JP3549426B2 - Thermoelectric element and method for manufacturing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention includes a P-type element and an N-type element made of P-type and N-type thermoelectric semiconductor materials, and a thermoelectric element that enables temperature difference power generation (thermal power generation) by the Seebeck effect and electronic cooling and heat generation by the Peltier effect, and It relates to the manufacturing method.
[0002]
[Prior art]
The thermoelectric element is manufactured by joining a P-type thermoelectric semiconductor material and an N-type thermoelectric semiconductor material via a metal electrode to form a PN junction pair. This thermoelectric element generates electric power based on the Seebeck effect by giving a temperature difference between the junction pair, and as a power generation device, and when current flows through the element, cooling occurs at one of the junctions and heat is generated at the other. In other words, there is a use as a cooling device utilizing the Peltier effect or a precision temperature control device.
[0003]
This thermoelectric element is generally manufactured and used as a thermo module in which a plurality of tens to hundreds of PN junction pairs are formed in series in order to enhance the performance as an element.
The thermoelectric element as the thermo module maintains a shape as a structural body, and has two substrates having metal electrodes for forming a PN junction pair, and a plurality of P-type and N-type sandwiched therebetween. It is composed of a thermoelectric semiconductor material and a bonding material for bonding the P-type and N-type elements to the metal electrodes.
[0004]
In this thermoelectric element, for example, P-type and N-type thermoelectric semiconductor material pieces (hereinafter, referred to as elements) cut in advance to a predetermined shape and size are respectively arranged at predetermined positions with a jig or the like. It can be manufactured by joining the arranged elements to the metal electrode with a joining material such as solder and sandwiching the two elements with two substrates. Here, solder or the like used as a bonding material is formed on a metal electrode on the substrate in advance by a method such as printing or plating.
[0005]
In addition to this manufacturing method, for example, as disclosed in Japanese Patent Application Laid-Open No. H8-97472, a wafer-like (plate-like or rod-like) P-type and N-type thermoelectric semiconductor material may A step of forming solder bumps, a step of forming electrode wiring (metal electrodes) and a structure (structure) on a substrate, a step of bonding a thermoelectric semiconductor material on which solder bumps are formed to a substrate, and a step of forming a thermoelectric semiconductor bonded to the substrate There is also a method of manufacturing through a step of forming a thermoelectric semiconductor material chip (element) by cutting unnecessary portions of a semiconductor material, and a step of bonding substrates on which P-type and N-type thermoelectric semiconductor material chips are respectively formed.
[0006]
In this method, the metal electrode and the thermoelectric semiconductor material chip are joined with a structure interposed therebetween in order to improve the joining strength.
[0007]
[Problems to be solved by the invention]
However, in the above manufacturing method, when filling an encapsulant such as a resin between the elements of the thermoelectric element, if the amount of the resin used as the encapsulant exceeds an appropriate amount, the resin jumps out between the elements, and the metal electrode In some cases, resulting in poor insulation of the electrodes.
[0008]
On the other hand, if the amount of the resin used for filling is too small, the filling rate of the resin between the elements may be reduced, which may cause problems such as a decrease in the mechanical strength of the thermoelectric element. And, as described above, various defects caused by the amount of the encapsulating material have reduced the yield of thermoelectric element fabrication.
The present invention has been made to solve the above problems, and has an object to provide a thermoelectric element having high mechanical strength of a thermoelectric element and capable of improving the yield, and a method of manufacturing the same. I do.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention is to join a P-type element made of a P-type thermoelectric semiconductor material, an N-type element made of an N-type thermoelectric semiconductor material, and a pair of these P-type and N-type heterogeneous elements. A pair of substrates having a metal electrode capable of forming a PN junction pair with each other and facing each other with the P-type and N-type elements interposed therebetween; and a junction for bonding the P-type and N-type elements to the metal electrode. In the thermoelectric element provided with the material, a structure having a predetermined height is formed on one edge of a bonding surface of the metal electrode with the P-type and N-type elements.
[0010]
According to such a configuration, a structure having a predetermined height is formed at one edge of the bonding surface on the metal electrode or the substrate with the P-type and N-type elements. The body makes it possible to control the flow of the encapsulant for filling between the elements and to reduce the defects caused by the amount of encapsulant.
[0011]
That is, for example, even if the amount of the encapsulant exceeds an appropriate amount, since the encapsulant overflowing from between the elements does not flow out in the direction of the metal electrode because the structure is provided, the metal electrode is encapsulated. It can be prevented from being covered with the material, and the occurrence of insulation failure can be reduced.
In addition, when the amount of the encapsulant is small, the mechanical strength of the thermoelectric element becomes small. Therefore, by setting the amount of the encapsulant slightly larger than an appropriate amount, the thermoelectric element generated due to the insufficient amount of the encapsulant is generated. It is possible to reduce poor mechanical strength of the element and supply an element having high mechanical strength.
[0012]
Further, since the mechanical strength is increased, it is possible to supply a fine thermoelectric element having a small element.
Specifically, examples of the P-type and N-type thermoelectric semiconductor materials include Bi-Te-based materials, Fe-Si-based materials, Si-Ge-based materials, and Co-Sb-based materials.
Further, the structure can be formed of a thick-film photoresist by, for example, a photolithography method.
[0013]
Further, the manufacturing method is such that a structure is formed on one end side of the metal electrode or the substrate, and the P-type and N-type elements are joined to one of the two substrates. Face-to-face, the tips of the P-type and N-type elements and the metal electrode of the substrate facing the tips are fixed, and these substrates are joined.
According to such a manufacturing method, a structure is formed on one end side of the metal electrode or the substrate, and the P-type and N-type elements are joined to one of the two substrates. The substrates are faced to each other, and the tips of the P-type and N-type elements are fixed to the metal electrodes of the substrate facing the tips, so that these substrates are joined together, and then sealed between the elements of the thermoelectric element. To fill the material, the flow of the encapsulant can be controlled by the structure.
[0014]
That is, for example, even if the amount of the encapsulant exceeds an appropriate amount, since the encapsulant overflowing from between the elements does not flow out in the direction of the metal electrode because the structure is provided, the metal electrode is encapsulated. It can be prevented from being covered with the material, and the occurrence of insulation failure can be reduced.
In addition, when the amount of the encapsulant is small, the mechanical strength of the thermoelectric element becomes small. Therefore, by setting the amount of the encapsulant slightly larger than an appropriate amount, the thermoelectric element generated due to the insufficient amount of the encapsulant is generated. It is possible to reduce poor mechanical strength of the element and supply an element having high mechanical strength.
[0015]
Therefore, by using a structure capable of controlling the flow direction of the sealing material flowing out between the P-type and N-type elements, it is possible to reduce defects such as insulation failure and mechanical strength failure and improve the yield in thermoelectric element production. It becomes possible.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a perspective view showing an outline of a thermoelectric element according to the present invention, and FIG. 2 is a plan view showing a structure pattern formed on a substrate.
[0017]
As shown in FIG. 1, a thermoelectric element 1 according to this embodiment includes a P-type element 3 made of a P-type thermoelectric semiconductor material, an N-type element 4 made of an N-type thermoelectric semiconductor material, and a P-type and an N-type. It is composed of substrates 2A, 2B and the like having metal electrodes 5 capable of forming a PN junction pair by joining different types of elements 3, 4 one by one.
The P-type element 3 and the N-type element 4 are made of, for example, a sintered body of a Bi-Te-based material.
[0018]
The bottom surface of the P-type element 3 is joined to the metal electrode 5 of the substrate 2B via the structure 7. The hollow portion 7a of the structure 7 is filled with a bonding material 6 made of Ni and solder, so that the element 3 and the metal electrode 5 are electrically connected. . On the other hand, the upper surface of the element 3 is directly fixed to the metal electrode 5 of the substrate 2A by the bonding material 6. Similarly, the bottom surface of the N-type element 4 is joined to the metal electrode 5 of the substrate 2A via the structure 7, and the top surface is directly fixed to the metal electrode 5 of the substrate 2B by the joining material 6.
[0019]
As described above, the P-type element 3 and the N-type element 4 are sandwiched between the two substrates 2A and 2B, and one end is joined to the metal electrode 5 of the substrate 2A and the other end is joined to the metal electrode 5 of the substrate 2B. In this state, a PN junction pair is formed via the metal electrode 5, and the PN junction pairs are connected in series.
As shown in FIG. 2, on the substrates 2A and 2B, an oval metal electrode 5 capable of joining a pair of different types of P-type and N-type elements 3 and 4 is provided, and one end on the metal electrode 5 is provided. On the side, for example, a structural body 7 formed of a resin material in a substantially cylindrical shape and having a hollow portion 7a on the inner peripheral side is provided.
[0020]
These structures 7 are interposed between the bottom surfaces of the elements 3 and 4 and the metal electrode 5 to control the flow of the bonding material 6 generated at the time of bonding to increase the bonding strength between them. Provided on the metal electrode 5 of the substrate 2B at the edge of the bonding surface with the bottom surface of the P-type element 3 and on the metal electrode 5 of the substrate 2A at the edge of the bonding surface with the bottom surface of the N-type element 4. Have been.
[0021]
Further, each structure 7 is connected to the adjacent structure via a connection wall 7c, whereby the strength of each structure 7 is enhanced.
The control wall 7d of the structure 7 is formed on the metal electrode and the substrate. When the sealing material is filled between the elements, the electrodes are prevented from being covered with the sealing material. Therefore, for example, even if the amount of the encapsulant exceeds an appropriate amount, even if the encapsulant overflowing from the element flows out in the electrode direction, the electrode is covered by the encapsulant because it is controlled by the structure 7. It can be eliminated and insulation failure can be prevented. In addition, even if the amount of the encapsulant is large, the above-mentioned problems are unlikely to occur.Therefore, by setting the amount of the encapsulant slightly larger than an appropriate amount, the amount of the encapsulant is insufficient. It is possible to reduce the mechanical strength failure due to the existence.
[0022]
Next, an example of a method of manufacturing the thermoelectric element 1 configured as described above will be described step by step with reference to FIGS.
3 to 14 are schematic cross-sectional views showing respective manufacturing steps of the thermoelectric element 1. FIG. 3 shows an insulating film forming step, FIG. 4 shows a film forming step, FIG. 5 shows an electrode forming step, and FIG. 7, FIG. 7 shows a mask forming step, FIG. 8 shows a Ni and solder plating step, FIG. 9 shows a mask removing step, FIG. 10 shows a bump forming step, FIG. 11 shows a joining step, and FIG. 12 shows a cutting / removing step (pillaring step). 13 shows an assembling process, and FIG. 14 shows a filling process of an encapsulating material.
[0023]
First, in the insulating film forming step, as shown in FIG. 3, an insulating thermal oxide film 8 (for example, silicon oxide) is formed on a surface of substrates 2A and 2B (for example, a single crystal silicon wafer) to a predetermined thickness (for example, silicon oxide). , 1 μm).
In the film forming step, as shown in FIG. 4, a metal film (for example, chromium, chromium, or the like) is formed on one end surface of the substrates 2A and 2B (the surface of the thermal oxide film 8 formed in the insulating film forming step) by, for example, a sputtering method. The three-layer film 5 made of nickel and gold is formed to have a thickness of 0.1 μm, 1 μm, and 0.1 μm, respectively.
[0024]
In the electrode forming step, as shown in FIG. 5, an electrode wiring pattern (metal electrode 5 and input / output electrodes) is formed from the metal film formed in the film forming step (FIG. 4) by photolithography.
In the structure forming step, as shown in FIG. 6, a plurality of structures 7 (for example, an inner diameter of 100 μm and an outer diameter of 150 μm) are formed on the metal electrode 5 formed in the electrode forming step of FIG. (A cylindrical shape having a height of 50 μm, or a rectangular parallelepiped shape having a width of 100 μm, a length of 2.2 mm, and a height of 50 μm).
[0025]
Here, the structure pattern is such that the structure 7 is formed at the position where the P-type and N-type elements 3 and 4 are disposed, and the cutout 7 b of each structure 7 is formed by the metal electrode 5 provided with the structure 7. It is designed to be formed on the center side. The control wall 7d of the structure 7 is designed to be formed across the metal electrode.
In the mask forming step, as shown in FIG. 7, for example, a film photoresist 9 is coated on both sides of a P-type thermoelectric semiconductor material 3A and an N-type thermoelectric semiconductor material 4A made of a Bi-Te based sintered body by a coater. Apply.
[0026]
Next, openings for forming the solder bumps 6A on the photoresist in a pattern having a P-type and N-type arrangement in consideration of a bonding step (FIG. 11) and a cutting / removing step (FIG. 12) performed later. It is manufactured by a photolithography method so as to be able to perform.
In the Ni and solder plating process shown in FIG. 8, the opening of the photoresist is washed with an acid (for example, 10% sulfuric acid) or the like, and nickel plating 10 (for example, 15 μm in thickness) is formed in the opening, and then the solder is formed. Plating 11 (for example, the composition ratio of Sn and Pb is 6: 4 and the thickness is 50 μm) is formed.
[0027]
The nickel plating in this step enhances the adhesion between the solder and the thermoelectric semiconductor materials 3A and 4A, and at the same time, in the subsequent bonding step (FIG. 11) and cutting / removing step (FIG. 12), the substrate 2A, It has a role of forming a predetermined gap between 2B and the thermoelectric semiconductor materials 3A, 4A.
In the mask removing step, as shown in FIG. 9, the photoresist is stripped from the thermoelectric semiconductor materials 3A, 4A using, for example, acetone as a solvent.
[0028]
In the bump forming step, as shown in FIG. 10, a rosin-based solder flux is applied to the surface of the solder plating layer, and then a reflow process (for example, 230 ° C.) is performed to form a hemispherical solder bump 6A.
In the bonding step, as shown in FIG. 11, the structure 7 formed on the substrates 2A and 2B and the solder bump 6A formed on the thermoelectric semiconductor materials 3A and 4A in the structure manufacturing step (FIG. 6) are referred to. Alignment is performed, and the substrate 2B and the P-type thermoelectric semiconductor material 3A and the substrate 2A and the N-type thermoelectric semiconductor material 4A are respectively superposed. Then, the substrate 2B and the P-type thermoelectric semiconductor material 3A, and the substrate 2A and the N-type thermoelectric semiconductor material 4A are formed by heating (for example, 230 ° C.) and melting the solder bump 6A while pressing in the joining direction. It is fixed through the body 7.
[0029]
Here, in order to increase the bonding strength, a thin rosin-based flux is applied to the tip of the solder bump 6A.
In the cutting / removing step (pillaring step), as shown in FIG. 12, the thermoelectric semiconductor materials 3A and 4A joined to the substrates 2A and 2B in the joining step of FIG. 3 and 4 are formed. In this step, for example, a dicing blade used for cutting a silicon semiconductor or the like is used.
[0030]
In order to cut and remove the thermoelectric semiconductor materials 3A and 4A, a dicing blade is passed between the solder bumps 6A formed on the end faces of the thermoelectric semiconductor materials 3A and 4A, and the cutting depth at that time is set to only the thermoelectric semiconductor material. To the gap formed between the surface of the substrate and the thermoelectric semiconductor material, so that the bottom surfaces of the thermoelectric semiconductor materials 3A and 4A are separated from the substrates 2A and 2B as shown in FIG. The elements 3 and 4 can be formed in a state where they are joined via the structure 7 and the solder bumps 6A are formed on the upper surfaces of the thermoelectric semiconductor materials 3A and 4A.
[0031]
In the assembling step, as shown in FIG. 13, the substrates 2A and 2B on which the P-type and N-type elements 3 and 4 are formed in the cutting / removing step (FIG. 12) face the surfaces of the elements 3 and 4 respectively. After the solder bumps 6A on the upper surfaces of the elements 3 and 4 are brought into contact with the metal electrodes 5 of the other substrates 2B and 2A, the substrates 2A and 2B are heated (for example, at 230 ° C.) while being appropriately pressed in the bonding direction. By melting the solder bumps 6A, the substrates 2A and 2B are joined via the elements 3 and 4, and the thermoelectric element 1 can be manufactured. Here, in order to increase the bonding strength, a thin rosin-based flux is applied to the tip of the solder bump 6A.
[0032]
In the resin encapsulation step, as shown in FIG. 14, the thermoelectric element is filled with an epoxy resin as an encapsulating material from between the elements using a disperser.
When the amount of the encapsulant exceeds an appropriate amount, the encapsulant overflowing from between the elements does not flow out in the direction of the metal electrode because the control wall 7d of the structure 7 is provided. Therefore, in order to reduce the mechanical strength failure of the thermoelectric element caused by the insufficient amount of the encapsulating material, the amount is set slightly larger than an appropriate amount. After the filling is completed, it is left in a dryer at 100 ° C. for 2 hours to cure the sealing material.
[0033]
According to such a manufacturing method, for example, using a dicing blade having a blade thickness of 140 μm from a thermoelectric semiconductor material 3A, 4A having a thickness of 600 μm, the outer dimensions are 1.3 mm × 2 mm × 2.3 mm, and the number of elements is The thermoelectric element 1 having a total of 102 P-type and N-type and having an internal resistance of about 90Ω was able to be manufactured.
Here, the thermoelectric semiconductor materials 3A and 4A are Bi-Te-based sintered bodies. The main characteristics of the thermoelectric semiconductor materials 3A and 4A are that the P-type thermoelectric semiconductor material 3A has a Seebeck coefficient of 200 μV / K and a specific resistivity of 0.93 mΩcm. The N-type thermoelectric semiconductor material 4A has a Seebeck coefficient of -180 μV / K, a specific resistance of 0.97 mΩcm, and a thermal conductivity of 1.61 W / mK. One used.
[0034]
As described above, since the structure 7 is formed on the metal electrode and the Si substrate, and the encapsulant is filled between the elements, the encapsulant overflowing from the element can be controlled in the outflow direction by the structure 7. Thus, insulation failure that covers the electrodes can be prevented, and by filling the encapsulant more than an appropriate amount, the insufficient mechanical strength caused by insufficient filling of the encapsulant can be reduced.
[0035]
That is, in the production of the thermoelectric element, it is possible to reduce defects such as poor insulation of the electrode and poor mechanical strength, and it is possible to improve the yield.
In addition, since the mechanical strength of the thermoelectric element is improved by the encapsulating material, the elements 3 and 4 can be downsized, and more PN junction pairs can be formed in the thermoelectric element 1 having the same size. It becomes.
[0036]
Therefore, even with a small temperature difference, a large amount of electric power can be generated, and the thermoelectric element 1 can be used for power generation of various portable electronic devices such as an electronic wristwatch.
Further, the thermoelectric element 1 exerts a great effect even when used as a cooling element. That is, the cooling performance is determined by the electric power input to the thermoelectric element 1. In the case of the thermoelectric element 1, it is possible to supply a predetermined electric power with a low current. As a result, it is not necessary to make the input / output wiring thicker or to use a large current source for the power supply. Therefore, the thermoelectric element 1 can be used for cooling various electronic devices such as a semiconductor laser, for example.
[0037]
Note that the sizes, materials, and characteristics of the elements 3 and 4 shown in the present embodiment are not limited to these. For example, the size can be applied to a general size of several hundred μm to millimeter order. Further, as a material of the elements 3 and 4, a sintered body of a Bi-Te-based material has been described as an example. It is also applicable to materials.
[0038]
Also, as to the method of forming the elements 3 and 4 shown in the method of manufacturing the thermoelectric element, the individual elements 3 and 4 are formed and then the structure 7 of each of the substrates 2A and 2B is formed as in the conventional manufacturing method. May be provided at the position where the is formed.
In addition, the detailed configurations, methods, and the like specifically shown can be changed without departing from the gist of the present invention.
[0039]
【The invention's effect】
According to the configuration of the present invention, a structure having a predetermined height is formed on the metal electrode or the substrate, and the structure controls the flow of the sealing material when the sealing material is filled between the elements. It becomes possible.
For example, when the amount of the encapsulant is large, even if the amount of the encapsulant exceeds an appropriate amount, the encapsulant overflowing from between the elements may flow out in the direction of the metal electrode because the structure is provided. Therefore, the metal electrode is not covered with the encapsulating material, and the occurrence of insulation failure can be reduced.
[0040]
In addition, when the amount of the encapsulant is small, the mechanical strength of the thermoelectric element becomes small. Therefore, by setting the amount of the encapsulant slightly larger than an appropriate amount, the thermoelectric element generated due to the insufficient amount of the encapsulant is generated. It is possible to reduce poor mechanical strength of the element and supply an element having high mechanical strength. Further, since the mechanical strength is increased, it is possible to supply a fine thermoelectric element having a small element.
[0041]
According to the manufacturing method of the present invention, a structure is formed on a metal electrode or a substrate, and a P-type and an N-type element are joined to one of the two substrates. To fix the tips of the P-type and N-type elements and the metal electrodes of the substrate facing the tips so as to join the substrates, and then insert an encapsulant between the elements of the thermoelectric element. Fill. Therefore, even if the amount of the encapsulant exceeds an appropriate amount, since the encapsulant overflowing from between the elements does not flow out in the direction of the metal electrode due to the provision of the structure, the metal electrode is covered with the encapsulant. The occurrence of insulation failure can be reduced.
[0042]
In addition, when the amount of the encapsulant is small, the mechanical strength of the thermoelectric element becomes small. Therefore, by setting the amount of the encapsulant slightly larger than an appropriate amount, the thermoelectric element generated due to the insufficient amount of the encapsulant is generated. It is possible to reduce the mechanical strength failure of the element.
Therefore, the structure capable of controlling the flow direction of the sealing material flowing out between the P-type and N-type elements can reduce defects such as insulation failure and mechanical strength failure, and improve the yield in thermoelectric element manufacturing. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an overview of a thermoelectric element according to the present invention.
FIG. 2 is a plan view showing a structure pattern formed on a substrate constituting the thermoelectric element of FIG. 1;
FIG. 3 is a cross-sectional view illustrating an insulating film forming step in one example of a method for manufacturing a thermoelectric element.
FIG. 4 is a cross-sectional view showing a film forming process.
FIG. 5 is a cross-sectional view showing the same electrode manufacturing step.
FIG. 6 is a cross-sectional view showing the same structure manufacturing step.
FIG. 7 is a cross-sectional view showing the same mask forming step.
FIG. 8 is a sectional view showing a Ni and solder plating process.
FIG. 9 is a cross-sectional view showing the same mask removing step.
FIG. 10 is a cross-sectional view showing the same bump forming step.
FIG. 11 is a cross-sectional view showing the same bonding step.
FIG. 12 is a sectional view showing a cutting / removing step (pillaring step).
FIG. 13 is a cross-sectional view showing an assembling step.
FIG. 14 is a cross-sectional view showing a filling step of the encapsulating material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermoelectric element 2A, 2B Substrate 3 P-type element 3A P-type thermoelectric semiconductor material 4 N-type element 4A N-type thermoelectric semiconductor material 5 Metal electrode 6 Bonding material 7 Structure 7a Hollow part 7b Notch part 7c Connection wall 7d Control wall 8 Oxidation Film 9 photoresist 10 nickel 11 solder 12 encapsulant

Claims (2)

A P-type element made of a P-type thermoelectric semiconductor material;
An N-type element made of an N-type thermoelectric semiconductor material;
As well as have a metal electrode to form a PN junction pair with the P-type element according to the N-type element, and two substrates disposed opposite to the state sandwiching the P-type and N-type elements,
And the bonding material for bonding the metal electrode and the P-type and N-type elements,
A structure formed on at least one of the two substrates and having a predetermined height for controlling the flow of the encapsulant;
A thermoelectric element comprising: A method of manufacturing a thermoelectric element in which a P-type element made of a P-type thermoelectric semiconductor material and an N-type element made of an N-type thermoelectric semiconductor material are joined in pairs to form a PN junction pair ,
A first step of forming a metal electrode on the substrate,
A second step of forming a structure for controlling the flow of the encapsulant on one end side of the metal electrode or the substrate,
A third step of joining at least one of the P-type element and the N-type element to the metal electrode;
A step of fixing and joining the tip of the element provided on the substrate in the third step, and a metal electrode of a counter substrate facing the tip,
Filling a gap between the substrate and the counter substrate with an encapsulating material.

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