KR20040021720A - Thermoelectric module - Google Patents

Abstract

PURPOSE: A thermoelectric device is provided to improve the intensity and the durability by inserting a mixture of Mo and Sn into a gap between an N-type thermoelectric semiconductor and a P-type thermoelectric semiconductor. CONSTITUTION: A thermoelectric device includes the first ceramic substrate, one or more N-type thermoelectric semiconductors(N), one or more P-type thermoelectric semiconductors(P), and the second ceramic substrate. The N-type thermoelectric semiconductors(N) and the P-type thermoelectric semiconductors(P) are fixed in a predetermined interval on the first ceramic substrate. The N-type thermoelectric semiconductors(N) and the P-type thermoelectric semiconductors(P) are connected to each other by using conductors. The second ceramic substrate is covered thereon. A metallic filling member is inserted into a gap between the N-type thermoelectric semiconductors(N) and the P-type thermoelectric semiconductors(P). The metallic filling member is formed with Sn or a mixture(50) of Sn and Mo.

Description

Thermoelectric module

The present invention relates to a thermoelectric element.

As is well known, the thermoelectric element is not only utilized as a cooling means by replacing a freon gas, which is one of the substances causing air pollution, and is also widely used as a small generator by the Seebeck effect.

In particular, when a current flows in a loop formed by metals being grounded through a semiconductor (thermoelectric semiconductor), a potential difference is generated due to a difference in Fermi energy, and electrons carry energy necessary to move from one metal surface to another (heat absorption) While cooling takes place, heating occurs because other metals give out heat energy as much as the energy brought by the electrons (radiation), which is called the Peltier effect and is the operating principle of the cooling device by the thermoelectric element.

At this time, the location of the endotherm and the heat dissipation is determined according to the type of the semiconductor and the direction in which the current flows, and a difference occurs in the effect depending on the material.

1 is a structural diagram of an NP-type thermoelectric semiconductor provided in a thermoelectric element. Referring to the description of the operating state, a circuit in which an N-type thermoelectric semiconductor (N) and a P-type thermoelectric semiconductor (P) are connected in series via a conductor (M) is shown. When a direct current (DC) is applied to the metal, the negatively charged metal / semiconductor contacts (1, 2) move electrons absorbing thermal energy from the surroundings into the thermoelectric semiconductor, causing endotherm, and positively charged At the contacts, heat radiation 3 and 4 occurs due to the release of electron thermal energy. In addition, if the direction of the current is reversed, the endothermic and heat dissipating portions are also reversed.

On the other hand, there is a difference in the thermoelectric efficiency also depending on the material of the thermoelectric semiconductor (N, P), the thermoelectric materials are widely used because of the excellent number of thermal cells, BiTe-based, PbTe-based and the like.

However, even when optimized using the thermoelectric material, the heat absorption and / or heat dissipation per power supply of the thermocouple in which the N-type and P-type thermocouples are paired is very small. For this reason, when the thermoelectric semiconductors (N, P) are actually utilized in a cooling device, a plurality of thermocouples are connected to increase the amount of heat absorption and / or heat dissipation, and these devices are widely used in cooling devices and the like as thermoelectric devices.

Unexplained symbols 'E.F' and 'H.F' indicate directions of electron flow and hole flow occurring in N-type and P-type thermoelectric semiconductors, respectively.

FIG. 2 is a partial cutaway perspective view of a conventional thermoelectric device, and FIG. 3 is a partial cross-sectional view of FIG. 2. Referring to this, a plurality of thermocouples are disposed on a plate to connect a conductor to form a series circuit, and then a DC current ( 41, 42) forms a structure in which heat dissipation and heat absorption oppose the thermocouples.

In general, the conductor is made of a material having high conductivity such as copper 30 to smoothly flow the current, and grounds the copper 30 and the thermal conductors (N, P) through the lead 20. do. In addition, a reinforcement is applied to the upper and lower surfaces of the structure so as to prevent the damage caused by external forces while preserving the shape of the structure consisting of the thermoelectric semiconductors (N, P), often an insulating material such as ceramic (10) widely used In this case, the copper 30 is bonded to the ceramic substrate 10 through the lead 20.

In addition, since addition and application of layers made of various materials are performed as a method for realizing the diffusion prevention of the lead 20, improvement of adhesion between the thermoelectric semiconductors (N, P) and the conductor, or improvement of the thermoelectric effect, The general layer structure (ceramic substrate-lead-copper-lead-thermoelectric semiconductor-lead-copper-lead-ceramic substrate) of the thermoelectric element described in the related art is just one example, and the present invention is not limited thereto.

However, in the conventional thermoelectric device, as shown in FIG. 3, the thermoelectric semiconductors N and P are disposed to be spaced apart at predetermined intervals to prevent short circuits, and the copper 30 and the thermoelectric semiconductors are formed through the lead 20. N, P) is fixed and grounded, and the ceramic substrate 10 coated on the upper and lower surfaces only maintains the shape of the element and protects against external forces, so that even a small impact can be easily broken or the ground state changes, causing malfunction. Could. In addition, the conventional thermoelectric device has a problem in that its life is shortened due to the decrease in durability due to the mechanical variation between the thermoelectric semiconductor and the conductor and the change in the physical properties of the component as the change from the maximum temperature to the lowest temperature occurs repeatedly.

Therefore, the problem can be solved to some extent by filling the separation space with a liquid filling member and hardening it, but the following conditions must be satisfied.

First, in the thermoelectric device, since the N-type thermoelectric semiconductor (N) and the P-type thermoelectric semiconductor (P) are connected in series, the filling member should be an insulator to prevent a short circuit.

Second, the thermal conductivity between the heat absorbing portion and the heat dissipating portion of the thermoelectric element should be low. If the heat conductivity between the heat absorbing portion and the heat dissipating portion is excellent, the heat of the heat dissipating portion can be easily transferred to the heat absorbing portion, so that the temperature of the heat absorbing portion to be low temperature can be increased.

Third, since a large temperature change continuously occurs in the heat absorbing part and the heat dissipating part, the filling member should have a small change in physical properties even at an extremely high or low temperature.

However, the metals used as the conventional filling members did not sufficiently satisfy the first and second conditions, and polymer composite materials such as epoxy did not satisfy the third condition, causing the operating efficiency of the thermoelectric element to be deteriorated. The materials used were expensive and disadvantageous in terms of economics.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a thermoelectric device with improved strength as well as durability against external force while maintaining thermoelectric efficiency.

1 is a structural diagram of an N.P type thermoelectric semiconductor provided in a thermoelectric element;

2 is a partial cutaway perspective view of a conventional thermoelectric device;

3 is a partial cross-sectional view of FIG.

4 is a partial cross-sectional view showing a thermoelectric device according to the present invention;

4A is an enlarged view of a portion X in FIG. 4.

-Explanation of terms for main parts of attached drawings-

10; Ceramic substrate 20; lead

30; Copper 41; Positive (+)

42; Cathode (-) 50; mixture

51; Note 52; molybdenum

60; air gap

N; N-type thermoelectric semiconductor P; P type thermoelectric semiconductor

D.C; DC current

The present invention for achieving the above object,

One or more N-type thermocouples and P-type thermocouples are fixed to one surface of the first ceramic substrate at predetermined intervals, and the thermocouples of the release type are sequentially connected in series via a conductor, and the second ceramic substrate is connected to the second ceramic substrate. 1 A thermoelectric element bonded and covered with a ceramic substrate opposite thereto,

Powder-filled metallic filling member is embedded in the spaced space of the thermoelectric semiconductors,

In particular, the powder-type metallic filling member is characterized in that the tin,

Alternatively, the powder-type metallic filling member is characterized in that the mixture of tin and molybdenum.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

4 is a partial cross-sectional view showing a thermoelectric device according to the present invention. When described with reference to this, at least one N-type thermoelectric semiconductor (N) and a P-type thermoelectric semiconductor (P) are in series with each other via a conductor (copper) 30. Tin 51 is filled into the spaced space between the N-type thermoconductor N and the P-type thermoconductor P, which are connected to and fixed to a conventional thermoelectric element at a predetermined interval, in which a direct current (DC) is operated as a flow. do.

Here, for the sake of clarity, the thermoelectric device according to the present invention will be described together with the manufacturing process.

In general, the manufacturing process of thermoelectric elements is in order of top and bottom plate manufacturing (ceramic supply, lead coating, copper coating, lead coating), N-P type thermoelectric semiconductor (N, P) mounting, wire work, and top and bottom plate joining. Is done.

The ceramic supply operation is a step of forming a substrate on which the conductors such as lead 20 and copper 30 are applied while protecting the N-P type thermoelectric semiconductors (N, P), and the substrate is generated according to the Peltier effect. The effect of heat dissipation and heat absorption is transmitted to the outside.

In general, it is preferable that the substrate is a non-conductor and has a large heat capacity, in order to prevent the temperature from being easily changed by heat conversion (endotherm, heat dissipation) generated by the Peltier effect. Ceramic is mainly utilized. Here, the substrate is mixed with a heat sink, a heat absorbing plate, or a ceramic substrate (a first ceramic substrate, a second ceramic substrate), or the like.

In the case of copper coating, which is part of the upper and lower plate manufacturing process, detailed work is required. This is because the copper 30 is a medium for grounding one or more N-type thermoelectric semiconductors (N) and P-type thermoelectric semiconductors (P) in series with each other. (If the connection is not properly made, the thermoelectric element cannot be operated or malfunctions. In particular, in the case of a thermoelectric device used in a cooling system, in particular, a plurality of thermocouples composed of an N-type thermocouple (N) and a P-type thermocouple (P) are connected in series via a conductor. The connection is very complicated. Therefore, before applying the copper 30, the circuit diagram, that is, the design for the application position must be preceded.

On the other hand, in the case of lead coating is to increase the adhesive strength between the copper 30 and the ceramic substrate 10, copper 30 and the thermoelectric semiconductor (N, P) can be referred to as a kind of soldering operation. The position where lead 20 is applied to prevent short circuit should coincide with the application position of copper 30, which is a process requiring detailed work like the copper coating.

When the upper and lower plates are manufactured as described above, the N-type thermoconductor N and the P-type thermoconductor P are mounted on the upper or lower plate, respectively. As mentioned above, the thermoelectric element is a kind of direct element in which one or more of the thermocouples are connected in series with each other, and thus the N-type thermoelectric semiconductor (N) and the P-type thermoelectric semiconductor (P) must be accurately mounted in place. By design applied in lead coating.

Thereafter, the wires 41 and 42 (see FIG. 2), which supply the DC current D.C, are connected. Since the wires 41 and 42 are joint members and power supply paths between the external substrate and the thermoelectric element, the corresponding positions according to the design of the copper 30, the lead 20, and the thermoelectric semiconductors (N, P) mentioned above. It is grounded and fixed to.

After the above process, the filling member is filled into the spaced space of the thermoelectric semiconductor (N, P).

In the present invention, the filling member processed in the form of powder is embedded, in particular, it is preferred that the change in physical properties with a small change in temperature, it will be described with reference to Figure 4a.

The filling member in the form of powder lowers the thermal conductivity between the heat absorbing portion and the heat dissipating portion while a predetermined void 60 is formed. In addition, it is possible to significantly reduce the electrical conductivity to expect a relatively excellent insulation effect than the prior art it is possible to suppress the degradation of the thermoelectric efficiency as much as possible.

On the other hand, the filling member is advantageous in that the thermal conductivity and the electrical conductivity is small while the change in physical properties is small even under a sudden temperature change, in the present invention, the tin (51), the electrical conductivity and thermal conductivity is relatively small compared to other metals are utilized. Since the tin 51 is inexpensive and has a desirable property as a filling member of the thermoelectric element, when the tin 51 in the form of powder is filled into the separation space, a smaller electric conductivity and a thermal conductivity can be expected. Can be prevented from deteriorating.

However, tin (51) at room temperature is a beta-tin, which can ideally function as a protective agent of the N-type thermoelectric semiconductor (N) and the P-type thermoelectric semiconductor (P), that is, the function of the filling member. When the temperature drops, the properties of alpha-tin can change, preventing them from functioning. Therefore, it is preferable to mix and use a predetermined amount of molybdenum 52 in powder form.

Molybdenum 52 has a relatively low thermal conductivity and electrical conductivity at very low temperatures (about minus 273 degrees Celsius) and very high temperatures (about 2000 degrees Celsius), so that thermal conductivity and electrical conductivity are relatively low. Tin 51, which is a member, helps the embedded thermoelectric element to reach its function and lifespan.

In the present invention, the mixing ratio of the tin 51 and the molybdenum 52 is set to 7: 3, and the increase and decrease of the tin 51 and the molybdenum 52 is not limited thereto.

On the other hand, when the tin 51 and molybdenum 52 mixture 50 in the powder form into the separation space, since the fluidity of the particles are lowered to support each other, the strength and durability of the thermoelectric element against external force is improved.

As described above, after the filling operation in which the tin 51 and molybdenum 52 mixtures 50 in powder form are introduced into the space between the thermoelectric semiconductors (N.P), the other one of the previous ones prepared (upper or lower) The cover is precisely covered and bonded to the plate on which the thermoelectric semiconductors (N, P) are mounted via an epoxy. On the other hand, the epoxy operation is a process to seal the thermoelectric element to block the physical and chemical effects from the outside and to have an appearance.

The thermoelectric element manufactured by filling the filling member in the form of powder through the above manufacturing process greatly improves the strength and durability against external impact. The cycle is performed by changing the heat absorbing part and the heat radiating part from the maximum temperature to the lowest temperature by applying the highest voltage. In the repeated experiments, the thermoelectric element without the filling member was short-circuited at 3000 to 5000 times. However, when the mixture of tin and molybdenum in the form of powder was inserted, the durability data was improved through the experimental data that more than 60,000 times were possible. At this time, the change in thermoelectric efficiency was insignificant.

According to the present invention as described above, by filling the molybdenum and tin mixture in the powder form in the space between the N-type and P-type thermoconductor, while improving the strength to the external force at a low cost, as well as operating the thermoelectric element There is an effect of increasing the durability due to the reduction of the physical properties and mechanical variations of the resulting component.

Claims (3)

One or more N-type thermocouples and P-type thermocouples are fixed to one surface of the first ceramic substrate at predetermined intervals, and the thermocouples of the release type are sequentially connected in series via a conductor, and the second ceramic substrate is connected to the second ceramic substrate. 1 A thermoelectric element bonded and covered with a ceramic substrate so as to face each other, The thermoelectric device, characterized in that the metallic filling member in the form of powder is embedded in the spaced space of the thermoelectric semiconductors. The method of claim 1, And the powder-filled metallic filling member is tin. The method of claim 1, The powder-type metallic filling member is a thermoelectric element, characterized in that the mixture of tin and molybdenum.