JPH11251650A - Thermoelectric element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a thermoelectric element in manufacturing yield, by a method wherein elements provided for the thermoelectric element are improved in manufacturing method. SOLUTION: A thermoelectric element 1 is equipped with boards 2B and 2A which are each provided with an element 3 of P-type thermoelectric semiconductor material, an element 4 of N-type thermoelectric semiconductor material, and a metal electrode 5 which joins a pair of the element 3 and 4 together to form a PN junction couple. In this case, the elements 3 and 4 on the metal electrode 5 are formed through an up-cut dicing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises P-type and N-type elements made of P-type and N-type thermoelectric semiconductor materials, and performs temperature difference power generation (thermal power generation) by the Seebeck effect and electronic cooling and heat generation by the Peltier effect. The present invention relates to a thermoelectric element that can be used and a manufacturing method thereof.

[0002]

2. Description of the Related Art A thermoelectric element is manufactured by joining a P-type thermoelectric semiconductor material and an N-type thermoelectric semiconductor 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 pair of junctions, so as a power generation device.
On the other hand, there is a use as a cooling device or a precision temperature control device utilizing the so-called Peltier effect that generates heat. The thermoelectric element is generally manufactured and used as a thermo module in which a plurality of tens to hundreds of PN junction pairs are formed in series in order to enhance the performance as an element. The thermoelectric element as the thermo module maintains a shape as a structural body, and has two substrates having metal electrodes for forming a PN junction pair, and a plurality of P-type and N-type interposed therebetween. It is composed of a thermoelectric semiconductor material and a bonding material for bonding the P-type and N-type elements to the metal electrodes. In this thermoelectric element, for example, P-type and N-type thermoelectric semiconductor material pieces (hereinafter, referred to as elements) cut in advance into a predetermined shape and size are respectively arranged at predetermined positions with a jig or the like. It can be manufactured by joining the arranged elements to a metal electrode with a joining material such as solder and sandwiching the two elements with two substrates. Here, solder or the like used as a bonding material is formed in advance on a metal electrode on the substrate by a method such as printing or plating. Further, other than such a manufacturing method, for example,
2, a step of forming solder bumps on each end face of a wafer-shaped (plate-shaped or rod-shaped) P-type and N-type thermoelectric semiconductor material, an electrode wiring (metal electrode) and a structure ( Forming a structure), bonding a thermoelectric semiconductor material on which solder bumps are formed to a substrate, and cutting unnecessary portions of the thermoelectric semiconductor material bonded to the substrate to form thermoelectric semiconductor material chips (elements). There is also a method of manufacturing through a process and a process of joining substrates on which P-type and N-type thermoelectric semiconductor material chips are respectively formed. In this method, the metal electrode and the thermoelectric semiconductor material chip are joined with a structure interposed therebetween in order to improve the joining strength.

[0003]

However, in the above-described manufacturing method, when the thermoelectric semiconductor material is bonded to the substrate and then cut by, for example, down-cutting when dicing, the lower portion of the thermoelectric material at the cutting margin is removed. In some cases, the elements are connected to each other, resulting in a short circuit. In addition, since the thermoelectric material cannot be removed, the element is broken due to poor cutting properties, and it has been difficult to manufacture a thin element. On the other hand, to prevent short-circuit failure between elements due to thermoelectric material,
When the blade is lowered and cut, the metal electrode on the substrate is cut, which may cause an electrical disconnection failure. For this reason, the yield of thermoelectric element fabrication has been reduced due to various problems caused by dicing of the thermoelectric material.

The present invention has been made to solve the above problems, and has as its object to provide a thermoelectric element having a thin element and capable of improving the yield, and a method of manufacturing the same. .

[0005]

In order to solve the above problems, the invention according to claim 1 comprises a P-type element made of a P-type thermoelectric semiconductor material, an N-type element made of an N-type thermoelectric semiconductor material, It is provided with two substrates having metal electrodes capable of forming a PN junction pair by joining a pair of different types of elements of N-type and N-type, and a bonding material for bonding the P-type and N-type elements to the metal electrodes. In thermoelectric elements,
At one end on the metal electrode, the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are bonded to separate substrates,
The P-type and N-type thermoelectric semiconductor materials are cut by dicing upcut to form a plurality of the P-type and N-type elements on the substrate, and then the two substrates are faced to each other. In addition, the tip of the N-type element is fixed to the metal electrode of the opposing substrate, and these substrates are joined.

According to the present invention, the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are bonded to separate substrates, and the P-type and N-type thermoelectric semiconductor materials are cut by dicing upcut. The uncut portions of the P-type and N-type thermoelectric semiconductor materials are eliminated, and the uncut portions prevent the elements from being electrically connected to each other, so that occurrence of short-circuit failure can be reduced. In addition, since there is no remaining cutting, the cutting performance of dicing is improved, so that a thin element can be supplied.

Specifically, examples of the P-type and N-type thermoelectric semiconductor materials include Bi-Te-based materials, Fe-Si-based materials, Si-Ge-based materials, and Co-Sb-based materials. Further, the structure can be formed of a thick-film photoresist by, for example, a photolithography method.

According to the present invention, a P-type element made of a P-type thermoelectric semiconductor material and an N-type element made of an N-type thermoelectric semiconductor material are provided.
For joining the P-type and N-type elements to the metal electrodes, two substrates having a mold element, a metal electrode capable of forming a PN junction pair by joining these P-type and N-type heterogeneous elements one by one. A method for manufacturing a thermoelectric element comprising the bonding material of (a), wherein the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are bonded to separate substrates, and the P-type and N-type thermoelectric semiconductor materials are improved in dicing. After cutting by cutting, the plurality of P-type and N-type elements are formed on the substrate, and then the two substrates are faced to each other.
It is characterized in that the tips of the mold and N-type elements are fixed to the metal electrodes of the opposing substrates, and these substrates are joined.

According to the manufacturing method of the present invention, the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are joined to the separate substrates, and the P-type and N-type thermoelectric semiconductor materials are cut by dicing upcut. Therefore, since the P-type and N-type thermoelectric semiconductor materials are not cut off and the elements are not electrically connected to each other, it is possible to reduce occurrence of short-circuit failure. In addition, since it is not necessary to reduce the blade height and to cut, the metal electrode on the substrate is not cut to cause an electrical disconnection defect, and the yield can be improved.

[0010]

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 state where an element is joined to one substrate.

As shown in FIG. 1, a thermoelectric element 1 of this embodiment includes a P-type element 3 made of a P-type thermoelectric semiconductor material 3A (FIGS. 7 to 12) and an N-type thermoelectric semiconductor material 4A.
Substrates 2A, 2B having an N-type element 4 composed of (FIGS. 7 to 12) and metal electrodes 5 capable of forming a PN junction pair by joining a pair of these P-type and N-type different elements 3, 4 one by one. And so on.

P-type element 3 and N-type element 4
Is made of, for example, a sintered body of a Bi-Te-based material. As shown in FIG. 2, each element 3 (4) has a bottom surface 3b (4b) and an upper surface 3a (4a) parallel to the bottom surface 3b (4b). The area of the cross section parallel to 3a (4a) is
It is formed in a shape that continuously decreases from (4b) toward the upper surface 3a (4a). This element 3 (4)
The bottom surface 3b (4b) is the metal electrode 5 of the substrate 2B (2A).
Are joined via a structure 7. The hollow portion 7a of the structure 7 is filled with a bonding material 6 composed of Ni 6a and solder 6b so that the element 3 (4) and the metal electrode 5 are electrically connected. It has become. On the other hand, the upper surface 3a (4) of the element 3 (4)
a) is directly formed by the bonding material 6 as shown in FIG.
It is fixed to the metal electrode 5 of the substrate 2A (2B).

As described above, the P-type element 3 and the N-type element 4 are sandwiched between the two substrates 2A and 2B, and one end is connected to the metal electrode 5 of the substrate 2A and the other end is connected to the metal electrode 5 of the substrate 2B. In the joined state, the metal electrode 5
And a PN junction pair is formed through
The joining pairs are connected in series.

As shown in FIG. 2, on the substrates 2A and 2B, an oval-shaped metal electrode 5 capable of joining a pair of different types of P-type and N-type elements 3 and 4 is provided. A structural body 7 formed in a substantially cylindrical shape from, for example, a resin material and having a hollow portion 7a on the inner peripheral side is provided at one upper end side. These structures 7 are interposed between the bottom surfaces 3b and 4b of the elements 3 and 4 and the metal electrode 5 to control the flow of the bonding material 6 generated at the time of bonding to increase the bonding strength between them. Here, the edge of the bonding surface with the bottom surface 3b of the P-type element 3 on the metal electrode 5 of the substrate 2B and the bonding surface with the bottom surface 4b of the N-type element 4 on the metal electrode 5 of the substrate 2A. At the edge. The size of these structures 7 is determined by the bottom surfaces 3b, 4
It is set based on the size of b (the joint surface to the structure 7). Here, for example, the bottom surfaces 3b of the elements 3, 4;
When the shape of 4b is a square, the size of the structure 7 is
At least the size of the hollow portion 7a covered by the bottom surfaces 3b and 4b, that is, the inner diameter thereof is set to a value smaller than the length of one side of the bottom surfaces 3b and 4b.

Furthermore, since the arrangement position of each element 3, 4 is clearly indicated by the structure 7, it is possible to improve the accuracy of the alignment when the metal electrode 5 and the elements 3, 4 are joined. Become.

Next, an example of a method for manufacturing the thermoelectric element 1 thus configured will be described step by step with reference to FIGS.

FIGS. 3 to 14 are cross-sectional views showing respective manufacturing steps of the thermoelectric element 1. FIG. 3 shows an insulating film forming step, FIG. 4 shows a film forming step, FIG. 5 shows an electrode forming step, and FIG. Manufacturing process, FIG. 7
Is a mask forming step, FIG. 8 is a Ni and solder plating step,
9 shows a mask removing step, FIG. 10 shows a bump forming step, and FIG.
1 is a bonding step, FIG. 12 is a cutting / removing step (pillaring step), FIG. 13 is a cutting / removing step (pillaring step), FIG.
Indicates an assembly process.

First, in the insulating film forming step, as shown in FIG. 3, an insulating thermal oxide film 8 (for example, silicon oxide) is formed on a surface of substrates 2A and 2B (for example, a single crystal silicon wafer) to a predetermined thickness. (For example, 1 μm).

In the film forming step, as shown in FIG.
A, 2B on one end surface (the surface of the thermal oxide film 8 formed in the insulating film forming step) by, for example, a sputtering method.
A metal film (for example, a three-layer film 5 made of chromium, nickel, and gold is 0.1 μm, 3 μm, and 1 μm, respectively) is formed.

In the electrode forming step, as shown in FIG. 5, an electrode wiring pattern (metal electrode 5 and input / output electrodes) is formed from the metal film formed in the film forming step (FIG. 4) by photolithography. .

In the structure manufacturing process, as shown in FIG.
On the metal electrode 5 formed in the electrode forming step (FIG. 5), a plurality of structures 7 (for example,
A cylindrical pattern having an inner diameter of 100 μm, an outer diameter of 150 μm, and a height of 50 μm) is formed. Here, the structure pattern is designed so that the structure 7 is formed at the position where the P-type and N-type elements 3 and 4 are arranged.

In the mask forming step, as shown in FIG.
For example, a film photoresist 9 is applied by a coater to both surfaces of a wafer of a P-type thermoelectric semiconductor material 3A and an N-type thermoelectric semiconductor material 4A made of a Bi—Te-based sintered body. Next, the bonding step (FIG. 11) performed later,
It is manufactured by a photolithography method so that an opening for forming the solder bump 6A is formed in the photoresist in a pattern having a P-type and N-type arrangement in consideration of the removal process (FIGS. 12 and 13).

In the Ni and solder plating step, as shown in FIG. 8, the opening of the photoresist is washed with an acid (eg, 10% sulfuric acid) or the like, and the opening is plated with nickel 10 (eg, 15 μm thick). Then, solder plating 11 (for example, the composition ratio of Sn and Pb is 6: 4 and the thickness is 50 μm) is formed. The nickel plating in this step enhances the adhesion between the solder and the thermoelectric semiconductor materials 3A and 4A, and at the same time, the bonding step (FIG.
In 1) and in the cutting / removing step (FIGS. 12 and 13), it has a role of forming a predetermined gap between the substrates 2A and 2B and the thermoelectric semiconductor materials 3A and 4A.

In the mask removing step, as shown in FIG.
The photoresist is stripped from the thermoelectric semiconductor materials 3A, 4A using, for example, acetone as a solvent.

In the bump forming step, as shown in FIG. 10, a rosin-based solder flux is applied to the surface of the solder plating layer, and then a reflow process (for example, 230 ° C.) is performed to form a hemispherical solder bump 6A. .

In the bonding step, as shown in FIG. 11, the structure 7 formed on the substrates 2A and 2B and the solder bumps 6A formed on the thermoelectric semiconductor materials 3A and 4A in the structure manufacturing step (FIG. 6) are formed. Positioning is performed with reference to the substrate 2B and the P-type thermoelectric semiconductor material 3A, and the substrate 2A and N
The thermoelectric semiconductor materials 4A are superposed on each other. Then, the substrate 2B and the P-type thermoelectric semiconductor material 3A, and the substrate 2A and the N-type thermoelectric semiconductor material 4A are respectively heated and melted (for example, at 230 ° C.) while pressing in the bonding direction. It is fixed via the structure 7. Here, in order to increase the bonding strength, a thin rosin-based flux is applied to the tip of the solder bump 6A.

In the cutting / removing step (pillaring step), FIG.
2. As shown in FIG. 13, in the joining step (FIG. 11), the thermoelectric semiconductor materials 3A, 4A joined to the substrates 2A, 2B are cut off and unnecessary portions are removed to form the elements 3, 4. In this step, for example, a dicing blade used for cutting a silicon semiconductor or the like is used. In order to cut and remove the thermoelectric semiconductor materials 3A and 4A, the substrate 2 to which the thermoelectric semiconductor materials 3A and 4A are bonded is used.
A and 2B are adhered to an adhesive tape 13, adsorbed on a dicing stage 14, and a dicing blade is passed between solder bumps 6A formed on the end surfaces of the thermoelectric semiconductor materials 3A and 4A, and the cutting depth at that time is adjusted. , The depth at which only the thermoelectric semiconductor material 3A, 4A is cut, ie, the substrate 2
By setting up to the gap formed between the surfaces of A and 2B and the thermoelectric semiconductor materials 3A and 4A, the bottom surfaces 3b and 4b are placed on the substrates 2A and 2B via the structure 7 as shown in FIG. The elements 3 and 4 can be formed in a state where they are joined and the solder bumps 6A are formed on the upper surfaces 3a and 4a. The dicing conditions at this time were an up mode cut, a feed rate of 5 mm / sec, a water amount of 0.1 L / min, and a blade height of 0.4 mm. When cutting P-type and N-type thermoelectric materials,
In the up mode, the direction of rotation of the blade is
Since it becomes upward (B) with respect to (A), the cutting residue of the thermoelectric material can be reliably removed from the calf line. Therefore, there is no short circuit between the elements due to the remaining portion of the thermoelectric material. That is, in the production of the thermoelectric element 1,
Short circuit defects can be reduced. In addition, there is no thermoelectric material that cannot be removed, and cutting properties are improved.
It becomes possible to manufacture thin elements. That is,
By improving these matters, an element having an element size of 80 μm square and a height of 600 μm can be provided.

In the assembling process, as shown in FIG. 14, in the cutting / removing process (FIGS. 12 and 13), the substrates 2A and 2A on which the P-type and N-type elements 3 and 4 are formed, respectively.
B, with the surfaces of the elements 3 and 4 facing each other and the solder bumps 6A of the upper surfaces 3a and 4a of the elements 3 and 4 being brought into contact with the metal electrodes 5 of the other substrates 2B and 2A,
The substrates 2A and 2B are heated (for example, at 230 ° C.) while being appropriately pressed in the joining direction to melt the solder bumps 6A.
B can be joined to complete the thermoelectric element 1.
Here, in order to increase the bonding strength, the solder bumps 6A
A thin rosin-based flux is applied to the tip of.

According to such a manufacturing method, for example, the outer dimensions are 1.3 mm × 2 mm × 2.5 mm, using a dicing blade having a blade thickness of 140 μm from a thermoelectric semiconductor material 3A, 4A having a thickness of 600 μm. The number of elements is 102 in total for P-type and N-type, and the internal resistance is about 70Ω
Thus, the thermoelectric element 1 could be manufactured. here,
The thermoelectric semiconductor materials 3A and 4A are Bi-Te based sintered bodies, and the main characteristics thereof are that the P-type thermoelectric semiconductor material 3A is
Seebeck coefficient: 202 μV / K, resistivity: 0.93
mΩcm and thermal conductivity of 1.46 W / mK, while the N-type thermoelectric semiconductor material 4A has a Seebeck coefficient of -188 μV /
K, specific resistivity 0.97 mΩcm, thermal conductivity 1.61
W / mK was used.

Thus, the P-type and N-type elements 3,
4 is bonded to the two substrates 2A and 2B via the structure 7, and then the substrates 2A and 2B are bonded. Therefore, before combining the substrates 2A and 2B, the P-type and the N-type Elements 3 and 4 have a structure 7
, Accurate positioning is performed.

Further, since the dicing cutability is improved, a thin element can be formed, and a small element can be manufactured. Therefore, even with a small temperature difference, a large amount of electric power can be generated, and the thermoelectric element 1 can be used 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, the thermoelectric element 1 can be used for cooling various electronic devices such as a semiconductor laser, for example.

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. Also, element 3,
As the material of No. 4, a sintered body of a Bi-Te-based material has been described as an example, but it is also applicable to various thermoelectric semiconductor materials such as Fe-Si-based materials, Si-Ge-based materials, and Co-Sb-based materials. It is. In addition, the detailed configuration specifically shown,
The method and the like can be changed without departing from the gist of the present invention.

[0033]

According to the first aspect of the present invention, the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are bonded to different substrates, and the P-type and N-type thermoelectric semiconductor materials are improved in dicing. Since the P-type and N-type thermoelectric semiconductor materials are cut off by cutting, there is no remaining uncut portion of the P-type and N-type thermoelectric semiconductor materials. That is, for example, since the elements are not electrically connected to each other, it is possible to reduce occurrence of a short circuit failure. Also, in order to improve the dicing cutability,
A thin element can be made, and a small element can be supplied.

According to the second aspect of the present invention, the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material are bonded to different substrates, and the P-type and N-type thermoelectric semiconductor materials are cut by dicing. Since the cutting is performed, the P-type and N-type thermoelectric semiconductor materials are left uncut. That is, for example, since the elements are not electrically connected to each other, the occurrence of a short circuit can be reduced, and the yield can be improved. In addition, since it is not necessary to reduce the blade height and cut the metal electrode on the substrate, it is not necessary to cut the metal electrode and cause an electrical disconnection failure. That is, by improving these matters, occurrence of short-circuit failure and disconnection failure can be reduced, the yield can be improved, and the thermoelectric element can be easily manufactured.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing a state where an element is joined to one substrate.

FIG. 3 is a cross-sectional view showing an insulating film forming step in one example of a method for manufacturing a thermoelectric element.

FIG. 4 is a cross-sectional view showing a film forming process.

FIG. 5 is a cross-sectional view showing the same electrode manufacturing step.

FIG. 6 is a cross-sectional view showing the same structure manufacturing step.

FIG. 7 is a cross-sectional view showing the same mask forming step.

FIG. 8 is a cross-sectional view showing a Ni and solder plating process.

FIG. 9 is a cross-sectional view showing the same mask removing step.

FIG. 10 is a cross-sectional view showing the same bump forming step.

FIG. 11 is a cross-sectional view showing the same bonding step.

FIG. 12 is a cross-sectional view showing a cutting / removing step (pillaring step).

FIG. 13 is a sectional view showing a cutting / removing step (pillaring step).

FIG. 14 is a cross-sectional view showing an assembling step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermoelectric element 2A, 2B board 3 P-type element 3A P-type thermoelectric semiconductor material 4 N-type element 4A N-type thermoelectric semiconductor material 5 Metal electrode 6 Bonding material 7 Structure 8 Oxide film 9 Photo resist 10 Nickel 11 Solder 12 Dicing saw 13 Adhesive tape 14 Dicing stage

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/78 Q (72) Inventor Hirohiko Nemoto 1-8 Nakase, Mihama-ku, Chiba-shi, Chiba SII RD Center Co., Ltd. (72) Inventor Matsuo Kishi 1-8-8 Nakase, Mihama-ku, Chiba Chiba Pref. SII IRD Center Co., Ltd. (72) Inventor Michio Yamamoto 1-8-8 Nakase, Mihama-ku, Chiba Chiba Inside SII IRD Center

Claims (2)

[Claims] A PN junction pair is formed by joining a P-type element made of a P-type thermoelectric semiconductor material, an N-type element made of an N-type thermoelectric semiconductor material, and a pair of these P-type and N-type different elements. A thermoelectric element comprising two substrates having a possible metal electrode, and a bonding material for bonding the P-type and N-type elements to the metal electrode, wherein the P-type thermoelectric semiconductor material is provided at one end on the metal electrode; And the N
Bonding a thermoelectric semiconductor material to separate substrates, cutting the P-type and N-type thermoelectric semiconductor materials to form a plurality of the P-type and N-type elements on the substrate, With the substrates facing each other, the tips of the P-type and N-type elements and the metal electrodes of the opposing substrates are fixed, and in the thermoelectric element for joining these substrates, the P-type and N-type thermoelectric semiconductor materials are cut. A thermoelectric element manufactured using dicing upcut. 2. A PN junction pair is formed by joining a P-type element made of a P-type thermoelectric semiconductor material, an N-type element made of an N-type thermoelectric semiconductor material, and a pair of these different types of P-type and N-type elements. A method for manufacturing a thermoelectric element comprising two substrates having a possible metal electrode, and a bonding material for bonding a P-type and an N-type element to a metal electrode, the method comprising: Bonding the P-type thermoelectric semiconductor material and the N-type thermoelectric semiconductor material to separate substrates, and cutting the P-type and N-type thermoelectric semiconductor materials to form a plurality of the P-type and N-type elements on the substrate; Then, the two substrates are faced to each other, the tips of the P-type and N-type elements are fixed to metal electrodes of the opposing substrates, and the P-type and N-type elements are bonded together.
A method for manufacturing a thermoelectric element, comprising using an upcut of dicing to cut a mold and an N-type thermoelectric semiconductor material.