JP2001102643A - Method for manufacturing thermoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric element, provided with elements which have high mechanical strengths and can improve the yield. SOLUTION: A thermoelectric element is constituted of P-type elements 3 composed of a P-type thermoelectric material, N-type elements 4 composed of an N-type thermoelectric material, two substrates 2 having metallic electrodes 5 which can form P-N junction pairs by joining the elements 3 and 4 to each pair by pair, and so on. The gaps between the elements 3 and 4 are filled with an insulating adhesive 6. The elements 3 and 4 are fixed to the electrodes 5, formed on the substrates 2 via jointing layers, in such a way that the P-N junction pairs are formed via the electrodes 5 and connected in series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art A thermoelectric element is manufactured by joining a P-type thermoelectric material and an N-type thermoelectric material via a metal electrode to form a PN junction pair. This thermoelectric element generates electric power based on the Seebeck effect by giving a temperature difference between the junction pair, and as a power generation device, and when current flows through the element, cooling occurs on one side of the junction and heat is generated on the other side It is used as a cooling device using the so-called Peltier effect or as a precision temperature control device.

In general, a thermoelectric element is composed of a plurality of columnar (rectangular) P-type and N-type thermoelectric material pieces (hereinafter referred to as elements) and two substrates provided with metal electrodes for joining them. Have been. With the P-type and N-type elements sandwiched between two substrates, one end surface is fixed to the metal electrode of one substrate, and the other end surface is fixed to the metal electrode of the other substrate, respectively. And a PN junction pair is formed, and each PN junction pair is connected in series.

[0003]

However, such an element is made of, for example, a Bi-Te material as a thermoelectric material, and is brittle and easily cleaved. Therefore, in particular, the thermoelectric element was easily broken by stress in the process of manufacturing the thermoelectric element. Further, since the elements are connected in series, one broken element may cause an open defect (disconnection) or a short circuit. As a result, the yield has been reduced.

The present invention has been made to solve the above problems, and provides a thermoelectric element including an element having high mechanical strength and capable of improving the yield, and a method of manufacturing the same. The purpose is to:

[0005]

In order to solve the above-mentioned problems, the present invention provides a PN element in which a gap between a P-type element made of a P-type thermoelectric material and an N-type element made of an N-type thermoelectric material is filled with an insulating material. A step of forming a resin having holes at positions corresponding to the P-type element and the N-type element on the PN element, a step of forming a bonding layer in the holes, and a step of forming a bonding layer on the substrate. The method includes a step of forming a metal electrode at a portion, and a step of forming a PN junction pair by bonding the metal electrode to the P-type element and the N-type element via a bonding layer.

According to such a method, the PN element is a state in which the P-type and N-type elements are firmly fixed by the insulating adhesive, and the P-type and N-type elements do not fall or interfere. There is also an advantage that the PN element can be processed to an arbitrary size and used. Further, the shapes of the bottom surface and the top surface may be any shapes such as a square such as a square or a rectangle, another polygon, or a circle.

Further, bumps having a projecting shape are formed on the metal electrodes formed on the two substrates. According to this, not only the metal electrodes of the two substrates and the P-type and N-type elements are bonded via the bonding layer, but also the bonding effect due to the engagement of the bumps with the holes formed on the PN elements can be expected. Also, the positioning of the substrate and the PN element becomes easy.

Further, the formed bonding layer is formed by solder. According to this, since the metal electrodes of the two substrates and the P-type and N-type elements are firmly joined by solder, the reliability is improved. Alternatively, the formed bonding layer is formed of a conductive resin. According to this, since the metal electrodes of the two substrates and the P-type and N-type elements are firmly joined with the conductive resin, the reliability is improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG.
1 is a perspective view showing an outline of a thermoelectric element according to the present invention, and FIG. 2 is a cross-sectional view showing a part of the thermoelectric element according to the present invention.

As shown in FIG. 1, a thermoelectric element 1 of this embodiment includes a P-type element 3 made of a P-type thermoelectric material,
It comprises an N-type element 4 made of an N-type thermoelectric material, two substrates 2 having a metal electrode 5 capable of forming a PN junction pair by joining these dissimilar elements in pairs. The P-type element 3 and the N-type element 4 are made of, for example, a sintered body of a Bi-Te-based material.
Alternatively, as P-type and N-type thermoelectric materials, for example, Fe
-Si-based materials, Si-Ge-based materials, Co-Sb-based materials, and the like can also be used. Here, the P-type element 3
Has a main characteristic that, for example, the Seebeck coefficient is 202
μV / K, the specific resistance is 0.93 mΩcm, and the thermal conductivity is 1.46 W / mK. On the other hand, the main characteristics of the N-type element 4 are, for example, a Seebeck coefficient of -188 μV /
K, specific resistivity 0.97 mΩcm, thermal conductivity 1.61
W / mK.

The P-type element 3 and the N-type element 4 are formed as PN elements 7 with a gap filled with an insulating adhesive 6. Each of the elements 3 and 4 is fixed to a metal electrode 5 formed on the substrate via a bonding layer so that a PN junction pair is formed via the metal electrode 5 and these PN junction pairs are connected in series. It has become. The P-type element 3 and the N
As compared with the conventional element having the same characteristics, the mold element 4 has the elements 3 and 4 fixed by the insulating adhesive 6, so that it is electrically insulated and mechanically resistant to shear stress against external impact and the like. The strength is improved, and the yield can be improved. In addition, the substrate smoothes the flow of heat to the outside and prevents the elements 3 and 4 from being damaged by an external impact.

Next, a method for manufacturing the thermoelectric element having the above-described structure will be specifically described, focusing on the portion according to the present invention. First, a P-type thermoelectric material wafer 8 and an N-type thermoelectric material wafer 9 are formed in a structure having fins as shown in FIGS. 3A and 3B, respectively. Next, FIG.
As shown in (d), P-type and N-type thermoelectric material wafers 8 and 9
Is filled with an insulating adhesive 6. Next, as shown in FIG. 4A, the P-type and N-type thermoelectric material wafers 8 and 9 are combined with the insulating adhesive 6 interposed therebetween. Here, when filling the insulating adhesive 6, the P-type and N-type thermoelectric material wafers 8 and 9 may be combined and then filled. Further, the unnecessary portion is cut and polished to obtain a shape as shown in FIG. 4B, the removed portion is filled with the insulating adhesive 6, and the unnecessary portion is cut and polished as shown in FIG. Let it be a PN element 7.

In processing the P-type thermoelectric material wafer 8 and the N-type thermoelectric material wafer 9, for example, a dicing blade or a wire saw used for cutting a silicon semiconductor or the like can be used. The shape (thickness, curve at the tip, etc.) of the blade of this dicing blade is selected in consideration of the shapes of the P-type thermoelectric material wafer 8 and the N-type thermoelectric material wafer 9, thereby forming a desired shape. be able to.

Then, a photosensitive resin 10 in the form of a dry film is stuck on the PN element 7 (not shown). The dry film used here is of a negative type and has a thickness of, for example, 30 μm. After the photosensitive resin 10 is exposed to ultraviolet light through a mask, unexposed portions are dissolved and removed to form a bonding layer 12 as shown in FIG. 6A cross-sectional view and FIG. 6B top view. Hole 11 is formed. The shape of the hole is a square such as a square or rectangle,
Other shapes such as a polygon or a circle may be used. The hole diameter is, for example, 5 μm to 95 μm.
However, only one of the elements 3 and 4 of the PN element 7 appears at the bottom of the hole. Next, as shown in the sectional view of FIG.
2 is added. The thermoelectric element 1 having a PN junction is completed by aligning and joining the elements 3 and 4 of the PN element 7 with the metal electrodes 5 to be joined of the two substrates.

Further, in the above-described manufacturing method, bumps 13 having a projection shape as shown in FIG. 8 are formed on the metal electrodes 5 formed on the two substrates 2. Although not shown, the bumps 13 in the form of protrusions are formed by forming a photosensitive resin on the two substrates 2, forming holes for forming the bumps 13 on the metal electrodes 5 by photolithography, and forming holes by plating. Was formed by forming nickel to a thickness of 10 to 25 μm and then dissolving and peeling off the photosensitive resin. The bump 13 on the metal electrode 5 thus manufactured is
The thermoelectric element 1 having a PN junction is completed by fixing the elements 3 and 4 of the N elements in alignment with each other. In the thermoelectric element 1 thus manufactured, the electrical conductivity and the thermal conductivity between the elements 3 and 4 of the PN element 7 and the two substrates are good, and the elements 3 and 4 of the PN element 12 are firmly joined. This also facilitates alignment during joining.

Further, the conductive material for forming the bonding layer 12 is solder. The solder here is
It is a bismuth-based solder, and is formed by a PN formed with a photosensitive resin having a hole 11 for forming a bonding layer.
After applying the solder to the entire upper and lower surfaces of the element 7, the excess amount is removed. Alternatively, solder may be attached to the tip of a jig having pins of the same pattern as the holes 11 formed on the PN element 7 and transferred to the P-type and N-type elements 3 and 4. The thermoelectric element 1 having a PN junction is completed by aligning with the bumps 13 on the metal electrode 5 to be joined to the respective elements 3 and 4 of the PN element 7 on which the joining layer has been formed, and by thermocompression bonding. The thermoelectric element manufactured in this manner includes a substrate 2 and a PN element 7.
The elements 3 and 4 have good electrical and thermal conductivity and are firmly joined.

The conductive material to be the bonding layer 12 formed was a conductive resin. The conductive resin referred to herein is an epoxy-based two-component adhesive containing a silver-based conductive filler, and is formed by a hole 11 for forming a bonding layer.
On the PN element 7 on which the photosensitive resin is opened,
After applying the conductive resin to the entire lower surface, the excess amount is removed. Alternatively, a conductive resin may be attached to the tip of a jig having pins formed in the same pattern as the holes 11 formed on the PN element 7 and transferred to the P-type and N-type elements 3 and 4. The respective elements 3 and 4 of the PN element 7 on which the bonding layer has been formed are aligned with the bumps 13 on the metal electrodes 5 to be bonded, and are heat-pressed to obtain
The thermoelectric element 1 having an N junction is completed. The thermoelectric element 1 thus manufactured has good electric and thermal conductivity between the substrate 2 and each of the elements 3 and 4 of the PN element 7.
Strongly joined. Further, by improving the mechanical strength of the elements 3 and 4 themselves bonded with the insulating adhesive 6 and the bonding strength between the elements 3 and 4 and the substrate 2, the elements 3 and 4 can be reduced in size. , It is possible to form more PN junction pairs in the same size thermoelectric element 1.

Therefore, it is possible to generate a large electric power even with a small temperature difference, and it is possible to use the thermoelectric element 1 for power generation of various portable electronic devices such as an electronic wristwatch. Further, the thermoelectric element 1 exerts a remarkable effect even when used as a cooling element. That is, the cooling performance is determined by the electric power input to the thermoelectric element 1. In the case of the thermoelectric element 1, it is possible to supply a predetermined electric power with a low current. As a result, it is not necessary to make the input / output wiring thicker or to use a large current type power supply. Therefore, this thermoelectric element 1 is
For example, it can be used for cooling various electronic devices such as a semiconductor laser.

The sizes, materials, and characteristics of the elements 3 and 4 shown in this embodiment are not limited to these. For example, the size can be applied to a general size of a few hundred μm to a millimeter order.

[0020]

According to the present invention, since the P-type and N-type elements are firmly fixed by the insulating adhesive, the mechanical strength against the shear stress against external impact and the like is obtained together with the electric insulation. And the yield can be improved. Further, the substrate smoothes the flow of heat with the outside and prevents each element from being damaged by an external impact. Further, there is an advantage that the PN element can be processed to an arbitrary size and used.

Further, by forming bumps in the form of protrusions on the metal electrodes formed on the two substrates, the electrical and thermal conductivity between each element of the PN element and the two substrates is good, and And the PN element are firmly joined, and the alignment at the time of joining becomes easy.
Furthermore, by forming the formed bonding layer with solder, since the substrate and the PN element are formed by metal bonding with solder, the electric and thermal conductivity between each element of the PN element and the two substrates are also reduced. Often, each element of the substrate and the PN element is firmly joined. In addition, positioning at the time of joining becomes easy.

Further, by forming the formed bonding layer with a conductive resin, the heating step at the time of bonding the PN element to the substrate can be omitted, so that no thermal stress is applied to the PN element. In addition, the electrical conductivity and the thermal conductivity between the substrate, each element of the PN element, and the two substrates are good, and they are firmly joined. In addition, positioning at the time of joining becomes easy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a thermoelectric element according to the present invention.

FIG. 2 is a sectional view showing a part of a thermoelectric element according to the present invention.

FIG. 3 is a perspective view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view and a perspective view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

FIG. 5 is a perspective view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a method for manufacturing a thermoelectric element according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 thermoelectric element 2 substrate 3 P-type element 4 N-type element 5 metal electrode 6 insulating adhesive 7 PN element 8 P-type wafer 9 N-type wafer 10 photosensitive resin 11 hole for forming bonding layer 12 bonding layer 13 bump

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Matsuo Kishi 1-8-8 Nakase, Mihama-ku, Chiba-shi Chiba Prefecture Inside SII IR D Center (72) Inventor Michio Yamamoto Mihama-ku, Chiba Chiba 1-8-8 Nakase SIID Center Co., Ltd. (72) Inventor Hirohiko Nemoto 1-8-8 Nakase Mihama-ku, Chiba City Chiba Pref.

Claims (6)

[Claims] 1. Production of a thermoelectric element in which a P-type element made of a P-type thermoelectric material and an N-type element made of an N-type thermoelectric material are sandwiched between two substrates having metal electrodes to form a PN junction pair. A method comprising: producing a PN element in which a gap between a P-type element and an N-type element is filled with an insulating material; and applying a resin having holes at positions corresponding to the P-type element and the N-type element on the PN element. Forming a bonding layer in the hole, forming a metal electrode on a portion of the substrate corresponding to the bonding layer, and fixing the PN element and the substrate. Bonding the metal electrode to the P-type element and the N-type element via the bonding layer to form a PN junction pair. The method of production. 2. The step of producing the PN element,
Forming a P-type thermoelectric material and an N-type thermoelectric material into a shape having a plate-like fin at a base; and forming the P-type thermoelectric material and the N-type thermoelectric material into a fin portion of the P-type thermoelectric material; Forming a state in which the fin portions of the N-type thermoelectric material are attached to each other with an insulating adhesive therebetween, and removing the bases of the P-type thermoelectric material and the N-type thermoelectric material. The method for manufacturing a thermoelectric element according to claim 1, wherein: 3. The step of forming the resin on the PN element includes: forming a photosensitive resin on a surface of the PN element where an end face of the P-type element and an end face of the N-type element are exposed; The method of manufacturing a thermoelectric device according to claim 1, further comprising: forming holes in the photosensitive resin to expose end faces of the P-type element and end faces of the N-type element. 4. The method for manufacturing a thermoelectric device according to claim 1, wherein the metal electrode includes a bump having a protruding shape. 5. The method for manufacturing a thermoelectric device according to claim 1, wherein said bonding layer is solder. 6. The method for manufacturing a thermoelectric device according to claim 1, wherein the bonding layer is made of a conductive resin.