JP2004281930A - Method for producing thermoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a thermoelectric conversion element suitable for producing a high quality thermoelectric conversion element exhibiting excellent heat resistance and a low environmental load while reducing the production cost. <P>SOLUTION: In the method for producing a thermoelectric conversion element 1 comprising first and second substrates 4 and 5 provided with electrodes 6 and 7, and a plurality of P type and N type thermoelectric material elements 2 and 3 sandwiched between these substrates to have PN junction through the electrodes 6 and 7, a barrier metal layer 15, an Au layer 16 and an Sn layer 17 are formed sequentially on P type and N type thermoelectric material plates. The electrodes 6 and 7 of the substrates 4 and 5 and the P type and N type elements 2 and 3 made of a thermoelectric material are bonded by soldering at a low temperature allowing fusion of the Sn layer 17, and then the elements 2 and 3 are sandwiched between the substrates 4 and 5. Under that state, the Au layer 16 and the Sn layer 17 are diffusion bonded at a high temperature allowing fusion of the Au layer 16 and the Sn layer 17. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a thermoelectric conversion element 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]
The thermoelectric conversion element has a configuration in which a plurality of P-type and N-type thermoelectric material elements sandwiched between two substrates provided with electrodes are PN-joined via the electrodes of both substrates. The following two methods are known as methods for manufacturing this thermoelectric conversion element.
[0003]
In the first manufacturing method, a Ni plating layer is provided on both surfaces of the P-type and N-type thermoelectric material plates, and the thermoelectric material plate is cut to produce a plurality of P-type and N-type thermoelectric material elements. . Next, an electrode for PN junction and a substrate on which a bonding material is laminated are prepared, and each of the P-type and N-type thermoelectric material elements is disposed on the substrate. Thereafter, the electrode and the thermoelectric material element are soldered using the bonding material, thereby producing a thermoelectric conversion element in which the thermoelectric material element sandwiched between the two substrates is PN-joined via the electrode ( For example, see Patent Document 1.)
[0004]
In the second manufacturing method, bumps (brazing layers) are formed on both surfaces of the thermoelectric material plate corresponding to positions to be bonded to the electrodes of the substrate. The bump includes a Ni layer laminated on the thermoelectric material plate and a solder layer laminated on the Ni layer. Next, the bump on one surface of the thermoelectric material plate is soldered to the substrate using the solder layer, and the substrate and the thermoelectric material plate with bumps are joined. Thereafter, the thermoelectric material plate is cut to form thermoelectric material elements provided on the substrate. This step is performed individually for P-type and N-type thermoelectric material plates. Thereafter, one substrate to which the P-type thermoelectric material element is soldered and the other substrate to which the N-type thermoelectric material element is soldered are opposed to each other, and each thermoelectric material element is used as a substrate by using the solder layer. Soldering. Thus, a thermoelectric conversion element in which a thermoelectric material element sandwiched between two substrates is PN-joined via an electrode is produced (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-8-97472 (paragraphs 0005-0026, FIGS. 16, 17, paragraphs 0057-0064, FIGS. 1-4)
[0006]
[Problems to be solved by the invention]
In any of the manufacturing methods described in Patent Document 1, the electrode of the substrate and the thermoelectric material element are joined using a solder containing a lead component, for example, a solder having a composition ratio of tin to lead of 6: 4. Although lead-containing solder has the advantage of a low melting point, lead components are harmful to the natural environment. For this reason, it is required that the thermoelectric material element and the electrode of the substrate be joined using a joining material containing no lead component.
[0007]
Sn-Ag alloys, Sn-Cu alloys, Sn-Au alloys, and the like are known as so-called lead-free joining materials that substantially do not contain a lead component. By the way, a thermoelectric conversion element is used for temperature control of a semiconductor device for optical communication. In this case, the package of the semiconductor device and the substrate of the thermoelectric conversion element are joined by using a high melting point solder that can withstand heat generation of the semiconductor device.
[0008]
Under these circumstances, the present inventors have conducted intensive studies and have found that among lead-free joining materials, Sn-Au alloys, which are high melting point solders, particularly Sn-Au alloys having a composition ratio of Au: Sn of 8: 2, are used. I have found it to be promising.
[0009]
In order to use the Sn-Au alloy in the first manufacturing method, it has been found that it is preferable to solve the following problems. First, plating and screen printing are conceivable as means for laminating a bonding material made of an Sn-Au alloy over both surfaces of a thermoelectric material plate.
[0010]
However, the balance between Sn and Au during plating is quite unstable. For this reason, the composition of the plating layer obtained by plating tends to vary greatly, and it is difficult to reliably obtain a plating layer having a composition ratio of 8: 2. Thus, it is practically difficult to provide a bonding material made of an Sn-Au alloy by plating over the entire surface of both surfaces of the thermoelectric material plate.
[0011]
On the other hand, it is easy to print and provide the Sn-Au alloy on the entire surface of the thermoelectric material plate by screen printing using an ink in which the Sn-Au alloy powder is mixed into a flux to form a paste. . However, in screen printing, a part of the ink that passes through the screen is used. The remaining ink is used for printing again. However, the flux in the ink evaporates with several times of use, and the ink hardens and cannot be reused. That is, the solidified ink containing the Au powder is wasted. In the case of screen printing, the use efficiency of expensive ink is low as described above, and this is a factor in increasing the manufacturing cost. It is possible to extract and recover Au powder from the solidified ink. However, much labor is required, and the cost for recovery is higher than the cost for purchasing the ink as a raw material. Therefore, even if it is collected, it becomes an increasing factor of the manufacturing cost.
[0012]
The same applies to the case where the Sn-Au alloy is used in the second manufacturing method. Briefly, when a bonding material made of an Sn-Au alloy is provided at predetermined positions on both surfaces of a thermoelectric material plate by plating, it is difficult to precipitate a Sn-Au alloy having a stable composition, and the feasibility is high. Low. In the case where a bonding material made of an Sn-Au alloy is provided at predetermined positions on both surfaces of the thermoelectric material plate by screen printing, the use efficiency of expensive ink is low, which is a factor of increasing the manufacturing cost.
[0013]
The problem to be solved by the present invention is to provide a method for manufacturing a thermoelectric conversion element which has excellent heat resistance and is suitable for manufacturing a high-quality thermoelectric conversion element, has a small environmental load, and can reduce the manufacturing cost. It is in.
[0014]
[Means for Solving the Problems]
The present invention relates to a first and second substrates provided with electrodes, a plurality of P-type and N-type sintered thermoelectric material elements sandwiched between these substrates and PN-joined via the electrodes. A method for manufacturing a thermoelectric conversion element having
[0015]
In order to solve the above-mentioned problem, the present invention forms a brazing layer including a step of sequentially stacking a barrier metal layer, an Au layer, and a Sn layer on both surfaces of a P-type and N-type thermoelectric material plates. . Next, the thermoelectric material plate with the brazing layer or the P-type and N-type thermoelectric material elements made from this thermoelectric material and the electrodes of the substrate are soldered at a low temperature to enable melting of the Sn layer. Attach and join. Thereafter, while the thermoelectric material elements are sandwiched between the two substrates, the Au layer and the Sn layer are diffused at a high temperature at which the Au layer and the Sn layer of the brazing layers can be melted. By joining, a thermoelectric conversion element is manufactured.
[0016]
In a preferred embodiment of the present invention, the temperature of the brazing by the Sn layer is a temperature from a temperature exceeding the solidification temperature of the Sn layer to a temperature lower than the eutectic temperature of the Au-Sn alloy around 280 ° C. In a preferred embodiment of the present invention, the temperature of the diffusion bonding is a temperature equal to or higher than the eutectic temperature of the Au-Sn alloy near 280 ° C and lower than the sintering temperature of the thermoelectric material.
[0017]
In the present invention, examples of the thermoelectric material include a sintered material, for example, a sintered body such as a Bi-Te-based material or an Fe-Si-based material. In the present invention, examples of the barrier metal layer include Ni, Rh, a Ni-P alloy containing Ni as a main component, and a Ni-B alloy containing Ni as a main component. In the present invention, the composition ratio between the Au layer and the Sn layer is preferably 8: 2. In the present invention, the thermoelectric material element can be obtained by cutting a thermoelectric material plate having a brazing layer formed on the entire surface on both sides into a predetermined size, or corresponds to a portion where the thermoelectric material element is joined. The brazing layer can be obtained by removing a part of the thermoelectric material plate formed on both sides. In the present invention, the temperature at the time of the brazing by the Sn layer is preferably in the range of 232 ° C. to 250 ° C. in order to suppress the diffusion of the Au layer accompanying this bonding, and the solidification of the Sn layer is as much as possible. A temperature close to the temperature should be set. In the present invention, the temperature at the time of diffusion bonding between the Au layer and the Sn layer is preferably set in the range of 280 ° C. to 350 ° C. in order to suppress, for example, thermal deterioration of a thermoelectric material made of a Bi—Te-based material. Good to do.
[0018]
In the present invention, after the electrodes of the substrate and the thermoelectric material plate or thermoelectric material element are brazed and joined at a low temperature using the Sn layer, the P-type and the P-type are sandwiched between these substrates with both substrates facing each other. The Au layer and the Sn layer of the N-type thermoelectric material element are diffusion-bonded at a high temperature. Thereby, in the final form of bonding, the thermoelectric material element and the electrode of the substrate can be bonded with a high melting point Au-Sn alloy substantially containing no lead component. Furthermore, since the Au-Sn alloy is formed by diffusion bonding as described above, an Au-Sn alloy having a stable composition can be obtained as compared with a case where the alloy is deposited by plating, and the composition thereof can be obtained. Can also be easily controlled by controlling the thickness of the Au layer and the Sn layer. In addition, since no screen printing is performed, it is possible to reduce waste of the expensive Au layer.
[0019]
In a preferred embodiment of the present invention, the step of forming the brazing layer includes a wet back process for the Sn layer. This embodiment is excellent in that the Sn layer, which is located farthest from the plate surface of the thermoelectric material plate among the brazing layers, can be rounded into a hemispherical shape so that the height of the brazing layer can be increased and aligned. I have.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0021]
Reference numeral 1 in FIG. 5 indicates a thermoelectric conversion element manufactured by the manufacturing method of the first embodiment. The thermoelectric conversion element 1 obtains the Peltier effect and controls the temperature of, for example, a semiconductor device for optical communication. One of the substrates described below is connected to a package of the semiconductor device via a high melting point bonding material. Used in joined state.
[0022]
The thermoelectric conversion element 1 includes a plurality of P-type thermoelectric material elements (hereinafter, abbreviated as P-type elements or simply elements) 2 and a plurality of N-type thermoelectric material elements (hereinafter, N-type elements) paired with the element 2. Or simply referred to as an element.) 3 is sandwiched between first and second substrates 4 and 5 which are arranged to face each other, and via electrodes 6 and 7 provided on these substrates 4 and 5 respectively. PN junction. The P-type and N-type elements 2, 3 are connected in series by the PN junction. 2 to 5 are provided for facilitating the distinction between the P-type and N-type elements 2 and 3 and do not represent a cross section.
[0023]
For example, the size of each of the elements 2 and 3 in the thermoelectric conversion element 1 is 200 μm, and the shape of each of the elements 2 and 3 in a cross section parallel to the substrates 4 and 5 is preferably rectangular and preferably square. Is 250 μm. Alumina, aluminum nitride, a silicon wafer, or the like can be used as a material for the substrates 4 and 5, and the surface of the silicon wafer is an electrical insulating film formed by thermal oxidation. As a material for each of the elements 2 and 3, a sintered body of a Bi-Te-based material, which is a material having excellent performance near room temperature (room temperature), can be suitably used. The coefficient of thermal expansion of the material of each element 2, 3 is greater than the coefficient of thermal expansion of the material of the substrates 4, 5.
[0024]
The thermoelectric conversion element 1 having the above configuration is manufactured through a bump forming step, a first bonding step, an element forming step, and a second bonding step, which will be described below, in this order.
[0025]
The bump forming step is a step of forming a brazing layer at a predetermined position on both plate surfaces (both surfaces) of the P-type and N-type thermoelectric material plates. Since these steps are the same, a procedure for forming the brazing layer 14 on the P-type thermoconductive material plate 12 shown in FIGS. 1A to 1E will be described as a representative. Note that reference numeral 13 in FIGS. 1A to 1E indicates an N-type thermoelectric material plate.
[0026]
The brazing layer 14 functions as a bump for mechanically and electrically joining the substrate and the thermoelectric material. The layer 14 is formed by laminating a barrier metal layer 15, an Au layer 16, and a Sn layer 17 in this order.
[0027]
Specifically, first, a photoresist 18 having a predetermined thickness is applied to the entire area of both plate surfaces f1 and f2 of the P-type thermoelectric material plate 12, and the photoresist 18 is exposed and developed to be arranged in a predetermined pattern. A large number of circular openings 19 are formed. The state in which the opening 19 is formed is schematically illustrated in FIG. Here, the predetermined arrangement pattern of the openings 19 corresponds to the arrangement of the elements 2 and 3 of the thermoelectric conversion element 1.
[0028]
Next, the barrier metal layer 15 is formed on the bottom surface of each opening 19 by plating, for example, Ni (nickel) as a barrier metal by an electroplating method. FIG. 1B schematically illustrates a state in which the barrier metal layer 15 is stacked on the plate surfaces f1 and f2 of the thermoelectric material plate 13.
[0029]
Thereafter, Au (gold) is plated by electroplating to form an Au layer 16 on each barrier metal layer 15. FIG. 1C schematically illustrates a state in which the Au layer 16 is stacked on the barrier metal layer 15.
[0030]
Subsequently, Sn (tin) is plated by electroplating to form an Sn layer 17 on each Au layer 16. In this case and in the previous stage, the film thickness of the Au layer 16 and the Sn layer 17 is set such that the composition ratio of the alloy formed by the Au layer 16 and the Sn layer 17 by diffusion bonding described later is Au: Sn = 8: 2. Is set. This setting can be easily performed by controlling the quantity of electricity during plating. FIG. 1D schematically illustrates a state in which the Sn layer 17 is stacked on the Au layer 16.
[0031]
Finally, the photoresist 18 is stripped. Thereby, the brazing layers 14 are formed in a predetermined arrangement pattern on each of both plate surfaces f1 and f2 of the P-type thermoelectric material plate 12. FIG. 1E schematically illustrates a P-type thermoelectric material plate 12 in which a brazing layer 14 is formed by laminating both plate surfaces f1 and f2. The brazing layer 14 is formed in a predetermined arrangement pattern on the plate surfaces f1 and f2 of the N-type thermoelectric material plate 13 in the same procedure.
[0032]
At each stage of the above bump forming process, cleaning using an acid or the like is performed as necessary.
[0033]
The first bonding step is performed by preparing P-type and N-type substrates 4 and 5 which have already been manufactured. As shown in FIGS. 2A and 2B, electrodes 6 or 7 are provided on one surface of the substrates 4 and 5 in a wiring pattern for electrically connecting the elements 2 and 3 in series. The electrodes 6 and 7 can be provided on one surface of the substrates 4 and 5 by sputtering, in the order of chromium, nickel, and gold from the substrate side, and then provided with a predetermined wiring pattern by photolithography.
[0034]
As shown in FIG. 2 (A), one plate surface f1 of the N-type thermoelectric material plate 13 with bumps faces the electrode surface of the N-type substrate 5, and each brazing layer 14 Positioning is performed so as to be located at a position, that is, a portion where the N-type element 3 is joined. Thereafter, the Sn layer 17 of the brazing layer 14 in contact with the electrode 7 is melted, and the brazing layer 14 is joined to the above-mentioned portion. Thus, the N-type thermoelectric material plate 13 and the substrate 5 are brazed as shown in FIG.
[0035]
Similarly, as shown in FIG. 2B, one plate surface f1 of the P-type thermoelectric material plate 12 with bumps and the electrode surface of the P-type substrate 4 are opposed to each other, and each brazing layer 14 has an electrode. Positioning is performed so as to be arranged at a predetermined position of No. 6, that is, at a site where the P-type element 2 is joined. After that, the Sn layer 17 of the brazing layer 14 in contact with the electrode 6 is melted, and the brazing layer 14 is joined to the above-mentioned portion. As a result, the P-type thermoelectric material plate 12 and the substrate 4 are brazed as shown in FIG. These bondings are performed by heating under pressure in a non-oxidizing atmosphere such as an inert gas atmosphere or a vacuum atmosphere.
[0036]
These bondings are performed at a low temperature at which the Sn layer 17 can be melted, for example, at a temperature higher than the solidification temperature of the Sn layer 17 to a temperature lower than the eutectic temperature of the Au-Sn alloy around 280 ° C. Preferably, the bonding is performed at a temperature within the range of 232 ° C. to 250 ° C., and more preferably, a temperature as low as possible within this preferable temperature range.
[0037]
Performing the first bonding at such a low temperature is preferable in that the diffusion of the Au layer 16 of the brazing layer 14 is easily suppressed and the warpage of the thermoelectric material plate 12 or 13 is easily suppressed. If the first joining step is performed at 280 ° C. or higher, cracks (including cracks) may occur in the thermoelectric material bodies 12, 13 due to the thermal expansion difference between the thermoelectric material plates 12, 13 and the substrates 4, 5. Oxidization, diffusion bonding, and deformation.
[0038]
The warpage will be described. Since the thermoelectric material plates 12 and 13 are more likely to thermally expand than the substrates 4 and 5, the higher the bonding temperature in the first bonding step, the greater the amount of expansion of the thermoelectric material plates 12 and 13 with respect to the substrates 4 and 5. For this reason, the thermoelectric material plates 12 and 13 generate a large warp in which the thermoelectric material plates 12 and 13 approach the substrates 4 and 5 from the peripheral part toward the center part due to a large shrinkage due to a temperature decrease after the bonding. If such a warp remains in the thermoelectric material plates 12 and 13, in cutting and removing in the element forming step described later, poor element formation due to insufficient cutting of the thermoelectric material plates 12 and 13 and electrode cutting due to excessive cutting are caused. It will be easier. However, such inconveniences are less in the first embodiment in which the warpage of the thermoelectric material plates 12 and 13 can be suppressed to be small in the first joining step as described above. Therefore, it is possible to improve the yield.
[0039]
In the element forming step, the thermoelectric material plates 12 and 13 bonded to the substrates 4 and 5 are cut in the thickness direction to remove a part of the area, so that the elements 2 or 3 bonded to the substrates 4 and 5 are respectively predetermined. Get the number. At this time, the substrates 4, 5 or the electrodes 6, 7 may be cut and removed as needed. The cutting in this step can be performed using, for example, a dicing saw having a predetermined thickness suitable for removing the partial region. This cutting is performed along the vertical and horizontal directions (XY directions) of the thermoelectric material plates 12 and 13. As a result, a plurality of P-type elements 2 or N-type elements 3 each having a predetermined size and having the brazing layer 14 at both ends, as schematically illustrated in FIGS. It is provided standing up.
[0040]
In the second bonding step, the substrate 4 to which the P-type element 2 is bonded and the substrate 5 to which the N-type element 3 is bonded face each other as schematically shown in FIG. Thereafter, the Sn layer 17 forming the surface layer of the other brazing layer 14 provided at the tip of each of the elements 2 and 3 and the elements of the electrodes 6 and 7 formed on the substrates 4 and 5 should be joined. Align with the site. Next, the Au layer 16 and the Sn layer 17 of each brazing layer 14 are melted, so that the Au layer 16 and the Sn layer 17 are diffusion-bonded, and the respective elements 2, 3 are connected to the portions of the electrodes 6, 7. To join. This bonding is performed by heating under pressure in a non-oxidizing atmosphere such as an inert gas atmosphere or a vacuum atmosphere.
[0041]
As a result, an Au—Sn alloy layer 20 is formed as schematically shown in FIG. 5, and this layer 20 is used as a bonding layer to mechanically and electrically connect the elements 2 and 3 and the electrodes 6 and 7 of the substrates 4 and 5. The connection is made electrically, and the thermoelectric conversion element 1 is assembled. By this assembling, the elements 2 and 3 are sandwiched between the substrates 4 and 5, and PN junctions are formed through the electrodes 6 and 7, and the PN junction pairs are electrically connected in series.
[0042]
In the bonding in the second bonding step, a high temperature at which the Au layer and the Sn layer 17 can be melted, that is, a temperature higher than the eutectic temperature of the Au-Sn alloy around 280 ° C. and lower than the sintering temperature of the elements 2 and 3 Done at temperature. In this case, the bonding is preferably performed at a temperature in the range of 280 ° C. to 350 ° C., and more preferably, a temperature as low as possible, for example, 280 ° C. in this preferable temperature range.
[0043]
Performing the second bonding at such a high temperature allows diffusion bonding of the Au layer 16 and the Sn layer of the brazing layer 14 and also causes thermal degradation of the sintered elements 2 and 3. It is preferable because it does not exist. In this second joining step, although the joining is performed at a temperature higher than the joining temperature in the first joining step, the thermoelectric material plate does not exist at this stage and the elements 2 and 3 are already formed. There is no warpage due to the difference in thermal expansion which causes a problem.
[0044]
As described above, the Au-Sn alloy layer 20 obtained by diffusion bonding of the Au layer 16 and the Sn layer 17 of the brazing layer 14 and the P-type and N-type elements 2, 3 are sandwiched therebetween. The electrodes 6, 7 of the arranged first and second substrates 4, 5 are joined. For this reason, it is possible to provide the junction with high heat resistance of 280 ° C. or higher, which is the melting temperature of the Au—Sn alloy layer 20, and it is possible to manufacture the thermoelectric conversion element 1 having excellent durability against high temperatures. Therefore, the thermoelectric conversion element 1 manufactured by the method of the present invention can be suitably used as an element for controlling the temperature of the semiconductor device for optical communication.
[0045]
Then, since the Au-Sn alloy layer 20 is obtained by the above-described diffusion bonding and the elements 2, 3 and the substrates 4, 5 are joined, the Au-Sn alloy layer 20 is previously formed on the elements 2, 3 by plating. Then, it is possible to stably obtain the Au—Sn alloy layer 20 having a composition of 8: 2 as compared with the case of melting and joining them. Moreover, in this case, the composition of the Au—Sn alloy layer 20 can be easily controlled by controlling the thicknesses of the Au layer 16 and the Sn layer 17. For this reason, the composition of the Au—Sn alloy layer 20 can be stabilized, and accordingly, the quality of the manufactured thermoelectric conversion element 1 can be improved.
[0046]
Further, since the Au—Sn alloy layer 20 is obtained by the diffusion bonding described above, it is not necessary to perform screen printing to obtain the alloy layer 20. For this reason, there is no increase in cost due to waste of the paste containing Au powder, which has a high material cost, and the cost can be reduced as compared with the case where screen printing is performed.
[0047]
In addition, the Au-Sn alloy layer 20 joining the elements 2 and 3 and the substrates 4 and 5 does not contain a lead component, so that the manufacturing method of the present invention has a small load on the environment.
[0048]
FIG. 6 shows a second embodiment of the present invention. Since this embodiment has basically the same configuration as the first embodiment, the same portions are denoted by the same reference numerals as those in the first embodiment, and the description of the configuration and operation will be omitted, and different portions will be described below. I do.
[0049]
The bump forming process in the second embodiment includes a wet back process performed at the final stage. This wet-back process is performed by applying a flux such as rosin to each brazing layer 14 made as shown in FIG. And further washing. Thereby, each Sn layer 17 at the tip of each brazing layer 14 is rounded into a hemisphere as shown in FIG.
[0050]
For this reason, the height of the brazing layer 14 can be made high and uniform. As a result, the distance between the thermoelectric material plates 12 and 13 joined with the brazing layer 14 interposed therebetween and the substrates 4 and 5 individually corresponding thereto can be made large. Therefore, when the elements 2 and 3 are formed by cutting and removing a part of the thermoelectric material plates 12 and 13 in the above-described element forming step to be performed next, the cutting depth of the dicing saw has a large margin. Therefore, it is excellent in that the element forming step can be easily performed. Except for the points described above, the third embodiment is the same as the first embodiment.
[0051]
7 to 10 show a third embodiment of the present invention. Since this embodiment has basically the same configuration as the first embodiment, the same portions are denoted by the same reference numerals as those in the first embodiment, and the description of the configuration and operation will be omitted, and different portions will be described below. I do. The parallel diagonal lines shown in FIGS. 8 to 10 are provided for facilitating the distinction between P-type and N-type elements, and do not represent cross sections.
[0052]
In the third embodiment, the thermoelectric conversion element 1 is manufactured by sequentially obtaining the element forming step, the first joining step, the assembling step, and the second joining step.
[0053]
In the element forming step, first, as shown in FIGS. 7B to 7D, the entire region of both plate surfaces f1 and f2 of the P-type and N-type thermoelectric material plates 12 and 13 shown in FIG. The barrier metal layer 15, the Au layer 16, and the Sn layer 17 are sequentially stacked by plating. Next, these thermoelectric material plates 12 and 13 are cut along the XY direction using a dicing saw or the like, and a plurality of P-type and N-type thermoelectric material elements having brazing layers 14 at both ends. Make 2 and 3.
[0054]
In the first joining step, a first substrate 4 on which electrodes 6 are formed in advance is prepared, and the P-type and N-type elements 2 and 3 are arranged on the substrate 4 in a predetermined arrangement. In this state, one end of each of the elements 2 and 3 is connected to the electrode 6 at a low temperature at which the Sn layer 17 of the brazing layer 14 at the one end in contact with the electrode 6 can be melted. Braze and join. The bonding conditions in this step are the same as those in the first embodiment, and the bonded state is schematically shown in FIG.
[0055]
In the assembling process, a second substrate 5 on which the electrodes 7 are formed in advance is prepared, and the electrodes 7 of the substrate 5 are brought into contact with the other ends of the P-type and N-type elements 2 and 3 joined to the first substrate 4. Let it. As a result, the second substrate 5 is opposed to the first substrate 4, and the elements 2 and 3 are assembled in a state where the elements 2 and 3 are sandwiched between the substrates 4 and 5. The assembled state is shown schematically in FIG.
[0056]
After the assembly, in a second bonding step performed, the Au layer 16 and the Sn layer 17 are diffusion-bonded at a high temperature at which the Au layer 16 and the Sn layer 17 of each brazing portion 14 can be melted. The bonding conditions and the like in this step are the same as those in the first embodiment, and the bonded state, that is, the manufactured thermoelectric conversion element 1 is schematically shown in FIG.
[0057]
That is, in the third embodiment in which the above-described steps are performed to manufacture the thermoelectric conversion element 1, similarly to the first embodiment, first, the barrier metal layer 15 is formed on the P-type and N-type thermoelectric material plates 12 and 13. , Au layer 16 and Sn layer 17 are sequentially laminated. Next, the P-type and N-type elements 2 and 3 made of the thermoelectric material plates 12 and 13 and the electrode 6 of the substrate 4 are joined by brazing at a low temperature at which the Sn layer 17 can be melted. Thereafter, with the elements 2 and 3 sandwiched between the substrates 4 and 5, the Au layer 16 and the Sn layer of each brazing layer 14 are heated at a high temperature to enable melting of the Au layer 16 and the Sn layer 17. The thermoelectric conversion element 1 is manufactured by diffusion bonding with the layer 17.
[0058]
Therefore, the manufacturing method of the third embodiment also has excellent heat resistance and is suitable for manufacturing a high-quality thermoelectric conversion element, has a small load on the environment, and can reduce the manufacturing cost of the thermoelectric conversion element.
[0059]
In each of the above embodiments, the substrates 4 and 5 provided with the electrodes 6 and 7 in advance are prepared. However, before the first bonding step is started, the electrodes 4 and 5 are formed on the substrates 4 and 5 by the above-described procedure or the like. It is also possible to carry out the method of the present invention by providing an electrode forming step for attaching.
[0060]
【The invention's effect】
According to the present invention, the thermoelectric material element and the electrode of the substrate are joined by the Au—Sn alloy layer obtained by diffusion-joining the Au layer and the Sn layer laminated by plating. It is possible to give. In addition, since the Au—Sn alloy layer used for this bonding does not substantially contain a lead component, the load on the environment is small. At the same time, an Au—Sn alloy having a stable composition can be obtained by the diffusion bonding described above, and the composition of the alloy can be easily controlled by controlling the thickness of the Au layer and the Sn layer. It is possible to improve the quality of the thermoelectric conversion element. Furthermore, since screen printing using a paste containing Au powder, which has a high material cost, is not performed, it is possible to provide a method for manufacturing a thermoelectric conversion element that has advantages such as less waste and cost reduction.
[Brief description of the drawings]
FIGS. 1A to 1E are views sequentially showing steps of forming bumps on a thermoelectric material plate by a manufacturing method according to a first embodiment of the present invention.
FIGS. 2A and 2B are views showing a first bonding step of brazing a P-type or N-type thermoelectric material on a substrate by the manufacturing method according to the first embodiment;
FIG. 3 is a view showing a step of providing a thermoelectric material element on a substrate by the manufacturing method of the first embodiment.
FIG. 4 is a view showing a process of assembling two thermoelectric material elements on two substrates by the manufacturing method of the first embodiment.
FIG. 5 is a view showing a second bonding step in the manufacturing method according to the first embodiment.
FIG. 6 is a view showing a state in which a wet-back process has been performed on bumps in the manufacturing method according to the second embodiment of the present invention.
FIGS. 7A to 7E are views sequentially showing steps of forming a thermoelectric material element with a brazing layer from a thermoelectric material plate by a manufacturing method according to a third embodiment of the present invention.
FIG. 8 is a view showing a first joining step of providing a thermoelectric material element on a substrate by the manufacturing method of the third embodiment.
FIG. 9 is a view showing an assembling process of two substrates and each thermoelectric material element in the manufacturing method of the third embodiment.
FIG. 10 is a view showing a second bonding step in the manufacturing method according to the third embodiment.
[Explanation of symbols]
1. Thermoelectric conversion element
2. P-type element (P-type thermoelectric material)
3. N-type element (N-type thermoelectric material)
4: First substrate
5 Second substrate
6: electrodes on the first substrate
7 ... electrode on the second substrate
12 P-type thermoelectric material plate
13 ... N-type thermoelectric material plate
f1, f2: plate surface of each thermoelectric material plate
14. Brazing layer
15 ... Barrier metal layer
16 Au layer
17: Sn layer
20: Au-Sn alloy layer

Claims (6)

A thermoelectric material comprising: first and second substrates provided with electrodes; and a plurality of P-type and N-type sintered thermoelectric material elements sandwiched between the substrates and PN-joined via the electrodes. A method for manufacturing a conversion element,
Forming a brazing layer including sequentially stacking a barrier metal layer, an Au layer, and a Sn layer on both surfaces of the P-type and N-type thermoelectric material plates;
Brazing bonding of the thermoelectric material plate with the brazing layer or the P-type and N-type thermoelectric material elements made from the thermoelectric material plate and the electrode of the substrate at a low temperature enabling melting of the Sn layer The process of
A step of diffusion-bonding the Au layer and the Sn layer at a high temperature that allows melting of the Au layer and the Sn layer of the brazing layers while the thermoelectric material elements are sandwiched between the two substrates; When,
The manufacturing method of the thermoelectric element provided with. A thermoelectric material comprising: first and second substrates provided with electrodes; and a plurality of P-type and N-type sintered thermoelectric material elements sandwiched between the substrates and PN-joined via the electrodes. A method for manufacturing a conversion element,
A barrier metal layer, an Au layer, and a Sn layer will be sequentially laminated on both surfaces of the P-type and N-type thermoelectric material plates and on the electrode corresponding to the arrangement of the P-type or N-type thermoelectric material elements. Forming an additional layer;
Using the Sn layer of each of the brazing layers formed on one surface of the P-type thermoelectric material plate, the electrode of the first substrate and the one thermoelectric material plate at a low temperature enabling melting of the Sn layer. And using the Sn layer of each of the brazing layers formed on one surface of the N-type thermoelectric material plate, with the electrode of the second substrate at a low temperature that enables melting of the Sn layer. A step of brazing and joining the other thermoelectric material plate,
A part of the P-type thermoelectric material plate is removed to provide a plurality of the P-type thermoelectric material elements on the first substrate, and a part of the N-type thermoelectric material plate is removed to remove the N-type thermoelectric material. Providing a material element on the second substrate;
In a state where the first and second substrates to which the P-type or N-type thermoelectric material elements are bonded are opposed to each other and the thermoelectric material elements are sandwiched between the first and second substrates, the second substrate And the P-type thermoelectric material element are diffusion-bonded at a high temperature that allows their melting using the Au layer and the Sn layer of the brazing layer of the element, and at the same time, the electrode of the first substrate and the electrode Diffusion bonding the N-type thermoelectric material element at a high temperature to enable melting thereof by using an Au layer and a Sn layer of a brazing layer of the element;
The manufacturing method of the thermoelectric conversion element provided with. 3. The method of manufacturing a thermoelectric conversion element according to claim 1, wherein the step of forming the brazing layer includes a wet back process on the Sn layer. 4. A thermoelectric material comprising: first and second substrates provided with electrodes; and a plurality of P-type and N-type sintered thermoelectric material elements sandwiched between the substrates and PN-joined via the electrodes. A method for manufacturing a conversion element,
A brazing layer is formed by sequentially laminating a barrier metal layer, an Au layer, and a Sn layer on both sides of the P-type and N-type thermoelectric material plates, and cutting the thermoelectric material plate with the brazing layer. Making a plurality of P-type and N-type thermoelectric material elements having said brazing layer at both ends;
The electrode of one of the substrates and one end of the P-type and N-type thermoelectric material elements are brazed at a low temperature to enable melting of the Sn layer by using the Sn layer of the brazing layer at the one end. Process and
The other substrate is opposed to the other substrate such that an electrode of the substrate is in contact with the other end of the P-type and N-type thermoelectric material elements joined to the one substrate, and the thermoelectric material An assembling step of sandwiching an element between the first and second substrates, and after this assembling, diffusion bonding of the Au layer and the Sn layer at a high temperature that enables melting of the Au layer and the Sn layer of the brazing layer The process of
The manufacturing method of the thermoelectric conversion element provided with. 5. The method of manufacturing a thermoelectric conversion element according to claim 1, wherein the temperature of the brazing joint by the Sn layer is less than a eutectic temperature of the Au—Sn alloy around 280 ° C. from a temperature exceeding a solidification temperature of the Sn layer. Temperature. 6. The method of manufacturing a thermoelectric conversion element according to claim 1, wherein the temperature of the diffusion bonding is equal to or higher than the eutectic temperature of the Au—Sn alloy around 280 ° C. and lower than the sintering temperature of the thermoelectric material. .

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