JP2020155498A - Joined body and method for manufacturing joined body - Google Patents

Abstract

To provide a joined body capable of effectively suppressing the occurrence of cavities into a junction layer, and a method for manufacturing a joined body.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 to mutually join the plate-like members 2, 3. The junction layer 4 has an internal gas passage 5 which passes through the inside of the junction layer 4 and opens to a side surface Ss of the junction layer 4.SELECTED DRAWING: Figure 1

Description

This specification discloses a joint and a technique relating to a method for producing the joint.

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 cavity causes a decrease in the joint strength between the plate-shaped members.

In this specification, a joint body capable of effectively suppressing the generation of cavities in the joint layer and a method for producing the joint body are disclosed.

The joint body disclosed in this specification includes a plurality of plate-shaped members arranged so as to be overlapped with each other, and a joint layer interposed between the plate-shaped members to join the plate-shaped members to each other. The bonding layer has an internal gas passage that passes through the inside of the bonding layer and opens to the side surface of the bonding layer.

The method for producing a joined body disclosed in this specification is to join at least two plate-shaped members and a member preparation step for preparing a metal powder paste, and one plate-shaped member and / or the other joining member to each other. A paste application step in which a metal powder paste is applied to the joint surface to be used and a groove extending to the outer edge of the paste application area is provided in the paste application area, and a plate-shaped member on which the metal powder paste is sandwiched and overlapped with each other is heated. Then, the metal powder paste has a heating step of forming a bonding layer for bonding the plate-shaped members to each other.

According to the above-mentioned joint body and the method for producing the joint body, the generation of cavities in the joint layer can be effectively suppressed.

It is a perspective view which shows typically the junction of one Embodiment. It is sectional drawing which follows the line II-II of FIG. It is a perspective view which shows the mode of applying the metal powder paste to the plate-shaped member at the time of manufacturing the joint body of FIG. It is a perspective view which shows the other application mode of the metal powder paste to a plate-shaped member. It is a perspective view which shows the joint layer by removing one plate-like member of the joint body of FIG. It is a perspective view which shows the joint layer by removing one plate-like member of the joint body manufactured by the coating mode of FIG. It is a partially enlarged sectional view which shows the joint layer of the joint body of another embodiment. It is a perspective view which shows the joint of still another embodiment. It is a schematic plan view which shows the paste coating area of Examples 1-12 and Comparative Examples 1 and 2.

The embodiments disclosed in this specification will be described in detail with reference to the drawings below.
As illustrated in FIGS. 1 and 2, a plurality of, for example, two plate-shaped members 2, 3 and their plate-shaped members 2, 3 are arranged so as to overlap each other. It is provided with a bonding layer 4 that joins the plate-shaped members 2 and 3 to each other by interposing between the two. The joint layer 4 represents a portion including a space between one plate-shaped member 2 and the other plate-shaped member 3. In other words, the bonding layer 4 is a concept including a sintered body such as the bonding layer segment 4a described later and a space such as the internal gas passage 5.

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 composed of a sintered body of metal powder and an internal gas passage 5 described later. 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 14 is, for example, 3 μm to 400 μm, typically 5 μm to 100 μm. The average thickness of the joint layers 4 and 14 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.

In the joint body 1, the joint layer 4 is provided with an internal gas passage 5 that passes through the inside of the joint layer 4 and opens to the side surface Ss of the joint layer 4. The internal gas passage 5 extends inside the bonding layer 4 and has an opening 5a on the side surface Ss. The side surface Ss of the bonding layer 4 means a peripheral surface exposed to the outside between the plate-shaped members 2 and 3, and there are four surfaces in this embodiment.

As a result, it is possible to effectively suppress a decrease in the bonding strength due to the gas that may be generated from the metal powder paste during heating when the bonded body 1 is manufactured.

More specifically, during heating in the production of the bonded body 1, the solvent in the metal powder paste interposed between the two plate-shaped members volatilizes, the binder decomposes, and the like. Gas is generated between the two plate-shaped members. 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.
On the other hand, in this embodiment, since the bonding layer 4 has the above-mentioned internal gas passage 5, the gas generated from the metal powder paste during heating passes through the intended internal gas passage 5 and the side surface of the bonding layer 4. The gas is smoothly discharged from the opening 5a of the internal gas passage 5 in Ss. 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.

An example of a method for manufacturing the bonded body 1 including the formation of the internal gas passage 5 in the bonded layer 4 will be described below.
First, a member preparation step for preparing at least two plate-shaped members 2 and 3 and a metal powder paste is performed.

Next, the metal powder paste Pm is applied to at least one of the joint surfaces of the two plate-shaped members 2 and 3 to be joined to each other, for example, the joint surface of the plate-shaped member 3, using an applicator or the like. Perform the paste application step.

At this time, as shown in FIG. 3, a groove portion 6 extending to the outer edge of the paste application area is provided in the paste application area Ap on the plate-shaped member 3. The groove 6 is recessed from the surface of other parts of the paste coating area Ap by partially eliminating the metal powder paste Pm in the paste coating area Ap or partially reducing the coating thickness of the metal powder paste Pm. Can be provided. A small amount of metal powder paste Pm may be present in the groove portion 6.

To form the groove 6 in the paste coating area Ap, for example, after applying the metal powder paste Pm to the entire paste coating area Ap, the metal powder paste Pm is partially removed according to the shape of the groove 6 or , The paste application area Ap is covered with a cover hollowed out into a predetermined shape corresponding to the shape of the groove portion 6, and the metal powder paste Pm is applied from above the paste application area Ap.

The shape of the groove 6 in the plan view of the paste coating area Ap may be appropriately selected as long as it extends from the inside of the paste coating area Ap to the outer edge of the paste coating area Ap.
In the place shown in FIG. 3, in the plan view of the paste application area Ap, a plurality of linear grooves (four in the example of FIG. 3) parallel to each other are arranged so as to intersect at substantially right angles to form a grid-like portion. The groove portion 6 to have is provided. The lattice-shaped portion need only have intersecting grooves, and includes those composed of curved grooves and those having non-right-angled intersection angles.
On the other hand, in FIG. 4, the groove portion 16 is formed by a plurality of linear grooves (four in the example of FIG. 3) arranged in parallel with each other in the plan view of the paste application area Ap.
Although not shown, a curved groove, a groove that bends or branches in the middle, and the like are also possible. Further, a groove portion having a radial portion including a plurality of grooves extending linearly, curvedly, or bent from the vicinity of the center of the joint layer in a plan view to the outside is also effective. The number of grooves constituting the groove portion may be one or more.
The shapes of the grooves 6 and 16 can correspond to the shape of the internal gas passage of the joint layer in the joint body manufactured through the heating step described later.

Then, the plate-shaped members 2 and 3 are superposed in a direction in which both joint surfaces thereof face each other. As a result, the metal powder paste Pm applied by providing the groove portion 6 or the like in the paste application area Ap is sandwiched between the plate-shaped members 2 and 3. At this time, in the portion provided with the groove portion 6 or the like in the paste application area Ap, the amount of the metal powder paste Pm is smaller than that in the peripheral portion, and a passage is formed there. When the plate-shaped members 2 and 3 are overlapped with each other, pressure is applied to the metal powder paste Pm, and the area of the groove portion 6 becomes smaller. Therefore, the paste coating area Ap can be appropriately set based on the thickness of the metal powder paste Pm and the pressure applied to the metal powder paste Pm so that the groove portions 6 are not crosslinked by the metal powder paste Pm adjacent to each other.

After that, in the heating step, the plate-shaped members 2 and 3 superposed on each other are heated under the intervention of the metal powder paste Pm. At this time, the solvent, binder, etc. contained in the metal powder paste Pm generate gas between the plate-shaped members 2 and 3, and the gas is provided in the paste application area Ap of the metal powder paste Pm as described above. It is smoothly discharged from the outer edge (side surface Ss of the bonding layer 4) of the paste coating area Ap through the internal gas passage 5 formed by the groove portion 6 and the like. 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, since the internal gas passage 5 due to the groove portion 6 or the like is present, the volume reduction due to the sintering of the metal powder is alleviated, and the function also functions to prevent the occurrence of cracks in the bonding layer 4, so that the bonding strength is reduced. Can be suppressed more effectively.

Here, it is desirable to perform heating 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 needed, but if the metal powder paste Pm is sandwiched between the plate-shaped members 2 and 3 and heated, the plate-shaped members 2 and 3 can be firmly pressed without pressurization. Can be joined. Before stacking the plate-shaped members 2 and 3, the solvent contained in the metal powder paste Pm 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 stacked. When heated together, pressurization is often required to join.

In the bonded body 1 manufactured as described above, the plate-shaped members 2 and 3 are firmly bonded to each other by the bonding layer 4.

Then, the internal gas passage 5 of the joint layer 4 provided in the joint body 1 is provided in the paste coating area Ap of FIG. 3 as shown in FIG. 5 when one plate-shaped member 2 is removed from the joint body 1 and observed. It has a grid-like portion having substantially the same shape as the groove portion 6. The bonding area of the bonding layer segment 4a is larger than the coating area of the metal powder paste Pm due to the pressure applied to the metal powder paste Pm when the plate-shaped members 2 and 3 are overlapped. Therefore, the internal gas passage 5 does not completely correspond to the groove portion 6 provided in the paste application area Ap.
Further, when the groove portion 16 as shown in FIG. 4 is provided in the paste coating area Ap, the internal gas passage 15 of the joint layer 14 in the bonded body produced by the groove portion 16 is formed in the groove portion 16 of FIG. It has a plurality of linear portions having substantially the same shape as the above, which are arranged in parallel with each other and extend linearly.

Further, these bonding layers 4 and 14 are partitioned into a plurality of bonding layer segments 4a and 14a by the internal gas passages 5 and 15 due to the presence of the internal gas passages 5 and 15 opening to the side surface SS inside. ing.

In FIG. 5, since the internal gas passages 5 form a grid in a plan view, each joint layer segment 4a constituting the joint layer 4 has a cube, a rectangular parallelepiped, or other rectangular shape. Further, in FIG. 6, rod-shaped joint layer segments 14a having a rectangular cross section are arranged side by side in parallel with each other by the grooves of a plurality of parallel linear portions. However, when the plate-shaped members 2 and 3 are overlapped with each other, a force is applied to the metal powder paste Pm to deform it, so that the shape does not match the shape of a perfect cube or rectangular parallelepiped.

It is preferable that each of the bonding layer segments 4a and 14a has a diameter of a maximum circle inscribed in the bonding layer segments 4a and 14a of 4 mm or less in a plan view of the bonding layer 4 and 14. As a result, the distance at which the gas generated in the metal powder paste Pm diffuses to the outside of the metal powder paste Pm can be suppressed, and the formation of cavities can be suppressed. If the diameter of the maximum inscribed circle is larger than 4 mm in one or more of the bonding layer segments 4a and 14a, there is a concern that cavities will be generated in the bonding layer segments 4a and 14a and the bonding force will be reduced. .. From this point of view, it is more preferable that the diameter of the maximum inscribed circle is 2 mm or less.

FIG. 7 shows the bonded body 21 of another embodiment.
In the joint body 21 of FIG. 7, similarly to the joint body 1 described above, the joint layer 24 has an internal gas passage 25 that passes through the inside thereof and opens to the side surface Ss. However, in the joint body 21, a thin portion 24a of the sintered body of the joint layer 24 is interposed between the internal gas passage 25 and the joint surface of one plate-shaped member 22. More specifically, the internal gas passage 25 reaches the other plate-shaped member 23 but does not reach the one plate-shaped member 22 in the plate thickness direction (vertical direction in FIG. 7), and is formed by the thin-walled portion 24a. , Is located away from the joint surface of one of the plate-shaped members 22.

In such a bonded body 1, although the bonded layer 24 does not have the bonded layer segment described above, gas is effectively degassed during heating in the internal gas passage 25, so that it is effective to generate cavities in the bonded layer 24. Can be suppressed.

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 bonded bodies of Examples 1 to 12 and Comparative Examples 1 and 2 having different forms of the paste application area of the metal powder paste applied on the test piece were prepared by the above method. FIG. 9 shows the planar shapes of the paste coating areas of Examples 1 to 12 and Comparative Examples 1 and 2.

Table 1 also shows the results of tests for measuring the bonding strength of these bonded bodies by peeling off the bonded copper test pieces. 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, in Examples 1 to 12, the area ratio of the cavity is reduced as a result of the effective discharge of the gas during heating by the internal gas passage opening on the side surface of the bonding layer, and the bonding strength is relatively high. was gotten. On the other hand, in Comparative Examples 1 and 2, the area ratio of the cavity was large and the joint strength was low. It is considered that this is because Comparative Example 1 did not have an internal gas passage, and Comparative Example 2 did not open the internal gas passage to the side surface, so that a large cavity was generated by the gas during heating.

1, 21, 31 Joined body 2, 3, 22, 23, 32, 33 Plate-shaped member 4, 14, 24, 34 Joint layer 24a Thin-walled part of sintered body 5, 15, 25, 35 Internal gas passage 5a, 15a Opening 6, 16 Groove Ss Side surface t Average thickness of joint layer Ap Paste application area Pm Metal powder paste

Claims (9)

It is a joint body including a plurality of plate-shaped members arranged so as to be superposed on each other and a bonding layer that is interposed between the plate-shaped members to join the plate-shaped members to each other.
A bonded body in which the bonded layer has an internal gas passage that passes through the inside of the bonded layer and opens to a side surface of the bonded layer. The junction according to claim 1, wherein the junction layer has a plurality of junction layer segments partitioned by the internal gas passage. The bonded body according to claim 2, wherein the diameter of the maximum circle that can be inscribed in the bonded layer segment is 4 mm or less in a plan view of the bonded layer. The bonded body according to claim 1 to 3, wherein the internal gas passages are arranged in parallel with each other and have a plurality of linear portions extending linearly in a plan view of the bonded layer. The bonded body according to any one of claims 1 to 4, wherein the internal gas passage has a grid-like portion in a plan view of the bonded layer. The bonded body according to any one of claims 1 to 5, wherein the internal gas passage has a radial portion in a plan view of the bonded layer. A method of manufacturing a joint
A member preparation step for preparing at least two plate-shaped members and a metal powder paste, and
A paste coating step in which a metal powder paste is applied to the bonding surfaces of one plate-shaped member and / or the other bonding member to be bonded to each other, and a groove extending to the outer edge of the paste application area is provided in the paste application area. ,
A method for producing a bonded body, which comprises a heating step of heating plate-shaped members which are overlapped with each other with the metal powder paste sandwiched between them, and forming the metal powder paste into a bonding layer for joining the plate-shaped members to each other. The method for producing a bonded body according to claim 7, wherein in the paste coating step, the grooves are formed of a plurality of linear grooves arranged in parallel with each other in a plan view of the paste coating area. The method for producing a bonded body according to claim 7 or 8, wherein in the paste coating step, the grooves are provided in a grid pattern in a plan view of the paste coating area.

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