JPH0455145B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a joining member formed by joining a silicon carbide ceramic sintered body to another ceramic sintered body or a metal, and a joining method therefor. For example, there is a ceramic package that houses a semiconductor device, which is made by bonding a silicon carbide ceramic to another ceramic sintered body, and the present invention is suitable for application to such a ceramic package. [Prior Art] When joining a ceramic sintered body to another ceramic sintered body or metal, it is known to metalize the surface of the ceramic sintered body. As an example, JP-A-55-113683 discloses that the surface of a silicon carbide ceramic sintered body is coated with powder of at least one kind of powder of groups a, a, a, a, and a of the periodic table of elements, and the powder is non-oxidizing. It is described that metallization is performed by firing in an atmosphere. Then, nickel is applied to the metalized surface in this way.
It is described that after plating with copper or the like, soldering or brazing with various metals is performed. [Problems to be Solved by the Invention] The above-mentioned prior art does not describe an example in which a carbide-based ceramic sintered body is actually joined to a metal or other ceramic sintered body, and the problems at the time of joining are not described. Not considered at all. The purpose of the present invention is to metallize the surface of a silicon carbide ceramic sintered body and solve problems when brazing it with other ceramic sintered bodies or metal, so that a highly reliable joint can be obtained. The present invention provides a joining member and a method for manufacturing the same. [Means for Solving the Problems] The present invention provides a joining member in which a surface of a silicon carbide ceramic sintered body to be joined is metallized and is brazed to another ceramic sintered body or a metal. A ceramic sintered body having a mixed layer of chromium silicide and chromium carbide on the surface to be joined, and a chromium layer and a layer made of at least one of nickel and copper thereon, and the other ceramic sintered body or metal. It is characterized by having a thermal stress relieving material between the brazing surfaces. [Function] By forming a chromium layer on the surface to be joined of the silicon carbide ceramic sintered body, and forming a layer made of at least one of nickel, copper, and silver on top of the chromium layer and brazing it, brazing is achieved. It is possible to prevent the film from peeling off from the part or the layer made of at least one of nickel and copper. However, it was found that if the chromium layer was formed directly on the surface of a silicon carbide ceramic sintered body, it would peel off from the interface between the sintered body and the chromium layer when a thermal fatigue test was performed after brazing. . The present inventors have discovered that when a silicon carbide-based ceramic sintered body has a mixed layer of chromium silicide and chromium carbide on the surface and a chromium layer thereon,
It was discovered that the chromium layer no longer peels off. The reason that peeling of the chromium layer can be prevented in this way is that the mixed layer of chromium silicide and chromium carbide acts to firmly bond the silicon carbide ceramic sintered body and the chromium layer. This is based on the fact that it has the heat resistance to withstand the temperatures applied. In addition, when brazing a silicon carbide ceramic sintered body with another ceramic sintered body or metal,
There is a difference in the coefficient of thermal expansion between the two, and there is also a difference in the coefficient of thermal expansion between the two and the brazing metal, so thermal stress occurs due to overcooling after brazing, and the silicon carbide ceramic sintered body I found out that it can break. As an example, when a silicon carbide ceramic sintered body and alumina were brazed, the silicon carbide ceramic sintered body cracked during the cooling process after brazing. In addition, the thermal expansion coefficient of silicon carbide ceramics in this case is approximately 3.7×
10 ^-6 /℃, and the thermal expansion coefficient of alumina is approximately 7.0.
×10 ^-6 /℃. This cracking occurs regardless of the presence or absence of a metallized layer on the surface of the silicon carbide ceramic sintered body. In order to prevent the silicon carbide ceramic sintered body from cracking due to thermal stress, it is necessary to interpose a thermal stress relieving material in the brazed portion. The reason why a silicon carbide-based ceramic sintered body cracks is because the ceramic sintered body does not follow the shrinkage of the brazing during the cooling process after brazing, resulting in thermal stress. By interposing a thermal stress relieving material on the brazing surface and causing the thermal stress relieving material to follow the contraction of the brazing material, it was possible to prevent cracking of the silicon carbide ceramic sintered body. The thickness of the thermal stress relaxation material is preferably 100 μm or more, and it is particularly preferable to use a thin plate with a thickness of 100 μm to 1000 μm. As the material for the thermal stress relaxation material, it is preferable to use silver, copper, or an alloy thereof, which has good brazing properties and good thermal conductivity. In the present invention, as a method for forming a mixed layer of chromium silicide and chromium carbide on the surface to be joined of a silicon carbide ceramic sintered body and forming a chromium layer thereon, the following method is very preferable.
That is, this is a method in which chromium powder is applied to the surface of a silicon carbide-based ceramic sintered body, and then heated and fired in a non-oxidizing atmosphere. Heating temperature is 900-1300
A range of 0.degree. C. is preferred. The heating atmosphere is preferably an inert atmosphere or an atmosphere with an oxygen partial pressure of 10 ^-2 torr or less. By this firing, a mixed layer of chromium silicide and chromium carbide is formed on the surface of the silicon carbide ceramic sintered body, chromium is formed on the mixed layer, and a layer containing chromium oxide is further formed on the layer. After this, the layer containing chromium oxide is removed to expose the chromium layer. If a layer consisting of at least one of nickel and copper is formed on a chromium oxide layer or a layer containing chromium oxide and then brazed, the layer will peel off from the interface between the chromium oxide and the layer above it, so this must be avoided. Must be. As the mating material in the silicon carbide ceramic joining member of the present invention, carbide ceramics, oxide ceramics, non-oxide ceramics, and various metals can be used. As the carbide ceramics, the same type of silicon carbide ceramics can be used. An example of an oxide ceramic is alumina. A specific example of a sintered silicon carbide ceramic body brazed to another sintered ceramic body is a package for a semiconductor device. As the density and speed of semiconductor devices increase, the amount of heat generated increases, and there is a need to improve the heat dissipation properties of packages.As a result, silicon carbide ceramic sintered bodies are bonded to alumina to form packages. began to take place. The idea is to improve heat dissipation by brazing a sintered silicon carbide ceramic substrate on which a semiconductor device having an integrated circuit is mounted to an alumina frame and attaching heat dissipation fins to the sintered silicon carbide ceramic substrate. It is extremely effective to apply the bonding member and its manufacturing method of the present invention to such packages for semiconductor devices, and it is possible to obtain ceramic packages that are extremely reliable in terms of bonding strength and airtightness. Another method of metallizing the surface of a ceramic sintered body is to apply a mixed powder of manganese and molybdenum to the surface of an oxide ceramic such as alumina, and then heat it to a high temperature in a forming gas and sinter it. However, this method cannot be applied to carbide ceramics. JP-A-59-195590 discloses Fe, Ni, Cr,
At least one metal component among Mn,
A composition in which at least one component of C, Si, and B is mixed is placed on the surface of a nitride ceramic body in the form of powder or foil, and the composition is mixed in a non-oxidizing or weakly oxidizing atmosphere. Although it is described that materials can be melted, there is no mention of silicon carbide ceramics. As a metallization method for silicon carbide ceramics, JP-A-58-99184 discloses W, Mo, Ti,
A method is described in which powder such as Mn is applied and fired in a non-oxidizing atmosphere, but the firing temperature is
Since the temperature is higher than 140℃, the thermal stress during metallization is large and reliable metallized parts cannot be obtained. [Example] The present inventors applied various metal powders to the surface of silicon carbide ceramics and investigated the reaction state between the ceramics and the metals when heated to 1000°C in a non-oxidizing atmosphere. As a result, we discovered the following new phenomenon. That is, when applying metals of group a and group a of the periodic table of elements such as Ti, Zr, Nb, and V,
The reaction does not proceed at a heating temperature of 1000°C, and in order to cause a binding reaction, it is necessary to raise the heating temperature above 1000°C to near the melting point of the metal. but,
It has been found that when the heating temperature is raised to near the melting point, a thick layer of brittle compounds such as carbides and silicides of the metal is formed at the metallized interface, making it impossible to obtain sufficient metallization strength. Moreover, the thickness of the metallized layer formed by the metal powder applied to the surface of silicon carbide ceramics is
or the same thickness as the printed metal powder.
It became more than 10μm. Therefore, the ceramic was destroyed due to the thermal stress generated on the surface of the ceramic. When Group A and Group A metals such as Fe, Ni, Mn, and Co are coated, the bonding reaction with the ceramics proceeds excessively at a heating temperature of 1000°C, and the brittle silicide of the metals forms at the bonding interface. Alternatively, it has been found that the carbide layer and free carbon are formed so thick that sufficient metallization strength cannot be obtained. On the other hand, when applying Cr powder among Group A metals such as Cr, Mo, and W, a mixed layer of Cr silicide and Cr carbide is formed on the matrix of the ceramic.
Furthermore, it was found that a metal chromium layer was formed on the outside with a total thickness of less than 10 μm. This mixed layer of Cr silicide and Cr carbide and the Cr layer are strongly bonded to the ceramic, and their thickness is not affected by the thickness of the applied Cr powder, and when the heating temperature is 900 to 1300°C, the entire Cr layer is It was found that the film was extremely thin, with a thickness of 1 to 10 μm. Therefore, the thermal stress generated on the surface of the ceramic is also reduced, and the ceramic is not damaged by thermal stress, and the metallization strength is improved. When chromium powder is applied to the surface of silicon carbide ceramics and fired in a non-oxidizing atmosphere, a relatively thick unreacted Cr layer containing some chromium oxides such as Cr ₂ O ₃ is formed on the outside of the metallic chromium layer. be done. This unreacted chromium layer has a weak bonding force with the chromium metallized layer. By removing such an unreacted chromium layer before bonding the metal member to the chromium-metalized surface, it is possible to prevent it from affecting the bonding strength of the metal member. To remove this unreacted chromium layer containing chromium oxide, methods such as polishing, removal with a brush, honing, etc. may be used. In the present invention, among silicon carbide ceramics, metallized layers with particularly high strength were obtained using silicon carbide ceramics to which 1 to 2% by weight of BeO was added as a sintering aid. In addition, since the Cr metallized layer formed on the surface of the ceramic does not have sufficient brazing or solderability for joining with other metals or ceramics, a Cu, Ag, or Ni layer is provided on the surface of the chromium layer. Afterwards, it is desirable to join the metal or other ceramics by brazing. Applicable
To form a Cu or Ni layer on the surface of the Cr layer, methods such as electroplating, chemical plating, and vapor deposition sputtering can be used. The thickness of these layers is 3-8μm
It is desirable to do so. Furthermore, the Cr layer and Cu or
In order to improve the bonding state with the Ni layer, it is desirable to perform the diffusion treatment again at a temperature of 500°C to 800°C, but this can be omitted if brazing is performed in this temperature range. By forming a metallized film of chromium on the surface of silicon carbide ceramics using the above method and then bonding it to other metal members using a brazing filler metal, a bending strength of 20 kg/mm ² or more can be obtained, and the heat resistance is also 600°C or more. . The particle size of the chromium powder applied to the surface of silicon carbide ceramics is 100 μm or less, preferably
Desirably 50μm or less. For particle sizes larger than this,
As a result, there are likely to be parts of the ceramic surface that are not covered by the formed metallic chromium layer. In addition, the coating thickness of chromium powder is preferably 10 μm to 30 μm. If it is too small, the surface of the ceramic will not be covered with the metallic chromium layer, and if it is too large, the unreacted layer containing chromium oxide will increase, making it uneconomical. unfavorable to The chromium powder is preferably applied in the form of a paste together with a suitable paste agent. The time for heating the ceramic coated with chromium powder to 900°C to 1300°C is preferably 10 minutes or more and 1 hour or less. Note that if the firing temperature of Cr metallization is below 900°C, the Cr metallized layer will not be formed, and if the firing temperature is above 1300°C, the thickness of the Cr metallized layer will be 10 μm or more, and the Cr metallized layer will not form.
The strength of the metallized layer is extremely reduced. Silver, which is easily wetted by brazing, has a melting point higher than the brazing temperature, and has a small elastic modulus E (E = 7.7 x 10 ³ Kg) is used as a thermal stress relaxation material.
It is preferable to use copper (E=11×10 ³ Kgf ^/ mm ² ). Aluminum (E=7.0×10 ³ Kg
f/mm ² ), but in this case it is preferable to form a thin layer of nickel or copper on the surface. The thickness of the thermal stress relaxation material is preferably 0.1 mm or more because if it is too thin, the relaxation effect will be reduced and there will be problems with erosion due to brazing. Moreover, if the upper limit thickness is thicker than 1 mm, the thermal stress relaxation effect will be poor.
A thickness of 0.1 to 0.8 mm is preferred. The atmosphere during brazing may be any non-oxidizing atmosphere, such as an inert gas atmosphere, a reducing gas atmosphere, or a vacuum. It is desirable to use different atmospheres depending on the components of the brazing filler metal used.
For example, when using a eutectic brazing material containing 7% silver and 28% copper, any atmosphere may be used, but when using a silver brazing material containing Zn, Cd, etc., which have high vapor pressure, an inert atmosphere may be used. A gas atmosphere or a reducing gas atmosphere is desirable. An inert gas atmosphere or a mixed gas atmosphere of nitrogen gas and hydrogen gas is also effective. Example 1 1 mm thick with about 2 wt% BeO as sintering aid,
Cr powder made into a paste with dimethyl ethyl cellulose was applied to a thickness of approximately 1 mm on one side of a hot-pressed silicon carbide ceramic plate measuring 20 mm in length and width, and then fired at 1100°C for 30 minutes in an Ar atmosphere. After that, it was naturally cooled. As a result, a mixed layer of Cr silicide and Cr carbide with a thickness of approximately 3 μm is formed on the surface of the ceramic mother plate, a metal Cr layer is formed on top of this, and the outermost layer is an unreacted layer containing a portion of Cr oxide. A Cr layer was formed. Next, the unreacted Cr layer was removed using a knife to expose the chromium layer. Then, a Cu film of about 5 μm was formed on the Cr layer by electroplating. A silicon carbide sintered body having a metallized film formed by the above method and a stainless steel plate with a thickness of 1 mm and a width of 5 mm are joined by Ag brazing via a thermal stress relaxation material made of a Cu plate with a thickness of 500 μm and a width of 5 mm. did. After joining, a tensile test was performed and a tensile strength of 20 Kg/mm ² was obtained. Furthermore, as a result of a heat resistance test of this metallized portion, no decrease in bonding strength was observed up to 700°C. Example 2 2 mm thick with about 5 wt% AlN as sintering aid,
Cr powder made into a paste similar to that in Example 1 was applied to the entire surface of a hot-pressed silicon carbide ceramic plate measuring 20 mm in length and width to a thickness of about 0.5 mm.
This was baked at 1050° C. for 30 minutes in a vacuum of 10 ⁻⁴ torr, and then cooled naturally. As a result, a mixed layer of Cr silicide and Cr carbide with a thickness of about 5 μm is formed on the surface of the ceramic, and a metal Cr layer is formed thereon.
An unreacted Cr layer containing Cr oxide was formed as the outermost layer. Next, the unreacted Cr layer formed as the outermost layer is removed by polishing, and the metal on the ceramic surface is removed.
Approximately 5 μm of Ni was electroplated on the Cr layer. The silicon carbide ceramic sintered body having a metallized film formed by the above method and a stainless steel plate with a thickness of 1 mm and a width of 5 mm were silver soldered via a silver plate with a thickness of 500 μm and a width of 5 mm as a thermal stress relaxation material. ,
Pd-Ag solder was used as the silver solder, and the bonding was carried out at 900°C. After that, a tensile test was conducted and the result was approximately 30Kg/
A tensile strength of mm ² was obtained, and no decrease in bonding strength was observed up to 700°C. Example 3 The semiconductor device package according to the present invention was
This will be explained with reference to the drawings and FIG. The cooling substrate 1 is made of highly thermally conductive silicon carbide ceramics with a thickness of 1 mm, length and width of 15 mm, and containing 2% by weight of BeO as a sintering aid. Cr metallization with a width of 2 mm is applied along the outer edge of one side of the cooling substrate 1. formed a layer. The formation conditions were as follows: Cr powder with a particle size of 10 μm made into a paste with dimethyl cellulose was applied to a predetermined position to a thickness of about 30 μm, and this was coated with 1050 Cr powder in an Ar atmosphere.
℃ for 30 minutes and then allowed to cool naturally. Next, the outermost layer
The Cr oxide layer is removed by brush polishing, and the metal Cr
A Ni layer 3 of about 5 μm was formed on layer 2 by electroplating. The alumina ceramic frame 4 facing the cooling substrate 1 having a metallized film formed by the method described above has a three-layer structure, with wiring patterns 8 between the layers. The uppermost layer (referred to as the first layer) of the frame 4, which is joined to the cooling substrate 1, has an opening in the center sufficient to accommodate the semiconductor device, and the opening is successively formed in the second and third layers. is larger, and the wiring part 9 connected to the input/output pin 10 and the wiring pattern 8
There is. The wiring section 9 is bonded to the cooling substrate 1 by an Au--Si metallized layer 11 and is a connection terminal to an electrode section of a semiconductor device. A Mo--Mn metallized layer 5 and a Ni layer 3 are formed on the first layer surface of the frame 4 at positions that match the metallized portions of the cooling substrate 1. The cooling board 1 and the frame 4 were joined by silver brazing. The brazing method is 50μm silver solder (BAg-
7: 56wt%Ag-22wt%Cu-17wt%Zn-5
Weight % Sn) foil 7 and thermal stress relaxation material 6 (silver plate, oxygen-free copper plate) of a predetermined thickness are punched into a metallized pattern, and the silver solder foil 7, thermal stress relaxation material 6, and silver solder foil 7 are placed in this order on a cooling board. 1 and frame 4 in an N ₂ -10% H ₂ gas atmosphere with a flow rate of 5.5 l/min.
Brazing was performed by heating to 700-710℃. The cooling rate is
20℃/min up to 500℃, 5-10℃/min below 500℃
The mixture was cooled in the furnace to 150°C, and then naturally cooled to room temperature in the atmosphere. Next, we conducted a He leak test on the semiconductor package after brazing. A leak test was conducted before and after the thermal fatigue test, and the conditions were -50℃ to +150℃ for 1
The heat cycle was performed for 1000 cycles with one cycle time. Leak test pass line 1x
Table 1 shows the test results at 10 ^-8 atm・cc/s.

[Table] An LSI is bonded to the Au-Si metallized part 11 of the opening part of a package for a semiconductor device that has passed a thermal fatigue test, and the electrode part of the LSI and the wiring part 9 of the frame 4 are connected by a thin Al wire. It was sealed to prevent exposure to outside air. Further, a heat dissipating fin 12 made of silicon carbide ceramics was adhered to the upper surface of the cooling substrate 1 with a thermally conductive adhesive 13 to form a package for a semiconductor device. Example 4 Same cooling board 1 and frame 4 as used in Example 3
Table 2 shows the results of the He leak test after the fatigue test by thermal cycling of the joints fabricated using different thermal stress relaxation materials, brazing, and brazing conditions. In addition, the thickness of the thermal stress relaxation material is 500 μm, and the Ar
The flow rate is 8 l/min, and the degree of vacuum is 5 x 10 ^-5 torr.

【table】

〔Effect of the invention〕

As explained above, according to the present invention, the silicon carbide ceramic sintered body does not crack during the cooling process after brazing, and is also prevented from peeling off from the metallized layer, thereby improving reliability. A highly bonded member can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a package for a semiconductor device showing an embodiment of the present invention, and FIG. 2 is an enlarged view of section A in FIG. 1. 1...Cooling substrate, 2...Cr layer, 3...Ni layer,
4...Alumina ceramics frame, 5...Mo-
Mn metallized layer, 6... thermal stress relaxation material, 7...
Silver wax foil.

Claims (1)

[Scope of Claims] 1. A joining member between a silicon carbide ceramic sintered body having a metallized layer on the surface to be joined and another ceramic or metal, wherein the metallized layer is a mixed layer of chromium silicide and chromium carbide, A silicon carbide-based material having a three-layer structure including a chromium layer thereon and an outermost layer made of at least one of nickel and copper, and having a thermal stress relaxation material between the bonding surfaces with the other ceramic or metal. Ceramics joining parts. 2. A bonding member for silicon carbide ceramics according to claim 1, wherein the thermal stress relieving material is made of at least one of silver and copper. 3. A joining member of silicon carbide ceramics according to claim 1, wherein the thickness of the thermal stress relaxation material is 100 to 1000 μm. 4. The silicon carbide ceramic bonding member according to claim 1, wherein the other ceramic is made of alumina. 5. In claim 1, the mixed layer of chromium silicide and chromium carbide in the metallized layer and the chromium layer thereon are made non-oxidizing by coating the surface of the silicon carbide ceramic sintered body with chromium powder. 1. A bonding member for silicon carbide ceramics, characterized in that it is obtained by firing in an atmosphere and removing a layer containing chromium oxide formed as an outermost layer. 6. In claim 1, the silicon carbide-based ceramic sintered body contains beryllium oxide.
A bonding member for silicon carbide ceramics, characterized in that it contains ~2% by weight. 7. In a method for manufacturing a joining member formed by joining a silicon carbide ceramic sintered body having a metallized layer on the surface to be joined with another ceramic or metal, the step of forming the metallized layer includes sintering the silicon carbide ceramic A step of applying chromium powder to the body surface and then heating it in a non-oxidizing atmosphere to form a mixed layer of chromium silicide and chromium carbide, a chromium layer thereon, and an outermost layer containing chromium oxide, and removing the outermost layer. and thereafter, a step of coating with at least one of nickel and copper, and brazing the bonding surface between the metallized layer and the other ceramic or metal via a thermal stress relieving material. A method for manufacturing a silicon carbide ceramic bonding member. 8. The method for producing a silicon carbide ceramic bonding member according to claim 7, characterized in that heating is performed in the non-oxidizing atmosphere to a temperature of 900 to 1300°C. 9. The method of manufacturing a silicon carbide-based ceramic bonding member according to claim 7, characterized in that at least one of copper and silver is used as the thermal stress relaxation material. 10 In claim 8, the thickness is 100
A method for producing a silicon carbide-based ceramic sintered body, characterized by interposing a thermal stress relaxation material of ~1000 μm. 11. The method of manufacturing a silicon carbide ceramic bonding member according to claim 7, wherein the brazing is performed using silver solder.