Thermally conductive joining structure, thermally conductive joining method, heat sheet having the thermally conductive joining

Abstract

[Problem] To provide a thermally conductive bonding technique which is suitable for a bonding structure of a semiconductor device, can alleviate stress caused by thermal strain, can prevent breakage and peeling of a bonding portion, has low thermal resistance, can improve heat dissipation properties by thermal conduction between members, can maintain rigidity in the stacking direction between the members, and can improve the reliability of the bonding structure. According to the present invention, durability as a device can be maintained, the degree of parallelism between members can be maintained during joining assembly, and assembly accuracy can be improved. [Solution] The present invention is a structure comprising a bonding layer (10) that is in close contact with a member (9) and performs heat conduction with the member (9), and is provided with: a metal porous substrate (11) in which are formed a plurality of through-holes (111) that extend in the thickness direction and open on both front and back plate surfaces; and a solder solidified body (12) composed of a filling part (121) filled in the through hole (111) of the porous substrate (11) and solder films (122, 123) continuously expanded to at least one plate surface with the filling part, wherein the solder film (122) is closely adhered to and bonded to an opposing member (9).

Description

Technical Field

[0001] The present invention relates to a bonding structure between a heat receiving body and a heat dissipating fin of a heat sink, and a heat conductive bonding structure and a heat conductive bonding method suitable for bonding structures of various parts of a semiconductor device. Background Art

[0002] In recent years, semiconductor devices, especially power semiconductor devices, have increased the heat generated by semiconductor chips as the current density increases. In addition, semiconductor devices are expected to be miniaturized, and it is more important to efficiently transfer the heat of semiconductor chips with high heat generation to the heat sink as a cooler and further dissipate the heat from the heat sink to the gas or liquid refrigerant. A representative semiconductor device, for example, stacks a circuit board and a semiconductor chip on a substrate, and mounts a heat sink on the lower surface of the substrate. A heat conductive sheet is provided between the stacked components to maintain good thermal conductivity and connect the two (for example, refer to Patent Document 1).

[0003] However, the semiconductor device has a structure in which multiple components (semiconductor chips, circuit boards, substrates, etc.) with different linear expansion coefficients are joined and stacked. Therefore, the large temperature changes associated with the above-mentioned heat generation will cause thermal strains in various parts of the semiconductor device, especially the breakage and peeling of the heat-conducting sheet as the joint portion. In order to prevent the breakage of the joint portion caused by such thermal strain, it is also considered to replace the heat-conducting sheet with a solder layer with low rigidity and capable of relieving stress. However, the thermal resistance of the solder is relatively large, and the heat dissipation obtained by heat conduction between the components becomes poor. In addition, the rigidity cannot be maintained in the stacking direction between the components, that is, in the direction of the plate thickness orthogonal to the joint surface, which limits the durability of the device. Moreover, it is difficult to maintain the parallelism between the components during joint assembly, and there are also problems with the assembly accuracy.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent Application Laid-Open No. 11-58591 (Japan). Summary of the invention

[0007] Problems to be solved by the invention

[0008] Therefore, the present invention is completed in view of the above-mentioned situation, and the problem to be solved is to provide a bonding structure suitable for semiconductor devices and capable of alleviating stress caused by thermal strain, preventing breakage and peeling of the bonding portion, and having low thermal resistance, and capable of improving the heat dissipation obtained by heat conduction between components. It is a thermal conductive bonding technology that can be expected to be miniaturized and have a long life, and further, it is a thermal conductive bonding technology that can maintain rigidity in the stacking direction between components, maintain durability, and maintain parallelism between components during bonding and assembly, and has high assembly accuracy.

[0009] Technical solutions to the problem

[0010] In view of this situation, the inventors of the present invention conducted in-depth research and found that by combining a metal plate having multiple through holes extending in the thickness direction with solder, it is possible to relieve stress in a horizontal direction parallel to the surface, prevent breakage and peeling, reduce thermal resistance in the thickness direction (plate thickness direction), have excellent thermal conductivity, maintain rigidity in the thickness direction, and obtain a joining structure with assembly accuracy. Moreover, such a thermally conductive joining structure is also effective beyond semiconductor devices. It was further discovered that this effect can be applied to the joining structure of a heat receiving body and a heat dissipation fin of a new heat sink, thereby completing the present invention.

[0011] In addition, the thermal conductivity in the thickness direction and the approximate rigidity in the in-plane direction were investigated when the volume ratio of the metal plate (copper plate) to the solder was changed under the test conditions shown below. Fig.11 . As can be seen from the graph, the larger the volume of the metal plate (the volume of the wall part excluding the holes) (the smaller the porosity), the more proportionally the thermal conductivity increases, and the approximate rigidity in the in-plane direction increases rapidly. It can be seen that in order to satisfy both thermal conductivity and stress relaxation, the volume of the metal plate is preferably set to a range of 70 vol% or less (porosity of 30 vol% or more), and the volume of the metal plate is more preferably set to a range of 20 vol% or more and 70 vol% or less (porosity of 30 vol% or more and 80 vol% or less).

[0012] (Test conditions)

[0013] Thickness of bonding layer: 200 μm

[0014] Solder: SAC305 (Sn-3mass%Ag-0.5mass%Cu)

[0015] Thermal conductivity measuring device: TCM1001 (manufactured by RHESCA Corporation)

[0016] That is, the present invention includes the following technical solutions.

[0017] (1) A heat-conducting bonding structure composed of a bonding layer, wherein the bonding layer is in close contact with a component and conducts heat between the component, wherein the bonding layer includes: a porous substrate made of metal, which is formed with a plurality of through holes extending in the thickness direction and opening on both the front and back board surfaces; and a solder solidified body, which is composed of a filling portion filled in the through holes of the porous substrate and a solder film extending continuously from the filling portion to at least one board surface, wherein the solder film is in close contact with and bonded to the relative component.

[0018] (2) A thermally conductive bonding structure composed of a bonding layer, wherein the bonding layer is arranged between two components and bonds the two components together, and transfers heat from one component to the other component of the two components, wherein the bonding layer includes: a porous substrate made of metal, which is formed with a plurality of through holes extending in the thickness direction and opening on both front and back board surfaces, and is installed between the two components; and a solder solidified body, which is composed of a filling portion filled in the through holes of the porous substrate and a solder film extending continuously from the filling portion to the two board surfaces, wherein the solder film is tightly attached to and bonded to the two opposite components respectively.

[0019] (3) In the thermally conductive bonding structure described in (1) or (2), the porous substrate constituting the bonding layer has a porosity of 30 to 80 vol % due to the through holes.

[0020] (4) A method for thermally conductive bonding by providing a bonding layer, wherein the bonding layer is in close contact with a component and conducts heat between the component, wherein a porous substrate made of metal having a plurality of through holes extending in the thickness direction and opening on both front and back board surfaces is provided as the bonding layer, and a solder solid body is provided. The solder solid body is obtained by solidifying a solder member in a state where the solder is filled in the through holes of the porous substrate and a solder film is formed which extends continuously from the filled portion to at least one board surface, and the solder film is in close contact with the relative components and bonded together.

[0021] (5) A thermally conductive bonding method, wherein a bonding layer is provided between two components to transfer heat from one component to the other component, thereby bonding the two components together, wherein a porous substrate made of metal having a plurality of through holes extending in the thickness direction and opening on both front and back board surfaces is installed between the two components as the bonding layer, and a solder solid body is provided, wherein the solder solid body is solidified in a state where the solder member is filled in the through holes of the porous substrate and a solder film is formed which extends continuously from the filled portion to the two board surfaces, wherein the solder film is tightly attached to the two opposite components and bonded together.

[0022] (6) In the thermal conductive bonding method described in (4) or (5), the solder part is installed between one or both of the front and back plate surfaces of the porous substrate and the component opposite to the plate surface, the component, the porous substrate and the solder part are heated in an overlapping state to melt the solder part, and the solder part is cooled and solidified in a state in which it fills the through holes of the porous substrate and forms a solder film that extends continuously with the filling portion to the two plate surfaces, thereby forming the solder solidified body.

[0023] (7) In the thermal conductive bonding method described in (6), the two components, the porous substrate and the solder component are overlapped in the vertical direction and the solder component is arranged on the upper surface side of the porous substrate. The heating is performed to melt the solder component, and the solder component is made to fall into and fill the through hole by utilizing its own weight and the load from the component on the upper side. The solder component leaks out from the opening on the lower side of the through hole and expands to the gap between the porous substrate and the component on the lower side, forming the solder film on the lower board surface. The remaining part of the solder that has not fallen into the through hole forms the solder film on the upper board surface.

[0024] (8) A heat sink having the thermal conductive joint structure described in (1), comprising: a metal heat absorber as the certain component, the metal heat absorber having a contact surface abutting against an object to be cooled, and heat of the object to be cooled is transferred through the contact surface; and a metal plate-shaped fin as the porous substrate, a portion of a plate surface of which is joined to a surface of the heat absorber on the opposite side of the contact surface, a plurality of through holes opened in the plate surface are formed in the plate-shaped fin, the joining layer is formed in the portion of the plate-shaped fin, the joining layer having the solder solidified body composed of the filling portion filled in the through holes formed in the region and the solder film extending continuously from the filling portion to the plate surface, the solder film being in close contact with the opposing heat absorber, conducting heat with the heat absorber, and dissipating heat to the outside through the through holes in the remaining region of the plate-shaped fin protruding around the heat absorber.

[0025] (9) A heat sink having the thermally conductive joint structure described in (2), comprising: a metal heat absorber as one of the two components, the metal heat absorber having a contact surface that contacts an object to be cooled and transfers heat from the object to be cooled through the contact surface; a metal first plate-shaped fin as the porous substrate, a portion of its plate surface being joined to a surface of the heat absorber on the opposite side of the contact surface; a metal connecting body as the other of the two components, the metal connecting body being joined to an area of ​​the plate surface of the first plate-shaped fin on the opposite side of the plate surface that corresponds to the portion of the plate surface; and a metal second plate-shaped fin, a portion of its plate surface being joined to the connecting body and to the portion of the plate surface of the connecting body that is joined to the first plate-shaped fin. On the surface opposite to the surface, a plurality of through holes opening in the plate surface are respectively formed on the first plate-shaped fin and the second plate-shaped fin, and the bonding layer is formed on the said partial area of ​​the first plate-shaped fin, and the bonding layer has the said solder solid body composed of the said filling part filled in the through holes formed in the area and the said solder film extending continuously with the said filling part to the two plate surfaces, and the said solder film is closely attached to the said opposite heat absorber and the said connecting body, respectively, and heat is transferred from the said heat absorber to the connecting body, and the heat is dissipated to the outside through the through holes of the first plate-shaped fin protruding to the remaining area around the said heat absorber and the said connecting body and the through holes of the second plate-shaped fin protruding to the remaining area around the said connecting body.

[0026] (10) A semiconductor device comprising: a substrate; a circuit board bonded to the substrate; and a semiconductor chip bonded to the circuit board, wherein the thermally conductive bonding structure described in (2) formed by the bonding layer is provided between at least two of the two components of the substrate and the circuit board and between the two components of the circuit board and the semiconductor chip.

[0027] (11) A semiconductor device, wherein a heat sink is provided on the lower surface side of a substrate on which a circuit board and a semiconductor chip are stacked, and the thermally conductive bonding structure described in (2) composed of the bonding layer is provided between the substrate and the heat sink.

[0028] Effects of the Invention

[0029] According to the thermally conductive bonding structure / thermal conductive bonding method of the present invention, the porous substrate made of metal with solder filled in the through-holes can easily expand and contract in the horizontal direction parallel to the bonding surface, and can relieve stress. Moreover, since the filling portion formed continuously with the solder film exerts an anchoring effect, it can prevent damage and peeling. That is, the porous substrate with multiple through-holes in the plate thickness direction can be deformed in the horizontal direction to relieve stress, and since the filling portion of the solder filled in each through-hole is rod-shaped in the plate thickness direction, it is easy to bend in the horizontal direction, further promoting the relaxation of stress in this direction. The filling portion filled in each through-hole continuously with the solder film acts as an anchor to maintain the firm integrity and close contact between the solder film and the porous substrate.

[0030] In addition, although the solder film is closely attached to the components, the through-holes filled with solder are surrounded by metal plates, so the thermal resistance along the plate thickness direction is small, and the components have excellent close contact and thermal conductivity. Since the through-holes are filled with solder, the increase in thermal resistance caused by the presence of voids can be avoided, and the solder solid body and the porous substrate have a larger contact area through the filling portion filled in the through-holes, and the heat received by the solder film can be efficiently transferred to the porous substrate.

[0031] Furthermore, since each through hole of the porous substrate extends in the thickness direction, it has excellent rigidity in the plate thickness direction orthogonal to the joint surface. Moreover, the filling portion of the solder filled in each through hole is in the shape of a rod extending in the plate thickness direction as described above, thereby further improving the rigidity in the plate thickness direction as the axial direction. Therefore, it is also possible to easily obtain the accuracy during assembly. That is, it is possible to achieve a low thermal resistance and excellent thermal conductivity joint structure with the accuracy of the designed thickness, parallelism, etc.

[0032] In addition, the porosity obtained by the through-holes of the porous substrate constituting the bonding layer is preferably 30 to 80 vol%. If the above-mentioned porosity is less than 30%, the stress relaxation effect tends to decrease. In addition, when greater than 80%, the longitudinal rigidity decreases, and it is easy to deform as a whole, and it is difficult to maintain the precision of the bonding portion such as thickness.

[0033] In addition, a solder part is installed between one or two plate surfaces on the front and back of the porous substrate and the component opposite thereto, the component, the porous substrate and the solder part are heated in an overlapping state to melt the solder part, and the solder part is cooled and solidified in a state where it fills the through holes of the porous substrate and forms a solder film that extends continuously with the filled portion to the two plate surfaces, thereby forming a solder solidified body. By adopting such a method, the thermal conductive bonding structure of the present invention with high precision can be efficiently realized.

[0034] When arranged between two components, the two components, the porous substrate and the solder part are overlapped in the up and down directions and the solder part is arranged on the upper surface side of the above-mentioned porous substrate, and then heated to melt the solder part. The solder part is made to fall into and fill the through-hole by utilizing its own weight and the load from the component on the upper side, and leak out from the opening on the lower side of the through-hole and expand to the gap between the porous substrate and the component on the lower side to form the above-mentioned solder film on the lower board surface. The remaining part of the solder part that has not fallen into the above-mentioned through-hole forms the above-mentioned solder film on the upper board surface. By adopting such a method, the thermal conductive bonding structure of the present invention with high precision can be efficiently realized.

[0035] Furthermore, according to the above-mentioned heat sink having the heat conductive joint structure of the present invention, the joint portion between the heat absorber and the plate-shaped fin has excellent adhesion and thermal conductivity, has excellent heat dissipation, can alleviate the stress generated in the joint portion, and can prevent peeling. In addition, it is possible to stably and efficiently provide a high-quality heat sink having high rigidity and assembly accuracy and having strength and accuracy that conform to the design. In addition, through the heat conductive joint structure of the present invention, it is possible to further join the connecting body and the second plate-shaped fin together, and it is possible to more stably and efficiently provide a high-quality heat sink having excellent heat dissipation.

[0036] In addition, according to the semiconductor device having the heat-conducting joint structure of the present invention, the joint between the substrate and the circuit board or between the circuit board and the semiconductor chip has excellent adhesion and thermal conductivity, and can relieve the stress generated in the joint, and can prevent cracking and peeling. As a result, efficient heat dissipation and stress relief can be achieved, and miniaturization and long life of the semiconductor device can be expected. Moreover, it is possible to stably and efficiently provide a high-quality semiconductor device with high rigidity and assembly accuracy and strength and accuracy that conforms to the design.

[0037] In addition, a heat sink is provided on the lower surface side of the substrate on which the circuit board and the semiconductor chip are stacked, and a structure composed of the above-mentioned bonding layer is provided between the two components of the substrate and the heat sink, so that the bonding portion between the substrate and the heat sink has excellent adhesion and thermal conductivity, has excellent heat dissipation, can alleviate the stress generated in the bonding portion, and can prevent the heat sink from peeling off. Moreover, a high-quality semiconductor device with high rigidity and assembly accuracy and strength and accuracy that conform to the design can be stably and efficiently provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1a It is a perspective view showing the concept of the thermal conductive joint structure of the present invention.

[0039] Figure 1b It is a cross-sectional view which similarly shows the concept of a thermally conductive bonding structure.

[0040] Figure 2 It is an explanatory diagram showing the thermal conductive bonding method of the present invention.

[0041] Figure 3 It is an explanatory diagram showing a modified example of the thermal conductive bonding structure in the same manner.

[0042] Figure 4a This is a perspective view showing the concept of the thermally conductive joining structure of the present invention provided between two members.

[0043] Figure 4b It is a cross-sectional view which similarly shows the concept of a thermally conductive bonding structure.

[0044] Figure 5 It is an explanatory diagram showing the thermal conductive bonding method of the present invention for bonding two members.

[0045] Figure 6a It is a perspective view showing an example of a heat sink having the thermally conductive bonding structure of the present invention.

[0046] Figure 6b It is the same cross-sectional view.

[0047] Figure 7 The figures are explanatory diagrams showing the steps of manufacturing the heat sink in the same manner.

[0048] Figure 8a This is a perspective view showing an example of a heat sink having the thermally conductive bonding structure of the present invention provided between two members.

[0049] Figure 8b It is the same cross-sectional view.

[0050] Fig. 9 The figures are explanatory diagrams showing the steps of manufacturing the heat sink in the same manner.

[0051] Fig.10 1 is a cross-sectional view showing an example of a semiconductor device having the thermally conductive bonding structure of the present invention provided between two members.

[0052] Fig.11 This is a graph showing changes in thermal conductivity in the thickness direction and rough rigidity in the in-plane direction. DETAILED DESCRIPTION

[0053] Next, embodiments of the present invention will be described in detail based on the drawings.

[0054] First, based on Figure 1a to Figure 5 , the heat conductive bonding structure and the heat conductive bonding method of the present invention are described. The heat conductive bonding structure S1 of the present invention is as follows Figure 1a , Figure 1b As shown, the structure is composed of a bonding layer 10 which is in close contact with a certain component 9 and conducts heat with the component 9 .

[0055] The bonding layer 10 is as follows Figure 1a , Figure 1b and Figure 2 As shown, it comprises: a porous metal substrate 11, which is formed with a plurality of through holes 111 extending in the thickness direction and opening on both the front and back sides of the plate; and a solder solidified body 12, which is composed of a filling portion 121 filled in the through holes 111 of the porous substrate 11 and solder films 122 and 123 extending continuously from the filling portion to at least one plate surface. Furthermore, through the solder film 122, it is closely attached to and joined to the above-mentioned component 9 opposite to it.

[0056] In such a thermally conductive joint structure S1 of the present invention, the porous substrate 11 is made of metal, has low thermal resistance, has excellent adhesion and thermal conductivity to the component 9, and is a plate having through holes 111 extending in the thickness direction, so it is easy to deform in the horizontal direction and can relieve stress. In addition, the filling portion 121 continuously filled in each through hole 111 with the solder film 122 acts as an anchor to maintain the strong integrity and adhesion between the solder film 122 and the porous substrate 11.

[0057] In addition, although including the solder film that is closely attached to the parts, since the through holes filled with solder are surrounded by metal plates, the thermal resistance along the thickness direction is small, and the parts have excellent close contact and thermal conductivity. The solder solid body 12 and the porous substrate 11 also have a larger contact area through the filling portion 121 filled in the through hole 111, and the heat received by the solder film 122 can be efficiently transferred to the porous substrate 11. In addition, because the through hole 111 extends in the thickness direction, the porous substrate 11 has excellent rigidity in the thickness direction. Moreover, the filling portion 121 of the solder filled in each through hole 111 is a rod-shaped extending in the thickness direction as described above, so the rigidity in the thickness direction as the axial direction is further improved. Therefore, it is also possible to easily obtain the accuracy during assembly. That is, it is possible to achieve a low thermal resistance and excellent thermal conductivity joint structure with the accuracy of the designed thickness, parallelism, etc.

[0058] In this example, other components may or may not be bonded to the bonding layer 10 on the side opposite to the component 9. As shown in the example of the heat sink described later, the porous substrate 11 constituting the bonding layer 10 has a remaining area extending outward from the area constituting the bonding layer 10, and components having other functions other than bonding can be widely used in the area (in the case of the heat sink described later, it has a function as a cooling fin through which a cooling fluid passes), and as Figure 3 As shown, components of the second joining region are provided via the non-joining region.

[0059] The porous substrate 11 can widely use metal materials and alloys thereof with excellent thermal conductivity such as aluminum, iron, and copper. In the case of copper, etc., it is preferred to use a lotus-shaped porous metal formed body with a plurality of pores extending in one direction formed by a metal solidification method, and a porous plate obtained by cutting in a direction orthogonal to the extending direction of the pores. However, in the porous substrate of the present invention, of course, a porous substrate in which through holes are set by a drill, a laser, etc. is included. The lotus-shaped porous metal formed body can be formed by a known method such as a high-pressure gas method (Pressurized Gas Method) (for example, a method disclosed in Japanese Patent Gazette No. 4235813), a thermal decomposition method (Thermal Decomposition Method), etc. The through holes of the porous plate obtained by cutting the lotus-shaped porous metal formed body are the above-mentioned pores disconnected by the above-mentioned cutting process.

[0060] In addition to the through holes, there are also non-through bottomed holes (the holes cut off at the interrupted position of the pores). Such bottomed holes also have the effect of increasing the contact area with the solder solid body 12. In addition, in the case of the heat sink described later, it also has the effect of increasing the surface area and promoting the heat dissipation from the plate surface. In this way, by using a porous plate cut from a lotus-shaped porous metal molded body, the porous substrate 11 can be obtained at low cost and easily. The porosity of the porous substrate 11 obtained by the through holes 111, that is, the ratio of the total volume inside the through holes 111 to the volume assuming that there are no holes in the porous substrate 11, is preferably 20 to 70% by volume. In addition, the opening diameter (diameter) of the through hole 111 is preferably 0.01 to 1.00 mm.

[0061] The solder (solder alloy) of the solder solid body 12 can be appropriately selected from known solders (solder alloys) according to the use environment, such as the temperature of heat exchanged with the parts of the bonding object, the assumed stress, etc., and the characteristics such as wettability obtained by the raw material, size of the through hole, and thickness of the porous substrate 11. In particular, Sn-Ag, Sn-Cu, Sn-Bi, Sn-In, or solder alloys containing a third element based on these are preferred.

[0062] The filling portion 121 is obtained by solidifying the solder filled in the through hole 111 of the porous substrate 11, and is formed integrally with the solder films 122 and 123. As described later, in order to melt the solder plate overlapped with the porous substrate 11, the solder itself flows into the through hole 111 and solidifies, and it is also preferred to apply / evaporate a coating agent such as a flux that improves the wettability of the solder, a metal film, etc. on the surface of the porous substrate 11 (including the inner wall of the through hole).

[0063] The solder films 122 and 123 are films of solder that extend continuously to at least one plate surface with the above-mentioned filling portion 121, and are films that improve the close contact and adhesion with the parts of the joining object. In this example, in addition to the solder film 122 on the side joined to the component 9, a solder film 123 is also formed on the surface on the opposite side, but the solder film 123 can also be omitted. The solder film 122 is firmly attached to the component 9 and heat transfer can be performed. Unlike the existing solder joint, the solder film 122 is relatively thin, and the overall rigidity and precision will not be reduced due to the solder film 122. In addition, the above-mentioned filling portion 121 formed continuously with the solder film 122 acts as an anchor and can also prevent peeling from the porous substrate 11.

[0064] Figure 2 1 shows the process of forming the thermally conductive bonding structure S1 of this example, that is, the thermally conductive bonding method of providing the bonding layer 10 which is in close contact with the component 9 and conducts heat with the component. First, the solder plate 120 and the porous substrate 11 are stacked on the component 9. Then, the solder plate 120 is melted by heating using a heating furnace or the like. As a result, the solder of the solder plate 120 rises through the through hole 111 of the porous substrate 11, seeps out to the upper surface side to form a solder film 123 and solidifies.

[0065] The remaining solder that has not entered the through hole 111 forms a solder film 122 between the porous substrate 11 and the component 9 and solidifies. In addition, the solder solidified in the through hole 111 forms the above-mentioned filling portion 121. In this way, a bonding layer 10 (thermal conductive bonding structure S1) that is closely bonded to the component 9 is formed. The peeling of the solder film 122 and the porous substrate 11 can be prevented by utilizing the anchoring effect of the filling portion 121. By forming a solder film 123 that connects and integrates the filling portions 121 to each other at the end of the filling portion 121 as in this example, the anchoring effect can be further improved.

[0066] In this example, the solder plate 120 is placed between the component 9 and the porous substrate 11 and heated, but it is also preferable to further place a solder plate on the upper surface side, that is, the side where the solder film 123 is formed, and heat it. This can more reliably form the solder film 123. In addition, it is also preferable not only to place the solder plate 120 but also to fill the through hole 111 with solder powder.

[0067] Next, based on Figure 4a , Figure 4b and Figure 5 , an example of a thermally conductive bonding structure S2 composed of a bonding layer that is provided between two components to bond the two components and transfer heat from one of the two components to the other is described.

[0068] like Figure 4a and Figure 4bAs shown, the bonding layer 10A of the present heat-conducting bonding structure S2 includes: the above-mentioned porous substrate 11 installed between the two components 91 and 92; and a solder solidified body 12, which is composed of a filling portion 121 filled in the through hole 111 of the porous substrate 11 and solder films 122 and 123 extending continuously with the filling portion 121 to the two board surfaces, and the solder films 122 and 123 are structures that are respectively tightly attached to and bonded to the two opposite components 91 and 92. In such a heat-conducting bonding structure S2 of the present invention, it also has excellent tightness and thermal conductivity for the components 91 and 92. At the same time, since it is a plate material with a through hole 111 extending in the thickness direction, it is easy to deform in the horizontal direction and can relieve stress. In particular, the bonding of two components is prone to generate stress at the bonding portion due to the difference in thermal shrinkage of the two components, but the present invention can absorb this stress and prevent cracking and breakage.

[0069] The solder films 122 and 123 are anchored to the porous substrate 11 by the filling portion 121 and the mutual solder films to maintain a strong integrity and close contact. In addition, similarly, a low thermal resistance and excellent thermal conductivity joint structure can be achieved with the precision of the designed thickness, parallelism, etc. The raw material of the porous substrate 11, the porosity of the through hole 111, the structure of the opening diameter, the raw material of the solder, and other methods can be considered in the same way as the above-mentioned structure S1, and their description is omitted.

[0070] Figure 5 The process of forming the heat-conducting joint structure S2 of this example is shown, that is, a heat-conducting joint method in which a joint layer 10 for transferring heat from one of the two components 91 and 92 to the other is provided between two components 91 and 92. First, on one component 91, a solder plate 120, a porous substrate 11, and a solder plate 120 are stacked in sequence, and another component 92 is further stacked thereon. Then, the two solder plates 120 are melted by heating by the heater 4, placing in a heating furnace, etc. As a result, the solder of the solder plate 120 is respectively filled into the through hole 111 of the porous substrate 11 from the top and bottom, and the solder film 122 and 123 are continuously extended to the two plate surfaces with the filling portion 121.

[0071] The amount of solder that melts the solder plate 120 and flows into the through hole 111 is greater when the solder flows into the upper side due to gravity. Therefore, in order to make the thickness of the solder films 122 and 123 equal, it is preferred that the solder plate 120 on the upper side is thicker and the amount of solder is greater. In this example, the solder plates 120 are arranged on the upper and lower sides of the porous substrate 11. For example, only the upper solder plate can be arranged and the lower side can be omitted. Even if the lower side is omitted, the solder flowing downward from the through hole 111 will expand and form the solder film 122 on the lower side.

[0072] Regarding other structures, modifications and the above Figure 1a to Figure 3The structure is the same, so its description is omitted.

[0073] Next, based on Figure 6a , Figure 6b and Figure 7 An example of a heat sink formed of the thermally conductive bonding structure S1 will be described.

[0074] The heat sink 2 of this example is equivalent to an improved version of the heat sink described in Japanese Patent Gazette No. 2018-73869, and is a heat sink having a structure with excellent heat conduction from the heat absorber to the cooling fins and excellent bonding strength, which can be manufactured more efficiently and accurately by using the present thermal conductive bonding structure S1. Specifically, Figure 6a , Figure 6b As shown, the heat absorbing body 20 made of metal has a contact surface 20b which contacts with a cooling object such as a CPU and transfers heat from the cooling object through the contact surface; and a metal plate-shaped fin 21, a portion of a plate surface area R1 of which is joined to a surface 20a on the opposite side of the contact surface 20b of the heat absorbing body 20. The plate-shaped fin 21 is formed with a plurality of through holes 111 opening in the plate surface.

[0075] Furthermore, the bonding layer 10 of the heat absorber 20 and the plate-like fin 21 is composed of the heat absorber 20 as the component 9 and the plate-like fin 21 as the porous substrate 11, and the solder solidified body 12 composed of the filling portion 121 filled in the through hole 111 in the region R1 and the solder films 122 and 123 extending continuously from the filling portion 121 to the plate surface. The solder film 122 is in close contact with the heat absorber 20 facing the heat absorber 20, and conducts heat efficiently to the heat absorber 20.

[0076] The remaining area R2 of the plate-shaped fin 21 protruding around the heat absorber 20 functions as a heat dissipation fin that dissipates heat to the fluid passing through the through hole 111. According to the heat sink 2 of this example, the heat conduction joint structure S1 has the above-mentioned effect, that is, compared with the structure in which the plate end of the heat dissipation fin is joined to the side wall of the heat absorber as in the conventional heat sink, it has excellent adhesion and thermal conductivity, can also relax stress, and has excellent joint strength.

[0077] In addition, the filling portion 121 continuously filled with the solder film 122 in each through hole 111 acts as an anchor to maintain the strong integrity and close contact between the solder film 122 and the plate-like fin 21. In addition, a low thermal resistance and excellent thermal conductivity joint structure can be easily realized with the precision of thickness, parallelism, etc. in accordance with the design. In this example, the solder film 123 is also formed on the surface of the plate-like fin 21 on the opposite side to the heat absorber 20, but this film can also be omitted.

[0078] The heat sink 2 is as Figure 7As shown, a solder plate 120 having the same shape as in a plan view is placed on the upper surface of the heat absorber 20, and the plate-like fin 21 is further stacked. The plate-like fin 21 is placed so that the central region R1 is placed on the solder plate 120 and the remaining region R2 is located around it. Then, the solder plate 120 is heated and melted by the heater 4 or placed in a heating furnace, and the solder of the solder plate 120 rises through the through hole 111 of the region R1 on the central side of the plate-like fin 21, seeps out to the upper surface side to form a solder film 123 and solidifies.

[0079] The solder that does not enter the through-hole 111 and remains solidifies to form a solder film 122 between the plate-like fin 21 and the heat absorber 20. The solidified solder in the through-hole 111 forms a filling portion 121. In this way, the bonding layer 10 (thermal bonding structure S1) that is closely attached to and bonded to the heat absorber 20 is formed.

[0080] The heat absorber 20 is a solid cube made of metal, and there is no limitation on such a structure. It can also be hollow instead of solid. The material used in existing heat sinks such as aluminum, iron, and copper can be widely used. In addition, it can also be composed of a material with a heat pipe installed inside or the heat pipe itself.

[0081] As the metal material constituting the plate-like fin 21, similarly to the heat absorber 20, materials used in existing plate-like fins of heat sinks such as aluminum, iron, and copper can be widely applied. In this example, it is made of copper, and specifically, it is obtained by cutting a lotus-shaped porous metal formed body having a plurality of pores extending in one direction formed by a metal solidification method in a direction intersecting the extending direction of the pores. In the plate cut from the lotus-shaped porous metal formed body, in addition to the through holes 111, there are also non-through holes with bottoms, but such holes with bottoms also have the effect of increasing the surface area of ​​the plate surface of the region R2 that functions as a heat dissipation fin, and have the effect of promoting heat dissipation from the plate surface. The shape of the plate-like fin 21 is a square, but there is no limitation to this, and of course, shapes other than square, such as polygons and circles, can also be used.

[0082] Next, based on Figure 8a , Figure 8b and Fig. 9 An example of a heat sink having the thermally conductive bonding structure S2 will be described.

[0083] The heat sink 2A ​​of this example is also equivalent to an improved version of the heat sink described in Patent Gazette No. 2018-73869 (Japan). By using the present thermally conductive bonding structure S2, it can be manufactured more efficiently and with high precision, and is a heat sink having a structure with excellent thermal conductivity from the heat absorber to the cooling fins and excellent bonding strength.

[0084] Specifically, if Figure 8a , Figure 8b As shown, it includes: a metal heat absorber 20, which has a contact surface 20b that contacts the cooling object and transfers the heat of the cooling object through the contact surface; a metal first plate-shaped fin 21, a part area R3 of its plate surface is joined to the surface 20a of the heat absorber 20 on the opposite side of the contact surface 20b; a metal connecting body 22, which is joined to the area of ​​the plate surface of the first plate-shaped fin 21 on the opposite side of the above-mentioned plate surface corresponding to the above-mentioned part area R3; and a metal second plate-shaped fin 21A, a part area R5 of its plate surface is joined to the surface of the connecting body 22 on the opposite side of the surface joined to the above-mentioned first plate-shaped fin 21.

[0085] Furthermore, the bonding layer 10A of the heat absorber 20, the plate-like fin 21, and the connecting body 22 is formed by the heat absorber 20 as one of the two components 91, the first plate-like fin 21 as the porous substrate 11, and the connecting body 22 as the other of the two components 92, and the solder solidified body 12 is formed by the filling portion 121 filled in the through hole 111 of the region R3 and the solder films 122 and 123 extending continuously to the upper and lower plate surfaces with the filling portion 121 in the above-mentioned partial region R3 of the plate-like fin 21. The solder films 122 and 123 are in close contact with the heat absorber 20 and the connecting body 22 facing each other, respectively, and conduct heat efficiently between the heat absorber 20 and the connecting body 22. The connecting body 22 and the second plate-like fin 21A are bonded together by the heat conductive bonding structure S1 formed by the bonding layer 10, similarly to the above-mentioned example of the heat sink 2.

[0086] The remaining area R4 of the first plate-shaped fin 21 protruding around the heat absorbing body 20 and the connecting body 22 and the remaining area R6 of the second plate-shaped fin 21A protruding around the connecting body 22 respectively function as heat dissipating fins for dissipating heat to the fluid passing through the through hole 111. According to the heat sink 2A ​​of this example, the heat conduction joint structures S1 and S2 have the above-mentioned effects, that is, compared with the structure in which the plate end of the heat dissipating fin is joined to the side wall of the heat absorbing body as in the above-mentioned conventional heat sink, it has excellent adhesion and thermal conductivity, can also relax stress, and has excellent joint strength.

[0087] In this example, a structure is adopted in which only one connecting body 22 is used, and two heat dissipating fins 21 and 21A are arranged side by side in the axial direction perpendicular to the plate surface. However, a heat dissipating fin may be used in which two or more heat-conducting joint structures S2 are connected in the axial direction, two or more connecting bodies 22 are provided, and three or more heat dissipating fins are arranged side by side. According to the heat-conducting 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 transferred, and heat can be efficiently dissipated from each fin.

[0088] The heat sink 2 is as Fig. 9 As shown, the solder plate 120, the plate fin 21, the solder plate 120, the connecting body 22, the solder plate 120, and the plate fin 21A are sequentially placed and overlapped on the upper surface side of the heat absorber 20. The plate fins 21 and 21A are placed so that the central regions R3 and R5 correspond to the positions of the solder plate 120, respectively, and the remaining regions R4 and R6 are located around them. Then, each solder plate 120 is melted by heating using the heater 4, the heating furnace, etc., so that the solder of each solder plate 120 penetrates into the through-hole 111 of the central region R3 and R5 of the plate fin 21 and 21A, and the solder film 122 and 123 are formed on both sides of each fin and solidified.

[0089] The solder solidified in the through-hole 111 of each fin forms a filling portion 121. In this way, a bonding layer 10A (heat-conducting bonding structure S2) in which the plate-shaped fin 21 is closely attached to and bonded to the heat absorber 20 and the connecting body 22, and a bonding layer 10 (heat-conducting bonding structure S1) in which the plate-shaped fin 21A is closely attached to and bonded to the connecting body 22 are formed. Other structures, raw materials, modifications, etc. are the same as those of the above-mentioned heat sink 2, and therefore, description thereof is omitted.

[0090] Next, based on Fig.10 An example of a semiconductor device having the thermally conductive bonding structure S2 will be described.

[0091] The semiconductor device 3 of this example includes a substrate 30, a circuit board 31 bonded to the substrate 30, a semiconductor chip 32 bonded to the circuit board 31, and a heat sink 33 bonded to the lower surface side of the substrate 30. The present thermally conductive bonding structure S2 composed of the above-mentioned bonding layer 10A is respectively provided between the substrate 30 and the circuit board 31, between the circuit board 31 and the semiconductor chip 32, and between the substrate 30 and the heat sink 33. Reference numeral 34 denotes a bonding wire, 35 denotes a terminal, 36 denotes a housing, and 37 denotes a filler.

[0092] The semiconductor device 3 using the heat-conducting joint structure S2 of the present invention thus becomes a structure with excellent adhesion and thermal conductivity at these joints, and a structure with excellent durability that can relieve the stress generated at the joints and prevent cracking and peeling. Therefore, efficient heat dissipation and stress relief can be achieved, and miniaturization and long life of the device can be expected. In addition, due to high rigidity and assembly accuracy, it is possible to stably and efficiently provide a high-quality device with strength and accuracy that complies with the design. In this example, the heat-conducting joint structure S2 is used in each joint, but the structure can also be used only in a part of the joint. In addition, the structure of the semiconductor device is of course not limited to the figure, and can be applied to various devices.

[0093] As mentioned above, although embodiment of the present invention was described, the present invention is of course not limited to such embodiment at all, and can be implemented in various forms within the scope not departing from the gist of the present invention.

[0094] Description of Reference Numerals

[0095] S1, S2 thermal conductive joint structure

[0096] 2. 2A heat sink

[0097] 3Semiconductor devices

[0098] 4 Heater

[0099] 9 parts

[0100] 10.10A bonding layer

[0101] 11porous substrate

[0102] 12 Solder solidification body

[0103] 20Heat absorber

[0104] 20a side

[0105] 20b abutment surface

[0106] 21. 21A plate fin

[0107] 22 Connected

[0108] 30 substrates

[0109] 31 Circuit Board

[0110] 32Semiconductor chips

[0111] 33 heat sink

[0112] 91, 92 parts

[0113] 111 through hole

[0114] 120 solder plate

[0115] 121 Filling Department

[0116] 122, 123 solder film

[0117] R1-R6 area.

Claims

1. A heat-conducting joint structure composed of a joint layer, wherein the joint layer is in close contact with a component and conducts heat between the component, wherein: The bonding layer comprises: A porous metal substrate having a plurality of through holes extending in the thickness direction and opening on both the front and rear surfaces; and A solder solidified body, which is composed of a filling portion filled in the through-holes of the porous substrate and a solder film extending continuously from the filling portion to at least one plate surface, The solder film is closely attached to and bonded to the opposing components.

2. A heat-conducting joint structure consisting of a joint layer, wherein the joint layer is arranged between two components and joins the two components together, and transfers heat from one component to the other component of the two components, wherein: The bonding layer comprises: A metal porous substrate having a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces, and installed between the two components; and A solder solidified body, which is composed of a filling portion filled in the through hole of the porous substrate and a solder film extending continuously from the filling portion to the two plate surfaces, The solder film is respectively in close contact with the two opposite components and bonded together.

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

4. A thermal conductive bonding method by providing a bonding layer, wherein the bonding layer is in close contact with a component and conducts heat between the component, wherein: As the bonding layer, A porous metal substrate is provided on which a plurality of through holes extending in the thickness direction and opening on both the front and rear plate surfaces are formed. A solder solidified body is provided, wherein the solder solidified body is obtained by solidifying a solder material in a state where the solder material is filled in the through-holes of the porous substrate and a solder film is formed which extends continuously from the filled portion to at least one plate surface. The solder film is closely attached to and bonded to the opposing components.

5. A heat conductive bonding method, wherein a bonding layer is provided between two components to transfer heat from one component to the other component to bond the two components together, wherein: As the bonding layer, A porous metal substrate having a plurality of through holes extending in the thickness direction and opening on both the front and back surfaces is installed between the two components, and A solder solidified body is provided, wherein the solder solidified body is obtained by solidifying the solder material in a state where the solder material is filled in the through-holes of the porous substrate and a solder film is formed which continuously extends to the two plate surfaces along with the filled portion, The solder film is respectively in close contact with the two opposite components and bonded together.

6. The thermal conductive bonding method according to claim 4 or 5, wherein: The solder member is installed between one or two plate surfaces on the front and back sides of the porous substrate and the component opposite to the plate surface. The component, the porous substrate and the solder piece are heated in an overlapping state to melt the solder piece, and the solder piece is cooled and solidified in a state where it fills the through holes of the porous substrate and forms a solder film that extends continuously with the filled portion to the two plate surfaces, thereby forming the solder solidified body.

7. The thermal conductive bonding method according to claim 6, wherein: The heating is performed in a state where the two components, the porous substrate and the solder material are overlapped in the vertical direction and the solder material is arranged on the upper surface side of the porous substrate to melt the solder material. The solder material is dropped into and filled in the through hole by utilizing its own weight and the load from the upper component, and The solder leaks out from the lower opening of the through hole and spreads to the gap between the porous substrate and the lower component to form the solder film on the lower plate surface. The remaining portion of the solder material that has not fallen into the through hole forms the solder film on the upper board surface.

8. A heat sink having the thermally conductive bonding structure according to claim 1, comprising: The metal heat absorber as the one of the components has a contact surface that contacts the object to be cooled, and transfers heat from the object to be cooled through the contact surface; and The metal plate-shaped fin as the porous substrate has a portion of its plate surface bonded to the surface of the heat absorber opposite to the abutting surface. The plate-shaped fin is formed with a plurality of through holes opening on the plate surface. The bonding layer is formed in the partial region of the plate-shaped fin, and the bonding layer has the solder solidified body composed of the filling portion filled in the through hole formed in the region and the solder film extending continuously from the filling portion to the plate surface, the solder film is in close contact with the opposite heat absorber and conducts heat with the heat absorber, Heat is dissipated to the outside through the through holes in the remaining areas of the plate-like fins that protrude around the heat absorber.

9. A heat sink having the thermally conductive bonding structure according to claim 2, comprising: A metal heat absorber as one of the two components, which has a contact surface that contacts the object to be cooled and transfers heat from the object to be cooled through the contact surface; A first plate-shaped fin made of metal as the porous substrate, a portion of the plate surface of which is bonded to the surface of the heat absorber opposite to the abutting surface; a metal connecting body as the other of the two members, which is joined to a region corresponding to the partial region of the plate surface of the first plate-shaped fin on the side opposite to the plate surface; and a second plate-shaped fin made of metal, a portion of the plate surface of which is joined to a surface of the coupling body opposite to the surface joined to the first plate-shaped fin; The first plate-shaped fin and the second plate-shaped fin are respectively formed with a plurality of through holes opening on the plate surface. The bonding layer is formed in the partial region of the first plate-shaped fin, and the bonding layer has the solder solidified body composed of the filling portion filled in the through hole formed in the region and the solder film extending continuously with the filling portion to the two plate surfaces, the solder film is in close contact with the opposing heat absorbing body and the connecting body, respectively, and heat is transferred from the heat absorbing body to the connecting body. Heat is dissipated to the outside through the through holes of the first plate-shaped fins that protrude to the remaining areas around the heat absorber and the connecting body and the through holes of the second plate-shaped fins that protrude to the remaining areas around the connecting body.

10. A semiconductor device comprising: substrate; a circuit board bonded to the substrate; and A semiconductor chip bonded to the circuit board, The thermally conductive joint structure according to claim 2 composed of the joint layer is provided between at least one of two components, namely, between the substrate and the circuit board and between the circuit board and the semiconductor chip.

11. A semiconductor device, wherein: A heat sink is provided on the lower surface of the substrate on which the circuit board and the semiconductor chip are stacked. The heat conductive joint structure according to claim 2 composed of the joint layer is provided between the two members of the substrate and the heat sink.

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