WO2024042791A1

WO2024042791A1 - Heat conductive joining structure, heat conductive joining method, heat sink having said heat conductive joining structure, and semiconductor device having said heat conductive joining structure

Info

Publication number: WO2024042791A1
Application number: PCT/JP2023/018545
Authority: WO
Inventors: 拓哉井手; 政明村上; 富行沼田; 裕章巽
Original assignee: 株式会社ロータス・サーマル・ソリューション; 国立大学法人大阪大学
Priority date: 2022-08-25
Filing date: 2023-05-18
Publication date: 2024-02-29
Also published as: JP2024030766A

Abstract

[Problem] To provide a heat conductive joining technology which is suitable for a joining structure of a semiconductor device, is capable of mitigating stress due to thermal deformation and preventing damage and peeling of a joining part, ensures low thermal resistance, and is capable of enhancing heat dissipation through heat transfer between members, and With which it is possible to maintain durability as a device without maintaining stiffness between the members in the stacking direction thereof, and maintain parallelism between the members during joining and assembly to enhance assembly accuracy. [Solution] This structure, which is composed of a joining layer 10 which is in close contact with a member 9 and performs heat transfer between the structure and the member 9, comprises: a metal-made porous base plate 11 having a plurality of through-holes 111 which extend in the thickness direction of the plate and are open in the front and rear plate surfaces of the plate; and a solder solidified body 12 composed of a filling part 121 filled in the though-holes 111 of the porous base plate 11, and solder films 122, 123 which are continuous to the filling part and expand on at least one plate surface, wherein the structure is brought into close contact with and joined to the facing member 9 by means of the solder film 122.

Description

A thermally conductive bonding structure, a thermally conductive bonding method, a heat sink having the thermally conductive bonding structure, and a semiconductor device having the thermally conductive bonding structure

The present invention relates to a thermally conductive bonding structure suitable for a bonding structure between a heat receiving body of a heat sink and a heat dissipating fin, a bonding structure for various parts of a semiconductor device, and a thermally conductive bonding method.

In recent semiconductor devices, especially power semiconductor devices, the amount of heat generated by the semiconductor chip is increasing as the current density increases. In addition, as semiconductor devices are expected to become smaller, it is becoming more important to efficiently transport the heat from semiconductor chips that generate a large amount of heat to a heat sink, which is a cooler, and then dissipate the heat from the heat sink into a gas or liquid phase coolant. It has become. In a typical semiconductor device, for example, a circuit board and a semiconductor chip are stacked on a base plate, and a heat sink is attached to the lower surface of the base plate. A heat conductive sheet is provided between each laminated member to maintain good heat conduction and join the members together (for example, see Patent Document 1).

Incidentally, a semiconductor device has a structure in which a plurality of members (semiconductor chips, circuit boards, base plates, etc.) having different coefficients of linear expansion are bonded to each other and stacked. Therefore, the large temperature change caused by the heat generation causes thermal strain in various parts of the semiconductor device, and damage and peeling of the heat conductive sheet, which is the bonding part, becomes a particular problem. In order to prevent damage to the joint due to such thermal strain, it may be possible to use a solder layer that has low rigidity and can relieve stress in place of the thermally conductive sheet. However, solder has a relatively high thermal resistance, resulting in poor heat dissipation through heat conduction between members. Furthermore, rigidity cannot be maintained in the lamination direction between the members, that is, in the plate thickness direction perpendicular to the joint surfaces, and there is a limit to the durability of the device. Furthermore, it is difficult to maintain parallelism between members during joining and assembly, and there is also a problem in terms of assembly accuracy.

Japanese Patent Application Publication No. 11-58591 (Japan)

Therefore, in view of the above-mentioned situation, the present invention aims to solve the problem by being suitable for the bonding structure of semiconductor devices, being able to alleviate stress caused by thermal strain, preventing damage and peeling of the bonded portion, and having low thermal resistance. , Thermal conduction bonding technology can improve heat dissipation through heat conduction between components, and can be expected to be smaller and have a longer lifespan.Furthermore, it can maintain rigidity in the stacking direction between components, making it possible to bond with durability. The object of the present invention is to provide a heat conductive joining technology that can maintain parallelism between members during assembly and improve assembly accuracy.

In view of the current situation, the inventors of the present invention have conducted intensive studies and found that by combining a metal plate having a plurality of through holes extending in the thickness direction with solder, stress can be alleviated in the horizontal direction parallel to the surface, and damage can occur. The bonded structure not only prevents peeling and peeling, but also suppresses thermal resistance in the thickness direction (thickness direction), has excellent thermal conductivity, maintains rigidity in the thickness direction, and achieves assembly accuracy. We have discovered that this can be realized and that such a thermally conductive bonding structure is effective for applications other than semiconductor devices, and furthermore, we have discovered that this can be applied to a new bonding structure between a heat receiving body and a heat dissipation fin of a heat sink, and have developed the present invention. I was able to complete it.
In addition, under the experimental conditions shown below, we investigated changes in thermal conductivity in the thickness direction and apparent rigidity in the in-plane direction when changing the volume ratio of the metal plate (copper plate) and solder. I got the graph. From this graph, it can be seen that the larger the volume of the metal plate (the volume of the flesh part excluding holes) (the smaller the porosity), the higher the thermal conductivity will be proportionally, but the apparent stiffness in the in-plane direction will increase at an accelerating rate. I know what will happen. From this, in order to satisfy both thermal conductivity and stress relaxation, the volume of the metal plate should be 70 vol% or less (porosity is 30 vol% or more), and more preferably the volume of the metal plate should be 20 vol% or more. It has been found that it is preferable to set the porosity in a range of 70 vol% or less (porosity of 30 vol% or more and 80 vol% or less).
(Experimental conditions)
・Bonding layer thickness: 200μm
・Solder: SAC305 (Sn-3mass%Ag-0.5mass%Cu)
・Thermal conductivity measuring device: TCM1001 (manufactured by Resca Co., Ltd.)

That is, the present invention includes the following inventions.
(1) A thermally conductive bonding structure consisting of a bonding layer that closely adheres to a certain member and conducts heat between the bonding layer and the bonding layer, which has a plurality of bonding layers extending in the thickness direction and opening on both the front and back surfaces. Consisting of a metal porous base plate in which a through hole is formed, a filling part filled in the through hole of the porous base plate, and a solder film that extends on at least one plate surface in continuity with the filling part. a solder solidified body, and the solder film is closely bonded to the facing member.

(2) A thermally conductive bonding structure consisting of a bonding layer provided between two members to bond the two members and transmit heat from one of the two members to the other, the bonding layer extending in the thickness direction. a metal porous base plate having a plurality of through holes opening on both the front and back surfaces and interposed between the two members; a filling portion filled in the through holes of the porous base plate; A solidified solder body consisting of a solder film extending over both plate surfaces continuously from the filling part, and the solder film is closely joined to two members facing each other.

(3) The thermally conductive bonding structure according to (1) or (2), wherein the porous base plate constituting the bonding layer has a porosity due to the through holes of 30 to 80 vol%.

(4) A thermally conductive bonding method in which a bonding layer is provided that closely adheres to a certain member and conducts heat between the member, and the bonding layer extends in the thickness direction and opens on both the front and back surfaces of the plate. A metal porous base plate in which a plurality of through holes are formed is provided, and a solder material is filled in the through holes of the porous base plate, and spreads on at least one plate surface continuously from the filled portion. A thermally conductive bonding method, wherein a solidified solder body is provided with a solder film formed thereon, and the solder film is closely bonded to the member facing the member.

(5) A thermally conductive bonding method in which a bonding layer that transfers heat from one of the two members to the other is provided between the two members to bond the two members, the bonding layer being a bonding layer that extends in the thickness direction and has a A metal porous base plate in which a plurality of through holes opening to the plate surface are formed is interposed between the two members, and a solder material is filled in the through holes of the porous base plate, and A thermally conductive bonding method in which a solidified solder is provided in a filled part and solidified with a solder film that spreads continuously over both plate surfaces, and the solder film is bonded to two facing members in close contact with each other. .

(6) The solder material is interposed between one or both of the front and back surfaces of the porous base plate and the member facing thereto, and the member, the porous base plate, and the solder material are stacked. heating the porous base plate to melt the solder material, filling the through hole of the porous base plate with the solder material, and forming a solder film that extends continuously over the filled portion and on both plate surfaces. The thermally conductive bonding method according to (4) or (5), wherein the solidified solder is formed by cooling and solidifying.

(7) With the two members, the porous base plate, and the solder material stacked vertically, and the solder material placed on the upper surface side of the porous base plate, heat is applied to melt the solder material. Then, due to the solder material's own weight and the load from the upper member, it falls into the through hole and fills it, and leaks from the lower opening of the through hole and fills the gap between the porous base plate and the lower member. The thermally conductive bonding method according to (6), wherein the solder film is spread out on the lower plate surface, and the remaining solder material that did not fall into the through hole forms the solder film on the upper plate surface.

(8) A heat sink having the thermally conductive bonding structure described in (1), wherein the heat sink has a contact surface that comes into contact with the object to be cooled, and the heat of the object to be cooled is transferred through the contact surface. A metal heat absorber as a member, and a metal plate-like fin as the porous base plate, a part of the plate surface of which is joined to a surface opposite to the contact surface of the heat absorber. , a plurality of through holes opening to the plate surface are formed in the plate-shaped fin, and the filling portion is filled in the through-hole formed in the partial area of the plate-shaped fin. , and has the solder solidified body made of the solder film that extends over the plate surface continuously in the filling part, and the solder film is in close contact with the facing heat absorbing body, and heat is not generated between the solder film and the heat absorbing body. A heat sink in which the conductive bonding layer is formed and heat is radiated to the outside through a through hole in a remaining region protruding around the heat absorbing body of the plate-like fin.

(9) A heat sink having the thermally conductive bonding structure described in (2), which has a contact surface that comes into contact with the object to be cooled, and the heat of the object to be cooled is transmitted through the contact surface. A metal heat absorber as one of the members, and a metal heat absorber as the porous base plate, a part of the plate surface being joined to the surface opposite to the contact surface of the heat absorber. A first plate-like fin and the other member of the two members joined to a region corresponding to the partial region of the plate surface opposite to the plate surface of the first plate-like fin. A metal connecting body and a metal second plate-like fin having a partial region of the plate surface joined to a surface of the connecting body opposite to the surface joined to the first plate-like fin. The first plate-like fin and the second plate-like fin each have a plurality of through-holes opening to the plate surface, and the partial area of the first plate-like fin has a plurality of through holes formed in the first plate-like fin and the second plate-like fin. The solidified solder body is comprised of the filling part filled in a through hole formed in the through hole, and the solder film extending continuously to the filling part and spreading over both plate surfaces, and the solder film faces each other. The bonding layer is formed to be in close contact with the heat absorbing body and the connecting body, respectively, and transmitting heat from the heat absorbing body to the connecting body, and the remaining portion of the first plate-shaped fin protrudes around the heat absorbing body and the connecting body. A heat sink that radiates heat to the outside through a through hole in the region and a through hole in the remaining region protruding around the connecting body of the second plate-like fin.

(10) Comprising a base plate, a circuit board bonded onto the base plate, and a semiconductor chip bonded onto the circuit board, and between the two members of the base plate and the circuit board, and the circuit board. A semiconductor device having the thermally conductive bonding structure according to (2), which includes the bonding layer between at least one of the two members, a substrate and a semiconductor chip.

(11) The thermally conductive bonding structure according to (2), wherein a heat sink is provided on the lower surface side of the base plate on which the circuit board and the semiconductor chip are stacked, and the bonding layer is provided between the two members of the base plate and the heat sink. A semiconductor device having:

According to the thermally conductive bonding structure/thermal conductive bonding method of the present invention, the metal porous base plate whose through holes are filled with solder can easily expand and contract in the horizontal direction parallel to the bonding surface, thereby relieving stress. Moreover, since the filled portion continuous with the solder film has an anchor effect, damage and peeling can be prevented. In other words, a porous base plate having multiple through holes in the thickness direction can be deformed in the horizontal direction to relieve stress, and the solder filled portion in each through hole is shaped like a rod in the thickness direction. Therefore, it is easy to bend in the horizontal direction, and the relaxation of stress in this direction is further promoted. The filling portion that is continuous with the solder film and filled in each through hole serves as an anchor to maintain strong integrity and adhesion between the solder film and the porous base plate.

In addition, it has a solder film that tightly adheres to the component, but since the through hole that is filled with solder is surrounded by a metal plate, the thermal resistance along the plate thickness direction is small, and it has excellent adhesion to the component. Has thermal conductivity. Since the through-holes are filled with solder, an increase in thermal resistance due to the presence of voids can be avoided, and the solidified solder and the porous base plate have a wide contact area through the filled portions filled in the through-holes. Therefore, the heat received by the solder film can be efficiently transferred to the porous base plate.

Furthermore, since each through hole in the porous base plate extends in the thickness direction, excellent rigidity is maintained in the thickness direction perpendicular to the joint surface. Further, since the solder filling portion filled in each through hole has a rod shape extending in the plate thickness direction as described above, the rigidity in the plate thickness direction, which is the axial direction, is further improved. Therefore, accuracy during assembly can be easily achieved. In other words, a bonded structure with low thermal resistance and excellent thermal conductivity can be realized with the designed thickness, parallelism, and other precision.

Here, it is preferable that the porous base plate constituting the bonding layer has a porosity of 30 to 80 vol% due to the through holes. If the porosity is less than 30%, the stress relaxation effect tends to be small. Moreover, when it is larger than 80%, the vertical rigidity decreases, the whole is easily deformed, and the accuracy of the joints such as thickness cannot be maintained.

In addition, a solder material is interposed between one or both of the front and back surfaces of the porous base plate and the member facing it, and the member, the porous base plate, and the solder material are heated in a stacked state, and the solder material is The solder is solidified by melting the solder material, filling the through holes of the porous base plate, and cooling and solidifying the solder film forming a solder film that spreads continuously over both plate surfaces in the filled part. According to the method of forming the body, it is possible to realize the thermally conductive bonding structure according to the present invention efficiently and with high precision.

When installing between two members, the two members, the porous base plate, and the solder material are stacked vertically, and the solder material is placed on the upper surface of the porous base plate, and heated to melt the solder material. Due to the weight of the solder material and the load from the upper member, the solder material falls into the through hole and fills it, and it also leaks from the lower opening of the through hole and spreads into the gap between the porous base plate and the lower member. The method of forming the solder film on the side plate surface and using the remaining solder material that did not fall into the through hole to form the solder film on the upper plate surface allows efficient and accurate heat conduction of the present invention. A bonded structure can be realized.

Further, according to the heat sink having the thermally conductive bonding structure according to the present invention, the bonding portion between the heat absorbing body and the plate-like fin has excellent adhesion and thermal conductivity, and has excellent heat dissipation property. It is possible to alleviate the stress generated in the parts and prevent peeling. Furthermore, it is possible to stably and efficiently provide a high-quality heat sink that has high rigidity and assembly accuracy, and has the strength and precision as designed. In addition, with the thermally conductive bonding structure according to the present invention, the connecting body and the second plate-shaped fin are further bonded, and a similarly high-quality heat sink with better heat dissipation performance can be stably and efficiently provided.

Further, according to the semiconductor device having the thermally conductive bonding structure according to the present invention, the bonding portion between the base plate and the circuit board or between the circuit board and the semiconductor chip has excellent adhesion and thermal conductivity. At the same time, it is possible to alleviate the stress generated at the joint and prevent breakage and peeling. Therefore, efficient heat dissipation and stress relaxation can be achieved, and semiconductor devices can be expected to be made smaller and have a longer lifespan. Furthermore, it is possible to stably and efficiently provide high-quality semiconductor devices that have high rigidity and assembly accuracy, and have strength and precision as designed.

Further, a heat sink is provided on the lower surface side of the base plate on which the circuit board and the semiconductor chip are laminated, and between the two members of the base plate and the heat sink, in the case of the bonding layer, there is a gap between the base plate and the heat sink. The bonded portion has excellent adhesion and thermal conductivity, has excellent heat dissipation, and can alleviate stress generated at the bonded portion, thereby preventing the heat sink from peeling off. Furthermore, it is possible to stably and efficiently provide high-quality semiconductor devices that have high rigidity and assembly accuracy, and have strength and precision as designed.

FIG. 1 is a perspective view showing the concept of a thermally conductive joining structure of the present invention. FIG. 3 is a cross-sectional view showing the concept of the heat conductive bonding structure. FIG. 2 is an explanatory diagram showing the thermally conductive bonding method of the present invention. Explanatory drawing showing a modification of the thermally conductive bonding structure. FIG. 1 is a perspective view showing the concept of a thermally conductive joining structure of the present invention provided between two members. FIG. 3 is a cross-sectional view showing the concept of the heat conductive bonding structure. FIG. 2 is an explanatory diagram showing the thermally conductive joining method of the present invention for joining two members. FIG. 1 is a perspective view showing an example of a heat sink having a thermally conductive bonding structure according to the present invention. Also a cross-sectional view. An explanatory diagram showing the procedure for manufacturing the heat sink. FIG. 1 is a perspective view showing an example of a heat sink having a thermally conductive bonding structure of the present invention provided between two members. Also a cross-sectional view. An explanatory diagram showing the procedure for manufacturing the heat sink. FIG. 1 is a cross-sectional view showing an example of a semiconductor device having a thermally conductive bonding structure of the present invention provided between two members. Graph showing changes in thermal conductivity in the thickness direction and apparent stiffness in the in-plane direction

Next, embodiments of the present invention will be described in detail based on the accompanying drawings.

First, the thermally conductive bonding structure and thermally conductive bonding method of the present invention will be explained based on FIGS. 1a to 5. The thermally conductive bonding structure S1 according to the present invention, as shown in FIGS. 1a and 1b, is a structure consisting of a bonding layer 10 that closely adheres to a certain member 9 and conducts heat between the member 9.

As shown in FIGS. 1a, 1b, and 2, the bonding layer 10 includes a metal porous base plate 11 in which a plurality of through holes 111 extending in the thickness direction and opening on both the front and back surfaces are formed, and It is provided with a filling part 121 filled in the through hole 111 of the base plate 11, and a solidified solder body 12 consisting of

solder films

122 and 123 extending continuously from the filling part on at least one plate surface. Then, it is closely bonded to the facing member 9 by a solder film 122.

In such a thermally conductive joint structure S1 of the present invention, the porous base plate 11 is made of metal, has low thermal resistance, has excellent adhesion to the member 9, and has excellent thermal conductivity, and at the same time has through holes extending in the thickness direction. Since it is a plate material having a diameter of 111, it can be easily deformed in the horizontal direction and stress can be alleviated. Further, the filling portion 121 that is continuous with the solder film 122 and filled in each through hole 111 serves as an anchor to maintain strong integrity and adhesion between the solder film 122 and the porous base plate 11.

In addition, it has a solder film that tightly adheres to the component, but since the through hole filled with solder is surrounded by a metal plate, the thermal resistance along the plate thickness direction is small, and it has excellent adhesion and thermal conductivity to the component. has. There is also a wide contact area between the solder solidification body 12 and the porous base plate 11 through the filling part 121 filled in the through hole 111, and the heat received by the solder film 122 is efficiently transferred to the porous base plate 11. can do. Further, since the through holes 111 extend in the thickness direction, the porous base plate 11 maintains excellent rigidity in the thickness direction. Furthermore, since the solder filling portion 121 filled in each through hole 111 has a rod shape extending in the thickness direction as described above, the rigidity in the thickness direction, which is the axial direction, is further improved. Therefore, accuracy during assembly can be easily achieved. In other words, it is possible to realize a bonded structure with low thermal resistance and excellent thermal conductivity with the designed thickness, parallelism, and other precision.

In this example, another member may or may not be bonded to the side of the bonding layer 10 opposite to the member 9. As shown in the example of a heat sink described below, the porous base plate 11 constituting the bonding layer 10 has a remaining region extending outward from the region in addition to the region constituting the bonding layer 10, and the porous base plate 11 that constitutes the bonding layer 10 has a remaining region extending outward from the region, and has a remaining region extending outward from the region constituting the bonding layer 10. A heat sink that has another function (in the case of a heat sink described later, it has a function as a cooling fin for passing cooling fluid), or a second bonded area is provided through a non-bonded area as shown in Figure 3. It can be applied to a wide range of applications.

The porous base plate 11 can be made of a wide variety of metal materials with excellent thermal conductivity, such as aluminum, iron, and copper, and alloys thereof. In the case of copper, preferably, a perforated plate is used, which is obtained by cutting a lotus-shaped porous metal molded body formed by a metal coagulation method and having a plurality of pores extending in one direction in a direction perpendicular to the direction in which the pores extend. It will be done. However, the porous base plate of the present invention also includes those in which through holes are formed using a drill, laser, or the like. The lotus-shaped porous metal molded body can be formed by a known method such as a pressurized gas method (for example, the method disclosed in Japanese Patent No. 4235813) or a thermal decomposition method. . The through-holes of the porous plate cut out from the lotus-type porous metal molded body in this manner are the pores divided by the cutting process.

In addition to through holes, there are also holes with a bottom that do not penetrate through the hole (the hole is cut at a point where the pores are interrupted), but such a hole with a bottom also increases the contact area with the solder solidified body 12. In addition, in the case of a heat sink described below, the surface area is increased to promote heat dissipation from the plate surface. In this way, by using a porous plate cut out from a lotus-type porous metal molded body, the porous base plate 11 can be easily obtained at low cost. The porosity due to the through holes 111 of the porous base plate 11, that is, the ratio of the total volume inside the through holes 111 to the volume assuming that no holes exist in the porous base plate 11 is preferably 20 to 70% by volume. Further, the opening diameter (diameter) of the through hole 111 is preferably 0.01 to 1.00 mm.

The solder (solder alloy) of the solder solidified body 12 is determined depending on the usage environment, such as the temperature of the heat exchanged with the parts to be joined, the expected stress, etc., the material of the porous base plate 11, the size of the through hole, the plate thickness, etc. The material may be appropriately selected from known materials depending on the properties such as wettability required by the method. Particularly preferred are Sn--Ag based, Sn--Cu based, Sn--Bi based, Sn--In based solder alloys, or solder alloys based on these and containing a third element.

The filling portion 121 is solidified solder filled in the through hole 111 of the porous base plate 11, and is integrated with the

solder films

122 and 123. As will be described later, in order to melt the solder plate placed over the porous base plate 11 and to cause the solder to flow into the through holes 111 and solidify, the surface of the porous base plate 11 (including the inner walls of the through holes) is melted. It is also preferable to apply/evaporate a flux or other coating agent or metal film that increases solder wettability.

The

solder films

122 and 123 are solder films that extend over at least one plate surface continuously from the filling portion 121, and are films that improve adhesion and adhesion to the members to be joined. In this example, in addition to the solder film 122 on the side to be joined to the member 9, a solder film 123 is also formed on the opposite side, but the solder film 123 can be omitted. The solder film 122 and the member 9 are tightly adhered to each other and can perform heat transfer. Unlike conventional solder joints, the solder film 122 is relatively thin, and the solder film 122 does not reduce overall rigidity or accuracy. Further, the filling portion 121 formed continuously on the solder film 122 functions as an anchor, and can prevent separation from the porous base plate 11.

FIG. 2 shows a procedure for forming the thermally conductive bonding structure S1 of this example, that is, a thermally conductive bonding method in which a bonding layer 10 is provided in close contact with a member 9 and conducts heat between the member and the member 9. . First, the solder plate 120 and the porous base plate 11 are stacked on the member 9. Then, the solder plate 120 is melted by heating with a heating furnace or the like. As a result, the solder on the solder plate 120 rises through the through holes 111 of the porous base plate 11, oozes out to the upper surface side, forms a solder film 123, and solidifies.

The remaining solder that did not enter the through holes 111 forms a solder film 122 between the porous base plate 11 and the member 9 and solidifies. Furthermore, the solder solidified within the through hole 111 forms the filling portion 121 . In this way, the bonding layer 10 (thermal conductive bonding structure S1) closely bonded to the member 9 is formed. Peeling of the solder film 122 and the porous base plate 11 can be prevented by the anchor effect of the filling part 121, but as in this example, a solder film 123 that connects and integrates the filling parts 121 is provided at the end of the filling part 121. This structure further enhances the anchor effect.

In this example, the solder plate 120 was placed between the member 9 and the porous base plate 11 and heated, but it is also possible to place a solder plate on the upper surface side, that is, on the side where the solder film 123 is formed, and then heat it. is also preferable. This allows the solder film 123 to be formed more reliably. Further, in addition to the solder plate 120, it is also preferable to fill the through hole 111 with solder powder.

Next, an example of a thermally conductive bonding structure S2 consisting of a bonding layer provided between two members to bond the two members and transmit heat from one of the two members to the other will be explained based on FIGS. 4a, 4b, and 5. explain.

As shown in FIGS. 4a and 4b, the bonding layer 10A of the thermally conductive bonding structure S2 includes the porous base plate 11 interposed between the two

members

91 and 92, and the through-hole 111 of the porous base plate 11. A solidified solder body 12 consisting of a filling part 121 filled in the interior and

solder films

122 and 123 extending continuously from the filling part 121 onto both plate surfaces, and the

solder films

122 and 123 are two members facing each other. 91 and 92, respectively, in close contact with each other. The thermally conductive joint structure S2 of the present invention similarly has excellent adhesion and thermal conductivity to the

members

91 and 92, and since it is a plate material having through holes 111 extending in the thickness direction, It is easy to deform and can relieve stress. In particular, when joining two members, stress is likely to occur at the joint due to differences in thermal contraction between the two members, but the present invention absorbs this stress and prevents breakage and damage.

Strong integrity and adhesion are maintained between the

solder films

122 and 123 and the porous base plate 11 using the solder film as an anchor between the filling portion 121 and each other. Similarly, a bonded structure with low thermal resistance and excellent thermal conductivity can be realized with the thickness, parallelism, and other precision as designed. The material of the porous base plate 11, the porosity of the through-holes 111, the configuration such as the opening diameter, the material of the solder, and other forms can be considered in the same manner as in the above structure S1, and therefore their explanations will be omitted.

FIG. 5 shows the procedure for forming the thermally conductive bonded structure S2 of this example. A conduction bonding method is shown. First, the solder plate 120, the porous base plate 11, and the solder plate 120 are stacked in this order on one member 91, and then the other member 92 is stacked on top of that. Then, both solder plates 120 are melted by heating them by placing them in a heater 4 or a heating furnace. As a result, the solder of the solder plate 120 is filled into the through holes 111 of the porous base plate 11 from above and below, respectively, and

solder films

122 and 123 are formed that continue from the filled portions 121 and spread over both plate surfaces.

The amount of solder that melts from the solder plate 120 and flows into the through hole 111 increases as the solder on the upper side flows in due to gravity. It is preferable to make 120 thicker and use a larger amount of solder. In this example, the solder plates 120 are arranged on both the upper and lower sides of the porous base plate 11, but it is also possible, for example, to use only the upper solder plate and omit the lower side. Even if the lower side is omitted, the solder flowing downward from the through hole 111 can spread and form the lower solder film 122.

The other configurations and modifications are the same as the structures shown in FIGS. 1a to 3 above, and their explanations will be omitted.

Next, an example of a heat sink configured by the thermally conductive bonding structure S1 will be described based on FIGS. 6a, 6b, and 7.

The heat sink 2 of this example is an improved version of the heat sink described in Japanese Unexamined Patent Publication No. 2018-73869 (Japan), and by using the present thermally conductive bonding structure S1, it can be manufactured more efficiently and accurately, and from the heat absorber. It is constructed to have excellent heat conduction to the cooling fins and excellent bonding strength. Specifically, as shown in FIGS. 6a and 6b, it is made of metal and has a contact surface 20b that comes into contact with an object to be cooled such as a CPU, and the heat of the object to be cooled is transferred through the contact surface. It includes a heat absorbing body 20 and a metal plate-shaped fin 21 having a partial region R1 of the plate surface joined to a surface 20a of the heat absorbing body 20 opposite to the contact surface 20b. A plurality of through holes 111 are formed in the plate-like fin 21 and open to the plate surface.

Then, the bonding layer 10 of the heat absorbing body 20 and the plate-like fin 21 is formed in the partial region R1 of the plate-like fin 21, with the heat absorbing body 20 as the member 9 and the plate-like fin 21 as the porous base plate 11, The solidified solder body 12 is composed of the filled portion 121 filled in the through hole 111 of the region R1, and the

solder films

122 and 123 that extend over the plate surface continuously from the filled portion 121. . The solder film 122 is in close contact with the facing heat absorbing body 20 and efficiently conducts heat between it and the heat absorbing body 20 .

The remaining region R2 of the plate-shaped fin 21 that protrudes around the heat absorbing body 20 functions as a heat radiating fin that radiates heat to the fluid passing through the through hole 111. According to the heat sink 2 of this example, the above-mentioned effects of the thermally conductive bonding structure S1 are achieved, that is, superior adhesion is achieved compared to the conventional heat sink in which the plate end of the heat dissipation fin is bonded to the side wall of the heat absorber. It has thermal conductivity, can relieve stress, and has excellent bonding strength.

Furthermore, the filling portion 121 that is continuous with the solder film 122 and filled in each through hole 111 serves as an anchor to maintain strong integrity and adhesion between the solder film 122 and the plate-shaped fin 21. In addition, a bonded structure with low thermal resistance and excellent thermal conductivity can be easily realized with the thickness, parallelism, and other precision as designed. In this example, a solder film 123 is also formed on the surface of the plate-shaped fin 21 opposite to the heat absorbing body 20, but this film can be omitted.

As shown in FIG. 7, in this heat sink 2, a solder plate 120 having the same shape in plan view is placed on the upper surface of the heat absorbing body 20, and plate-shaped fins 21 are further stacked. The plate-shaped fin 21 is placed such that the center region R1 is placed on the solder plate 120, and the remaining region R2 is located around the center region R1. Then, by heating and melting the solder plate 120 by placing it in the heater 4 or a heating furnace, the solder of the solder plate 120 rises through the through hole 111 in the region R1 on the center side of the plate-shaped fin 21, and moves toward the upper surface side. The solder oozes out, forms a solder film 123, and solidifies.

The remaining solder that did not enter the through holes 111 forms a solder film 122 between the plate-like fins 21 and the heat absorbing body 20 and solidifies. Furthermore, the solder solidified within the through hole 111 forms a filling portion 121 . In this way, the bonding layer 10 (thermal conductive bonding structure S1) closely bonded to the heat absorbing body 20 is formed.

Although the heat absorbing body 20 has a solid cubic shape made of metal, it is not limited to such a configuration. It may be hollow instead of solid. A wide range of materials used for conventional heat sinks, such as aluminum, iron, and copper, can be used. Moreover, it can also be configured with a heat pipe built-in or the heat pipe itself.

As for the metal material constituting the plate-shaped fins 21, similarly to the heat absorbing body 20, materials used in plate-shaped fins of conventional heat sinks, such as aluminum, iron, and copper, can be widely used. In this example, a lotus-shaped porous metal molded body made of copper and having a plurality of pores extending in one direction, which was molded by a metal coagulation method, was cut in a direction that intersects the direction in which the pores extend. It is something. In addition to the through hole 111, there are also holes with a bottom that do not penetrate through the plate material cut out from the lotus-type porous metal molded body. This has the effect of increasing the surface area and promoting heat radiation from the plate surface. Although the shape of the plate-like fin 21 is rectangular, it is not limited to this at all, and of course it can be made into a shape other than a rectangle, such as a polygon or a circle.

Next, an example of a heat sink having a thermally conductive bonding structure S2 will be described based on FIGS. 8a, 8b, and 9.

The heat sink 2A of this example is an improved version of the heat sink also described in Japanese Patent Application Publication No. 2018-73869 (Japan), and by using the present heat conductive bonding structure S2, it can be manufactured more efficiently and accurately, and the heat absorber The structure has excellent heat conduction from the cooling fins to the cooling fins, and excellent bonding strength.

Specifically, as shown in FIGS. 8a and 8b, a metal heat absorber 20 has a contact surface 20b that contacts the object to be cooled, and the heat of the object to be cooled is transferred through the contact surface. and a first plate-like fin 21 made of metal with a partial region R3 of the plate surface joined to the surface 20a on the opposite side to the contact surface 20b of the heat absorbing body 20; A metal connecting body 22 joined to a region corresponding to the partial region R3 on the plate surface opposite to the plate surface, and a surface of the connecting body 22 opposite to the surface joined to the first plate-like fin 21. A second plate-shaped fin 21A made of metal is provided on the side surface thereof, to which a partial region R5 of the plate surface is joined.

The bonding layer 10A of the heat absorbing body 20, the plate-like fins 21, and the connecting body 22 uses the heat absorbing body 20 as one of the two members 91, and the first plate-like fin 21 as the porous base plate 11, The connecting body 22 is the other member 92 of the two members, and the filling portion 121 filled in the through hole 111 of the region R3 is provided in the partial region R3 of the plate-like fin 21, and the filling portion 121 The solidified solder body 12 is composed of the

solder films

122 and 123 that continuously spread over the upper and lower plate surfaces. The

solder films

122 and 123 are in close contact with the heat absorbing body 20 and the connecting body 22 facing each other, and conduct heat efficiently between the heat absorbing body 20 and the connecting body 22, respectively. The connecting body 22 and the second plate-like fin 21A are joined by a thermally conductive joining structure S1 made of the same joining layer 10 as in the example of the heat sink 2 described above.

The remaining region R4 of the first plate-like fin 21 that protrudes around the heat absorbing body 20 and the connecting body 22, and the remaining region R6 of the second plate-like fin 21A that protrudes around the connecting body 22 have through holes 111, respectively. It functions as a radiation fin that radiates heat to the fluid passing through it. According to the heat sink 2A of this example, the above-mentioned effects of the thermally conductive bonding structures S1 and S2 are superior to those of the conventional heat sink in which the plate ends of the heat dissipation fins are bonded to the side wall of the heat absorber. It has good adhesion and thermal conductivity, can relieve stress, and has excellent bonding strength.

In this example, there is only one connecting body 22, and two heat dissipating fins, the

plate fins

21 and 21A, are arranged in parallel in the axial direction perpendicular to the plate surface. It is also possible to provide a heat sink with two or more connecting bodies 22 arranged in series in the axial direction, and three or more radiation fins arranged in parallel. According to the heat conductive joint structures S1 and S2 of the present invention, a plurality of heat dissipating fins can be assembled in parallel with each other with high precision, and the heat absorbed by each fin can be efficiently transmitted, and the heat can be efficiently transmitted from each fin. It can dissipate heat well.

As shown in FIG. 9, the present heat sink 2 is constructed by placing a solder plate 120, a plate-like fin 21, a solder plate 120, a connecting body 22, a solder plate 120, and a plate-like fin 21A in this order on the upper surface side of a heat absorbing body 20. I'll keep it. The plate-shaped

fins

21 and 21A are placed so that the center regions R3 and R5 correspond to the positions of the solder plate 120, respectively, and the remaining regions R4 and R6 are located around the center regions R3 and R5, respectively. Then, by melting each solder plate 120 by heating with the heater 4, heating furnace, etc., the solder of each solder plate 120 is transferred to the through holes 111 of the center side regions R3 and R5 of the plate-shaped

fins

21 and 21A. At the same time,

solder films

122 and 123 are formed on both surfaces of each fin and solidified.

The solder solidified within the through hole 111 of each fin forms a filling portion 121, respectively. In this way, the bonding layer 10A in which the plate-like fins 21 are tightly bonded to the heat absorbing body 20 and the connecting body 22
(thermal conductive joint structure S2) and a joint extension 10 (in which the plate-like fins 21A are tightly joined to the connecting body 22) (
A thermally conductive bonding structure S1) is formed. Other structures, materials, modifications, etc. are the same as those of the heat sink 2 described above, so their explanations will be omitted.

Next, an example of a semiconductor device having a thermally conductive junction structure S2 will be described based on FIG. 10.

The semiconductor device 3 of this example includes a base plate 30, a circuit board 31 bonded onto the base plate 30, a semiconductor chip 32 bonded onto the circuit board 31, and a semiconductor chip 32 bonded onto the bottom surface of the base plate 30. It is provided with a heat sink 33 to be bonded, and between the base plate 30 and the circuit board 31, between the circuit board 31 and the semiconductor chip 32, and between the base plate 30 and the heat sink 33, from the bonding layer 10A to The present heat conductive bonding structure S2 is provided. Reference numeral 34 indicates a bonding wire, 35 a terminal, 36 a case, and 37 a filler.

In this manner, the semiconductor device 3 using the thermally conductive bonding structure S2 of the present invention has excellent adhesion and thermal conductivity in these bonded portions, and also relieves stress generated in the bonded portions and prevents breakage and peeling. Since it has excellent durability and prevents such occurrences, efficient heat dissipation and stress relaxation can be achieved, and equipment can be expected to be smaller and have a longer lifespan. Furthermore, since it has high rigidity and assembly accuracy, it is possible to stably and efficiently provide a high-quality device that has the strength and precision as designed. In this example, the thermally conductive bonding structure S2 is used for each bonding portion, but it may of course be adopted only for some bonding portions. Furthermore, it goes without saying that the structure of the semiconductor device is not limited to that shown in the drawings, and can be applied to various types of devices.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

S1, S2 Thermal

conductive bonding structure

2, 2A Heat sink 3 Semiconductor device 4 Heater 9

Member

10, 10A Bonding layer 11 Porous base plate 12 Solidified solder 20 Heat absorber 20a Surface

20b Contact surface

21, 21A Plate fin 22 Connecting body 30 Base plate 31 Circuit board 32 Semiconductor chip 33

Heat sink

91, 92 Member 111 Through hole 120 Solder plate 121 Filling

part

122, 123 Solder film R1-R6 area

Claims

A thermally conductive bonding structure consisting of a bonding layer that closely adheres to a certain member and conducts heat between the member,
The bonding layer is
a metal porous base plate having a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces;
A filling part filled in the through-hole of the porous base plate, and a solidified solder body consisting of a solder film that extends on at least one plate surface continuously from the filling part,
the solder film is closely bonded to the facing member;
Heat conductive joint structure.
A thermally conductive bonding structure comprising a bonding layer provided between two members to bond the two members and transmit heat from one of the two members to the other,
The bonding layer is
a metal porous base plate interposed between two members, in which a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces are formed;
A filling part filled in the through-hole of the porous base plate, and a solidified solder body consisting of a solder film that extends over both plate surfaces continuously from the filling part,
The solder film is closely bonded to two members facing each other,
Heat conductive joint structure.
The heat conductive bonding structure according to claim 1 or 2, wherein the porous base plate constituting the bonding layer has a porosity due to the through holes of 30 to 80 vol%.
A thermally conductive bonding method comprising providing a bonding layer that is in close contact with a certain member and conducts heat between the member,
As the bonding layer,
A metal porous base plate is provided with a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces,
A solidified solder body is provided by filling the through holes of the porous base plate with a solder material and solidifying the solder material in a state where a solder film is formed continuously in the filled portion and spread over at least one plate surface,
the solder film is closely bonded to the facing member;
Thermal conduction bonding method.
A thermally conductive joining method for joining two members by providing a joining layer between the two members that transmits heat from one of the two members to the other,
As the bonding layer,
A metal porous base plate having a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces is interposed between the two members, and
Filling the through-holes of the porous base plate with a solder material, and providing a solidified solder body that is solidified to form a solder film that extends continuously over both plate surfaces in the filled portion,
The solder film is closely bonded to two members facing each other,
Thermal conduction bonding method.
interposing the solder material between one or both of the front and back surfaces of the porous base plate and the member facing thereto,
The member, the porous base plate, and the solder material are heated in a stacked state to melt the solder material and fill the through hole of the porous base plate with the solder material, and the solder material is continuous with the filled part. The solidified solder is formed by cooling and solidifying the solder film that spreads over both plate surfaces.
The thermally conductive bonding method according to claim 4 or 5.
The two members, the porous base plate, and the solder material are stacked vertically, and the solder material is placed on the upper surface side of the porous base plate, and the heating is performed to melt the solder material,
Due to the solder material's own weight and the load from the upper member, the solder material sinks into the through hole and fills it,
leaking from the lower opening of the through hole and spreading into the gap between the porous base plate and the lower member, forming the solder film on the lower plate surface;
The remaining solder material that did not fall into the through hole forms the solder film on the upper plate surface.
The thermally conductive bonding method according to claim 6.
A heat sink having the thermally conductive bonding structure according to claim 1,
A metal heat absorber as the certain member, which has a contact surface that comes into contact with the object to be cooled, and the heat of the object to be cooled is transferred through the contact surface;
a metal plate-shaped fin serving as the porous base plate, a part of the plate surface being joined to a surface opposite to the contact surface of the heat absorbing body;
A plurality of through holes opening to the plate surface are formed in the plate-like fin,
The filling part filled in a through hole formed in the partial area of the plate-like fin, and the solder film extending over the plate surface continuously from the filling part. The bonding layer is formed, which has a solidified solder, is in close contact with the heat absorbing body facing the solder film, and conducts heat between the solder film and the heat absorbing body,
radiating heat to the outside through a through hole in a remaining region protruding around the heat absorbing body of the plate-like fin;
heat sink.
A heat sink having the thermally conductive bonding structure according to claim 2,
a metal heat absorber as one of the two members, which has a contact surface that comes into contact with the object to be cooled, and through which the heat of the object to be cooled is transferred;
a metal first plate-shaped fin serving as the porous base plate, a part of the plate surface of which is joined to a surface opposite to the contact surface of the heat absorbing body;
a metal connector as the other member of the two members, which is joined to a region corresponding to the partial region of the plate surface opposite to the plate surface of the first plate-shaped fin;
A second plate-shaped fin made of metal to which a partial region of the plate-shaped fin is bonded is provided on a surface of the connecting body opposite to the surface bonded to the first plate-shaped fin,
A plurality of through holes each opening to the plate surface are formed in the first plate-like fin and the second plate-like fin,
The filling portion is filled in a through hole formed in the partial region of the first plate-like fin, and the solder film extends over both plate surfaces continuously from the filling portion. The bonding layer is formed, having the solidified solder body consisting of the solder film, in which the solder film is in close contact with the facing heat absorbing body and the connecting body, respectively, and transmitting heat from the heat absorbing body to the connecting body,
Through a through-hole in a remaining region of the first plate-like fin that protrudes around the heat absorbing body and the connecting body, and a through-hole in a remaining region that protrudes around the connecting body of the second plate-like fin, dissipates heat to the outside,
heat sink.
base plate and
a circuit board bonded onto the base plate;
a semiconductor chip bonded onto the circuit board;
The thermally conductive bonding structure according to claim 2, wherein the bonding layer is provided between at least one of the two members of the base plate and the circuit board and the two members of the circuit board and the semiconductor chip. A semiconductor device.
A heat sink is provided on the bottom side of the base plate on which the circuit board and semiconductor chips are stacked,
3. A semiconductor device having a thermally conductive bonding structure according to claim 2, comprising the bonding layer between two members, the base plate and the heat sink.