of the electrode formed on the one substrate opposite to a surface facing the one substrate, and is less than a thickness of the chip of the P-type thermoelectric conversion material and the chip of the N-type thermoelectric conversion material.

Images