JP5865721B2 - Thermoelectric module - Google Patents

Description

  The present invention relates to a thermoelectric module suitably used for temperature control, waste heat power generation, and the like of a thermostatic bath, a refrigerator, an automobile seat cooler, a semiconductor manufacturing apparatus, a laser diode, and the like.

  The thermoelectric element utilizes the Peltier effect that when a current is passed through a PN junction pair consisting of a p-type semiconductor and an n-type semiconductor, one end side of each semiconductor generates heat and the other end side absorbs heat. The thermoelectric module is capable of precise temperature control, is small and has a simple structure, and is widely used in cooling devices such as freonless cooling devices, photodetectors, semiconductor manufacturing devices, laser diode temperature control devices, etc. Has been.

  Moreover, since the thermoelectric element can also extract electric power when there is a temperature difference between both ends, it is expected to be used for a power generation device such as exhaust heat recovery power generation.

Thermoelectric modules used near room temperature are P-type thermoelectric elements and N-type elements made of thermoelectric materials made of A ₂ B ₃ type crystals (A is Bi and / or Sb, B is Te and / or Se). The thermoelectric element is configured to include a pair. For example, as a thermoelectric material exhibiting particularly excellent performance, a thermoelectric material made of a solid solution of Bi ₂ Te ₃ and Sb ₂ Te ₃ (antimony telluride) is used for a P-type thermoelectric element, and an N-type thermoelectric element is used. Is a thermoelectric material made of a solid solution of Bi ₂ Te ₃ and Bi ₂ Se ₃ (bismuth selenide).

  Then, a pair of support substrates arranged so as to face each other made of an insulator such as ceramics so as to electrically connect the P-type thermoelectric element and the N-type thermoelectric element formed of such a thermoelectric material in series. The P-type thermoelectric element and the N-type thermoelectric element are joined to each other with the wiring conductors arranged on the opposed inner main surfaces of the pair of support substrates respectively. Furthermore, a thermoelectric module is manufactured by joining a heat exchange member such as a fin to the outer main surface of the support substrate with a bonding material such as an adhesive or solder in order to collect and dissipate heat through a medium such as air or water. (For example, refer to Patent Document 1).

JP 2007-35907 A

  However, in the joining of the heat exchange member and the support substrate as shown in Patent Document 1, when the heat source suddenly rises or falls in temperature, the joining material may crack, which may reduce the power generation amount of the thermoelectric module. there were.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoelectric module in which the power generation capacity is not easily lowered for a long time even by a rapid temperature change of a heat source.

The present invention provides a pair of support substrates disposed so as to face each other, wiring conductors provided on the inner main surfaces facing each other of the pair of support substrates, and inner main surfaces facing each other of the pair of support substrates. A plurality of thermoelectric elements arranged so as to be electrically connected by the wiring conductor between the surfaces, and attached to the outer main surface of at least one of the pair of support substrates via a bonding material , A heat exchange having a plurality of standing portions extending in a direction perpendicular to the main surface of the support substrate and a bottom portion connecting every other end of the adjacent standing portions on the support substrate side when viewed in a section. region and the member, and having a, and the Kutsugaeso Let covering the surface area of the bonding material which is not covered with the heat exchange member, the coating layer is, excluding the bottom side of the upright direction in the standing portion thermoelectric, characterized in that not provided in the It is a joule.

  Here, it is preferable that the coating layer is in contact with the bonding material and the heat exchange member.

  Moreover, it is preferable that the said coating layer has covered the surface area | region of the joining material along the outer peripheral part of the said heat exchange member.

Also, preferably before Symbol coating layer is provided so as to be filled between the bottom portion and the bottom portion.

  Moreover, it is preferable that the said coating layer is provided to the position higher than the upper surface of the said bottom part.

  Moreover, it is preferable that the said coating layer is provided also on the said bottom part.

  Moreover, it is preferable that the said heat exchange member is each attached to the outer main surface of both support substrates.

  According to the present invention, the bonding material for bonding the support substrate and the heat exchange member has a coating layer on the surface of the region not covered with the heat exchange member, thereby improving the bonding strength and increasing the heat capacity. To do. Therefore, it is possible to realize a thermoelectric module in which cracks are prevented from entering the bonding material even under an environment in which a rapid temperature change of the heat source occurs, and the power generation capacity is not easily lowered for a long time.

It is sectional drawing which shows an example of embodiment of the thermoelectric module of this invention. It is the perspective view which decomposed | disassembled some thermoelectric modules shown in FIG. It is sectional drawing which shows the principal part of the other example of embodiment of the thermoelectric module of this invention.

  Hereinafter, the example of embodiment of the thermoelectric module of this invention is demonstrated.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of a thermoelectric module of the present invention, and FIG. 2 is an exploded perspective view of a part of the thermoelectric module shown in FIG.

  The thermoelectric module shown in FIG. 1 and FIG. 2 includes a pair of support substrates 1 arranged so as to face each other, a wiring conductor 2 provided on each of the opposing main surfaces of the pair of support substrates 1, and a pair of A plurality of thermoelectric elements 3 arranged so as to be electrically connected by wiring conductors 2 between the opposing inner main surfaces of the support substrate 1, and at least one support substrate 1a of the pair of support substrates 1 And a heat exchange member 5 attached to the main surface via the bonding material 4, and has a coating layer 6 so as to cover the surface region of the bonding material 4 not covered with the heat exchange member 5. It is a thermoelectric module.

A pair of support substrates 1 (1a, 1b) arranged so as to face each other is a substrate (for example, a thickness) in which a copper plate is bonded to the outer main surface of an epoxy resin plate (substrate body) to which an alumina filler is added, for example. And a support substrate 1a, 1b disposed so as to face each other. This pair of support substrates 1
(1a, 1b) is formed so that the dimensions when viewed in plan are, for example, 40 to 50 mm in length, 20 to 40 mm in width, and 0.05 to 2.0 mm in thickness. The support substrate 1 may have a configuration in which a metal plate such as copper is bonded to the outer main surface of a substrate body made of a ceramic material such as alumina or aluminum nitride, such as copper, silver, or silver-palladium. Alternatively, an insulating layer made of epoxy resin, polyimide resin, alumina, aluminum nitride, or the like may be provided on the inner main surface of the substrate body made of the conductive material.
Wiring conductors 2 are provided on the inner main surfaces of the pair of support substrates 1 (1a, 1b) facing each other. The wiring conductor 2 is formed, for example, by etching a copper plate bonded to the inner main surface of the support substrate 1 into a wiring pattern, and between adjacent P-type thermoelectric elements 3a and N-type thermoelectric elements 3b in series. An electrical connection is provided. The material for forming the wiring conductor 2 is not limited to copper, and may be a material such as silver or silver-palladium.

Thermoelectric elements 3 (P-type thermoelectric elements 3a and N-type thermoelectric elements 3b) are electrically connected by wiring conductors 2 between the inner main surfaces of the pair of supporting substrates 1 (1a, 1b) facing each other. Multiple sequences are arranged. The thermoelectric element 3 (P-type thermoelectric element 3a, N-type thermoelectric element 3b) is a thermoelectric material made of A ₂ B ₃ type crystal (A is Bi and / or Sb, B is Te and / or Se), preferably bismuth ( Bi) The main body is formed of a tellurium (Te) thermoelectric material. Specifically, the P-type thermoelectric element 3a is formed of, for example, a thermoelectric material made of a solid solution of Bi ₂ Te ₃ (bismuth telluride) and Sb ₂ Te ₃ (antimony telluride), and the N-type thermoelectric element 3b is For example, it is formed of a thermoelectric material made of a solid solution of Bi ₂ Te ₃ (bismuth telluride) and Bi ₂ Se ₃ (bismuth selenide).

Here, the thermoelectric material to be the P-type thermoelectric element 3a is a P-type forming material composed of Bi _, Sb and Te once melted and solidified in one direction by the Bridgman method, for example, a cross section having a diameter of 1 to 3 mm. It is a circular rod-shaped body. Further, the thermoelectric material to be the N-type thermoelectric element 3b is an N-type forming material composed of Bi, Te and Se once melted and solidified in one direction by the Bridgman method, for example, a cross section having a diameter of 1 to 3 mm. It is a circular rod-shaped body.

  After coating a resist for preventing the plating from adhering to the side surfaces of these thermoelectric materials, the wire is cut into a width of, for example, 0.3 to 5.0 mm using a wire saw. Next, the Ni layer is formed only on the cut surface by, for example, electrolytic plating, the Sn layer is formed thereon, and the resist is peeled off with the solution, whereby the thermoelectric element 3 (P-type thermoelectric element 3a, N-type thermoelectric element). 3b) can be obtained.

  The shape of the thermoelectric element 3 (P-type thermoelectric element 3a, N-type thermoelectric element 3b) may be cylindrical, quadrangular, or polygonal, but in order to avoid stress concentration associated with expansion and contraction during use, A columnar shape is preferred.

  As shown in FIG. 2, a plurality of the thermoelectric elements 3 are arranged vertically and horizontally, for example, at intervals of 0.5 to 2.0 mm and 0.5 to 2.0 times the thermoelectric element size (diameter). The thermoelectric elements 3 (P-type thermoelectric element 3a and N-type thermoelectric element 3b) are joined to the wiring conductor 2 by a solder paste applied in the same pattern as the wiring conductor 2, and a plurality of thermoelectric elements 3 arranged in the wiring The conductors 2 are electrically connected in series.

  A heat exchange member 5 is attached to the outer main surface of at least one of the pair of support substrates 1 via a bonding material 4. In FIG. 1, a heat exchange member 5 is attached to the outside of both support substrates 1a and 1b via a bonding material 4.

Examples of the bonding material 4 include Sn-Bi solder, Sn-Sb solder, Sn-Ag-C.
u-based solder or the like is used.

  As the heat exchange member 5, copper, aluminum, iron or the like having high thermal conductivity is usually used. For applications in the region exceeding 1000 ° C. (for example, thermoelectric power generation used in a waste heat furnace or the like), silicon nitride or the like is used. Ceramics are also used. In addition, because the heat is transferred to liquids such as water and organic solvents, and gases such as air and nitrogen, many corrugated fins and needle pins on the wave stand to increase the surface area per unit area. The shape etc. which are are preferable.

  And the thermoelectric module of this invention has the coating layer 6 so that the surface area | region of the joining material 4 which is not covered with the heat exchange member 5 may be covered.

  The coating layer 6 is made of a resin material such as an epoxy resin, a polyimide resin, or silicone, and is formed to have a thickness of 10 to 100 μm, for example. As a method for forming the coating layer 6, the heat exchange member 5 and the support substrate 1 are bonded to each other, and then formed on the surface of the bonding material 4 by spray coating or dispenser coating.

  Further, the coating layer 6 may be formed of a flux contained in the bonding material 4 instead of the resin. In this case, a solder using a flux having a halogen content of 0.1% or less is used as the bonding material 4, and when the heat exchange member 5 and the support substrate 1 are soldered together, the surface flux component forms the coating layer 6. Become.

  In thermoelectric power generation, power is generated by creating a temperature difference between opposing surfaces of the thermoelectric module. Therefore, one surface of the thermoelectric module absorbs heat from the heat source, and the other surface is cooled by water cooling, air cooling, or the like. The heat source used here is not a constant amount of heat such as a furnace for industrial waste, an industrial furnace, or waste heat for automobiles, but most of it has a change with time. Therefore, when the rapid temperature change occurs, the bonding material 4 is cracked by the thermal stress, the thermal resistance is increased, the amount of heat transmitted to the thermoelectric element 3 is decreased, and the power generation amount may be decreased as a result.

  On the other hand, the thermoelectric module comprised like this invention improves the joining strength of the support substrate 1 and the heat exchange member 5, and heat capacity increases. Therefore, even in an environment where a rapid temperature change of the heat source has occurred, cracks in the bonding material 4 are suppressed, and a decrease in power generation performance can be suppressed.

  Here, the coating layer 6 is preferably in contact with the bonding material 4 and the heat exchange member 5. The amount of heat is transferred from the heat source to the heat exchange member 5 through gas, and then transferred in the order of the bonding material 4, the support substrate 1, the wiring conductor 2, and the thermoelectric element 3. By having the coating layer 6, the heat transfer path from the heat exchange member 5 to the support substrate 1 increases, so that the bonding material 4 is not locally overheated, so that the stress on the bonding material 4 can be reduced. Therefore, generation | occurrence | production of a crack can be suppressed and power generation performance fall can be prevented.

  Further, it is desirable that the covering layer 6 covers the surface region of the bonding material 4 along the outer peripheral portion of the heat exchange member 5.

  Since the support substrate 1, the bonding material 4, and the heat exchange member 5 on the high temperature side tend to spread due to thermal expansion, the thermal stress at the outer peripheral portion of the thermoelectric module is maximized. Therefore, since stress is repeatedly applied to the outer peripheral portion of the thermoelectric module in response to a rapid temperature change of the heat source, there is a high possibility that a power generation performance is deteriorated due to cracks. On the other hand, since the strength is improved by forming the covering layer 6 so as to cover the surface region of the bonding material 4 on the outer peripheral portion of the thermoelectric module, the occurrence of cracks can be suppressed.

  As shown in FIG. 3, the heat exchange member 5 includes a plurality of standing portions 51 extending in a direction perpendicular to the main surface of the support substrate 1 and a support substrate of the adjacent standing portions 51 as viewed in a cross section. It is desirable that the covering layer 6 is provided so as to be filled between the bottom portion 52 and the bottom portion 52 that connects every other end portion on the side.

  The amount of heat from the heat source includes heat transfer through gas and radiant heat. As the bonding material 4, for example, Sn—Bi solder, Sn—Sb solder, Sn—Ag—Cu solder, and the like are used, but any material system hardly absorbs radiant heat and efficiently radiates heat from a heat source. Hard to absorb.

  As in the present invention, the heat exchanging member 5 has a shape in which a single plate is bent, and a plurality of standing portions 51 (fins) extending in a direction perpendicular to the main surface of the support substrate 1 are adjacent to each other. A bottom portion 52 that connects every other end of the portion 5 on the support substrate side, and the covering layer 6 is filled between the bottom portions 52 and 52 so that the absorption rate of the radiant heat from the heat source is increased. Can be improved. Therefore, the amount of heat absorbed increases and the amount of power generation improves.

  Further, as shown in FIG. 3, it is desirable that the covering layer 6 is provided up to a position higher than the upper surface of the bottom portion 52.

  For example, the thickness of the heat exchange member 5 (the thickness of the bottom 52) is 5 to 150 μm, the thickness of the bonding material 4 is 50 to 200 μm, and covers the surface region of the bonding material 4 that is not covered with the heat exchange member 5. The coating layer 6 to be provided has a thickness of 100 μm to 5.0 mm so as to reach a position higher than the upper surface of the bottom portion 52.

  By increasing the heat capacity due to the provision of the coating layer 6, the in-plane temperature of the support substrate 1 becomes uniform, and the power generation performance is improved. Furthermore, the absorption rate of radiant heat is improved, and the power generation performance is improved.

  Although not shown, it is desirable that the covering layer 6 is also provided on the bottom 52. According to this structure, since the radiant heat from the upper part of the standing part 51 (fin) can be absorbed, electric power generation performance improves.

  Further, the heat exchange member 5 may be attached to the outer main surface of both the support substrates 1.

  For example, in the case of using the thermoelectric module by reversing the high temperature side and the low temperature side without fixing, it is desirable to attach the heat exchange member 5 to each of the outer main surfaces of both support substrates 1. In some cases, repeated thermal stresses due to temperature differences occur in the bonding material 4 on both sides. Therefore, the presence of the coating layer 6 so as to cover the surface region of each bonding material 4 not covered with the heat exchange member 5 suppresses cracks in the bonding material 4 on both sides and suppresses a decrease in power generation amount. can do.

  The thermoelectric module described above can be manufactured as follows.

  First, the thermoelectric element 3 (P-type thermoelectric element 3a and N-type thermoelectric element 3b) and the support substrate 1 are joined.

  As shown in FIG. 2, a solder paste is applied to at least a part of the wiring conductor 2 formed on the support substrate 1 (1b) to form a solder layer. Here, as a coating method, a screen printing method using a metal mask or a screen mesh is preferable in terms of cost and mass productivity.

  Next, the thermoelectric elements 3 are arranged on the surface of the wiring conductor 2 on which the solder layer is formed. The thermoelectric element 3 needs to arrange two types of elements, a P-type thermoelectric element 3a and an N-type thermoelectric element 3b. Any known technique may be used as a joining method, but the P-type thermoelectric element 3a and the N-type thermoelectric element 3b are arranged by a transfer method in which each of the P-type thermoelectric element 3a and the N-type thermoelectric element 3b is separately transferred to a jig that has been drilled. After that, a method of transferring and arranging on the support substrate 1 (1b) is simple and preferable.

  After the thermoelectric elements 3 (P-type thermoelectric elements 3a and N-type thermoelectric elements 3b) are arranged on the support substrate 1 (1b), the thermoelectric elements 3 (P-type thermoelectric elements 3a and N-type thermoelectric elements 3b) are opposite to the upper surface. The support substrate 1 (1a) is installed.

  Specifically, a solder layer is formed on the surface of the wiring conductor 2 on the upper surface of the thermoelectric elements 3 (P-type thermoelectric element 3a and N-type thermoelectric element 3b) arranged on the wiring conductor 2 provided on the support substrate 1b. The formed and coated support substrate 1a is soldered by a known technique. The soldering method may be any of reflow oven or heating with a heater. However, when resin is used for the support substrate 1, the solder and the thermoelectric element 3 (P-type thermoelectric element 3a) may be heated while applying pressure to the upper and lower surfaces. And N-type thermoelectric element 3b) is preferable for improving the adhesion.

  Next, the heat exchange member 5 is attached to at least one of the pair of support substrates 1 (1a, 1b) with the bonding material 4. The shape and material of the heat exchange member 5 to be used differ depending on the application. Here, copper fins are preferable in terms of high thermal conductivity, and when heat from a heat source is transferred through a gas such as air, the fins are formed in a wavy shape so that the area in contact with the gas increases. Is desirable.

  Next, an epoxy resin or the like is poured into the portion where the bonding material 4 is exposed and, if necessary, between the bottom portion 52 and the bottom portion 52 or on the bottom portion 52, and the coating layer 6 is formed.

  Finally, a lead wire (not shown) for energizing the wiring conductor 2 is joined with a soldering iron and a laser or the like to obtain the thermoelectric module of the present invention.

  Hereinafter, the present invention will be described in more detail with reference to examples.

First, a P-type thermoelectric material and an N-type thermoelectric material made of Bi, Sb, Te, and Se were melted and solidified by the Bridgman method to produce a rod-shaped material having a circular section of 1.8 mm in diameter. Specifically, the P-type thermoelectric material is made of a solid solution of Bi ₂ Te ₃ (bismuth telluride) and Sb ₂ Te ₃ (antimony telluride), and the N-type thermoelectric material is Bi ₂ Te ₃ (bismuth telluride). And Bi ₂ Se ₃ (bismuth selenide). Here, in order to roughen the surface, the surfaces of the rod-shaped P-type thermoelectric material and N-type thermoelectric material were etched with nitric acid.

  Next, the rod-shaped P-type thermoelectric material and the rod-shaped N-type thermoelectric material coated with the coating layer are cut with a wire saw so as to have a height (thickness) of 1.6 mm, and the P-type thermoelectric element and N A mold thermoelectric element was obtained. The obtained P-type thermoelectric element and N-type thermoelectric element formed a nickel layer on the cut surface by electrolytic plating.

  Next, a support substrate made of Cu (length 40 mm × width 40 mm × thickness 200 μm) having an insulating layer made of epoxy resin formed on one main surface and having a thickness of 80 μm is prepared, and a wiring conductor having a thickness of 105 μm is formed on the insulating layer. Formed. Then, 95Sn-5Sb solder paste was screen-printed on the wiring conductor.

  Furthermore, 160 thermoelectric elements were arranged on the solder paste using a mounter so that the P-type thermoelectric elements and the N-type thermoelectric elements were electrically in series. The P-type thermoelectric elements and N-type thermoelectric elements arranged as described above are sandwiched between two supporting substrates, heated in a reflow furnace while applying pressure to the upper and lower surfaces, and the wiring conductor and thermoelectric elements are connected via solder. And joined.

  Next, a heat exchange member (copper fin) was attached to the support substrate with a bonding material.

  Here, as the thermoelectric module of sample 1 (comparative example), a thermoelectric module of sample 2 (invention example) was prepared by forming a coating layer on the surface region of the bonding material not covered with the heat exchange member. A module having a coating layer formed on the surface region of the bonding material not covered with the heat exchange member was produced. The coating layer was formed by pouring an epoxy resin between the fin and the support substrate and curing the coating layer, and the thickness was about 50 μm.

  Each assembled thermoelectric module was evaluated.

  As an evaluation method, 20 samples 1 each having no coating layer and 2 samples 2 having a coating layer were prepared, a temperature difference of about 200 ° C. was applied to the thermoelectric module in air, and the degree of power generation deterioration was compared. Specifically, a 40mm square heater block is placed on one side of the fin, and the fin is heated to adjust the output so that the maximum temperature is 220 ° C. It was. The other fin was placed in water flowing at 20 ° C. and 5 L / min.

  When the power generation amount after one cycle and after 5000 cycles was compared, the power generation amount before the test was 9.2 W on the average for sample 1 and 9.7 W on the average for sample 2. It was found that the power generation amount increased by 5%.

  In addition, when the power generation amount at 5000 cycles was compared, Sample 1 had an average of 8.1 W and 12% power generation decreased, whereas Sample 2 had an average of 9.5 W, and there was a coating layer. It was found that the amount of power generation was less than 1%.

  In addition, when the external appearance after 5000 cycles of the sample 1 is investigated, it is inferred that cracks are observed in the solder between the fin and the support substrate, and tensile stress is applied to the solder. From the above results, it can be seen that the sample 2 of the embodiment of the present invention is more reliable than the sample 1 of the comparative example, such as reversal energization in a constant temperature and high humidity.

1, 1a, 1b Support substrate 2 Wiring conductor 3 Thermoelectric element 3a P-type thermoelectric element 3b N-type thermoelectric element 4 Bonding material 5 Heat exchange member 51 Standing portion 52 Bottom

Claims (7)

Between a pair of support substrates disposed so as to face each other, wiring conductors respectively provided on the inner main surfaces facing the pair of support substrates, and the inner main surfaces facing the pair of support substrates, A plurality of thermoelectric elements arranged so as to be electrically connected by the wiring conductor and at least one of the pair of support substrates are attached to the outer main surface of the support substrate via a bonding material, and viewed in one section. A plurality of upright portions extending in a direction perpendicular to the main surface of the support substrate, and a bottom portion connecting every other end portion of the adjacent upright portions on the support substrate side , and the Kutsugaeso Let covering the surface area of the bonding material which is not covered by the heat exchange member, and having a, the coating layer is provided in a region excluding the bottom side of the upright direction in the standing portion thermoelectric module, wherein the non   The thermoelectric module according to claim 1, wherein the coating layer is in contact with the bonding material and the heat exchange member.   The thermoelectric module according to claim 1, wherein the coating layer covers a surface region of the bonding material along an outer peripheral portion of the heat exchange member. The thermoelectric module according to any one of claims 1 to 3 before Symbol coating layer and being provided so as to be filled between the bottom portion and the bottom portion.   The thermoelectric module according to claim 4, wherein the coating layer is provided up to a position higher than an upper surface of the bottom portion.   The thermoelectric module according to claim 4, wherein the covering layer is also provided on the bottom portion.   The thermoelectric module according to claim 1, wherein the heat exchange member is attached to each of main surfaces on the outer sides of both support substrates.