JPH10335536A - Ceramic-metal junctioned structure with excellent thermal shock resisting property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic-metal junctioned substrate, having excellent thermal shock resisting property, which can be sufficiently used as a highly excellent reliable part such as a power device mounting insulative circuit substrate. SOLUTION: First, tough-pitch copper plate 2 of 0.25 mm in thickness which will be used for a circuit and a tough pitch copper plate 2 of 0.2 mm in thickness which will be used for a heat sink are prepared as metal members, and a commercially available alumina substrate of 22 mm square used for an HIC is prepared. Then, the copper plate 2 is catalytically arranged on both main surfaces of the prepared alumina substrate 1, and a junction body is obtained by heating and cooling the above-mentioned material in an innert gas atmosphere. Then, the circuit side copper plate 2 in the obtained junction body is formed into the prescribed pattern shape having the edge part width of 0.3 mm, the interval of 0.25 mm and the length of 0.5 mm, and the heat sink side is formed into totally attached form by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-metal bonded substrate having excellent thermal shock resistance, and more particularly to a ceramic-metal bonded substrate which is sufficiently used as a component requiring high reliability such as an insulated circuit board for mounting a power device. The present invention relates to a ceramic-metal bonded substrate that can be used.

[0002]

2. Description of the Related Art Conventionally, as a method of joining a ceramic member and a metal member, a direct joining method in which the two members are brought into direct contact with each other, or an intermediate layer is interposed between the ceramic member and the metal member. The intermediate material method has been put to practical use. As a direct bonding method, for example, a method is known in which alumina and copper are brought into direct contact in an inert gas atmosphere and heated and cooled to obtain a bonded body (disclosed in US Pat. No. 4811893). Also, it is known that a direct bonded body can be obtained by a combination of niobium and alumina, or a combination of silicon nitride and nickel.

On the other hand, as an intermediate material method, there are an active metal method and a metallization method. The active metal method uses a group IV element such as Ti or Zr or an alloy containing a group IV element as an intermediate material,
In this method, the intermediate member is sandwiched between a ceramic member and a metal member and joined. For example, an Ag-Cu-Ti alloy has been used as an intermediate material for bonding silicon nitride and stainless steel, and a Cu-Ti alloy has been used as an intermediate material for bonding alumina and copper. The metallization method is a method of forming a metal film on the surface of a ceramic member and joining the metal member via a brazing material. As a metallization method, for example, a method is known in which a Mo metallized layer is formed on alumina, the surface thereof is plated with Ni, and then a Cu plate is joined via a brazing material.

[0004] When a ceramic-metal bonding substrate for an electric circuit is subjected to a temperature change, that is, a thermal shock when soldering a chip or a terminal or when using a bonding substrate, the thermal expansion coefficient between the ceramic member and the metal member is increased. The thermal stress is generated from the difference. If the generated thermal stress exceeds the strength of the ceramic member, a crack is generated or broken in the ceramic member, and therefore, it has been a major problem how to reduce the thermal stress.

Therefore, in the conventional technology, thermal shock is reduced by slowly cooling from a joining temperature, or thermal stress is relaxed by inserting an intermediate material between a ceramic member and a metal member. . As the intermediate material to be inserted between the two members to reduce the thermal stress, an intermediate material between the thermal expansion coefficient of the ceramic member and the thermal expansion coefficient of the metal member, or a ductile metal that undergoes plastic deformation is used. Have been.

Methods of interposing an intermediate material for relaxing thermal stress between a ceramic member and a metal member include, for example, joining a ceramic turbine rotor of a turbocharger for an automobile to a metal shaft, and an exhaust valve for a marine diesel engine. It has been used for joining ceramic face and metal valve. Further, an alumina-copper bonded circuit board and the like in which a Mo plate is interposed as an intermediate material and bonded are also known.

On the other hand, by changing the shape of the joined body,
Methods for alleviating the above thermal stress have also been developed. For example,
The stress applied to ceramics is reduced by reducing the thickness of the circuit-side metal plate in the ceramic-metal bonded circuit board used as an electronic material, or by thinning only the end of the circuit-side metal plate to provide a step. Was.

However, when an intermediate material for relieving thermal stress is inserted between the ceramic member and the metal member as described above, the inserted intermediate material deteriorates heat dissipation and increases the thickness and weight of the joined body. There were problems such as getting lost. Also, when the shape of the joined body is changed as described above,
Since the metal plate needs a certain thickness to ensure heat dissipation, it is not possible to secure sufficient heat dissipation, or it is not possible to mount devices on thinned parts, so the fundamental pattern size Had to be changed. Furthermore, according to the above-mentioned conventional thermal stress relaxation method, it is necessary to produce various intermediate materials and metal plates having a special shape, so that there is a problem that a significant increase in cost cannot be avoided.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and does not cause deterioration of heat radiation or increase in weight, and thermal stress without changing the pattern size or the substrate area. It is an object of the present invention to provide a ceramics-copper joint substrate excellent in thermal shock resistance capable of alleviating cracks.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, in a joined body of a ceramic substrate and a metal plate, the metal member was viewed from the direction in which the main surface of the ceramic substrate spread. A metal plate is formed so that an edge becomes uneven, or a metal member of the same shape is joined on both main surfaces of a ceramic member at a position which is plane-symmetric with respect to a plane which divides the thickness of the ceramic substrate into two equal parts. As a result, it has been found that the above-mentioned problems are solved, and the present invention has been achieved.

That is, the present invention comprises a ceramic substrate and a metal plate joined on at least one main surface thereof, and the metal plate has an uneven shape in a direction parallel to the main surface of the ceramic substrate. A ceramic-metal bonded substrate excellent in thermal shock resistance, characterized by being formed as described above, more preferably, a ceramic substrate and a metal plate bonded on at least one main surface thereof; Is 0.5mm long, 0.3mm wide, 0.25 to 1.0 in the direction parallel to the main surface of the ceramic substrate.
Ceramics with excellent thermal shock resistance characterized by being formed to have irregularities with an interval selected from mm
A ceramic-metal bonding substrate, comprising: a metal bonding substrate; and a metal plate of the same shape bonded on both main surfaces of the ceramic substrate at positions that are plane-symmetric with respect to a plane that divides the thickness of the ceramic substrate into two equal parts. Is provided.

[0012]

When a thermal shock is repeatedly applied to a ceramic-metal bonded substrate, a thermal stress is generated due to a difference in thermal expansion coefficient between the ceramic member and the metal member. At this time, if the ceramic member does not have strength enough to withstand the generated thermal stress, cracks occur from the vicinity of the edge of the metal member on the surface of the ceramic member. In addition, it has been confirmed that when a thermal shock is further applied to the bonded substrate, cracks progress to the inside of the ceramic member and finally break.

FIGS. 4 and 5 show the progress of the crack.
This will be described below with reference to FIG. The conventional alumina shown in FIG.
It has been confirmed that when a thermal shock is repeatedly applied to the copper-bonded substrate, the cracks 3 occur in the following portions of the alumina substrate 1 as the number of repetitions increases. First, as shown in FIG. 5 (a), it occurs near the convex corner portion of the copper plate pattern, then as shown in FIG. 5 (b), it occurs in a linear portion of the copper plate pattern, and finally, as shown in FIG. This occurs in the concave corner portion of the copper plate pattern. In other words, in a ceramic-metal bonded substrate in which a metal plate having a certain pattern shape is bonded to a ceramic substrate, the magnitude of the stress applied to the ceramic substrate varies depending on the location, and the convex corner is the largest, followed by the linear portion and the concave corner. The order of the divisions is
It can be seen from the order of cracks.

[0014] The ceramic-metal bonding substrate of the present invention comprises:
First, a ceramic substrate and a metal plate bonded to at least one main surface thereof are formed, and an edge portion of the metal plate is formed so as to be uneven in a planar spreading direction of the main surface of the substrate. The thermal shock resistance is improved. The reason why the thermal shock resistance is improved by forming the edge portion of the metal plate in an uneven shape as described above is not clear, but can be considered as follows. When the edge of the metal plate is formed in an uneven shape, cracks are generated from a straight line portion in the vicinity of the edge of the metal plate on the surface of the ceramic substrate. In addition, as compared with a bonded substrate in which an edge of a metal plate is not formed in an uneven shape, a crack generation time when a thermal shock is repeatedly applied is late in a bonded substrate having an uneven shape. From these facts, it is considered that by forming the edge portion of the metal plate in an uneven shape, the direction in which the stress is applied changes, the stress distribution changes, and the magnitude of the thermal stress decreases.

Secondly, the present invention provides a method of joining a metal plate having the same shape on both main surfaces of a ceramic substrate at a position which is plane-symmetric with respect to a plane which divides the thickness of the ceramic substrate into two equal parts. We are improving. The reason why the thermal shock resistance is improved by joining the metal plates in this way can be considered as follows. When the shape of the metal plate bonded on both main surfaces of the ceramic substrate is different, when the thermal shock is applied, the ceramic substrate has a warp in which the side where the metal plate having a large area is bonded becomes concave, and the warp reduces the area. Tensile stress is generated on the surface of the ceramic substrate to which the metal plate is bonded.

This means that a bonding substrate having a solid surface on the heat sink side, such as a ceramic-metal bonding insulated circuit substrate for mounting a power device, has a surface of the ceramic substrate on the circuit side formed in a pattern more than the heat sink side. It can also be seen from the fact that cracks occur more quickly from. Therefore, by making the shape of the metal plate on the heat sink side the same as that of the circuit side, and joining the ceramic substrate at a position that is plane-symmetric with respect to a plane that divides the thickness of the ceramic substrate into two, the warpage of the joined substrate is cancelled, and cracks are generated. Is delayed.

That is, since the ceramic-metal bonded substrate of the present invention has excellent thermal shock resistance by forming the metal plate as described above, it is not necessary to interpose an intermediate material or the like, and the heat radiation property is improved. Deterioration and weight increase are prevented. Further, in the ceramic-metal bonded substrate of the present invention, the edge of the metal plate is formed in an uneven shape, but the level is not at a level where the pattern size of the circuit needs to be changed. There is no. Further, since the metal plate in the ceramic-metal bonding substrate of the present invention can be manufactured by a conventional general method such as a mold method or an etching method, it can be mass-produced at low cost.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

[0019]

Embodiment 1 First, a tough pitch copper plate 2 for a circuit side having a thickness of 0.25 mm and a tough pitch copper plate 2 for a heat sink side having a thickness of 0.2 mm were prepared as metal members, and a commercially available 22 mm square HIC was used as a ceramic member. An alumina substrate was prepared.
Next, the copper plates 2 were placed in contact with both main surfaces of the prepared alumina substrate 1 and heated and cooled in an inert gas atmosphere to obtain a joined body. Next, the circuit-side copper plate 2 in the obtained joined body was cut with an edge width of 0.3 mm and a length of 0.5 m.
m, only the spacing is 0.25mm, 0.5mm and 1.0mm, respectively, etched into a predetermined pattern shape with unevenness slightly different in dimensions, and the heat sink side is etched in a solid shape,
Three types of alumina-copper bonded substrates were produced (FIG. 1).

The three kinds of alumina-copper bonded substrates thus produced were subjected to a thermal shock resistance test. The thermal shock test uses a belt furnace and has the same conditions as those for actually soldering the chips.
The furnace was passed under the condition of a temperature rising / falling rate of 20 ° C./min, and the presence or absence of cracks was examined. The results are shown in Table 1. The presence or absence of cracks was determined by passing the alumina-copper bonded substrate through a furnace a predetermined number of times, dissolving the copper plate with a chemical, immersing it in red ink, washing with water, and then drying it. Was evaluated. Each sample was 3 pieces or more. If no cracks occurred in all the pieces, no cracks occurred. If even one piece cracked, cracks occurred.

[0021]

[Table 1]

[0022]

Example 2 A joined body was obtained in the same manner as in Example 1 except that a tough pitch copper plate 2 having a thickness of 0.25 mm was disposed on the circuit side and the heat sink side of the alumina substrate 1 as a metal member. Next, the circuit side copper plate 2 and the heat sink side copper plate 2
Was etched into a pattern shape having the same shape and being plane-symmetric with respect to a plane that divides the thickness of the alumina substrate 1 into two equal parts, thereby producing an alumina-copper bonded substrate of the present invention (FIG. 2).

With respect to the alumina-copper bonded substrate produced as described above, a thermal shock resistance test and evaluation were performed in the same manner as in Example 1, and the results are shown in Table 1.

[0024]

Comparative Example A conventional alumina-copper bonded substrate was manufactured in the same manner as in Example 1 except that the circuit side copper plate 2 was etched into a pattern shape having no irregularities on the edges and the heat sink side was etched into a solid shape (FIG. 3).

With respect to the alumina-copper bonded substrate produced as described above, a thermal shock resistance test and evaluation were performed in the same manner as in Example 1, and the results are shown in Table 1.

As can be seen from Table 1, the conventional alumina-copper bonded substrate (No. 4) in the comparative example suffered from cracking in the first pass of the furnace, whereas Example 1 did not.
Of the alumina-copper bonded substrate of the present invention in Nos. 2 and 3 having irregularities formed on the edge of the copper plate (Nos. 1, 2, and 3)
Can withstand at least three passes, and can withstand one pass even if the copper plate has no irregularities at the edge (No. 5), and has a thermal shock resistance. It was excellent.

[0027]

According to the development of the ceramic-metal bonded substrate of the present invention, compared with the conventional ceramic-metal bonded substrate, the heat radiation property is not deteriorated, the weight is increased, the pattern size is not changed, and the substrate area is not increased. The thermal shock resistance can be improved. Therefore, the ceramic-metal bonded substrate of the present invention can be manufactured at low cost, and has extremely high commercial value.

[Brief description of the drawings]

FIG. 1 is a view showing an example of an alumina-copper bonding substrate according to the present invention, wherein (a) is a plan view on a circuit side, (b) is a plan view on a heat sink side, and (c) is a sectional side view. .

2A and 2B are diagrams showing another example of the alumina-copper bonding substrate of the present invention, wherein FIG. 2A is a plan view on the circuit side, FIG. 2B is a plan view on the heat sink side, and FIG. It is.

3A and 3B are diagrams showing a conventional alumina-copper bonding substrate, wherein FIG. 3A is a plan view on a circuit side, FIG. 3B is a plan view on a heat sink side, and FIG.

FIG. 4 shows a conventional ceramic as exemplified in FIG.
FIG. 9 is a plan view showing the occurrence of cracks on the pattern-side substrate surface when repeatedly applying a thermal shock to the copper-bonded substrate, wherein (a), (b) and (c) show different numbers of thermal shock repetitions; (B), (b)
(C) is greater than that of (c).

[Explanation of symbols]

 1 Alumina substrate 2 Copper plate 3 Crack

Claims (2)

[Claims] 1. A ceramic substrate comprising: a ceramic substrate and a metal plate bonded on at least one main surface thereof, wherein the metal plate has all edges in a direction parallel to the ceramic substrate main surface.
A ceramic-metal bonding substrate excellent in thermal shock resistance, characterized in that it is formed to have irregularities with a length of 0.5 mm, a width of 0.3 mm, and an interval selected from 0.25 to 1.0 mm. 2. Excellent thermal shock resistance characterized in that metal plates of the same shape are joined on both main surfaces of a ceramic substrate at positions that are plane-symmetric with respect to a plane that divides the thickness of the ceramic substrate into two equal parts. Ceramic-metal bonded substrate.