JP2004328013A - Thermoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric conversion element of a small size and a thin type along with its manufacturing method, where the number of chips of a thermoelectric material can be increased per unit area. <P>SOLUTION: Thermoelectric material wafers 40 of P-type and N-type are jointed with an interval to substrates 42 of P-type and N-type where an electrode wiring 43 is provided. The thermoelectric material wafer 40 jointed to the substrate 42 is cut to remove an unnecessary part by utilizing the interval, providing the substrate 42 to which a thermoelectric material chip 45 is jointed. The substrates 42 jointed to the P-type thermoelectric material chip and the N-type thermoelectric material chip are adapted to face each other, and the tip of the chip is jointed to the electrode wiring 43 on the substrate to form PN junction. A structure 44 for both alignment and prevention of flowing of a bonding agent at jointing twice is provided around the jointing part of the substrate 42. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoelectric conversion 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 a method of manufacturing the same.

  The thermoelectric conversion element is manufactured by joining a P-type thermoelectric material and an N-type thermoelectric material via an electrically conductive electrode such as a metal to form a PN junction pair. This thermoelectric conversion element generates a thermoelectromotive force based on the Seebeck effect by giving a temperature difference between a pair of junctions, so it is used as a power generation device. There is a use as a cooling device or a precision temperature control device using the so-called Peltier effect that generates heat.

  Generally, a thermoelectric conversion element is used as a module in which a plurality of PN junction pairs are connected in series in order to improve the performance. This module has a structure in which P-type and N-type thermoelectric material pieces (referred to as thermoelectric material chips) each having a rectangular parallelepiped shape having several sides of several hundred μm to several mm are electrically insulating substrates such as alumina and aluminum nitride. The P-type thermoelectric material chip and the N-type thermoelectric material chip are PN-joined with electrodes made of a conductive material such as metal formed on the substrate, and at the same time, the thermoelectric material chips are connected in series. Is connected to

  FIG. 15 shows a cross section of a conventional thermoelectric conversion element having such a structure (hereinafter, referred to as a thermoelectric conversion element including a module in which a plurality of thermoelectric material chips are arranged) in a direction parallel to the substrate and perpendicular to the substrate. FIG. 3 is a diagram showing an arrangement of electrodes of a substrate and a thermoelectric material chip in a cross section of various parts. FIG. 15A is a view showing the arrangement of the electrode wiring and the thermoelectric material chip on the substrate in a cross section in the direction parallel to the substrate of the conventional thermoelectric conversion element. In other words, the arrangement of the electrode and the thermoelectric material chip from the top of the substrate. It is the figure which was seen through in order to show.

  The electrode pattern indicated by the solid line indicates the electrode wiring 151 of the upper substrate, and the electrode pattern indicated by the dotted line indicates the electrode wiring 152 of the lower substrate. A hatched rectangle inside the intersection of the upper substrate electrode wiring 151 and the lower substrate electrode wiring 152 indicates a portion where the P-type thermoelectric material chip 153 and the N-type thermoelectric material chip 154 are arranged. Is shown. FIGS. 15B, 15C and 15D are views showing vertical sections taken along X1-X1 ', X2-X2' and Y1-Y1 'in FIG. 15A. As can be seen from FIG. 15, the arrangement of the thermoelectric material chips in the conventional thermoelectric conversion element is arranged in a grid on the substrate, and each side constituting the grid (the X direction and the Y direction in FIG. 15A). In the above, the P-type thermoelectric material chips and the N-type thermoelectric material chips were arranged so as to always appear alternately.

  An outline of a conventional method for manufacturing a thermoelectric conversion element including a plurality of thermoelectric material chips will be described below.

  FIG. 16 is a diagram showing an outline of processing of a thermoelectric material in the production of a conventional thermoelectric conversion element by a longitudinal section thereof. FIG. 16A shows a cross section of a thermoelectric material 161 processed into a plate shape or a rod shape. A layer 162 for soldering Ni or the like is formed on both sides of the surface of the thermoelectric material to be joined to the substrate by a plating method (FIG. 16B). Next, by cutting the thermoelectric material, thermoelectric material chips 163 having layers 162 for soldering on both sides are prepared for P-type and N-type (FIG. 16C).

  Next, each of the thermoelectric material chips manufactured in this manner is arranged on a predetermined electrode wiring on a substrate by using a jig or the like, and joined to manufacture a thermoelectric conversion element.

  FIG. 17 is a diagram showing a conventional manufacturing method for manufacturing a thermoelectric conversion element using a substrate provided with thermoelectric material chips and wiring. FIG. 17A shows a state of the substrate 171 and the thermoelectric material chip 172 before joining. An electrode wiring 173 for performing PN junction and a bonding material 174 for bonding the thermoelectric material chip 172 are formed in a layer on the substrate 171. FIG. 17B is a longitudinal sectional view of a thermoelectric conversion element 175 formed by joining the respective parts.

  The size of each thermoelectric material chip used as a thermoelectric conversion element is a rectangular parallelepiped having a side of several hundred μm to several mm, but in recent years, an element used under a temperature difference of several tens degrees near room temperature has a large size. Those having a thickness of several tens to several hundreds of micrometers are said to have higher performance. For example, IEICE Transactions C-II, Vol. J75-C-II, No. 8, pp. Such contents are described in 416-424 and the like, while simultaneously discussing the importance of design against heat.

In addition, the number of thermoelectric material chip pairs in one thermoelectric conversion element is at most several hundred, and the density is also up to about several tens of pairs / cm ² , but the number of thermoelectric material chip pairs may be increased. It is one of the very important factors in improving performance and expanding its applications. In particular, in power generation using a small temperature difference, the generated electromotive force is proportional to the number of thermoelectric material chip pairs, so in order to extract a high voltage, increase the number of thermoelectric material chips connected in series in the thermoelectric conversion element as much as possible. It is desired. Furthermore, even when a thermoelectric conversion element is used as a cooling element or a temperature control element, if the number of thermoelectric material chips arranged in series is small, the current flowing through the element becomes large, so that the wiring and the power supply become large. Therefore, it is desired to arrange as many thermoelectric material chips in series as possible.

  As described above, the miniaturization, thinning, thermal design, and the increase in the number of thermoelectric material chip pairs connected in series in one thermoelectric conversion element lead to the high performance of the thermoelectric conversion element, and at the same time, the point of expanding applications. It is becoming.

  However, when the thermoelectric conversion element having the conventional structure shown in FIG. 15 is manufactured by the manufacturing method shown in FIGS. 16 and 17, it is necessary to handle the thermoelectric material chips one by one. Considering this, there is a limit to reducing the size of the chip and the size of the element. Materials such as Bi-Te-based materials and Fe-Si-based materials, which are particularly good thermoelectric materials, are materials with low mechanical strength, so the size of the thermoelectric material chip is several hundred μm or less. When a thermoelectric conversion element having an extremely large number of chips is manufactured, it is difficult to handle the thermoelectric material, and it is difficult to manufacture a thermoelectric conversion element having a conventional structure by a conventional manufacturing method.

  Therefore, an object of the present invention is to reduce the size of a thermoelectric material chip and increase the number of thermoelectric material chips per unit area (chip density), thereby providing a small and high-performance thermoelectric conversion element and a method of manufacturing the same. Is to provide.

  Therefore, the present invention can adopt a new manufacturing method by changing the arrangement of the thermoelectric material chips on the substrate in the conventional thermoelectric conversion element, thereby reducing the size of the thermoelectric material chips and reducing the chip density. It is intended to obtain an increased thermoelectric conversion element.

  That is, the thermoelectric conversion element of the present invention is composed of two substrates on which electrodes are wired, and at least one pair or more of chip-shaped P-type and N-type thermoelectric materials sandwiched therebetween and PN-joined via the electrode wiring. The thermoelectric material chip has a rectangular cross section in a plane parallel to the substrate, and connects the centers of the squares of the P-type and N-type thermoelectric material chips forming an electrical pair. The thermoelectric material chip and the thermoelectric material chip are formed on the substrate such that the position and direction relationship between the straight line and the four sides forming the square of each thermoelectric material chip forming the PN junction pair are not orthogonal or parallel. And a PN junction electrode.

  Therefore, depending on the positional relationship between the P-type thermoelectric material chip and the N-type thermoelectric material chip, and the directional relationship between the P-type and N-type thermoelectric material chips and the PN junction electrode, a thermoelectric conversion element having a plurality of PN junctions can be used. Since the degree of freedom in design can be increased at the same time as the degree of freedom in design can be increased, it is possible to manufacture a thermoelectric conversion element composed of thermoelectric material chips located under several hundreds of trenches.

Further, in the thermoelectric conversion element of the present invention, a dummy thermoelectric material chip that is not electrically connected is joined and arranged in the element in addition to the thermoelectric material chip having a PN junction constituting the element.
That is, the mechanical strength of the thermoelectric conversion element can be increased by joining the electrically separated thermoelectric material chip to the substrate.

Further, the thermoelectric conversion element of the present invention has an electrode in which a plurality of thermoelectric material chips of the same type are joined on one electrode among electrodes for forming a PN junction pair formed on a substrate. Is what it is.
That is, since the thermoelectric material chip of the same type is joined to one electrode for PN junction, the mechanical strength is increased, and even if one is damaged, it can function as an element.

  Alternatively, the thermoelectric conversion element of the present invention is composed of two substrates on which electrodes are wired, and at least one or more pairs of chip-shaped P-type and N-type thermoelectric materials sandwiched therebetween and PN-joined via the electrode wiring. A thermoelectric material chip whose thermoelectric material chip has a rectangular cross section in a plane parallel to the substrate, and a thermoelectric material chip on the substrate which has a rectangular side which is a cross sectional shape of the thermoelectric material chip. The chips are arranged in a lattice in the direction, and the arrangement of the chips constituting one side of the lattice is such that the P-type thermoelectric material chips and the N-type thermoelectric material chips are alternately arranged, and the P-type thermoelectric material chips are arranged on the other side. The rows in which only the N-type thermoelectric material chips are arranged are alternately arranged.

  That is, the positional relationship between the P-type thermoelectric material chip and the N-type thermoelectric material chip and the relationship between these arrangements increase the degree of freedom in designing a thermoelectric conversion element having a plurality of PN junctions, and at the same time expand the degree of freedom in the manufacturing method. Therefore, it is possible to manufacture a thermoelectric conversion element composed of thermoelectric material chips under several hundreds of trenches.

  Further, in addition to a thermoelectric material chip having a PN junction constituting this element, a dummy thermoelectric material chip that is not electrically connected is joined and arranged in the element.

Further, of the electrodes for forming a PN junction pair formed on the substrate, one having a plurality of thermoelectric material chips of the same type joined on one electrode.
That is, the mechanical strength of the thermoelectric conversion element can be increased by joining the electrically separated thermoelectric material chip to the substrate.

  In addition, since the same type of thermoelectric material chip is joined to one electrode for PN junction, the mechanical strength is increased, and even if one is damaged, it can function as an element.

  Alternatively, the thermoelectric conversion element of the present invention comprises two substrates on which electrodes are wired, and at least one or more pairs of chip-shaped P-type and N-type thermoelectric materials sandwiched therebetween and PN-joined via the electrode wiring. The cross-sectional shape of the thermoelectric material chip has a width that changes in a direction perpendicular to the substrate.

  Therefore, in the case where the Peltier effect is used, a place where Joule heat is generated by energization can be defined by the cross-sectional shape. Further, in this method of manufacturing a thermoelectric conversion element, a thermoelectric conversion element composed of thermoelectric material chips under several hundred grooves can be manufactured, and the yield can be improved.

  Alternatively, the thermoelectric conversion element of the present invention is composed of two substrates on which electrodes are wired, and at least one pair or more of chip-shaped P-type and N-type thermoelectric materials sandwiched therebetween and PN-joined via the electrode wiring. In a thermoelectric conversion element, a structure is provided on all or a part of the surface of at least one substrate in a portion where the thermoelectric material chip and the substrate are joined, in the vicinity thereof.

  That is, the structure near the bonding portion on the substrate prevents the flow of the bonding material such as solder at the time of bonding the substrate and the thermoelectric material, and also facilitates the positioning of the thermoelectric material on the substrate.

  Further, the size or shape of the structure provided on this substrate is different in at least one of the substrates where the P-type thermoelectric material chip and the N-type thermoelectric material chip are arranged.

  In other words, since the size and shape of the structure near the joint on one substrate are different between the portions where the P-type thermoelectric material chip and the N-type thermoelectric material chip are arranged, the type of the thermoelectric material is mistaken. It can be joined without any. In addition, when a P-type thermoelectric material chip and an N-type thermoelectric material chip are first bonded to separate substrates, and then a thermoelectric conversion element is manufactured by a step of performing PN junction with facing each other, positioning is performed at the first bonding. By reducing the size of the structure used, the positional accuracy of the joint can be increased, and by increasing the size of the structure used for positioning in the second joint (PN junction), it is possible to allow a margin for positioning, The flow of the bonding material can be prevented.

  Further, the size or shape of the structure provided on this substrate is different between the two substrates constituting the thermoelectric conversion element for the same thermoelectric material chip.

  That is, the structure provided on the substrate is the same thermoelectric material chip, and the two substrates constituting the thermoelectric conversion element are different in size or shape, so that the type of the thermoelectric material is wrong. It can be joined without. In addition, when a P-type thermoelectric material chip and an N-type thermoelectric material chip are first bonded to separate substrates, and then a thermoelectric conversion element is manufactured by a step of performing PN junction with facing each other, positioning is performed at the first bonding. By reducing the size of the structure used, the positional accuracy of the joint can be increased. By increasing the size of the structure used for positioning in the second joining (PN junction), it is possible to provide a margin for positioning and at the same time joining. Material flow can be prevented.

The material of the structure provided on the substrate was a polymer material.
That is, since the structure near the bonding portion on the substrate is made of a polymer material, the heat conduction is poor, so that the flow of heat from the high-temperature end to the low-temperature end of the thermoelectric conversion element can be suppressed, and the performance of the element decreases. Nothing.

The structure provided on the substrate was formed by curing a photosensitive resin material.
In other words, since the structure in the vicinity of the joint on the substrate is obtained by curing a photosensitive resin, it can be miniaturized by photolithography, and therefore is composed of several hundreds of thermoelectric material chips under the trench. In producing a thermoelectric conversion element, it works effectively as a structure.

At least one of the two substrates constituting the thermoelectric conversion element was made of silicon.
That is, since microfabrication can be performed by using silicon for the substrate, it is possible to manufacture a thermoelectric conversion element composed of thermoelectric material chips under several hundred holes. In addition, the thermal conductivity of silicon is not only higher than that of ceramics such as alumina, but also higher at lower temperatures than that of metals such as aluminum. As a result, the performance of the thermoelectric conversion element can be improved.

Further, the whole or a part of the surface of the silicon substrate constituting this element is covered with an insulating film.
That is, by providing an insulating layer on silicon of the substrate, electrical insulation between the substrate and the thermoelectric material chip can be completely completed.

Further, in the bonding of the thermoelectric conversion element on at least one substrate, the composition of the bonding material for bonding the thermoelectric material chip and the electrode formed on the substrate is different between different types of thermoelectric material chips. And
That is, after the P-type thermoelectric material chip and the N-type thermoelectric material chip are respectively bonded to different substrates, bonding can be easily performed in forming a PN junction pair.

Further, an electrode for forming a PN junction formed on the thermoelectric material chip and the substrate was joined via a protruding electrode.
That is, since the PN junction can be easily formed by the protruding electrodes, a method of manufacturing a thermoelectric conversion element made of a thermoelectric material chip having a size of several hundreds and a large size can be adopted.

  Further, a protruding electrode for joining the thermoelectric material chip and the electrode formed on the substrate is formed on the thermoelectric material chip.

That is, since the protruding electrodes are formed on the thermoelectric material, it can be easily aligned with the substrate for forming the PN junction. Thermoelectric conversion element can be easily manufactured.
Further, a protruding electrode having a solder bump structure, in which a protruding electrode for joining the thermoelectric material chip and an electrode formed on the substrate is formed on the thermoelectric material chip.

That is, since the protruding electrodes have a solder bump structure formed on the thermoelectric material, the solder melts at the time of joining, so that the height of the P-type thermoelectric material chip and that of the N-type thermoelectric material chip are different, Can be offset by soldering, and a thermoelectric conversion element can be easily manufactured.
The method for manufacturing a thermoelectric conversion element according to the present invention includes the following steps. Two sheets provided with predetermined electrode wiring for PN-joining a plate-like or rod-like P-type and N-type thermoelectric material (hereinafter, a plate-like or rod-like thermoelectric material is referred to as a wafer-like thermoelectric material or a thermoelectric material wafer) Each is separately bonded to a substrate.

Next, the bonded thermoelectric material wafers are cut and removed as necessary so that the electrodes to which the different types of thermoelectric material chips are to be bonded appear. At this time, a part of the substrate or the electrode wiring is also cut as necessary. By these steps, the substrate on which the P-type thermoelectric material chip is bonded to the predetermined electrode and the electrode to which the N-type thermoelectric material chip is to be bonded appears on the surface, and the N-type thermoelectric material chip is bonded to the predetermined electrode Two substrates are produced which are joined and have electrodes on the surface to which the P-type thermoelectric material chips are to be joined.
Next, with respect to these two substrates, the surfaces to which the thermoelectric material chips are bonded face each other, the mutual thermoelectric material chips and the substrate electrodes are aligned at predetermined positions, and the tips of the mutual thermoelectric material chips and the substrate To form a PN junction pair via an electrode made of metal or the like, thereby forming a thermoelectric conversion element.

In such a manufacturing method, the P-type and N-type thermoelectric material wafers are separately bonded to two substrates on which predetermined electrode wiring is formed in advance to form a PN junction, and then the bonded thermoelectric material is bonded. By cutting and removing a predetermined portion of the wafer, a thermoelectric material chip bonded to the substrate is obtained. At this time, electrodes to be joined to different types of thermoelectric material chips are made to appear.
The thermoelectric conversion element is manufactured by facing the substrate in which the P-type thermoelectric material chip thus manufactured is joined and the substrate in which the N-type thermoelectric material chip is joined, and joining them together at a predetermined position. can do.

  In addition, when bonding the thermoelectric material wafer and the substrate, a gap is provided between the thermoelectric material wafer and the substrate, and the gap is used in the next step of cutting and deleting unnecessary portions of the thermoelectric material. Cut and delete only the thermoelectric material wafer without damaging the electrodes or the electrodes, and create a substrate to which the thermoelectric material chips are joined.

  In such a manufacturing method, since there is a gap between the substrate and the bonded thermoelectric material wafer, when the predetermined part of the thermoelectric material is cut / deleted by the equipment used for cutting / deletion, the gap is used as a boundary. I can do it. Thus, unnecessary portions of the thermoelectric material can be cut or deleted without breaking or breaking the electrode wiring on the substrate.

  A step of performing predetermined electrode wiring on the substrate surface; and a step of forming a predetermined shape and arrangement pattern on at least one surface of the surface of the thermoelectric material wafer that is to be bonded to the substrate. And a step of forming a bump made of nickel or the like, and a step of joining a substrate and a thermoelectric material through the bump.

  Such a manufacturing method includes a step of forming an electrode for performing PN junction on a substrate, and forming a bump of solder, gold, silver, copper, nickel, or the like on at least one surface of the thermoelectric material wafer. The thermoelectric material can be miniaturized by the process of bonding the substrate and the thermoelectric material through the process, so that the thermoelectric conversion elements with the arrangement and the interval to become the thermoelectric material chips of the size of several hundreds of cavities are manufactured. Can be done.

Further, in the bonding between the thermoelectric material wafer and the substrate, a gap is provided between the bonded thermoelectric material wafer and the substrate, and the gap is formed by a bump.
In such a manufacturing method, since a gap is provided between the substrate and the thermoelectric material wafer by the bump formed on the surface of the thermoelectric material chip, the thermoelectric material can be cut without breaking or breaking the electrode wiring on the substrate. Unnecessary parts of material can be cut and deleted.

Further, in the bonding between the thermoelectric material wafer and the substrate, a gap is provided between the bonded thermoelectric material wafer and the substrate, and the gap is a method for manufacturing a thermoelectric conversion element formed by a structure provided on the substrate. .
In such a manufacturing method, a gap is formed between the bonded substrate and the thermoelectric material wafer by the structure provided on the substrate, so that the electrode wiring on the substrate is disconnected or damaged. Unnecessary portions of the thermoelectric material can be cut or deleted without the need.

Further, a thermoelectric conversion element formed by forming a bump on the surface of the thermoelectric material wafer bonded to the substrate opposite to the surface bonded to the substrate after bonding the thermoelectric material wafer to the substrate. Production method.
According to such a manufacturing method, since the bumps are formed on the surface of the thermoelectric material bonded to the substrate, the bumps can be formed more easily than when bumps are simultaneously formed on both surfaces of the thermoelectric material wafer.

  Further, before joining the thermoelectric material wafer and the substrate, at least one or all of the surfaces of the thermoelectric material wafer is subjected to a process in which a joint portion with the substrate or a portion near the joint portion is convex. The manufacturing method of the thermoelectric conversion element to be kept.

  According to such a manufacturing method, since all or part of the surface to be bonded of the thermoelectric material wafer used for bonding with the substrate is processed so that the bonding portion or the vicinity of the bonding portion is convex, the substrate After the bonding of the thermoelectric material wafer to the substrate, a gap can be formed between the substrate and the thermoelectric material wafer. In addition, the cross-sectional shape of the thermoelectric material chip can be changed in the height direction of the thermoelectric material chip depending on the width of the cut / deletion and the shape of the protrusion.

  Further, a method for manufacturing a thermoelectric conversion element including a step of grooving at least all or a part of at least one surface of the thermoelectric material wafer before joining the thermoelectric material wafer and the substrate.

  According to such a manufacturing method, the entire surface or at least one surface of the surface of the thermoelectric material wafer to be bonded to the substrate is subjected to grooving using physical or chemical means. A convex portion can be formed at or near the joint. With this projection, a gap can be provided between the bonded thermoelectric material wafer and the substrate. By using this gap, unnecessary portions of the thermoelectric material can be cut or deleted without breaking or breaking the electrode wiring on the substrate. In addition, the cross-sectional shape of the thermoelectric material chip can be changed in the height direction of the thermoelectric material chip depending on the width of the cut / deletion and the shape of the protrusion.

  In addition, at least one surface of the thermoelectric material wafer in which a bonding material for bonding to the substrate or a layer of a material for assisting bonding is formed on at least one surface before the bonding between the thermoelectric material wafer and the substrate. And a method for manufacturing a thermoelectric conversion element having a step of grooving all or part of the thermoelectric conversion element.

  According to such a manufacturing method, of the thermoelectric material wafer on which the bonding material layer or the layer for assisting bonding is provided, at least one of the surfaces to be bonded to the substrate is physically or physically provided on the entire surface or a part thereof. By performing grooving processing such as the groove 67 in FIG. 6B using chemical means, for example, a convex portion can be formed at the joint portion or in the vicinity of the joint portion. Since a gap can be provided between the wafer and the substrate, unnecessary portions of the thermoelectric material can be cut or deleted without breaking or breaking the electrode wiring on the substrate.

  In addition, by taking into account the width of the cut / deletion and the shape of the convex portion, the cross-sectional shape of the thermoelectric material chip of the completed thermoelectric conversion element in a plane perpendicular to the substrate is close to the substrate and the center of the thermoelectric material chip. You can change the width.

  In addition, before the first bonding between the thermoelectric material wafer and the substrate, a groove is formed in all or a part of at least one of the surfaces of the thermoelectric material wafer on which bumps for bonding to the substrate are formed. And a method for manufacturing a thermoelectric conversion element in which the grooving is performed between the bumps.

  According to such a manufacturing method, at least one of the surfaces of the thermoelectric material wafer on which the bumps are formed for bonding to the substrate is physically or chemically formed on at least one of the surfaces on which the bumps are formed. By performing grooving between the bumps by using a means, a convex portion can be formed at or near the bonding portion, so that a gap is formed between the bonded thermoelectric material wafer and the substrate. Since it can be provided, unnecessary portions of the thermoelectric material can be cut or deleted without breaking or breaking the electrode wiring on the substrate. Further, the cross-sectional shape of the thermoelectric material chip can be changed in the height direction of the thermoelectric material chip depending on the width of the cut / deletion and the shape of the protrusion.

  In addition, before the first bonding between the thermoelectric material wafer and the substrate, there is provided a step of grooving at least all or a part of at least one surface of the thermoelectric material wafer. Is different from the width of a portion to be cut / deleted in a step of cutting / removing an unnecessary portion of a thermoelectric material wafer, which is a post-process.

  According to such a manufacturing method, at least one of the surfaces of the thermoelectric material wafer to be bonded to the substrate is entirely or partially bonded to the groove 93 in FIG. By performing the grooving process as shown in FIGS. 94 and 94, a convex portion can be formed at or near the joint. With this projection, a gap can be provided between the bonded thermoelectric material wafer and the substrate. By using this gap, unnecessary portions of the thermoelectric material can be cut or deleted without breaking or breaking the electrode wiring on the substrate. In addition, by making the width of the cut / delete different from the width of the groove, the cross-sectional shape of the thermoelectric material chip can be changed in the height direction. Further, by increasing the width of the gap at the time of joining formed by grooving, the degree of freedom in positioning and accuracy of the blade used in the cutting process is increased, so that the workability is improved.

  As described above, according to the present invention, based on the positional relationship between the thermoelectric material chip and the PN junction electrode, the thermoelectric material wafer is joined to the PN junction electrode on the substrate, and then unnecessary portions of the thermoelectric material are cut. After removal, a thermoelectric material chip bonded on the substrate is manufactured, and then the substrate on which the heterogeneous thermoelectric material chips are bonded faces each other, and the tip of the thermoelectric material chip is bonded to the PN junction electrode on the substrate. By doing so, a PN junction is formed, so that there is an effect that a thermoelectric conversion element having a small thermoelectric material chip size and a high density of thermoelectric material chips per unit area can be manufactured.

  Also, from the arrangement of the thermoelectric material chips, and the position and arrangement relationship between the thermoelectric material chips and the PN junction electrodes, it is possible to adopt a method in which the thermoelectric material is formed into chips after bonding to the substrate. Eliminates the handling of difficult thermoelectric material chips. Therefore, it is possible to provide a small-sized thermoelectric conversion element having a small thermoelectric material chip size and a high density of thermoelectric material chips per unit area.

  In addition, since a dummy thermoelectric material chip is fixed between the two substrates at a portion corresponding to the outer peripheral portion of the thermoelectric conversion element which is easily subjected to mechanical shock from the outside, the mechanical strength of the element is increased and the reliability is improved. It has the effect of increasing.

  In addition, by changing the cross-sectional shape of the thermoelectric material chip in the direction perpendicular to the substrate, when utilizing the Peltier effect of the thermoelectric conversion element, it is possible to limit the location where Joule heat is generated by energization, so that the cooling efficiency on the cooling surface is reduced. Has the effect of increasing. In addition, by changing the cross-sectional shape, it is possible to increase the alignment accuracy in the assembly process, so that it is possible to manufacture thermoelectric conversion elements composed of thermoelectric material chips under several hundreds of trenches, and to improve the yield. There is an effect that it can be achieved.

  In addition, since the structure is provided near (around) the position where the thermoelectric material is to be joined on the substrate, there is an effect that the alignment accuracy at the time of joining can be improved and the flow of the joining material can be prevented. is there.

  In addition, since silicon is used as a substrate material, surface processing by photolithography can be easily performed, and there is an effect that a small thermoelectric conversion element can be easily manufactured. In addition, since the thermal conductivity of silicon is very high, especially at low temperatures, it is higher than that of metals such as aluminum, so that the efficiency of absorbing and dissipating heat in the manufactured thermoelectric conversion element increases, so that the performance as a thermoelectric conversion element increases. This has the effect.

  Also, in a method of joining different kinds of thermoelectric material chips to different substrates, facing each other, and joining the thermoelectric material chips to the substrate, a joining material used for the first joining and a joining material used for the second time By changing the composition of the material, the second bonding temperature can be lower than the first bonding temperature, so that the thermoelectric conversion element can be manufactured without damaging the first bonding portion.

  In addition, by performing bonding via a protruding electrode such as a bump, in addition to the effect of serving as a bonding material in bonding the thermoelectric material wafer and the substrate, in addition to the cutting / deleting process after bonding, This has the effect of also providing a gap for preventing damage to the electrode wiring.

  Furthermore, by providing a protruding electrode made of nickel or the like on the thermoelectric material side, it is possible to suppress the diffusion reaction between the bonding material such as solder and the thermoelectric material, thereby improving the reliability of the produced thermoelectric conversion element. be able to. This effect is remarkable in the case of joining of a Bi-Te-based material by a solder, which has a remarkable diffusion reaction with the solder.

  In addition, since a method of forming the thermoelectric material into chips after bonding to the substrate can be adopted, the thermoelectric material chip, which is difficult to handle when the size of the thermoelectric material chip is small, is not required. It is possible to provide a small-sized thermoelectric conversion element having a small size and a high density of thermoelectric material chips per unit area.

  In addition, since a gap is provided between the bonded thermoelectric material wafer and the substrate, the substrate and the electrode wiring provided on the substrate may be damaged by inserting a cutting edge such as a cutting tool used for cutting / deleting into the gap. There is an effect that a thermoelectric material chip bonded to a substrate can be manufactured without giving.

  In addition, a gap can be formed between the bonded thermoelectric material wafer and the substrate by using the structure provided on the substrate, so that a cutting edge such as a cutting tool used for cutting and deleting is set in the gap. This has an effect that a thermoelectric material chip bonded to the substrate can be manufactured without damaging the substrate and the electrode wiring provided on the substrate. Further, the structure itself may serve as a gap.

  Also, there is no need to provide a bonding layer on both sides of the thermoelectric material wafer in advance, and the first bonding is performed using the bonding layer formed only on one side, and thereafter, a method such as printing, cutting, If a chip is formed after the chip is removed, the bonding material layer can be formed on the other surface by a simple method such as a stamping method at the tip of the thermoelectric material chip.

  In addition, by forming at least a portion of the thermoelectric material wafer to be initially bonded to a portion to be bonded to the electrode on the substrate and the vicinity thereof, a gap is formed between the bonded thermoelectric material wafer and the substrate. The thermoelectric material chip bonded to the substrate can be easily formed without damaging the substrate or the electrode wiring provided on the substrate by placing the cutting edge of the cutting tool or the like used for cutting or deleting in this gap. There is an effect that it can be manufactured. In addition, about the method of forming a convex part, in addition to the physical method by a cutting tool etc., the chemical method of etching, etc., when a thermoelectric material is a sintered body, it becomes a desired convex shape at the time of sintering. There is also a method of manufacturing using such a mold.

In addition, by forming a groove in a thermoelectric material wafer having a bonding material layer for bonding to the substrate or a layer for assisting bonding formed on the surface, a convex portion is formed in a portion to be bonded to the substrate and in the vicinity thereof. Form. As a result, the projection becomes a protruding electrode corresponding to the bump, and the layer formed at the tip becomes a layer directly involved in bonding.
Therefore, in the method for manufacturing a thermoelectric conversion element according to claim 19, a patterned bonding layer is formed, and a gap can be formed between the bonded thermoelectric material wafer and the substrate. By placing a cutting edge such as a cutting tool used for removal in this gap, the thermoelectric material chip bonded to the substrate can be easily manufactured without damaging the substrate or the electrode wiring provided on the substrate. is there.

  In addition, by inserting a groove between the bumps of the thermoelectric material wafer having bumps formed on the surface for bonding to the substrate, the bumps are positioned above the convex portions. Therefore, if the gap required for cutting / deletion cannot be created between the substrate and the thermoelectric material after bonding due to the small size of the bumps, the protrusions and bumps are used between the bonded thermoelectric material wafer and the substrate. A sufficiently wide gap can be created. Thereby, the cutting edge of a cutting tool or the like used for cutting / deletion can be set in this gap, and the thermoelectric material chip bonded to the substrate can be easily manufactured without damaging the substrate or the electrode wiring provided on the substrate. This has the effect.

  In addition, by changing the width of the groove and the width of cutting / deleting before the first bonding, the thermoelectric conversion element where the cross-sectional shape of the thermoelectric material chip in the direction perpendicular to the substrate differs between the vicinity of the substrate and the center part Since it can be manufactured, there is an effect that a thermoelectric conversion element having excellent performance can be provided.

  Further, the thermoelectric conversion element having a PN junction pair of a large number of small and thin thermoelectric material chips produced in this way has a great effect in power generation with a small temperature difference. In the first embodiment, an example in which an electronic wristwatch is driven by using thermoelectric conversion elements having a number of PN junction pairs capable of outputting an output of about 1 V or more has been described. For example, if the device is driven at a lower voltage, the number of elements can be significantly reduced, and thus the application of the thermoelectric conversion element to not only electronic wrist watches but also many portable electronic devices can be achieved. Also, the use of a small thermoelectric conversion element produced by the present invention as a cooling element has a great effect.

  For example, if the current density flowing per thermoelectric material chip is constant in order to make the cooling performance the same, the cross-sectional area of the thermoelectric material chip is small, and many thermoelectric material chips can be arranged in series. The cooling capacity can be increased by increasing the voltage. For example, the cooling performance is determined by the power input to the thermoelectric conversion element. In the conventional thermoelectric conversion element, the power supply is low voltage and large current because the cross-sectional area of the thermoelectric material chip is large.

  On the other hand, in the thermoelectric conversion element of the present invention, the cross-sectional area of the thermoelectric material chip can be reduced, so that power can be supplied at 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. Further, since the electric wiring can be thinned, a multi-stage element called a so-called cascade type can be easily manufactured, and an extremely low temperature can be achieved.

  In the embodiment, the size of the thermoelectric material chip is set to 500 μm or less. However, it is needless to say that the present invention can be applied to a size of several hundred μm, which is a general size, to a millimeter order. Nor. Furthermore, in the embodiments, the production of individual thermoelectric conversion elements has been described. However, by using a large-sized substrate or a thermoelectric material wafer, a plurality of elements can be produced together, so that a small thermoelectric conversion element can be manufactured. In the case of manufacturing, the present invention has a great effect also in terms of cost.

  Hereinafter, the present invention will be described in detail based on embodiments with reference to the drawings.

  FIG. 1 is a diagram showing the appearance of a thermoelectric conversion element according to the present invention. The basic configuration of the thermoelectric conversion element 11 shown in FIG. 1 includes a substrate 12, a P-type thermoelectric material chip 13, an N-type thermoelectric material chip 14, and a PN junction electrode 15. FIGS. 2A and 2B are cross-sectional views of a main part taken along lines A-A 'and B-B' shown in the diagram showing the appearance of the thermoelectric conversion element shown in FIG. 1, respectively.

The cross-sectional view shown in FIG. 2 shows the structure 23 of the present invention formed on the substrate 21 around the joint in addition to the main part of the thermoelectric conversion element. In FIG. 2A, which is a cross-sectional view of FIG. 1A-A ', while P-type thermoelectric material chips and N-type thermoelectric material chips appear alternately, FIG. 2B, which is a cross-sectional view of FIG. In b), only a P-type thermoelectric material chip or an N-type thermoelectric material chip appears. FIG. 3 is a perspective view of the thermoelectric conversion element of FIG. 1 from above showing a positional relationship between an electrode wiring pattern on a substrate and a thermoelectric material chip. (FIGS. 1, 2 and 3 show the outlines and concepts, and the dimensions and the number of thermoelectric material chips are determined according to the purpose.)
In FIG. 3, among the lines representing the electrode wirings, the solid lines indicate the electrode wiring patterns 32 on the upper substrate, and the dotted lines indicate the electrode wiring patterns 33 on the lower substrate. Note that the expressions of the upper substrate and the lower substrate here are for convenience of explanation, and it goes without saying that in a thermoelectric conversion element, both substrates can be up and down. The squares with two types of diagonal lines represent a P-type thermoelectric material chip 34 and an N-type thermoelectric material chip 35, respectively.

Embodiments relating to the thermoelectric conversion element of the present invention having such a structure and a method of manufacturing the same will be described for a small thermoelectric conversion element having a thermoelectric material chip size of 100 μm.
As the thermoelectric material, a sintered body of a Bi-Te-based material, which is a material having excellent performance near room temperature, was used. The main characteristics of this thermoelectric material are that the P-type has a Seebeck coefficient of 205 μV / deg, a specific resistance of 0.95 mΩcm, and a thermal conductivity of 1.5 W / m · deg, and the N-type has a Seebeck coefficient of 170 μV / deg and a specific resistance of 0. The heat conductivity was 75 mΩcm and the thermal conductivity was 1.5 W / m · deg.

  As the substrate material, a 300 μm thick silicon wafer electrically insulated by thermally oxidizing the surface was used. As for the size of the element, the height of the thermoelectric material chip was 500 μm, the shape of the cross section parallel to the substrate of the thermoelectric material chip was a square, and the length of each side was 100 μm as described above. The distance between the thermoelectric material chips is 200 μm (300 μm at the center-to-center distance), and the distance between the nearest different types of thermoelectric material chips is 70 μm (300 / √2 = about 210 μm at the center-to-center distance). Are 125 pairs in series.

  FIG. 4 is a diagram illustrating an outline of a process for manufacturing the thermoelectric conversion element of the present embodiment. As shown in FIG. 4, this manufacturing method is roughly divided into five steps. This will be described step by step.

  In the bump forming step (a), a 50 μm-thick photoresist is applied to both surfaces of each of the P-type and N-type thermoelectric material wafers 40 made of a 500 μm-thick Bi—Te-based sintered body. By exposing and developing the photoresist, a resist layer having a circular shape with an opening diameter of 90 μm and having openings such that the arrangement is a desired pattern is formed. Here, the desired pattern is determined based on the dimensions described above so that the thermoelectric material chips are arranged in FIG. Next, after washing the opening with an acid or the like, nickel plating of 40 μm is first applied by electroplating to form a so-called nickel bump.

  Next, solder plating was similarly performed on nickel by electroplating to form a solder layer of 30 μm. Here, the solder plating was performed so that the composition ratio of tin and lead was 6: 4. Next, after removing the photoresist, a rosin-based flux is applied to the solder plating layer, and a reflow process is performed at 230 ° C., whereby spherical solder bumps 41 having a diameter of about 100 μm are formed on both surfaces of the thermoelectric material wafer 40. I was able to.

  In the electrode wiring step (b), the surface of a 300 μm thick silicon wafer substrate 42 provided with a 0.5 μm oxide layer on the surface is thermally oxidized, and the surface of the silicon wafer substrate 42 is subjected to sputtering in the order of chromium, nickel, and gold. Films were formed with a thickness of 0.1 μm, 3 μm, and 1 μm. Next, the electrode wiring 43 was formed on the upper and lower substrates by photolithography so as to have the electrode wiring pattern of FIG. Further, two types of donut-shaped structures 44 were formed by a photolithography method using a polyimide-based photoresist around a portion where the P-type thermoelectric material and the N-type thermoelectric material were joined by solder bumps.

  The size of the structure body 44 made of the polyimide-based photoresist has a donut shape at a position where the P-type thermoelectric material chip is arranged on one of the two substrates constituting the thermoelectric conversion element. The inner diameter is 120 μm, the outer diameter is 150 μm, the height is 30 μm, the inner diameter is 140 μm, the outer diameter is 170 μm, and the height is 30 μm at the position where the N-type thermoelectric material chip is arranged. The inner diameter was 140 µm, the outer diameter was 170 µm, and the height was 30 µm. The inner diameter was 120 µm, the outer diameter was 150 µm, and the height was 30 µm at the position where the N-type thermoelectric material chip was to be arranged.

  In the joining step (c), the thermoelectric material wafer 40 with the solder bumps 41 produced in the bump forming step (a), the electrode wiring 43 produced in the electrode wiring step (b), and the donut-shaped structure 44 near the joint are formed. After performing predetermined alignment with the substrate 42 facing the substrate 42, the solder was melted, and the thermoelectric material wafer 40 and the substrate 42 were joined. In joining the P-type thermoelectric material wafer and the substrate, the solder bumps formed on the surface of the P-type thermoelectric material wafer are replaced with the smaller donut formed on the substrate having an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of 30 μm. The thermoelectric material wafer 40 and the substrate 42 were aligned by being placed inside the mold structure.

  Similarly, in bonding the N-type thermoelectric material wafer to the substrate, the solder bump formed on the surface of the N-type thermoelectric material wafer is replaced with a small donut having an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of 30 μm formed on the substrate. The thermoelectric material wafer 40 and the substrate 42 were aligned by being placed inside the mold structure. The reason why the smaller one of the two types of donut-shaped structures formed on the substrate was used for bonding the thermoelectric material wafer 40 and the substrate 42 was that the bonding position was definitely determined. Is to enhance mutual alignment accuracy.

  In the cutting / deleting step (d), the thermoelectric material wafer 40 bonded to the substrate 42 is cut / deleted from the thermoelectric material wafer to form a thermoelectric material chip 45 bonded to the substrate 42. At this time, a part of the substrate 42 or the electrode wiring 43 may be cut or deleted at the same time as necessary. In this embodiment, the cutting / deleting step (d) is performed using a dicing saw used for cutting a silicon semiconductor or the like. The blade used for cutting / deleting had a thickness of 200 μm. The thickness of this blade is such that the side length of the thermoelectric material chip 45 having a square shape in this embodiment is 100 μm, the center-to-center distance between the closest similar thermoelectric material chips is 300 μm, and different types of thermoelectric material chips are shown in FIG. It was selected because it is joined in a positional relationship.

  Unnecessary portions of the thermoelectric material are cut / deleted at the center between the solder bumps 41 and at the same time on the substrate by utilizing the gap between the thermoelectric material wafer 40 and the substrate 42 made of nickel bumps having a height of 40 μm. This was performed by adjusting the height of the blade so that the electrode wiring 43 was not damaged. The substrate 42 to which substantially 125 thermoelectric material chips 45 were bonded for each type of thermoelectric material was manufactured by cutting and removing the thermoelectric material of each type vertically and horizontally.

  Here, the substrate 42 to which substantially 125 thermoelectric material chips 45 are bonded is the arrangement and configuration of the thermoelectric material chips in FIG. 3. A rectangular thermoelectric material wafer is used, and 11 rows of solder bumps are vertically arranged. X When formed as 12 rows in the horizontal direction (total of 132 rows), 125 rows substantially contribute to the PN junction due to the arrangement. In this case, some unnecessary peripheral chips will be deleted in the cutting / deleting process without any means for joining, so that there is no problem. By bonding and leaving, it is possible to enhance the mechanical reinforcement and electrical reliability of the thermoelectric conversion element to be manufactured, so that it can be bonded to the substrate by some means and left. Good.

  In this case, if the purpose is to increase the strength of the thermoelectric conversion element to be manufactured, a dummy bonding pad that is electrically isolated in advance on the substrate is manufactured at the time of forming the electrode wiring, and the dummy bonding pad is formed with other bumps. Similarly, the thermoelectric conversion element can be manufactured without any trouble in the process by joining. Also, by bonding the bumps of the unnecessary chip portions to the substrate on which pads arranged in advance so as to short-circuit with the nearby electrodes are formed, the chip is left, and the thermoelectric material chip at the outermost periphery is mechanically reinforced. And the reliability of electrical connection can be improved.

  In the assembling step (e), the two substrates 42 to which the different types of thermoelectric material chips 45 are joined are opposed to each other, and the solder bumps 41 formed at the tips of the respective chips are formed on the substrates. The electrode wiring 43 is aligned with the position to be joined, and heated while applying pressure, thereby melting the solder, joining the thermoelectric material chip 45 and the electrode wiring 43 on the substrate 42, and A thermoelectric conversion element having a PN junction was completed.

  It should be noted that the alignment at the time of joining is performed by leaving the structure 44 formed on the substrate of the other type to which the solder bump 41 formed at the tip of each type of thermoelectric material chip 45 is to be joined. It was carried out by placing the inside of a larger donut-shaped structure (inner diameter 140 μm, outer diameter 170 μm, height 30 μm). The reason why the donut-shaped structure was made larger in this alignment is to facilitate the alignment between the thermoelectric material chip and the substrate electrode and to suppress the flow of the solder. These effects were sufficiently obtained in combination with the small donut-shaped structure in the step (c).

  The final external dimensions of the thermoelectric conversion element manufactured in this manner are about 1.2 mm in thickness (the thickness configuration is such that the thickness of the thermoelectric material chip is 0.5 mm and the thickness of the upper and lower substrates is 0.1 mm each). 3 mm, the height of the joining material and the height of the nickel bump at the upper and lower joints are each 0.05 mm), and the size is 4 mm × 4 mm, which is the size of the lower substrate on which the input / output electrodes are provided. The internal resistance was 120Ω.

  The size of the thermoelectric conversion element of this embodiment having the position and arrangement relationship between the thermoelectric material chip and the PN junction electrode shown in FIG. 3 manufactured by this manufacturing method is the same as that of the conventional manufacturing method. After that, the size cannot be made by a method of forming a thermoelectric conversion element by sandwiching it between upper and lower substrates.

A lead wire was connected to the input / output electrode of such a thermoelectric conversion element, and the respective characteristics were examined. The following results were obtained.
The power generation performance based on the Seebeck effect is as follows. The release voltage at a temperature difference of 2 ° C. between the substrates is 90 mV. When a load resistance of 1 KΩ is externally applied and a temperature difference of 2 ° C. is applied between the substrates, an output of 80 mV-70 μA is obtained. was gotten. Moreover, when the 16 thermoelectric conversion elements of the 125 pairs of PN junctions were connected in series and carried in a quartz oscillator type electronic wristwatch, the watch could be driven at a room temperature of 20 ° C.

  Regarding the performance as a cooling / heating element based on the Peltier effect, when a heat sink made of aluminum was adhered to a substrate on the heating side with a silicone adhesive having a high thermal conductivity and a voltage of 6 V was applied between input electrodes, about 50 mA was obtained. This current flows, and on the surface of the substrate on the heat absorption side, a phenomenon occurs in which the moisture in the air instantaneously freezes, which proves that the performance of the thermoelectric conversion element as a Peltier element is extremely excellent.

  FIG. 5 is a perspective view of the thermoelectric conversion element according to the second embodiment, which is seen through from the upper substrate, for explaining the outline of the arrangement of the electrode wiring and the thermoelectric material chip on the substrate. In FIG. 5, among the lines representing the electrode wirings, the solid lines indicate the electrode wiring patterns 50 on the upper substrate, and the dotted lines indicate the electrode wiring patterns 51 on the lower substrate. Note that the expressions of the upper substrate and the lower substrate here are for convenience of explanation, and it goes without saying that in a thermoelectric conversion element, both substrates can be up and down. Also, squares with two types of oblique lines represent a P-type electric material chip 52 and an N-type thermoelectric material chip 53, respectively. Further, a thermoelectric material chip (hereinafter, referred to as a dummy chip) which is not related to the PN junction present on the outer periphery of the thermoelectric conversion element is joined and fixed to the upper substrate and the lower substrate by the upper substrate dummy electrode 54 and the lower substrate dummy electrode 55. Have been.

In FIG. 5, the dummy chip is bonded to the dummy electrode on one substrate, and is bonded on the electrode performing the PN junction on the other substrate. However, the dummy chip may be provided on both substrates.
In any case, the dummy chip serves to mechanically reinforce the thermoelectric conversion element composed of the small thermoelectric material chip manufactured in this embodiment. As shown in FIG. 5, the arrangement of the thermoelectric material chips in the thermoelectric conversion element of the present embodiment is such that when a certain row is viewed in the X direction, only the P-type thermoelectric material chips or the N-type thermoelectric material chips form a row. The rows of the P-type thermoelectric material chips and the rows of the N-type thermoelectric material chips are alternately arranged. On the other hand, in the Y direction, when a certain row is viewed, P-type thermoelectric material chips and N-type thermoelectric material chips are arranged side by side.

  In the present embodiment, the thermoelectric conversion element having this structure and the arrangement of the thermoelectric material chips has a size of 500 μm, a height of 500 μm, and a center-to-center distance of the closest thermoelectric material chip in a cross section parallel to the substrate. The thermoelectric material chips (including dummy chips) having a thickness of 1000 μm and including the P-type and the N-type were 64 in total.

  As the thermoelectric material, a sintered body of a Bi-Te-based material, which is a material having excellent performance near room temperature as in Example 1, was used. The main characteristics of this thermoelectric material are that the P-type has a Seebeck coefficient of 205 μV / deg, a specific resistance of 0.95 mΩcm, and a thermal conductivity of 1.5 W / m · deg, and the N-type has a Seebeck coefficient of 170 μV / deg and a specific resistance of 0. The heat conductivity was 75 mΩcm and the thermal conductivity was 1.5 W / m · deg. As a substrate material, alumina having a thermal conductivity of 20 W / m · deg was used.

FIG. 6 is a diagram showing an outline of a process for manufacturing the thermoelectric conversion element. Hereinafter, each step will be described with reference to FIG.
In the bonding layer forming step (a), nickel plating is performed on both surfaces of the surface of the thermoelectric material wafer 60 having a thickness of 500 μm to be bonded to the substrate by wet plating to form a nickel layer 61 having a thickness of 10 μm. . Next, one surface on which the nickel layer is formed is masked, and the other surface is subjected to solder plating having a composition of tin: lead = 1: 9 by wet plating to form a solder layer 62 having a thickness of 30 μm. .

  Next, the plating mask is removed, the solder layer 62 having a composition of tin: lead = 1: 9 is masked, and a tin: lead = 6: 4 composition is formed on the other nickel layer 61 by a wet plating method. By applying solder plating, a solder layer 63 having a thickness of 30 μm is formed, and by removing the plating mask, a solder layer 62 having a composition of tin: lead = 1: 9 is provided on one surface, and the solder layer 63 is provided on the other surface. A thermoelectric material wafer having a solder layer 63 having a composition of tin: lead = 6: 4 is prepared. Next, a rosin-based flux was applied to the solder layers 62 and 63 on both sides, and the solder was reflowed at 350 ° C. to homogenize the solder layer and clean the surface. Note that the reflow treatment may be performed after the grooving step, which is a subsequent step, because of the steps.

In the grooving step (b), a dicing saw was used, but with a blade having a blade width of 1.5 mm, the solder layer 62 having a composition of tin: lead = 1: 9 was vertically and horizontally extended from the surface of the nickel layer 61 to a depth of 90 μm. Grooves are made. At this time, the spacing between the grooves of the blade was 2 mm, that is, the interval between the convex portions formed between the grooves was 0.5 mm, which is the size of the thermoelectric material chip.
Here, the reason why the depth of the groove is set to 90 μm from the surface layer of the solder is the depth of the groove for preventing the adjacent convex portions from being short-circuited in the bonding in the later step. It also serves as a gap between the thermoelectric material wafer and the substrate, which is required for chipping by cutting / deleting in a later step.

  In the electrode wiring step (c), the copper plate of the 0.5 mm-thick alumina substrate 64 on which the 0.1 mm-thick copper plate is bonded is subjected to photo-etching to form electrodes of the patterns of the upper substrate and the lower substrate shown in FIG. The wiring 65 was processed.

  In the bonding step (d), the protrusion 68 of the thermoelectric material wafer 60 having the protrusion formed by grooving is aligned with the electrode wiring 65 on the substrate, and then the composition of tin: lead of the protrusion is 1: 9. Was melted, and the electrode wiring 62 and the thermoelectric material wafer 60 were joined. The joining temperature at this time was 340 ° C.

  In the cutting step (e), the cutting in the X direction shown in FIG. 5 is performed with a blade having a blade width of 1.5 mm using a dicing saw, and the cutting in the Y direction is performed with a blade width of 0.5 mm. In order to cut / delete the electrode wiring 65 on the substrate 64 without damaging it, the unnecessary part is cut / deleted so that the cutting edge comes to the groove (recess) 67 formed in the grooving step. A thermoelectric material chip 66 was manufactured.

  In the assembling step (f), two substrates 64 to which different types of thermoelectric material chips 66 are joined are faced to each other, and a tin: lead = 6: 4 composition formed at the tip of each chip is formed. The solder layer 63 and the electrode wiring 65 formed on the substrate 64 are aligned with the position to be joined, and are heated while applying pressure to melt the solder, and the thermoelectric material chip 66 and the electrode wiring 65 on the substrate 64 are melted. And a thermoelectric conversion element having a PN junction on the upper and lower substrates was completed. The temperature at the time of joining was 230 ° C., which is a temperature at which the previously joined solder having a composition of tin: lead = 1: 9 does not melt. For this reason, the assembling process could be performed without causing the thermoelectric material chip to fall down or shift without providing a structure around the joint.

  The thermoelectric conversion element of the present embodiment also employs essentially the same manufacturing method as the thermoelectric conversion element described in Example 1, but when the thermoelectric material chip is extremely small, the thermoelectric conversion element according to Example 1 is used. Although the position and arrangement of the thermoelectric material chips and the arrangement of the PN junction electrodes are preferable, in order to increase the density of the thermoelectric material chips in the thermoelectric conversion element, the position and arrangement of the thermoelectric material chips and the arrangement of the PN junction electrodes in this embodiment are preferred. preferable. Further, in order to suppress the amount of the thermoelectric material to be removed by cutting / deleting, the thermoelectric conversion element according to the present embodiment and the manufacturing method thereof are preferable.

  The final external dimensions of the thermoelectric conversion element manufactured in this manner are about 1.5 mm in thickness, and the size is 9 mm × 8 mm, which is the size of the lower substrate on which the input / output electrodes are provided. Had an internal resistance of 1Ω. A lead wire was connected to the input electrode of such a thermoelectric conversion element, and the performance as a cooling / heating element based on the Peltier effect was examined. When a heat sink made of aluminum is adhered to the substrate on the heat generating side with a silicone adhesive having high thermal conductivity and a voltage of 1 V is applied between input electrodes, a current of about 1 A flows, and rapid cooling occurs on the heat absorbing substrate side. Was. The ratio of the amount of heat absorbed to the input power, the so-called COP (coefficient of performance), was 0.55 when the temperature difference was 20 ° C., demonstrating that the thermoelectric conversion element had excellent performance.

  In the thermoelectric conversion element having the same electrode wiring structure as in Example 1, the production of a small thermoelectric conversion element having a thermoelectric material chip size of 50 μm will be described.

  As the thermoelectric material, a sintered body of a Bi-Te-based material, which is a material having excellent performance near room temperature as in Example 1, was used. The main characteristics of this thermoelectric material are that the P-type has a Seebeck coefficient of 205 μV / deg, a specific resistance of 0.95 mΩcm, and a thermal conductivity of 1.5 W / m · deg, and the N-type has a Seebeck coefficient of 170 μV / deg and a specific resistance of 0. The heat conductivity was 75 mΩcm and the thermal conductivity was 1.5 W / m · deg.

  As the substrate material, a 300 μm thick silicon wafer electrically insulated by thermally oxidizing the surface was used. As for the size of the element, the height of the thermoelectric material chip was 500 μm, the shape of the cross section parallel to the substrate of the thermoelectric material chip was a square, and the length of one side was 50 μm as described above. The distance between the thermoelectric material chips is 100 μm (150 μm at the center-to-center distance), and the distance between the nearest different types of thermoelectric material chips is 35 μm (150 / √2 = about 110 μm at the center-to-center distance). Are 51 pairs in series.

  FIG. 7 is a diagram illustrating an outline of a process for manufacturing the thermoelectric conversion element according to the present embodiment. As shown in FIG. 7, this manufacturing method is roughly divided into five steps. This will be described step by step.

  In the bump forming step (a), a photoresist having a thickness of 20 μm is applied to both surfaces of each of the P-type and N-type thermoelectric material wafers 70 made of a 500-μm-thick Bi—Te-based sintered body. By exposing and developing the photoresist, a resist pattern is formed so that the opening diameter is 45 μm and the arrangement is a desired pattern. Here, the desired pattern is determined based on the dimensions described above so that the thermoelectric material chips are arranged in FIG. Next, after washing the opening with an acid or the like, nickel plating of 20 μm is first applied by electroplating to form a so-called nickel bump.

  Next, solder plating was similarly performed on nickel by electroplating to form a solder layer of 30 μm. Here, the solder plating was performed so that the ratio of tin to lead was 6: 4. Next, after the photoresist is removed, a rosin-based flux is applied to the solder plating layer, and reflow treatment is performed at 230 ° C., so that spherical solder bumps 71 having a diameter of about 50 μm are formed on both surfaces of the thermoelectric material wafer 70. I was able to.

  In the electrode wiring step (b), the surface of a silicon wafer substrate 72 having a thickness of 300 μm and having a 0.5 μm oxide layer formed thereon is thermally oxidized, and the surface of the silicon wafer substrate 72 is subjected to sputtering in the order of chromium, nickel, and gold from the substrate side. Films were formed with a thickness of 0.1 μm, 2 μm, and 1 μm. Next, the electrode wiring 73 was formed on the upper and lower substrates by photolithography so as to have the electrode wiring pattern of FIG. Furthermore, a thick film photoresist was used around a portion where the P-type thermoelectric material and the N-type thermoelectric material were joined by the solder bumps, and two types of structures 74 were formed by removing the joint in a circular shape by photolithography.

  The shape and size of the structure 74 composed of the thick-film photoresist are circular in a position where the P-type thermoelectric material chip is arranged on one of the two substrates constituting the thermoelectric conversion element. The size of the portion to be removed was 60 μm in diameter, the diameter was 70 μm at the position where the N-type thermoelectric material chip was arranged, and the other portion was covered with a 40 μm-thick resist. On the other substrate, a structure having a diameter of 70 μm at the position where the P-type thermoelectric material chip is arranged, a diameter of 60 μm at the position where the N-type thermoelectric material chip is arranged, and covering the other parts with a resist having a thickness of 40 μm is formed. did.

  Here, the reason why the thickness of the resist is set to 40 μm is that in the next step (c) of joining the structure thus formed to the thermoelectric material wafer 70 and the substrate 72 and in the next step (d) of cutting and deleting the thermoelectric material wafer 70. This is for use as a gap. In the first embodiment, the gap is formed by the nickel bump. In the fourth embodiment, the gap between the thermoelectric material wafer 70 and the substrate 72 required in the cutting / deleting step (d) is 30 μm or more. On the other hand, when the bumps 71 are formed on the thermoelectric material wafer 70 in the previous step, it is difficult to make the height of the nickel bumps forming the gap 20 μm or more due to limitations of the photolithography technology and the plating technology.

  In the bonding step (c), the thermoelectric material wafer 70 with the solder bumps 71 manufactured in the bump formation step (a), the electrode wiring 73 manufactured in the electrode wiring step (b), and the substrate on which the structure 74 near the bonding part is formed After performing predetermined alignment with the substrate 72, the solder is melted, and the thermoelectric material wafer 70 and the substrate 72 are joined. In the bonding between the P-type thermoelectric material wafer and the substrate, the solder bumps formed on the surface of the P-type thermoelectric material wafer are placed inside the bonding openings of the structure 74 having a diameter of 60 μm formed on the substrate. Thus, the thermoelectric material wafer 70 and the substrate 72 were aligned.

  Similarly, in the bonding between the N-type thermoelectric material wafer and the substrate, the solder bumps formed on the surface of the N-type thermoelectric material wafer are connected to the inside of the bonding opening of the structure 74 having a diameter of 60 μm formed on the substrate. Then, the positioning of the thermoelectric material wafer 70 and the substrate 72 was performed. The reason for using the smaller joining opening of the joining openings of the two structures 74 formed on the substrate for joining the thermoelectric material wafer 70 and the substrate 72 here is to make sure that the joining position is correct. And increase the mutual alignment accuracy.

In the cutting / deleting step (d), the thermoelectric material wafer 70 bonded to the substrate 72 is cut and deleted from the thermoelectric material wafer to form a thermoelectric material chip 75 bonded to the substrate 72.
At this time, if necessary, a part of the substrate 72 may be cut or deleted at the same time. In this embodiment, the cutting / deleting step (d) is performed using a dicing saw used for cutting a silicon semiconductor or the like. The blade used for cutting / deleting had a thickness of 100 μm. The thickness of the blade is such that the side of the thermoelectric material chip 75 having a square shape in this embodiment has a side length of 50 μm, the center-to-center distance of the nearest similar thermoelectric material chip is 100 μm, and the thermoelectric material chips of different types are shown in FIG. It was selected because it was joined in the positional relationship of

  Cutting and removing unnecessary portions of the thermoelectric material are performed at the center between the solder bumps 71 and at the same time, the gap between the thermoelectric material wafer 70 and the substrate 72 made of the structure 74 having a height of 40 μm is used. This was performed by adjusting the height of the blade so as not to damage the upper electrode wiring 73. A substrate 72 to which substantially 51 thermoelectric material chips 75 were bonded for each type of thermoelectric material was manufactured by cutting and removing the thermoelectric material of each type vertically and horizontally.

  Here, the substrate 72 to which substantially 51 thermoelectric material chips 75 are bonded is the arrangement and configuration of the thermoelectric material chips in FIG. 3. A rectangular thermoelectric material wafer is used, and solder bumps are arranged in seven rows in the vertical direction. X When formed as eight rows in the horizontal direction (total of 56 rows), 51 rows are substantially involved in the PN junction due to the arrangement. In this case, some unnecessary peripheral chips will be deleted in the cutting / deleting process without any means for joining, so that there is no problem. By bonding and leaving, it is possible to enhance the mechanical reinforcement and electrical reliability of the thermoelectric conversion element to be manufactured, so that it can be bonded to the substrate by some means and left. Good.

  In this case, if the purpose is to increase the strength of the thermoelectric conversion element to be manufactured, a dummy bonding pad that is electrically isolated on the substrate in advance is manufactured at the time of forming the electrode wiring, and is similar to other bumps. In this case, the thermoelectric conversion element can be manufactured without any trouble in the process. Also, by bonding the bumps of the unnecessary chip portions to the substrate on which pads arranged in advance so as to short-circuit with the nearby electrodes are formed, the chip is left, and the thermoelectric material chip at the outermost periphery is mechanically reinforced. And the reliability of electrical connection can be improved.

  In the assembling step (e), the two substrates 72 to which the different types of thermoelectric material chips 75 are joined face each other, and the solder bumps 71 formed at the tips of the respective chips are formed on the substrates. The solder is melted by heating while applying pressure while aligning the electrode wiring 73 with the electrode wiring 73 to be joined, and the thermoelectric material chip 75 and the electrode wiring 73 on the substrate 72 are joined, and the upper and lower substrates are connected. Thus, a thermoelectric conversion element having a PN junction was completed.

  The alignment at the time of joining is performed by joining the opening 74 of the structure 74 formed on the substrate of the other type to which the solder bump 71 formed at the tip of the thermoelectric material chip 75 of each type is to be joined. Out of the remaining large one (diameter 70 μm). The reason why the joining opening of the structure 74 was made larger at the time of this alignment is to facilitate the alignment between the thermoelectric material chip and the substrate electrode and to suppress the flow of the solder. Thus, these effects were sufficiently obtained in addition to the small joining opening of the structure 74 in the joining step (c).

  The final external dimensions of the thermoelectric conversion element manufactured in this manner are about 1.2 mm in thickness, and the size is 2 mm × 2 mm, which is the size of the lower substrate on which the input / output electrodes are provided. Had an internal resistance of 180Ω. When a lead wire was connected to the input / output electrode of such a thermoelectric conversion element, and each characteristic was examined, the following results were obtained.

  The power generation performance based on the Seebeck effect is as follows. The release voltage at a temperature difference of 2 ° C. between substrates is 35 mV. When a load resistance of 1 KΩ is externally applied and a temperature difference of 2 ° C. is applied between the substrates, an output of 30 mV-30 μA is obtained. was gotten. Also, when 49 thermoelectric conversion elements having 51 pairs of PN junctions were connected in series and carried in a wristwatch, the watch could be driven at a room temperature of 20 ° C.

  As for the performance as a cooling / heating element based on the Peltier effect, an aluminum radiating plate was adhered to the substrate on the heating side with a high thermal conductive silicone adhesive, and a voltage of 2 V was applied between input electrodes. This current flows, and on the surface of the substrate on the heat absorption side, a phenomenon occurs in which the moisture in the air instantaneously freezes, which proves that the performance of the thermoelectric conversion element as a Peltier element is extremely excellent.

  In a thermoelectric conversion element having an electrode wiring structure similar to that of Example 1, the thermoelectric material chip has a cross-sectional shape of a thermoelectric material chip that is thick (70 μm) on one substrate side and thin (50 μm) on the other substrate side. The fabrication of the device will be described.

As the thermoelectric material, a sintered body of a Bi-Te-based material was used. As the substrate material, a 300 μm thick silicon wafer electrically insulated by thermally oxidizing the surface was used. Regarding the size of the element, the height of the thermoelectric material chip is 500 μm, the cross-section of the thermoelectric material chip in a cross section parallel to the substrate is square, and the length of each side is 50 μm as described above, and 70 μm in the vicinity of one junction. And Elements in FIG. 3 where the center-to-center distance between the closest similar-type thermoelectric material chips is 270 μm) and the center-to-center distance between the closest different-type thermoelectric material chips is 270 / √2 = about 190 μm). The logarithm was 51 pairs in series. (This distance was calculated with the chip size being 70 μm.)
FIG. 8 is a diagram illustrating an outline of a process for manufacturing the thermoelectric conversion element of the fourth embodiment. As shown in FIG. 3, this manufacturing method is roughly divided into six steps. This will be described step by step.

  In the bump forming step (a), a 10 μm-thick photoresist is applied to both surfaces of each of the P-type and N-type thermoelectric material wafers 40 made of a 500-μm-thick Bi—Te-based sintered body. By exposing and developing this photoresist, a resist layer having a circular shape with an opening diameter of 40 μm on one surface and an opening diameter of 60 μm on the other surface, and having openings such that the arrangement is a desired pattern. To form Here, the desired pattern is determined based on the dimensions described above so that the thermoelectric material chips are arranged in FIG.

Next, after washing the opening with an acid or the like, nickel plating of 10 μm is first applied to both surfaces by electroplating to form a so-called nickel bump. Next, solder plating was similarly performed on nickel by electroplating to form a solder layer of 30 μm. Here, the solder plating was performed so that the ratio of tin to lead was 6: 4. Next, after the photoresist was removed, a rosin-based flux was applied to the solder plating layer, and a reflow treatment was performed at 230 ° C., and a spherical solder bump having a diameter of about 50 μm on one surface and a diameter of 70 μm on the other surface was obtained. 81 could be formed on both sides of the thermoelectric material wafer 80.
In the grooving step (b), different grooving was performed on the P-type thermoelectric material wafer and the N-type thermoelectric material wafer.

FIG. 9 is a diagram showing the width and depth of the grooving in the grooving step of the present embodiment.
As shown in FIG. 9, first, in the P-type thermoelectric material wafer, a 150 μm deep groove is vertically and horizontally formed on a surface on which a solder bump having a diameter of 70 μm is formed with a dicing saw having a blade having a blade width of 160 μm. Performed in the middle between the solder bumps. As a result, a groove having a width of 160 μm and a depth of 150 μm is formed. Therefore, a P-type in which a solder bump having a diameter of about 70 μm is formed on a protrusion having a side length of 70 μm and a height from the bottom of the groove of 150 μm. A thermoelectric material wafer can be formed.

  On the surface of the N-type thermoelectric material wafer on which a solder bump having a diameter of 50 μm was formed, a dicing saw having a blade with a blade width of 180 μm was used to form a groove having a depth of 350 μm vertically and horizontally at the center between the solder bumps. As a result, a groove having a width of 180 μm and a depth of 350 μm is formed. Therefore, an N-type solder bump having a diameter of about 50 μm is formed on a protrusion having a side length of 50 μm and a height of 350 μm from the bottom of the groove. A thermoelectric material wafer can be formed.

  Such grooving is performed to form a gap between the thermoelectric material wafer and the substrate, which is required in the subsequent joining step (d) and cutting / deleting step (e) in FIG. In addition, when the fabricated thermoelectric conversion element is used as a Peltier element by changing the cross-sectional shape of the thermoelectric material chip in the direction perpendicular to the substrate, Joule heat due to energization is generated as much as possible on the heat dissipation substrate side, and heat absorption This is to prevent heat radiation to the substrate side.

In the electrode wiring step (c) shown in FIG. 8, chromium, nickel, and gold are formed on the surface of a 300 μm-thick silicon wafer substrate 82 having a 0.5 μm oxide layer on the surface by thermal oxidation. Were formed in the order of 0.1 μm, 1 μm, and 0.1 μm, respectively. Next, the electrode wiring 83 was formed on the upper and lower substrates by photolithography so as to have the electrode wiring pattern of FIG. On one of the substrates, a doughnut-shaped structure 84 having an inner diameter of 80 μm, an outer diameter of 110 μm, and a height of 30 μm was formed by curing a thick-film photoresist around a portion to be joined by a solder bump by photolithography.
On the other substrate, a donut-shaped structure 84 having an inner diameter of 60 μm, an outer diameter of 90 μm, and a height of 30 μm was formed by curing a thick-film photoresist around a portion to be joined by a solder bump by photolithography.

  In the joining step (d) in FIG. 8, the thermoelectric material wafer 80 with the solder bumps 81 produced in the bump forming step (a), the electrode wiring 83 produced in the electrode wiring step (c), and a donut-shaped structure near the joint After performing predetermined alignment with the substrate 82 on which the body 84 is formed, the solder is melted, and the thermoelectric material wafer 80 and the substrate 82 are joined. In this joining, the solder bumps on the grooved surface of the thermoelectric material wafer 80 and the donut-shaped structure 84 on the substrate 82 are combined, and heating and joining are performed while the substrate 82 is externally pressed. The P-type thermoelectric material wafer is joined to a substrate on which a structure body having an inner diameter of 80 μm, an outer diameter of 110 μm, and a height of 30 μm is formed by solder bumps having a diameter of 70 μm formed on the surface where the grooving is performed. The mold thermoelectric material wafer is bonded to a substrate on which a structure having an inner diameter of 60 μm, an outer diameter of 90 μm, and a height of 30 μm is formed by a solder bump having a diameter of 50 μm formed on the surface where the groove is formed.

  In the cutting / deleting step (e) of FIG. 8, the thermoelectric material wafer 80 bonded to the substrate 82 is formed into a thermoelectric material chip 85 bonded to the substrate 82 by cutting and deleting a part of the thermoelectric material wafer. . At this time, if necessary, a part of the substrate 82 may be cut or deleted at the same time.

  In this example, as in Example 1, the cutting / deleting step (e) was performed using a dicing saw used for cutting a silicon semiconductor or the like. The blade used for cutting / deleting was a blade having a blade thickness of 180 μm for cutting / deleting a P-type thermoelectric material wafer, and the blade having a blade thickness of 160 μm for cutting / deleting an N-type thermoelectric material wafer. In the P-type thermoelectric material wafer, a groove having a width of 160 μm has already been formed 150 μm from the substrate side by the groove forming step. Cutting and deletion are performed from the surface of the thermoelectric material wafer on the side opposite to the case where a groove having a width of 160 μm and a depth of 150 μm is formed to a depth of 350 μm.

  In the N-type thermoelectric material wafer, since a groove having a width of 180 μm has already been formed at 350 μm from the substrate side by the grooving step, in the cutting / deleting step (e), the remaining 150 μm is cut by a 160 μm blade. The thermoelectric material wafer is cut / deleted from the surface of the thermoelectric material wafer on the side opposite to when the groove having a width of 180 μm and a depth of 350 μm is formed. FIG. 10 is a cross-sectional view in a direction perpendicular to the substrate to which the thermoelectric material chip manufactured by this operation is bonded. As shown in FIG. 10, the P-type thermoelectric material chip has a size of 70 μm on one side from 150 μm from the substrate side and 50 μm on a side from 150 μm to 500 μm from the substrate side. From the substrate side, the size of one side is 50 μm up to 350 μm and the size of one side is 70 μm from 350 μm to 500 μm.

In the assembling step (f) of FIG. 8, the two substrates 82 to which the different types of thermoelectric material chips 85 are joined are opposed to each other, and the solder bumps 81 formed at the tips of the respective chips are formed on the substrates. The solder is melted by applying pressure and heating to the position to be joined with the electrode wiring 83 to be joined, so that the thermoelectric material chip 85 and the electrode wiring 83 on the substrate 82 are joined together. A thermoelectric conversion element having a PN junction on the substrate was completed.
The alignment at the time of joining was performed by the structure 84 formed on the other type of substrate to which the solder bump 81 formed at the tip of each type of thermoelectric material chip 85 should be joined.

  FIG. 11 is a cross-sectional view illustrating an outline of the thermoelectric conversion element manufactured by the series of steps. The configuration of the element is the same as that of the element manufactured in Example 1, except that the cross-sectional shapes of the P-type thermoelectric material chip 110 and the N-type thermoelectric material chip 111 are not merely rectangular, but one of P-type and N-type. It is thick on the substrate 116 side and thin on the other substrate 113 side.

  In order to examine the performance of the thermoelectric conversion element of the present Example-4, thermoelectric conversion elements having the same number of PN junctions and the same external dimensions were prepared for thermoelectric material chip sizes of 50 μm and 70 μm, and the performance as a Peltier element was evaluated by three parties. As a result of comparison, at the same input power, the device of this example showed a value that was about 10% higher than that of any of the comparative samples in terms of COP, showing the most excellent performance.

  In the Peltier element, Joule heat is generated by energization in addition to heat generated on the heat dissipation substrate side due to heat transfer due to the Peltier effect. As is well known, when the cross section of a substance to be energized has a uniform cross section, Joule heat is most heated and generated at the center. In the thermoelectric conversion element of this embodiment, the substrate on the side where the thermoelectric material chip is thinner is energized so as to be a heat dissipation substrate, so that Joule heat is generated mainly in the portion where the thermoelectric material chip is thinner. Therefore, the generated heat is smoothly performed from the closer substrate, that is, the heat radiation substrate, so that the flow of heat to the opposite heat absorbing substrate can be prevented, and the performance of the thermoelectric conversion element has been improved. .

  Although FIG. 11 shows a schematic cross-sectional view of the thermoelectric conversion element of the present Example-4, it is easy to manufacture the thermoelectric conversion element, in particular, alignment in the assembly process and bonding of the thermoelectric material chip to the substrate. Considering this, the sectional shape shown in FIG. 12 is also effective.

  In a thermoelectric conversion element having an electrode wiring structure similar to that of Example 1, an example in which a thermoelectric material and a substrate are joined to form a small thermoelectric conversion element by a method other than the solder bump method will be described. The size of the thermoelectric material chip, the number of PN junction pairs, the materials used, and the like were the same as in Example 1.

  FIG. 13 is a diagram showing an outline of a process for manufacturing the thermoelectric conversion element of the present example. As shown in FIG. 13, this manufacturing method is roughly divided into five steps. This will be described step by step.

  In the protruding electrode forming step (a), a 50 μm-thick photoresist is applied to both surfaces of each of the P-type and N-type thermoelectric material wafers 130 made of a 500-μm-thick Bi—Te-based sintered body. By exposing and developing the photoresist, a resist layer having a circular shape with an opening diameter of 90 μm and having openings such that the arrangement is a desired pattern is formed.

  Here, the desired pattern is determined based on the dimensions described above so that the thermoelectric material chips are arranged in FIG. Next, after washing the opening with an acid or the like, nickel plating of 50 μm is first applied by electroplating to form a protruding nickel layer. Next, gold plating was similarly performed on nickel by electroplating to form a gold layer of 1 μm. Next, the protruding electrode 131 made of nickel-gold was formed by removing the resist. Here, the gold layer is provided to prevent oxidation of the surface of nickel and to facilitate soldering in a later process. Therefore, when there is no fear of oxidation, the gold layer is not necessarily required.

  In the electrode wiring step (b), the surface of a silicon wafer substrate 132 having a thickness of 300 μm having a 0.5 μm oxide layer formed thereon is thermally oxidized, and the surface of the silicon wafer substrate 132 is subjected to sputtering in the order of chromium, nickel, and gold. Films were formed with a thickness of 0.1 μm, 1 μm, and 0.1 μm. Next, the electrode wiring 133 is formed on the upper and lower substrates by photolithography so as to have the electrode wiring pattern of FIG. 3, and a solder paste is printed on the electrode wiring 133 to thereby form the electrode wiring 133. completed.

In the bonding step (c), the thermoelectric material wafer 130 with the protruding electrodes 131 formed in the protruding electrode forming step (a) and the substrate 132 on which the electrode wiring 133 formed in the electrode wiring step (b) are formed are fixed. Is performed, the solder is melted, and the thermoelectric material wafer 130 and the substrate 132 are joined. (However, the upper and lower parts are expressions for convenience as described above, and there is no upper and lower parts on the substrate of the thermoelectric conversion element.)
In the cutting / deleting step (d), the thermoelectric material wafer 130 bonded to the substrate 132 is cut and deleted to form a thermoelectric material chip 134 bonded to the substrate 132. At this time, if necessary, a part of the substrate 132 may be cut or deleted at the same time. In this embodiment, the cutting / deleting step (d) is performed using a dicing saw used for cutting a silicon semiconductor or the like. The blade used for cutting / deleting had a thickness of 200 μm.

  The thickness of this blade is as follows. The length of one side of the thermoelectric material chip 134 having a square shape in this embodiment is 100 μm, the center-to-center distance between the closest similar thermoelectric material chips is 300 μm, and the different type thermoelectric material chip is shown in FIG. It was selected because it was joined in the positional relationship of The unnecessary portion of the thermoelectric material is cut / deleted at the center between the protruding electrodes 131 and at the same time, utilizing the gap between the thermoelectric material wafer 130 and the substrate 132 made of the protruding electrodes 131 having a height of 50 μm. Then, the height of the blade was adjusted so as not to damage the electrode wiring 133 on the substrate. A substrate 132 to which substantially 125 thermoelectric material chips 134 were bonded for each type of thermoelectric material was manufactured by cutting and removing the thermoelectric material of each type vertically and horizontally.

  In the assembling step (e), the two substrates 132 to which the different types of thermoelectric material chips 134 are bonded are opposed to each other, and the protruding electrodes 131 formed at the tips of the respective chips are formed on the substrates. The electrode wiring 133 made of a solder layer is aligned with the position to be joined, and is heated while applying pressure, thereby melting the solder and joining the thermoelectric material chip 134 and the electrode wiring 133 on the substrate 132. A thermoelectric conversion element having a PN junction on the upper and lower substrates was completed.

  The final external dimensions of the thermoelectric conversion element manufactured in this manner are about 1.2 mm in thickness, and the size is 4 mm × 4 mm in size of the lower substrate on which the input / output electrodes are provided. The resistance was 120Ω, and the basic characteristics were the same as those of the thermoelectric conversion element manufactured in Example-1.

  In a thermoelectric conversion element having an electrode wiring structure similar to that of Example 1, an example in which a small thermoelectric conversion element is manufactured by joining a thermoelectric material and a substrate by a solder bump method and a method using a conductive adhesive will be described. The size of the thermoelectric material chip, the number of PN junction pairs, the materials used, and the like were the same as in Example 1.

  FIG. 14 is a diagram illustrating an outline of a process for manufacturing the thermoelectric conversion element according to the present embodiment. As shown in FIG. 14, this manufacturing method is roughly divided into five steps. This will be described step by step.

  In the bump forming step (a), a 50 μm-thick photoresist is applied to one surface of each of P-type and N-type thermoelectric material wafers 140 made of a 500-μm-thick Bi—Te-based sintered body. By exposing and developing the photoresist, a resist layer having a circular shape with an opening diameter of 90 μm and having openings such that the arrangement is a desired pattern is formed. Here, the desired pattern is determined based on the dimensions described above so that the thermoelectric material chips are arranged in FIG. Further, the surface on which the photoresist is not applied is coated with a plating resist.

  Next, after washing the opening with an acid or the like, nickel plating of 40 μm is first applied by electroplating to form a so-called nickel bump. Next, solder plating was similarly performed on nickel by electroplating to form a solder layer of 30 μm. Here, the solder plating was performed so that the ratio of tin to lead was 6: 4. Next, after removing the photoresist and the plating resist, a rosin-based flux was applied to the solder plating layer, and a reflow treatment was performed at 230 ° C., and a spherical solder bump 141 having a diameter of about 100 μm was formed on one surface of the thermoelectric material wafer 140. Could be formed.

  In the electrode wiring step (b), a 300 μm-thick silicon wafer provided with a 0.5 μm oxide layer on the surface is thermally oxidized, and chromium, nickel, and gold are sequentially deposited on the surface of the substrate 142 from the substrate side by sputtering. Films were formed with a thickness of 0.1 μm, 1 μm, and 0.1 μm, respectively. Next, the electrode wiring 143 was formed on the upper and lower substrates by photolithography so as to have the same electrode wiring pattern as in FIG. Further, two types of donut-shaped structures 144 were formed by a photolithography method using a polyimide-based photoresist around a portion where the P-type thermoelectric material and the N-type thermoelectric material were joined by solder bumps.

  The structure 144 composed of the polyimide-based photoresist has an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of one of the two substrates constituting the thermoelectric conversion element at the position where the P-type thermoelectric material chip is disposed. 30 μm, a donut shape having an inner diameter of 140 μm, an outer diameter of 170 μm, and a height of 30 μm at the position where the N-type thermoelectric material chip is arranged, and an inner diameter of 140 μm and an outer diameter of 170 μm at the position where the P-type thermoelectric material chip is arranged on the other substrate A donut shape having a height of 30 μm, an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of 30 μm at the position where the N-type thermoelectric material chip is disposed.

  In the joining step (c), the thermoelectric material wafer 140 with the solder bumps 141 produced in the bump forming step (a), the electrode wiring 143 produced in the electrode wiring step (b), and the donut-shaped structure 144 near the joint are formed. After performing predetermined alignment by facing the substrate 142 thus formed, the solder was melted, and the thermoelectric material wafer 140 and the substrate 142 were joined. In joining the P-type thermoelectric material wafer and the substrate, the solder bumps formed on the surface of the P-type thermoelectric material wafer are replaced with the smaller donut formed on the substrate having an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of 30 μm. The thermoelectric material wafer 140 and the substrate 142 were aligned by being placed inside the mold structure 144.

  Similarly, in bonding the N-type thermoelectric material wafer to the substrate, the solder bump formed on the surface of the N-type thermoelectric material wafer is replaced with a small donut having an inner diameter of 120 μm, an outer diameter of 150 μm, and a height of 30 μm formed on the substrate. The thermoelectric material wafer 140 and the substrate 142 were aligned by being placed inside the mold structure 144. Here, the reason why the smaller one of the two sizes of the donut-shaped structures formed on the substrate was used for joining the thermoelectric material wafer 140 and the substrate 142 was that the joining position was definitely determined. The aim is to increase mutual alignment accuracy.

In the cutting / deleting step (d), a thermoelectric material chip 145 bonded to the substrate 142 is formed by cutting / deleting a part of the thermoelectric material wafer from the thermoelectric material wafer 140 bonded to the substrate 142. At this time, if necessary, a part of the substrate 142 may be cut or deleted at the same time. In this embodiment, the cutting / deleting step (d) is performed using a dicing saw used for cutting a silicon semiconductor or the like. The blade used for cutting / deleting had a thickness of 200 μm. The thickness of this blade is such that the side length of the thermoelectric material chip 145 having a square shape in this embodiment is 100 μm, the center-to-center distance between the closest similar thermoelectric material chips is 300 μm, and different types of thermoelectric material chips are shown in FIG. It was selected because it is joined in a positional relationship.
Unnecessary portions of the thermoelectric material are cut / deleted at the center between the solder bumps 141 and at the same time on the substrate by using the gap between the thermoelectric material wafer 140 and the substrate 142 made of nickel bumps having a height of 40 μm. The height of the blade was adjusted so that the electrode wiring 143 was not damaged. A substrate 142 to which substantially 125 thermoelectric material chips 145 were bonded for each type of thermoelectric material was manufactured by cutting and removing the same with a dicing saw blade vertically and horizontally.

  In the assembling step (e), a conductive adhesive mainly composed of silver particles and an epoxy resin is attached to the tip of the thermoelectric material chip 145 with respect to the two substrates 142 to which the different types of thermoelectric material chips 145 are joined. Are adhered by stamping, these are faced to each other, the tip of the thermoelectric material chip 145 and the electrode wiring 143 formed on the substrate 142 are aligned at a position to be joined, and heated while being pressurized. The adhesive was cured, and the thermoelectric material chip 145 and the electrode wiring 143 on the substrate 142 were joined to complete a thermoelectric conversion element having a PN junction on the upper and lower substrates. Although this joining was performed inside the remaining donut-shaped structure 144, the donut-shaped structure 144 prevented the conductive adhesive from sticking out at the time of joining.

  The final external dimensions of the thermoelectric conversion element manufactured in this manner are about 1.2 mm in thickness, and the size is 4 mm × 4 mm in size of the lower substrate on which the input / output electrodes are provided. The resistance was 120Ω, and the basic characteristics were the same as those of the thermoelectric conversion element manufactured in Example-1.

  In the present embodiment, in the step of forming bumps on the thermoelectric material, there is no formation of a plating resist by photolithography on both sides, so there is no need to apply photoresist on both sides or use a double-sided aligner / exposure machine, Equipment and processes can be simplified.

  As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and a wide range of applications can be considered. For example, in each of the examples, a sintered body of a Bi—Te-based thermoelectric material was used as a thermoelectric material. However, it is needless to say that the present invention is not limited to this thermoelectric material. -It can be applied to various thermoelectric materials such as Ge-based materials and Co-Sb-based materials. In each embodiment, a small thermoelectric conversion element and a method for manufacturing the same are described. However, according to the thermoelectric conversion element and the method for manufacturing the same according to the present invention, after a thermoelectric material chip is manufactured, it is sandwiched between two substrates. The method can also be applied to a relatively large thermoelectric conversion element manufactured by the above method.

It is a figure showing appearance of a thermoelectric conversion element concerning the present invention. FIG. 2 is a diagram illustrating a cross section of a main part along A-A ′ and B-B ′ illustrated in FIG. 1. FIG. 3 is a diagram illustrating a relationship between an arrangement of thermoelectric material chips and electrode wirings of the thermoelectric conversion element described in Example 1 of the present invention. It is a figure showing the outline of the process for manufacturing the thermoelectric conversion element concerning Example 1 of the present invention. FIG. 4 is a diagram showing a relationship between the arrangement of thermoelectric material chips and electrode wiring of a thermoelectric conversion element according to Example 2 of the present invention. FIG. 4 is a diagram illustrating an outline of a process for manufacturing a thermoelectric conversion element according to Example-2 of the present invention. FIG. 8 is a diagram illustrating an outline of a process for manufacturing a thermoelectric conversion element according to Example 3 of the present invention. FIG. 9 is a diagram illustrating an outline of a process for manufacturing a thermoelectric conversion element according to Example-4 of the present invention. It is a figure showing the cross section of the thermoelectric material wafer after the grooving process among the processes for manufacturing the thermoelectric conversion element concerning Example-4 of the present invention. It is a figure showing the cross section of the principal part after the cutting and elimination process among the processes for manufacturing the thermoelectric conversion element concerning Example-4 of the present invention. FIG. 9 is a diagram showing a completed cross section of a thermoelectric conversion element according to Example-4 of the present invention. It is sectional drawing of the thermoelectric conversion element of the structure relevant to the thermoelectric conversion element of Example-4 of this invention. It is the figure which showed the outline | summary of the process for manufacturing the thermoelectric conversion element concerning Example-5 of this invention. It is a figure showing the outline of the process for manufacturing the thermoelectric conversion element concerning Example-6 of the present invention. FIG. 10 is a diagram showing a relationship between the arrangement of thermoelectric material chips and electrode wiring of a conventional thermoelectric conversion element. It is the figure which showed the outline | summary of the processing of the thermoelectric material in manufacture of the conventional thermoelectric conversion element by the longitudinal cross-sectional view. It is a figure showing the manufacturing method of the conventional thermoelectric conversion element which manufactures a thermoelectric conversion element using a substrate provided with the thermoelectric material chip and electrode wiring.

Explanation of reference numerals

11, 175 Thermoelectric conversion elements 12, 21, 31, 42, 56, 72, 82, 102, 113, 116, 122, 123, 132, 142, 150, 171 Substrates 13, 34, 52, 110, 120, 153 P-type thermoelectric material chip 14, 35, 53, 111, 121, 154 N-type thermoelectric material chip 15 PN junction electrode 22 Bonding material 23, 44, 74, 84, 104, 115, 144 Structure 32, 50 Upper substrate electrode Wiring patterns 33, 51 Lower substrate electrode wiring patterns 40, 60, 70, 80, 130, 140 Thermoelectric material wafers 41, 81, 71, 91, 101, 112, 141 Solder bumps 43, 65, 73, 83, 103, 114 , 133, 143, 173 Electrode wiring 45, 66, 75, 85, 134, 145, 163, 172 Thermoelectric material chip 54 Upper substrate dummy electrode 55 Lower substrate dummy electrode 61 Nickel layer 62, 63 Solder layer 64 Alumina substrate 67 Groove 68 Convex portion 90 P-type thermoelectric material wafer 92 N-type thermoelectric material wafer 105 N-type thermoelectric material 131 Projecting electrode 151 Upper substrate electrode Wiring 152 Lower substrate electrode wiring 161 Thermoelectric material 162 Layer 174 for soldering Bonding material

Claims (7)

First and second substrates provided with a plurality of electrodes respectively,
A plurality of P-type thermoelectric material chips and a plurality of N-type thermoelectric material chips arranged vertically and horizontally between the first substrate and the second substrate and PN-joined by the electrodes,
The plurality of P-type thermoelectric material chips and the plurality of N-type thermoelectric material chips have a substantially square cross-sectional shape in a plane parallel to the surface of the first or second substrate,
The plurality of P-type thermoelectric material chips and the plurality of N-type thermoelectric material chips are arranged in a lattice shape in the direction of the sides of the substantially quadrangular shape, and the P-type thermoelectric material chips and the N-type The thermoelectric material chips are alternately arranged, and in the side orthogonal to the one side, the arrangement in which only the P-type thermoelectric material chips are arranged and the arrangement in which only the N-type thermoelectric material chips are arranged are alternately arranged. The thermoelectric conversion element characterized by the above-mentioned. The plurality of P-type thermoelectric material chips, and at least one of the plurality of N-type thermoelectric material chips is electrically separated and provided between the first substrate and the second substrate. The thermoelectric conversion element according to claim 1, wherein: 3. The thermoelectric conversion element according to claim 1, wherein the plurality of electrodes include electrodes to which a plurality of thermoelectric material chips of the same type are connected. First and second substrates provided with a plurality of electrodes respectively,
A plurality of P-type thermoelectric material chips and a plurality of N-type thermoelectric material chips provided between the first substrate and the second substrate and PN-joined by the electrodes,
A thermoelectric conversion element, wherein the width of the P-type thermoelectric material chip or the N-type thermoelectric material chip changes in the height direction of the thermoelectric material chip. First and second substrates provided with a plurality of electrodes respectively,
A plurality of P-type thermoelectric material chips and a plurality of N-type thermoelectric material chips provided between the first substrate and the second substrate and PN-joined by the electrodes,
The structure in which the P-type thermoelectric material chip or the N-type thermoelectric material chip is provided in the vicinity of a portion of at least one of the first substrate and the second substrate that is bonded to the electrode. Characteristic thermoelectric conversion element. The thermoelectric conversion element according to claim 5, wherein the structure is obtained by curing a photosensitive resin. The thermoelectric conversion element according to claim 5, wherein the structure is made of a polymer material.

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