JP7155654B2 - Method for manufacturing conjugate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a bonded body in which two members are bonded using a paste-like bonding material containing metal particles in assembling, mounting, or the like of electronic components.

Metal particles with high thermal conductivity such as silver (Ag) and gold (Au) are dispersed in a volatile solvent to form a paste when joining two or more members in the assembly or mounting of electronic components. It is known to use a bonding material. When two members are joined using such a paste-like jointing material, the jointing material is applied to the joint surface of one member, and the other member is brought into contact with the jointing material-coated surface. Heat treatment. By this heat treatment, the volatile solvent volatilizes and the metal particles are sintered to form a bonding layer made of a conductive sintered body, thereby bonding the two members. When the bonding layer is formed from such a sintered body of metal particles, the bonding layer can be formed under relatively low temperature conditions, and the melting point of the bonding layer itself is high, so the bonding strength is greatly reduced even in a high temperature environment. It has the advantage of not

By the way, when two members are joined using such a paste-like joining material, that is, during heat treatment, a large amount of gas is generated due to the evaporation of the volatile solvent contained in the joining material. Voids tend to occur due to the retention of In addition, when a large amount of voids are generated in the bonding layer, the voids tend to cause a decrease in bonding strength or the like. Therefore, it is required to reduce voids in the bonding layer.

As a measure for reducing voids in the bonding layer, for example, Patent Document 1 discloses that in a step of connecting a base material and a semiconductor element via a connection layer having fluidity, along a connection surface between the semiconductor element and the base material, It is described that the gas is diffused to the outside of the connection layer in the process of connection by performing the connection while applying acceleration to the substrate, the connection layer and the semiconductor element in each direction.

Further, Patent Document 2 describes a method of bonding a semiconductor chip and a substrate using a bonding agent containing Cu particles and Sn particles. In this method, the bonding agent applied to the bonding surface of the semiconductor chip is heated at a temperature lower than the melting point of Sn to volatilize the paste solvent component. to sinter the bonding agent Cu and Sn in a transitional liquid phase to bond the semiconductor chip to the substrate. In addition, Cited Document 2 describes that voids generated in the bonding agent (joint portion) are suppressed by heating at a temperature lower than the boiling point of the paste solvent during temporary firing of the bonding agent. .

On the other hand, Patent Document 3 does not describe voids, but Patent Document 3 also describes a package method in which a paste as a bonding material is heated and pre-sintered, and then further heated to bond two parts. Have been described. Specifically, in Patent Document 3, a glass substrate and a low-melting-point glass paste are preliminarily sintered, and sintered glass is preliminarily welded onto the glass substrate, and then a lead frame is superimposed on the sintered glass and then heated. The lead frame is welded onto the glass substrate by melting the glass. Separately, after the cover glass and the low-melting paste are temporarily baked and the sintered glass is temporarily welded on the cover glass, the glass substrate to which the lead frame has already been welded and the cover glass are butted against each other. It is described that the sintered glass is melted to weld the cover glass to the lead frame and the glass substrate.

JP-A-2009-164203 JP 2014-199852 A Japanese Patent Publication No. 3-76025

However, in a state in which a connection layer (bonding material) is interposed between two members, the base material and the semiconductor element, as in Patent Document 1, even if acceleration is applied in the direction along the bonding surface, the connection layer Since most of the gap is blocked by the base material and the semiconductor element, it is difficult to dissipate the gas generated in the connection layer to the outside, and it is also difficult to sufficiently reduce voids. Further, Patent Document 1 describes a method of using centrifugal force generated by a rotating motion on a rotating base as means for applying acceleration. .

On the other hand, as described in Patent Documents 2 and 3, when the paste solvent component in the bonding agent (bonding material) is completely volatilized and pre-sintered before bonding the substrate and the semiconductor chip, When the semiconductor chip and the substrate are subsequently bonded, the wettability of the bonding agent between the semiconductor chip and the substrate is hindered, making it difficult to obtain high bonding strength. Further, as described in Patent Documents 2 and 3, when one component (semiconductor chip) in which a bonding agent is temporarily sintered is superimposed on the other component (substrate), the gas generated during sintering It is difficult to remove from the contact interface between the component and the bonding agent, and voids tend to remain at the contact interface between the other component and the bonding agent. Therefore, it is difficult to obtain a high bonding strength between the other part and the bonding agent.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a joined body, which can suppress the occurrence of voids in the joining layer and improve the joining strength between two members. aim.

The method for manufacturing a bonded body of the present invention uses a paste-like bonding material containing metal particles containing at least one metal selected from the group consisting of silver, gold and copper and a volatile solvent to bond the first member and the second member together. A method for manufacturing a bonded body for bonding members, wherein the bonding material is applied to the bonding surface of the first member, and the first member coated with the bonding material is heated to cause the volatilization in the bonding material. a first calcination step of forming a first calcination layer on the bonding surface of the first member by volatilizing part of the solvent, applying the bonding material to the bonding surface of the second member, and bonding a second calcination for forming a second calcination layer on the bonding surface of the second member by heating the second member coated with the material to volatilize a part of the volatile solvent in the bonding material; and heating the laminate of the first member and the second member in a state where the first calcined layer and the second calcined layer are superimposed, and the first calcined layer and the second calcined layer The volatile solvent remaining in the fired layer is volatilized, the metal particles are sintered to form a bonding layer, and the first member and the second member are bonded via the bonding layer. and a joining step of forming a joined body.

A first calcined layer is formed on the joint surface of the first member, a second calcined layer is formed on the joint surface of the second member, and a calcined layer is formed on each of the first member and the second member. Thus, the application amount of the bonding material necessary for bonding the first member and the second member can be divided into two, and the application amount of the bonding material applied to each bonding surface can be reduced, and the coating thickness can be reduced. For this reason, in the first temporary baking step and the second temporary baking step, when the volatile solvent is volatilized from the bonding material applied to each bonding surface of the first member and the second member, the gas generated in the bonding material can be smoothly released to the outside, and the formation of voids in the first calcined layer and the second calcined layer can be suppressed. Moreover, since the coating thickness of each of the bonding materials applied to the first member and the second member is small, the pre-firing time can be shortened compared to the case where the bonding material is applied to either one of the members.
Although the first calcination process and the second calcination process are performed before the joining process, the order of performing each calcination process is not particularly limited. That is, the first calcining step can be performed prior to the second calcining step, the first calcining step and the second calcining step can be performed simultaneously, or the second calcining step can be performed at the same time. It can also be performed prior to the first calcination step.

In addition, in the first temporary baking process and the second temporary baking process, a part of the volatile solvent in the bonding material is volatilized, and the first temporary baking layer and the second temporary baking layer are formed without completely volatilizing the volatile solvent. A calcined layer is formed. Therefore, in the bonding step, when the first calcined layer and the second calcined layer are superimposed, the remaining volatile solvent allows the two calcined layers to be brought into close contact with each other. In addition, in the first calcination step, the bonding material wets the bonding surface of the first member, and high adhesion is maintained between the first calcination layer and the first member. Similarly, in the second calcination step, the bonding material wets the bonding surface of the second member, and the adhesion between the second fired layer and the second member is maintained at a high level. Therefore, by heating the laminate of the first member and the second member in a state where the first calcined layer and the second calcined layer are superimposed in the bonding step, the first calcined layer and the second calcined layer The first member and the second member can be strongly bonded via the bonding layer.

Moreover, as described above, most of the volatile solvent in the first calcined layer and the second calcined layer has already volatilized in the first calcined step and the second calcined step. Therefore, in the bonding step, the metal particles may be sintered by evaporating the slightly remaining volatile solvent. Therefore, the sintering time can be relatively shortened. Also, since the amount of the volatile solvent contained in the first calcined layer and the second calcined layer is smaller than that in the bonding material, only a small amount of gas is generated when volatilizing the volatile solvent in the bonding process. Furthermore, in the first calcined layer and the second calcined layer, since a part of the volatile solvent is volatilized in each calcining step to form voids between the metal particles, gas Even if it occurs, it is smoothly released to the outside from the gaps between the first calcined layer and the second calcined layer. Therefore, voids formed in the bonding layer can be reduced, and the bonding strength between the first member and the second member can be improved.

In a preferred embodiment of the method for producing a joined body of the present invention, the first metal particles have a particle size of 100 nm or more and less than 500 nm, and the first metal particles have a particle size of 50 nm. An aggregate containing second metal particles with a particle size of 5% or more and 40% or less by volume and a third metal particle with a particle size of less than 50 nm in a proportion of 5% or less by volume, The aggregate has a D10 in the range of 0.05 μm or more and 0.25 μm or less and a D50 in the range of 0.4 μm or more and 0.6 μm or less in a volume-based particle size distribution curve measured by a laser diffraction scattering method, Furthermore, it is preferable that D90 is in the range of 1.5 μm or more and 2.5 μm or less.

By sintering the bonding material in which the metal particles having different particle diameters are combined, it is possible to form a dense bonding layer with few gaps (voids) between the metal particles. Therefore, a bonding layer having higher bonding strength can be obtained.

In a preferred embodiment of the method for producing a bonded body of the present invention, the first calcined layer and the second calcined layer have a tacking force of 500 mm N or more and 1200 mm N or less, and the non-solid content excluding the metal particles is preferably 5% by mass or more and 15% by mass or less.

In the first calcination step and the second calcination step, the content of non-solids excluding metal particles such as volatile solvents in the bonding material is reduced to 5% by mass or more and 15% by mass or less, and the tacking force is reduced to 500 mm · By forming the first calcined layer and the second calcined layer held at N or more and 1200 mm N or less, the generation of voids in the bonding layer can be suppressed, and the bonding strength between the first member and the second member. can be definitely increased. If the tacking force of the first calcined layer and the second calcined layer is less than 500 mm N, the adhesion between the first calcined layer and the second calcined layer decreases during the bonding process, and the bonding layer is not formed. It may become difficult. Further, when the tacking force of the first pre-fired layer and the second pre-fired layer exceeds 1200 mm·N, the amount of volatilization of the volatile solvent is small, so voids may occur in the bonding layer.

In a preferred embodiment of the method for manufacturing a joined body of the present invention, the first calcining step and the second calcining step have a temperature increase rate of 5° C./min or less, a heating temperature of 70° C. or more and 100° C. or less, and When the heating time is 5 minutes or more and 20 minutes or less, and the bonding step is performed at a heating rate of 10° C./minute or less, a heating temperature of 150° C. or more, and a heating time of 60 minutes or more. good.

As described above, by using the method of the present invention, the first calcined layer and the second calcined layer can be reliably formed, and voids generated in the bonding layer are suppressed, and the first member and the second member can be reliably joined.

ADVANTAGE OF THE INVENTION According to this invention, the void which generate|occur|produces in a joining layer can be suppressed, and the improvement of the joint strength of the 1st member and the 2nd member can be aimed at.

1 is a flowchart of a method for manufacturing a joined body according to the first embodiment of the present invention; FIG. It is a schematic diagram explaining each process of the manufacturing method of the joined body of 1st Embodiment of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Composition of joining material]
First, the bonding material used in the manufacturing method of the bonding material of the present embodiment will be described.
The bonding material contains metal particles containing at least one metal selected from the group consisting of silver (Ag), gold (Au) and copper (Cu), an organic substance, and a volatile solvent, and is formed into a paste. . The bonding material contains, for example, metal particles and a volatile solvent at a mass ratio of 70:30. Also, the bonding material can be produced, for example, by kneading a mixture of metal particles, an organic substance, and a volatile solvent using a kneading apparatus such as a three-roll mill.

The metal particles contained in the bonding material contain, for example, at least one metal selected from the group consisting of silver, gold and copper in an amount of 70% by mass or more. The content of silver, gold or copper in the metal particles is preferably 90% by mass or more. Metal particles of higher purity are easier to melt, so that they can be sintered at a relatively low temperature.

In addition, the metal particles are not particularly limited, but the first metal particles having a particle size of 100 nm or more and less than 500 nm are included in the range of 60 volume % or more and 95 volume % or less, and the particle diameter is 50 nm or more and less than 100 nm. It is preferable to use metal particles containing second metal particles in the range of 5 volume % or more and 40 volume % or less and third metal particles having a particle size of less than 50 nm in a proportion of 5 volume % or less. In addition, the content of the first metal particles is in the range of 70% by volume or more and 90% by volume or less, the content of the second metal particles is in the range of 10% by volume or more and 30% by volume or less, and the content of the third metal particles is 1 It is preferably in the range of vol% or less.
In addition, the metal particles are aggregates of the first metal particles, the second metal particles and the third metal particles, and in the volume-based particle size distribution curve measured by the laser diffraction scattering method, D10 is 0.05 μm or more and 0 0.25 μm or less, D50 is preferably in the range of 0.4 μm or more and 0.6 μm or less, and D90 is preferably in the range of 1.5 μm or more and 2.5 μm or less. Since the metal particles are agglomerates having a relatively wide particle size distribution as described above, it is possible to form dense agglomerates of metal particles with small gaps between the metal particles, and to form a bonding layer with few voids. can.

The particle diameters of the first metal particles, the second metal particles, and the third metal particles are measured, for example, using a SEM (scanning electron microscope), and are calculated from the projected area of the metal particles to the equivalent circle diameter (the projected area of the metal particles and It is obtained by converting the particle size obtained by calculating the diameter of a circle having the same area) into a volume-based particle size. In the laser diffraction scattering method, aggregates are put into ion-exchanged water, irradiated with 25 kHz ultrasonic waves for 5 minutes to disperse the aggregates in ion-exchanged water, and measured with a laser diffraction scattering particle size distribution analyzer (manufactured by Horiba Ltd.: LA-960) can be measured.

Volatile solvents contained in the bonding material include, for example, alcohol-based solvents, glycol-based solvents, acetate-based solvents, hydrocarbon-based solvents, and amine-based solvents. In the case of an amine-based solvent, it is preferable to use a volatile solvent having 12 or less carbon atoms. In this case, it is easy to volatilize at a low temperature, and the heating time when baking the bonding material can be shortened.

Specific examples of alcohol solvents include α-terpineol, isopropyl alcohol, pentadecyl alcohol, dodecyl alcohol and the like.
Specific examples of glycol-based solvents include ethylene glycol, diethylene glycol, and polyethylene glycol.
Specific examples of the acetate solvent include butyltoll carbitate acetate and the like.
Specific examples of hydrocarbon solvents include decane, dodecane, tetradecane, and the like.
Specific examples of amine solvents include hexylamine, octylamine, dodecylamine and the like.

The bonding material may further contain additives such as antioxidants, viscosity modifiers and resins. The content of these additives is preferably in the range of 1% by mass or more and 5% by mass or less with respect to the total amount of the bonding material.

Further, a dispersing agent may be added to the bonding material. As the dispersant, amine-based dispersants such as hexylamine, octylamine and dodecylamine can be used. When an amine-based solvent is used as the solvent, the amine-based solvent also serves as a dispersant, so the addition of a dispersant is not necessary.

[Method for producing joined body]
Next, a method for manufacturing a bonded body using the bonding material described above will be described. FIG. 2(d) shows a cross-sectional view of the bonded body 101 manufactured by the bonded body manufacturing method according to the first embodiment of the present invention. As shown in FIG. 2D, the joined body 101 is a joint formed by sintering metal particles between a substrate 10 (first member in the present invention) and an element 20 (second member in the present invention). It is joined via the layer 31 .

The substrate 10 and the element 20 to be bonded using a bonding material are not particularly limited, but examples of the substrate 10 include an insulating substrate and a circuit substrate. Examples of the element 20 include electronic components such as silicon (Si), silicon carbide (SiC), semiconductor chips, and LED elements. Although illustration is omitted, the bonding surface of the substrate 10 and the bonding surface of the element 20 are coated with, for example, one or two selected from the group consisting of silver (Ag), gold (Au), copper (Cu), and the like. Metal layers composed of more than one kind of metal are laminated. Although the method for laminating the metal layer on these joint surfaces is not particularly limited, examples thereof include a vacuum vapor deposition method, a sputtering method, a plating method, a printing method, and the like.

<First Embodiment>
As shown in FIG. 1, the manufacturing method of the joined body of the first embodiment comprises a first temporary baking step of forming a first temporary baking layer on the joint surface of the substrate 10 and a second temporary baking step of forming a first temporary baking layer on the joint surface of the element 20. A second calcination step of forming a calcined layer, a bonding step of forming a bonded body 101 by bonding the substrate 10 on which the first calcined layer is formed and the element 20 on which the second calcined layer is formed, Prepare. Note that the first calcination process, the second calcination process, and the bonding process are all performed in the atmosphere.
As shown in the flow chart of FIG. 1, the first calcination step and the second calcination step are performed before the bonding step, but the order of performing each step is not particularly limited. That is, the first calcination process can be performed before the second calcination process, or the first calcination process and the second calcination process can be performed simultaneously. Also, the second temporary baking process can be performed prior to the first temporary baking process.

[First calcination step and second calcination step]
First, as shown in FIG. 2A, a bonding material 40 is applied to the bonding surface of the substrate 10 . The bonding material 40 is applied, for example, to a position where the elements 20 are overlapped. Further, similarly, the bonding material 40 is applied to the bonding surface of the element 20 . The bonding material 40 is applied to the substrate 10 and the elements 20 by, for example, a spin coating method, a metal mask method, a screen printing method, or a discharge supply using a dispenser or the like.

Then, the substrate 10 and the element 20 each coated with the bonding material 40 are heated to partially volatilize the volatile solvent in each bonding material 40 . Thereby, as shown in FIG. 2B, a first calcined layer 41 is formed on the bonding surface of the substrate 10 and a second calcined layer 42 is formed on the bonding surface of the element 20 .

The conditions of the heat treatment in the first calcining step and the second calcining step are not particularly limited, but for example, the temperature rise rate is 5 ° C./min or less, the heating temperature is 70 ° C. or more and 100 ° C. or less, The heating time at the heating temperature is preferably in the range of 5 minutes or more and 20 minutes or less. By performing the heat treatment under the heating conditions in the above range, the first calcination step and the second calcination step are relatively low in heating temperature and short in heating time, and the balance between low energy consumption and simplification of the manufacturing process is achieved. It can be done under the given conditions.

The first calcined layer 41 and the second calcined layer 42 formed in this heat treatment have a non-solid content excluding metal particles such as a volatile solvent in the bonding material 40 of 5% by mass or more and 15% by mass. % or less, and maintain the tacking force (adhesive force) at 500 mm·N or more and 1200 mm·N or less. By forming the first calcined layer 41 and the second calcined layer 42 in this way, the gas volatilized from the first calcined layer 41 and the second calcined layer 42 can be eliminated in the subsequent bonding step. Since the amount of voids generated can be minimized, the generation of voids in the bonding layer 31 can be suppressed. In addition, since the adhesion between the calcined layers 41 and 42 can be kept high, the bonding strength between the substrate 10 and the element 20 can be reliably increased.
Note that if the tacking force of the first calcined layer 41 and the second calcined layer 42 is less than 500 mmN, the adhesion between the first calcined layer 41 and the second calcined layer 42 decreases during the bonding process. , it may become difficult to form the bonding layer 31 . In addition, when the tacking force of the first pre-fired layer 41 and the second pre-fired layer 42 exceeds 1200 mmN, the amount of volatilization of the volatile solvent is small, so voids may occur in the bonding layer 31. .

As described above, in the first calcination step and the second calcination step, the first calcination layer 41 is formed on the bonding surface of the substrate 10, and the second calcination layer 42 is formed on the bonding surface of the element 20. , Since the calcined layers 41 and 42 are formed on the substrate 10 and the element 20, respectively, the amount of the bonding material 40 required for bonding the substrate 10 and the element 20 is divided into two, and the bonding material is applied to each bonding surface. The coating amount of 40 is reduced, and each coating thickness is formed thin. In this manner, the bonding material 40 applied to each bonding surface of the substrate 10 and the element 20 is formed to have a thin coating thickness, and the heating time (temporary baking time) for volatilizing the volatile solvent from each bonding material 40 ) can be shortened. In addition, the application thickness of each bonding material 40 is formed to be thin, and since the bonding material 40 only faces each bonding surface and is not obstructed by anything else, the gas generated in the bonding material 40 can be smoothly discharged. Can be released outside. Therefore, formation of voids in the first calcined layer 41 and the second calcined layer 42 can be suppressed. The thickness of the first calcined layer 41 and the second calcined layer 42 is preferably 20 μm or more and 100 μm or less. When these thicknesses are less than 20 μm, the thickness of the bonding layer 31 obtained after the bonding process described below is thin, and the substrate 10 (the first member in the present invention) and the element 20 (the second member in the present invention) are bonded together. It becomes difficult to relax the thermal stress due to the difference in coefficient of linear expansion, and there is a risk that the substrate 10 (the first member in the present invention) or the element 20 (the second member in the present invention) will crack.
Moreover, when the thickness of each of the calcined layers 41 and 42 exceeds 100 μm, it becomes difficult for the solvent in the bonding material to escape, which may result in insufficient sintering.

Further, as described above, the first calcined layer 41 and the second calcined layer 42 are formed relatively thin, but in the first calcined step, the bonding material 40 wets the bonding surface of the substrate 10. , the adhesion between the first calcined layer 41 and the substrate 10 is maintained at a high level. Similarly, in the second calcination step, the bonding material 40 wets the bonding surface of the element 20, and the adhesion between the second calcination layer 42 and the element 20 is maintained at a high level. Therefore, after the heat treatment, the first calcined layer 41 does not come off the substrate 10 when the substrate 10 is handled, and the substrate 10 and the first calcined layer 41 can be handled as one. Similarly, when the element 20 is handled, the second calcined layer 42 does not drop off from the element 20, and the element 20 and the second calcined layer 42 can be handled as one unit.

In the first pre-baked layer 41, the content of non-solids other than metal particles decreases due to volatilization of the volatile solvent, etc., so that the intervals between the metal particles are narrowed and the bonding material applied to the bonding surface is reduced. It is formed thinner than 40. Similarly, the second calcined layer 42 also has a smaller thickness than the bonding material 40 applied to the bonding surface due to narrowing of the intervals between the metal particles due to the decrease in the non-solid content. Then, the first calcined layer 41 and the second calcined layer 42 are formed into a porous structure by forming a large number of voids where there was a volatile solvent or the like before the heat treatment.

[Joining process]
As shown in FIG. 2C, the first calcined layer 41 and the second calcined layer 42 are overlapped to arrange the substrate 10 and the element 20 . As described above, in the first temporary baking process and the second temporary baking process, part of the volatile solvent in the bonding material 40 is volatilized, and the first temporary baking is performed without completely volatilizing the volatile solvent. A layer 41 and a second calcined layer 42 are formed. Therefore, in the joining step, when the first calcined layer 41 and the second calcined layer 42 are stacked, the remaining volatile solvent allows the calcined layers 41 and 42 to be brought into close contact with each other.

Next, while the first calcined layer 41 and the second calcined layer 42 are stacked, the laminate 110 of the substrate 10 and the element 20 is heated, and the first calcined layer 41 and the second calcined layer 42 are heated. The volatile solvent is volatilized, and the bonding layer 31 is generated by sintering the metal particles. Thereby, the substrate 10 and the element 20 are bonded via the bonding layer 31 to manufacture the bonded body 101 . Note that the thickness of the bonding layer 31 is preferably 30 μm or more and 150 μm or less.
When the thickness of the bonding layer 31 is less than 30 μm, it becomes difficult to relax the thermal stress due to the difference in linear expansion coefficient between the substrate 10 (first member in the present invention) and the element 20 (second member in the present invention). (the first member in the present invention) or the element 20 (the second member in the present invention) may crack.
If the thickness of the bonding layer 31 exceeds 150 μm, the thermal resistance may increase.

During the heat treatment, a pair of pressure plates 51, 52 and the like are used to move the laminate 110 of the substrate 10 and the element 20 in the lamination direction, as indicated by the two-dot chain line in FIG. 2(c). You can pressurize. By applying pressure, the gaps between the metal particles can be narrowed to form the bonding layer 31 densely, and the bonding strength between the substrate 10 and the element 20 can be increased. The applied pressure at this time is preferably 10 MPa or less. Note that it is also possible to manufacture the joined body 101 by heating without applying pressure.

The conditions of the heat treatment in the bonding step are not particularly limited, but for example, the heating rate is 10° C./min or less, the heating temperature is 150° C. or more, and the heating time at the heating temperature is 60 minutes or more. is preferred. By performing the heat treatment under the above heating conditions, voids generated in the bonding layer 31 can be suppressed, and the substrate 10 and the element 20 can be reliably bonded.

As described above, in the first calcination process and the second calcination process, the adhesion between the first calcination layer 41 and the substrate 10 is maintained high, and the adhesion between the second calcination layer 42 and the element 20 is maintained. High quality is maintained. Therefore, by heating the laminate 110 of the substrate 10 and the element 20 in a state where the first pre-fired layer 41 and the second pre-fired layer 42 are superimposed in the bonding step, the first pre-fired layer 41 and the second pre-fired layer 42 are heated. The bonding layer 31 firmly bonded to the fired layer 42 can be formed, and the substrate 10 and the element 20 can be strongly bonded via the bonding layer 31 .

Moreover, most of the volatile solvent in the first calcined layer 41 and the second calcined layer 42 has already volatilized in the first calcined step and the second calcined step. Therefore, in the bonding step, the metal particles may be sintered by evaporating the slightly remaining volatile solvent.

In addition, since the amount of the volatile solvent contained in the first calcined layer 41 and the second calcined layer 42 is smaller than that in the bonding material 40, only a small amount of gas is generated when volatilizing the volatile solvent in the bonding process. be. Furthermore, in the first calcined layer 41 and the second calcined layer 42, a part of the volatile solvent is volatilized in each calcining step, so that voids are formed between the metal particles. Even if gas is generated in the above, the gas is smoothly released to the outside from the gaps between the first calcined layer 41 and the second calcined layer 42 . Therefore, voids formed in the bonding layer 31 can be reduced, and bonding strength between the substrate 10 and the element 20 can be improved.

The present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made to the detailed configurations without departing from the gist of the present invention.
The present invention can be applied to cases other than bonding between a substrate and an element. For example, joining metal plates (both metal plates of the same kind such as copper plate and copper plate, or different metal plates such as copper plate and aluminum plate), power module substrates and heat sinks in which circuit layers are bonded to ceramic substrates The present invention can also be applied to bonding between a semiconductor package and a lead frame.

The effects of the present invention will be described in detail below using examples, but the present invention is not limited to the following examples.

As shown in Tables 1 to 4, present invention examples 1 to 17 and comparative examples 1 and 2 of joined bodies in which the first member and the second member were joined in the atmosphere using a joining material were produced.
A 20 mm square Cu plate (thickness: 1 mm) with a gold-plated joint surface was prepared as the first member, and a 2.5 mm square Si wafer (thickness: 200 μm) with a gold-plated joint surface was prepared as the second member. prepared.
As the bonding material, silver particles (Ag) shown in Table 1 were used as metal particles, as shown in Table 2, and octylamine was used as a dispersant.

(Invention Examples 1 to 17)
A bonding material was applied to the bonding surface of the first member and the bonding surface of the second member by a metal mask method. Then, these were heated under the first heating conditions shown in Table 3 to form a first calcined layer on the bonding surface of the first member, and a second calcined layer was formed on the bonding surface of the second member. (First calcination step and second calcination step). The first calcined layer and the second calcined layer were each formed by applying the bonding material with the same coating thickness (30 μm). Then, the tacking force and non-solid content of the first calcined layer and the second calcined layer were measured by the method described later.
Next, the laminate in which the first calcined layer and the second calcined layer are superimposed is heated under the second heating conditions shown in Table 3 to form a bonding layer, and the first member and the second member are joined. A bonded body bonded via the bonding layer was produced (bonding step). Then, the void area ratio in the bonding layer and the bonding strength between the first member and the second member of the obtained bonded body were measured by the following methods. Table 4 shows the evaluation results.

(Comparative example 1)
A bonding material was applied to the bonding surface of the first member and the bonding surface of the second member by a metal mask method. The bonding material applied to each bonding surface had the same coating thickness (30 μm) as in Examples 1 to 17 of the present invention. In Comparative Example 1, only the joining step was performed without performing the first calcining step and the second calcining step. Therefore, in Comparative Example 1, the tacking force and non-solid content of the bonding material were measured and shown in Table 4.
Further, a laminate in which the bonding material applied to the first member and the bonding material applied to the second member are superimposed is heated under the second heating conditions shown in Table 2 to form a bonding layer, and the bonding layer is formed. and the second member through the bonding layer to produce a bonded body. Then, the void area ratio in the bonding layer and the bonding strength between the first member and the second member of the obtained bonded body were measured in the same manner as in Examples 1 to 17.

(Comparative example 2)
A bonding material was applied to the bonding surface of the first member by a metal mask method. The bonding material applied to the bonding surface of the first member had a thickness (60 μm) twice the coating thickness of Examples 1 to 17 and Comparative Example 1. This first member was heated under the first heating conditions shown in Table 3 to form a first calcined layer on the bonding surface of the first member (first calcining step). Then, the tacking force and non-solid content of the first calcined layer were measured.
In addition, the laminate in which the first calcined layer is superimposed on the bonding surface of the second member is heated under the second heating conditions shown in Table 3 to form a bonding layer, and the first member and the second member are bonded. A joined body was produced by joining through the joining layer. Then, the void area ratio in the bonding layer and the bonding strength between the first member and the second member of the obtained bonded body were measured in the same manner as in Examples 1 to 17 and Comparative Example 1.

(Measurement method of tacking force)
The tacking force (mm·N) was measured using a tacking force measuring device (tackiness tester manufactured by Malcom Co., Ltd.: TK-1). The tacking force is as follows: temperature 25° C., humidity 50%, thickness of the first calcined layer and second calcined layer 25 to 28 μm, device probe descending speed 2 mm/sec, weighting time 5 sec, lifting speed 5 mm/sec. Under these measurement conditions, the device probe was brought into contact with the first calcined layer and the second calcined layer, and the adhesive force when the probe (made of SUS) was separated again was taken as the adhesive force.

(Method for measuring non-solid content)
The non-solid content of the first calcined layer or the second calcined layer was measured as follows. After dissolving the first calcined layer or the second calcined layer using an organic solvent (THF: tetrahydrofuran), the dissolved material is pressure-filtered through a PTFE (polytetrafluoroethylene resin) filter to obtain silver particles. . Then, the non-solid content was obtained by subtracting the powder amount of the sampled silver particles from the amount of the first calcined layer or the second calcined layer measured in advance.

(Method for measuring void area ratio in bonding layer)
The bonded body was set in an X-ray transmission device (X-ray inspection device: XD7600NT manufactured by Nordson Advanced Technologies, Inc.), X-rays were irradiated from above the bonded body, and voids were observed. Then, the void area ratio in the bonding layer was calculated from the following formula. Here, the area of the bonding layer was the area to be bonded by the bonding layer, that is, the area of the bonding surface of the second member. In addition, since the portion where the first member and the second member are separated in the X-ray transmission apparatus is represented by the white portion, the area of this white portion was defined as the void area.
Void area ratio (%) = (void area/bonding layer area) x 100

(Method for measuring bonding strength between first member and second member)
The bonding strength was measured using a shear strength evaluation tester (bond tester: Dage Series 4000 manufactured by Nordson Advanced Technologies, Inc.). The bonding strength was measured by fixing the first member of the bonded body horizontally, using a share tool at a position 50 μm above the surface of the bonding layer, and pressing the second member horizontally from the side. The strength when broken was measured. The moving speed of the share tool was set to 0.1 mm/sec. The test was performed 5 times per condition, and the average value thereof was used as the measured value.

In Examples 1 to 17 of the present invention in which a pre-fired layer was formed on each of the first member and the second member, compared to Comparative Examples 1 and 2, the void area ratio was lower, and the first member and the second member increased bonding strength. In particular, the particle size distribution of the silver particles is such that the first metal particles are 60% by volume or more and 95% by volume or less, the second metal particles are 5% by volume or more and 40% by volume or less, and the third metal particles are 5% by volume or less. As an aggregate, D10 is 0.05 μm or more and 0.25 μm or less, D50 is 0.4 μm or more and 0.6 μm or less, D90 is 1.5 μm or more and 2.5 μm in a volume-based particle size distribution curve measured by a laser diffraction scattering method. Inventive Example 9 in which the tacking force of the first calcined layer and the second calcined layer is 500 mm N or more and 1200 mm N or less, and the non-solid content is 5% by mass or more and 15% by mass or less. At ~16, the void area ratio was lower and the bond strength was higher.

10 substrate (first member)
20 element (second member)
31, 32 bonding layer 40 bonding material 41 first calcined layer (temporarily calcined layer)
42 Second calcined layer (temporarily calcined layer)
51, 52 pressure plate 101 joined body 110 laminated body

Claims (4)

A method for manufacturing a joined body in which a first member and a second member are joined using a pasty joining material containing metal particles containing at least one metal selected from the group consisting of silver, gold and copper and a volatile solvent and
The bonding material is applied to the bonding surface of the first member, and the first member coated with the bonding material is heated to volatilize a part of the volatile solvent in the bonding material to form the first member. A first calcination step of forming a first calcination layer on the joint surface of the
The bonding material is applied to the bonding surface of the second member, and the second member coated with the bonding material is heated to volatilize a part of the volatile solvent in the bonding material to form the second member. A second calcination step of forming a second calcination layer on the joint surface of the
While the first calcined layer and the second calcined layer are stacked, the laminate of the first member and the second member is heated, and the first calcined layer and the second calcined layer volatilizing the volatile solvent remaining in the joint body, forming a joint layer by sintering the metal particles, and joining the first member and the second member through the joint layer a joining step of forming;
A method of manufacturing a joined body, comprising: 60% by volume or more and 95% by volume or less of the first metal particles having a particle size of 100 nm or more and less than 500 nm, and 5 volumes of the second metal particles having a particle size of 50 nm or more and less than 100 nm. % or more and 40 vol% or less, and an aggregate containing 5 vol% or less of third metal particles having a particle size of less than 50 nm,
The aggregate has a D10 in the range of 0.05 μm or more and 0.25 μm or less and a D50 in the range of 0.4 μm or more and 0.6 μm or less in a volume-based particle size distribution curve measured by a laser diffraction scattering method. 2. A method for producing a joined body according to claim 1, wherein D90 is in the range of 1.5 .mu.m to 2.5 .mu.m. The first calcined layer and the second calcined layer have a tacking force of 500 mm N or more and 1200 mm N or less, and a non-solid content excluding the metal particles of 5% by mass or more and 15% by mass or less. 3. The method for manufacturing a joined body according to claim 1 or 2, characterized in that: The first calcination step and the second calcination step are performed at a temperature increase rate of 5 ° C./min or less, a heating temperature of 70 ° C. or more and 100 ° C. or less, and a heating time of 5 minutes or more and 20 minutes or less at the heating temperature. ,
4. The method according to any one of claims 1 to 3, wherein the bonding step is performed at a temperature elevation rate of 10°C/min or less, a heating temperature of 150°C or more, and a heating time of 60 minutes or more at the heating temperature. A method of manufacturing the described conjugate.

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