TW201528388A - Silver paste and semiconductor device using same, and production method for silver paste - Google Patents

Abstract

The present invention provides a silver paste that is a silver paste that contains silver particles and a solvent. The silver particles contain silver particles that have a particle diameter of 1-20 μm and silver particles that have a particle diameter of 1-300 nm and that are covered by a protective agent that has a boiling point of less than 130 DEG C at atmospheric pressure.

Description

Silver paste and semiconductor device using the same, and method for producing silver paste

The present invention relates to a silver paste (silver paste), a semiconductor device using the same, and a method for producing a silver paste. More specifically, it relates to a silver paste, a semiconductor device using the same, and a method for producing a silver paste, which is used for a power semiconductor, a large integrated circuit (LSI), and a light-emitting diode ( Semiconductor components such as LEDs are adhered to support members such as lead frames, ceramic circuit boards, glass epoxy circuit boards, and polyimide substrates.

In the method of manufacturing a semiconductor device, a method of bonding a semiconductor element and a supporting member to each other is a method in which a binder resin such as an epoxy resin or a polyimide resin, a filler such as silver powder, a solvent composition, or the like is mixed into a gel. Shape and use this as an adhesive. In recent years, with the high integration of semiconductor packages, the power density (W/cm ³ ) has become high, and in order to ensure the operational stability of the semiconductor element, high heat dissipation is required for the adhesive. Further, since the ambient temperature of the semiconductor element is high, heat resistance is also required for the adhesive. Further, in order to reduce the environmental load, an adhesive containing no lead has been required. For the reasons described above, sintered silver paste containing no binder resin has been studied.

As a method of using a silver paste, the following methods are mentioned, for example, using a dispenser, a printing machine, and a stamping machine. After the silver paste is applied to the die pad of the support member, the semiconductor element is die-bonded, and the semiconductor element is adhered by heat curing to form a semiconductor device. The characteristics required for the silver paste are roughly classified into the contents of the method of adhesion and the physical properties of the silver sintered body after adhesion.

The content of the method at the time of adhesion is to prevent adhesion of the semiconductor member, and it is required to be adhered at a low temperature (for example, about 300 ° C), a low pressure (for example, about 0.1 MPa), or no pressure. Further, from the viewpoint of improving the yield, it is required to shorten the time required for adhesion. On the other hand, as a physical property of the silver sintered body after adhesion, in order to secure adhesion to a semiconductor member, high adhesiveness (high grain shear strength) is required. Further, high heat dissipation characteristics (high thermal conductivity) of the silver sintered body have also been demanded. Further, in order to ensure a long-term connection reliability, heat resistance and high density of the silver sintered body are required (the voids are small in the cured product).

As a silver paste in the past, silver pastes disclosed in, for example, Patent Documents 1 to 2 have been proposed, which use micron-sized silver particles which have been subjected to special surface treatment, whereby silver particles are sintered to each other by heating at 400 ° C or lower. (Prior Art 1). Further, for example, a silver paste disclosed in Patent Document 3 has been proposed which forms a silver sintered body by using silver particles of a nanometer size (Prior Art 2). Further, for example, a silver paste disclosed in Patent Document 4, which is a mixture of micron-sized silver particles and nano-sized silver particles having a boiling point of 130 ° C to 250 ° C, has been proposed. The organic substance having an amine group or a carboxyl group is coated (Prior Art 3).

[Previous Technical Literature] (Patent Literature)

Patent Document 1: Japanese Patent No. 4353380

Patent Document 2: Japanese Laid-Open Patent Publication No. 2012-84514

Patent Document 3: Japanese Patent No. 4414145

Patent Document 4: Japanese Laid-Open Patent Publication No. 2012-119132

The problem with the silver paste of the prior art 1 to 3 is that the density of the formed silver sintered body is insufficient, and in the silver sintered body, the temperature changes due to the energization, so that the crack easily progresses. Therefore, it is impossible to ensure adhesion of the semiconductor members to each other, and there is a fear that the semiconductor members are peeled from each other.

In view of the above problems of the prior art, it is an object of the present invention to provide a silver paste and a semiconductor device using the same, and a method for producing a silver paste, which is low temperature and low pressure (or no pressure) When sintered, a silver sintered body having a high density can be formed.

The present invention provides a silver paste comprising silver particles and a solvent, the silver particles comprising: silver particles having a particle diameter of 1 μm to 20 μm; and silver particles having a particle diameter of 1 nm to 300 nm, which are coated under atmospheric pressure. A protective agent having a boiling point of less than 130 °C.

The silver paste preferably further contains a carboxylic acid having a boiling point of 400 ° C or less at atmospheric pressure and being solid at normal temperature.

The protective agent is preferably selected from the group consisting of an amine compound, a carboxylic acid compound, At least one of the group consisting of an amino acid compound, an amino alcohol compound, and a guanamine compound.

The above protective agent is preferably selected from the group consisting of 1-aminopentane, 2-aminopentane, 3-aminopentane, 2-methylbutylamine, 3-methylbutylamine, 1,2- Dimethylpropylamine, 2,2-dimethylpropylamine, N-methylbutylamine, N-methylisobutylamine, ethylpropylamine, piperidine, methylpropylamine, Diethylamine, fluolin, triethylamine, N,N-diethylmethylamine, N,N-dimethylisopropylamine, N,N,N'-trimethylethylenediamine , N,N-Dimethylethylenediamine, 1,2-bis(methylamino)ethane, 1,2-diaminopropane, N-methylethylenediamine, 1,2-diaminoethyl At least one of a group consisting of an alkane and an acetic acid.

Preferably, the surface of the silver particles having a particle diameter of 1 μm to 20 μm is coated with an aliphatic monocarboxylic acid having 2 to 20 carbon atoms.

Preferably, the silver particles having a particle diameter of 1 μm to 20 μm are plate-like silver particles or a mixture of plate-like silver particles and spherical silver particles.

Moreover, the present invention provides a semiconductor device in which a semiconductor element and a support member for mounting a semiconductor element are adhered to each other via a sintered body obtained by sintering the silver paste.

Moreover, the present invention provides a method for producing a silver paste, which comprises mixing silver particles and a solvent to obtain a silver paste, wherein silver particles having a particle diameter of 1 μm to 20 μm are used as the silver particles; Silver particles of 1 nm to 300 nm are coated with a protective agent having a boiling point of less than 130 ° C at atmospheric pressure.

In the silver paste of the present invention, since the nano-sized silver particles and the micro-sized silver particles contained in the silver paste are sintered at the same low temperature, The density of the formed silver sintered body is high. As a result, a silver sintered body having excellent adhesion to a semiconductor member and high connection reliability can be obtained. Further, the silver sintered body also has good physical properties such as thermal conductivity and electrical conductivity.

1‧‧‧Semiconductor components

2a‧‧‧ lead frame

2b, 2c‧‧‧ lead frame (heat sink)

3‧‧‧Sintered body of silver paste

4‧‧‧ lead

5‧‧‧ molding resin

6‧‧‧Substrate

7‧‧‧ lead frame

8‧‧‧LED chip

9‧‧‧Translucent resin

10, 20‧‧‧ semiconductor devices

Fig. 1 is a graph showing the results of TG-DTA measurement of the silver nanoparticles of Example 1.

Fig. 2 is a graph showing the results of TG-DTA measurement of the silver microparticle AgC239 of Example 1.

Fig. 3 is a graph showing the results of TG-DTA measurement of the silver paste of Example 1.

Fig. 4 is a schematic cross-sectional view showing an embodiment of a semiconductor device of the present invention.

Fig. 5 is a schematic cross-sectional view showing another embodiment of the semiconductor device of the present invention.

Fig. 6 is an X-ray powder diffraction pattern of the silver nanoparticles of Example 1.

Fig. 7 is a SEM photograph of the silver nanoparticles of Example 1.

Fig. 8 is a SEM photograph of a connection cross section of the semiconductor member of Example 1.

Fig. 9 is a graph showing the results of TG-DTA measurement of the silver nanoparticles of Comparative Example 1.

Fig. 10 is a SEM photograph of a connection cross section of the semiconductor member of Comparative Example 1.

Fig. 11 is a SEM photograph of a connection cross section of the semiconductor member of Comparative Example 2.

Fig. 12 is a SEM photograph of a connection cross section of the semiconductor member of Comparative Example 3.

Hereinafter, an embodiment of the present invention will be described in detail.

The silver paste of the present embodiment contains silver particles and a solvent, and the silver particles include silver particles having a particle diameter of 1 μm to 20 μm; and silver particles having a particle diameter of 1 nm to 300 nm, which are coated under atmospheric pressure. A protective agent having a boiling point of less than 130 °C.

The silver particles used in the present embodiment include silver particles having a particle diameter of 1 μm to 20 μm (hereinafter referred to as "silver microparticles"); and silver particles having a particle diameter of 1 nm to 300 nm (hereinafter referred to as "Silver nanoparticle") is coated with a protective agent having a boiling point of less than 130 ° C at atmospheric pressure.

When the particle diameter of the silver microparticles is from 1 μm to 20 μm, the filling property of the entire silver particles is good. Therefore, the density of the obtained silver sintered body is improved, and the properties such as adhesion, thermal conductivity, and electrical conductivity are also improved. The particle diameter of the silver microparticles is preferably from 1 μm to 10 μm, more preferably from 1 μm to 5 μm. For the same reason as described above, the particle diameter of the silver nanoparticles is from 1 nm to 300 nm, preferably from 10 nm to 200 nm, more preferably from 20 nm to 100 nm. The silver nanoparticles may be efficiently filled in the gap formed by the contact of the silver microparticles, and the particle diameter of each of the silver microparticles and the silver nanoparticles may be determined within the above range. The ratio of the particle diameter of the particles to the particle diameter of the silver microparticles is preferably in the range of from 1/10 to 1/100, and the compactness of the sintered body is further improved. In addition, the particle diameter of the silver particle in this specification is the square root of the area of the silver particle when the silver particle is planarly observed using SEM (scanning electron microscope).

The shape of the silver microparticles and the silver nanoparticles is not particularly limited, and may be used when the silver microparticles and the silver nanoparticles are mixed as appropriate. The shape with higher filling can be used. Specifically, plate-like silver particles, spherical silver particles, a mixture of such silver particles, or the like can be suitably used. Further, as the silver microparticles and the silver nanoparticles, both single crystals and polycrystals can be used. In particular, in relation to the silver microparticles, in order to improve the adhesion strength to the semiconductor element and the support member, it is preferred to use platy silver particles or a mixture of platy silver particles and spherical silver particles, which can be used with semiconductor elements and The bonding area of the support member is large. Further, the "plate shape" in the present specification means a shape in which the aspect ratio (particle size/thickness) of the silver particles is in the range of 2 to 1,000.

Silver particles (including silver microparticles and silver nanoparticles) are generally coated with an organic substance (in the present specification, this organic substance is described as a "protective agent"). When the silver particles are heated, the protective agent will detach at a certain temperature to expose a clean silver surface. The activity of the silver surface is very high, and if the silver particles on the exposed surface are in contact with each other, silver atoms are diffused to grow into larger silver particles. The growth phenomenon of this silver particle is called sintering. That is, it is considered that the sintering temperature of the silver particles is the detachment temperature of the protective agent, and in order to lower the sintering temperature, it is necessary to lower the detachment temperature of the protective agent. The detachment temperature of the protective agent depends on the strength of the chemical bond formed between the silver particles and the protective agent, the thermal stability of the protective agent, and the like. The present inventors focused on the thermal stability of the protective agent, and found the fact that if a protective agent having a specific boiling point is used, the temperature at which the protective agent is detached from the silver particles is also lowered.

In order to rapidly sinter the silver paste at a temperature at which the semiconductor member is connected (generally 300 ° C or lower), the removal temperature of the protective agent for the silver microparticles and the silver nanoparticles is preferably 300 ° C or lower, more preferably 250 ° C. the following.

The detachment temperature of the protective agent can be made by performing thermogravimetry-heat difference in the atmosphere. Analysis (Thermogravimetry-Differential Thermal Analysis; TG-DTA) was obtained.

In the present embodiment, the protective agent for the silver nanoparticles is an organic compound having a boiling point of less than 130 ° C, preferably an organic compound having a boiling point of 120 ° C or lower, more preferably an organic compound having a boiling point of 110 ° C or lower. On the other hand, the lower limit of the boiling point of the protective agent is not particularly limited, and is, for example, 70 ° C or higher. Further, the boiling point in the present specification represents the boiling point at atmospheric pressure (1013 hPa).

The protective agent for silver nanoparticles, as described above, is preferably at least selected from the group consisting of an amine compound, a carboxylic acid compound, an amino acid compound, an amino alcohol compound, and a guanamine compound. 1 species. More preferably, it is selected from the group consisting of 1-aminopentane, 2-aminopentane, 3-aminopentane, 2-methylbutylamine, 3-methylbutylamine, 1,2-dimethyl Propylamine, 2,2-dimethylpropylamine, N-methylbutylamine, N-methylisobutylamine, ethylpropylamine, piperidine, methylpropylamine, diethyl Amine, morphine, triethylamine, N,N-diethylmethylamine, N,N-dimethylisopropylamine, N,N,N'-trimethylethylenediamine, N , N-dimethylethylenediamine, 1,2-bis(methylamino)ethane, 1,2-diaminopropane, N-methylethylenediamine, 1,2-diaminoethane, And at least one of the groups consisting of acetic acid. These protective agents may be used alone or in combination of two or more.

As the protective agent for the silver microparticles, a protective agent used for the above silver nanoparticles is preferably used. The protective agent used for the silver microparticles is more preferably an aliphatic monocarboxylic acid having 2 to 20 carbon atoms.

Further, in order to obtain the dense silver sintered body at the same time as the silver nanoparticle and the silver microparticle are sintered at the same time, it is preferred that the release temperatures of the two kinds of particles are similar. Specifically, the protective agent of silver nanoparticles and the protection of silver microparticles The difference in the detachment temperature of the conditioner is preferably within 50 ° C, more preferably within 30 ° C.

The amount of the protective agent of the silver nanoparticles is preferably in the range of 0.1:99.9 to 20:80 by mass ratio of the protective agent: silver nanoparticles. When the amount of the protective agent is at least the above lower limit value, the silver nanoparticles can be favorably coated. Therefore, aggregation of the silver nanoparticles can be suppressed, and the dispersibility of the silver nanoparticles with respect to the solvent can be ensured. On the other hand, when the amount of the protective agent is at most the above upper limit value, the volume shrinkage during sintering of the silver nanoparticles can be suppressed, and therefore, a highly dense silver sintered body can be easily obtained. For the same reason as described above, the amount of the protective agent to be coated with the silver microparticles is preferably in the range of 0.1:99.9 to 20:80 by mass ratio of the protective agent: silver nanoparticles.

Further, the mass ratio may be determined by measuring the TG-DTA for the silver nanoparticle or the silver microparticle by heating to a temperature at which the protective agent is sufficiently removed, and determining the mass change before and after the measurement.

Here, the reason why the silver paste of the present embodiment is excellent in sinterability is specifically described based on the first embodiment (details will be described later). In the first embodiment, silver nanoparticle coated with a protective agent, that is, N,N-dimethylethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 107 ° C), and a protective agent are also used. That is, silver microparticles (trade name: AgC239 (manufactured by Fukuda Metal Foil Co., Ltd.)) coated with dodecanoic acid are used in combination. The results of TG-DTA measurement of silver nanoparticles and silver microparticles are shown in Fig. 1 and Fig. 2, respectively. As can be seen from Fig. 1, N,N-dimethylethylenediamine on the surface of the silver nanoparticles is detached at about 225 °C. Further, as is apparent from Fig. 2, the dodecanoic acid on the surface of the silver microparticles was desorbed at about 250 °C. The TG-DTA measurement results of the silver paste prepared by mixing these silver particles are shown in Fig. 3. The temperature at which the organic material is detached from the silver paste is At about 250 ° C, the weight is reduced by about 9.5% by weight. The detachment temperature of the organic substance in the TG-DTA measurement was 250 ° C. However, even if it was about 200 ° C, the same weight loss (9.5 wt%) as that at 250 ° C was obtained as long as it was heated for a certain period of time. That is, the silver paste of Example 1 can be sintered by completely removing the organic substance at about 200 °C. Moreover, since the difference between the removal temperature of the protective agent of the silver nanoparticle and the protective agent of the silver microparticle is less than 25 ° C, the silver nanoparticle and the silver microparticle can be sintered almost simultaneously, and a dense silver sintering can be formed. body. Therefore, the characteristics (grain shear strength, volume resistivity, and thermal conductivity) of the silver sintered body are also good.

The mixing ratio of the silver nanoparticle to the silver microparticle is preferably 60:40 to 95:5, more preferably 70:30 to 90:10, further in terms of the mass ratio of the silver nanoparticle to the silver microparticle. Good is 80:20~90:10. When the mixing ratio of the silver nanoparticles is within the above range, the amount of pore filling formed by bringing the silver microparticles into contact with each other becomes an appropriate amount, so that the density of the silver sintered body can be further improved. .

The amount of silver particles (the total of the silver microparticles and the silver nanoparticles) in the silver paste can be appropriately determined in accordance with the viscosity or the thixotropy of the intended silver paste. In order to make the adhesion strength and thermal conductivity of the silver sintered body easier to exhibit, it is preferable that the silver particles are 80 parts by mass or more in 100 parts by mass of the silver paste. In addition, the silver paste may contain silver particles other than the silver microparticles and the silver nanoparticles as the silver particles, and the content thereof is preferably 50% by mass or less, and more preferably 30% by mass or less based on the total amount of the silver particles. Further more preferably, it is 10% by mass or less.

The solvent of the present embodiment is liquid as long as it is at normal temperature. The solvent is not particularly limited, and a known solvent can be used. The solvent may be selected from the group consisting of alcohols, aldehydes, carboxylic acids, ethers, esters, amines, monosaccharides, polysaccharides, linear hydrocarbons, fatty acids, aromatics, etc., and may also be plural The above solvents are used in combination.

The boiling point of the solvent is not particularly limited, but is preferably from 100 ° C to 350 ° C, more preferably from 130 ° C to 300 ° C, still more preferably from 150 ° C to 250 ° C. When the boiling point of the solvent is 100 ° C or more, the use of the silver paste suppresses the volatilization of the solvent at room temperature, so that the viscosity stability and coating properties of the silver paste can be ensured. In addition, when the boiling point of the solvent is 350 ° C, it is possible to prevent the solvent from remaining in the silver sintered body without evaporating when the semiconductor element is connected to the temperature of the support member. Therefore, the characteristics of the silver sintered body can be more favorably maintained.

The solvent is preferably a solvent suitable for the dispersion of the silver particles from the solvent as described above, and specifically, from the viewpoint of improving the thermal conductivity, electrical conductivity, and adhesion strength of the silver sintered body. A solvent having an alcohol structure, an ether structure, or an ester structure is selected. Examples of the solvent in the present embodiment include butyl cellosolve, carbitol, butyl sulphate acetate, carbitol acetate, ethylene glycol diethyl ether, and dipropylene glycol methyl ether. Acetate, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n-methyl ether, isodecyl cyclohexanol, butyrin, terpineol, and the like.

The amount of the solvent in the silver paste is preferably less than 20 parts by mass in 100 parts by mass of the silver paste. When the solvent is less than 20 parts by mass, volume shrinkage accompanying solvent volatilization during sintering of the silver paste can be suppressed, and the denseness of the formed silver sintered body can be more easily improved.

The silver paste of the present embodiment may further contain an additive. Add to The agent is preferably a carboxylic acid having a boiling point of 400 ° C or less at atmospheric pressure and being solid at normal temperature. Specific examples of the additive include stearic acid, lauric acid, docosanoic acid, sebacic acid, 1,16-octadecanedioic acid, and the like. The amount of the additive is preferably 2 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0 parts by mass in 100 parts by mass of the silver paste.

Further, the silver paste of the present embodiment may further contain components other than silver particles, a solvent, and an additive, within a range that does not impair the effects of the present invention. Examples of the components other than the silver particles, the solvent, and the additive include metal particles other than silver, an anti-settling agent for silver particles in the silver paste, and a flux for promoting sintering of the silver particles. When the component is an organic compound, the organic compound is preferably the same as the solvent, and is released to the outside of the system at a temperature at which the silver paste is sintered. The amount of the components other than the silver particles, the solvent, and the additive is preferably 2 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0 parts by mass, per 100 parts by mass of the silver paste.

In the silver paste according to the present embodiment, it is preferred that the silver paste is subjected to thermogravimetry-thermal differential analysis under the conditions of a temperature increase rate of 10 ° C/min from room temperature in the atmosphere. The weight loss occurs when the organic matter in the mash is detached, and the temperature at which the weight reduction is stopped is less than 270 °C.

Further, in the silver paste according to the present embodiment, it is preferred that the silver microparticles and the silver nanoparticles are subjected to thermogravimetry-heat difference in a temperature environment at a temperature increase rate of 10 ° C/min from room temperature. In the analysis and measurement, the weight loss occurs due to the detachment of the organic substance on the surface of the silver particles, and the difference between the temperature at which the weight reduction is stopped for the silver microparticles and the silver nanoparticles is within 50 °C.

When the silver paste of the present embodiment is to be produced, for example, as long as appropriate Dispersing/dissolving device such as agitator, crusher, three-roll mill, planetary mixer, etc., together with silver nanoparticles, silver microparticles, and solvent (further with additives) It may be heated as needed and mixed, dissolved, granulated, kneaded or dispersed to make it a uniform gel.

As a method of sintering the silver paste of the present embodiment by heating, a known method can be used. In addition to external heating by a heater, an ultraviolet lamp, a laser, a microwave, or the like can be suitably used. The heating temperature of the silver paste is preferably such that the protective agent, solvent and additives are separated from the temperature outside the system. Specifically, the heating temperature is preferably in the range of 150 ° C or more and 300 ° C or less, more preferably 150 ° C or more and 250 ° C or less. When the general semiconductor member is connected by setting the heating temperature to 300 ° C or lower, damage to the member can be avoided. Further, by setting the heating temperature to 150 ° C or higher, the release of the protective agent is likely to occur.

The heating time of the silver paste may be set to a temperature at which the organic substance such as a protective agent or a solvent is removed at the set temperature. The appropriate heating temperature and range of heating time can be estimated by performing TG-DTA measurement of the silver paste.

Further, the step of heating the silver paste can be appropriately determined. In particular, when sintering is carried out at a temperature exceeding the boiling point of the solvent, if the temperature is preheated at a temperature equal to or lower than the boiling point of the solvent, the solvent is volatilized to a certain extent in advance and then sintered, whereby a dense silver sintered body can be easily obtained. The rate of temperature rise when the silver paste is heated is not particularly limited when it is sintered at a boiling point not at the solvent. When sintering is performed at a temperature exceeding the boiling point of the solvent, it is preferred to set the temperature increase rate to 1 ° C / sec or less, or to carry out a preheating step.

The silver sintered body obtained by sintering the silver paste in the above manner is preferably a silver sintered body having a volume resistivity, a thermal conductivity, an adhesive strength, and a density of 1 × 10 ^-5 Ω, respectively. Below cm, 30W/m. K or more, 10 MPa, and 60% or more. Further, the density of the silver sintered body is calculated based on the following formula.

Density [%] = density of silver sintered body [g/cm ³ ] × 100 / theoretical density of silver [10.49 g/cm ³ ]

In the semiconductor device of the present embodiment, the semiconductor element and the semiconductor element mounting support member are adhered to each other via a sintered body obtained by sintering the silver paste of the present embodiment.

Fig. 4 is a schematic cross-sectional view showing an example of a semiconductor device of the embodiment. As shown in FIG. 4, the semiconductor device 10 includes a lead frame 2a which is a support member for mounting a semiconductor element, lead frames (heat sinks) 2b and 2c, and a semiconductor element 1 which is silver paste according to the present embodiment. The sintered body 3 is connected to the lead frame 2a; and, the molding resin 5, which is molded. The semiconductor element 1 is connected to the lead frames 2b, 2c via two lead wires 4, respectively.

Fig. 5 is a schematic cross-sectional view showing another example of the semiconductor device of the embodiment. As shown in FIG. 5, the semiconductor device 20 includes a substrate 6, a lead frame 7, which is a semiconductor element mounting supporting member formed to surround the substrate 6, and a semiconductor LED wafer 8 via the present embodiment. The silver paste sintered body 3 is connected to the lead frame 7; and, the light-transmitting resin 9, which seals these. The LED chip 8 is connected to the lead frame 7 via the lead wires 4.

In these semiconductor devices, for example, the semiconductor element and the supporting member for mounting the semiconductor element can be adhered to each other by: silver paste Applying to a semiconductor element mounting supporting member by a dispensing method, a screen printing method, an imprint method, or the like, mounting the semiconductor element on a portion to which the silver paste has been applied, and using a heating device to deposit the silver paste sintering. Further, after sintering the silver paste, a semiconductor device is obtained by performing a wire bonding step and a sealing step.

Examples of the semiconductor element mounting supporting member include a 42 alloy lead frame, a copper lead frame, and a palladium PPF lead frame; and a glass epoxy substrate (a glass fiber reinforced ring) An organic substrate such as a substrate made of an oxyresin or a BT substrate (a substrate obtained by using a BT resin composed of a cyanate monomer and an oligomer thereof and bismaleimide).

In the adhesion surface of the semiconductor element supporting member for semiconductor element mounting, it is preferable to provide unevenness (roughening treatment) in order to improve the adhesion to the silver paste. When a semiconductor element mounting supporting member having a fine uneven surface (for example, a distance between convex portions in the uneven surface is less than 1 μm) is used, the silver nanoparticles in the silver paste of the present embodiment are carried by the conductor element. It is trapped by the concave portion of the surface of the support member, so that higher adhesion can be obtained.

[Examples]

The invention will be more specifically described by way of the examples shown below. The invention is not limited to the embodiments.

The measurement of each characteristic in each of the examples and the comparative examples was carried out as follows.

(1) Phase identification of silver nanoparticles (X-ray diffraction (XRD) measurement)

About 100 mg of silver nanoparticles are placed in a glass jar for XRD measurement (glass) In the cell, this was mounted on a sample holder of an X-ray powder diffraction device (model: Rigaku CN4036). CuK α ray was generated at an acceleration voltage of 40 kV and a current of 20 mA, and monochromatic photochemical was performed by a graphite single photometer as a measurement ray source. The diffraction pattern of the silver particles was measured in the range of 2 θ = 5° to 85°.

(2) Desorption temperature of organic matter (TG-DTA measurement)

10 mg of silver particles or silver paste was placed in an aluminum sample pan for TG-DTA measurement, and this was mounted on a sample holder of a TG-DTA measuring device (manufactured by SII Technology, model: EXSTAR6000 TG/DTA6300). While the dry air was passed through at a flow rate of about 400 mL/min, the sample was heated from room temperature to about 500 ° C at a temperature increase rate of 10 ° C/min, and the weight change and thermal behavior at this time were measured. The stop point of the weight change is set as the end temperature at which the organic matter is detached.

(3) Density and density of silver sintered body

The silver paste was preheated at 110 ° C for 10 minutes by a hot plate (manufactured by Shinei Hall, model: SHAMAL HOTPLATE HHP-401), and further heated at 200 ° C for 1 hour, thereby obtaining a silver sintered body (about 10 mm × 10 mm × 1mm). The silver sintered body produced was ground with a sandpaper (No. 800), and the volume and mass of the polished silver sintered body were measured. From these values, the density of the silver sintered body was calculated, and the density was further calculated according to the following formula.

Density [%] = density of silver sintered body [g/cm ³ ] × 100 / theoretical density of silver [10.49 g/cm ³ ]

(4) Grain shear strength

0.1 mg of silver paste was applied to a silver-plated copper lead frame (contact portion: 10 × 5 mm) On top of this, a 1 mm × 1 mm silver-plated germanium wafer (silver plating thickness: 0.1 μm, wafer thickness: 400 μm) or a gold-plated germanium wafer (gold plating thickness: 0.1 μm, wafer thickness: 400 μm) was adhered thereto. This was heated at 200 ° C for 1 hour using a hot plate (manufactured by Shinei Hall, model: SHAMAL HOTPLATE HHP-401). The adhesion strength of the obtained silver sintered body was evaluated based on the grain shear strength [MPa]. Using a universal bond strength tester (manufactured by Nordson DAGE Co., Ltd., 4000 series), the gold-plated tantalum wafer was pressed in the horizontal direction at a measurement speed of 500 μm/s and a measurement height of 100 μm to measure the crystal of the silver sintered body. Grain shear strength [MPa].

(5) Thermal conductivity

The silver paste was preheated at 110 ° C for 10 minutes using a hot plate (manufactured by Shinei Hall, model: SHAMAL HOTPLATE HHP-401), and further heated at 200 ° C for 1 hour, thereby obtaining a silver sintered body (about 10 mm × 10 mm × 1 mm). ). The thermal diffusivity of the silver sintered body was measured by a laser flash method (manufactured by NETZSCH Co., Ltd., model: LFA 447, measuring temperature: 25 ° C), and further, the thermal diffusivity, and the differential scanning calorimeter ( The product of specific heat and sintered density obtained by PerkinElmer Co., Ltd., model: Pyris1), calculated the thermal conductivity of the silver sintered body at 25 ° C [W / m. K].

(6) Volume resistivity

The silver paste was applied to a glass plate, and preheated at 110 ° C for 10 minutes using a hot plate (manufactured by Shinjeong Hall, model: SHAMAL HOTPLATE HHP-401), and further heated at 200 ° C for 1 hour, thereby being on a glass plate. A silver sintered body of 1 mm × 50 mm × 0.03 mm was obtained. This silver sintered body was manufactured by the 4-terminal method (Advantest Co., Ltd., model: R687E DIGTAL) MULTIMETER) Determination of volume resistivity [μΩ. Cm].

(7) Cross-sectional observation of silver sintered body

0.1 mg of silver paste was applied to a silver-plated copper lead frame (contact portion: 10 × 5 mm, silver plating thickness: about 4 μm), and a 1 mm × 1 mm gold-plated tantalum wafer was adhered thereon (gold plating thickness: 0.1) Μm, wafer thickness: 400 μm). This was heated at 200 ° C for 1 hour using a hot plate (manufactured by Shinei Hall, model: SHAMAL HOTPLATE HHP-401). The connected sample was embedded in an epoxy resin and ground until the cross section of the gold-plated tantalum wafer/silver sintered body/silver-plated copper lead frame was confirmed. Platinum was evaporated onto the ground sample by an ion sputtering apparatus (manufactured by Hitachi Advanced Technology Co., Ltd., model: E1045), and this was fabricated by a desktop scanning electron microscope (Japan Electronics Co., Ltd., model number). : NeoScope JCM-5000), observed at an electron acceleration voltage of 10 kV and a magnification of 5000 times, and taken an SEM photograph.

(Example 1)

The silver nanoparticles are synthesized according to the following steps. Using silver oxide (manufactured by Wako Pure Chemical Co., Ltd.) as a source of silver, diethylene glycol (manufactured by Wako Pure Chemical Co., Ltd., boiling point 244 ° C) as a reducing agent, N,N-dimethylethylenediamine (Tokyo Huacheng Co., Ltd., boiling point 107 ° C) as a protective agent for silver nanoparticles. These reagents were added to the eggplant type flask according to the formulation ratio shown in Table 1. The reaction solution was heated and refluxed at 110 ° C for 3 hours while stirring at about 700 rpm by a magnetic stirrer. About 300 ml of acetone was added to the solution after the reaction, and the supernatant was removed, and the precipitated silver nanoparticles were recovered. This silver nanoparticle was heated at 40 ° C for 3 hours to be dried. By performing XRD measurement of the silver nanoparticle, an XRD pattern as shown in Fig. 6 was obtained, and it was confirmed It is metal silver. Further, it was confirmed that the silver nanoparticles were spherical, and the particle diameter of the silver nanoparticles was 50 to 200 nm (Fig. 7). The TG-DTA measurement of this silver nanoparticle was carried out, and the graph of Fig. 1 was obtained. From this, it is understood that the N,N-dimethylethylenediamine coated on the surface of the silver nanoparticles is detached at about 225 °C.

On the other hand, AgC239 (manufactured by Fukuda Metal Foil Co., Ltd.) was used as the silver microparticles. The treatment for coating AgC239 with a protective agent, that is, dodecanoic acid, was carried out as follows. In other words, first, 100 g of AgC239, 10 g of dodecanoic acid (manufactured by Wako Pure Chemical Co., Ltd., boiling point: 299 ° C), and 1-propanol (manufactured by Wako Pure Chemical Co., Ltd., boiling point: 97 ° C), 500 mL, respectively, were added to the eggplant type. In the flask, and as a reaction solution. The reaction solution was heated while stirring at about 200 rpm by a magnetic stirrer, and heated at 60 ° C for 3 hours to cause a reaction. Excess dodecanoic acid was removed by repeating the following operations three times and AgC239 coated with dodecanoic acid was recovered: for the solution after the reaction, after adding about 1000 ml of acetone, the supernatant was removed. This was heated at 40 ° C for 3 hours to serve as an evaluation sample.

The TG-DTA measurement of AgC239 coated with dodecanoic acid was carried out, and the graph of Fig. 2 was obtained. From this, it is understood that the dodecanoic acid coated with the silver microparticles will be detached at about 250 °C. Further, it has been confirmed that the silver microparticles have a plate shape, and the silver microparticles have a particle diameter of 2 to 10 μm.

As terpineol (manufactured by Wako Pure Chemical Industries, a mixture of isomers, a boiling point of about 217 ° C), stearic acid (manufactured by Shin Nippon Chemical Co., Ltd.) was used as an additive. Silver nanoparticle, silver microparticles, solvent, and additives were kneaded by a kneading machine for 15 minutes according to the blending ratio shown in Table 2 to prepare a silver paste. The TG-DTA measurement of this silver paste was performed, and the chart of FIG. 3 was obtained. Know The detachment of the organic matter contained in the gel ends at about 250 °C. The characteristics of this silver paste are shown in Table 3. The SEM photograph of the cross section of the gold-plated tantalum wafer and the silver sintered body in the gold-plated tantalum wafer/silver sintered body/silver-plated copper lead frame produced in the above (7) is taken as an SEM photograph as shown in FIG. Shown.

(Example 2)

N-methylbutylamine (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 91 ° C) was used as a protective agent for silver nanoparticles, and silver nanoparticles were synthesized in the same manner as in Example 1. Using this silver nanoparticle, a silver paste was prepared in the same procedure as in Example 1. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, it has been confirmed that the silver nanoparticles are spherical, and the particle diameter of the silver nanoparticles is 50 to 200 nm.

(Example 3)

Silver nanoparticle was synthesized by the same procedure as in Example 1 using 1,2-dimethylpropylamine (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 86 ° C) as a protective agent for silver nanoparticles. Using this silver nanoparticle, a silver paste was prepared in the same procedure as in Example 1. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, it has been confirmed that the silver nanoparticles are spherical, and the particle diameter of the silver nanoparticles is 200 to 250 nm.

(Example 4)

As a protective agent for silver nanoparticles, triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point: 89.7 ° C) was used, and silver nanoparticles were synthesized in the same manner as in Example 1. Using this silver nanoparticle, a silver paste was prepared in the same procedure as in Example 1. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Also, it has been confirmed that the silver nanoparticles are spherical and silver nanoparticles The particle size of the particles is 35 to 100 nm.

(Example 5)

Silver acetate particles were synthesized using the same procedure as in Example 1 using acetic acid (manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 118 ° C) as a protective agent for silver nanoparticles. Using this silver nanoparticle, a silver paste was prepared in the same procedure as in Example 1. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, it has been confirmed that the silver nanoparticles are spherical, and the silver nanoparticles have a particle diameter of 100 to 280 nm.

(Comparative Example 1)

Silver nitrate particles were synthesized in the same manner as in Example 1 using diethanolamine (manufactured by Wako Pure Chemical Co., Ltd., boiling point: 217 ° C) as a protective agent for silver nanoparticles. The TG-DTA measurement of the silver nanoparticles was carried out, and the graph of Fig. 9 was obtained. From this, it was found that diethanolamine was detached from the surface of the silver nanoparticles at about 335 °C. Using this silver nanoparticle, a silver paste was prepared in the same procedure as in Example 1. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, it has been confirmed that the silver nanoparticles are spherical, and the silver nanoparticles have a particle diameter of 100 to 280 nm. Further, an SEM photograph obtained by photographing a cross section of a portion of a gold-plated tantalum wafer/silver sintered body/silver-plated copper lead frame produced in the above (7) and a silver sintered body is obtained. Figure 10 shows. In the silver sintered body of Comparative Example 1, the silver nanoparticle protective agent has a high desorption temperature, and therefore is not completely sintered at 200 ° C, but the density, grain shear strength, volume resistivity, and bulk resistivity of the silver sintered body. Also, the thermal conductivity was inferior to the silver sintered body of Example 1.

(Comparative Example 2)

Silver nanoparticles were synthesized in the same manner as in Example 1. Using this silver nanoparticle, a silver paste was prepared in the same manner as in Example 1 so that silver microparticles were not added. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, an SEM photograph obtained by photographing a cross section of a portion of a gold-plated tantalum wafer/silver sintered body/silver-plated copper lead frame produced in the above (7) and a silver sintered body is obtained. Figure 11 shows. It has been observed that the volume shrinkage when the silver nanoparticles are sintered is large, and the sintered body is peeled off from the gold-plated tantalum wafer.

(Comparative Example 3)

A silver paste was produced in the same manner as in Example 1 except that silver microparticles were not used, and silver nanoparticle was used. The formulation of the silver paste is as described in Table 2. The characteristics of this silver paste are shown in Table 3. Further, an SEM photograph obtained by photographing a cross section of a portion of a gold-plated tantalum wafer/silver sintered body/silver-plated copper lead frame produced in the above (7) and a silver sintered body is obtained. Figure 12 shows. The properties of the silver sintered body of Comparative Example 3 were also inferior to those of the silver sintered body of Example 1.

Claims (8)

A silver paste comprising silver particles and a solvent, wherein the silver particles comprise: silver particles having a particle diameter of 1 μm to 20 μm; and silver particles having a particle diameter of 1 nm to 300 nm, which are coated with a boiling point at atmospheric pressure A protective agent of less than 130 °C. The silver paste according to claim 1, further comprising: a carboxylic acid having a boiling point of 400 ° C or less at atmospheric pressure and being solid at normal temperature. The silver paste according to claim 1 or 2, wherein the protective agent is at least 1 selected from the group consisting of an amine compound, a carboxylic acid compound, an amino acid compound, an amino alcohol compound, and a guanamine compound. Kind. The silver paste according to any one of claims 1 to 3, wherein the protective agent is selected from the group consisting of 1-aminopentane, 2-aminopentane, 3-aminopentane, 2-methyl Butylamine, 3-methylbutylamine, 1,2-dimethylpropylamine, 2,2-dimethylpropylamine, N-methylbutylamine, N-methylisobutylamine ,ethylpropylamine, piperidine, methylpropylamine, diethylamine, fluolin, triethylamine, N,N-diethylmethylamine, N,N-dimethylisopropyl Amine, N,N,N'-trimethylethylenediamine, N,N-dimethylethylenediamine, 1,2-bis(methylamino)ethane, 1,2-diaminopropane, At least one of the group consisting of N-methylethylenediamine, 1,2-diaminoethane, and acetic acid. The silver paste according to any one of claims 1 to 4, wherein the surface of the silver particles having a particle diameter of 1 μm to 20 μm is coated with an aliphatic monocarboxylic acid having 2 to 20 carbon atoms. The silver paste according to any one of claims 1 to 5, wherein the silver particles having a particle diameter of from 1 μm to 20 μm are plate-like silver particles or a mixture of plate-like silver particles and spherical silver particles. A semiconductor device having a structure in which a semiconductor element and a support member for mounting a semiconductor element are adhered to each other by a sintered body obtained by sintering the silver paste according to any one of claims 1 to 6. A method for producing a silver paste by mixing silver particles and a solvent to obtain a silver paste, wherein silver particles having a particle diameter of 1 μm to 20 μm are used as the silver particles; and silver having a particle diameter of 1 nm to 300 nm The particles are coated with a protective agent having a boiling point of less than 130 ° C at atmospheric pressure.