JP2020155497A - Joined body - Google Patents

Abstract

To provide a joined body capable of effectively suppressing the occurrence of cavities into a junction layer.SOLUTION: A joined body 1 includes a plurality of plate-like members 2, 3 disposed to be superposed over each other and a junction layer 4 interposed between the plate-like members 2, 3 and including a sintered body to mutually join the plate-like members 2, 3. At least one plate-like member 2 has an internal gas passage 5 which passes a joint surface Sb facing a junction layer 4 side of the plate-like member 2 and opens to the outer surface of the plate-like member 2.SELECTED DRAWING: Figure 1

Description

This specification discloses a technique relating to a conjugate.

In recent years, metal powder pastes in which metal powders made of conductive metals such as silver and copper are dispersed in solvents, binders, etc. have been used to bond various semiconductor elements to two plate-shaped members such as substrates. May be used.

In such a metal powder paste, the metal powder contained therein is sintered and diffused by heating to form a bonding layer under the interposition between the two plate-shaped members to be bonded. Two plate-shaped members are joined to each other by this joining layer to obtain a joined body.
In addition, as a technique related to this, there are those described in Patent Documents 1 to 4.

Japanese Unexamined Patent Publication No. 2013-232527 Japanese Unexamined Patent Publication No. 2014-167145 JP-A-2018-152176 Japanese Unexamined Patent Publication No. 2013-206765

By the way, when the metal powder paste is sandwiched between the plate-shaped members and heated, gas is generated due to volatilization of the solvent in the metal powder paste, decomposition of the binder, and the like during heating. This gas causes the generation of large voids or cavities in the bonding layer of the bonded body obtained after heating. Then, there is a problem that the generation of such a large void causes a decrease in the joint strength between the plate-shaped members.

This specification discloses a bonded body capable of effectively suppressing the generation of cavities in the bonded layer.

The bonded body disclosed in this specification includes a plurality of plate-shaped members arranged so as to be superposed on each other, and a sintered body that is interposed between the plate-shaped members to join the plate-shaped members to each other. It is provided with a layer, and at least one of the plate-shaped members has an internal gas passage that opens to the outer surface of the plate-shaped member through a joint surface facing the joint layer side of the plate-shaped member. is there.

According to the above-mentioned bonded body, the generation of cavities in the bonded layer can be effectively suppressed.

It is a perspective view which shows the junction of one Embodiment. It is sectional drawing which follows the line II-II of FIG. It is a perspective view of the plate-shaped member which shows the joint surface side of one plate-shaped member provided in the joint body of FIG. It is an enlarged cross-sectional view which shows only one plate-shaped member of FIG. It is a perspective view which shows one plate-like member provided in the joint body of another embodiment. It is sectional drawing which follows the VI-VI line of FIG. It is sectional drawing which shows the modification of the through hole provided in a plate-shaped member. It is a perspective view which shows the joint of still another embodiment. It is a top view which shows typically the groove shape of Examples 1-18.

The embodiments disclosed in this specification will be described in detail with reference to the drawings below.
As illustrated in FIGS. 1 and 2, the bonded body 1 of one embodiment includes a plurality of plate-shaped members 2, 3 arranged so as to overlap each other, for example, two plate-shaped members 2, 3 and the plate-shaped members 2, 3 thereof. It is provided with a bonding layer 4 including a sintered body that joins the plate-shaped members 2 and 3 to each other with an interposition between the two.

Here, at least one of the plurality of plate-shaped members 2, 3 shall be made of, for example, a metal material such as copper, aluminum or nickel, or an alloy thereof, and a material having a surface treatment such as plating on them. Can be done. Further, at least one plate-shaped member 2 or 3 can be made of a metal material such as copper and a copper alloy, a semiconductor chip such as Si or SiC, or a ceramic material such as a DCB substrate. The thickness of the plate-shaped members 2 and 3 can be, for example, 0.1 mm to 8.0 mm, typically 0.3 mm to 4.0 mm. Although not shown, it is also possible to further stack other plate-shaped members to provide three or more plate-shaped members. Further, not only the plate-shaped members are joined in parallel, but also one plate-shaped member 32 is erected at a right angle as shown in the joined body 31 shown in FIG. 8, and the other plate-shaped member 32 is erected on the side thereof. It is also possible to have a structure to be joined on top.

Further, here, the bonding layer 4 is mainly made of a sintered body of metal powder. Examples of the metal powder include copper powder and silver powder. The details of the bonding layer 4 will be described later, but by heating the metal powder paste at a predetermined temperature, the solvent, binder, etc. in the metal powder paste are removed, and the metal powder in the metal powder paste is baked. It was formed by connecting.
The average thickness of the bonding layers 4 and 34 is, for example, 3 μm to 400 μm, typically 5 μm to 100 μm. The average thickness of the joint layers 4 and 34 is a gap between the plate-shaped members 2 and 3 calculated by subtracting the thicknesses of the plate-shaped members 2 and 3 from the total thickness of the joint body 1. At this time, the total thickness of the bonded body 1 and the thicknesses of the plate-shaped members 2 and 3 are average values of the measured values measured at five points.

Until now, in order to produce a bonded body having such a bonded layer, heating with a metal powder paste sandwiched between two plate-shaped members has the following problems. That is, at the time of heating, the solvent in the metal powder paste interposed between the two plate-shaped members volatilizes, the binder decomposes, and the like, so that the two plate-shaped members are separated from each other. Gas is generated. This gas forms large cavities in the bonding layer of the bonded body after heating. Then, when a large cavity is formed in the bonding layer, the bonding strength between the two plate-shaped members decreases.

In response to this problem, in the illustrated embodiment, the plate-shaped member 2 passes through the joint surface Sb of the plate-shaped member 2 facing the joint layer 4 side, and the internal gas passage 5 opens to the outer surface of the plate-shaped member 2. Shall have. As a result, the gas generated from the metal powder paste during heating is smoothly discharged from the opening 5a of the internal gas passage 5 on the outer surface of the plate-shaped member 2 through the intended internal gas passage 5. As a result, it is possible to suppress the generation of unintended large cavities in the bonding layer 4, and it becomes easy to secure the required bonding strength.

As shown in FIG. 1, the internal gas passage 5 opens to the side surface Ss of the outer surface of the plate-shaped member 2, and the opening 5a of the internal gas passage 5 exists on the side surface Ss. By opening the internal gas passage 5 in the side surface Ss of the plate-shaped member 2, it is easier to process the groove formation than in the case where there is no opening or when a through hole is formed, and while suppressing the decrease in strength. It has the advantage that the material can be made lighter.

Further, in the embodiment shown in FIGS. 1 and 2, as can be seen from the fact that only one plate-shaped member 2 is turned upside down and shown in FIG. 3, it is recessed from the joint surface Sb and has a predetermined shape on the joint surface Sb. It is assumed that it has one or more extending groove portions 6, and at least a part of the internal gas passage 5 is composed of the groove portions 6. The internal gas passage 5 including such a groove 6 is preferable because it is easy to process and can be used even when the product cannot be penetrated through the plate-shaped member 2. Further, when the plate is erected at a right angle, it is extremely difficult to process the through hole, so the shape of the groove portion 6 is preferable.

In the front view of the joint surface Sb of the plate-shaped member 2, the form in which the groove 6 extends on the joint surface Sb is not particularly limited, but in this embodiment, as shown in FIG. 3, one side surface Ss side to the other. The four groove portions 6 extending linearly toward the side surface Ss side of the above surface are arranged side by side in parallel with a distance from each other. In the joint body 1 including the plate-shaped member 2, the internal gas passage 5 has openings 5a on both one side surface Ss and the other side surface Ss. However, a groove can be provided so that the internal gas passage opens only on either side surface. Further, the number of grooves may be one to three or five or more.

From the viewpoint of more smoothly discharging the gas generated during heating, a groove portion extending linearly from the central portion to the peripheral portion of the joint surface Sb is preferable. Although not shown, it is also possible to provide grid-like or radial grooves in the front view of the joint surface Sb. It should be noted that a curved groove portion, a groove portion that bends or branches in the middle, and the like are also conceivable.

The internal gas passage 5 may have a size and shape that allows gas that can be generated during heating to pass through and is discharged to the outside.
Specifically, when the plate-shaped member 2 is provided with the groove portion 6 for the internal gas passage 5, the groove width Wp of the groove portion 6 is 0.1 mm to 1.5 mm, and further, as shown in the enlarged cross-sectional view in FIG. It is preferably 0.15 mm to 1.2. If the groove width Wp is too narrow, the metal powder of the metal powder paste is likely to be clogged in the groove portion 6, which may hinder gas discharge. On the other hand, if the groove width Wp is too wide, the bonding strength may decrease due to the decrease in the bonding area with the other plate-shaped member 3. The groove width Wp is measured at a position farthest from the bottom Bp of the groove 6 (the lowest position in FIG. 4) in a direction orthogonal to the extending direction of the groove 6. If the groove width differs depending on the position of the groove, the average of 5 points or more is defined as the groove width Wp.

Further, the groove depth Dp of the groove portion 6 is preferably 0.01 mm to 1.5 mm and further 0.02 mm to 1.0 as measured along the plate thickness direction from the deepest point of the bottom portion Bp. .. When the groove depth Dp is shallow, the groove portion 6 may be filled with metal powder, and there is a concern that gas may not be discharged effectively. When the groove depth Dp is deep, the rigidity of the plate material may decrease.

Further, the distance between the adjacent groove portions 6 is preferably 0.3 mm to 6 mm. If the intervals between the grooves 6 are wide, there is a concern that gas may not be discharged effectively. On the other hand, if the intervals between the groove portions 6 are narrow, the joint strength may decrease. The distance between the groove portions 6 is measured along a direction orthogonal to the extending direction of any one of the adjacent groove portions 6. If the spacing differs depending on the position of the groove, the average value of 5 points or more shall be used.
In the example shown in FIG. 3, the groove portions 6 formed in the plate-shaped member 2 are arranged side by side in parallel, but in the embodiment in which the groove portions are arranged in a grid pattern, they are arranged adjacent to each other substantially in parallel. The spacing between the groove portions is preferably 3 times or more and less than 6 times the groove width.

Further, in the front view of the joint surface Sb, the ratio of the area of the groove 6 to the area of the joint surface Sb (the portion of the joint surface Sb without the groove 6) excluding the groove 6 (area ratio of the groove 6) is preferably 3. % To 70%, more preferably 5% to 50%, still more preferably 10% to 30%. If the area ratio of the groove portion 6 is too large, the joint area may decrease and the joint strength may decrease. Further, if the area ratio of the groove portion 6 is too small, the gas is insufficiently discharged from the internal gas passage 5 at the time of heating, and there is a concern that a somewhat large cavity may be generated in the joint layer 4.

When a plate-shaped member 2 having such a groove 6 provided on the joint surface Sb is to be joined to the other plate-shaped member 3 by using a metal powder paste, a part of the metal powder paste is a plate-shaped member 2. The metal powder may be sintered there in the state where it has entered the groove portion 6. However, even in this case, by adjusting the dimensional shape of the groove 6 so that the groove 6 of the plate-shaped member 2 is not completely filled with the metal powder, the gas from the internal gas passage 5 at the time of heating can be collected. It is possible to make the discharge good.

In the bonded body 1 obtained by heating in a state where the groove portion 6 is not completely filled with the metal powder in this way, as can be seen from FIG. 2, at least a part of the groove portion 6 on the bottom Bp side. , There will be a vacant Vp in which the bonding layer 4 has not entered. The joint body 1 having an empty Vp in the groove 6 of the plate-shaped member 2 is said to have sufficiently secured the required joint strength as a result of the gas being effectively discharged from the internal gas passage 5 during heating. Conceivable.

5 and 6 show a plate-shaped member 12 included in the joint of another embodiment. In the embodiment of FIG. 5, the plate-shaped member 12 is formed with one or more through holes 16 extending between the joint surface Sb and the surface Sf and opening in each of the joint surface Sb and the surface Sf. Then, the through hole 16 constitutes an internal gas passage 15 that opens to the surface Sf of the outer surface through the joint surface Sb. The through hole 16 extends linearly from the joint surface Sb toward the surface Sf, but may have various shapes such as a curved shape or a shape that bends in the middle. Further, it may be a through hole that opens in the side surface Ss.

In the internal gas passage 15 having the through holes 16 as shown in FIGS. 5 and 6, when the metal powder paste is heated, the gas generated by the internal gas passage 15 passes through the internal gas passage 15 and exists on the surface Sf of the plate-shaped member 12. It can be smoothly discharged from the opening 15a.

Further, even in the internal gas passage 25 formed of the through hole 26 as shown in FIG. 7, the gas at the time of heating the metal powder paste can be effectively discharged.
The internal gas passage 25 has the internal gas shown in FIGS. 5 and 6 except that the vicinity of the opening of the through hole 26 on the joint surface Sb side is enlarged and a recess 26a recessed from the joint surface Sb is provided therein. It has substantially the same configuration as the passage 25. In the internal gas passage 25 including the recess 26a recessed in the joint surface Sb as shown in FIG. 7, instead of the groove 6 of FIG. 3 extending on the joint surface Sb as described above, for example, the outer surface such as the surface Sf of the through hole 26 By opening the opening 25a, gas effectively flows out from the opening 25a. Thereby, even in this internal gas passage 25, it is possible to suppress the generation of a large cavity due to the generation of gas.

Although not shown, an internal gas passage may be formed by combining a groove provided in the plate-shaped member and a through hole.
Further, the internal gas passage can be provided in the other plate-shaped member, or may be provided in both the one plate-shaped member and the other plate-shaped member.

The method for producing the bonded body as described above will be described by taking the bonded body 1 shown in FIG. 1 as an example.
First, the plate-shaped members 2 and 3 are prepared. Here, the groove 6 is provided in one of the plate-shaped members 2 by cutting or other processing, casting, molding, or the like.

Next, the metal powder paste is applied to the joint surface Sb of one plate-shaped member 2, the joint surface of the other plate-shaped member 3, or both joint surfaces thereof using an applicator or the like. Then, the plate-shaped members 2 and 3 are overlapped with the two joint surfaces facing each other. As a result, the metal powder paste is sandwiched and intervened between the plate-shaped members 2 and 3.

Then, the plate-shaped members 2 and 3 superposed on each other are heated under the intervention of the metal powder paste. At this time, the solvent, binder, etc. contained in the metal powder paste generate gas between the plate-shaped members 2 and 3, and the gas passes through the internal gas passage 5 provided in the plate-shaped member 2 as described above. Therefore, it is smoothly discharged from the opening 5a on the outer surface of the plate-shaped member 2. As a result, the generation of large cavities in the joint layer 4 formed after heating is suppressed, and the required joint strength between the plate-shaped members 2 and 3 can be effectively secured.

Further, the space of the internal gas passage 5 such as the groove 6 also functions to alleviate the stress caused by the volume reduction due to the sintering of the metal powder and prevent the occurrence of cracks in the bonding layer 4, so that the bonding strength is increased. The decrease can be suppressed more effectively.

Here, it is desirable that heating is performed in several steps. For example, as the first step, the temperature of 80 ° C. to 150 ° C. can be maintained for 3 to 60 minutes. Heating at this temperature volatilizes the solvent in the paste. At this time, large cavities are likely to occur in the joint layer. Since the solvent does not volatilize when the heating temperature is low, cavities are created in the next heating step. The above temperature and time are desirable because large cavities are generated when the heating temperature is high. Heat treatment for sintering is performed in the second and subsequent steps. In the second step, heat treatment at 400 to 900 ° C. for 5 to 60 minutes is carried out to obtain a densely fired bonded layer. If the temperature is too low, the metal powder itself is only lightly fired, so that the metal powder becomes a porous shape in which the metal powders are sparsely connected to each other, and the difference in thermal expansion between the plate-shaped members 2 and 3 is easily alleviated. Cannot be increased. By raising the temperature to a relatively high temperature as in the above temperature range, a dense bonding layer 4 is obtained, and the bonding strength is greatly increased. Further, since the gas that is likely to be generated by high-temperature heating flows out satisfactorily from the internal gas passage 5 as described above, the problem of cavities does not occur.

At the time of heating, it is possible to pressurize as necessary, but if the metal powder paste is sandwiched between the plate-shaped members 2 and 3 and heated, the plate-shaped members 2 and 3 are firmly joined without pressurization. It is possible. Before stacking the plate-shaped members 2 and 3, the solvent contained in the metal powder paste on the joint surface of any of the plate-shaped members 2 and 3 is volatilized, and then the plate-shaped members 2 and 3 are superposed. In the case of heating, it is often necessary to pressurize for joining.

As a result, it is possible to obtain a bonded body 1 in which the plate-shaped members 2 and 3 are firmly bonded to each other by the bonding layer 4.

Next, the above-mentioned joint was prototyped and its effect was confirmed, which will be described below. However, the description here is for the purpose of mere illustration, and is not intended to be limited thereto.

With the metal powder paste sandwiched between two copper test pieces simulating a plate-shaped member, the metal powder paste is heated to 120 ° C. as the first step heating, and then heated to 800 ° C. as the second step heating. Then, a metal powder was sintered between the two plate-shaped members to form a joint layer. As the metal powder paste, a paste in which copper powder was dispersed in a solvent, a binder or the like was used. The size of the test piece was 10 × 10 × 1.5 t (mm), and the coating thickness of the metal powder paste was 0.1 mm.

Here, as shown in Table 1, the joints of Examples 1 to 23 and Comparative Examples 1 and 2 having different forms of grooves or through holes provided on the joint surface of the test piece were produced by the above method. The groove shapes of Examples 1 to 18 are shown in FIG.

For these bonded bodies, a test was conducted in which the bonded strength was measured by peeling off the bonded copper test pieces. The results are also shown in Table 1. In Table 1, four stages of "x", "Δ", "○", and "◎" are shown in order from the one with the lowest bonding strength to the one with the highest bonding strength. “X” means that the material was easily peeled off (the joint strength is low), and “◎” means that the material was forcibly peeled off and finally peeled off (the joint strength is high). “△” means that peeling was possible when a little force was applied, and “○” means peeling when a force stronger than “△” and weaker than “◎” was applied. Means that was possible.

From Table 1, it can be seen that in Examples 1 to 23, the area ratio of the cavities was reduced to some extent, and relatively high bonding strength was obtained. It is considered that this is because the gas was effectively discharged from the internal gas passage during heating, and the generation of large cavities in the joint layer was effectively suppressed. On the other hand, in Comparative Examples 1 and 2, the area ratio of the cavity increased and the joint strength decreased.

1, 31 Joined body 2, 3, 12, 32 Plate-shaped member 4, 34 Joined layer 5, 15, 25, 35 Internal gas passage 5a, 15a, 25a, 35a Opening 6 Groove 16, 26 Through hole 26a Recessed Ss Side surface Sb Joint surface Sf Surface Wp Groove width Dp Groove depth Vp Vacancy

Claims (9)

A bonded body including a plurality of plate-shaped members arranged so as to be superposed on each other, and a bonding layer including a sintered body that is interposed between the plate-shaped members and joins the plate-shaped members to each other.
A joint body in which at least one plate-shaped member has an internal gas passage that opens to the outer surface of the plate-shaped member through a joint surface facing the joint layer side of the plate-shaped member. The joint according to claim 1, wherein the internal gas passage opens on a side surface of the outer surface of the plate-shaped member. The bonded body according to claim 1 or 2, wherein the plate-shaped member has a groove portion recessed from the joint surface and extends on the joint surface, and at least a part of the internal gas passage is composed of the groove portion. .. The bonded body according to claim 3, wherein the groove width of the groove portion is 0.1 mm to 1.5 mm. The joint according to claim 3 or 4, wherein the groove depth of the groove is 0.01 mm to 1.5 mm. The joint according to any one of claims 3 to 5, wherein the area ratio, which is the ratio of the area of the groove to the area of the joint surface excluding the groove, is 3% to 70%. The joint according to any one of claims 3 to 6, wherein the plate-shaped member has a plurality of the groove portions, and the distance between the plurality of groove portions is 0.3 mm to 6 mm. The joint according to any one of claims 3 to 7, wherein a vacant space without a joint layer exists in at least a part on the bottom side of the groove. The bonded body according to any one of claims 1 to 8, wherein at least one of the plate-shaped members bonded to each other by the bonding layer is made of a metal material.

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