JP3205665B2 - Manufacturing method of thermoelectric conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion element which enables thermoelectric generation by the Seebeck effect and electronic cooling by the Peltier effect.

[0002]

2. Description of the Related Art A thermoelectric conversion element is manufactured by joining a P-type thermoelectric material and an N-type thermoelectric material via an electrode such as a metal to form a PN pair. This thermoelectric conversion element generates an electromotive force based on the Seebeck effect by giving a temperature difference between a pair of junctions, so as a power generator, and conversely, by flowing a current to the element, one side of the junction cools down, and the other side. There are applications such as a cooling device using the so-called Peltier effect that generates heat and a precision temperature control device.

A thermoelectric conversion element is used as a module in which a plurality of PN pairs are connected in series in order to improve the performance. The structure of this module is several hundred μm on one side
A P-type and N-type thermoelectric material piece having a rectangular parallelepiped shape of a few mm is sandwiched between two electrically insulating substrates such as alumina and aluminum nitride, and a P-type thermoelectric material piece and an N-type thermoelectric material piece are At the same time, the thermoelectric material pieces are connected in series on the substrate by electrodes made of a conductive substance such as a metal.

[0004] A method of manufacturing such a thermoelectric conversion element will be described below. FIG. 9 shows a process diagram of a conventional technique. The thermoelectric material is cut to produce a piece of material (a prism) (step 901). P-type and N-type thermoelectric material pieces are arranged in a desired arrangement (step 902). The substrate on which the wiring electrodes are installed is joined (step 903).

Next, FIG. 10 is an explanatory diagram schematically illustrating the prior art. In FIG. 10A, a plate 1021 of a P-type or N-type thermoelectric material is prepared. Next, FIG.
In (b), as a surface treatment for bonding to the substrate, 1022 layers of Ni plating are formed on both sides of the plate material.

Next, in FIG. 10C, the plate material subjected to the surface treatment is cut to produce a thermoelectric material piece 1023 (a prism) (step 901). Next, in FIG.
The mold and N-type thermoelectric material pieces are arranged in a desired arrangement. here,
The thermoelectric material pieces are placed one by one on a dedicated jig (Step 902).

Next, in FIG. 10E, an alumina substrate 1024 having a wiring electrode (3) 1025 formed thereon is formed.
Sandwich and join. This is manufactured by forming a solder 1026 on a piece of material, sandwiching the solder 1026 between alumina substrates 1024, and heating (step 903).

[0008] As described above, a method of producing and arranging the thermoelectric material pieces, that is, a method of handling each of the thermoelectric material pieces has been performed.

[0009]

However, in the conventional method of manufacturing a thermoelectric conversion element, batch processing and automation are difficult, and reduction in man-hour is not expected. In addition, in order to reduce the size or to produce an element having a large conversion capability, it is necessary to reduce the thermoelectric conversion material and increase the number of PN pairs. There was a problem that it would be a restriction on fabrication.

Accordingly, an object of the present invention is to provide a manufacturing method capable of miniaturization and mass production by using a manufacturing method by batch processing and fine processing in order to solve the conventional problems described above. is there.

[0011]

In order to solve the above-mentioned problems, the present invention relates to a method for manufacturing a thermoelectric conversion element, which includes a fine processing technique used in semiconductor manufacturing, a method of performing assembly and processing in parallel, By using a method that can handle material pieces collectively, it is possible to respond to miniaturization and mass production.

The manufacturing method of the present invention will be described below. First, a convex portion is formed on a thermoelectric material, and a mask having an opening at a joint portion is formed on a plate. Next, the thermoelectric material and the plate are bonded via a bonding agent. Then, in order to form a pillar structure, the thermoelectric material is divided. As described above, P-type and N-type pillar structures are individually manufactured. Finally, P-type and N-type pillar structures are bonded together (method 1). This step is a basic process of the present invention.

Before cutting the thermoelectric material to produce the columnar structure of the method 1, the thermoelectric material is shaved and processed for thickness (method 2). In this step, by adding a thickness processing step of the thermoelectric material in the middle of the method 1, the thickness is reduced and the columnar thermoelectric material is produced at a high density. Many thermoelectric materials are difficult-to-cut materials, and are liable to break by general single-piece machining. in this way,
The lamination of the plates facilitates thickness processing of the material.

[0014] The number of steps is reduced (method 3) except for the production of the protrusions of the thermoelectric material in methods 1 and 2. The number of steps is reduced except for the masking of the plates in Methods 1 and 2 (Method 4). Instead of bonding the P-type and N-type pillar structures in Methods 1, 2, 3, and 4, another plate is joined (Method 5). This uses a thermoelectric material that has been pre-processed by the methods 7, 8, and 9, thereby eliminating the joining of the column structure, simplifying the process, and improving the thermoelectric characteristics by increasing the density of the columnar thermoelectric material.

[0015] The number of steps is reduced except for the separation of the thermoelectric material for producing the pillar structure in Method 5 (Method 6). This is a method of pre-processing a thermoelectric material (method 7). First, a thin plate is cut out from the P-type and N-type thermoelectric material blocks and subjected to thickness processing. Next, P-type and N-type thermoelectric materials are joined alternately. At this time, the positional accuracy of P and N and the mechanical strength of the joint are important. Further, the joined thermoelectric material is cut by a joining method. Finally, the thickness of the cut thermoelectric material is processed. The thermoelectric material produced as described above is a thin plate in which P-type and N-type are alternately arranged. If this thermoelectric material is used, the density of the columnar thermoelectric material is determined by the thickness of the bonding agent. Therefore, the density of the columnar thermoelectric material can be increased, and the thermoelectric characteristics can be improved.

In addition to the manufacturing method of Method 7, as a subsequent step,
The thickness-processed material is joined again, and thickness processing is performed again (method 8). By this method, an aggregate of P-type and N-type columnar thermoelectric materials can be manufactured. This material allows the thermoelectric material to have a higher density and simplifies the assembly process of the thermoelectric conversion element.

In addition to the manufacturing methods of Methods 7 and 8, as a later step, electrode wiring is formed on at least one surface of the thermoelectric material (Method 9). This facilitates handling of the thermoelectric conversion material and further simplifies the process of assembling the thermoelectric conversion element because detailed positioning is not required. Also,
Characteristic tests before assembly are also facilitated.

[0018]

In the thermoelectric conversion element configured as described above, since assembly and processing can be performed in parallel or the thermoelectric material can be handled as one part, there is no need to work on individual columnar thermoelectric materials and batch processing is performed. It can be manufactured with. In addition, the number of assembled parts can be reduced by performing pre-processing of the thermoelectric material.

These influence not only the miniaturization of the structure and the increase in the density, but also the productivity, such as simplification of the assembling process and simplification of processing by surface processing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 shows a process diagram 1 of the present invention. In steps 105 to 101, a pillar structure is formed of P-type and N-type materials, and in step 105, these are laminated to form a structure in which PNs are alternately arranged in series. A protrusion is formed on the thermoelectric material to enhance the bonding strength with the plate and facilitate the positioning (Step 101). A mask is formed on the board as a margin for protecting the bonding agent and processing when the thermoelectric material is cut (Step 1).
02). The thermoelectric material and the plate are joined (step 103). The thermoelectric material is cut into a desired shape to form a pillar structure (Step 1).
04). Laminate P-type and N-type pillar structures (Step 10
5).

Next, FIG. 2 is an explanatory view schematically illustrating Embodiment 1 of the present invention. Example 1 is based on (method 1). In FIG. 2A, a Si substrate 201 to be a heat radiating plate or a heat absorbing plate is prepared. An oxide film is formed on the surface of the substrate in order to provide insulation. The Si substrate 201 can be an effective heat sink or heat absorbing plate because the semiconductor process can be used and the thermal conductivity is good.

Next, in FIG. 2B, a wiring electrode (1) 202 for electrically connecting a thermoelectric material was formed. In this method, three layers of Cr-Ni-Au were formed by sputtering, and were patterned by photolithography. Next, in FIG. 2C, a groove 203 is formed in the P-type or N-type thermoelectric material 204 to form a convex portion 203. The grooving 205 was performed vertically and horizontally, and the projections 203 were formed in a matrix. Groove 205 is made of thermoelectric material 2
04 on both sides. The lower side is intended to increase the bonding strength by avoiding interference with the mask on the substrate in a later process, and to position the plate and the thermoelectric material at the time of bonding. The upper side is intended for positioning when the thermoelectric material 204 is cut.

For positioning of the upper and lower surfaces, a double-sided exposure machine was used, and marks were formed with resist. In addition, a dicing saw used for dicing a semiconductor was used to form the grooves (step 101). Next, in FIG.
A mask 206 having a thickness of 20 μm was formed on the substrate. The mask 206 has a shape in which a desired place where the wiring electrode and the thermoelectric material are to be joined is opened. This is to avoid a short circuit between the electrodes due to the bonding agent and to provide a space between the Si substrate and the thermoelectric material so as to avoid the cutting of the wiring electrodes on the Si substrate by the dicing saw in the dividing step (Step 102). ).

Next, in FIG. 2E, on the substrate,
The silver paste which is the conductive bonding agent (1) 207 has just been applied. At the opening of the mask, a bonding agent (1)
207 is embedded. Next, in FIG. 2F, the substrate and the thermoelectric material were joined. Although the alignment can be easily performed because of the fitting, care must be taken to apply pressure because the thermoelectric material is brittle (step 103).

Next, in FIG. 2 (g), the thermoelectric material was cut to form a pillar structure 208. This is also Step 1
As in the case of No. 01, a method of grooving 209 using a dicing saw was used. At this time, the height is adjusted so as to cut the mask portion. Thus, the wiring electrode on the Si substrate is not cut. Further, the electrode bonding portion (mask opening) of the thermoelectric material having no pillar is in a state in which a conductive bonding agent is embedded (step 104).

Next, in FIG. 2 (h), the column structure (for example, N-type) manufactured in the above step and another type of column structure 210 (P-type) manufactured separately were joined. Bonding agent (2) 21
For 1, silver paste was used. The silver paste was applied using a stamp method so as to withstand miniaturization (see FIG. 3) (step 105).

In the thermoelectric conversion element manufactured as described above, the material density, that is, the thermoelectric characteristic is determined by the processing ability of the dicing saw. By using a dicing saw, columns having a size of 100 μm or less can be manufactured, and the material density can be greatly increased as compared with the conventional method. In this method, the thermoelectric conversion element manufactured with a column of 100 μm square is 1c
The output per m square was at least 100 times higher than that of a thermoelectric material piece of about 1 mm square.

Here, the application of the bonding agent by the stamp method used in the embodiment of the present invention will be described. FIG. 3 is an explanatory diagram schematically showing the stamp method. FIG. 3A shows the pillar structure 308 and the bonding agent (2) 311 that has been thinned.

Next, in FIG. 3B, the column structure is placed on a bonding agent. Next, in FIG.
The column structure has been separated from the bonding agent. Here, the tip of the pillar structure is in a state where the bonding agent is applied. The application amount of the bonding agent can be controlled by the viscosity of the bonding agent and the thickness when the bonding agent is extended.

Next, FIG. 4 is an explanatory view schematically illustrating Embodiment 2 of the present invention. Example 2 is based on (Method 3). 4A and 4B, the shape is the same as that of the first embodiment. Next, in FIG. 4C, the mask 406 has been manufactured (Step 10).
2).

Next, in FIG. 4D, on the substrate,
The silver paste which is the conductive bonding agent (1) 407 has just been applied. Here, since the screen printing technique was used, the bonding agent was buried only in the openings of the desired masks, and there was no unnecessary application to the periphery.

Next, in FIG. 4E, the substrate and the thermoelectric material 404 were joined. No alignment is required,
The operation was easy because a relatively thick material was used (step 103). Next, in FIG. 4F, the thermoelectric material was thinned by lapping. GC # 3000 for abrasive grains
Was used. Here, processing was performed up to 200 μm, but processing itself was possible because it was bonded to the substrate.

Next, in FIG. 4 (g), the thermoelectric material was cut to form a column structure 408. Blast was used for this processing. For this reason, the substrate-shaped mask does not act as a margin for processing as in the first embodiment, but acts as a protective film for the substrate. The column shape has a taper 412 unlike the machining.

Since the blast also processes the electrodes and the substrate, the operation must be completed before the electrodes on the substrate in the mask opening appear (step 104). Next, FIG.
In (h), the pillar structure (for example, N-type) manufactured in the above step and another type pillar structure 410 (P-type) separately manufactured were joined. Silver paste was used for the bonding agent (2) 411. The silver paste was applied using a stamp method so as to withstand miniaturization (see FIG. 3) (step 105).

Since the thermoelectric conversion element manufactured as described above is processed on the surface, the processing time can be greatly reduced. However, in the case of a thickness of 200 μm, the material density was smaller than that of the method using a dicing saw when the device was manufactured in consideration of the small aspect ratio of blasting and the taper due to the wraparound of abrasive grains. In processing in which a large aspect ratio, such as blasting, cannot be obtained in the separation method, it is necessary to reduce the thickness of the thermoelectric material in order to increase the degree of integration of the columnar thermoelectric material.

With respect to the processing conditions, in dicing, it was necessary to suppress defects due to chipping, but with blasting, there was a problem how to reduce processing unevenness. This is also considered to be a portion where the effect is reduced by reducing the thickness. Surface processing such as blasting has a large degree of freedom in the shape and arrangement of pillars, and is extremely thin in terms of characteristics and thickness processing (at least 100 μm or less)
If this can be used, it is an effective separation method for increasing the degree of integration.

FIG. 5 shows a process chart 2 of the present invention.
In this method, P-type and N-type materials are processed into one composite material. Each of the P-type and N-type materials is processed into a thin plate (Step 501). P-type and N-type materials are joined alternately (step 502). The composite material is sliced in the joining direction and processed into a thin plate (Step 503).

Next, FIG. 6 is an explanatory view schematically illustrating Embodiment 3 of the present invention. Example 3 is based on (Method 7). In FIG. 6A, a block 613 of P-type and N-type thermoelectric materials is prepared.

Next, in FIG. 6 (b), after slicing each material by a multi-blade cutting machine, finishing the thickness by lapping to produce a thin plate 614 of a thermoelectric material (step 501). . Next, in FIG. 6C, P-type 615 and N-type 616 thin plates were alternately bonded via a bonding agent (3) 617. As the bonding agent (3) 617, an insulating epoxy film adhesive having a base cloth was used. The absence of the base cloth is advantageous because the bonding layer can be made smaller, but here, the insulation is emphasized. This joint could be produced with high accuracy. Although the jig for suppressing the contact was used, it is considered that the position of the material was determined almost uniformly by the elasticity of the base cloth (step 502).

Next, in FIG. 6 (d), after performing slicing processing using a multi-blade cutting machine in the joining direction of the materials, finishing the thickness by lapping, the P-type and N-type composite materials 618 are formed. Produced. Due to the difference in hardness between the thermoelectric material and the bonding agent, a step or a gap was formed at the boundary between the thermoelectric material and the bonding agent in the lapping process. By changing the hardness and thickness of the bonding agent, it was possible to reduce the size, but it could not be completely eliminated. Although the inorganic bonding agent was better in terms of steps and gaps than the organic bonding agent, the yield due to accuracy and cracking was not good. Further, when performing the step of Method 9, it was necessary to make the gap small enough (Step 503).

The P-type and N-type composite materials produced as described above had relatively high mechanical strength and were sufficiently resistant to the subsequent steps. Next, FIG. 7 is an explanatory diagram schematically illustrating Embodiment 4 of the present invention. Example 4 is according to methods 5 and 7.

FIGS. 7A and 7B show the first embodiment.
Is the same as Next, in FIG. 7C, a mask 706 having a thickness of 20 μm was formed on the substrate using BPR. The mask 706 has a shape in which a desired place where the electrode and the thermoelectric material are to be joined is opened. This is to avoid a short circuit between the electrodes due to the bonding agent (step 102).

Next, in FIG. 7D, a silver paste as a conductive bonding agent (1) 707 has been applied to the mask opening. Next, in FIG.
The P-type and N-type composite materials 718 (prepared by the method 7) were bonded to the Si substrate (step 103).

Next, in FIG. 7F, separation was performed so that the PN sequence remained. The figure is a picture viewed from the side. Since the separation is performed only in one direction, FIG.
The shape in the same direction does not change. Dicing was used for separation (step 104). Next, in FIG. 7G, since the PN arrangement of the thermoelectric material has already been performed,
Rather than bonding the columnar structures performed by the method 1 or the like, the substrate 719 provided with the wiring electrodes was bonded to the thermoelectric material using the bonding agent (2) 711. Since the composite material has a thickness finish, the individual steps are very small, and the amount of the bonding agent (2) 711 may be small. However, since this structure does not prevent the flow of the bonding agent, the amount and the pressing pressure are reduced. Attention was required (alternative to step 105).

The thermoelectric conversion element manufactured as described above has a small number of steps in assembling, and has a high mechanical strength because the thermoelectric material is held, which is very advantageous in terms of productivity. Next, FIG. 8 shows a fifth embodiment manufactured according to the present invention. This is a schematic diagram of a P-type and N-type composite material.

Example 5 is based on Methods 8 and 9.
P-type 815 and N-type 8 are formed on a P-type and N-type composite material in which thermoelectric material pieces of P-type 815 and N-type 816 are arranged in a matrix.
The wiring electrodes (2) 820 are formed so that 16 are alternately connected.

First, the P-type and N-type composite materials of Example 3 were joined again via a joining agent. Next, it was cut by slicing in the joining direction and finished by lapping to obtain a matrix-type P-type and N-type composite material. The silver paste was applied to the wiring electrode (2) 820 by screen printing.

The P-type and N-type composite materials were used for producing a thermoelectric conversion element according to Method 6. According to this method, assembling and processing are performed separately, so that the cost can be reduced and the yield can be improved. Furthermore, since the evaluation of the characteristics of the thermoelectric conversion material alone becomes easy, there is also an effect in terms of reliability. Also, by connecting all the material pieces with the electrode wiring on the composite material,
A highly reliable thermoelectric conversion element could be manufactured more easily.

Finally, the points that were not sufficient in the above description will be described together. In the thickness processing performed in the method 2 or the like, the substrate and the material were sometimes peeled off due to insufficient strength of the joint. In the case of a combination in which a mask material and a bonding agent are bonded, the problem of peeling is small, but it is basically better to use a thermoelectric material provided with a convex portion.

In the method of not producing a mask as in the method 4, etc., attention was paid to alignment and short-circuiting due to a bonding agent. In addition, blasting and etching methods were also effective for producing the convex portions. Further, if it is conductive, it can be formed of another material. There was no problem with the structure produced by Ni plating or silver paste.

Also, one of the projections formed on both sides is unnecessary when an alignment mark or the like is formed because the main purpose is alignment at the time of separation. However, this does not apply for the purpose of strengthening the joining of composite materials that do not require division. If the mask material is insulating, it is organic,
It can be either inorganic.

The application of the bonding agent depends on the process.
Either the substrate side or the material side may be used. It is preferable that the bonding agent does not have an extremely different coefficient of thermal expansion or that can be processed at a low temperature. Although it could be manufactured by using solder, particularly in a device having a large area, poor bonding was likely to occur.

Further, although etching was also used for the division, the result was the same as that of blasting. In addition, there was no major problem in any method such as a thin film and a thick film for producing a wiring electrode on the substrate side, and the method was selected in terms of accuracy and cost. However, as for the wiring electrodes on the composite thermoelectric material, many electric wires appear in a thin film, and a method using a thick film was effective.

[0054]

According to the present invention, as described above, the construction and processing are performed simultaneously or the thermoelectric material is made into a single component, so that the work object becomes large and the handling becomes easy. And batch processing, surface processing, etc. became possible, and processing time was shortened. In addition, since the degree of freedom of the structure by the surface processing, the low-temperature processing and the like is increased, the process design is facilitated.

Further, according to the methods 8 and 9, the evaluation of thermoelectric characteristics during the process can be easily performed. Further, since the processing of the thermoelectric material and the assembly of the thermoelectric conversion element can be performed separately, there is also an effect in optimizing the working environment. As described above, the manufacturing method of the present invention is effective in reducing the size, thickness, mass production, and improving the productivity, reliability, and yield of the thermoelectric conversion element.

[Brief description of the drawings]

FIG. 1 is a process diagram 1 of the present invention.

FIG. 2 is an explanatory view schematically showing Example 1 of the present invention.

FIG. 3 is an explanatory view showing application of a bonding agent by a stamp used in an example of the present invention.

FIG. 4 is an explanatory diagram schematically showing a second embodiment of the present invention.

FIG. 5 is a process drawing 2 of the present invention.

FIG. 6 is an explanatory view schematically showing a third embodiment of the present invention.

FIG. 7 is an explanatory diagram schematically showing a fourth embodiment of the present invention.

FIG. 8 is an explanatory diagram schematically showing a fifth embodiment of the present invention.

FIG. 9 is a process chart of a conventional method.

FIG. 10 is an explanatory diagram schematically showing a conventional method.

[Explanation of symbols]

 201, 401, 701 Si substrate 202, 402, 702 Wiring electrode (1) 203 Convex part 204, 404 Thermoelectric material 205, 209 Groove 206, 706 Mask 207, 407, 707 Bonding agent (1) 208, 308, 408 Column Structure 210, 410 Other type column structure 211, 311, 411, 711 Bonding agent (2) 412 Taper 613 Block of thermoelectric material 614 Thin plate of thermoelectric material 615, 815 P type 616, 816 N type 617 Bonding agent (3) 618, 718 P-type, N-type composite material 719 Substrate 820 Wiring electrode (2) 1021 Plate 1022 Ni plating 1023 Thermoelectric material piece 1024 Alumina substrate 1025 Wiring electrode (3) 1026 Solder

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-299585 (JP, A) JP-A-58-64075 (JP, A) JP-A-46-773 (JP, A) JP-A-53- 95588 (JP, A) JP-A-61-168232 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 35/34 H01L 35/32

Claims (6)

(57) [Claims] 1. a first step of forming a plurality of protrusions on a thermoelectric material; a second step of joining an electrode formed on a substrate to the protrusions; and a column structure by cutting the thermoelectric material. A third step of fabricating the thermoelectric material, the thermoelectric material is made of a different type of thermoelectric material, and the opposing substrate and the substrate, which are provided in a columnar shape, are opposed to each other. And a fourth step of joining different kinds of thermoelectric materials. A method for producing a thermoelectric conversion element, comprising: 2. The method according to claim 2, further comprising, before the second step, a step of forming a mask having an opening on the substrate provided with the electrodes, and the second step includes: The method for producing a thermoelectric conversion element according to claim 1, wherein the method is a joining step. 3. The method for manufacturing a thermoelectric conversion element according to claim 1, further comprising a step of performing thickness processing of the thermoelectric material after the second step. 4. The method according to claim 3, wherein in the third step, a columnar structure including the protrusion is formed by removing a thermoelectric material in a gap between the protrusions formed in the thermoelectric material. Item 3. The method for producing a thermoelectric conversion element according to item 1 or 2. 5. A step of electrically connecting an electrode formed on a substrate to a thermoelectric material; a step of cutting the thermoelectric material to produce a thermoelectric material having a columnar structure; A step in which a counter substrate provided with a columnar thermoelectric material and the substrate are opposed to each other, and an electrode of the counter substrate and the thermoelectric material of the columnar structure are electrically connected to an electrode on the substrate and the different thermoelectric material; A method for manufacturing a thermoelectric conversion element, comprising: 6. A step of forming a mask having an opening on a substrate provided with an electrode, a step of providing a conductive bonding agent in the opening, and applying a thermoelectric material to the electrode via the bonding agent. An electrical connection step; a step of cutting the thermoelectric material to produce a columnar thermoelectric material; and opposing the opposing substrate provided with a columnar thermoelectric material different from the thermoelectric material to the substrate. Electrically connecting the electrode on the counter substrate and the thermoelectric material having the columnar structure to the electrode on the substrate and the different thermoelectric material.