JP2015104744A - Joining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joining method capable of reducing adverse influence on joining strength and conductivity of electricity and heat, even if a height of a projection formed on a joint surface for easily removing an oxide film is varied, when removing the oxide film and joining an insert material and a joining object material by eutectic reaction between the insert material and the joining object material, by interposing the insert material between the joint surfaces formed with the oxide film.SOLUTION: A projection 1c constituting an uneven structure of the joint surface is formed in an inclined state without erecting on the joint surface. For example, when a shape of the projection 1c is a pyramidal shape, an intersection C with a bottom surface of a perpendicular lowered to a bottom surface from its apex T, is dislocated from the center of gravity G of the bottom surface.

Description

  The present invention relates to a method for joining a metal material having an oxide film on the surface, and more specifically, the metal material can be joined at low pressure and low temperature in the atmosphere, and heat to the base material and the surroundings can be obtained. In particular, the present invention relates to a bonding method capable of minimizing the influence of the applied pressure and obtaining stable bonding strength, and a semiconductor device bonded by such a method.

  For example, a dense and strong oxide film is formed on the surface of an aluminum-based metal material, and the presence of such an oxide film is an obstacle. Therefore, these aluminum-based metal materials are generally metallurgical. Is difficult to join.

In joining with such an aluminum-based metal material, for example, an insert material containing Zn as a metal that causes a eutectic reaction with Al is pressed and heated in a state of being interposed between the joint surfaces, and the aluminum-based material and the insert It is known to cause a eutectic reaction between the materials and join them.
That is, by causing a eutectic reaction between the aluminum-based material and the insert material, the oxide film on the surface of the aluminum-based material is removed, and the resulting eutectic melt is discharged from the joint surface, thereby causing an oxide film. The influence on the bonding quality is eliminated and sound bonding is possible.

  At this time, in order to promote direct contact between the aluminum-based material and the insert material, to form the starting point of the eutectic reaction early, and to make the joining process smoother, in order to destroy the oxide film As a stress concentration means, it has been proposed to form a concavo-convex structure (protrusion) on the joint surface (see cited document 1).

JP 2013-78793 A

  However, in the method described in Patent Document 1, since the concavo-convex structure is fine, it is difficult to process a high-precision concavo-convex structure, and when the height of the protrusions varies, a sufficient contact area is obtained. May not be obtained, and in such a case, there is a problem that the bonding strength varies. In addition, the electrical conductivity and thermal conductivity of the joint surface may be impaired.

  As described above, the present invention provides a method for removing an oxide film on a bonding surface by providing a concavity and convexity on the bonding surface and utilizing a eutectic reaction generated between the insert material and the material to be bonded interposed between the bonding surfaces. It was made in view of the problem. The object of the present invention is to provide a bonding method capable of reducing the influence on the bonding strength and the electrical / thermal conductivity due to the unevenness of the irregularities. Another object of the present invention is to provide a semiconductor device as a joining component to which such a joining method is applied.

  As a result of intensive studies to achieve the above object, the present inventors have found that the projections constituting the concavo-convex structure of the joint surface do not stand upright on the joint surface, that is, asymmetry, that is, the central axis of the projection is The present invention has been completed by finding that the above-mentioned problems can be solved by forming the film in an inclined state.

In other words, the present invention is based on the above knowledge, and in the joining method of the present invention, at least one of the objects is covered with an insert material between two metal members having an oxide film formed on the surface. The bonding material is heated while being relatively pressurized, causing a eutectic reaction between the metal forming the oxide film and the insert material, and discharging the resulting eutectic reaction melt together with the oxide film from the bonding surface. When joining the materials to be joined, a plurality of protrusions are provided on at least one of the joining surfaces of the metal member to break the oxide film, and a center line of at least 60% of the protrusions is inclined with respect to the joining surface. It is characterized by being formed.
The semiconductor device of the present invention is bonded by the above bonding method of the present invention.

  According to the present invention, since 60% or more of the protrusions of the concavo-convex structure formed on the bonding surface are inclined with respect to the bonding surface, the protrusions easily fall down and easily deform due to the pressure applied during bonding. The contact area on the joining surface is increased, and variations in the processing accuracy of the protrusions are absorbed, so that the joining quality can be stabilized.

(A)-(e) is process drawing which shows roughly the exclusion process of the oxide film in the joining method of this invention. These are explanatory drawings which show the example of the formation site | part of the uneven structure in the joining method of this invention. (A)-(d) is explanatory drawing which shows the 1st example of a shape of the processus | protrusion in the joining method of this invention. (A)-(d) is explanatory drawing which shows the 2nd example of a shape of the protrusion in the joining method of this invention. (A)-(d) is explanatory drawing which shows the 3rd example of a processus | protrusion in the joining method of this invention. It is the schematic which shows the structure of a semiconductor device as an example of the components joined by the joining method of this invention. It is a perspective view which shows the point of the butt | joining joining of the round bars in the Example of this invention. It is a perspective view which shows the junction point of the semiconductor device in the Example of this invention.

  Hereinafter, the bonding method of the present invention will be described in more detail and specifically. In the present specification, “%” means mass percentage unless otherwise specified.

In the joining method of the present invention, as described above, an insert material is interposed between the materials to be joined, and the eutectic reaction between the insert material and the metal that forms an oxide film on the joining surface of the joining material. And the generated eutectic reaction melt is discharged from the bonding surface together with the oxide film, so that bonding on the new surface becomes possible at a relatively low temperature (eutectic temperature).
At this time, a large number of protrusions are provided on at least one of the joint surfaces, and at least 60% of the protrusions are inclined with respect to the joint surface.

Therefore, by destroying the oxide film on the joint surface with a low load by the protrusion and bringing it directly into contact with the insert material, it can be the starting point of the eutectic reaction, and can be joined at low pressure and low temperature. It is possible to minimize the influence on the material to be joined and peripheral members.
In addition, since the protrusions are inclined in advance with respect to the bonding surface without standing upright on the bonding surfaces, the protrusions are easily deformed and fall down by pressing from the mating bonding surface during bonding, and the contact area between the bonding surfaces increases. As a result, variations in the processing accuracy of the protrusions are absorbed, the bonding quality is stabilized, and the bonding strength, electrical conductivity, and thermal conductivity can be improved.

In the bonding method of the present invention, all of the plurality of protrusions constituting the concavo-convex structure formed on the bonding surface need not necessarily be inclined, but at least 60% of the total number of protrusions must be inclined.
That is, when the proportion of upright non-inclined protrusions exceeds 40%, the deformability of the entire concavo-convex structure composed of such protrusions is insufficient, and the above effects cannot be obtained.

In the joining method of the present invention, first, irregularities made of a large number of protrusions are formed on at least one joining surface of the materials to be joined. In the present invention, as described later, it is necessary to form the protrusions in a state inclined with respect to the joint surface.
Next, an insert material containing an element that causes a eutectic reaction with the metal constituting the material to be joined provided with the oxide film is interposed between the joint surfaces provided with the concavo-convex structure including such protrusions.

In joining, a relative load is applied to both materials to be joined, and local stress is increased by the protrusions formed on the joining surfaces, and the oxide film on the joining surfaces is locally broken.
When the oxide film on the joint surface is destroyed locally and mechanically, the new surface is exposed and reaches the temperature at which the eutectic reaction occurs, the eutectic reaction occurs, and the elements in the material to be joined and the insert material are joined at the joint interface. A melt is formed by the eutectic reaction with the contained elements.

By further pressurization of the material to be joined, the oxide film on the joining surface is discharged from the joining interface together with the eutectic reaction melt generated, and the joining surface of the material to be joined is directly joined.
At this time, a concavo-convex structure consisting of a large number of protrusions is formed on the joint surface, and the tip of the protrusions selectively contacts the mating surface and locally increases the stress. Thus, a eutectic reaction can be caused, and a strong bonding with a new surface can be performed under a low load.

  FIG. 1A to FIG. 1E are schematic views for explaining an oxide film discharge process according to the bonding method of the present invention, taking as an example the bonding between aluminum-based metal materials.

First, as shown in FIG. 1A, a material containing Zn (zinc) as a material that causes a eutectic reaction with Al between the materials to be bonded 1 and 1 made of an aluminum alloy material as a material to be bonded, For example, the insert material 2 made of zinc foil is sandwiched.
At this time, a concavo-convex structure composed of a large number of protrusions 1c is formed on the surface of the materials 1 and 1 to be bonded, here, the bonding surface of the material 1 to be bonded in the upper side in the figure. Oxide films 1a mainly composed of Al ₂ O ₃ are formed on the surface.

Next, as shown in FIG.1 (b), both the to-be-joined materials 1 and 1 are pressurized, these are closely_contact | adhered via the insert material 2, and a heating is started, adding a load. Then, in spite of the low load, the stress at the portion where the tip of the projection 1c of the concavo-convex structure contacts locally rapidly increases, and the oxide film 1a of the material 1 to be joined is mechanically broken, and FIG. As shown in FIG.
When the new surface of the material to be bonded 1 and the insert material 2 are in direct contact with each other through the crack C, when the temperature of the bonding surface reaches a temperature at which a eutectic reaction occurs, Al in the material to be bonded 1 and the insert A eutectic reaction occurs between Zn of the material 2 and a eutectic melt phase is generated. Then, as shown in FIG. 1 (d), the eutectic melting range is expanded, and the broken pieces of the oxide film 1a are dispersed in the eutectic melting phase.

  By subsequent pressurization, as shown in FIG. 1 (e), the eutectic reaction melt is discharged from the bonding interface, and the fragments of the oxide film 1a dispersed in this liquid phase are also discharged together with the eutectic melt. At the same time, they are pushed out from the bonding interface, and the new surfaces of the materials to be bonded 1 and 1 are bonded to each other.

  About the formation position of the said protrusion 1c, what is necessary is just to form in one or more places of a joining surface, and it forms in one of the joining surfaces of the to-be-joined materials 1 and 1 as mentioned above, and as shown in FIG. Both can be provided. By forming it on both surfaces, it is possible to increase the breakdown starting point of the oxide film.

  Further, the protrusion 1c constituting the concavo-convex structure needs to be formed in an inclined state with respect to the joint surface. The shape is not particularly limited as long as it is tilted without standing upright on the joint surface. For example, the shape shown in FIGS. 3 to 5 can be adopted.

That is, as shown in FIG. 3, the tip portion can be formed into a dot shape, that is, a conical protrusion. Here, an example of a quadrangular pyramid is shown as a representative example of the conical protrusion.
As shown in FIG. 3A, the concavo-convex structure according to this embodiment is composed of innumerable quadrangular pyramidal projections 1c arranged in the vertical and horizontal directions at a pitch p without a gap on the joint surface.

  As shown in an enlarged view of FIG. 3 (b), each protrusion 1c has an inclined shape instead of a symmetric shape, like an accurate quadrangular pyramid. From the apex T to the bottom surface of the protrusion 1c. The lowered vertical line intersects the bottom surface at a position C deviated from the center of gravity G of the bottom surface.

Regarding the positional relationship between the intersection C between the perpendicular line from the vertex T and the bottom surface and the center of gravity G of the bottom surface, as shown in FIGS. 3C and 3D, the line segment connecting the center of gravity G and the intersection C is the bottom surface. It is preferable that the value of d / L is 0.1 or more, where E1 and E2 are points intersecting each other, L is the distance between E1 and E2, and d is the distance between the center of gravity G and the intersection C.
That is, the protrusion 1c whose d / L value is less than 0.1 is not inclined in shape, and the effect of the present invention due to the inclination may not be sufficiently obtained.

FIG. 4 shows another example of the shape of the protrusion, in which the tip is linear, that is, an example of a roof-type protrusion (sawtooth-shaped cross section) arranged in parallel with a triangular prism.
As shown in FIG. 4A, the concavo-convex structure according to this embodiment is composed of innumerable triangular prism-shaped projections 1c arranged in parallel at a pitch p in the lateral direction without gaps on the joint surface.

As shown in FIG. 4B, each protrusion 1c has a cross section that is not an isosceles triangle, but an asymmetrically inclined shape, and is the midpoint M of the apex line (ridge line) that is the tip. From the above, the perpendicular line dropped to the bottom surface of the projection 1c intersects the bottom surface at the position C deviated from the center of gravity G of the bottom surface, as in the case of the quadrangular pyramid described above.
As shown in FIGS. 4C and 4D, the positional relationship between the intersection C between the perpendicular line from the vertex T and the bottom surface and the center of gravity G of the bottom surface is similar to that of the square pyramid, as shown in FIGS. The points where the line connecting the intersection C intersects the bottom are E1 and E2, respectively, the distance between E1 and E2 is L, and the distance between the center of gravity G and the intersection C is d. It is desirable to be 1 or more.

Furthermore, as shown in FIG. 5, as another embodiment, the tip portion may have a planar shape, that is, a frustum-shaped protrusion.
As shown in FIG. 5 (a), the concavo-convex structure according to this embodiment is composed of innumerable quadrangular pyramid-shaped protrusions 1c arranged on the joint surface in the vertical and horizontal directions at a pitch p with no gap.

  As shown in an enlarged view in FIG. 5B, each protrusion 1c has an inclined shape rather than a symmetrical shape such as an accurate quadrangular frustum. The perpendicular line drawn down to the bottom surface of 1c intersects the bottom surface at the position C deviated from the center of gravity G of the bottom surface, as in the case of the quadrangular pyramid (first form).

The positional relationship between the intersection C between the perpendicular line drawn from the center of gravity Gt of the projection top surface and the bottom surface and the center of gravity G of the bottom surface is not different from the first and second embodiments.
That is, as shown in FIGS. 5C and 5D, the points where the line segment connecting the center of gravity G and the intersection C intersects the bottom surface are E1 and E2, respectively, the distance between E1 and E2 is L, and the center of gravity G- When the distance between the intersection points C is d, it is desirable that the value of d / L is 0.1 or more.

  The shape of the protrusion 1c is not limited in terms of number or shape as long as it has a function of concentrating stress and promoting the destruction of the oxide film. It is also possible to make the tip of the part a curved surface. Needless to say, the smaller the radius of curvature of the curved surface, the more conspicuous the stress concentration becomes, and the more easily the oxide film is broken.

  As for the shape of the protrusions 1c, the aspect ratio is preferably 0.001 or more and the pitch is 1 μm or more, more preferably, the aspect ratio is 0.1 or more and the pitch is 10 μm or more. That is, when the aspect ratio is less than 0.001 and the pitch is less than 1 μm, the stress cannot be sufficiently concentrated, and the oxide film may be difficult to break.

  The protrusion 1c can be formed by cutting, grinding, plastic processing (roller processing), laser processing, electric discharge processing, etching processing, lithography, or the like, and the forming method is not particularly limited. However, the plastic working can be formed at a very low cost.

As described above, the example in which the aluminum metal material is joined using the insert material made of zinc foil has been described. As described above, the materials to be bonded in the bonding method of the present invention include aluminum-based and magnesium-based metal materials that form a strong oxide film, but at least one of the materials to be bonded forms an oxide film on the surface. As long as it is, it can become a joining object of the method of the present invention.
That is, it can be applied to all practical metals, for example, copper and copper alloys, nickel and nickel alloys, steel materials, etc., except for bonding of gold (Au) where an oxide film is not formed. Further, it can be applied not only to the same kind of material but also to the joining between different kinds of materials.

Here, the insert material may be a metal material that causes a eutectic reaction with Al in the case of joining the aluminum-based metal material as described above. In addition to the zinc foil, magnesium (Mg It is also possible to use a foil, a tin (Sn) foil, Zn, Mg, Sn, an alloy containing these as a main component, or an alloy of these metals and Al.
The “main component” means that the metal content is 80% or more. Specifically, it means a metal (pure metal or alloy) containing 80% or more of Zn, Mg, Sn, Zn + Mg, Zn + Sn, Mg + Sn, Zn + Mg + Sn, Zn + Al, Mg + Al, Sn + Al, Zn + Mg + Al, Zn + Sn + Al, Mg + Sn + Al, Zn + Mg + Sn + Al.

  Cu (copper) can also be used as a metal that causes a eutectic reaction with Al. However, since the melting point of Cu is higher than the melting point of Al, Al is previously alloyed as an insert material. Therefore, it is necessary to use a Cu—Al alloy whose components are adjusted so that its melting point is lower than the melting point of the aluminum alloy base material.

  Further, the material to be joined is not limited to the aluminum-based metal material, and as described above, for example, it can be applied to the joining of copper and copper alloys, magnesium and magnesium alloys, nickel and nickel-base alloys, and iron-based materials. Can do.

As an insert material in the joining of copper or a copper-based alloy, for example, Al, Ag (silver), Sn, or an alloy thereof can be used as described above.
In addition to the above, Ti (titanium) can be cited as a metal that causes a eutectic reaction with Cu. However, since the melting point of Ti is higher than the melting point of Cu, similarly to the above, Ti In addition, it is necessary to use an alloy having a lower melting point than Cu obtained by previously alloying Cu as an insert material.

Moreover, as an insert material used for joining magnesium or a magnesium-based alloy, for example, Al, Zn, or an alloy thereof can be used in the same manner as described above.
Si (silicon) is an element that causes a eutectic reaction with Mg. However, since the melting point of Si is higher than that of Mg, similarly to the above, it has a lower melting point than Mg obtained by alloying Mg in advance. It is necessary to use an alloy as the insert material. Also, since Al is close to the melting point of Mg, it is desirable to use an insert material in which Mg is similarly alloyed.

Furthermore, as an insert material used for joining nickel or a nickel base alloy, for example, Cu or an alloy thereof can be used in the same manner.
In addition to Cu, Ti, Nb (niobium), and Cr (chromium) can be cited as metals that cause a eutectic reaction with Ni. The melting point of these metals is higher than that of Ni. Therefore, it is necessary to use an alloy having a lower melting point than Ni by alloying Ni in advance as an insert material.

  For joining iron-based materials, a material having a lower melting point than that of the base material by alloying Fe with C, N, or Cr can be used as an insert material.

As a method of interposing between the shape of the insert material and the two materials to be joined, since there is a high degree of freedom in selecting the composition and shape (thickness), it is sandwiched between both materials in the form of foil. Is desirable.
Moreover, it is also possible to coat | cover an insert material beforehand to the joint surface of one or both of both materials by plating or the powder deposition method.

The bonding method of the present invention can be performed in an inert gas atmosphere, but can be performed in the air without any trouble.
Of course, it can be performed in a vacuum, but not only vacuum equipment is required, but also the vacuum gauge and gate valve may be damaged by melting of the insert material. It is also advantageous.

In the bonding method of the present invention, the means for heating and maintaining the bonded portion within the above temperature range is not particularly limited, and for example, resistance heating, high-frequency heating, infrared heating, or a combination thereof Can be adopted.
In addition, if the bonding temperature is too high, the base material dissolves and an excessive liquid phase is generated, and if the liquid phase is excessive, it remains at the bonding interface and the strength tends not to be obtained. Specifically, a temperature range from the eutectic point to eutectic point + 100 ° C. is preferable.

  As for the rate of temperature rise to the bonding temperature, if it is slow, the interface is oxidized and the melt discharge property is lowered, which may cause the strength to be lowered. This tendency occurs particularly in the case of bonding in the atmosphere. Specifically, it is more preferably 3 ° C./second or more, 10 ° C./second or more, and further preferably 25 ° C./second or more.

  In addition, as a pressing force at the time of bonding in the bonding method of the present invention, bonding can be performed with a low pressing force of 30 MPa or less, an applied load can be reduced, damage to the materials to be bonded can be prevented, and a pressurizing system can be used. It can be simplified, energy consumption can be suppressed, and cost can be reduced.

As described above, the bonding method of the present invention can be applied to bonding various metals having an oxide film, and a typical example thereof is a semiconductor device.
FIG. 6 is a schematic cross-sectional view showing the structure of a semiconductor device formed by bonding a semiconductor chip onto an insulating substrate by the above bonding method.

That is, the semiconductor device shown in the figure includes an insulating substrate 12 fixed on a heat sink 11 and a structure in which a silicon chip 14 is bonded to a wiring metal 13 disposed on the surface of the substrate 12.
The wiring metal 13 is made of an aluminum alloy, and the bonding surface of the silicon chip 14 is preliminarily coated with aluminum, and these aluminum-based metals are bonded to each other by the method of the present invention.

In joining the wiring metal 13 and the silicon chip 14, an uneven structure including innumerable protrusions is formed in advance on the joining surface of the wiring metal 13 made of aluminum alloy by plastic working or cutting.
Then, a quenching foil strip of 25 μm thick Al—Sn—Zn alloy is disposed as an insert material between the wiring metal 13 and the silicon chip 14 so that a pressing force of 15 MPa or less is always applied using a jig. Fixed.

Then, for example, the wiring metal 13 and the silicon chip 14 can be joined by storing in this state in a brazing furnace and holding at 400 ° C. for 1 minute.
According to this method, in addition to being free of Pb (lead), since the bonding is completed at a low temperature and in a short time, the thermal influence on the semiconductor chip can be minimized, and the component Distortion and performance degradation can be prevented. In addition, a plurality of chips can be bonded simultaneously. In addition to the silicon chip described above, various semiconductor chips such as SiC and GaN can be used as the semiconductor chip.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited at all by such an Example.

[1] Example 1
(Invention Example 1)
As shown in FIG. 7, a 15 mm long, 5 mm diameter round bar 3 made of industrial pure aluminum (99.99% Al) defined as A1070, and a 25 mm long, 10 mm diameter round A rod 4 was prepared.
At this time, a pyramidal projection 1c (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = as shown in FIG. 3 is formed on the joint surface of the round bar 4 having a diameter of 10 mm. An uneven structure consisting of 0.35) was formed by cutting using a diamond tool.

A 0.1 mm thick foil strip made of a Zn-3.5% Al-2.5% Mg alloy made by a rapid cooling single roll method is inserted between the joint surfaces of the round bar 3 and the round bar 4 as an insert material. Sandwiched as 2.
And the said round bars 3 and 4 were joined by heating to 400 degreeC with the high frequency heating coil S arrange | positioned around the junction part in air | atmosphere, and hold | maintaining in the state pressurized by 5 MPa for 1 minute.

(Invention Example 2)
A protrusion 1c (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = having a sawtooth cross section in which triangular prisms as shown in FIG. Except having formed the uneven | corrugated structure which consists of 0.35), by repeating the same operation as the said invention example 1, the round bars 3 and 4 were joined and it was set as invention example 2.

(Invention Example 3)
On the joint surface of the round bar 4, a truncated pyramid-shaped projection 1c as shown in FIG. 5 (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, w = 0.02 mm, d / L = Except having formed the uneven | corrugated structure which consists of 0.35), the round bar 3 and 4 was joined by repeating the same operation as the said invention example 1, and it was set as invention example 3. FIG.

(Invention Example 4)
By repeating the same operation as in the invention example 1 except that the round bar 3 and the round bar 4 are made of a magnesium alloy (9% Al) defined as AZ91 by ASTM (American Society for Testing and Materials). The round bars 3 and 4 were joined to obtain Invention Example 4.

(Invention example 5)
Except that the round bar 3 and the round bar 4 are made of oxygen-free copper, the same operation as in the above-described Invention Example 1 is repeated, whereby the round bars 3 and 4 are joined to obtain Invention Example 5.

(Comparative Example 1)
The round bars 3 and 4 were joined by repeating the same operation as the said invention example 1 without using an insert material, and it was set as the comparative example 1.

(Comparative Example 2)
The round bars 3 and 4 were joined by repeating the same operation as the said invention example 2 without using an insert material, and it was set as the comparative example 2.

(Comparative Example 3)
By repeating the same operation as in the above-mentioned Invention Example 3 without using an insert material, the round bars 3 and 4 were joined to obtain Comparative Example 3.

(Comparative Example 4)
A concavo-convex structure in which pyramid-shaped protrusions (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having a symmetric shape are formed upright on the joint surface of the round bar 4 is formed. Except for this, the same operation as in Comparative Example 1 (without insert material) was repeated, whereby the round bars 3 and 4 were joined to obtain Comparative Example 4.

(Comparative Example 5)
Unevenness formed by upstanding a roof-shaped protrusion 1c (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having an isosceles triangular cross section on the joint surface of the round bar 4 Except having formed the structure, the same operation as the said comparative example 2 (no insert material) was repeated, the round bars 3 and 4 were joined and it was set as the comparative example 5.

(Comparative Example 6)
A symmetrical truncated pyramid-shaped projection (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, w = 0.02 mm, d / L = 0) is made upright on the joint surface of the round bar 4. The round bars 3 and 4 were joined by repeating the same operation as in the comparative example 3 (no insert material) except that the concavo-convex structure was formed.

(Comparative Example 7)
A concavo-convex structure in which pyramid-shaped protrusions (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having a symmetric shape are formed upright on the joint surface of the round bar 4 is formed. Except for this, by repeating the same operation as in the above-described Invention Example 1 (with insert material), the round bars 3 and 4 were joined to obtain Comparative Example 7.

(Comparative Example 8)
Unevenness formed by upstanding a roof-shaped protrusion 1c (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having an isosceles triangular cross section on the joint surface of the round bar 4 Except that the structure was formed, the same operations as those in Invention Example 2 were repeated, whereby the round bars 3 and 4 were joined to obtain Comparative Example 8.

(Comparative Example 9)
A symmetrical truncated pyramid-shaped projection (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, w = 0.02 mm, d / L = 0) is made upright on the joint surface of the round bar 4. The round bars 3 and 4 were joined by repeating the same operation as that of the above-described Invention Example 3 except that the uneven structure was formed.

(Comparative Example 10)
A concavo-convex structure in which pyramid-shaped protrusions (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having a symmetric shape are formed upright on the joint surface of the round bar 4 is formed. Except for this, by repeating the same operation as in the above-described Invention Example 4 (material to be joined made of magnesium alloy), the round bars 3 and 4 were joined to obtain Comparative Example 10.

(Comparative Example 11)
A concavo-convex structure in which pyramid-shaped protrusions (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having a symmetric shape are formed upright on the joint surface of the round bar 4 is formed. Except for this, by repeating the same operation as in Invention Example 5 (material to be joined made of oxygen-free copper), the round bars 3 and 4 were joined to obtain Comparative Example 11.

(Evaluation method)
The joint strength of each joined body of the round bar 3 and the round bar 4 obtained as described above was evaluated by a tensile test (tensile speed: 1 mm / min) using a universal tester. The test was repeated five times, and the average value was used as the bonding strength, and the standard deviation was obtained as an index of variation.
Further, wires were welded to the ends of the round bars 3 and 4, and the electrical resistance at the joint interface was obtained by the four-point terminal method, and the thermal conductivity at the joint interface was obtained by the laser flash method. These results are summarized in Table 1.

[2] Example 2
(Invention Example 6)
As shown in FIG. 8, on both sides of a ceramic plate 5 made of 15 mm × 15 mm × 0.635 mm AlN, plate materials 6 and 6 made of pure aluminum 12 mm × 12 mm × 0.5 mm are attached on a ceramic substrate. The semiconductor chip 7 made of Si was joined.
At the time of bonding, pure aluminum is sputtered on the bonding surface of the semiconductor chip 7, while the protrusion 1c (a = 0.1 mm) having a sawtooth cross section as shown in FIG. , H = 0.1 mm, p = 0.1 mm, d / L = 0.35) was formed by cutting using a diamond tool.

  Next, a 0.1 mm-thick foil strip made of a Zn-3.5% Al-2.5% Mg alloy produced by a rapid cooling single roll method is inserted between the joining surfaces of the aluminum plate 6 and the semiconductor chip 7. Sandwiched as material 2. Then, in this state, the semiconductor chip 7 was bonded to the aluminum plate 6 on the ceramic substrate by holding it at 400 ° C. for 1 minute under an applied pressure of 5 MPa with an infrared heating type diffusion bonding apparatus.

(Comparative Example 12)
Concavities and convexities formed by erecting a roof-shaped protrusion 1c (a = 0.1 mm, h = 0.1 mm, p = 0.1 mm, d / L = 0) having an isosceles triangular section on the joint surface of the aluminum plate 6 Except that the structure was formed, the semiconductor chip 7 was joined to the aluminum plate 6 on the ceramic substrate by repeating the same operation as in the sixth invention example.

(Evaluation method)
The bonding strength of the semiconductor device obtained as described above was evaluated by a die shear test (shear rate: 100 μm / second). At this time, the number of test repetitions was 5, and the average value was used as the bonding strength, and the standard deviation was obtained as an index of variation.
Further, the obtained semiconductor device was incorporated into a simple circuit to determine the electrical resistance of the bonding interface, and the thermal conductivity of the bonding interface was determined by a laser flash method.
These results are shown in Table 2.

1 Bonded material 1a Oxide film 1c Protrusion
2 Insert material

Claims (5)

A metal and an insert in which an oxide film is formed by heating the material to be joined in a state in which an insert material is interposed between two metal members, at least one of which has an oxide film formed on the surface, while relatively pressing. When the eutectic reaction is generated between the materials and the resulting eutectic reaction melt is discharged together with the oxide film from the joining surface to join the materials to be joined,
A plurality of protrusions provided on at least one of the joint surfaces of the metal member to destroy the oxide film, and a center line of at least 60% of the protrusions is inclined with respect to the joint surface; Method.   The tip of the fine protrusion has a dot shape, and the intersection of the perpendicular line and the bottom surface of the fine protrusion, which occupies 60% or more of the fine protrusion, deviates from the center of gravity of the bottom surface. 2. The joining method according to 1.   The tip of the fine protrusion is linear, and the intersection of the perpendicular line and the bottom surface of the top surface of the fine protrusion, which occupies 60% or more, is shifted from the center of gravity of the bottom surface. The joining method according to claim 1, characterized in that:   The tip of the fine projection has a planar shape, and the intersection of the perpendicular line and the bottom surface of the top surface of the fine projection, which occupies 60% or more, and the bottom surface of the fine projection is shifted from the center of gravity of the bottom surface. The joining method according to claim 1. A semiconductor device bonded by the method according to claim 1.

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