JP2005217028A - Thermoelectric conversion module and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module in which variation of bonding strength of power supply wiring is suppressed, power supply wiring cannot be removed and stable loading is realized. <P>SOLUTION: The thermoelectric conversion module is provided with a support substrate, a plurality of thermoelectric conversion elements arranged on the support substrate, a wiring conductor which electrically connect the thermoelectric conversion elements, an outer connection terminal which is electrically connected to the wiring conductor, and a power supply wiring which is electrically connected to the outer connection terminal and supplies power. A diffusion layer of a power supply wiring component with thickness not less than 0.1 μm is formed in solder joining power supply wiring to the outer connection terminal, and the diffusion layer exists for 20% or above of a joined area of power supply wiring. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoelectric conversion module suitably used for temperature control, cold insulation, and power generation, and a method for manufacturing the same.

  The thermoelectric conversion element utilizes the Peltier effect that one end generates heat and the other end absorbs heat when a current is passed through a PN junction pair composed of a P-type semiconductor and an N-type semiconductor. Is capable of precise temperature control, is small and has a simple structure, and is expected to be widely used for electronic cooling elements such as freonless cooling devices, photodetectors, semiconductor manufacturing equipment, and laser diode temperature control. Yes.

  On the other hand, when a temperature difference is given to both ends of the thermoelectric conversion element, it has a characteristic that a voltage is generated, and is expected to be used for exhaust heat recovery power generation and the like.

  As shown in FIG. 1, for example, the structure of the thermoelectric module includes wiring conductors 3a and 3b formed on the surfaces of the support substrates 1a and 1b, respectively, and further includes an N-type thermoelectric conversion element 2a and a P-type thermoelectric conversion element 2b. It joins with the solder 6 so that the several thermoelectric conversion element 2 may be clamped.

  These thermoelectric conversion elements 2 are connected by wiring conductors 3 a and 3 b so as to be electrically in series, and further connected to the external connection terminal 4. A power supply wiring 5 is connected to the external connection terminal 4 by solder 6 so that power is supplied from the outside.

A thermoelectric module _{2 made of} A ₂ B ₃ type crystal (A is Bi and / or Sb, B is Te and / or Se) is used for the cooling thermoelectric module used near room temperature from the viewpoint of excellent cooling characteristics. Commonly used.

A solid solution of Bi ₂ Te ₃ and Sb ₂ Te ₃ is shown in the N-type thermoelectric conversion element 2a, and a solid solution of Bi ₂ Te ₃ and Bi ₂ Se ₃ is shown in the P-type thermoelectric conversion element 2b. Therefore, this A ₂ B ₃ type crystal (A is Bi and / or Sb, B is Te and / or Se) is widely used for the thermoelectric conversion element 2.

  Further, copper electrodes are used for the wiring conductors 3a and 3b. A plurality of N-type thermoelectric conversion elements 2a and P-type thermoelectric conversion elements 2b obtained in this way are electrically connected in series.

Furthermore, a power supply wiring 5 made of a lead wire or the like is connected to the external connection terminal 4 by solder 6 to form a thermoelectric conversion module 11. The connection of the power supply wiring 5 has been proposed to be heat-bonded with a laser beam in order to improve the short-circuit problem and workability (see Patent Document 1).
Japanese Patent No. 2583149

  However, when the thermoelectric conversion module is mounted on a package or the like, there is a problem that the power supply wiring may be taken. As a result of earnest investigation and analysis of this phenomenon, the inventor of the present patent has found that there are variations in the bonding strength between the power supply wiring and the solder, and the strength is insufficient.

  Accordingly, an object of the present invention is to provide a thermoelectric conversion module that is stabilized by suppressing variations in bonding strength of power supply wirings, and thus can be stably mounted without taking off power supply wirings. .

  In view of the above, the present invention provides a support substrate, a plurality of thermoelectric conversion elements arranged on the support substrate, a wiring conductor that electrically connects the thermoelectric conversion elements, and an electrical connection with the wiring conductor. In the thermoelectric conversion module having the external connection terminal and the power supply wiring that is electrically connected to the external wiring terminal and supplies power, the solder connecting the power supply wiring to the external connection terminal has a thickness of 0.1 μm or more The power supply wiring component diffusion layer is formed, and the diffusion layer exists in 20% or more of the bonded area.

  Further, the bonding strength of the power supply wiring is 2N or more.

  In addition, the interface between the diffusion layer and the non-diffusion layer of the power supply wiring component has a wave shape.

  Further, the diffusion layer of the power supply wiring component is denser than the surrounding non-diffusion layer.

  Further, the power supply wiring is a column or block shape.

  The power supply wiring is joined at a temperature of 103 to 130% of the solder melting temperature.

  In the present invention, a diffusion layer of a power supply wiring component having a thickness of 0.1 μm or more is formed on the solder for joining the power supply wiring to the external connection terminal, and the diffusion layer is present in 20% or more of the bonded area. By doing so, the power supply wiring and the solder are firmly coupled, so that there is no need to remove the power supply wiring during the mounting operation to the package or the like, and a thermoelectric conversion module that enables stable mounting can be provided. In particular, when the bonding strength of the power supply wiring is 2N or more, a thermoelectric conversion module that enables stable mounting can be provided.

  In addition, the present invention can improve the bonding strength because the interface between the diffusion layer and the non-diffusion layer of the power supply wiring component has a wave shape, so that thermoelectric conversion enables more stable mounting. Modules can be provided.

  In addition, the present invention can provide a thermoelectric conversion module that enables more stable mounting because the diffusion layer is denser than the surrounding non-diffusion layer.

  Further, the present invention provides a thermoelectric conversion module that can be mounted by wire bonding or the like because the power supply wiring is in the form of a pillar or a block, and therefore, the power supply wiring is harder to be removed, and thus enables stable mounting. Can be provided.

  Moreover, the thermoelectric conversion module of the present invention enables stable mounting by joining the power supply wiring at a temperature of 103 to 130% of the solder melting temperature.

  The present invention will be described based on the following embodiments.

  FIG. 1 shows an embodiment of a thermoelectric module of the present invention.

  As shown in FIG. 1, the thermoelectric module of the present invention has wiring conductors 3a and 3b formed on the surfaces of a lower support substrate 1a and an upper support substrate 1b, respectively, and an N-type thermoelectric conversion element 2a and a P-type thermoelectric conversion. A plurality of thermoelectric conversion elements 2 composed of the elements 2 b are arranged so as to be sandwiched between the wiring conductors 3 a and 3 b, and are joined by solder 6.

The thermoelectric conversion elements 2 are composed of two types of N-type thermoelectric conversion elements 2a and P-type thermoelectric conversion elements 2b, and are arranged in a matrix on one main surface of the lower support substrate 1a. N-type thermoelectric conversion element 2a and P-type thermoelectric conversion element 2b are connected by wiring conductors 3a and 3b so as to be alternately and electrically in series with N-type, P-type, N-type, and P-type, An electric circuit is formed. The thermoelectric conversion element 2 is preferably a Bi-Te system that has the most excellent thermoelectric conversion performance near room temperature. Thereby, a good cooling effect can be obtained. Bi _0.4 Sb _1.6 Te ₃ , Bi _0.5 Sb _1.5 Te _3, etc. as P type, Bi ₂ Te _2.85 Se _0.15 , Bi ₂ Te _2.9 Se _0.1 as N type Etc. are preferably used.

  The wiring conductors 3 a and 3 b are electrically connected to the external connection terminal 4. The external connection terminal 4 can be connected to the power supply wiring 5 by the solder 10 and has a structure in which power is supplied from the outside.

  In the prior art, the solder 10 is electrically connected by contacting the power supply wiring 5 to form an electric circuit.

  However, even if the electrical connection is made, the mechanical strength is weak, so there are cases where the power supply wiring 5 can be removed during mounting work on a package or the like, and stable mounting may not be possible. .

  Therefore, in the present invention, the diffusion layer 8 of the power supply wiring component having a thickness of 0.1 μm or more is formed on the solder 10 that joins the power supply wiring 5 to the external connection terminal 4, and the diffusion layer has a bonded area. It is important that it exists in 20% or more. As a result, an anchor effect is created between the solder 10 and the power supply wiring 5, and the mechanical strength can be improved. For this reason, the power supply wiring is not removed even in the mounting operation, and a thermoelectric conversion module capable of stable mounting operation is obtained. When the thickness of the diffusion layer 8 of the power supply wiring component is smaller than 0.1 μm or smaller than 20% of the bonded area, a sufficient anchor effect cannot be obtained and a stable bonding strength cannot be obtained. The thickness is preferably 0.3 μm or more, more preferably 0.5 μm.

  The bonded area is preferably 30% or more, more preferably 40% or more.

  In addition, it is important that the bonding strength of the power supply wiring 5 is 2N or more. As a result, the power supply wiring 5 is not removed during the mounting operation, and a stable mounting operation is possible. The bonding strength is preferably 5N or more, more preferably 10N or more.

  In the case of less than 2N, the power supply wiring may be disconnected during the mounting operation.

  In addition, it is desirable that the interface 9 between the diffusion layer 8 and the non-diffusion layer 7 of the power supply wiring component has a wave shape, and the interface 9 of the diffusion layer 8 cuts the joint and cross-sections the X-ray microanalysis. For example, the power supply wiring component can be analyzed and mapped.

  As a result, a stronger anchor effect can be expected, and thus the bonding strength is stabilized.

  Further, the diffusion layer 8 is a range in which the power supply wiring component is included at 1 at% or more.

  Further, it is desirable that the diffusion layer 8 is denser than the surrounding non-diffusion layer 7. This is similarly observed by SEM observing the entire section or the vicinity of the interface at a magnification of 100 to 3000 times and observing the proportion of voids. Therefore, when the diffusion layer 8 is denser, a high strength and stable bonding strength can be obtained.

  By making the power supply wiring 5 into a pillar or block shape, wire bonding is possible, thereby eliminating the need for manual mounting work and enabling more stable mounting work.

  Further, by bonding the power supply wiring 5 at a temperature of 103 to 130% of the melting temperature of the solder 10, the diffusion layer 8 of the power supply wiring component can be formed, and a stable bonding strength can be obtained. . When the solder 10 is melted and bonded at a temperature lower than 103% of the melting temperature, the sufficient diffusion layer 8 of the power supply wiring component is not formed, and a stable bonding strength cannot be obtained.

  Further, when melted and bonded at a temperature higher than 130%, the solder has low viscosity and fluidity is too high, so that the solder may flow out to the adjacent wiring conductor 3 and may be short-circuited. Accordingly, a temperature of 103 to 130% of the solder melting temperature, preferably 105 to 125%, more preferably 107 to 120% is desirable.

  Furthermore, it is preferable to adjust the temperature rising rate as necessary.

  Next, the manufacturing method of the thermoelectric module of the present invention will be described by taking the manufacturing method of the thermoelectric module 11 of FIG. 1 as an example.

  First, the thermoelectric conversion element 2 is prepared. According to the present invention, the thermoelectric conversion element 2 can be obtained by a known method. That is, it is possible to use crystals obtained by any one of a sintering method, a single crystal method, a melting method, and a thin film method.

  The thermoelectric conversion element 2 is preferably a sintered body containing at least one of Bi and Sb and at least one of Te and Se. These metals and alloys can realize a thermoelectric module with high performance near room temperature. Although the magnitude | size of the thermoelectric conversion element 2 is not specifically limited, As the small thermoelectric module 11, what processed into 0.1-2 mm in length, 0.1-2 mm in width, and 0.1-3 mm in height is prepared.

  Next, ceramics such as alumina, aluminum nitride, silicon nitride, silicon carbide, and diamond are prepared as the support substrate 1. After processing the substrate shape, the wiring conductor 3 and the external connection terminal 4 are formed on the surface using a conductive material such as Zn, Al, Au, Ag, W, Ti, Fe, Cu, Ni, Pt, Pd, and Mg. It is formed using a technique such as a plating method, a metallization method, a DBC (Direct-bonding Copper) method, a chip bonding method, or the like.

  Next, the thermoelectric conversion element 2 is disposed on the wiring conductor 3. In order to improve the wettability of the solder 6, the thermoelectric conversion element 2 is joined by the solder 6 via Ni or the like that is previously metallized on the joint surface.

  The thermoelectric conversion elements 2 are arranged so that N-type thermoelectric conversion elements 2a and P-type thermoelectric conversion elements 2b are alternately arranged, and are electrically arranged in series.

  The thermoelectric conversion module 11 is manufactured by locally heating and joining the power supply wiring 5 having a diameter of, for example, 0.3 mm to the external connection terminal 4 of the thermoelectric conversion module 11 obtained in this way with a soft beam or the like. To do. In addition, the thermoelectric conversion element 2 and the wiring conductor 3 can be joined simultaneously or separately with an electric furnace or a heater.

  In addition, a cylindrical or prismatic block can be used as the lead wire power supply wiring.

  Thus, since the thermoelectric conversion module 11 of the present invention does not allow the power supply wiring 5 to be removed when mounted on a package or the like, a thermoelectric module with excellent mounting workability can be provided.

As a starting material, a thermoelectric conversion element 2 made of a Bi ₂ Te _2.85 Se _0.15 sintered body was prepared. The shape was a quadrangular prism, and the dimensions were 0.6 mm in length, 0.6 mm in width, and 1 mm in height.

  In addition, as the support substrate 1, alumina having a size of 6 mm × 8 mm was prepared.

  A Cu wiring conductor 3 was formed on the support substrate 1 by metallization.

  A solder paste made of solder 6 such as Au-Sn is printed on the wiring conductor 3a of the lower support substrate 1a, the thermoelectric conversion elements 2 are arranged on the printed wiring paste 3a, and the thermoelectric conversion elements are heated from the opposite surface of the lower support substrate 1a. 2 was fixed. The number of thermoelectric conversion elements 2 is the same as that of N-type thermoelectric conversion elements 2a and P-type thermoelectric conversion elements 2b.

  Similarly, the thermoelectric module 11 is obtained by fixing the upper support substrate 1b and the thermoelectric conversion element 2 on the other surface.

  The power supply wiring 5 was connected to the external connection terminal 4 of the obtained thermoelectric conversion module 11 while heating with a soft beam while supplying the solder 10.

The power supply wiring 5 of the thermoelectric conversion module 11 obtained in this way was pulled in a direction to be bent at a right angle, and the peel strength was measured. In addition, the yield when mounted on a package was measured.

  As an example, the sample No. 2 to 7 and 9 to 20 were good because the peel strength was 2N or more and the mounting yield was 100%.

  On the other hand, as a comparative example, the sample No. Nos. 1 and 8 had a low peel strength and a defect occurred in the mounting test, which was clearly inferior to the sample of the present invention.

  In addition, the result of each sample is demonstrated separately below.

  In sample No. 7, the solder heating temperature was too high and the solder dripped to cause a short circuit.

  In Sample No. 16, since the interface shape of the diffusion layer is flat, the anchor effect does not work and the peel strength is slightly lowered, but there is no problem in use.

  Samples Nos. 21 and 22 satisfy the mounting yield without causing a short circuit with either solder or wire bonding.

  In sample Nos. 23 to 25, it can be seen that the peel strength is improved as the void ratio of the diffusion layer is reduced.

  Such control can be managed by the solder melting temperature, but can also be performed by managing the heating rate, the solder atmosphere, the heat sink, and the like as required.

BRIEF DESCRIPTION OF THE DRAWINGS It is a thermoelectric conversion module of one Embodiment of this invention, (a) is a perspective transmission figure, (b) is a cross-sectional enlarged view of a power supply wiring junction part. It is a thermoelectric conversion module of an embodiment applicable to wire bonding of the present invention, (a) is a perspective transparent view, and (b) is an enlarged sectional view of a power supply wiring junction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Support substrate 1a ... Lower support substrate 1b ... Upper support substrate 2 ... Thermoelectric conversion element 2a ... N type thermoelectric conversion element 2b ... P type thermoelectric conversion element 3 ... Wiring Conductor 3a ... Lower wiring conductor 3b ... Upper wiring conductor 4 ... External connection terminal 5 ... Power supply wiring 6 ... Solder 7 ... Non-diffusion layer 8 ... Diffusion layer 9 ...・ Interface 10 ... solder 11 ... thermoelectric conversion module

Claims (6)

A support substrate; a plurality of thermoelectric conversion elements arranged on the support substrate; a wiring conductor that electrically connects the thermoelectric conversion elements; an external connection terminal that is electrically connected to the wiring conductor; In a thermoelectric conversion module including a power supply wiring that is electrically connected to an external connection terminal and supplies power, a solder that joins the power supply wiring to the external connection terminal has a power supply wiring component having a thickness of 0.1 μm or more. A thermoelectric conversion module, wherein a diffusion layer is formed, and the diffusion layer is present in 20% or more of the bonded area of the power supply wiring. The thermoelectric conversion module according to claim 1, wherein a bonding strength of the power supply wiring is 2N or more. 3. The thermoelectric conversion module according to claim 1, wherein a part of a cross section of an interface between a diffusion layer and a non-diffusion layer of a component of the power supply wiring has a wave shape. 4. The thermoelectric conversion module according to any one of claims 1 to 3, wherein a diffusion layer of a component of the power supply wiring is denser than a surrounding non-diffusion layer. The thermoelectric conversion module according to claim 1, wherein the power supply wiring has a pillar shape or a block shape. A method for manufacturing a thermoelectric conversion module, comprising joining the power supply wiring of the thermoelectric conversion module according to claim 1 at a temperature of 103 to 130% of a solder melting temperature.

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