JP2000286467A - Electrically insulating material, and module and manufacture of the module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically insulating material which allows joint of conductors with a high joint strength, without degradation in insulating characteristics. SOLUTION: Related to an electrically insulating material for jointing conductors, ceramic particles of softening-point higher than that of glass matrix are dispersed in a glass matrix, whose softening-point is lower than the conductor, and the thermal expansion factor of the ceramics particle is lower than that of glass matrix, with the thermal expansion factor 150% or less of the conductor provided as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating material for joining electric conductors, a module such as a thermoelectric conversion module using the electric insulating material, and a method for manufacturing the module.

[0002]

2. Description of the Related Art In order to mechanically join electrical conductors while maintaining electrical insulation, there is a method of joining glass using an electrical insulating material. In this case, a glass with lower heat resistance than the conductor is sandwiched between the two conductors,
Welding is performed while maintaining the temperature at which the fluidity of the glass increases. In order to obtain high bonding strength, it is desirable that the glass layer between the conductors is thin, dense, and free from voids. However, the insulating property is reduced in a portion where the glass layer is very thin or where the glass layer is not substantially present. Here, when glass having low heat resistance is used, the fluidity of the glass layer is increased, so that an extremely thin portion of the glass layer is easily formed, and the insulating property is apt to be reduced. On the other hand, when glass having high heat resistance is used, the fluidity of the glass layer is low, so that voids are easily formed and the bonding strength is liable to decrease.

In particular, when thermoelectric semiconductors are joined to each other in a relatively large area of about several mm ² to several tens of mm ² as in a thermoelectric conversion module, breakage due to a decrease in joining strength and a decrease in insulation properties are apt to occur. In addition, when a high temperature end is exposed to a high temperature during use, such as a thermoelectric conversion module, and a temperature difference occurs internally, it is difficult to achieve both insulation and bonding strength during use.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electric insulating material which can join conductors with high joining strength without lowering insulation. Another object of the present invention is to provide a module using such an electrically insulating material, the insulation and the heat resistance of which do not decrease even when used at a high temperature, and a method for easily manufacturing such a module. Is to do.

[0005]

The electric insulating material of the present invention is an electric insulating material for joining conductors, and has a softening point lower than that of a glass matrix in a glass matrix having a softening point lower than that of the conductor. High ceramic particles are dispersed. The electric insulating material of the present invention has at least one of a coefficient of thermal expansion of ceramic particles smaller than a coefficient of thermal expansion of a glass matrix and a coefficient of thermal expansion of 150% or less of a coefficient of thermal expansion of a conductor as a whole. Satisfies the condition.

The glass matrix contains at least one of zinc and aluminum, but preferably does not contain alkali metals and alkaline earth metals as main components. As ceramic particles, oxides such as S
i-oxide is used. Further, it is preferable that a reaction layer is formed at the interface between the glass matrix and the ceramic particles. As the conductor, a thermoelectric semiconductor such as Si
-A Ge semiconductor is used. In this case, the electric insulating material preferably has lower mechanical strength than the thermoelectric semiconductor.

A module according to the present invention is a module in which a plurality of conductors arranged in a row are joined by an electric insulating material, wherein the electric insulating material is contained in a glass matrix having a softening point lower than that of the conductor. Is characterized by comprising ceramic particles having a high softening point dispersed therein.

According to the method of manufacturing a module of the present invention, in manufacturing a module in which a plurality of conductors arranged in a row are joined by an electrical insulating material, a glass matrix having a softening point lower than that of the conductive material is used as the electrical insulating material. A material in which ceramic particles having a softening point higher than that of the glass matrix are dispersed therein, and the electric insulating material is interposed between adjacent conductors, and is maintained at or above the softening point of the glass matrix. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The electrical insulating material of the present invention is obtained by dispersing ceramic particles having a higher softening point than a glass matrix in a glass matrix having a lower softening point than a conductor.

As the glass matrix, oxides such as SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , ZnO, PbO, A ₂
-O (alkali metal oxides such as Na ₂ O), A-O
(Alkaline earth metal oxide such as CaO) or the like is used as a main component. The main component has a content of 1 mol
%, Preferably 10 mol% or more, and does not include the case where it is mixed as a small amount of impurities.
It is preferable to use a glass matrix containing at least one of ZnO and Al ₂ O ₃ among the above oxides. On the other hand, the glass matrix preferably does not contain an alkali metal oxide or an alkaline earth metal oxide as a main component. This is because, in a glass matrix containing an alkali metal oxide or an alkaline earth metal oxide, cations of an alkali metal or an alkaline earth metal contribute to electric conduction, thereby lowering resistance and extremely lowering insulation. . A glass matrix material can be prepared by melting and solidifying the above glass component, and properties such as a coefficient of thermal expansion and a softening point can be appropriately controlled by a mixing ratio of the glass component. Specifically, the softening point of the glass matrix is 3
It can be adjusted to the range of 00 to 1000 ° C. The glass matrix preferably has a uniform composition,
It is sufficient if the characteristics can be regarded as a continuum without abrupt changes in characteristics depending on the part. The glass matrix may be crystallized.

The ceramic particles may be made of SiO ₂ , in consideration of adhesion to a glass matrix and heat resistance.
Al ₂ O ₃ , Si ₃ N _{4 and the} like are used. SiO ₂ or Al ₂
O ₃ may be crystallized. The softening point of the ceramic particles is 1200 ° C. for SiO ₂ and 1400 ° C. for Al ₂ O ₃ .

As described above, it is preferable to use, as the glass matrix or the ceramic particles, the oxide glass whose physical properties are easily adjusted and whose adhesion is high.

The size of the ceramic particles is preferably 1 μm or more and less than the thickness of the insulating layer to be formed, and more preferably 1 μm or more and less than の of the thickness of the insulating layer to be formed. If the size of the ceramic particles is less than 1 μm, the effect of adding the ceramic particles cannot be sufficiently exhibited due to the reaction with the glass matrix. In general, the thickness of the insulating layer that joins the conductors is adjusted to 1 to 1000 μm. This is because if it is less than 1 μm, the insulation performance may be partially reduced, and if it exceeds 1000 μm, the entire size of the joined body becomes too large. When the size of the ceramic particles is less than the thickness of the insulating layer, and further less than の of the thickness of the insulating layer, the fluidity of the glass matrix can be effectively utilized to achieve good bonding with the conductor.

The mixing ratio of the ceramic particles in the insulating material is preferably 1 to 70 vol% in volume content. If the content is less than 1 vol%, the effect of adding the ceramic particles cannot be sufficiently exerted, and it is difficult to achieve both insulation and heat resistance. If it exceeds 70% by volume, the fluidity of the glass matrix may be impaired, leading to insufficient strength of the insulating layer.

In the electric insulating material of the present invention, it is preferable that the ceramic particles are distributed in an island shape in the glass matrix. In order to form a structure in which the ceramic particles are distributed in an island shape in the glass matrix as described above, the glass matrix material and the ceramic particles are mixed as a powder and heated to a temperature higher than the softening point of the glass matrix material. Further, ceramic particles may be added in a temperature range where the glass matrix material has fluidity. By using such a method, a reaction layer is formed at the interface between the glass matrix and the ceramic particles, and the mechanical strength as an electrical insulating material is increased. The coefficient of thermal expansion of the electrically insulating material as a whole is 50 to 15 times the coefficient of thermal expansion of the conductor to be joined.
It is preferably 0%, more preferably 80 to 130%.

In order to manufacture a line type module using the electric insulating material of the present invention, for example, by joining a plurality of conductors arranged in a row with the electric insulating material, the electric insulating material is placed between adjacent conductors. Scissors, holding above the softening point of the glass matrix. In this way, for example, the porosity and void size of the insulating layer can be controlled by adjusting the rate of temperature rise of the conductor and the electrical insulating material until the softening point is reached.

The module of the present invention is a line type module in which a plurality of conductors arranged in a row are joined by an electric insulating material, wherein the electric insulating material is a glass module having a softening point lower than that of the conductor. In which ceramic particles having a softening point higher than that of the glass matrix are dispersed.

In this case, in order to reduce the probability of destruction of the module, it is desirable that the strength of the insulating layer formed between the conductors and made of the above-mentioned electrical insulating material is lower than the strength of the conductor. In order to realize such a strength relationship, the porosity of the insulating layer is preferably 5 to 50%, more preferably 5 to 25%.

[0019]

Embodiments of the present invention will be described below. As shown in Table 1, six types of glassy insulating materials A to F were prepared. The insulating materials A to D are made of only glass containing no ceramic particles, and the insulating material E contains Al ₂ O ₃ particles having a size of 250 μm or less with respect to the glass matrix at a rate of 50 vol%. , Insulating material F
Is a glass matrix containing 30 vol% of SiO ₂ particles having a size of 100 μm or less.

Table 1 shows the thermal expansion coefficients and softening points of the six types of glassy insulating materials A to F. The coefficient of thermal expansion is 25-300 ° C
Is a coefficient of thermal expansion [× 10 ⁻⁷ / ° C.]. The thermal expansion coefficients of the components of the insulating materials E and F are 30 to 60 for the glass matrix, 90 for the Al ₂ O ₃ particles, and 5 for the SiO ₂ particles. The softening point [° C.] is the temperature at which the insulating material softens and deforms under its own weight.

The above insulating materials A to F are sandwiched between two Si-Ge based thermoelectric semiconductors having a size of 3.5 × 3.5 × 3 to 10 (mm). Table 1 shows the results of examining the joining condition by joining by heating.
The relative density of the Si—Ge-based thermoelectric semiconductor is 98%, and the coefficient of thermal expansion is 38 × 10 ⁻⁷ / ° C.

In Table 1, "OK" means that Si
-Ge and the insulating layer were firmly fixed without cracking. When the insulating material E was used, cracks occurred in both the Si-Ge and the insulating layer. In the case where the insulating materials A to D are used, the thickness of the insulating layer after joining is 60 μm or less, and a portion where the thickness is extremely small (the thickness is almost 0).
Was observed. When the insulating materials E and F were used, the thickness of the insulating layer after joining was about 500 μm. From the result of the bonding evaluation, the thermal expansion coefficient of the insulating material is preferably less than 60 [× 10 ⁻⁷ / ° C.]. When the coefficient of thermal expansion exceeds 60 as in the case of the insulating material E, stress is applied to Si-Ge, and Si-Ge
Cracks occur in both the insulating layer and the insulating layer. Since the coefficient of thermal expansion of Si-Ge is 38, the coefficient of thermal expansion of the insulating material is 150% or less of the coefficient of thermal expansion of the conductor, and 50 to 150%.
It is understood that it is preferable that

Next, Si-Ge having a good bonding evaluation was used.
/ Insulating material / Si-Ge bonded body of 1000 to 1100
After conducting a heat resistance test at a temperature of ° C., the bonding condition was examined and the heat resistance in terms of strength was evaluated. When the insulating material B was used, the Si-Ge-based thermoelectric semiconductor was peeled off because of the high fluidity of the insulating layer. When the insulating material D was used, cracks occurred in the insulating layer. This is considered to be because a large amount of voids remained in the insulating layer after bonding, and the voids grew in the insulating layer after the heat resistance test, resulting in an extremely low strength. From the results of the heat resistance evaluation, the softening point of the insulating material was 620 to 750.
° C, 630-730 ° C (Si-Ge softening point 12
(50 to 60% with respect to 50 ° C.).
If the softening point is lower than the lower limit temperature, sufficient heat resistance cannot be obtained. On the other hand, when the softening point exceeds the upper limit temperature, voids in the insulating layer do not decrease and densification becomes insufficient, so that heat resistance and strength also decrease.

Next, Si-Ge having a good heat resistance evaluation was used.
The electrical resistance R [Ω] through the insulating material was measured for the bonded body of / insulating material / Si-Ge. Assuming that the area of the bonded portion of the bonded body sample was W [cm ² ], log (R × W) was obtained, and the insulating property was evaluated. When the insulating material A is used, the insulating performance is extremely deteriorated because the insulating layer contains an alkali metal oxide that contributes to ion conduction.

Further, from the overall evaluation results, the insulating material E
Compared with F, it is preferable to use SiO ₂ rather than Al ₂ O ₃ as ceramic particles. This is because the coefficient of thermal expansion of the glass matrix (30-60) is higher than that of SiO _2.
This is because the thermal expansion coefficient (5) is small (8 to 17%) and the whole insulating material becomes strong, and the thermal expansion coefficient of the entire insulating material approaches the thermal expansion coefficient of Si-Ge as a conductor.

[0026]

[Table 1]

FIG. 1 shows an electron micrograph (reflection electron beam composition image) of the vicinity of the bonding interface between the Si-Ge semiconductor and the insulating layer. The position of the vertical line seen from the center right is the bonding interface, the right side of the bonding interface is the Si-Ge semiconductor, and the left side is the insulating layer. In the insulating layer, dark black portions are voids, gray portions are SiO ₂ particles, and other white portions are glass matrices.

FIG. 2A schematically shows the structure of the inside of the insulating layer, and FIG. 2B shows the result of elemental analysis at the analysis position shown in FIG. 1A. Similarly, FIG.
FIG. 3B schematically shows the structure of the junction interface between the -Ge semiconductor / insulating layer, and FIG. 3B shows the result of elemental analysis at the analysis position in FIG. The elemental analysis was performed using EPMA (electr
On probe microanalyzer), the distribution of element concentration was measured. 2B and 3B, the horizontal axis represents distance, and the vertical axis represents the concentration of each element.

As shown in FIG. 2, a diffusion reaction layer is formed between the SiO ₂ particles and the Zn component and the Al component in the glass matrix, so that the two are strongly bonded inside the insulating layer. . The thickness of the diffusion reaction layer is 1 to
3.5 μm. When the insulating material in which the SiO ₂ particles are dispersed in the glass matrix is used as described above, the two can form a diffusion reaction layer and can be firmly joined to each other, and particularly when strength and heat resistance are required. It is effective for

As shown in FIG. 3, the insulating layer and the Si-G
A diffusion reaction layer is also formed at the junction interface with the e-semiconductor, and both are firmly joined. That is, at the interface,
The diffusion reaction layer is formed by diffusing Si and Ge into the insulating layer from the Ge semiconductor side and enriching Zn in the glass matrix along the interface. In particular, Ge
Shows that a reaction layer of about 6 μm was formed in the glass matrix, indicating that a sufficient diffusion reaction had progressed and that a strong bond was formed. In addition, Si is added to the insulating layer side by 1
A diffusion reaction layer of about 2 μm is formed, and Zn is Si—Ge
It was found that a diffusion reaction layer of about 1 μm was formed on the semiconductor side. These diffusion reaction layers are also highly effective for firm bonding.

Next, a 1 × 18 line type module shown in FIGS. 4 and 5 was manufactured. Although not shown, the low-temperature end side has the same structure as the high-temperature end side. At this time, the insulating material F that gave the best results in Table 1 was used. 4A is a plan view of the line type module, FIG. 4B is a side view of the line type module, and FIG. 5 is a cross-sectional view showing the vicinity of the high-temperature end of the line type module of FIG. is there.

First, 0.5 is applied to both ends of the Si-Ge semiconductor 1.
After fixing the carbon strain relaxation electrode 2 having a thickness of mm by diffusion bonding, it is machined to 3.5 × 3.5 × 9.
A Si-Ge semiconductor device having a size of (mm) was manufactured. In the Si-Ge semiconductor 1, Si = 80 at%, Ge =
It has a compounding ratio of 20 at% and contains boron as a p-type impurity or phosphorus as an n-type impurity in an amount of 0.5 to 2.0E20mo.
It is contained at a concentration of 1 / m ³ and the relative density is 98%. Next, 9 pairs (18 in total) of p-type and n-type Si-Ge
The semiconductor elements were alternately arranged in a line, and the side surfaces of the adjacent Si—Ge semiconductors 1 were fusion-bonded with an insulating material F to form an insulating layer 3. Thereafter, a Mo electrode 5 was brazed on the carbon electrode 2 with a nickel-based brazing material 4 so as to connect the Si-Ge semiconductor elements in series. Note that a gap was formed between the insulating layer 3 and the nickel-based solder 4.

In the above-described bonding step using the insulating material F, the porosity and the void size in the insulating layer 3 are controlled by controlling the rate of temperature rise until the bonding temperature is reached. Modules 1 and 2 were produced. In Table 2, the porosity is the volume% occupied by the voids. The maximum length of one void was measured as the void size, and the largest void size observed was defined as the maximum void size.

Each of these modules 1 and 2 is 50
Table 2 shows the results of evaluating the strength by the number of modules whose insulating layers were broken by dropping from a height of cm.

As shown in Table 2, while the number of destructions was 0 in the module 1, the insulating layer was destroyed in 4 modules of the module 2. From this result, it is understood that it is desirable to control the porosity and the void size of the insulating layer as follows. The porosity of the insulating layer is 50% or less,
It is desirable that the content be 5% or less. Maximum void size is 300
It is desirable that the thickness be 0 μm or less, and more preferably 180 μm or less.

[0036]

[Table 2]

Further, assuming that the module would be deformed at the time of manufacture or use, a destructive test was performed by applying a bending force to the module 1. As a result, many of them were broken in the insulating layer, and the power generation performance of the line module was not changed. However, there are some parts where the porosity of the insulating layer is locally reduced to 5% or less, where the Si-Ge semiconductor is broken. In this case, the module cannot be used due to disconnection. For this reason, in order to reduce the probability of destruction, it is desirable that the strength of the insulating layer be lower than the strength of the conductor (in this case, a Si—Ge semiconductor). In order to establish such a strength relationship, the porosity of the insulating layer is desirably 5% or more. From the above results, in order to reduce the probability of module breakage, it is effective that the porosity of the insulating layer composed of the glass matrix and the ceramic particles is 5 to 50%, and more preferably 5 to 25%.

The line type module 1 is installed such that its high-temperature end is in contact with a heat source of about 500 ° C. and its low-temperature end is in contact with a cooling plate of about room temperature, and the module is sandwiched between the cooling plate and the heat source. A load of 15 kgf was applied between them for use. As a result, both the insulating layer and the Si-Ge semiconductor did not break down, and operated favorably as a thermoelectric power module having a maximum output of 0.9 W.

[0039]

As described above in detail, according to the present invention, it is possible to provide an electric insulating material which can join conductors with a high joining strength without lowering the insulating property. Therefore, it is possible to provide a module in which insulation and heat resistance are not reduced even when used at high temperatures. Further, according to the present invention, it is possible to provide a method capable of easily manufacturing such a module.

[Brief description of the drawings]

FIG. 1 is an electron micrograph showing a microstructure near a bonding interface between a Si—Ge semiconductor and an insulating layer.

FIGS. 2A and 2B are a schematic diagram showing a structure structure inside an insulating layer and a diagram showing a result of elemental analysis. FIGS.

3A and 3B are a schematic diagram showing a structure of a bonding interface of a Si-Ge semiconductor / insulating layer and a diagram showing a result of elemental analysis.

FIG. 4 is a plan view and a side view of the line-type thermoelectric conversion module according to the present invention.

FIG. 5 is an enlarged sectional view showing the vicinity of a high-temperature end of the line thermoelectric conversion module according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Si-Ge semiconductor 2 ... Carbon electrode 3 ... Insulating layer 4 ... Ni-based solder 5 ... Mo electrode

Claims (13)

[Claims] 1. An electrically insulating material for joining conductors, wherein ceramic particles having a softening point higher than the glass matrix are dispersed in a glass matrix having a softening point lower than that of the conductor. An electrically insulating material having a coefficient of thermal expansion of 150% or less of the coefficient of thermal expansion of a body. 2. An electric insulating material for joining conductors, wherein ceramic particles having a softening point higher than the glass matrix are dispersed in a glass matrix having a softening point lower than the conductor. An electrically insulating material, wherein the coefficient of thermal expansion is smaller than the coefficient of thermal expansion of a glass matrix. 3. An electric insulating material for joining conductors, wherein ceramic particles having a softening point higher than the glass matrix are dispersed in a glass matrix having a softening point lower than the conductor. An electrically insulating material having a coefficient of thermal expansion smaller than that of a glass matrix and having a coefficient of thermal expansion of 150% or less of the coefficient of thermal expansion of the conductor as a whole. 4. The electrical insulating material according to claim 1, wherein said ceramic particles are oxides. 5. The electrical insulating material according to claim 4, wherein said oxide is a Si oxide. 6. The electrical insulating material according to claim 1, wherein a reaction layer is formed at an interface between the glass matrix and the ceramic particles. 7. The electrically insulating material according to claim 1, wherein said glass matrix contains at least one of zinc and aluminum. 8. The electrically insulating material according to claim 1, wherein said glass matrix does not contain an alkali metal and an alkaline earth metal as main components. 9. The electrically insulating material according to claim 1, wherein said conductor is a thermoelectric semiconductor. 10. The electrically insulating material according to claim 9, wherein said thermoelectric semiconductor is a Si—Ge based semiconductor. 11. The electrically insulating material according to claim 9, wherein the insulating material has a lower mechanical strength than the thermoelectric semiconductor. 12. In a module in which a plurality of conductors are joined by an electric insulating material, ceramic particles having a softening point higher than the glass matrix are dispersed in a glass matrix in which the electric insulating material has a lower softening point than the conductor. A module comprising: 13. In manufacturing a module in which a plurality of conductors are joined by an electrically insulating material, a ceramic having a softening point higher than the glass matrix in a glass matrix having a softening point lower than the conductor as the electric insulating material. A method for manufacturing a module, comprising using particles in which particles are dispersed, sandwiching the electrical insulating material between adjacent conductors, and maintaining the electrical insulating material at or above the softening point of the glass matrix.