JP6343041B2 - Thermally conductive paste and use thereof - Google Patents

Description

  The present invention relates to a heat conductive paste, and more particularly to a heat conductive paste for die attach or bump formation of a semiconductor device. The present invention also relates to a semiconductor device using the thermally conductive paste for joining components.

  A paste containing silver fine particles forms a conductive silver film by sintering silver fine particles by heating, and is used to form conductive circuits on a printed circuit board, capacitor electrodes, and the like (Patent Document 1). reference). In recent years, it is also used to form bonding members in semiconductor devices such as bumps and die attach materials.

  The above silver film has a porous structure in which a large number of silver fine particles are sintered and connected to each other, so that it is brittle and inferior in mechanical strength. Further, the silver film easily deteriorates due to the ingress of moisture and the like. There was also a problem that it was inferior in terms of sex. In order to solve these problems, a method has been proposed in which silver fine particles are sintered together and then impregnated with a curable liquid resin composition in a porous structure and cured (see Patent Documents 2 and 3). .

JP 2006-183072 A JP 2010-65277 A JP 2010-171271 A

  However, the step of impregnating the curable liquid resin composition is complicated, and there is a problem particularly from the viewpoint of application to a joining member of a semiconductor device.

  The inventors of the present invention have studied to obtain a silver film with improved mechanical strength and reliability using a heat conductive paste containing silver fine particles by a simpler method. By using a heat conductive paste containing a binder, a silver film with improved mechanical strength can be obtained only by heat treatment, and this silver film is also excellent in terms of electrical conductivity and heat conductivity. And the present invention has been completed.

The present invention [1] includes low-temperature sinterable silver fine particles; and a thermosetting binder,
It is related with the heat conductive paste whose thermosetting binder is 2-7 mass parts with respect to 100 mass parts of silver fine particles.
In the present invention [2], the low temperature sinterable silver fine particles are silver fine particles having an average particle diameter of 1 to 500 nm, and a coating film made of a paste in which silver fine particles are dispersed at a concentration of 90% by mass in an organic medium, When heated at 200 ° C. for 1 hour, in the coated film after heating, the silver fine particles are fused with each other, and the coated film after heating has a specific resistance of 10 μΩ · cm or less and a thermal conductivity of 70 W / mK or more. The present invention relates to a heat conductive paste of the present invention [1].
In the present invention [3], when thermogravimetric analysis is performed from 25 ° C. or less at a heating rate of 10 ° C./min, the weight loss from 25 ° C. to 500 ° C. is expressed as ΔW _{25 ° C. → 500 °} C. When the weight loss up to ΔW _{25 ° C → 500 ° C} ,
ΔW _{25 ° C → 500 ° C} ≧ 1%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} ≦ 0.7%
A silver fine particle having an average particle diameter of 1 to 500 nm; and a thermosetting binder,
The heat conductive paste whose thermosetting binder is 2-7 mass parts with respect to 100 mass parts of silver fine particles.
The present invention [4] comprises silver fine particles having an average particle diameter of 40 to 350 nm, a crystallite diameter of 20 to 70 nm, and a ratio of the average particle diameter to the crystallite diameter of 1 to 5; and a thermosetting binder,
It is related with the heat conductive paste whose thermosetting binder is 2-7 mass parts with respect to 100 mass parts of silver fine particles.
The heat conductive paste according to any one of the present invention [1] to [4], wherein the thermosetting binder comprises (B1) an epoxy resin and / or an oxetane resin, and (B2) a curing agent. About.
This invention [6] relates to the heat conductive paste of this invention [5] whose (B1) is an epoxy resin containing an ester bond.
The present invention [7] relates to the thermally conductive paste of the present invention [5], wherein (B1) is an oxetane resin.
This invention [8] relates to the heat conductive paste of this invention [6] whose epoxy resin containing an ester bond is diglycidyl phthalate and / or its derivative (s).
The present invention [9] is any one of the present invention [5] to [8], wherein (B2) is a curing agent selected from the group consisting of a cationic polymerization initiator, an amine curing agent and an acid anhydride curing agent. It relates to such a heat conductive paste.
The present invention [10] relates to the thermally conductive paste of the present invention [9], wherein (B2) is a cationic polymerization initiator.
The present invention [11] relates to the thermal conductive paste according to any one of the present invention [1] to [10] for die attach of a semiconductor device.
The present invention [12] relates to the thermal conductive paste according to any one of the present invention [1] to [10] for bump formation of a semiconductor device.
The present invention [13] relates to a semiconductor device using the thermally conductive paste of any one of the present invention [1] to [12] for joining parts.

  According to the heat conductive paste of the present invention, a silver film having improved mechanical strength and reliability can be obtained without using a special technique such as an impregnation process. In addition, this silver film is excellent in terms of electrical conductivity and thermal conductivity, and is suitable as a bonding member in semiconductor devices such as bumps and die attach materials. Furthermore, when using a paste containing conventional silver fine particles as a bonding member, in order to obtain sufficient bonding strength, heat treatment and pressure treatment are generally used in combination, but according to the heat conductive paste of the present invention. Only by heat treatment, sufficient bonding strength can be obtained and convenience is high.

It is the shape of the sample of the fatigue test in an Example. 2 is a TG chart of silver fine particles A to C in Examples. It is a DTA chart of silver fine particles A to C in Examples. It is a photograph of the coating film before and behind heating at 200 degreeC about silver fine particles AC in an Example for 1 hour. It is the result of cross-sectional observation of the silver film of the comparative example 1, Examples 1-5, and the comparative example 2. FIG. It is a result of the fatigue test of a silver film about the comparative example 1 and Example 3. FIG. It is a result of the cross-sectional observation of the junction part of Example 3. It is a result of cross-sectional observation of the silver film of Example 6 and Reference Examples 1 to 4 . It is a result of cross-sectional observation of the silver film of Examples 6 , 11 , 12 and Reference Example 5 .

  The thermally conductive paste of the present invention contains silver fine particles and a thermosetting binder. In the first embodiment of the present invention, the silver fine particles are low-temperature sinterable silver fine particles.

  In the present specification, the low-temperature sinterable silver fine particles are silver fine particles that can be sintered at 120 to 300 ° C. Specifically, as a low-temperature sinterable silver fine particle, a silver fine particle having an average particle diameter of 1 to 500 nm, and a coating film made of a paste in which silver fine particles are dispersed in an organic medium is heated at 200 ° C. for 1 hour. In the coating film after heating, silver particles can be used in which the silver particles are fused with each other, the coating film after heating exhibits a specific resistance of 10 μΩ · cm or less, and a thermal conductivity of 70 W / mK or more. In the above paste, the organic medium is not particularly limited as long as it is an organic medium that is liquid at room temperature (25 ° C.) and volatilizes when heated to 200 ° C. For example, benzyl alcohol, terpineol, or the like can be used. However, benzyl alcohol is preferred from the viewpoint of handleability. The density | concentration of the said paste is not specifically limited, From the point of formation of a coating film, it can be set as the density | concentration of 85-95 mass%, for example, can be 90 mass%. The said coating film can be obtained by apply | coating a paste on a base material. The thickness of the coating film is not particularly limited, and can be, for example, 1 to 2 mm. Regarding the fusion of silver fine particles in the coating film after heating, the particles are fused when the coating film cross section is observed, and the shape of the particles before heating cannot be confirmed, so that the fusion can be confirmed.

  In the present specification, the average particle diameter refers to an average particle diameter based on the number standard by laser diffraction scattering type particle size distribution measurement.

Further, in the second aspect of the present invention, fine silver particles, when subjected to thermogravimetric analysis at a heating rate 10 ° C. / min from 25 ° C. or less, [Delta] W _{25 ° C.} The weight loss up to 500 ° C. from 25 ° C. _{→ When} the weight loss from _{500 ° C.} and 25 ° C. to 200 ° C. is ΔW _{25 ° C. → 200 ° C.} ,
ΔW _{25 ° C → 500 ° C} ≧ 1%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} ≦ 0.7%
These are silver fine particles having an average particle diameter of 1 to 500 nm.

In this embodiment, ΔW _{25 ° C. → 500 ° C.} of the silver fine particles is 1% or more, and can be 3% or more. Specifically, it can be 1 to 30%, for example, 3 to 30%. In the case where the silver fine particles are dispersed in an organic medium, this form can be subjected to thermogravimetric analysis. In this case, the upper limit may vary depending on the amount of organic medium, and ΔW _{25 ° C. → 500 ° C.} may exceed 30%. The organic medium is liquid at room temperature (25 ° C.) and can be an organic medium that volatilizes when heated to 200 ° C. Examples include, but are not limited to, benzyl alcohol, terpineol, dihydroterpineol, and the like. Not. ΔW _{25 ° C. → 500 ° C.} is preferable from the viewpoint of ensuring dispersion stability and capable of suppressing the occurrence of voids and the like in the silver film when the surface of silver is easily exposed when using the heat conductive paste. Is 1-20%, More preferably, it is 3-20%, More preferably, it is 5-15%.
Here, ΔW _{25 ° C. → 500 ° C.} means that when the weight at 25 ° C. in the thermogravimetric analysis is W _{25 °} C. and the weight at _{500 ° C.} is W _{500 ° C.} ,
ΔW _{25 ° C. → 500 ° C.} = (W _{25 ° C.−} W _{500 ° C.} ) / W _{25 ° C.} × 100.
In addition, ΔW _{25 ° C. → 200 ° C.} is a case where the weight at 25 ° C. in the thermogravimetric analysis is W _{25 °} C. and the weight at _{200 ° C.} is W _{200 ° C.}
ΔW _{25 ° C. → 200 ° C.} = (W _{25 ° C.−} W _{200 ° C.} ) / W _{25 ° C.} × 100.

Furthermore, ΔW _{25 ° C. → 500 ° C.−} ΔW _{25 ° C. → 200 ° C. of} the silver fine particles is 0.7% or less. From the viewpoint of securing the sinterability at a low temperature (for example, 120 to 300 ° C.), it is preferably 0.5% or less, and more preferably 0.3% or less.

  The silver fine particles preferably have an exothermic peak at 180 to 260 ° C., more preferably 210 to 250 ° C., when differential thermal analysis is performed at a heating rate of 10 ° C./min.

  In this specification, thermogravimetric analysis and differential thermal analysis are performed by using a differential thermal / thermogravimetric simultaneous measurement device and raising the temperature from 25 ° C. or lower to 500 ° C. at a temperature rising rate of 10 ° C./min. , By measuring a TG-DTA curve. When the silver fine particles are dispersed in an organic medium, they can be subjected to thermogravimetric analysis and differential thermal analysis in the form of a dispersion.

In the present invention, the silver fine particles can be sintered at a temperature of 200 ° C. or lower, and the weight from 25 ° C. to 500 ° C. when thermogravimetric analysis is performed at a temperature increase rate of 10 ° C./min from 25 ° C. or lower. When the decrease is ΔW _{25 ° C. → 500 °} C. and the weight decrease from 25 ° C. to 200 ° C. is ΔW _{25 ° C. → 200 ° C.} ,
ΔW _{25 ° C → 500 ° C} ≧ 1%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} ≦ 0.7%
May be satisfied, and it is preferable that they are satisfied.

  Here, the silver fine particles have an average particle diameter of 1 to 500 nm, but from the viewpoint of low temperature sinterability and dispersion stability, the average particle diameter is preferably 40 to 350 nm, and more preferably 80 to 150 nm.

  As the silver fine particles, silver fine particles coated or treated with an organic substance, or silver fine particles dispersed in an organic medium can be used. Examples of silver fine particles dispersed in an organic medium include silver fine particles reduced and precipitated in the presence of an organic substance. From the viewpoint of preventing aggregation of silver fine particles and preparing a heat conductive paste, silver fine particles dispersed in an organic medium can be preferably used. It is understood that an organic substance is attached to the surface of such silver fine particles, and the organic substance is volatilized and thermally decomposed by heating, so that the weight of the silver fine particles can be changed.

  As such silver fine particles, silver fine particles obtained by allowing a primary amine to act on a silver salt of a carboxylic acid and then precipitated by a reduction reaction, or silver fine particles coated or treated with an organic substance can be used. Examples of the former include silver fine particles disclosed in JP-A-2006-183072, JP-A-2011-153362, and the like, and examples of the latter include JP-A-2009-289745, JP-A-2010-65277, and the like. The silver fine particles disclosed in (1) are exemplified. Silver fine particles are nano-order, have a large total surface area per unit weight, high surface energy, good sinterability in the first place, and organic substances on the surface volatilize when using a heat conductive paste. -The silver surface is exposed due to thermal decomposition and elution into the solvent, and the silver fine particles come into direct contact with each other, so that sintering is likely to proceed.

  Specifically, the silver fine particles can be produced by mixing a silver salt of a carboxylic acid and an aliphatic primary amine, then adding a reducing agent and precipitating at a reaction temperature of 20 to 80 ° C. .

  The silver salt of the carboxylic acid is not particularly limited, but a silver salt of an aliphatic monocarboxylic acid is preferable, silver acetate, silver propionate or silver butyrate is more preferable, and silver acetate is particularly preferable. The aliphatic primary amine is not particularly limited and may be a monoamine compound or a polyamine compound such as a diamine compound. The aliphatic primary amine has an aliphatic hydrocarbon group, a hydroxyl group, and the like. , A group substituted with an alkoxy group such as a methoxy group, an ethoxy group and a propyl group, more preferably 3-methoxypropylamine, 3-aminopropanol and 1,2-diaminocyclohexane.

  The amount of the aliphatic primary amine used is preferably 1 equivalent or more, preferably 1.0 to 3.0 equivalents, more preferably 1 equivalent to 1 equivalent of the silver salt of carboxylic acid. It is 0-1.5 equivalent, Most preferably, it is 1.0-1.1 equivalent.

  The mixing of the silver salt of the carboxylic acid and the aliphatic primary amine can be carried out in the absence or presence of an organic solvent. From the viewpoint of ease of mixing, the mixing may be in the presence of an organic solvent. Preferably, examples of the organic solvent include alcohols such as ethanol, propanol, and butanol, ethers such as propylene glycol dibutyl ether, and aromatic hydrocarbons such as toluene. The mixing of the silver salt of the carboxylate and the aliphatic primary amine is performed, for example, by stirring the silver salt of the carboxylic acid while stirring the primary aliphatic amine or the mixture of the primary aliphatic amine and the organic solvent. It can be performed by adding. Stirring can be continued as appropriate even after the end of the addition. In the meantime, it is preferable to maintain temperature at 20-80 degreeC, More preferably, it is 20-60 degreeC.

  Thereafter, a reducing agent is added to precipitate silver fine particles. As the reducing agent, formic acid, formaldehyde, ascorbic acid or hydrazine is preferable from the viewpoint of controlling the reaction, and formic acid is more preferable. The amount of the reducing agent used is usually at least a redox equivalent with respect to the silver salt of the carboxylic acid, and the redox equivalent is preferably 0.5 to 5 times, more preferably 1 to 3 times. . When the silver salt of carboxylic acid is a silver salt of monocarboxylic acid and formic acid is used as the reducing agent, the amount of formic acid used in terms of mole is 0.5 to 1 with respect to 1 mole of silver salt of carboxylic acid. 0.5 mol is preferable, more preferably 0.5 to 1.0 mol, and still more preferably 0.5 to 0.75 mol.

  In the addition of the reducing agent and the subsequent reaction, the temperature is maintained between 20 ° C and 80 ° C. It is preferable that temperature is 20-70 degreeC, More preferably, it is 20-60 degreeC. In the addition of the reducing agent and the subsequent reaction, an organic solvent such as an alcohol such as ethanol, propanol or butanol, an ether such as propylene glycol dibutyl ether, or an aromatic hydrocarbon such as toluene is added as necessary. be able to.

  Silver fine particles precipitated by the reaction can be allowed to settle and the supernatant can be removed by decantation or the like, or a solvent such as alcohol such as methanol, ethanol or the like can be added for fractionation. The solution in which the silver fine particles are precipitated can be directly blended with the heat conductive paste of the present invention. After any of the above steps, terpineol, dihydroterpineol, benzyl alcohol, 2-phenylethyl alcohol, butyl carbitol, butyl carbitol acetate, 2-ethyl-1,3-hexane for dispersion stability of the silver fine particles Solvents such as diol and texanol can also be added.

  Alternatively, silver fine particles can be obtained by coating silver fine particles produced by a reduction method, a pulverization method, an electrolysis method, an atomization method, a heat treatment method, or a combination thereof with an organic substance. From the viewpoint of low-temperature sinterability, it is preferable to coat silver fine particles produced by a reduction method with an organic substance.

  Examples of organic substances include high and intermediate fatty acids and derivatives thereof. Examples of the derivatives include high / intermediate fatty acid metal salts, high / intermediate fatty acid amides, high / intermediate fatty acid esters, and high / intermediate alkylamines. Of these, high and intermediate fatty acids are preferred.

  The higher fatty acid is a fatty acid having 15 or more carbon atoms, such as pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid (stearic acid), 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), eicosanoic acid ( Linear saturated fatty acids such as arachidic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), hexacosanoic acid (serotic acid), octacosanoic acid (montanic acid); 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2- Branched saturated fatty acids such as heptyldodecanoic acid and isostearic acid; unsaturated fatty acids such as palmitoleic acid, oleic acid, isooleic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid, gadrenic acid, erucic acid, and ceracoleic acid The

  Intermediate fatty acids are fatty acids having 6 to 14 carbon atoms, such as hexanoic acid (caproic acid), heptanoic acid, octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), undecanoic acid, Linear saturated fatty acids such as dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid); isohexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, 2-propylheptanoic acid, isodecanoic acid, Illustrative examples include branched saturated fatty acids such as isoundecanoic acid, 2-butyloctanoic acid, isododecanoic acid and isotridecanoic acid; and unsaturated fatty acids such as 10-undecenoic acid.

  It is also possible to use silver fine particles coated with higher fatty acids and derivatives thereof substituted with lower fatty acids.

  From the viewpoint of the sinterability and dispersion stability of silver fine particles, silver fine particles coated with a fatty acid having 12 to 18 carbon atoms are preferred.

  Further, the silver fine particles have an average particle diameter of 40 to 350 nm, a crystallite diameter of 20 to 70 nm, and a ratio of the average particle diameter to the crystallite diameter (average particle diameter / crystallite diameter) of 1 to 5. Certain silver particulates can be used. The average particle diameter is preferably 40 to 100 nm, more preferably 50 to 80 nm, the crystallite diameter is preferably 20 to 50 nm, and the ratio of the average particle diameter to the crystallite diameter is preferably 1 to 4, more preferably in the range of 1-3. In this specification, the crystallite diameter is calculated from the Scherrer equation by obtaining the half width of the plane index (1,1,1) plane peak from the powder X-ray diffraction method using Cu Kα ray as the radiation source. The results of

  In the present invention, the silver fine particles may be used alone or in combination of two or more.

  The present invention includes a thermosetting binder. The thermosetting binder is not particularly limited, and may include a thermosetting resin. For example, it may be a combination of (B1) an epoxy resin and / or an oxetane resin, and (B2) a curing agent.

  (B1) As the epoxy resin and / or oxetane resin, an epoxy resin is preferable.

  Among them, an epoxy resin containing an ester bond is preferable. The epoxy resin containing an ester bond is not particularly limited as long as it is an epoxy resin containing one or more ester bonds in the molecule. The number of ester bonds in the molecule is preferably two from the viewpoint of not inhibiting the sintering of the silver fine particles.

For example, the formulas (1) to (4):

(Wherein R ^{1 s} are each independently hydrogen or a methyl group;
Each R ³ is independently a C1-C4 alkyl group;
n is 0, 1, 2, 3 or 4)
The diglycidyl ester shown by these is mentioned.

Among them, formulas (1 ′) to (4 ′):

(Wherein R ^{1 s} are each independently hydrogen or a methyl group;
Each R ₃ is independently a C1-C4 alkyl group;
n is 0, 1, 2, 3 or 4)
Diglycidyl phthalate and derivatives thereof represented by
In the formulas (1) to (4) and (1 ′) to (4 ′), preferably R ₁ is hydrogen and n is 0 or R ₁ is hydrogen and n is 1. R ₃ is a methyl group.

The epoxy resin containing an ester bond may be an alicyclic epoxy resin, for example, the formulas (5) to (6):

The alicyclic epoxy resin shown by these is mentioned.

  As the epoxy resin, bisphenol F type epoxy resin, bisphenol A type epoxy resin, novolac type epoxy resin, glycidylamine type epoxy resin, 1,4-bis (glycidyloxymethyl) cyclohexane, neodecanoic acid glycidyl ester and the like can also be used. . These epoxy resins may be used in combination with an epoxy resin containing an ester bond. When using together with the epoxy resin containing an ester bond, it is more preferable to use it at 50 mass parts or less with respect to 100 mass parts of the epoxy resin containing an ester bond.

The oxetane resin is not particularly limited as long as it is a resin containing an oxetane ring in the molecule. For example, the formula:

(Where n is a number from 1 to 3)
The oxetane resin shown by these is mentioned.

  (B1) The epoxy resin and / or oxetane resin may be used alone or in combination of two or more. Two or more epoxy resins may be combined, an epoxy resin and an oxetane resin may be combined, or two or more oxetane resins may be combined.

  Among these, since fusion between silver fine particles proceeds and good thermal conductivity is obtained, diglycidyl phthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, and C1 to C4 thereof. Alkyl-substituted products (for example, methyl-substituted products) are preferable, and among them, hexahydrophthalic acid diglycidyl ester is preferable.

(B2) Curing agent The curing agent of (B2) is not particularly limited as long as it cures (B1) an epoxy resin and / or an oxetane resin. For example, a cationic polymerization initiator, an amine-based curing agent, and an acid anhydride Product curing agents and phenolic curing agents can be used, among which cationic polymerization initiators, amine-based curing agents, and acid anhydride curing agents are preferred.

  Examples of the cationic polymerization initiator include Lewis acid salts, onium salts, fatty acid metals, etc. Among them, onium salts are preferable.

The onium salt is, for example, the formula (7):

And / or formula (8):

(Where
R ₁₇ is an unsubstituted or substituted monovalent hydrocarbon group, each of which may be the same or different,
E ¹ is an iodine atom, a sulfur atom, a nitrogen atom, a phosphorus atom, a diazo group or an unsubstituted or ring-substituted pyridinio group;
E ² is a sulfur atom or a nitrogen atom,
Z is a counter ion that is BF ₄ , PF ₆ , AsF ₆ , SbF ₆ or (C ₆ F ₅ ) ₄ B;
a is 2 when E ¹ is an iodine atom, 3 when a sulfur atom, 4 when a nitrogen atom or a phosphorus atom, 1 when a diazo group or an unsubstituted or ring-substituted pyridinio group,
b is 1 when E ² is a sulfur atom, 2 when it is a nitrogen atom, and c is an integer of 4 or 5, and the iodonium salt, sulfonium salt, ammonium salt, phosphonium salt, diazonium salt or pyridinium salt Is mentioned. These may be used alone or in combination of two or more.

In the formulas (7) and (8), R ₁₇ is specifically an alkyl group having 1 to 15 carbon atoms such as methyl or ethyl; a cycloalkyl group having 3 to 10 carbon atoms such as cyclohexyl; phenyl, Aryl groups such as 4-tolyl, 2,4-xylyl and 1-naphthyl; aralkyl groups such as benzyl, 2- or 4-methylbenzyl and 2-phenylethyl; alkenyl groups having 2 to 10 carbon atoms such as vinyl and allyl And 4-hydroxyphenyl, 4-methoxyphenyl, 4-cyanophenyl, 4-chlorophenyl, 4-acetoxyphenyl, 4-propanoylphenyl, 4-methoxycarbonylphenyl, 4-ethoxycarbonylphenyl, 4-methoxybenzyl, 4; -Ethoxybenzyl, 4-t-butoxybenzyl, 4-nitrobenzyl, 4-cyanobenzyl, etc. Serial-substituted monovalent hydrocarbon group derived from a hydrocarbon group and the like. Among them, because they exhibit excellent curability, it is preferable that at least one R ₁₇ in a molecule is an aryl group or an aralkyl group, it is more preferred that all of R ₁₇ is such a group.

E ¹ or E ² is preferably an iodine atom or a sulfur atom because an excellent curing rate can be obtained.

Specific examples of the unsubstituted or ring-substituted pyridinio group for E ¹ include pyridinio, 2- or 4-methylpyridinio, 2,4-dimethylpyridinio, 2- or 4-cyanopyridinio, 2- or 4-methoxy. Examples include ring-substituted pyridinium groups such as carbonylpyridinio, 2- or 4-ethoxycarbonylpyridinio.

Z shows excellent curability when heated for a short time, so SbF ₆ or B (C ₆ F ₅ ) ₄ is preferable, does not show toxicity, and does not need to consider the effects on hygiene and the environment Therefore, B (C ₆ F ₅ ) ₄ is particularly preferable.

  Examples of such preferable onium salts include diaryliodonium such as diphenyliodonium; substituted aryl group-containing iodonium such as phenyl (4-methoxyphenyl) iodonium; aralkyl group-containing iodonium such as phenylbenzyliodonium; triphenylsulfonium, diphenyl (4- triarylsulfonium such as t-butylphenyl) sulfonium; substituted aryl group-containing sulfonium such as tris (4-hydroxyphenyl) sulfonium, tris (4-methoxyphenyl) sulfonium, tris (acetoxyphenyl) sulfonium; methyl (4-hydroxyphenyl) ) Hexafluoro such as benzyl structure-containing sulfonium such as benzylsulfonium and methyl (4-methoxyphenyl) -1-naphthylmethylsulfonium Oro antimonate and tetrakis (pentafluorophenyl) boron salts. Tetrakis (pentafluorophenyl) boron salt is preferable from the viewpoint of hygiene and environmental conservation, and an appropriate curing rate can be obtained. Particularly, 4-methylphenyl [4- (1-methylethyl) phenyl] iodonium tetrakis (pentafluorophenyl) Particularly preferred are diaryliodonium tetrakis (pentafluorophenyl) boron salts such as boron salts.

  Fatty acid metals can also be preferably used as the cationic polymerization initiator. Specific examples include metal octoate and metal naphthenate. Specific examples include ferric octoate, cobalt octoate, tin octoate, calcium octoate, zinc octoate, copper octoate, and octane. Examples thereof include zirconium acid, magnesium octoate, and naphthenate salts corresponding thereto.

  The amine curing agent is not particularly limited, and examples thereof include aliphatic polyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, trimethylhexamethylenediamine, m-xylenediamine, and 2-methylpentamethylenediamine, and isophoronediamine. 1,3-bisaminomethylcyclohexane, bis (4-aminocyclohexyl) methane, norbornenediamine, 1,2-diaminocyclohexane and other alicyclic polyamines, N-aminoethylpiperazine, 1,4-bis (2-amino) 2-methylpropyl) piperazine-type polyamines such as piperazine, diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, diethyltoluenediamine, trimethylenebis (4-aminobenzoate) Polytetramethylene oxide - aromatic and di -p- aminobenzoate polyamine, and the like.

  The amine curing agent includes an imidazole curing agent. The imidazole curing agent is not particularly limited, and 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2 -Phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecyl imidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2 , 4-Diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s -Triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6 -[2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethyli Dazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6- Examples include methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, and epoxy-phenol-borate ester blend.

  The acid anhydride-based curing agent is not particularly limited, but phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bistrimellitate, glycerol tris trimellitate, maleic anhydride, tetrahydro Phthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride Succinic anhydride, methylcyclohexene dicarboxylic acid anhydride, alkylstyrene-maleic anhydride copolymer, chlorendic acid anhydride, and polyazeline acid anhydride.

  (B2) As the curing agent, cationic polymerization initiators are preferable from the viewpoint that fusion between silver fine particles proceeds and good thermal conductivity is obtained, and among them, iodonium salt-based acid generators are preferable.

  (B2) A hardening | curing agent may be individual, or may use 2 or more types together.

  In the thermally conductive paste of the present invention, the thermosetting binder is 2 to 7 parts by mass, preferably 2.5 to 6 parts by mass with respect to 100 parts by mass of the silver fine particles, from the viewpoint of low-temperature sinterability. Yes, more preferably 3 to 5.5 parts by mass. When the silver fine particles are silver fine particles coated or treated with an organic substance, it can be based on the mass as silver excluding the organic substance, and can be the mass at 500 ° C. in thermogravimetric analysis. Moreover, when using the silver fine particle of the form disperse | distributed in the organic medium as a silver fine particle, a silver conversion amount can be calculated from the silver content rate in a medium, and can be based on this.

When the thermosetting binder is a combination of (B1) epoxy resin and / or oxetane resin and (B2) curing agent, and the curing agent is a cationic polymerization initiator, (B1) On the other hand, it can be 1.5-6.5 mass parts, Preferably, it is 3-5.5 mass parts, (B2) is 0.5-0.5 with respect to (B1) 100 mass parts. It can be 10 mass parts, Preferably, it is 2.5-8 mass parts.
When a hardening | curing agent is an acid anhydride type | system | group and an amine type, (B1) can be 1.5-6 mass parts with respect to 100 mass parts of silver fine particles, Preferably, 1.8-4 masses (B2) can be 20 to 60 parts by mass, preferably 30 to 50 parts by mass with respect to 100 parts by mass of (B1).

  The thermosetting binder can include a thermosetting resin other than an epoxy resin and an oxetane resin, and examples thereof include a thermosetting phenol resin, a urethane resin, and an acrylic resin.

  The heat conductive paste of this invention can contain a thermal radical production | generation agent in the range which does not impair the effect of this invention. Thermal radical generators include benzopinacol and its derivatives (for example, 1,2-bis (2-methylphenyl) -benzopinacol, 1,2-bis (2-ethylphenyl) -benzopinacol, 1,2-bis (2-fluorophenyl) -benzopinacol, 1,2-bis (2,6-difluorophenyl) benzopinacol, etc.), peroxides (for example, 1,1,3,3-tetramethylbutylperoxy-2- Ethylhexanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di (3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 2,5-dimethyl-2,5- Di (ethylhexanoylperoxy) hexane, etc.).

  The heat conductive paste of the present invention is a curing accelerator (for example, heterocyclic compounds imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, triphenyl, etc., as long as the effects of the present invention are not impaired. Phosphorus compounds such as phosphine and tetraphenylphosphonium tetraphenylborate, tertiary amines such as 2,4,6-tris (dimethylaminomethyl) phenol and benzyldimethylamine, 1,8-diazabicyclo (5,4,0 ) BDUs such as undecene and its salts, amines, imidazoles adduct type adducts adducted with epoxy, urea, acid, etc.), dispersing agents (eg, DISPERBYK101, DISPERBYK102, DISPERBYK103, manufactured by BYK Chemie) DISPERBYK106, DISPERBYK111, DISPERBYK116, DISPERBYK142, DISPERBYK180, DISPERBYK192, DISPERBYK2001, DISPERBYK2020, Enomoto Kasei Di Wetting and dispersing agents such as sperlon PW-36, Disperlon DA-1401, Disperlon DA-550, Disperlon DA-325, Disperlon DA-375, Disperlon DA-234), surfactant (for example, sorbitan monooleate), inorganic filler (For example, silver particles having an average particle diameter of more than 500 nm, such as spherical, elliptical, spindle, granular, substantially cubic, flake, and irregular shapes, and metal whose surface is coated with silver (for example, copper, nickel or (Aluminum) particles, metal particles that can be alloyed with silver, etc.), resin fillers (eg, solid resin particles that are insoluble in a solvent having an average particle size of 0.1 to 50 μm, and a resin whose surface is coated with a metal such as silver) Particles), titanium coupling agents (for example, titanates such as isopropyl triisostearoyl titanate), silane coupling agents, flame retardants, leveling agents, thixotropic agents Defoamers, can contain ion scavenger or the like.

  The heat conductive paste of this invention can contain a solvent from the point of applicability | paintability. Examples of the solvent include organic compounds having a hydroxyl group and a boiling point of 180 to 265 ° C., such as terpineol, dihydroterpineol, benzyl alcohol, 2-phenylethyl alcohol, butyl carbitol, butyl carbitol acetate, 2-ethyl- Examples include 1,3-hexanediol and texanol. Of these, dihydroterpineol, benzyl alcohol, and butyl carbitol acetate are preferable.

  The heat conductive paste of the present invention preferably has a viscosity at 25 ° C. (E-type viscometer, 5 rpm) of 10 to 45 Pa · s, more preferably 15 to 35 Pa · s, and still more preferably. Is 20-30 Pa · s.

  The method for producing the heat conductive paste of the present invention is not particularly limited, and each component is blended in a predetermined composition, a meteor stirrer, a dissolver, a bead mill, a laika machine, a pot mill, a three roll mill, a rotary mixer, two It can be manufactured by mixing in a mixer such as a shaft mixer.

  The heat conductive paste of the present invention forms a silver film by printing or applying to a desired part of a substrate or the like by a conventionally known method such as screen printing and then heating and baking to a predetermined temperature. Can do. The heating temperature of a heat conductive paste can be 120-300 degreeC, Preferably it is 150-250 degreeC, More preferably, it is 180-210 degreeC. The heating time can be appropriately changed depending on the heating temperature, but can be, for example, 15 to 120 minutes, and preferably 30 to 90 minutes. Firing can be performed in the air. As an apparatus for baking, a well-known electric furnace, a ventilation dryer, a belt furnace, etc. are mentioned.

  The silver film obtained by using the heat conductive paste of the present invention has a sufficient mechanical strength, and also has good thermal cycle characteristics and durability, and is excellent in terms of reliability. In addition, the silver film exhibits sufficient conductivity (for example, a specific resistance of 2 to 10 μΩ · cm level) and high thermal conductivity (for example, a thermal conductivity of 50 to 250 W / mK level). Since the silver fine particles contained in the heat conductive paste of the present invention are highly active, the desired characteristics are easily imparted to a silver film obtained by heating the heat conductive paste at 120 to 300 ° C. The thermal conductive paste of the present invention can be used to form conductive circuits on a printed circuit board, capacitor electrodes, etc., taking advantage of the above characteristics, such as between semiconductor device components, substrates and components, etc. It can be used suitably for joining.

  The thermal conductive paste of the present invention is particularly suitable for application as a die attach material for a joining member of a semiconductor device. As a die attach material, lead solder is widely used, but due to the toxicity of lead, restrictions on the use of lead in each country are becoming stricter. The die attach material obtained by using the heat conductive paste of the present invention exhibits a heat conductivity equal to or higher than that of lead (generally 35 to 65 W / mK) and has good conductivity. It can be a high thermal conductivity die attach material that can replace lead solder.

  Furthermore, according to the heat conductive paste of the present invention, it is possible to obtain a strong bonding strength only by heating and without applying pressure in the bonding process. However, pressurization may be performed.

  The heat conductive paste of the present invention is also suitable for application as a bump of a bonding member of a semiconductor device.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

Analysis in the examples was performed as follows.
(1) Measurement of silver fine particles (1-1) Average particle diameter 0.5 g of silver fine particles is added to 50 cc of dispersed water (water containing 0.5% of AEROSOL) and dispersed for 5 minutes by an ultrasonic disperser. The dispersion sample was measured by 3 (LS230) manufactured by Beckman Coulter. Based on the number standard, the average particle size was determined.
(1-2) Crystallite diameter A half of the surface index (1,1,1) plane peak using silver Kα ray as a radiation source by measuring silver fine particles with an X-ray diffractometer (M18XHF22) manufactured by Mac Science. The value range was determined, and the crystallite diameter was calculated from the Scherrer equation.
(1-3) Thermogravimetric analysis / differential thermal analysis 25 using a simultaneous differential thermal / thermogravimetric measuring device (TG-DTA2020SA type manufactured by Bruker AXS Co., Ltd.) at a temperature rising rate of 10 ° C./min in the atmosphere. The temperature was raised from ℃ to 500 ℃ and the TG-DTA curve was measured. Silver fine particles A and B described later are in the form of a silver fine particle-containing paste, and the silver fine particle-containing paste was subjected to thermogravimetric analysis / differential thermal analysis, respectively.
(1-4) Sinterability A paste in which silver fine particles were dispersed was prepared using benzyl alcohol as a medium.
Using the above paste, printing is performed on the substrate by screen printing so that the coating thickness is 1 to 2 mm, and then dried at room temperature (25 ° C.), and then heated at a heating rate of 4.5 ° C./min. When the temperature reached 200 ° C., the sample was further heated for 1 hour while maintaining 200 ° C. to produce a cross-section observation test piece. The test piece for cross-sectional observation was impregnated with Struers mold resin (SpeciFix Resin / SpeciFix-20 Curing Agent), and the mold resin was cured to prepare a sample. About the sample, it cut | disconnects so that it may become perpendicular | vertical with respect to the joint surface of a test piece, After smooth | blunting the surface by grinding | polishing a cut surface, it was made to vapor-deposit carbon, and JEOL Co., Ltd. field emission scanning electron microscope (JSM7500F) Cross-sectional observation was performed. By cross-sectional observation with a field emission scanning electron microscope, it was observed whether the particles maintained their shape as they were or whether they were fused and maintained.
Using the paste, a linear pattern of 5 mm × 50 mm with a coating thickness of 0.1 to 0.2 mm is printed on the substrate by screen printing, and then from room temperature (25 ° C.) to 4.5 ° C. / Heating was started at a heating rate of 1 minute, and when 200 ° C. was reached, heating was continued for 1 hour while maintaining 200 ° C. to produce a test specimen for measuring resistivity. The specific resistance was measured by a four-terminal method using a multimeter (2001 type (memory 128K)) manufactured by Toyo Corporation.
Using the paste, a 1 cm × 1 cm square pattern with a coating thickness of 1 to 2 mm is printed on the substrate by screen printing, and then the rate of temperature increase from room temperature (25 ° C.) to 4.5 ° C./min. Heating was started, and when 200 ° C. was reached, heating was further continued for 1 hour while maintaining 200 ° C. to produce a test piece for measuring thermal conductivity. The thermal conductivity was measured by a laser flash method (Xe flash analyzer manufactured by NETZSCH).

(2) Measurement concerning thermal conductive paste A sample was prepared as follows.
The thermal conductive paste is applied on a slide glass substrate so that the thickness is 0.5 cm × 5.0 cm and the thickness is 100 μm, and the temperature is raised from room temperature (25 ° C.) to 200 ° C. in 60 minutes using a blower dryer. Then, it was baked by holding at 200 ° C. for 60 minutes to obtain a silver film. This was used as a sample for various analyses.
(2-1) Specific resistance / electric resistance / film thickness A heat conductive paste was applied on a slide glass so that the width was 0.5 cm, the length was 5.0 cm, and the thickness was 100 μm. Heating was started at room temperature (25 ° C.) at a rate of temperature increase of 3 ° C./min, and when 200 ° C. was reached, heating was further continued for 1 hour while maintaining 200 ° C. Thereafter, the film thickness of the obtained silver film was measured with a surface roughness / shape measuring instrument (Surfcom 300B) manufactured by Tokyo Seimitsu Co., Ltd., and then using a multimeter (2001 type (memory 128K)) manufactured by Toyo Corporation. Electrical resistance was measured by the terminal method. The specific resistance was determined from the obtained film thickness and electrical resistance.
(2-2) Thermal conductivity A thermal conductive paste is applied on a slide glass so that the coating thickness is 1 to 2 mm, and left as it is at room temperature (25 ° C.) to 3 ° C. / Heating was started at a temperature rising rate of 1 minute, and when the temperature reached 200 ° C., heating was further performed for 1 hour while maintaining 200 ° C. After the heating, it was cooled sufficiently to room temperature (25 ° C.), and the silver film formed on the slide glass was peeled off from the slide glass. The thermal conductivity of the silver film thus obtained was measured using a laser flash method (Xe flash analyzer manufactured by NETZSCH) to obtain a thermal conductivity value.
(2-3) Thermal resistance of joint part A heat conductive paste was applied on a silver-plated copper lead frame, and a semiconductor silicon chip (gold back coating semiconductor chip 3 mm × 3 mm) was mounted. After adjusting the coating thickness to 50 μm by weighting, heating was started at a heating rate of 3 ° C./min in a batch-type heating furnace, and when it reached 200 ° C., it was further maintained for 1 hour while maintaining 200 ° C. Heating was continued. After completion of the heating, the test piece for evaluation was produced by cooling to room temperature (25 ° C.). Evaluation of thermal resistance was measured using a thermal resistance measuring device (T3Ster manufactured by Mentor Graphics). Electrical connections were made to the PN junctions formed on the mounted chip components and the thermal resistance of the junctions was measured with a thermal resistance measuring device.
(2-4) Cross-sectional observation of silver film The thermal conductive paste was applied on a slide glass so that the width was 0.5 cm, the length was 5.0 cm, and the thickness was 100 μm, and the temperature was increased from room temperature to 3 with a blower dryer. Heating was started at a temperature increase rate of ° C./min, and when the temperature reached 200 ° C., heating was further performed for 1 hour while maintaining 200 ° C. After heating, it was sufficiently cooled to room temperature, and the silver film formed on the slide glass was peeled off from the slide glass. The thus obtained cured coating film was subjected to cross-section processing with an ion milling device (E-3500) manufactured by Hitachi High-Technologies Corporation, and cross-section observation was performed with a field emission scanning electron microscope (JSM7500F) manufactured by JEOL Ltd.
(2-5) Cross-sectional observation of joint portion A thermally conductive paste was applied on a silver-plated copper lead frame, and a silicon chip (gold back-coated semiconductor chip 2 mm × 2 mm) was mounted. After adjusting the coating thickness to 50 μm by weighting, heating was started at a heating rate of 3 ° C./min in a batch-type heating furnace, and when it reached 200 ° C., it was further maintained for 1 hour while maintaining 200 ° C. Continued overheating. After the heating, the evaluation substrate was cooled to room temperature. Next, a mold resin (SpeciFix Resin / SpeciFix-20 Curing Agent) manufactured by Struers was impregnated, and the mold resin was cured to prepare a sample. The sample was cut so as to be perpendicular to the bonding surface between the silicon chip and the lead frame, and the cut surface was smoothed by polishing, and then carbon deposited, and a field emission scanning electron microscope (manufactured by JEOL Ltd.) JSM7500F) was used for cross-sectional observation at a magnification of 1000 to 50,000 times.
(2-6) Die shear strength A thermally conductive paste was applied on a silver-plated copper lead frame, and a silicon chip (gold back-coated semiconductor chip 2 mm × 2 mm) was mounted. After adjusting the coating thickness to 50 μm by weighting, heating was started at a heating rate of 3 ° C./min in a batch-type heating furnace, and when it reached 200 ° C., it was further maintained for 1 hour while maintaining 200 ° C. Heating was continued. After completion of the heating, the test piece for evaluation was produced by cooling to room temperature. About the test piece for evaluation, the die shear strength was measured with a universal bond tester (series 4000) manufactured by Daisy Japan.
(2-7) Reliability evaluation: Cooling cycle test A thermal conductive paste was applied on a slide glass so as to have a width of 0.5 cm, a length of 5.0 cm, and a thickness of 100 μm. Then, heating was started at a rate of temperature increase of 3 ° C./min. When the temperature reached 200 ° C., heating was further continued for 1 hour while maintaining 200 ° C. After completion of the heating, the test piece for evaluation was produced by cooling to room temperature (25 ° C.). The test piece obtained in this way is put into a small thermal shock apparatus (TSE-11) manufactured by Espec Co., Ltd., and subjected to a thermal shock 1000 cycle test in which one cycle is left at -55 ° C for 30 minutes and left at + 125 ° C for 30 minutes. The cross section was observed with a field emission scanning electron microscope (JSM7500F) manufactured by JEOL Ltd. for cracks and peeling at the joint.
(2-8) Reliability evaluation: Fatigue test A thermal conductive paste was applied onto a slide glass so as to have a shape as shown in FIG. 1 and then from room temperature (25 ° C.) to 3 ° C. with a blow dryer. Heating was started at a rate of temperature rise / minute, and when the temperature reached 200 ° C., heating was further performed for 1 hour while maintaining 200 ° C. After the heating, it was cooled sufficiently to room temperature (25 ° C.), and the silver film formed on the slide glass was peeled off from the slide glass. For the silver film obtained in this way, using a micro mechanical testing machine manufactured by Kinomiya Seisakusho Co., Ltd., repeatedly applying stress to the test piece at a test temperature of 25 ° C. and a frequency of 5 Hz, and determining the number of cycles of the repeated stress required to break. A silver film fatigue test was performed.

  Each component used in the examples is as follows.

<Silver fine particles>
Silver fine particles A
In a 10 L glass reaction vessel, 3.0 kg (30.9 mol) of 3-methoxypropylamine was placed. While stirring, the reaction temperature was maintained at 45 ° C. or lower, and 5.0 kg (30.0 mol) of silver acetate was added. Immediately after the addition, the solution became a transparent solution and dissolved, but as the addition proceeded, the solution gradually became turbid, and when the entire amount was added, it became an ash brown cloudy viscous solution. To this, 1.0 kg (21.0 mol) of 95% by weight formic acid was slowly added dropwise. Vigorous exotherm was observed immediately after the addition, while the reaction temperature was maintained at 30 to 45 ° C. Initially, the turbid viscous solution changed from brown to black. The reaction was terminated after the entire amount was added dropwise. The reaction mixture was allowed to stand at 40 ° C. and separated into two layers. The upper layer is a yellow transparent liquid, and black silver fine particles settled in the lower layer. The upper layer liquid did not contain a silver component. The upper layer liquid was removed by decantation, 0.36 kg of benzyl alcohol was added, and methanol remaining under reduced pressure was distilled off by an evaporator to obtain a silver fine particle-containing paste having a silver content of 90% by mass.
The characteristics of the silver fine particles are as follows.
Average particle diameter 61 nm, crystallite diameter 40 nm, average particle diameter / crystallite diameter = 1.5,
ΔW _{25 ℃ → 500 ℃} = 10.0%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} = 0.3%
Exothermic peak = 234 ° C
(1-4) When the sinterability was measured, fusion was observed by cross-sectional observation, the specific resistance was 3 μΩ · cm, and the thermal conductivity was 197 W / mK.

Silver fine particles B: Fine particles obtained by coating silver fine particles produced by a reduction method with oleic acid (silver fine particle-containing paste (solvent: benzyl alcohol) having a silver content of 91% by mass)
Average particle size: 300 nm
ΔW _{25 ° C → 500 ° C} = 8.9%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} = 0.2%
Exothermic peak = 253 ° C
(1-4) When the above paste was measured for sinterability, fusion was observed by cross-sectional observation, the specific resistance was 5 μΩ · cm, and the thermal conductivity was 184 W / mK.
Silver fine particles C: Particles obtained by coating silver fine particles produced by a reduction method with oleylamine Average particle size: 20 nm
ΔW _{25 ° C. → 500 ° C.} = 24.6%
ΔW _{25 ° C. → 500 ° C.} −ΔW _{25 ° C. → 200 ° C.} = 4.8%
Exothermic peak = 179 ° C, 300 ° C
(1-4) The silver fine particles C were dispersed in benzyl alcohol to obtain a paste having a silver content of 90% by mass, and then sinterability was measured. No fusion was observed, the specific resistance was greater than 10 μΩ · cm, and the thermal conductivity was 25 W / mK.

FIG. 2 shows a TG chart of the silver fine particles A to C.
FIG. 3 shows a DTA chart of the silver fine particles A to C.
FIG. 4 shows photographs of the silver fine particles A to C before and after heating at 200 ° C. for 1 hour in the measurement of sinterability. The photograph before heating is an image when the paste is applied to the substrate, dried at room temperature (25 ° C.), and observed from above, and the photograph after heating is as described in the measurement of sinterability. It is a cross-sectional photograph when the cross section is exposed.

<Epoxy resin>
Epoxy resin A: Hexahydrophthalic acid diglycidyl ester epoxy resin B:

Epoxy resin C: Bisphenol F type epoxy resin Epoxy resin D: 1,4-bis [(glycidyloxy) methyl] cyclohexane epoxy resin E: Neodecanoic acid glycidyl ester oxetane resin: OXT121 manufactured by Toagosei Co., Ltd.

<Curing agent>
Cationic polymerization initiator: 4-methylphenyl [4- (1-methylethyl) phenyl] iodonium = tetrakis (pentafluorophenyl) borateamine curing agent: 3,3′-diaminodiphenylsulfonic acid anhydride curing agent: methylhexa Hydrophthalic anhydride imidazole curing agent: 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct

<Thermal radical generator>
Peroxide: 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate

<Solvent>
Solvent 1: Benzyl alcohol solvent 2: Dihydroterpineol

  The components shown in Table 1 below were agitated and defoamed using a hybrid mixer to make uniform, to obtain a heat conductive paste, and various properties were measured. The formulation is parts by mass. The results are shown in Table 1.

  In FIG. 5, the result of the cross-sectional observation of the silver film of the comparative example 1, Examples 1-5, and the comparative example 2 is shown.

  About the comparative example 1 and Example 3, the fatigue test of the silver film was done. The results are shown in FIG.

  In FIG. 7, the result of the cross-sectional observation of the junction part of Example 3 is shown. 7-1 is a result of observing the cross section at 2000 times, 7-2 is a result of observing a joint portion with the chip back surface at 10000 times, and 7-3 is a joint portion with the chip back surface is observed at 50000 times. It is a result and 7-4 is the result of having observed the junction part with the board | substrate surface by 5000 time.

As shown in Table 1 and FIG. 5, the silver film obtained using the paste of each example has excellent electrical characteristics and thermal conductivity, and has a cross-sectional structure in which a resin is filled between the silver films. It was. Furthermore, as shown in the results of die shear strength in Table 1, the silver film obtained using the paste of the example was excellent in mechanical strength. Furthermore, from the results of the thermal cycle test in Table 1 and the results of the fatigue test of the silver film in FIG. 6, the silver film obtained using the paste of the example was excellent in terms of reliability.
In addition, as shown in FIG. 7, it was confirmed that silver spreads and is well bonded to gold plating.

  The components shown in Table 2 below were agitated and defoamed using a hybrid mixer to make uniform, to obtain a heat conductive paste, and various properties were measured. The formulation is parts by mass. The results are shown in Table 2.

In FIG. 8, the result of the cross-sectional observation of the silver film of Example 6 and Reference Examples 1-4 is shown.

  As shown in Table 2 and FIG. 8, the silver film obtained by using each example was excellent in electrical characteristics and thermal conductivity, and had a cross-sectional structure in which a resin was filled between the silver films. In particular, Examples 1 and 2 in which the epoxy resin is an epoxy resin containing an ester bond are excellent in both properties. Among them, Example 1 using a phthalic acid diglycidyl ester epoxy resin is outstandingly excellent. It was.

  The components shown in Table 3 below were agitated and defoamed using a hybrid mixer to make uniform, to obtain a heat conductive paste, and various properties were measured. The formulation is parts by mass. The results are shown in Table 3.

FIG. 9 shows the results of cross-sectional observation of the silver films of Examples 6 , 11 , 12 and Reference Example 5 .

  As shown in Table 3, even when a curing agent other than the cationic curing agent was used, a silver film excellent in electrical characteristics and thermal conductivity was obtained. In particular, as shown in FIG. 7, the progress of sintering was confirmed for the silver film using the cationic polymerization initiator, the amine curing agent, and the acid anhydride curing agent.

  The components shown in Table 4 below were agitated and defoamed using a hybrid mixer to make uniform, to obtain a heat conductive paste, and various properties were measured. The formulation is parts by mass. The results are shown in Table 3.

  As shown in Table 4, when silver fine particles A and B were used, a silver film excellent in electrical characteristics and thermal conductivity was obtained. On the other hand, when silver fine particles C not corresponding to the silver fine particles of the present invention were used, silver was not sintered and the silver film itself was not obtained.

  According to the heat conductive paste of the present invention, a silver film having improved mechanical strength and reliability can be obtained without using a special technique such as an impregnation process. In addition, this silver film is excellent in terms of electrical conductivity and thermal conductivity, and is suitable as a bonding member in semiconductor devices such as bumps and die attach materials. Furthermore, when a conventional heat conductive paste containing silver fine particles is used as a bonding member, heat treatment and pressure treatment are generally used in combination in order to obtain sufficient bonding strength. According to the paste, sufficient bonding strength can be obtained only by heat treatment, and convenience is high.

Claims (6)

Low temperature sinterable silver fine particles; and a thermosetting binder,
Thermosetting binder
(B1) at least one epoxy resin selected from the group consisting of phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and their C1-C4 alkyl substituents, and
(B2) At least one curing agent selected from the group consisting of a cationic polymerization initiator, an amine curing agent and an acid anhydride curing agent
Consists of
The heat conductive paste whose thermosetting binder is 2-7 mass parts with respect to 100 mass parts of silver fine particles. Silver fine particles having an average particle diameter of 40 to 350 nm, a crystallite diameter of 20 to 70 nm, and a ratio of the average particle diameter to the crystallite diameter of 1 to 5; and a thermosetting binder,
Thermosetting binder
(B1) at least one epoxy resin selected from the group consisting of phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and their C1-C4 alkyl substituents, and
(B2) A curing agent selected from the group consisting of a cationic polymerization initiator, an amine curing agent and an acid anhydride curing agent
Consists of
The heat conductive paste whose thermosetting binder is 2-7 mass parts with respect to 100 mass parts of silver fine particles. The thermally conductive paste according to claim 1 or 2 , wherein (B2) is a cationic polymerization initiator. The thermally conductive paste according to any one of claims 1 to 3 for die attach of a semiconductor device. The thermally conductive paste according to any one of claims 1 to 3 , which is used for forming a bump of a semiconductor device. The semiconductor device which used the heat conductive paste of any one of Claims 1-3 for joining of components.