JP3556494B2 - Thermoelectric converter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermoelectric conversion device including an element made of P-type and N-type thermoelectric materials, and capable of performing temperature difference power generation (thermal power generation) by the Seebeck effect and electronic cooling and heat generation by the Peltier effect.
[0002]
[Prior art]
When a so-called π-type thermoelectric conversion element having a structure in which a thermoelectric element is sandwiched between two substrates is used as a power generation device, in order to efficiently inflow and outflow heat to the thermoelectric conversion element, these two sheets are used. Connecting the board with a heat-absorbing and radiating plate made of a material with high thermal conductivity such as metal (one of which functions as a heat-absorbing plate and the other functions as a heat radiating plate, of course, depending on the situation), At the same time, connection was made by means of a screw or the like via an elastic member such as a spring or rubber.
[0003]
In recent years, by using a small-sized thermoelectric conversion element as a power generation device, power generation is performed by a temperature difference between body temperature and outside air temperature, and a movement of driving a portable small electronic device such as a wristwatch has been widely seen. It has become to. The structure and manufacturing method of such a small thermoelectric conversion element are described and disclosed in JP-A-63-20880, JP-A-8-18109, and JP-A-8-97472.
[0004]
Further, the application of such a thermoelectric conversion element to a wristwatch or the like as a power generation device and the mounting structure thereof are described in JP-A-55-20483, JP-A-8-46249, JP-A-6-109868, and the like. Is described and disclosed.
[0005]
[Problems to be solved by the invention]
However, when the two substrates of the thermoelectric conversion element and the heat sink / radiator plate are firmly bonded or connected with an adhesive or a screw, etc., when a force is applied to the heat sink / radiator plate, particularly in the shear direction, the thermoelectric conversion element There was a problem that would be damaged.
On the other hand, when a thermoelectric conversion element is used as a thermoelectric generator in a wristwatch or the like and is mounted on an electronic device such as a wristwatch, particularly a portable electronic device, bismuth, which is generally said to have the highest thermoelectric conversion performance near room temperature, is used. -A tellurium-based material is used, which is a substance with very low mechanical strength. Therefore, a portable electronic device such as a wristwatch also requires a structural design that considers mechanical strength enough to withstand shocks such as vibration and dropping. In this case, when a heat absorbing / radiating plate is attached to the thermoelectric conversion element, not only a general thermoelectric conversion element but also an element constituting a thermoelectric conversion element disclosed in JP-A-63-20880, JP-A-8-18109, and the like. There is a problem that even the element reinforced by filling the gap with the resin may damage the thermoelectric conversion element.
[0006]
[Means for Solving the Problems]
In the thermoelectric conversion device of the present invention, the connection between the two substrates and the two heat absorbing and dissipating plates of the thermoelectric conversion element has fluidity and viscoelasticity, particularly usually a constant form, in at least one of the connections. This is achieved through a material having a thixotropic property, which means a property of being deformed by the addition of water. With this material, external shocks transmitted through the heat absorbing and dissipating plate can be absorbed, and destruction and damage of the thermoelectric conversion element can be prevented. In this case, it is necessary to select a material having a high thermal conductivity as the material having thixotropic properties. However, fats and oils such as so-called silicone compounds made by mixing fine particles such as alumina with silicone oil, etc. And fine particles of a highly heat-conductive substance dispersed therein and clay.
[0007]
Further, in the thermoelectric conversion device of the present invention, as described above, the two heat absorbing and radiating plates connected to the substrate of the thermoelectric conversion element are made of a structure made of a material having a low thermal conductivity such as resin, glass, ceramics, and metal. Strongly connected. Accordingly, even when an external force is applied to the heat absorbing and dissipating plate, the configuration as a thermoelectric conversion device can be maintained, and at the same time, the connection between the thermoelectric conversion element and the heat absorbing and dissipating plate is deformed by the external force as described above. The thermoelectric conversion element is not damaged because of the connection material having the property.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic sectional view of a thermoelectric converter according to the present invention. As shown in FIG. 1, the thermoelectric element 1009 includes a P-type thermoelectric element 1004 and an N-type thermoelectric element 1005 sandwiched between a first substrate 1002 and a second substrate 1003, and at the same time via a first electrode 1006 and a second electrode 1007. And the resin 1008 is filled in the gaps between the elements. The thermoelectric element is constituted by the thermoelectric element 1009, the first heat absorbing and dissipating plate 1010, the second heat absorbing and dissipating plate 1011, and the plastic heat insulating structure 1012 for connecting these heat absorbing and dissipating plates to each other. Here, the first substrate 1002 and the first heat absorbing and dissipating plate 1010 are firmly connected by an adhesive layer 1013, and the second substrate 1003 and the second heat absorbing and dissipating plate 1011 are thermally connected by a heat conductive silicone compound 1014 having thixotropic properties. It is designed to keep contact. The thermoelectric conversion device 1001 is electrically connected to the outside by a lead wire 1016 connected to an input / output electrode 1015 provided on the first substrate 1002 of the thermoelectric conversion element 1009 filled with resin. It has become.
[0009]
Next, a method for manufacturing the thermoelectric conversion device 1001 of this embodiment will be described.
FIG. 2 schematically shows a manufacturing process of a portion of the thermoelectric conversion element 1009 filled with the resin except for the resin 1008. First, as shown in FIG. 2A, a P-type thermoelectric material plate 2001 polished to a certain thickness is prepared. Next, as shown in FIG. 2B, a photoresist is applied to both surfaces of the P-type thermoelectric material plate 2001, and is exposed and developed to form a resist layer 2002 having a desired pattern. Next, as shown in FIG. 2C, a nickel layer 2003 is formed by a wet method. Further, as shown in FIG. 2D, a solder layer 2004 is formed thereon. FIG. 2E shows a state where the resist layer 2002 is peeled and removed. Next, as shown in FIG. 2F, a solder bump 2005 is formed by a reflow process (melting process) for the purpose of equalizing the composition of the solder layer 2004 and adjusting the height by making the solder layer spherical. I do. Here, the above-described nickel layer 2003 is referred to as a nickel bump 2006 because of its shape. Through a series of these processes, a P-type thermoelectric material plate 2007 having a solder bump structure was obtained.
[0010]
Next, a silicon wafer 2008 shown in FIG. This silicon wafer is insulated by thermally oxidizing the surface. Next, as shown in FIG. 2H, a metal layer 2009 made of chromium, nickel, and gold is formed on the silicon wafer 2008 by a sputtering method. By forming the metal layer 2009 into an electrode 2010 having a desired pattern by a photolithography method, a first substrate 2011 is formed (FIG. 2I). The electrode 2001 serves as an electrode for performing a PN junction and an electrode for performing input and output to and from the outside.
[0011]
Next, as shown in FIG. 2J, the P-type thermoelectric material plate 2007 having the bump structures on both surfaces manufactured in this way and the first substrate 2011 are connected by soldering by melting the solder bumps 2005. At this time, a gap is provided between the P-type thermoelectric material plate 2001 and the first substrate 2011 by the nickel bump 2006. Next, the joined body of the P-type thermoelectric material plate and the first substrate 2011 formed as described above is connected to a cutting tool as needed by using the P-type thermoelectric material between the solder bumps formed on the P-type thermoelectric material. Unnecessary parts are removed by cutting with a cutting device such as a dicing machine or a wire saw provided. At this time, the cutting device is operated so that the cutting edge of the cutting tool is accommodated in the gap formed by the nickel bump so as not to damage the electrode 2010 on the first substrate 2011 or the first substrate itself. Thus, a P-type thermoelectric element bonded substrate 2013A in which the P-type thermoelectric element 2012 is bonded to the first substrate 2011 was manufactured (FIG. 2 (k)).
[0012]
Next, similarly for the N-type thermoelectric material, an N-type thermoelectric element bonding substrate 2013B having a desired element arrangement is prepared in advance, and these are opposed to each other, aligned, and then pressurized and heated. Was bonded to the electrodes on the substrate via solder bumps, thereby producing a thermoelectric conversion element 2014.
[0013]
Specifically, a compound composed of bismuth, antimony, and tellurium was used for the P-type thermoelectric material plate, and a compound composed of bismuth and tellurium was used for the N-type thermoelectric material plate. The thickness was set to 600 μm. The nickel bumps were cylindrical with a diameter of 80 μm and a height of 20 μm, and the solder bumps were nearly spherical with a diameter of about 80 μm. The distance between the bump centers was 220 μm, and the width of the cutting blade was 140 μm. As a result, the size of the element was 80 μm square and the height was 600 μm. Also, as for the number of elements, 102 P-type and N-type elements were connected in series.
[0014]
The thermoelectric conversion element 2014 was filled with the resin 1008 by pouring a resin having fluidity into the thermoelectric conversion element 2014 and curing the resin. Specifically, an epoxy resin was used as the resin.
After bonding the ten thermoelectric conversion elements 1009 on a first heat absorbing and dissipating plate 1010 made of nickel plated brass with an epoxy adhesive, each was connected in series with a gold wire by wire bonding, and A lead wire 1016 was attached to the output electrode 1015. That is, a device in which 102 × 10 = 1020 thermoelectric elements were connected in series was produced. Next, a heat insulating structure 1012 made of plastic was connected to the first heat sink / radiator plate 1010 using an epoxy adhesive. After an appropriate amount of silicon compound 1014 is placed on all of the second substrates 1003 of the ten thermoelectric conversion elements 1009 so that thermal contact between the second substrate 1003 and the second heat sink / radiator plate 1011 is sufficient, nickel plating is applied to brass. A second heat absorbing and radiating plate 1011 made of a material subjected to the above process is placed on these, and the thermoelectric conversion device 1001 of the present invention is fabricated by adhering and fixing the plastic heat insulating structure 1012 with an adhesive.
[0015]
When the performance of the thermoelectric conversion device 1001 manufactured in this manner was examined, the electrical resistance was 1000Ω, and when a temperature difference was given between the first heat absorbing and radiating plate 1010 and the second heat absorbing and radiating plate 1011, 150 mV / ° C. Open-circuit voltage was obtained.
Next, the thermoelectric conversion device 1001 was incorporated into a wristwatch and its performance was examined.
FIG. 3 is a view showing a cross section of a thermoelectric conversion device 1001 of the present invention incorporated in a wristwatch. In the thermoelectric conversion device 1001, the second heat absorbing and radiating plate is connected to a metal case 3001 via a metal heat conductive plate 3002 having elasticity. The other first heat absorbing and radiating plate is connected to the back cover 3003 by a rubber 3004 having high thermal conductivity while maintaining thermal contact. On the other hand, a plastic heat insulating frame 3005 is provided between the case 3001 and the back cover 3003, and heat insulation between the case and the back cover is achieved by the heat insulating frame. With such a structure, the heat generated from the arm efficiently passes through the back cover 3003 and the thermoelectric conversion device 1001 and radiates heat from the case 3001 and the glass 3006 to the outside. As a result, power is generated by the heat passing through the thermoelectric converter 1001, and if the generated power is 0.2 V or more, the generated power is stabilized at 1.5 V by a step-up / rectifier device contained in the clock move 3007. It is designed to drive a watch.
[0016]
When this watch was carried, power generation characteristics from the thermoelectric converter 1001 as shown in FIG. 4 were obtained. Curve A is a power generation characteristic when the outside air temperature is 18 ° C., and the peak voltage reaches 1.2 V about 15 seconds after immediately after carrying, and shows 0.4 V even in a steady state. Curve B is data at an outside air temperature of 22 ° C, and curve C is at 28 ° C. In each case, it exceeded 0.2 V and was shown to have sufficient output to drive the watch.
[0017]
Further, a drop test was performed on the impact resistance of the timepiece as in Example 1. The drop test was carried out by dropping onto the concrete from a height of 1 m with the back cover surface, the glass surface, the 12 o'clock direction, the 3 o'clock direction, the 6 o'clock direction, and the 9 o'clock direction as the drop directions. In the test of the above, there was no damage to the thermoelectric converter. As described above, according to the thermoelectric conversion device of the present invention, the thermoelectric conversion device is excellent in impact resistance and acts as a sufficient thermoelectric device.
[0018]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the thermoelectric conversion device of this invention, what is excellent not only in impact resistance but also in environmental resistance at high temperature, high humidity, etc. can be provided. In addition, it can be used as an energy source of a small portable device such as a wristwatch, and at the same time, can be used as a Peltier device having high reliability, that is, a cooling device.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a thermoelectric conversion device according to the present invention.
FIG. 2 is a view schematically showing a manufacturing process of a thermoelectric conversion element according to the present invention.
FIG. 3 is a diagram showing a cross section of a main part of a wristwatch when the thermoelectric conversion device according to the present invention is incorporated in a wristwatch.
FIG. 4 is a table showing the power generation performance of the thermoelectric converter of the present invention incorporated in a wristwatch.
[Explanation of symbols]
1001 Thermoelectric conversion device 1002 First substrate 1003 Second substrate 1004 P-type thermoelectric element 1005 N-type thermoelectric element 1006 First electrode 1007 Second electrode 1008 Resin 1010 First heat absorbing / radiating plate 1011 Second heat absorbing / radiating plate 1012 Heat insulating structure 1013 Adhesion Agent layer 1014 silicone compound

Claims (5)

A plurality of P-type elements made of P-type thermoelectric material;
A plurality of N-type elements made of N-type thermoelectric material;
With each having an electrode to form a PN junction pair by joining the P-type and N-type elements in pairs consist of a first substrate and a second substrate that sandwich the P-type and N-type elements facing each other In the thermoelectric converter,
A first heat sink / radiator plate connected to the first substrate by an adhesive ;
A second heat sink / radiator plate connected to the second substrate by a high heat conductive material having chicken sotropic properties ;
A thermoelectric conversion device, comprising: a reinforcing member made of a low heat conductive material that connects the first heat absorbing and radiating plate and the second heat absorbing and radiating plate. The thermoelectric conversion device according to claim 1 , wherein the high heat conductive substance is formed by dispersing a high heat conductive substance in fats and oils . 2. The thermoelectric conversion device according to claim 1, wherein the high thermal conductive material is obtained by dispersing fine particles of alumina in a silicone compound. The thermoelectric conversion device according to claim 1, wherein a resin material is filled between the first substrate and the second substrate. A small electronic device using the thermoelectric conversion device according to any one of claims 1 to 4 as a power generation device.

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