JP7082231B2 - A conductive composition, a conductive sintered portion, and a member provided with the conductive sintered portion. - Google Patents

Description

The present invention relates to a conductive composition, a conductive sintered portion, a member having a sintered portion or a bonded portion in which the conductive composition is used, a method for joining members, and a method for manufacturing a conductive sintered portion. In particular, the present invention relates to a conductive composition applied to an electronic component, for example, an electronic component for an automobile or a communication device, and an electronic component having a sintered portion obtained by sintering the conductive composition.

In the field of electronics, as an adhesive for forming a junction in an electronic component, for example, a semiconductor element, and as a conductive paste for forming a circuit of a circuit board, for example, an organic resin and a conductive filler such as metal fine particles. , A conductive composition containing, is used. Such a conductive composition is applied to a member and then sintered or heat-cured to form a sintered portion or a joint portion.

Regarding the metal fine particles used as the conductive filler, from Patent Document 1, by using a combination of micrometer-sized particles and nanometer-sized particles, the conductivity and thermal conductivity in the sintered conductive composition can be obtained. It is known to improve sex.

Patent Documents 2 and 3 describe thermal conductivity by using plate-type silver fine particles having a central particle diameter of 0.3 to 15 μm and a thickness of 10 to 200 nm in a conductive thermosetting resin composition. , It is described that a composition having excellent low stress property, adhesive property and reflow peeling resistance can be obtained.

Patent Document 4 describes (A) silver fine particles having an average particle size of 40 nm to 400 nm, (B) a solvent, and (C) a heat absorption peak in a DSC chart obtained by measurement using a differential scanning calorimeter. It is a conductive composition for sintering containing thermoplastic resin particles having a maximum value in the range of 80 ° C. to 170 ° C., and (C) the number of primary particles of the thermoplastic resin particles has an average particle diameter of 1 to 1. A conductive composition having a size of 50 μm is disclosed. In this conductive composition, the thermoplastic resin particles in the conductive composition are melted and deformed during sintering of the conductive composition, so that the composition shrinks when the conductive composition is cured. It is described that the generation of voids that may occur due to this can be suppressed, and cracks in the bonded member, cracks in the joint portion, peeling of the joint interface, and the like can be suppressed.

Patent Document 5 discloses a conductive adhesive composition containing a conductive filler (B) having an average particle diameter of 0.5 to 10 μm and particles (A) of a solid thermoplastic resin at 25 ° C. ing. Further, Patent Document 6 describes a conductive filler (A) containing metal particles (a1) having an average particle diameter of 0.5 to 10 μm and silver particles (a2) having an average particle diameter of 10 to 200 nm, and a solid at 25 ° C. A conductive adhesive composition containing particles (B) of a thermoplastic resin in the form is disclosed. In the conductive adhesive composition described in Patent Document 6, it is described that the thermal conductivity is improved by using a combination of micrometer-sized metal particles and nanometer-sized silver particles. In these patent documents, the conductive adhesive composition contains solid thermoplastic resin particles at 25 ° C., so that the thermoplastic resin particles are melted during sintering or thermal curing to be conductive. It is described that by filling the voids existing at the adhesive interface between the cured adhesive and the material to be adhered, the adhesive strength and stress relaxation performance can be improved, and the occurrence of peeling due to a temperature change can be suppressed. Similarly in Patent Document 7, a thermoplastic resin containing micrometer-sized metal particles and nanometer-sized silver particles as a conductive filler, having an average particle diameter of 2 to 14 μm, and a melting point of 130 to 250 ° C. A conductive adhesive composition containing the particles of the above is disclosed. It is also described here that the particles of the thermoplastic resin are melted by heating and the voids in the cured conductive adhesive can be filled to prevent the material to be adhered from peeling off.

Japanese Unexamined Patent Publication No. 2015-162392 Japanese Unexamined Patent Publication No. 2016-65146 Japanese Unexamined Patent Publication No. 2014-194013 International Publication No. 2016/063931 International Publication No. 2019/013230 International Publication No. 2019/013231 International Publication No. 2020/145170

The conductive composition according to the prior art has an excellent sintered portion or joint portion obtained after sintering the conductive composition by using a conductive filler containing silver particles that can be sintered at a low temperature. Shows bond strength and good conductivity. However, on the other hand, in the sintered part or the joint where the nanometer-sized silver particles are used, the shrinkage due to the sintering of the nanometer-sized silver particles becomes large, so that voids are likely to occur inside the joint. .. In addition, since the strain between the sintered part or the joint part and the bonded member becomes large, the nanometer size is required for the long-term reliability of the joint part for joining dissimilar materials such as a silicon chip and a lead frame or a substrate. The use of silver particles is disadvantageous. On the other hand, by using the thermoplastic resin particles having the maximum value of the specific heat absorption peak, the thermoplastic resin is melted and deformed at the time of sintering the conductive composition, and the voids in the sintered portion are filled. It is known that the formation of voids in the joint portion is suppressed, the peeling of the joint portion is suppressed, and the joint strength can be improved (see FIGS. 1 and 2). However, even when such a conductive composition is used, a relatively large electronic component, for example, a chip having a size of about 5 × 5 mm to 8 × 8 mm, is still subject to repeated cooling and heating cycles. , There is a problem that peeling is likely to occur.

Especially for in-vehicle electronic components, the operating temperature fluctuates sharply in the range of -50 ° C to 150 ° C, so even under such harsh conditions, highly reliable joints can be obtained for electronic components with a large area. The conductive composition to be obtained is desired.

Therefore, the subject of the present invention is that after sintering of the conductive composition, even if the member has high conductivity and thermal conductivity and has a large area, the member is peeled off from the joining target by repeating the thermal cycle. It is an object of the present invention to provide a conductive composition for obtaining a sintered portion or a joint portion that is unlikely to occur, and a method for joining members using the conductive composition, or a method for manufacturing a conductive sintered portion or a joint portion.

The present inventors are surprisingly composed of a resin or the like in a sintered matrix of a conductive composition containing nanometer-sized silver fine particles and micrometer-sized metal particles as a conductive filler. These resin particles exert stress because the micrometer-sized particles are uniformly dispersed in the sintered portion while maintaining the shape before sintering without being significantly deformed by melting due to heating. Not only can it be relaxed, but it can also disperse stress, which in turn has high conductivity in the joints of dissimilar materials joined using a conductive composition, especially in the joints for joining relatively large particles. We have found that both the above and the long-term joining reliability can be achieved at the same time, and have completed the present invention.

The configuration of the present invention is as follows:
[1] A conductive composition containing a conductive filler and resin particles, wherein the rate of change in the maximum ferret diameter of the resin particles before and after sintering the conductive composition is less than 1.20. The conductive composition.
[2] The conductive composition according to [1], wherein the rate of change in the maximum ferret diameter is in the range of 0.9 to 1.1.
[3] The conductive composition according to [1] or [2], wherein the temperature at which the conductive composition is sintered is in the range of 80 ° C to 300 ° C.
[4] The conductive composition according to any one of [1] to [3], which contains (A) silver fine particles having an average particle diameter of 10 to 300 nm as the conductive filler.
[5] The conductive composition according to [4], which contains (B) metal particles having an average particle diameter of 0.5 to 10 μm as the conductive filler.
[6] The conductive composition according to [5], which contains (C) resin particles having an average particle diameter of 2 to 15 μm as the resin particles.
[7] The conductive composition according to [6], wherein the resin constituting the resin particles (C) is selected from the group of thermoplastic resin, thermosetting resin and silicone resin.
[8] The conductive composition according to [7], wherein the thermoplastic resin is selected from the group of polyolefins and polyamides.
[9] The average particle size of the resin particles (C) corresponds to 1 to 85% of the thickness of the sintered portion or the bonded portion obtained after sintering the conductive composition, from [6] to [6]. 8] The conductive composition according to any one of up to.
[10] The conductive composition contains 5 to 50% by mass of the silver fine particles (A), 35 to 85% by mass of the metal particles (B), and the resin, based on the mass of the conductive composition. The conductive composition according to any one of [6] to [9], which contains 0.1 to 10% by mass of particles (C).
[11] Any of [1] to [10], wherein the conductive composition further contains (D) a binder resin in an amount of 0.5 to 10% by mass based on the mass of the conductive composition. The conductive composition according to one.
[12] The ratio of the silver fine particles (A) to the metal particles (B) in the conductive composition is in the range of 5:95 to 60:40 in terms of mass ratio, from [5] to [11]. The conductive composition according to any one of the above.
[13] Further, it is selected from the group consisting of a curing agent, a curing accelerator, a solvent, an antioxidant, an ultraviolet absorber, a tackifier, a viscosity modifier, a dispersant, a coupling agent, a toughness-imparting agent, and an elastomer. The conductive composition according to any one of [1] to [12], which contains at least one component.
[14] A method of joining members using the conductive composition according to any one of [1] to [13], after sintering with respect to the maximum ferret diameter of the resin particles before sintering. The joining method comprising the step of sintering the conductive composition so that the rate of change of the maximum ferret diameter of the resin particles is less than 1.20.
[15] A method for producing a conductive sintered portion or a bonded portion using the conductive composition according to any one of [1] to [13], wherein the maximum amount of resin particles before sintering is obtained. The production method comprising the step of sintering the conductive composition so that the rate of change of the maximum ferret diameter of the resin particles after sintering with respect to the ferret diameter is less than 1.20.
[16] The method according to [14] or [15], wherein the temperature at which the conductive composition is sintered is in the range of 80 ° C to 300 ° C.
[17] The method according to any one of [14] to [16], wherein the rate of temperature rise when sintering the conductive composition is 1 to 10 ° C./min.
[18] Use of the conductive composition according to any one of claims 1 to 13 for forming a joint, a conductive layer or a circuit of a member.
[19] A sintered portion or a bonded portion containing a conductive filler and resin particles, wherein the sintered portion or the bonded portion has the conductive composition according to any one of [1] to [13]. It is obtained by sintering an object, and the ratio of the conductive filler to the cross-sectional area of the sintered portion or the joint portion is 60 to 95 area%, and the ratio of the resin particles is 1. Sintering in which the ratio of the components other than the resin particles and the conductive filler to the voids is 4 to 25 area%, and the average particle size of the resin particles is 2 to 15 μm. Part or joint.
[20] A member having the sintered portion or the joint portion according to [19].

According to the present invention, the conductive composition is applied to a member, preferably an electronic component, more preferably an in-vehicle electronic component or an electronic component for communication equipment, and is contained in the conductive composition before sintering. By sintering the conductive composition so that the maximum ferret diameter of the resin particles is equal to or less than a certain rate of change, the conductive composition has high conductivity and thermal conductivity after sintering or heat curing. Even if the member has a large area, for example, a silicon chip, it is possible to obtain a sintered portion or a bonded portion in which peeling from the bonding target is unlikely to occur.

It is a figure which shows the member provided with the joint part which uses the conductive composition by the prior art. It is a figure which shows the member provided with the joint part which uses the conductive composition by the prior art. It is a figure which shows the member provided with the joint part which uses the conductive composition by this invention. It is a figure which shows the measurement of the ferret diameter in the particle of various shapes. It is a figure which shows the DSC measurement result of a resin particle. It is a figure which shows the DSC measurement result of a resin particle. It is a figure which shows the DSC measurement result of a resin particle. It is a figure which shows the DSC measurement result of a resin particle. It is a figure which shows the electron micrograph before and after heating of a resin particle by a prior art. It is a figure which shows the electron micrograph before and after heating of a resin particle by this invention. It is a figure which shows the electron micrograph of the cross section of the conductive composition by this invention and the comparative example after sintering. It is a figure which shows the pore distribution and the crack of the conductive composition by this invention after sintering.

The conductive composition according to the present invention contains micrometer-sized particles composed of a conductive filler, a resin, or the like, and the particles have a maximum ferret diameter before and after heating or sintering the conductive composition. The rate of change of is less than 1.20. According to the present invention, the rate of change in the maximum ferret diameter of the resin particles before and after sintering is preferably less than 1.10 and in the range of 0.9 to 1.0 from the viewpoint of peeling resistance. Is particularly preferred. That is, the particles composed of a resin or the like used in the conductive composition according to the present invention have an initial shape without being melted and deformed at a temperature at which the conductive composition is sintered or heat-cured. It is almost sustainable.

In general, there are various notations for specifying the size of particles. When the particle shape is spherical, the particle diameter refers to the diameter, but in the case of polygonal particles or particles with a distorted shape, it is not always possible to define the particle diameter in the same way as spherical particles. A directional diameter exists as one criterion for defining the particle size of polygonal particles. The directional diameter is a particle diameter that can be analyzed by observing a projected image of the particles with a microscope, and one of them is the Feret's Diameter. Ferret diameter is represented by a straight line connecting any two points on the contour of the selected particle, in other words, the length of a perpendicular line sandwiched between two parallel lines in a certain direction, of which the straight line or the perpendicular line. The longest one is called the maximum ferret diameter, and the shortest one is called the minimum ferret diameter. The maximum ferret diameter is also referred to as the maximum caliper length. In the measurement of the ferret diameter of the resin particles according to the present invention, the cross section of the member coated with the conductive composition is observed using, for example, a scanning electron microscope (SEM) or a high-magnification optical microscope (digital microscope). From the acquired image, the contour of the particles can be specified using the image analysis software Image-J, and 100 to 200 particles capable of clearly confirming the shape of the particles can be selected.

According to the present invention, the rate of change of the maximum ferret diameter of the particles is the average value of the maximum ferret diameter of the particles before sintering the conductive composition and the maximum ferret of the particles after sintering the conductive composition. The average value of the diameter can be calculated and calculated according to the following formula:
Rate of change in maximum ferret diameter = average value of maximum ferret diameter after heating or sintering / average value of maximum ferret diameter before heating or sintering In Fig. 4, the particles surrounded by the solid line are polygonal particles. Yes, the particles surrounded by the dotted line are circular or elliptical particles. The particles surrounded by the solid line and the particles surrounded by the dotted line have the same equivalent circle diameter. FIG. 4 shows an example of a major axis 15, a minor axis 11, a maximum ferret diameter 14, and a minimum ferret diameter 10. As is clear from the description in FIG. 4, the maximum ferret diameter of a particle does not necessarily coincide with the major axis (major axis) of such a particle when compared with other particles having the same equivalent circle diameter. Also, the minimum ferret diameter of a particle does not always coincide with the minor axis (minor axis) of the particle.

The micrometer-sized particles made of a resin or the like used in the present invention have a rate of change in the maximum ferret diameter of the particles of less than 1.20, preferably 0.9, before and after sintering the conductive composition. It is composed of a resin such as a thermoplastic resin, a thermosetting resin, and a silicone resin as long as it can satisfy the requirement that the maximum ferret diameter of the particles is substantially unchanged from 1.1 to 1.0, more preferably 1.0. It may be composed of other materials capable of absorbing stress, for example, tin, gold, or an inorganic material such as an alloy of tin and gold. A person skilled in the art can appropriately select an appropriate material in consideration of the use of the conductive composition, the coating method, desirable physical characteristics, for example, thermal conductivity, conductivity and the like.

The particles are preferably resin particles from the viewpoint of peel resistance. When resin particles are used, the rate of change in the maximum ferret diameter of the particles is determined under the condition that the conductive composition is sintered in consideration of the sintering temperature of the conductive composition and the melting point of the resin. A resin should be selected that does not exceed 1.20, preferably 0.9 to 1.1, more preferably 1.0.

The temperature at which the conductive composition is sintered depends on the conductive filler used, the type of resin particles, the particle size, and the like, but is usually in the range of 80 ° C to 300 ° C. If the sintering temperature is lower than about 80 ° C, the conductive composition does not cure, and if the sintering temperature exceeds about 300 ° C, the resin particles melt and deform, or the melted resin becomes voids or fine particles. Since it flows into the holes, the effect of the present invention cannot be obtained. Sintering of the conductive composition can also be performed in two steps at different temperatures. When resin particles are used, for example, in the first stage (preliminary firing), the conductive composition is kept constant at about 80 to 200 ° C, preferably about 130 to 200 ° C, and more preferably about 140 to 180 ° C. It is also possible to heat and hold for a period of time, and then in the second step (sintering), sintering is performed at a temperature higher than the above temperature, for example, 150 ° C. or higher, preferably 180 ° C. or higher, and more preferably 200 ° C. or higher. The rate of temperature rise in pre-baking and sintering is usually 1 to 10 ° C./min, preferably 3 to 7 ° C./min, and more preferably 5 ° C./min. Further, the heating rate from the first stage (preliminary firing) to the second stage (sintering) does not have to be the same. Sintering can be performed in an air atmosphere or an inert gas atmosphere, for example a nitrogen atmosphere. If the surface of the member to be joined is a material that easily forms an oxide film, such as copper, sintering should be performed under an inert gas atmosphere, for example, under a nitrogen purge, in order to avoid the formation or discoloration of the oxide film. Is preferable. In this case, the oxygen concentration in the nitrogen atmosphere is 500 ppm or less, preferably 80 ppm or less, more preferably 50 ppm or less, from the viewpoint of preventing oxidation or discoloration of the surface of the member to be joined. At the above oxygen concentration, oxidation or discoloration of copper hardly occurs, but when oxygen is present at a concentration of about 0.1% (1000 ppm), discoloration of copper is observed. Further, when about 0.1% of oxygen is present in the sintered atmosphere, it also affects the combustion of organic substances such as additives contained in the conductive composition. When the oxygen concentration in the sintering atmosphere exceeds 0.1%, the sintering result is equivalent to that of sintering in the atmospheric atmosphere. In this case, the copper is completely discolored. The time for sintering the conductive composition is usually 15 to 180 minutes. The time for sintering the conductive composition is not particularly limited as long as the conductive composition is thermally cured to obtain a bonded portion or a sintered portion. For example, when sintering is performed after pre-baking, the respective sintering times may be 15 to 120 minutes, preferably 30 to 90 minutes, and more preferably 60 minutes from the viewpoint of process control. Further, in addition to or instead of pre-baking, heating is controlled to a constant heating rate, for example, 1 to 10 ° C./min, preferably 3 to 7 ° C./min, and after reaching the sintering temperature. Sintering can also be performed by maintaining the sintering temperature for a certain period of time. In this case, the sintering time is, for example, about 30 minutes to 180 minutes, preferably about 60 minutes to 120 minutes. The temperature at the time of sintering, the heating or heating rate, and the sintering atmosphere can be determined by those skilled in the art regarding the types of conductive fillers and resin particles used in the conductive composition, particle size, solvent and other resins. Etc., can be appropriately selected based on the above description, depending on the additive such as, the material of the member to be joined, and the like.

[Conductive filler (A) silver fine particles]
The conductive composition according to the present invention contains (A) nanometer-sized silver fine particles, preferably silver fine particles having an average particle diameter of 10 to 300 nm, as the conductive filler.
The average particle size of the silver fine particles (A) according to the present invention is preferably 20 to 180 nm, more preferably 30 to 170 nm, still more preferably 40 to 160 nm from the viewpoint of sinterability. If the average particle size of the silver fine particles (A) is less than 10 nm, it may be difficult to remove the coating when the silver fine particles (A) have a coating on the surface, and sintering may be hindered. When the average particle size of the silver fine particles (A) exceeds 300 nm, the specific surface area is correspondingly reduced, which may hinder sintering.

The tap density of the silver fine particles (A) is not particularly limited, but is preferably 4 g / cm ³ or more, more preferably 5 g / cm ³ or more, from the viewpoint of the sinterability of the conductive composition. It is more preferably 5.5 g / cm ³ or more. Further, from the viewpoint of avoiding precipitation of silver fine particles (A) when the conductive composition is stored for a long period of time, the tap density is preferably 8 g / cm ³ or less, preferably 7.5 g / cm ³ or less. More preferably, it is more preferably 7 g / cm ³ or less. The tap density of the silver fine particles (A) can be measured and calculated by, for example, a metal powder-tap density measuring method of JIS standard Z2512: 2012.

The shape of the silver fine particles (A) is not particularly limited, and can be, for example, a flake shape, a plate shape, a spherical shape, a cubic shape, a rod shape, or the like. When a flake shape or a plate shape is adopted as the shape of the silver fine particles (A), a sintered portion having excellent conductivity and / or thermal conductivity can be obtained after sintering the conductive composition. In addition, since flake-shaped or plate-shaped silver fine particles are sintered mainly in the minor axis direction, the internal stress is smaller than when spherical silver fine particles are used, and the silver fine particles are highly oriented, resulting in excellent reflectance. A sintered or joined portion is obtained. Further, since the flake-shaped or plate-shaped silver fine particles are not easily affected by the presence or absence of oxygen, they can be carried out in either an atmospheric atmosphere or an atmosphere of an inert gas such as nitrogen. When controlling the oxygen concentration in the sintering atmosphere, considering the material of the joint and the sinterability of the conductive composition, for example, 1000 ppm, preferably 500 ppm, more preferably 80 ppm, and most preferably about 50 ppm of oxygen. Sinter at a concentration. The pre-baking prior to sintering can also be carried out under an atmospheric atmosphere or an inert gas atmosphere, or under an inert gas atmosphere having the same oxygen concentration as described above.

The surface of the silver fine particles (A) may be coated. Coating agents for such coatings are known to those of skill in the art, and examples thereof include amines, carboxylic acids and the like. Since the carboxylic acid coating agent is easily removed during sintering, it is preferable from the viewpoint of facilitating the curing of the conductive composition after sintering and improving the heat dissipation of the sintered portion. Examples of the carboxylic acid include monocarboxylic acid, polycarboxylic acid, oxycarboxylic acid and the like. Further, as the carboxylic acid, a saturated fatty acid having 12 to 24 carbon atoms and / or an unsaturated fatty acid is preferable from the viewpoint of dispersibility in a resin or a solvent.

The coating agent may be one kind or two or more kinds of coating agents may be used in combination. A method of coating the silver fine particles (A) with the coating agent is known to those skilled in the art. For example, the silver fine particles (A) are mixed with the silver fine particles (A) in a mixer, and the silver fine particles (A) are used as the coating agent. Examples thereof include impregnation into a solution.

The content of the silver fine particles (A) in the conductive composition according to the present invention is not particularly limited, but is 5 to 50 mass with respect to 100% of the total mass of the conductive composition from the viewpoint of suppressing shrinkage due to sintering. % Is preferable, and from the viewpoint of improving conductivity and / or thermal conductivity, it is more preferably 10 to 40% by mass, and particularly preferably 15 to 35% by mass.

[Conductive filler (B) metal particles]
The conductive composition according to the present invention further contains (B) micrometer-sized metal particles, preferably metal particles having an average particle diameter of 0.5 to 10 μm, as the conductive filler.
The average particle size of the metal particles (B) according to the present invention is preferably 0.6 to 8 μm, more preferably 0.7 to 7 μm, still more preferably 0.8 to 6 μm from the viewpoint of rheology of the conductive composition. Is. When the average particle size of the metal particles (B) is less than 0.5 μm, the shrinkage suppressing effect when sintering the conductive composition is lowered, and the adhesion between the bonded member and the sintered portion is lowered. .. If the average particle size of the metal particles (B) exceeds 10 μm, the sinterability of the conductive composition is impaired, and the adhesion between the bonded member and the sintered portion is lowered.

The distribution of the average particle size of the metal particles (B) may have a single peak or may have a plurality of peaks.

The BET specific surface area of the metal particles (B) is not particularly limited, but is preferably 0.1 to 3 m ² / g, more preferably 0.2 to 2 m ² / g, and 0.3 to 1 m. It is more preferably ² / g. From the viewpoint of ensuring the surface area in contact with the member to be adhered, the BET specific surface area of the metal particles (B) is preferably 0.1 m ² / g or more. Further, from the viewpoint of reducing the amount of the binder resin (D) binder resin and / or solvent described later, the BET specific surface area of the metal particles (B) is preferably 3 m ² / g or less. The BET specific surface area of the metal particles (B) can be measured using a BET specific surface area measuring device according to the BET one-point method.

The tap density of the metal particles (B) is not particularly limited, but is preferably 4 g / cm ³ or more, preferably 5 g / cm ³ or more, from the viewpoint of the adhesive strength of the conductive composition to the bonded member. Is more preferable, and 5.5 g / cm ³ or more is further preferable. Further, from the viewpoint of avoiding precipitation of silver fine particles (A) when the conductive composition is stored for a long period of time, the tap density is preferably 8 g / cm ³ or less, preferably 7.5 g / cm ³ or less. More preferably, it is more preferably 7 g / cm ³ or less. The tap density of the metal particles (B) can be measured and calculated by, for example, the metal powder-tap density measuring method of JIS standard Z2512: 2012.

The shape of the metal particles (B) is not particularly limited. For example, a shape known to those skilled in the art such as a flake shape, a plate shape, a spherical shape, a cubic shape, and a rod shape can be used. When a flake shape or a plate shape is adopted as the shape of the metal particles (B), after sintering the conductive composition, a sintered portion having excellent conductivity and / or thermal conductivity can be obtained. In addition, since flake-shaped or plate-shaped silver fine particles are sintered mainly in the minor axis direction, the internal stress is smaller than when spherical silver fine particles are used, and the silver fine particles are highly oriented, resulting in excellent reflectance. A sintered or joined portion is obtained. Further, since the flake-shaped or plate-shaped silver fine particles are not easily affected by the presence or absence of oxygen, sintering is possible in an atmosphere of an inert gas such as nitrogen.

The metal constituting the metal particles (B) according to the present invention is not particularly limited as long as it can contribute to the conductivity of the sintered portion. Metals known to those skilled in the art, such as silver, copper, nickel, aluminum, chromium, gold, platinum, palladium, tungsten, molybdenum, etc., can be used as simple substances, as mixtures, as alloys, and as metals that can contribute to conductivity. / Or can be used as an oxide. The alloy of the metal may be a binary alloy or a ternary alloy, and the alloy may contain an element other than the metal. It is also possible to use carbon nanotubes as the material constituting the metal particles (B). Further, the metal particles (B) may be a mixture of two or more kinds.

The ratio of the silver fine particles (A) and the metal particles (B) in the conductive composition according to the present invention is not particularly limited, but from the viewpoint of the balance between thermal conductivity and bondability, the mass ratio is 5:95. The range is preferably from 60:40, more preferably from 10:90 to 50:50, and particularly preferably from 15:85 to 40:60.

[(C) Resin particles]
According to the present invention, as the particles having the rate of change in the maximum ferret diameter, (C) resin particles having an average particle diameter of 2 to 15 μm are used.
From the viewpoint of stress relaxation and crack growth suppressing effect in the sintered portion after sintering the conductive composition, the average particle size of the resin particles (C) is preferably 3 μm or more, and preferably 4 μm or more. More preferred. From the viewpoint of stress dispersion in the sintered portion after sintering the conductive composition and the thickness of the sintered portion, the average particle diameter of the resin particles (C) is preferably 13 μm or less, preferably 12 μm or less. Is even more preferable. If the average particle size of the resin particles (C) is too large, the number of the resin particles (C) per volume of the conductive resin composition becomes small, and it becomes difficult to uniformly disperse the resin particles (C). The effect of dispersing the particles is reduced. Further, if the average particle size of the resin particles (C) is large, the thickness of the sintered portion cannot be reduced accordingly, so that the heat generated from the bonded member cannot be efficiently dissipated.

When joining members, the thickness of the joined portion may be about 200 μm at the maximum depending on the application, but is usually 10 μm to 50 μm. Therefore, considering the shrinkage rate of about 15% generated when the conductive composition is heat-cured, the average particle size of the resin particles (C) is uniform in the dispersion of the resin particles (C) and uniform in the joint portion. From the viewpoint of alleviating and dispersing stress and suppressing peeling, it is preferable that the thickness is about 85% or less of the thickness of the joint after heat curing.

The shape of the resin particles (C) is preferably spherical or substantially spherical, but may be cubic, cylindrical, prismatic, conical, pyramidal, flake or the like.

The melting point of the resin particles (C) is preferably higher than the sintering temperature of the conductive composition or the conductive filler, preferably 140 to 250 ° C, preferably 170 ° C to 250 ° C, from the viewpoint of the rate of change in the maximum ferret diameter. be. According to the present invention, surprisingly, when a conductive composition containing a conductive filler and resin particles is used as an adhesive to bond a member to be bonded, for example, a substrate and a chip, the resin particles in the conductive composition By controlling the sintering conditions so that the rate of change of the maximum ferret diameter is less than 1.20, preferably 0.9 to 1.1, and more preferably 1.0, the bonding portion or the bonding method according to the prior art. It has been found that a more reliable sintered or joined portion can be obtained. Therefore, the present invention relates to a method of joining a member to be bonded, for example, a substrate for an electronic component and a chip by sintering a conductive composition, a method of manufacturing a conductive sintered portion or a bonded portion, and a conductive portion. Conductive sintered parts or joints obtained by sintering or heat-curing the composition, members having the sintered parts or joints, particularly electronic components, such as electrons for in-vehicle or communication equipment. It provides parts.

As the resin constituting the resin particles (C), a resin selected from the group consisting of a thermoplastic resin, a thermosetting resin and a silicone resin can be used. As the resin, a resin known to those skilled in the art can be used. Examples of the thermoplastic resin include polyamides, nylon resins such as nylon 11, nylon 12, nylon 6, AS resin, ABS resin, AES resin, vinyl acetate resin, polystyrene, polyolefin resins such as polyethylene and polypropylene, polyvinyl chloride, and acrylic. Resins, methacrylic resins, polyvinyl alcohol resins, polyvinyl ethers, polyacetals, polycarbonates, polyethylene terephthalates, polybutylene terephthalates, polyvinyl butyral, polysulfones, polyetherimides, ethyl celluloses, cellulose acetates, various fluororesins, polyolefin elastomers, saturated polyester resins, etc. Particles are mentioned.

Examples of the thermosetting resin include urea resin such as polyurethane resin, polyimide resin, phenol resin, epoxy resin, melamine resin, unsaturated polysell resin, and alkyd resin.

Silicone resin, also called silicon resin, is a series of resins having organopolysiloxane as the main chain.

The above-mentioned resin constituting the resin particles (C) may be used alone or may be used in combination of two or more kinds of the above-mentioned resins. Further, it may be a homopolymer composed of one kind of monomers constituting the resin, or a copolymer composed of two or more kinds of monomers.

From the viewpoint of effectively preventing peeling of the sintered portion or the joint portion from the member to be adhered, resin particles having a melting point or DSC peak in the range of 140 to 250 ° C., preferably 170 ° C. to 250 ° C. are preferable. Examples of the resin having a melting point in the range of 140 to 250 ° C. include nylon 12, nylon 11, nylon 6, polyethylene, polypropylene, vinyl acetate resin, saturated polyester resin and the like. Among them, nylon 12, nylon 11, nylon 6, and polyethylene are preferably used, nylon 12, nylon 11, and nylon 6 are more preferably used, and nylon 12 and nylon 11 are more preferably used.

According to the present invention, by controlling the conditions for sintering the conductive composition, the resin particles (C) are preferably 80 ° C. or higher and 300 ° C. or lower, which is the temperature at which the conductive composition is sintered. Even at a temperature of 140 ° C. or higher and 250 ° C. or lower, more preferably 165 ° C. or higher, the shape of the particles before sintering can be substantially maintained. Therefore, the rate of change of the maximum ferret diameter of the resin particles after sintering with respect to the maximum ferret diameter of the resin particles before sintering the conductive composition is less than 1.20, preferably 0.9 to 1.1. More preferably, it is 1.0. Conditions for sintering the conductive composition include sintering temperature, sintering time, and sintering atmosphere. When sintering is performed separately for pre-baking and sintering, the member coated with the conductive composition according to the present invention is heated to a predetermined pre-baking temperature at a constant temperature rise rate, and is constant when the pre-baking temperature is reached. For a period of time, for example, 15 to 90 minutes, preferably 30 to 60 minutes, the heating is performed at a predetermined pre-baking temperature. After the pre-baking, the member coated with the conductive composition is continuously heated to the sintering temperature at a constant heating rate, and when the sintering temperature is reached, a certain time, for example, 15 to 90 minutes, preferably 30 minutes. Heat at a predetermined sintering temperature for ~ 60 minutes. Alternatively, the conductive composition may be sintered by heating to a predetermined sintering temperature at a constant heating rate without performing pre-baking. Here, the pre-baking means to heat and hold a constant temperature, and does not necessarily perform up to sintering. Pre-calcination and sintering can be performed under an inert gas atmosphere having an oxygen concentration of 1000 ppm or less, preferably 500 ppm or less, more preferably 80 ppm or less, and most preferably 50 ppm or less, for example, a nitrogen atmosphere. By sintering the conductive composition under the above conditions, the resin particles contained in the conductive composition are melted at the time of sintering and the sintered portion is as in the case of the conventional method. The original shape before sintering is almost maintained without filling the voids in the above, and is uniformly dispersed in the conductive resin composition before and after heating or sintering, so that it is obtained after sintering. Stress at the sinter or junction is relaxed and dispersed. Further, in the method according to the prior art, in the sintered portion or the joint portion after sintering the conductive composition, the resin particles are melted at the time of sintering and enter the voids of the sintered portion, so that they are no longer baked. While it does not have the particle size of the resin particles before forming, according to the method according to the present invention, the average particle size of the resin particles (C) after sintering is almost maintained at the initial 2 to 15 μm. .. Therefore, even if the member has a large area as compared with the joint portion obtained by the conductive composition according to the prior art, the progress of cracks in the joint portion is suppressed, and eventually the bonded member and the joint portion, for example, Peeling between the silicon chip and the joint, and between the joint and the lead frame or substrate is significantly suppressed. As a result, a member having high joining reliability, preferably an electronic component having excellent joining reliability with the joining partner, and more specifically, an electronic component for an in-vehicle or communication device having excellent joining reliability with the joining partner can be obtained. can get.

The content of the resin particles (C) in the conductive composition is the mass of the conductive composition from the viewpoint of effectively preventing peeling of the sintered portion or the joint portion from the bonded member after the thermal cycle. On the other hand, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, further preferably 1% by mass or more, and particularly preferably 2% by mass or more. From the viewpoint of preventing a decrease in thermal conductivity of the sintered portion or the joint portion after the conductive composition is cured, the content of the resin particles (C) is 10% by mass with respect to the mass of the conductive composition. It is preferably less than or equal to, more preferably 7% by mass or less, still more preferably 5% by mass or less.

In the present specification, the average particle size of the metal particles (B) and the resin particles (C) is a particle size (particles) having a cumulative volume percentage of 50% by volume measured using a laser diffraction / scattering type particle size analyzer. 50% average particle size of the diameter distribution) (D50). For such a measurement, for example, a laser diffraction / scattering particle size analyzer MT-3000 manufactured by Nikkiso Co., Ltd. can be used. The average particle size of the silver fine particles (A) is 50% average particle size (D50) of the particle size distribution measured by the dynamic light scattering method. Such a particle size can be measured using, for example, a nanotrack particle distribution measuring device manufactured by Nikkiso Co., Ltd.

The melting point of the resin particles (C) is determined according to the type of resin and is well known to those skilled in the art. For measuring the melting point of the resin, for example, a differential scanning calorimetry device (DSC) can be used. 5 to 8 show DSC peaks of the resin particles (c1), (c3), (c4) and (c11) shown in Table 1 below, respectively, as an example.

In addition to the silver fine particles (A), metal particles (B), and resin particles (C), the conductive composition according to the present invention may further contain each of the components described below.
[(D) Binder resin]
The conductive composition of the present invention may further contain a binder resin (D), if necessary. By containing the binder resin (D), the conductive composition can be further imparted with fluidity and adhesiveness. The binder resin (D) is not particularly limited as long as it is liquid alone or after being dissolved in a solvent from the viewpoint of workability, but for example, polyolefin, polyvinyl butyral, polyvinyl alcohol, ethyl cellulose, saturated polyester resin, acrylic resin and the like. Thermoplastic resin, thermosetting resin such as epoxy resin, phenol resin, urethane resin, polyimide resin, etc., or silicone resin can be used. These resins may be used alone or in combination of two or more. Further, the binder resin (D) is preferably a thermosetting resin, and particularly preferably an epoxy resin, from the viewpoint of heat resistance because the temperature becomes high during sintering.

The content of the binder resin (D) is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less, based on the mass of the conductive composition. preferable. When the content of the binder resin (D) is 10% by mass or less with respect to the mass of the conductive composition, a network due to necking of the silver fine particles (A) and / or the metal particles (B) is likely to be formed. Stable conductivity and thermal conductivity can be obtained. Further, the binder resin is preferably used in an amount of 0.5% by mass or more with respect to the mass of the conductive composition from the viewpoint of fluidity and adhesiveness.

<Curing agent>
The conductive composition according to the present invention may contain a curing agent in addition to the above components. Examples of the curing agent include amine-based curing agents such as tertiary amines, alkyl ureas, and imidazoles, and phenol-based curing agents.
The content of the curing agent is preferably 2% by mass or less with respect to the mass of the conductive composition. By doing so, the uncured curing agent is less likely to remain, and the adhesion to the bonded member is improved.
<Curing accelerator>
The conductive composition of the present invention may further contain a curing accelerator. Examples of the curing accelerator include 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methyl-4-methylimidazole, and 1-cyano-2-ethyl-. Examples thereof include imidazoles such as 4-methylimidazole, tertiary amines, triphenylphosphine, urea compounds, phenols, alcohols, carboxylic acids and the like. Two or more kinds of curing accelerators may be used in combination.
When a curing accelerator is used, its content is usually 0.5% by mass or less with respect to the mass of the conductive composition.

<Solvent / Diluent>
The conductive composition according to the present invention may further be made into a paste and contain a solvent or a diluent for facilitating application. When a solvent or a diluent is used, a solvent or a diluent that does not dissolve the resin particles is used so that the shape of the resin particles in the paste can be maintained. In other respects, the solvent or diluent used is not particularly limited, but from the viewpoint of volatility during sintering, a solvent or diluent having a boiling point of 350 ° C. or lower is preferable, and a solvent or diluent having a boiling point of 300 ° C. or lower is preferable. The agent is more preferred. As the solvent or diluent, those known to those skilled in the art, such as acetate, ether, hydrocarbon, and more specifically, dibutyl carbitol, butyl carbitol acetate, and the like can be used.
The content of the solvent or the diluent is usually 15% by mass or less with respect to the mass of the conductive composition, and is preferably 10% by mass or less from the viewpoint of workability.

<Additives>
In addition to the above components, the conductive composition according to the present invention further comprises additives known to those skilled in the art, such as antioxidants, ultraviolet absorbers, tackifiers, viscosity modifiers, dispersants, coupling agents, and toughness. The additive, elastomer and the like may be contained within a range that does not impair the effects of the present invention.

The conductive composition according to the present invention comprises the above-mentioned silver fine particles (A), metal particles (B), resin particles (C), and optionally a binder resin (D), and if necessary, the above-mentioned other components. Can be produced by mixing and stirring in any order. As the method, for example, a method known to those skilled in the art such as a two-roll mill, a three-roll mill, a sand mill, a roll mill, a ball mill, a colloid mill, a jet mill, a bead mill, a kneader, a homogenizer, and a propellerless mixer is adopted. Can be done.

According to the present invention, by applying the conductive composition according to the present invention to a member and sintering or heat-treating it, a sintered portion or a bonded portion having high conductivity and thermal conductivity and in which peeling of the bonded member is unlikely to occur. Part is obtained. The conductive composition according to the present invention contains at least a conductive filler and resin particles, and when the conductive composition is applied to a member and sintered, the maximum ferret of the resin particles before sintering is performed. The conductive composition is prepared under the condition that the rate of change of the maximum ferret diameter of the resin particles after sintering with respect to the diameter is less than 1.20, preferably in the range of 0.9 to 1.1, and more preferably 1.0. Surprisingly, it was found that sintering can effectively prevent peeling of chips having a particularly large area, for example, chips having a large size such as 7 × 7 mm or 8 × 8 mm. In the sintered portion or the bonded portion obtained by the present invention, the ratio of the conductive filler to the cross-sectional area (metal area) is 60 to 95 area%, and the ratio of the resin particles (resin particle area). Is 1 to 35 area%. 4 to 25 area% of the balance (other area) is the residue of voids and binder resin and the like. The "residue of the binder resin, etc." depends on the composition of the conductive composition, for example, resin particles (C) partially melted by heating and sintering, a curing agent, a curing accelerator, an antioxidant, and ultraviolet rays. Additives such as inhibitors, tackifiers, viscosity modifiers, dispersants, coupling agents, toughness-imparting agents, elastomers, and solvent residues can be included. As described above, according to the present invention, the resin particles in the conductive composition after sintering have a rate of change of the maximum ferret diameter of less than 1.20 and are hardly deformed during sintering, so that they are sintered. The previous average particle size is maintained. The metal area, resin particle area, and other areas are obtained by observing the cross section of the sintered portion by SEM.

Therefore, the object of the present invention is a sintered portion or a joint portion obtained by sintering a conductive composition by the method according to the present invention, and a member having the sintered portion or the joint portion, preferably the sintered portion. It is also an electronic component having a portion or a joint, more preferably an electronic component for an in-vehicle or communication device having the sintered portion or the joint.

Next, an example of how to use the conductive composition of the present invention will be described.

The conductive composition according to the present invention is applied to a member such as a silicon chip or an in-vehicle electronic component by a method known to those skilled in the art such as a dispenser, a metal mask, screen printing, and a spin coat to obtain the conductive composition. After forming the layer, when the conductive composition is used for bonding the member, the member is placed so that the conductive composition layer is in contact with the joining partner (for example, a lead frame) of the member, and then the member is fired. The present invention is obtained by heat-treating (sintering) the conductive composition under the condition that the rate of change of the maximum ferret diameter of the resin particles after sintering is less than 1.20 with respect to the maximum ferret diameter of the resin particles before forming. From the conductive composition, it is possible to obtain a member having a sintered portion or a joint portion, which has high conductivity and thermal conductivity and has a large area but is unlikely to be peeled off due to repeated cold and thermal cycles.

The temperature at which the conductive composition according to the present invention is sintered is not particularly limited as long as the conductive composition is heat-cured, that is, it is sintered, but a temperature in the range of 80 ° C. to 300 ° C. is advantageous. The heating rate is usually 1 to 10 ° C./min, preferably 3 to 7 ° C./min, and more preferably 5 ° C./min. Sintering of the conductive composition can also be performed in two steps. For example, in the first step (pre-baking), sintering is performed at a relatively low temperature, for example, 80 to 200 ° C, preferably 130 to 200 ° C, and more preferably 140 to 180 ° C, and then the second step (preliminary firing). In (sintering), in order to stabilize the shape of the sintered portion or the joint portion, the temperature is higher than that of the first stage, for example, 150 ° C. or higher, preferably 180 ° C. or higher, and more preferably 200 ° C. or higher. Sintering can also be performed.

Further, in order to prevent the sintered portion or the joint portion from shrinking and becoming too hard due to excessive progress of bonding of the silver fine particles (A) and / or the metal particles (B), the sintering temperature Is preferably 300 ° C. or lower, more preferably 275 ° C. or lower, and even more preferably 250 ° C. or lower.

The time for heating the conductive composition is not particularly limited as long as the conductive composition is sintered and a sintered portion or a joint portion is obtained, but it is usually 15 minutes to 180 minutes.

The heating may be performed in air or in an atmosphere of an inert gas such as argon or nitrogen. When heated in air, the coating agent on the surface of the silver fine particles (A) is easily removed, so that sintering is easy, but on the other hand, the silver fine particles (A) and / or the metal particles (B) are easily oxidized. The formation of the oxide film may impair the conductivity and thermal conductivity of the obtained cured conductive adhesive. For example, when heated in air, when a member to be bonded that is easily oxidized (for example, a Cu substrate) is used, the member to be bonded may be oxidized and the bonding may be hindered or discolored. There is also a risk that the member will be oxidized and deteriorated.

Therefore, in order to avoid the above-mentioned problems, it is preferable to perform heating in an inert gas atmosphere, for example, in a nitrogen atmosphere. When the sintering is performed in a nitrogen atmosphere, the oxygen concentration in the nitrogen atmosphere is 1000 ppm or less, preferably 500 ppm or less, more preferably 80 ppm or less, and most preferably 50 ppm or less. The oxygen concentration in the nitrogen atmosphere at the time of sintering may be 0 ppm.

In order to efficiently dissipate heat generated from a member to be adhered such as a semiconductor element, it is preferable that the conductive composition layer is thin. For example, the thickness of the conductive composition after sintering is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less.

On the other hand, in order to alleviate the internal stress caused by the difference in the coefficient of thermal expansion between the bonded member such as a substrate and the sintered portion in the thickness direction of the sintered portion, the conductive composition layer should be thicker. Is desirable. Specifically, the thickness of the conductive composition after sintering is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more.

According to the present invention, since the shape or particle size of the resin particles (C) is maintained at a constant rate of change even after sintering, the average particle size of the resin particles (C) is applied to the member. It should be selected according to the thickness of the conductive composition layer. When the thickness of the conductive composition layer is large, the resin particles (C) having a relatively large average particle diameter can be used, while when the thickness of the conductive composition layer is small, the resin particles can be used. It is preferable that the average particle size of (C) is also correspondingly small. Appropriate average particle diameters of the resin particles (C) can be appropriately selected by those skilled in the art based on the use, composition, layer thickness and the like of the conductive composition.

The thermal conductivity of the sintered portion or the joint portion obtained by sintering the conductive composition according to the present invention is preferably 20 W / m · K or more in order to ensure the heat dissipation of the bonded member. , 35 W / m · K or more, more preferably 50 W / m · K or more. As a method for calculating the thermal conductivity, the method described in the following examples can be used.

It is evaluated that when an adhered member such as an electronic component is adhered using the conductive composition according to the present invention, peeling is less likely to occur even when undergoing a thermal cycle, that is, repeated high and low temperature changes. Examples of the method include various methods. For example, a method of performing a thermal cycle test by the method described in the following examples and measuring the ratio of the peeled area after the test can be used. From the viewpoint of thermal resistance, the ratio of the peeled area measured by this method is preferably 20% or less, more preferably 15% or less, still more preferably 10% or less, and 5%. The following is extremely preferable.

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.
A. Preparation of Conductive Composition The materials listed below are used in the amounts (% by mass) shown in Table 2 and kneaded using a three-roll mill to obtain a conductive composition (sample numbers 1 to 28). ) Was manufactured.
[(A) Silver fine particles]
a1. Spherical particles, average particle diameter d50 = 90 nm, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. a2. Spherical particles, average particle diameter d50 = 150 nm, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. a3. Spherical particles, average particle diameter d50 = 250 nm, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. [(B) Metal particles]
b1. Flake-shaped silver particles, average particle diameter d50 = 5.5 μm, tap density 7.0 g / cm ³ , manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. b2. Flake-shaped silver particles, average particle diameter d50 = 4 μm, tap density 6.7 g / cm ³ , manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. b3. Spherical silver particles, average particle diameter d50 = 0.8 μm, tap density 5.5 g / cm ³ , manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. b4. Spherical copper particles, average particle diameter d50 = 5 μm, tap density 5.0 g / cm ³ , manufactured by Mitsui Mining & Smelting Co., Ltd. [(C) resin particles]
c1. Silicone resin "KMP-600", manufactured by Shinetsu Silicone Co., Ltd., rate of change in maximum ferret diameter at 165 ° C: 0.9
c2. Thermoplastic resin "TR-1" (polyamide), manufactured by Toray Industries, Inc., rate of change in maximum ferret diameter at 140 ° C: 1.01
c3. Thermoplastic resin "PPW-5" (polypropylene), manufactured by Seishin Corporation, rate of change in maximum ferret diameter at 140 ° C: 1.02, rate of change in maximum ferret diameter at 165 ° C: 1.22
c4. Thermoplastic resin particles "SP-500" (polyamide), manufactured by Toray Industries, Inc., rate of change in maximum ferret diameter at 150 ° C: 1.02, rate of change in maximum ferret diameter at 165 ° C: 0.96
c5. Thermoplastic resin particles "SP-10" (polyamide), manufactured by Toray Industries, Inc. c6. Thermoplastic resin "SP500" (polyamide), graded product, manufactured by Toray Industries, Inc. c7. Thermoplastic resin particles "SP-10" (polyamide), graded product, manufactured by Toray Industries, Inc. c9. Thermoplastic resin particles (comparative example) "PM-200" (polyethylene), manufactured by Mitsui Chemicals, Inc. c10. Thermoplastic resin (comparative example) "Oragasol 3501EXD" (polyamide), c11 manufactured by ARKEMA. Thermoplastic resin (comparative example) "PW powder" (polyester), manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. Various characteristics of the above resin particles are as shown in Table 1 below:

In the “rate of change in maximum ferret diameter at sintering temperature” in Table 1, “◯” indicates that the conductive composition has been heated under predetermined conditions as compared with the maximum ferret diameter of the particles before sintering. The rate of change in the maximum ferret diameter was less than 1.20, and "x" indicates that it was 1.20 or more.

Further, FIG. 9 shows the resin particles (c3) according to the prior art, and FIG. 10 shows electron micrographs of the resin particles (c1) according to the present invention before and after heating. In each figure, the upper row shows before heating (room temperature), and the lower row shows after heating at 165 ° C. for 30 minutes. From FIG. 9, it is clear that the shape of the resin particles PPW-5 of c3 has changed significantly after heating, and in this case, the rate of change of the maximum ferret diameter of the resin particles of c3 is 1.20. .. On the other hand, from FIG. 10, it is clear that the resin particles KMP-600 of c1 used according to the present invention almost maintain their original shape even after heating, and in this case, the resin particles of c1 The rate of change in the maximum ferret diameter is 0.99.
[(D) Binder resin]
d1. "EPICLON 830-S" (epoxy resin liquid at room temperature), manufactured by Dainippon Ink and Chemicals Co., Ltd., epoxy equivalent 169 g / eq
d2. "ERISYS GE-21" (epoxy resin liquid at room temperature), manufactured by CVC, epoxy equivalent 125 g / eq
In addition to the above (A) to (D), a phenolic curing agent (MEH8000H, manufactured by Meiwa Kasei Co., Ltd.), 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ, curing accelerator manufactured by Shikoku Kasei Co., Ltd.), And as the solvent, dibutyl carbitol (manufactured by Tokyo Chemical Industry Co., Ltd., solvent 1) or butyl carbitol acetate (manufactured by Tokyo Chemical Industry Co., Ltd., solvent 2) was used.
B. Physical property evaluation The conductive compositions (sample numbers 1 to 28) obtained in A were each applied to a silver-plated 10 × 10 mm copper lead frame, and the coated surface was subjected to silver sputtering of 5 × 5 mm. Alternatively, a 7 × 7 mm silicon chip was placed. The copper lead frame and the silicon chip are sintered and cured by raising the temperature from room temperature to 250 ° C. at a heating rate of 3 to 7 ° C./min under a nitrogen atmosphere and heating at this temperature for 60 minutes. A metal bonded body bonded by the above conductive composition was obtained (Examples 1 to 21 and Comparative Examples 1 to 8). The thermal conductivity λ of the obtained metal joint is shown in Table 2.

For the thermal conductivity λ (W / m · K), the thermal diffusion a was measured in accordance with ASTM-E1461 using a laser flash method thermal constant measuring device TC-7000 (manufactured by ULVAC-RIKO). The specific gravity d at room temperature is calculated by the pycnometer method, and the specific heat Cp at room temperature is measured using the differential scanning calorimetry device DSC-7020 (manufactured by Seiko Denshi Kogyo Co., Ltd.) in accordance with JIS-K7123 2012. It was calculated by the formula λ = a × d × Cp.

In addition, a thermal cycle test was performed using the obtained metal joint, and the peeling area was measured. In the thermal cycle test, the operation of holding the metal joint at −50 ° C. for 30 minutes and then holding it at 150 ° C. for 30 minutes was defined as one cycle, and this was repeated 2000 cycles. Then, the ratio of the peeled area of the silicon chip generated after this thermal cycle test was measured. For the ratio of the peeled area, images of the peeled state of the metal joint after the thermal cycle test were obtained using an ultrasonic image / inspection device Fine SAT (manufactured by Hitachi Power Solutions), and the shades of these images were binarized. The image was converted into two gradations of white and black using the image software Image-J, and obtained by the following relational expression:
Percentage of peeling area (%) = peeling area (number of black pixels) ÷ silicon chip area (number of black pixels + number of white pixels) x 100
The results obtained are shown in Table 2.

In Table 2, from the viewpoint of thermal resistance, those having a peeling area ratio of less than 20% after the thermal cycle test were evaluated as “◯”, and those exceeding 20% were evaluated as “x”. In the peeling test 1, a 5 × 5 mm Si chip was used, and in the peeling test 2, a 7 × 7 mm Si chip was used. Both chips are provided with a silver coating by sputtering on the back surface.

From the results in Table 2, when a 5 × 5 mm silicon chip was used, even in the case of the comparative example, the peeling area was small and good results were obtained, while a larger 7 × 7 mm silicon chip was used. When used, it is clear that the peel resistance is insufficient in all of Comparative Examples 1 to 3, 5 and 8 which showed good results when a 5 × 5 mm silicon chip was used. .. On the other hand, for the sintered portions (Examples 1 to 21) obtained by the present invention, the peeling area after the 2000 cycle cold cycle test is small even when a 7 × 7 mm silicon chip is used. It is clear that a highly reliable joint is obtained.

Next, the conductive composition was applied to a copper substrate whose surface was coated with a noble metal such as Au, Pd, Ag, and a copper substrate whose surface was not coated, and the bonded surface was coated with a noble metal on this coated surface. Chips (2 x 2 mm or 7 x 7 mm) were placed and sintered. The coating of the substrate and the chip with the noble metal is performed by means well known to those skilled in the art, such as plating, spattering, and metallizing. The size of the chips placed in Examples 22 to 26 is 2 × 2 mm, and the size of the chips placed in Examples 27 to 40 (Table 3) and Comparative Examples 9 to 12 (Table 4) is 7 ×. It is 7 mm. In Reference Examples 1 to 5, sintering was performed without placing a chip. The rate of temperature rise during sintering is 3 to 7 ° C./min. In Examples 22 and 27, the temperature was raised to 250 ° C. at the above heating rate without pre-baking to prepare a sintered portion. The cross section of the obtained sintered portion was observed by SEM, and the ratio of the conductive filler to the entire cross section of the sintered portion (metal area in Tables 3 and 4) and the ratio of the resin particles (Tables 3 and 4). The area of the resin particles inside) was calculated. The conductive composition used, chip size, sintering conditions, metal ratio and resin particle ratio to the cross section of the sintered part, bonding strength, and the results of the reliability test (cold heat cycle test) are shown in Table 3 below. And are summarized in Table 4.

Table 3 describes examples in which the substrate and the chip are bonded according to the present invention using the conductive compositions of sample numbers 4, 7, 8 and 15 shown in Table 2. Further, in the table, the metal area (conductive filler), the resin particle area (resin particles (C)), and other areas (voids) in the left end portion and the central portion of the cross section of the sintered portion obtained by the method according to the present invention are shown. And the distribution ratio of the residue of the binder resin, etc.) is described. The smaller the difference between the left end portion and the center portion, the more the conductive filler and the resin particles are uniformly dispersed in the sintered portion. When the chip size is 2 × 2 mm (Examples 22 to 26), the difference between the left end and the center is small, and the peeling area in the reliability test is also very small, while a 7 × 7 mm chip is placed. In the case of sintering (Examples 27 to 40), although the difference between the left end portion and the central portion is slightly large, the peeling area in the reliability test is small, and it can be seen that a highly reliable joint portion is still obtained. On the other hand, in Table 4, the sintered portion obtained by using the same conductive composition (sample numbers 24 and 28) as in the cases of Comparative Examples 3 and 8 shown in Table 2, and the conductivity having the composition according to the present invention. Reference Examples 1 to 5 in which the composition (Sample No. 8) is used but the sintered portion is sintered under the sintering conditions not according to the present invention and the chips are not placed are described. In Comparative Example 9 obtained by using the conductive composition (Sample No. 24) containing no resin particles (C), the peeled area after the thermal cycle was 95%, and the resin particles (C) had a peeled area of 95%. In Comparative Example 9 obtained by using the sample number 28 having a content of more than 10%, the peeled area is 45%, while the peeled area of the sintered portion obtained by the present invention is 10 in each case. % Or less. Further, even when the conductive composition according to the present invention is used, even in Comparative Examples 11 and 12 in which the temperature rise rate is above a certain range or sintering is performed without controlling the temperature rise rate, after the thermal cycle, The peeling area is very large. From these results, it is clear that according to the present invention, a highly reliable joint can be obtained even when the area of the chip is large. In Reference Examples 1 to 5, the conductive composition according to the present invention is applied to a substrate and then sintered without placing a chip. In these reference examples, since the deviation of the distribution of the resin particles (C) between the left end portion and the center portion of the cross section of the sintered portion (the difference between the area% at the left end and the area% at the center) is small, the resin particles (C) Can be seen to be uniformly dispersed over the entire sintered portion. From the viewpoint of stress relaxation and dispersion in the sintered portion or the joint portion, it is preferable that the resin particles (C) are uniformly dispersed. It is clear that in Examples 22 to 40 according to the present invention, the bias of the distribution of the resin particles (C) is small as in the reference example, and a highly reliable joint is obtained as compared with the comparative example.

FIG. 11 is an electron micrograph showing a cross section of the conductive composition after being applied to a member (Si chip) having a size of 7 × 7 mm and sintered. From the cross-sectional views of Examples 3 and 8, in the electric composition according to the present invention, as shown in FIG. 3, the resin particles have almost the same initial shape in the sintered conductive composition. It is clear that they are evenly dispersed while being maintained. As described above, the resin particles are uniformly dispersed in the sintered conductive composition, so that the stress is relaxed and dispersed according to the present invention, and a highly reliable joint can be obtained. On the other hand, in Comparative Example 6, as shown in FIG. 2, it is clear that the resin particles are melted and deformed and distributed in a non-uniform shape.

FIG. 12 shows an example of the progress of cracks in the junction obtained by the conductive composition according to the present invention. By using the conductive composition according to the present invention and performing sintering under the condition that the rate of change of the maximum ferret diameter of the resin particles before and after sintering is less than 1.20, the resin particles can be initially obtained even after sintering. The shape can be almost maintained. Therefore, the cracks generated in the thermal cycle do not occur at the interface of the joint portion, but become fine cracks generated by tracing the resin particles existing in the joint portion. This disperses the stress and minimizes cracks due to the thermal cycle, resulting in prevention of large delamination at the interface between the member and the joint.

As described above, the present invention has been described in detail based on a specific aspect, but it is clear to those skilled in the art that various changes and modifications can be made without departing from the technical idea and scope of the present invention.

According to the present invention, a conductive material containing a conductive filler can be applied to a member, particularly a member used in the field of electronics, for example, an electronic component, and more specifically, an electronic component for an in-vehicle or communication device. It is a sexual composition that exhibits good thermal conductivity after sintering, and is reliable because relatively large members and joints are less likely to peel off or crack even after repeated significant temperature changes. Provided are a conductive composition capable of forming a high joint portion, a method of joining members using the conductive composition, and a method of manufacturing a conductive sintered portion or a joint portion.

1 Member 2 Conductive composition 3 Resin particles 4 Voids 10 Minimum Ferret diameter 11 Minor diameter 14 Maximum Ferret diameter 15 Major diameter

Claims (14)

A method of joining members using a conductive composition containing a conductive filler and resin particles, wherein the conductive composition has 50% average particle diameter (D50) of particle size distribution as the resin particles. After sintering, the resin particles (C) having a size of 2 to 15 μm are contained in an amount of 0.1 to 10% by mass based on the mass of the conductive composition, and the maximum ferret diameter of the resin particles (C) before sintering is increased. Including the step of sintering the conductive composition so that the rate of change of the maximum ferret diameter of the resin particles (C) is 0.9 or more and less than 1.20, the temperature at the time of the sintering is 80 ° C. The bonding method, wherein the temperature is 300 ° C. or lower, and the conductive composition does not contain metal-coated resin particles coated with metal. As the conductive filler, (A) silver fine particles having a 50% average particle size (D50) of a particle size distribution of 10 to 300 nm and (B) a 50% average particle size (D50) of a particle size distribution of 0.5 to 300 nm. The joining method according to claim 1, which contains 10 μm of metal particles. The bonding method according to claim 1 or 2, wherein the resin constituting the resin particles (C) is selected from the group of a thermoplastic resin, a thermosetting resin, and a silicone resin. The joining method according to claim 3, wherein the thermoplastic resin is selected from the group of polyolefins and polyamides. The conductive composition contains 5 to 50% by mass of the silver fine particles (A), 35 to 85% by mass of the metal particles (B), and (D) a binder resin with respect to the mass of the conductive composition. The joining method according to any one of claims 2 to 4, which contains 0.5 to 10% by mass. The joining method according to any one of claims 1 to 5, wherein the rate of temperature rise when sintering the conductive composition is 1 to 10 ° C./min. A method for producing a conductive sintered portion or a joint portion using a conductive composition containing a conductive filler and resin particles, wherein the conductive composition is 50% of the particle size distribution as the resin particles. The resin particles (C) having an average particle diameter (D50) of 2 to 15 μm are contained in an amount of 0.1 to 10% by mass based on the mass of the conductive composition, and the resin particles (C) before sintering are contained. The sintering includes a step of sintering the conductive composition so that the rate of change of the maximum ferret diameter of the resin particles (C) after sintering with respect to the maximum ferret diameter is 0.9 or more and less than 1.20. The production method, wherein the temperature is 80 ° C. or higher and 300 ° C. or lower, and the conductive composition does not contain metal-coated resin particles coated with metal. As the conductive filler, (A) silver fine particles having a 50% average particle size (D50) of a particle size distribution of 10 to 300 nm and (B) a 50% average particle size (D50) of a particle size distribution of 0.5 to 300 nm. The production method according to claim 7, which contains 10 μm of metal particles. The production method according to claim 7 or 8, wherein the resin constituting the resin particles (C) is selected from the group of thermoplastic resin, thermosetting resin and silicone resin. The production method according to claim 9, wherein the thermoplastic resin is selected from the group of polyolefins and polyamides. The conductive composition contains 5 to 50% by mass of the silver fine particles (A), 35 to 85% by mass of the metal particles (B), and (D) a binder resin with respect to the mass of the conductive composition. The production method according to any one of claims 8 to 10, which contains 0.5 to 10% by mass. The production method according to any one of claims 7 to 11, wherein the rate of temperature rise when sintering the conductive composition is 1 to 10 ° C./min. A sintered portion or a bonded portion containing a conductive filler and resin particles, wherein the sintered portion or the bonded portion is the bonding method according to any one of claims 1 to 6 or claims 7 to 12. The resin is obtained by the production method according to any one of the above items, and the ratio of the conductive filler to the cross-sectional area of the sintered portion or the joint portion is 60 to 95 area%. The proportion of the particles is 1 to 35 area%, the proportion of the resin particles and the components other than the conductive filler and the voids is 4 to 25 area%, and the average particle size of the resin particles is 2 to 2. Sintered or joined portion of 15 μm. A member provided with the sintered portion or the joint portion according to claim 13.

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