JP2000226274A - Production of ceramic-metal conjugate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability in conjugation between ceramic and a metal by solder and produce a ceramic-metal conjugate at a low cost by absorbing an activated metal onto the surface of a ceramic substrate, heat-treating the surface and applying metal plating onto the surface on which the activated metal is applied. SOLUTION: The above ceramic substrate is preferably formed of one kind of compound selected from boron nitride, aluminum nitride, silicon nitride and alumina. One or more metals of Pd, Rh, Pt and Ru can be used as the activated metal. Heat treatment is preferably carried out at a temperature not lower than oxidation-starting temperature of the activated metal and is preferably carried out at a temperature not lower than 800 deg.C and not higher than it melting point when the activated metal is Pd. Heat treatment is carried out preferably under vacuum or in non-oxidative atmosphere of hydrogen, nitrogen, a hydrogen- nitrogen mixed gas, helium or argon. The metal plating is preferably electroless plating and a metal usable for plating includes Ni-P, Ni-B, Ni-Cu-P or Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic-metal joint used for a power module or the like.

[0002]

2. Description of the Related Art In order to use a high thermal conductive ceramic member for a power module, a metal plating which can be soldered to the surface is required. When importance is placed on solder durability, Ni plating is selected as metal plating. Ceramics are representative of members that are difficult to plate. As an inexpensive plating method, the ceramic surface is roughened by alkali etching or the like, Sn ions are adsorbed, and subsequently, metal Pd is replaced and precipitated in a palladium chloride solution to form a plating nucleus. A method of performing electrolytic Ni plating is known.

The electroless plating method is a method in which an activated metal is adsorbed on the surface of an inactive material such as a resin or ceramics to activate it, and the activated metal is plated. In this case, the activation metal and the plating metal are firmly adhered, but the adhesion between the activation metal and the ceramic is weak. Therefore, the ceramic surface is roughened to increase the mechanical coupling between the activated metal and the ceramic, thereby improving the adhesion by the anchor effect. Although some proposals for improvement of this method have been proposed, none of these proposals shows a range of how to increase the anchor effect, and has not achieved a highly reliable adhesion.

There is also a method represented by a tungsten metallization method for aluminum nitride ceramics. In this method, a tungsten paste is printed and dried on a ceramic green sheet before firing, and the ceramic and the tungsten paste are simultaneously fired at 1800 ° C. or more after degreasing heating. There is also a method of printing and firing a tungsten paste on ceramics which has been fired in advance on a white plate.

[0005] Since the ceramic surface is metallized with tungsten, it is called a tungsten metallization method. Thereafter, electroless Ni plating is performed, and then heat diffusion is performed to obtain a metal-plated ceramic substrate that is strongly Ni-plated on tungsten. In this method as well, the adhesion between tungsten and ceramics is due to the anchor effect.
By firing at a high temperature of 0 ° C., the ceramics and tungsten adhere firmly.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing an inexpensive ceramic-metal joined body having good durability in brazing such as Ag brazing. Another object of the present invention is to provide a method for manufacturing a ceramic-metal bonded body that can provide a metal-ceramic bonded body that is durable to a manufacturing process and a thermal cycle in a use environment.

[0007]

The present inventor used aluminum nitride as a ceramic substrate, adsorbed Pd on its surface, and performed a heat treatment at 800 ° C. in this state. Thereafter, electroless Ni-B plating was performed to obtain a ceramic-metal bonded body. Then, it was confirmed that the adhesion of the joined body was increased. The present invention has been completed by using a phenomenon in which a strong bonding force acts between the ceramic base material and the activation metal by performing an appropriate heat treatment in a state where the activation metal is adsorbed.

That is, in the method for producing a ceramic-metal bonded body of the present invention, an adsorption step of adsorbing an activated metal on the surface of a ceramic substrate and a heat treatment of heat-treating the ceramic substrate adsorbed with the activated metal are provided. A metal plating step of performing metal plating on the surface of the activated metal to which the heat-treated activated metal has been adsorbed. According to the method of the present invention, since the adhesion between the activated metal and the ceramic substrate is improved, a ceramic-metal bonded body having high adhesion can be manufactured.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a ceramic-metal bonded body according to the present invention includes an adsorption step, a heat treatment step, and a metal plating step. As a ceramic base material constituting one of the ceramic-metal bonded bodies of the present invention, a base material formed of one of boron nitride, aluminum nitride, silicon nitride, and alumina can be used.

The adsorption step of the present invention is a step of adsorbing the activated metal on the surface of the ceramic substrate, and a conventionally known adsorption step can be employed as it is. Specifically, the activation metal can be adsorbed simply by immersing the ceramic substrate in a solution in which the activation metal is dissolved. In addition, by sensitizing the surface of the base material with a solution containing Sn ions as is conventionally known, the activation metal can be more reliably adsorbed.

As the activating metal, one or more of conventionally known palladium, rhodium, platinum and ruthenium can be used. The heat treatment step is a treatment for increasing the adhesion between the adsorbed activated metal and the ceramic base material. When palladium is used as the activating metal, the heat treatment temperature is preferably set to 800 ° C. or higher. In order to analyze a phenomenon in which the adhesion is improved by the heat treatment, a sample of an aluminum nitride ceramics base material on which a Pd catalyst was adsorbed was prepared and subjected to XPS analysis. The Pd layer without heat treatment was atomic Pd, but the Pd layer heat-treated at 800 ° C. had Pd near the interface with aluminum nitride.
Was oxidized to Pd2 +. It is supposed that the oxidation of the activated metal is a factor that enhances the adhesion between the activated metal and the ceramic substrate.

Therefore, in the heat treatment step, the heat treatment is preferably performed at a temperature equal to or higher than the oxidation start temperature of the activated metal. In the case of Pd, the heat treatment is preferably performed at a temperature of 800 ° C. or more, more specifically, a temperature of 800 ° C. or more and a melting point or less. The heat treatment atmosphere is vacuum, hydrogen, nitrogen, hydrogen-nitrogen mixture, helium,
Alternatively, it is preferably performed in a non-oxidizing atmosphere such as argon. The amount of oxygen required for the oxidation of the activated metal is very small,
Oxygen of the oxide constituting the ceramic substrate may be used in some cases.

The metal plating step is a step of plating a metal, such as Ni, on the surface of the ceramic base material on which the activated metal has been adsorbed and which has been heat-treated. This metal plating step is preferably electroless plating, but is not limited to electroless plating. PVD and CVD plating methods, and electrolytic plating methods can also be employed if the active metal is adsorbed thick enough to be energized.

The metals that can be used in the metal plating step include Ni, Cu, etc., more specifically, Ni-P, Ni-B,
Ni-Cu-P, Cu, etc. can be adopted. If the cost is neglected, noble metal plating such as Au, Ag, Pd, and Rh is also possible. Before the adsorption step in the method of the invention,
It is preferable to perform a roughening step of roughening the surface of the ceramic base material. As the surface roughening method, a conventional surface roughening method can be adopted. Specifically, the surface of the ceramic substrate can be mechanically polished to form fine irregularities, or can be roughened by chemical etching.

Further, an activated metal plating step of plating the same or an alloy of the activated metal on the activated metal adsorbed in the adsorption step may be further performed.
By increasing the amount of the activated metal deposited per unit area, the adhesion between the activated metal and the ceramic substrate is further improved. The metal plating surface obtained after the metal plating step has an extremely high bonding property to the brazing material. Therefore, the metal plate can be easily brazed to the metal plating surface. For example, a copper plate having a predetermined thickness according to the purpose can be joined by brazing.

The brazing material used in the brazing step may be Ag brazing or solder. Preferably, the brazing material has a thickness of 40 μm or less. Moreover,
More preferably, the brazing material has a thickness of 20 μm or less.
When the thickness of the brazing material is greater than a predetermined thickness, that is, 40 μm or less, for example, when a large strain is applied between two members joined by the brazing material due to thermal stress due to different thermal expansions,
The thin brazing material plastically deforms and absorbs the distortion. That is, the brazing material layer functions as a strain relaxation layer.

When the thickness of the layer exceeds 40 μm, the thermal stress caused by the difference in thermal expansion coefficient between the ceramic substrate and the metal plate causes
The bending moment that deflects the ceramic-metal joint increases, and the warp that becomes concave toward the surface side excessively occurs in the joint. Further, when a joining material in which metal plates are joined to both surfaces of a ceramic base material, which is a general configuration of an actual product, is cooled at a cooling rate of 7 to 35 ° C./min in a continuous furnace, the layer thickness exceeds 40 μm. Cracks occur in the ceramics.

FIG. 1 shows a joined body in which a Cu plate is joined to one surface of an aluminum nitride substrate having a thickness of 0.635 mm and plated with Ni having a thickness of 3 μm by using an Ag braze; FIG. 10 is a view showing a result of measuring concave warpage of the Cu plate surface when the thickness of the Ag braze is changed in a joined body in which a Cu plate is joined using an Ag braze having a Cu intermediate layer on one surface of the Cu plate. . here,
The concave warpage of the Cu plate surface was measured by measuring the radius of curvature of the Cu plate surface when a 0.25 mm thick Cu plate was joined to one surface of the aluminum nitride substrate with an Ag braze. The thickness of the Ag brazing layer is the thickness of one Ag brazing layer as shown in the lower right circle of FIG. Ag wax-C
The thickness of the u-Ag brazing layer is as shown in the upper right circle of FIG.
The total thickness of the Ag brazing layers on both sides of the u layer and the Cu layer is shown, and the thickness of each Ag brazing is constant at 20 μm.

As can be seen from FIG. 1, as the thickness of the Ag brazing becomes larger, the radius of curvature becomes shorter, as can be seen from the radius of curvature of the joined body joined with only the Ag brazing. The radius of curvature can be reduced by
In other words, this indicates that the warpage of the Cu plate has increased. In addition, it can be seen that the joined body joined by the Ag brazing having the Cu intermediate layer has a larger radius of curvature than that of the joined body joined by only the Ag brazing, and the warpage of the Cu plate is smaller.

The brazing material functioning as the strain relief layer is a soft material having a low melting point, such as Ag brazing or solder. Here, the term "soft" means that the temperature is lower than the recrystallization temperature of a typical Ag-Cu binary Ag wax, which is a typical Ag wax composition, particularly 170 ° C. or lower which is assumed in a thermal cycle depending on the use environment.
It means that the g-Cu binary Ag wax exhibits elongation higher than or equal to the elongation due to plastic deformation in a tensile test. By having such a strain relaxation layer between the ceramic base material and the metal plate, the ceramic-metal joined body can relieve a bending moment caused by thermal stress due to cooling after high-temperature joining and thermal cycling in a use environment. .

As a method of directly joining a metal plate without applying a metal plating which can be soldered or brazed to a ceramic base material, a Cu plate is used for the metal plate, and a eutectic liquid phase of Cu and O is used. Ti-Ag-
There is an active metal method of joining a Cu plate using an active metal brazing represented by a Cu system. However, in these conventional methods,
Since the eutectic layer of Cu and O or the bonding layer in which Ti is diffused is hard, the thermal stress generated due to the difference in heat shrinkage between the ceramic base material and the metal plate during cooling after bonding cannot be reduced.

In a power module requiring a high current circuit, the current circuit bonded to the ceramic substrate is desirably a Cu plate having a low specific resistance and a high thermal conductivity.
However, in the above conventional method, there was a problem in the thermal cycling resistance as a result. Further, there is a method of directly joining a ceramic base and a metal plate, and using Al for the metal plate.
According to this method, the strain relaxation effect of Al itself is large, and there is no problem in the life of the joint between the ceramic substrate and Al. However, since cooling after joining causes irregularities on the Al surface, polishing of the Al surface is necessary after joining. Also, since Al is deformed by a thermal cycle in a use environment, there is a danger that the Al surface may be raised at a soldered portion under the chip or at a bonding portion where there is a connection by Al wire bonding. Furthermore, since Al has a higher specific resistance than Cu, it is not a material that satisfies the demands for higher output, higher speed, and smaller size of power modules. Choosing Al as a current circuit material is a compromise. It can be said that it is a typical choice.

[0023]

The present invention will be described below in detail with reference to examples of the present invention. (Example 1) 0.635-thick ceramic substrate
A sintered aluminum nitride white plate having break lines at intervals of 17 mm and 30 mm in length and width in mm was used. First, the aluminum nitride white plate was degreased.
The degreasing treatment was performed using a degreasing agent (50 g / l A-screen A-
220, manufactured by Okuno Pharmaceutical Co., Ltd.) at a temperature of 60 ° C. for 5 minutes. Thereafter, the aluminum nitride white plate was washed with water to remove the degreasing agent on the surface.

Next, the surface of the aluminum nitride white plate was roughened using a surface roughening agent. 5mo as surface roughening agent
Heated to 60 ° C. using 1 / l sodium hydroxide solution. The aluminum nitride white plate was roughened by immersing it in this sodium hydroxide solution for 25 minutes.
The aluminum nitride white plate was washed with water to remove the surface sodium hydroxide solution, and subsequently dried with warm air. Thereby, many pores are formed on the surface of the aluminum nitride white plate, and the surface roughness (Rz) of the aluminum nitride white plate is set to 6 μm.
And

Next, as preparation for surface activation, a resist film was screen-printed on a portion of the surface of the aluminum nitride white plate where no nickel plating pattern was formed.
As a result, unnecessary portions of the plating are masked, and the subsequent surface activation treatment can be performed only on the necessary portions. The resist film used was Nobuco Mask TC580
(Manufactured by Sannobuco) was used. After printing the resist, the aluminum nitride white plate was heated to 120 ° C. to cure and dry the resist film. In this embodiment, in order to measure the adhesion force later, the periphery of the break line on the upper surface (the surface with no break groove) of the aluminum nitride white plate is covered with a resist film, and the center portion and the lower surface of the break line on the upper surface (with the break groove) Surface) The whole surface was left.

Next, a non-masked portion of the surface of the aluminum nitride white plate was activated by a general method of adsorbing an activation metal on the surface of the nonconductor. That is, the first Sn ions were adsorbed on the surface of the aluminum nitride white plate using a sensitivity-imparting agent (100 ml / l TMP sensitizer, Okuno Pharmaceutical). After washing with water, the activating agent (50 ml /
l TMP activator, Okuno Pharmaceutical)
d was substituted and precipitated, and then washed with water.

This sensitivity imparting and activating treatment is a treatment for 30 seconds to 3 minutes at room temperature, and is repeated several times depending on the material and surface condition of the substrate. Next, the activated aluminum nitride white plate was dried with hot air to remove the masking resist. Thereafter, a heat treatment step was performed. In this heat treatment step, the activated aluminum nitride white plate is treated with hydrogen-
The heating is performed at 900 ° C. for 10 minutes in a nitrogen mixed gas stream. Next, the aluminum nitride white plate was subjected to electroless nickel plating. For the electroless nickel plating, a commercially available electroless Ni-B plating solution capable of forming a film having a boron content of about 1% was used. This plating solution is pH 6.3, 65 ° C
The aluminum nitride white plate heat-treated after activation was immersed to form a 3 μm Ni—B film. Further, the electroless nickel-plated aluminum nitride white plate was divided along the break line.

As a result, 3 μm Ni-B
An aluminum nitride substrate having a film, that is, the ceramic-metal bonded body of Example 1 was manufactured. For comparison, the same aluminum nitride white plate as in Example 1 was used without performing the heat treatment performed in Example 1, and the same degreasing treatment, surface roughening treatment, formation of a resist film, sensitivity imparting treatment, and activation treatment were performed. , An aluminum nitride substrate subjected to substitution precipitation of metal Pd, removal of a resist film, electroless nickel plating, and division at a break line, that is, a ceramic-metal bonded body of a comparative example was manufactured.

Using the ceramic-metal bonded body of Example 1 and the ceramic-metal bonded body of the comparative example, the adhesion between each aluminum nitride and the plating film formed of the Pd and Ni-B films was measured. did. FIG. 2 shows a method for measuring the adhesion of the plating film. Test samples were made as follows. First, the entire surface of the electroless nickel plating film 10 joined to the upper surface of the aluminum nitride substrate 3 of each of Example 1 and the comparative example was nickel-plated (not shown), and was formed of 0.5 × 8 × 11 mm 42. % Ni-Fe alloy plate 1
2 was joined with Sn-Pb solder having a melting point of 300 ° C. The nut 9 was joined to the center of the upper surface of the joined 42% Ni—Fe alloy plate 12 with the solder 4 having a melting point of 183 ° C.

Thereafter, a 4 × 30 × 60 mm Al plate 11 was bonded to the electroless nickel plating film 10 on the lower surface side of the aluminum nitride substrate 3 with the adhesive 2 to prepare a test sample.
In the test, as shown in FIG. 2, both ends of the Al plate 11 of the test sample where the aluminum nitride substrate 3 was not bonded were pressed by the fixture 8 as shown in FIG. 2. Then, a stainless steel hook 13 was passed through the nut 9 of the test sample. A tensile test was performed in this state. That is, the hook 13 was pulled upward. The nut 9 is pulled by the hook 13 and is finally peeled off the aluminum nitride substrate 3. The determination of the adhesion was obtained from the breaking strength at this time. In addition, as a fracture site, fracture in aluminum nitride,
Observation was made by classifying into plating peeling and solder joint breakage.

As a result of the test, the adhesion of the test sample of Example 1 was 90 kgf, and the broken portion was peeling of plating. Further, the adhesion of the test sample of the comparative material was 40 kgf, and the fracture site was peeling of the plating. From these test results, it can be seen that, by performing the heat treatment after adsorbing the activated metal, the adhesion is improved 2.25 times as compared with the case where the heat treatment is not performed. That is, the heat treatment after the adsorption of the activated metal greatly contributes to the increase in the adhesion. (Example 2) 0.635-thick ceramic base material
A sintered aluminum nitride white plate having break lines at intervals of 17 mm and 30 mm in length and width in mm was used. This aluminum nitride white plate was degreased in the same manner as in Example 1, and then etched with a sodium hydroxide solution. Surface roughness (Rz) of the obtained aluminum nitride white plate
Was 6 μm.

Next, in the same manner as in Example 1, a masking resist is screen-printed and heat-cured as a preparation for surface activation, followed by a first Sn ion adsorption and Pd substitution treatment for activated metal adsorption. Repeated times. Subsequently, plating of an activated metal was performed. That is, on the aluminum nitride white plate on which metal Pd is substituted and precipitated and adsorbed,
Electroless palladium plating was performed at 0.3 μm, and the substituted and precipitated metal Pd was reinforced with the same kind of metal.

The plating solution used was Muden Noble PD
(Manufactured by Okuno Pharmaceutical Co., Ltd.), pH 6.2, adjusted to 55 ° C., immersed in the aluminum nitride white plate for 7 minutes,
m palladium plating film was formed. Thereafter, the masking resist was removed by hot air drying. Next, a heat treatment was performed on the aluminum nitride white plate plated with the activation metal. That is, this aluminum nitride white plate was heated at 900 ° C. for 10 minutes in a hydrogen-nitrogen mixed gas flow. An aluminum nitride white plate prepared in the same manner and plated with Pd was placed in a vacuum for 120 hours.
Heat at 0 ° C. for 2 hours. Through the above steps, an aluminum nitride substrate obtained by adsorption, plating and heat treatment of two types of activated metals having different heat treatment conditions was obtained.

Next, using these two types of aluminum nitride substrates, electroless nickel plating was performed in the same manner as in Example 1 to form a 3 μm Ni—B film. Further, the aluminum nitride substrate was divided along the break line. As a result, a ceramic-metal joined body, which was two kinds of aluminum nitride substrates subjected to the different heat treatments in Example 2, was obtained.

Next, the adhesion between these two types of ceramic-metal bonded bodies was measured in the same manner as described in Example 1. The adhesion of the ceramic-metal bonded body of Example 2 which was heat-treated at 900 ° C. was 90 kgf, and the destruction was peeling of plating. The adhesion of the ceramic-metal bonded body of Example 2 which was heat-treated at 1200 ° C. was 180 kgf.
And the failure was a break in the solder joining the nuts.

From Example 2, it was clarified that the higher the heat treatment at 1200 ° C., the higher the adhesion strength. Example 3 In Example 2, it was found that a higher heat treatment temperature improved the adhesion, so in this example, the relationship between the heat treatment temperature and the adhesion was examined.

Six kinds of ceramic-metal joints were prepared in exactly the same manner as in Example 2 except that only the heat treatment temperature in Example was changed. The heat treatment temperature is 600 ° C, 800
℃, 1000 ℃, 1100 ℃, 1200 ℃ and 1250
° C. Note that the heat treatment atmosphere was vacuum in all cases and the heat treatment time was 2 hours. As a reference example, the same ceramic-metal joined body as the reference example of Example 1 was also prepared.

Next, in Example 1, a total of seven types of ceramic-metal bonded bodies, that is, the six types of ceramic-metal bonded bodies of Example 3 and the one type of ceramic-metal bonded body of Comparative Example, were used. The adhesion was measured in the same manner as described above. The results are shown in FIG. The results show that at 600 ° C. the adhesion is slightly higher, 800 ° C., 1000 ° C. and 1100 ° C.
As the temperature increased, the adhesion increased, and at a temperature of 1100 ° C. or more, the fracture site changed from peeling of plating to fracture in the solder joining the nut.

In order to analyze the phenomenon of the improvement of the adhesion due to the heat treatment, the Pd in the adsorbed state before the heat treatment step in Example 1 was analyzed.
And XPS analysis of Pd after heat treatment. For the palladium after the heat treatment, the aluminum nitride white plate before the heat treatment in
Heat-treated at 0 ° C for 10 minutes, and surface X
PS analysis was performed. As a result, it was found that unheated Pd was present in an atomic state. On the other hand, it was found that Pd heat-treated at 800 ° C. was oxidized to +2 valence.

Further, Pd of 0.3 μm was deposited on another aluminum nitride white plate of Example 1 under high vacuum. next,
While maintaining a high vacuum, it was heated to 800 ° C. and heat-treated for 10 minutes. Next, Pd is sputter-etched, and XP
S analysis was performed, and analysis was continued up to the vicinity of the interface between the aluminum nitride and the Pd layer. As a result, the surface of the deposited Pd becomes atomic P
However, it was found that Pd near the interface between the aluminum nitride and the Pd layer was oxidized to +2 valence.

From this, it is considered that the increase in adhesion due to the heat treatment is due to oxidation of Pd near the interface between the aluminum nitride and the Pd layer. As a substance that oxidizes Pd, a sintering aid of aluminum nitride, a composite oxide of sintering aid metal and aluminum, or remaining first Sn ions adsorbed before the Pd substitution treatment can be considered. In the former case, there is a possibility that the aluminum nitride and the Pd layer are reactively diffused. Even in the latter case, it can be inferred that the affinity between the aluminum nitride and the Pd layer is improved.

(Embodiment 4) In this embodiment, the aluminum nitride substrate obtained by adsorbing, plating and heat-treating the activated metal of Example 2 was used, and a Cu plate was further joined by an Ag braze. A joined body was manufactured. (Production method of Example 4) Aluminum nitride of Example 4
The method for producing the Ag braze-Cu joint is described below. First,
In the same manner as in Example 2, metal Pd was placed on an aluminum nitride white plate.
, And electroless palladium plating is further carried out with 0.1.
3 μm, then heated at 1200 ° C. for 2 hours in a vacuum, and a 3 μm Ni—B film was formed by electroless plating. Next, the image is divided along the break line, and the 1200
Thus, an aluminum nitride substrate heat-treated at a temperature of ℃ was obtained.

Next, 0.25 mm Cu plate / (20 μm Ag brazing / 50 μm Cu foil / 20 μm Ag) was added to the carbon jig.
Row) / aluminum nitride substrate / (20 μm Ag row /
50 μm Cu foil / 20 μm Ag wax) /0.25 mmC
u-plates are sequentially laminated, a weight of 200 g is placed, and H2
-N2 (Hydrogen-Nitrogen) mixed atmosphere, heated to 840 ° C to melt-bond Ag braze to form aluminum nitride-Ag
A wax-Cu joint was manufactured. Finally, electroless Ni-P plating was applied to the surface of the Cu plate forming the surface of the aluminum nitride-Ag braze-Cu joint to a thickness of 4 µm. The obtained aluminum nitride-Ag braze-Cu joint had a surface warpage of 6 μm / 30 mm.

(Example 5) This example is an aluminum nitride-Ag braze-Cu joint, except that the heating method of the Ag braze is 840 ° C in vacuum for 20 minutes.
It was manufactured in the same manner as described above. Here, after melting and joining the Ag braze in a vacuum furnace, the Ag braze is cooled to room temperature in the furnace as it is,
The cooling rate at 450 ° C. or lower was 3.2 ° C./min. In addition, the obtained aluminum nitride-Ag brazing-Cu joined body had a surface warpage of 6 μm / 30 mm as in Example 4.
Met.

Example 6 The joined body of Example 6 was manufactured in the same manner as in Example 4 except that the joined body of Example 4 did not have the intermediate layer made of copper foil. Was. That is, the changed point is (20 μm Ag wax / 50 μm Cu foil / 2
This is the point that the laminated Ag wax of (0 μm Ag wax) is replaced with a single-layer Ag wax of (20 μm Ag wax).

(Evaluation) A thermal cycle test was performed to evaluate the joined bodies of Examples 4, 5 and 6.
The thermal cycle test is a test for measuring the bonding strength of the substrate when the thermal cycle is applied up to 20,000 cycles, with 3 minutes at 125 ° C. and 3 minutes at −40 ° C. as one cycle. The measuring method of the joining strength is as follows. A sample in which an M5 size nut is joined by soldering to the surface of the joined body of Example 4, Example 5, and Example 6 is prepared, and the nut portion of the sample is pulled upward. The measurement was performed by measuring the strength at the time of breaking. The state of destruction was also observed. And
A stainless steel hook was passed through a nut of the test sample, and a tensile test was performed in this state. That is, by pulling the hook upward, the nut is pulled by the hook, and eventually comes off from the surface of the joined body. The joining strength was determined based on the breaking strength at this time. In addition, fracture sites were observed by classifying into fracture in the aluminum nitride base material and fracture in the solder joint.

(Results) In the joined body of Example 4, the value of the joining strength when the number of cooling / heating cycles was 0 was 194 kgf, and at this time, the solder joint of the nut was broken. The joined body of Example 4 has a cooling / heating cycle number of 1,000,
2000, 3000, 5000, 10,000, 2000
At any cycle number of 0, the bonding strength is 180.
kgf or more, and the destruction was both at the solder joint of the nut.

Next, the joined body of Example 5 had a joint strength of 193 kgf when the number of cooling / heating cycles was 0. At this time, the joint of the nut was destroyed. The joined body of the fifth embodiment is similar to the joined body of the fourth embodiment,
Regardless of the cycle number of 10010000 or 20000, the bonding strength was 180 kgf or more, and the state of destruction was both at the solder joint of the nut.

On the other hand, in the joined body of Example 6, the value of the joining strength when the number of cooling / heating cycles was 0 was 201 kgf, and at this time, the solder joint of the nut was broken.
The joined body of Example 6 has a cycle number of 1000, 2
000, 3000, the joint strength is 180 kgf
As described above, both of the fractures were fractures at the solder joints of the nuts. However, in 5000 cycles, the joint strength was 90 kgf, and the fractures were such that the aluminum nitride substrate was cracked.

As a comparative example, an aluminum nitride-Ag braze-Cu joint was manufactured using an aluminum nitride substrate manufactured by using a tungsten metallization method. This aluminum nitride substrate is commercially available and has a thickness of 0.6
The tungsten layer formed on both surfaces of 35 mm aluminum nitride was 15 μm, and a 3 μm Ni—B film was formed on the tungsten by electroless plating.

Aluminum nitride-Ag wax-C of comparative example
The u-joined body was prepared as described in the column of “Production method of Example 4” in the section “Next, 0.25 mm Cu plate / (2
(0 μm Ag wax / 50 μm Cu foil / 20 μm Ag wax)
/ Aluminum nitride substrate / (20 μm Ag wax / 50μ
mCu foil / 20 μm Ag braze) /0.25 mm Cu plate were sequentially laminated, and a weight of 200 g was placed thereon, followed by H2-N2
The mixture was heated to 840 ° C. in a mixed atmosphere to melt-bond the Ag braze to produce an aluminum nitride-Ag braze-Cu joint. ".

The aluminum nitride-Ag braze-Cu joint was manufactured, and finally, the aluminum nitride-Ag braze-Cu joint was manufactured.
Electroless Ni- is applied to the surface of the Cu plate forming the Cu joint surface.
P plating was applied to a thickness of 4 μm. The aluminum nitride-Ag braze-Cu joint of the comparative example had a surface warpage of 20 μm / 30 mm, and was then subjected to a thermal cycle test.

The value of the bonding strength when the number of cooling / heating cycles is 0 is 1
The weight was 82 kgf. At this time, the solder joint of the nut was broken. However, when the number of cycles is 500, it becomes 170 kgf, and when it becomes 1000 cycles, it becomes 60 kgf.
The state of destruction was such that the aluminum nitride substrate was cracked. In addition, in 3000 cycles, at the time when the aluminum nitride substrate was taken out of the thermal cycle tester, the aluminum nitride substrate had already been torn at the center in the thickness direction, and the bonding strength could not be measured.

From the above, the joined bodies of Examples 4 and 5 have sufficient joining strength even in a long-term 20,000-cycle deterioration test, and are far more than the comparative example similarly manufactured by the tungsten metallization method. It turned out that it was excellent in cold-heat resistance. Further, the joined body of Example 6
In the 00 cycle, the strength was halved, but there was no strength decrease until 3000 cycles.

(Embodiment 7) In the evaluation of the embodiments 4, 5, and 6, the target value of the durability was 3000 cycles of cooling and heating. The target value of the durability is based on the assumption that the engine room is further mounted in a vehicle-mounted application.
The target level is 10 times or more the durability of the conventional method such as the joining by the eutectic liquid phase and the active metal method. However, in the evaluations of Examples 4 and 5 above, the bonding strength did not decrease even in a long inferior test of 20,000 cycles.

Therefore, a more severe test was conducted to try to grasp the limit value of the cooling / heating cycle. As the means, a method of increasing the thickness of the Cu plate to be joined was selected. When the Cu plate becomes thicker, thermal stress applied to the aluminum nitride substrate during cooling after joining increases. That is, the joined body of this embodiment is an aluminum nitride-Ag braze-Cu joined body,
The thickness of the Cu plate which the joined body had on both sides was 0.25
mm, both 0.3 mm, and both 0.5 m
Except having changed to m, it manufactured like Example 5.

(Manufacturing Method of Embodiment 7) A manufacturing method of an aluminum nitride-Ag braze-Cu joint in this embodiment will be described below. First, in the same manner as in Example 2, a metal Pd was substituted and deposited on an aluminum nitride white plate, and electroless palladium plating was performed thereon at 0.3 μm.
After heating for an hour, a 3 μm Ni—B film was formed by electroless plating. Next, the substrate was divided along a break line, and an aluminum nitride substrate heat-treated at 1200 ° C. as in Example 2 was obtained.

Next, a Cu plate / (20 μm
Ag wax / 50 μm Cu foil / 20 μm Ag wax) / aluminum nitride substrate / (20 μm Ag wax / 50 μm Cu)
Foil / 20 μmAg wax) / Cu plate in order,
g weight, and heated at 840 ° C. for 20 minutes in a vacuum to melt-bond the Ag braze. Then, it is cooled as it is in a furnace to room temperature, and a cooling rate of 450 ° C. or less is
in. Here, the thicknesses of the two Cu plates were the same, and the thickness of the Cu plates was changed to two levels of 0.3 mm and 0.5 mm to produce an aluminum nitride-Ag braze-Cu joint. Finally, these two types of aluminum nitride-A
Electroless Ni-P plating was applied to the surface of the Cu plate of the g-Cu-Cu joint to a thickness of 4 μm.

(Evaluation) Similar to the evaluation of Examples 4, 5, and 6, a cooling / heating cycle test was also performed on Example 7. (Results) Regarding the joined body of Example 7, cold and
The cycle was evaluated. In Example 7, the joined body of the Cu plate having a thickness of 0.3 mm exceeded the cold / hot cycle of 5,000 cycles,
At 180 kgf or more up to the zero cycle, the state of destruction was that the solder joint of the nut was broken. Further, the joined body having a Cu plate thickness of 0.5 mm is 1 unit up to 3000 cycles of cooling and heating.
At 80 kgf or more, the solder joint was destroyed.
In the 0 cycle, the aluminum nitride substrate cracked at 50 kgf, and in the 10000 cycle, the aluminum nitride substrate had already been torn at the center of the aluminum nitride substrate when it was taken out of the thermal test machine. Therefore, in Example 7, the Cu plate thickness was 0.1 mm.
Even under the extremely strict condition of 5 mm, it satisfies 3000 cycles of cooling and heating, which is the target value of durability assuming that it is mounted in an engine room for in-car use.

The aluminum nitride substrate of the present embodiment, which is a ceramic-metal bonded body, uses aluminum nitride having high thermal conductivity as ceramics, and thus is useful as an insulating heat sink for power modules and the like.
A substrate that is less expensive and has less warpage than an aluminum nitride substrate formed by a tungsten metallization method, which is a conventional technique, can be provided, and has excellent adhesion of a plating film. Further, the joined body composed of the aluminum nitride-Ag braze-Cu plate of the present embodiment, that is, the ceramic-metal joined body,
It is useful as a substrate for a high current circuit having an insulating property of a power module. In addition, it is resistant to cooling and heating cycles and can be used in harsh environments such as engine rooms of automobiles. As an example of use, an inverter module having a fin made of aluminum attached to the back surface side can be cited.

[0061]

According to the production method of the present invention, after the adsorption step,
There is a special feature in performing the heat treatment. The activated metal adsorbed by this heat treatment is firmly bonded to the ceramic substrate. The connection between the activated metal and the plating metal formed in the subsequent metal plating step is a bond between the metals and the bonding strength is strong. Therefore, ceramics that can be produced by the present invention
Any bonding with the ceramic base material, the activated metal, and the plated metal constituting the metal bonded body becomes strong.

Further, a metal plate, a lead wire and the like can be easily joined on the plated metal by using solder or the like. That is, a metal-plated ceramic having strong plating adhesion can be obtained by the method of the present invention. This method is less expensive than the tungsten metallization method, which has a complicated process. Also, unlike the tungsten metallization method, since a white plate with a small warp is used as the ceramic base material, an active metal P having a thickness of about 0.3 μm is further used.
Since the heat treatment is performed in a state where d is adsorbed or adsorbed and plated, it is possible to provide a substantially flat ceramic-metal joined body in which the warpage in a white plate state is preserved.

Further, this ceramic-metal bonded body facilitates low-melting-point metal bonding of a soft material such as Ag brazing or solder shown in this embodiment. That is, bonding of a metal plate such as a Cu plate is facilitated, and a hard bonding layer is not formed unlike the conventional eutectic liquid phase bonding of Cu and O or the active metal method. As a result, it is possible to provide a ceramic-metal joined body in which a metal plate is joined, which is excellent in resistance to thermal cycling.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a strain relaxation layer used for bonding and a radius of curvature of a ceramic-metal joined body having the strain relaxation layer.

FIG. 2 is a cross-sectional view illustrating an outline of a measuring method for measuring a bonding force of bonding.

FIG. 3 is a diagram showing a relationship between a heat treatment temperature of an activated metal adsorbed and an adhesion strength of a bonding obtained.

[Description of Signs] 2 ... Adhesive 3 ... Aluminum nitride substrate 4 ... Solder 8 ... Fixing tool 9 ... Nut 10 ... Nickel plating film 11 ... Aluminum plate 12 ... Ni-Fe alloy plate
13 ... hook

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C23C 18/16 C23C 18/16

Claims (18)

[Claims] 1. An adsorption step for adsorbing an activated metal on the surface of a ceramic substrate, a heat treatment step for heat-treating the ceramic substrate on which the activated metal has been adsorbed, and the heat-treated activated metal adsorbed on the ceramic substrate. A metal plating step of performing metal plating on the bent surface. 2. The method for producing a ceramic-metal joined body according to claim 1, further comprising a roughening step of roughening the surface of the ceramic base before the adsorption step. 3. The method according to claim 1, further comprising an activation metal plating step of plating the activation metal after the adsorption step. 4. The method for manufacturing a ceramic-metal joined body according to claim 1, wherein the heat treatment is performed at a temperature equal to or higher than an oxidation start temperature of the activated metal. 5. The method according to claim 1, wherein the metal plating step is an electroless plating step. 6. The method according to claim 1, wherein the ceramic substrate is a substrate formed of one of boron nitride, aluminum nitride, silicon nitride, and alumina. 7. The method according to claim 1, wherein the activating metal is at least one selected from palladium, rhodium, platinum, and ruthenium. 8. The method according to claim 1, wherein the activating metal is palladium, and a heat treatment temperature in the heat treatment step is 800 ° C. or more. 9. The method according to claim 8, wherein the activating metal is palladium, and the heat treatment temperature in the heat treatment step is 800 ° C. or higher and lower than the melting point of palladium. 10. The activated metal is palladium,
The method for producing a ceramic-metal joined body according to claim 9, wherein palladium or a palladium alloy is further plated as an activating metal after the adsorption step. 11. The method according to claim 1, wherein the heat treatment step is performed in a non-oxidizing atmosphere such as vacuum, hydrogen, nitrogen, a hydrogen-nitrogen mixture, helium, or argon. 12. The method according to claim 12, wherein the metal plating step comprises the steps of:
2. The method for producing a ceramic-metal joined body according to claim 1, wherein the ceramic-metal joined body is electroless plating of iB, Ni-Cu-P or Cu. 13. The method according to claim 1, further comprising a brazing step of brazing a metal plate to a metal plating surface obtained after the metal plating step. 14. The method according to claim 13, wherein the brazing material used in the brazing step is one of Ag brazing and solder. 15. The method according to claim 14, wherein the brazing material has a thickness of 40 μm or less. 16. The method according to claim 14, wherein the brazing material has a thickness of 20 μm or less. 17. The brazing material according to claim 1, wherein the brazing material has one layer of Cu foil, and has a brazing foil on both sides of the Cu foil.
5. The method for producing a ceramic-metal joined body according to 4. 18. The laminated brazing material has a thickness of 100 μm.
18. The method for producing a ceramic-metal joined body according to claim 17, wherein m is not more than m.