JP4840284B2 - Joining layer-containing member and manufacturing method thereof - Google Patents

Description

  The present invention relates to a joining layer-containing member and a method for producing the same, and although not limited thereto, the present invention relates to a joining layer-containing member obtained by joining and integrating two members having a difference in thermal expansion using solder or brazing material as a joining layer.

  A bonding layer-containing member is known in which two members having a wide area are coated with a bonding material such as solder or brazing material in a region to be a bonding surface to form a bonding layer, and the two are bonded and integrated. As an example, a circuit board joined to a heat dissipation board for mounting various elements including a semiconductor element can be cited. An inverter for an HV vehicle is one example, and is formed by joining and integrating three members, a semiconductor element having a large area, an insulating material, and a heat radiating material, with a joining material such as solder or brazing material. In such a product, the thermal expansion coefficient of each member to be joined is usually different, and when thermal stress is repeatedly applied, a crack (crack) may occur in the joining layer due to thermal history.

  FIG. 4 schematically shows this, in which FIG. 4 (a) shows the state before the test, and FIG. 4 (b) shows the state after the test. Apply a bonding material (for example, solder) to a part 1 (for example, an insulating material or a heat dissipation material) and a part 2 (for example, a semiconductor element) having a large area and having different thermal expansion coefficients in a region substantially corresponding to the area of the part 2. Thus, the bonding layer 3 is formed, and both are bonded and integrated to obtain a product 5. When repeated thermal stress is repeatedly applied to the product 5, due to the thermal history, as shown in FIG. As shown, the occurrence of cracks can be observed. When such a crack occurs, there is a possibility that the bonding strength, electrical conductivity, or thermal conductivity at the time of design cannot be maintained.

  As one solution for improving the reliability against thermal history, Patent Document 1 discloses a ceramic circuit board in which a ceramic substrate and a metal circuit board are bonded via a bonding layer (brazing material). It is described that the corrugated shape is formed along the pattern of the metal circuit board. By making the outer circumference of the bonding layer apparently longer as the corrugated outer shape, the stress concentration at the joint edge between the ceramic substrate and the metal circuit board can be relaxed, and cracks in the ceramic substrate due to thermal stress and thermal cycle It is described that it can be prevented from occurring.

JP-A-2005-93803

  As described above, in the bonding layer-containing member in which the two members are integrated via the bonding layer, a crack may occur in the outer region of the bonding layer due to the thermal history. In such a case, the occurrence of cracks makes it impossible to maintain the electrical conductivity or thermal conductivity at the time of design and accelerates the deterioration of the product.

  Therefore, the present invention provides a bonding layer-containing member in which, in a bonding layer-containing member in which two members are integrated via a bonding layer, the occurrence of cracks in the bonding layer due to thermal history can be avoided. Let it be an issue.

  In the conventional bonding layer-containing member, the present inventor cracks inward from the peripheral edge of the bonding layer due to thermal history, because the thermal stress accompanying the temperature change occurs in the central portion of the bonding layer. It was thought that the smaller the outer peripheral portion, the larger the thermal stress generated at the end portion (peripheral edge portion), the larger the bonding area. Then, the bonding layer is divided into a large number of bonding sections, and the size of each bonding section is gradually reduced from the center toward the outer periphery so that cracks due to thermal stress occur. It was confirmed by experiments that it can be suppressed.

  As described in Patent Document 1, the outer peripheral portion of the bonding layer has a corrugated shape along the pattern of the metal circuit board, and the outer peripheral length of the bonding layer is apparently increased, so that the bonding end between the ceramic substrate and the metal circuit board is obtained. Even if the stress concentration on the surface can be alleviated, it is difficult to completely suppress the occurrence of cracks on the outer periphery as long as the bonding layer has a large area.

  The present invention has been made based on the above knowledge, and the bonding layer-containing member according to the present invention is a bonding layer-containing member in which the second member is bonded to the first member via the bonding layer made of the bonding material. The bonding layer has a shape in which a plurality of bonding sections are arranged with a gap, and the bonding layer is divided into an outer region which is an outer peripheral region thereof and an inner region which is located on the inner side of the outer region. The area per bonding section is the smallest in the outer region and larger in the inner region.

  In the joining layer-containing member according to the present invention, the inner region of the joining layer may be formed as a set of a plurality of joining sections having the same area, but preferably the area per joining section is from the outside to the inside. Preferably, it is formed as a set of a plurality of joint sections that are gradually enlarged toward the end.

  In the joining layer-containing member according to the present invention, since the thermal stress increases and the distortion increases toward the outer peripheral portion as a whole, the area per joining section decreases toward the outer peripheral side. The strain applied per piece is small, and the generated stress is small. Therefore, it can suppress that a crack generate | occur | produces in the outer side area | region of a joining layer, As a result, the product life of the said joining layer containing member can be lengthened.

  In the present invention, as a first method for manufacturing the bonding layer-containing member, the bonding surface of the first member and / or the second member using a mask created according to the arrangement pattern of the plurality of bonding sections. Also disclosed is a method for manufacturing a bonding layer-containing member, comprising: a step of applying a bonding material to the substrate, a step of removing the mask, and a step of bonding the first member and the second member. To do.

  Further, as a second manufacturing method, a material that easily wets the bonding material is disposed at a position where the plurality of bonding sections are to be formed on the bonding surface of the first member and / or the second member, and the gap is not formed. The step of disposing a material that is difficult to wet the bonding material at a place to be formed, the step of applying the bonding material to the entire surface of the region to be the bonding layer, and bonding the first member and the second member The manufacturing method of the joining layer containing member characterized by including this process is also disclosed.

By employing the above manufacturing method, a desired arrangement pattern of a plurality of joining sections can be easily formed on the joining surface. In the second method, when solder is used as the joining material, Ni, Cu, etc. can be cited as examples of materials that are easily wetted, and Al, AlN, Si ₃ N ₄ , SiC, Al can be used as materials that are difficult to wet. ₂ O ₃ etc. can be mentioned as an example. The solder applied on the entire surface moves to a region where the material that is difficult to wet moves to the region where the material that easily wets is arranged.

  In the bonding layer-containing member according to the present invention, the first member and the second member may have the same or a different coefficient of thermal expansion. In the case of two members having different thermal expansion coefficients, a thermal stress having a distribution that increases from the center toward the outer periphery due to the difference in thermal expansion coefficient is applied to the bonding material, but as described above, the area per bonding section By adjusting, the occurrence of cracks can be effectively suppressed.

  In the bonding layer-containing member according to the present invention, the ratio of the gap in the bonding layer to the total area of the bonding layer is preferably small from the viewpoint of bonding strength, electrical conductivity, thermal conductivity, and the like. However, if it is too small, the joining sections are joined together, and the intended purpose may not be achieved. The optimum value is set in consideration of various physical property values required for the bonding layer-containing member to be obtained. In the bonding layer-containing member according to the present invention, the bonding strength, electrical conductivity, thermal conductivity, etc. compared to the conventional product in which the entire surface of the bonding layer is covered with the bonding material by the amount of the gap. The performance is degraded. However, the decrease is slight, and the occurrence of cracks can be suppressed and the performance at the time of design can be maintained over a long period of time. Therefore, the bonding layer-containing member according to the present invention has a high advantage as a whole.

  ADVANTAGE OF THE INVENTION According to this invention, in the joining layer containing member which two members integrated through the joining layer, the joining layer containing member which made it possible to avoid that a crack generate | occur | produces in a joining layer by a heat history is provided.

  Hereinafter, the present invention will be described with reference to embodiments. FIG. 1 shows an example of a bonding layer-containing member according to the present invention.

  In this example, the bonding layer-containing member 10 is a bonding in which a first member 11 having a thermal expansion coefficient a and a second member 12 having a thermal expansion coefficient b are applied to an area approximately equal to the second member 12. The joining layer 13 made of a material (solder or the like) is joined and integrated. In the actual bonding layer-containing member 10, the bonding layer 13 exists between the first member 11 and the second member 12 and is not actually visible, but for convenience of explanation, in the figure, It is drawn so that it can be seen.

  The bonding layer 13 has a shape in which a plurality of bonding sections 14, 15, 16 are arranged with a gap 17. In this example, the first bonding section 14 having the smallest area per area and the second surface It is formed of a large second joint section 15 and a third joint section 16 that is large on the third surface. The group consisting of the first joining sections 14 having the smallest area forms the outer area of the joining area referred to in the present invention, and the group consisting of the second joining sections 15 and the group consisting of the third joining sections 16 form the inner area. In the inner region, the group consisting of the second joining sections 15 is located outside, and the group consisting of the third joining sections 16 is located inside thereof.

  Therefore, in the entire bonding layer 13, the bonding sections 14, 15, 16 arranged with gaps have the smallest bonding area in the outer peripheral region of the bonding layer 13, and hereinafter, the inner side (center portion). It is arranged to become gradually larger toward In the illustrated example, the region composed of the first joint section 14 is arranged over two laps, the region composed of the second joint section 15 is arranged over two laps inside, and the innermost is the largest. The third bonding section 16 which is the bonding area is arranged in a form of 2 columns × 5 rows, but this arrangement form is merely an example, and is the smallest in the outermost region of the bonding region, and is continuous toward the inner side. If the arrangement gradually increases in size, stepwise or stepwise, all of the intended purposes can be achieved.

  Although the method for forming the arrangement pattern of the plurality of joining sections 14, 15, 16 as described above is arbitrary, as one method, although not shown, a first member is formed using a mask created according to the arrangement pattern. 11 and / or a method in which a mask is placed on the bonding surface of the second member 12, a bonding material is applied thereon, the mask is removed, and the first member 11 and the second member 12 are bonded to each other. .

As another method, a material where the joining material such as Ni and Cu is easily wetted is used in a place where the plurality of joining sections 14, 15 and 16 are to be formed, and a place where the gap 17 is to be formed. There is a method in which a bonding material such as AlN or Si ₃ N ₄ that is difficult to wet is patterned in advance, and then the bonding material is applied to the entire surface of the region to be the bonding layer 13. In this method, the bonding layer 13 having an intended arrangement pattern is formed by the solder on the material that is difficult to wet move to the region where the material that easily wets is arranged.

  In the bonding layer-containing member 10 according to the present invention, as described above, the bonding section having a large bonding area per one is disposed with a gap at the center, and the bonding area gradually decreases toward the outer periphery of the bonding area. Are disposed with a gap between them, and the bonding section having the smallest bonding area per one is disposed with a gap at the outermost periphery, so that the bonding layer-containing member 10 as a whole goes to the outer peripheral portion by heating. Even if thermal stress and strain that become larger are applied, the thermal stress and strain applied to each joint section are reduced. Therefore, it can suppress effectively that a crack generate | occur | produces in the outer side area | region of the joining layer 13, and the product life of the joining layer containing member 10 can be lengthened.

  Hereinafter, the usefulness of the present invention will be described with reference to Examples and Comparative Examples.

[Example 1]
As shown in FIG. 2A, a CuMo heat sink (110 mm × 110 mm × 3 mm) as the first member 11 and an aluminum nitride insulating plate with an Al electrode (102 mm × 102 mm × 1. 5 mm) was integrated with the bonding layer 13 made of the solder material Sn ₃ Ag0.5Cu (lead-free). Using a mask (not shown), the solder was printed in the pattern shown, and then reflowed at a peak temperature of 280 ° C. in a nitrogen atmosphere. Area per one joint compartment, the size of most 10mm × 10mm = 100mm ² The size of the outer joint sections 14, 12mm × 12mm = 144mm ² The size of the middle joint section 15, the center of the joint section 16 Was 24 mm × 24 mm = 576 mm ² . Each joining section was arranged with approximately equal gaps. The total bonding material area of the bonding layer 13 is 7408 mm ² .

[Comparative example]
As shown in FIG. 2B, a joining layer-containing member is formed in the same manner as in Example 1 except that the joining layer 13 made of the solder material Sn ₃ Ag0.5Cu (lead-free) is formed in the entire region of 100 mm × 100 mm. made. The total bonding material area of the bonding layer 13 is 10,000 mm ² .

[test]
A vapor-phase cooling / heating cycle test (−40 ° C. to 105 ° C., maximum 2000 cycles) was performed on the example product and the comparative product. In the middle of the test, the specimen was taken out and the generated crack area was measured using an ultrasonic flaw detector. The results are shown in the graph of FIG.

[Evaluation]
As shown in the graph of FIG. 3, the occurrence of cracks in the example is greatly reduced, and the usefulness of the product of the present invention can be evaluated.

The figure which shows an example of the joining layer containing member by this invention. The figure which shows the joining layer containing member (FIG.2 (a)) of an Example, and the joining layer containing member (FIG.2 (b)) of a comparative example. The graph which shows the crack generation area of an Example and a comparative example. It is a schematic diagram when it tests that a crack (crack) enters into a joining layer of a joining layer content member by thermal history, Drawing 4 (a) is a state before a test, and Drawing 4 (b) is a state after a test. .

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Joining layer containing member, 11 ... 1st member, 12 ... 2nd member, 13 ... Joining layer, 14, 15, 16 ... Multiple joining division, 17 ... Gap

Claims (5)

A joining layer-containing member used in a place where the first member and the second member having a difference in thermal expansion coefficient are joined via a joining layer made of a joining material and the thermal history is repetitively imposed. There,
The bonding layer has a shape in which a plurality of bonding sections are arranged with a gap, and the bonding layer is divided into an outer region which is an outer peripheral region thereof and an inner region which is located on the inner side of the outer region. The bonding layer-containing member is characterized in that an area per section is the smallest in the outer region and larger in the inner region.   2. The joining layer-containing member according to claim 1, wherein in the inner region, an area per joining section gradually increases from the outside toward the inside.   The joining layer-containing member according to claim 1 or 2, wherein the joining material is lead-free solder.   It is a manufacturing method of the joining layer content member according to any one of claims 1 to 3, Comprising: The 1st member and / or the 2nd member using the mask created according to the arrangement pattern of the plurality of joined sections. A method for producing a bonding layer-containing member, comprising: a step of applying a bonding material to the bonding surface, a step of removing a mask, and a step of bonding the first member and the second member. .   It is a manufacturing method of the joining layer content member according to any one of claims 1 to 3, and in the joint surface of said 1st member and / or the 2nd member, in said place where a plurality of joined divisions should be formed. Placing a material that is easily wetted by the bonding material, placing a material that is difficult to wet the bonding material in a place where the gap is to be formed, and applying a bonding material to the entire surface of the bonding layer; A step of bonding the first member and the second member.

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