JP2013225375A - Conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste capable of favorably melting solder particles in a conductive paste and of allowing a resin cured part after heat treatment to have excellent resistance against severe environments such as high temperature, high humidity and pressurization.SOLUTION: Provided is a conductive paste which comprises a heat curable resin, a curing agent, an organic acid and a metal particle. The curing agent comprises a nitrogen compound having an imidazole structure or an amino group or both and having molecular weight of 220 g/mol or more, and the metal particle comprises a solder particle. In a preferable embodiment, the nitrogen compound is an isocyanuric acid adduct.

Description

  The present invention relates to a conductive paste using a thermosetting resin, and further relates to a component mounting substrate, an electronic component, or a laminated substrate bonded using the conductive paste.

  With recent high performance of electronic equipment, development of high-density packaging technology is remarkable. For this reason, since the size of electronic components to be mounted has been remarkably reduced, the bonding strength of each component has been lowered, and a bonding material with higher bonding strength is required.

  For example, passive components such as resistors and capacitors have recently been replaced with 0402 (0.40 mm × 0) in place of conventional 1005 (1.0 mm × 0.50 mm) and 0603 (0.60 mm × 0.30 mm) size components. .20 mm) size components will be mounted, and further miniaturization to 0201 (0.20 mm × 0.10 mm) size is expected in the future. Therefore, since the bonding strength of each small component becomes weak, reinforcement of the bonding strength of the small component particularly in surface mounting is an important issue.

  In order to reinforce the bonding strength of parts against such problems, parts are made using a thermosetting resin-type solder paste that is made into a paste with solder particles by adding an organic acid to the thermosetting resin composition. A method of mounting has been proposed (Patent Document 1). By mounting the component using the paste, a joint portion made of a thermosetting resin and a joint portion made of solder are simultaneously formed by a single heat treatment, thereby improving the joint strength of the component.

  Separately from this, a technique has been reported for increasing the conductivity by adding a predetermined amount of solder particles to a conductive paste comprising a thermosetting resin composition and high melting point metal particles such as Cu particles. (Patent Document 2).

JP 2010-279962 A JP 2011-142093 A

  However, since the cured portion of the thermosetting resin composition after heat treatment is weaker in high temperature, high humidity, and pressurized environments than metal, it is extremely important to increase resistance to such environments. In addition, when solder particles are included in the conductive paste, it is preferable to add an organic acid to the thermosetting resin composition in order to efficiently remove the oxide film on the surface of the solder particles. A chemical reaction also occurs between the thermoset resin and the thermosetting resin. In such a complicated paste composition, any hardener can be used to melt the solder well, and the conductive paste has good resistance to the environment such as high temperature, high humidity, and pressure There is not enough knowledge about whether it can be obtained.

  From such a background, the object of the present invention is to allow the solder particles in the conductive paste to be melted well, and in addition, the conductive paste cured part after the heat treatment has a severe environment, particularly high temperature and high It is an object to provide a conductive paste that provides excellent connection stability by having excellent resistance to wet and pressurized environments.

[1] A conductive paste containing a thermosetting resin, a curing agent, an organic acid, and metal particles, wherein the curing agent has an imidazole structure or an amino group, or a nitrogen compound having a molecular weight of 220 g / mol or more. And a conductive paste in which the metal particles include solder particles.
[2] The conductive paste according to [1], wherein the nitrogen compound is an isocyanuric acid adduct.
[3] The ratio of the content of the curing agent and the organic acid to the total content of the thermosetting resin, the curing agent, and the organic acid is 0.50 to 20% by mass, respectively, and the entire curing agent The conductive paste according to the above [1] or [2], wherein the proportion of the nitrogen compound in the water is 20% by mass or more.
[4] The conductive paste according to any one of [1] to [3], wherein the thermosetting resin contains an epoxy resin.
[5] The conductive paste according to any one of [1] to [4], wherein the organic acid contains glutaric acid or adipic acid.
[6] The conductive paste according to any one of [1] to [5], wherein the conductive paste further contains a thixotropic agent.
[7] The solder particles have a melting point of 240 ° C. or less, and the solder particles are Sn particles, or Sn and Ag, Au, Bi, Cu, Ge, In, Sb, Ni, Zn, and Pb. The electrically conductive paste in any one of said [1]-[6] which is Sn alloy particle | grains containing at least 1 sort (s) of the metal selected from the group which consists of.
[8] The solder particles are Sn alloy particles containing Sn and at least one metal selected from the group consisting of Bi, In and Zn, and the Sn alloy particles have a melting point of 200 ° C. or less. The conductive paste according to [7] above.
[9] The conductive paste according to any one of [1] to [8], wherein the metal particles include at least one high melting point metal particle having a melting point of 300 ° C. or higher.
[10] The above [9], wherein the refractory metal particles are one or more selected from the group consisting of Cu particles; Ag particles; and alloy particles containing at least one of Cu and Ag. Conductive paste.
[11] A component mounting substrate including a substrate electrode, an electronic component electrode, and a joint interposed therebetween, and the joint heat-treats the conductive paste according to any one of [1] to [10]. A component mounting board that is formed by
[12] A laminate including a first electronic component having a first electrode, a second electronic component having a second electrode, and a joint interposed between the first electrode and the second electrode A laminated electronic component, which is an electronic component, wherein the joint is formed by heat-treating the conductive paste according to any one of [1] to [10].
[13] A laminated substrate including a first substrate having a first electrode, a second substrate having a second electrode, and a junction interposed between the first electrode and the second electrode. A laminated substrate in which the bonding portion is formed by heat-treating the conductive paste according to any one of [1] to [10].

  According to the conductive paste provided by the present invention, it is possible to melt the solder particles contained in the conductive paste satisfactorily, and in addition, the conductive paste cured portion after the heat treatment has a severe environment, particularly at high temperatures. Excellent resistance to moisture absorption and pressure environment. Therefore, the conductive paste provided by the present invention provides excellent connection stability.

<Conductive paste>
One embodiment of the present invention is a conductive paste including a thermosetting resin, a curing agent, an organic acid, and metal particles, and the curing agent has a molecular weight having an imidazole structure (that is, an imidazole ring) and / or an amino group. It is a conductive paste containing a nitrogen compound of 220 g / mol or more, and the metal particles contain solder particles. Hereinafter, preferred embodiments of each component will be described.

[Thermosetting resin]
As the thermosetting resin, epoxy resin, phenol resin, cyanate ester resin, melamine resin, polyimide resin, bismaleimide resin, urea resin, alkyd resin, vinyl ester resin, benzoxazine resin, urethane resin, acrylic resin, etc. are used. can do. The thermosetting resin preferably contains an epoxy resin, and more preferably the thermosetting resin is an epoxy resin, from the viewpoints of resin curing characteristics at low temperatures and adhesion to the bonded portion. Epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hindered type epoxy resin, biphenyl type epoxy resin, alicyclic epoxy resin, triphenylmethane type epoxy resin, phenol novolac type epoxy. Resins, cresol novolac type epoxy resins and epoxy resins halogenated from these resins, diglycidyl ethers such as polyethylene glycol, polypropylene glycol, butanediol, hexanediol, and cyclohexanedimethanol can be used. Furthermore, as a polyfunctional epoxy resin having three or more epoxy groups in the molecule, which is preferable from the viewpoint of forming a three-dimensional crosslinked structure, for example, a phenol novolac type epoxy resin, a cresol novolak type epoxy resin, a naphthol novolak type epoxy resin, Examples thereof include bis A novolac type epoxy resin, dicyclopentadiene / phenol epoxy resin, alicyclic amine epoxy resin, aliphatic amine epoxy resin and the like. Among these, bisphenol A type epoxy resins and bisphenol F type epoxy resins having a relatively low viscosity are preferable from the viewpoint of pasting.

[Curing agent]
The conductive paste of the present invention is a conductive paste containing a nitrogen compound having an imidazole structure and / or an amino group and having a molecular weight of 220 g / mol or more as a curing agent. The molecular weight of the nitrogen compound is preferably 240 g / mol or more, more preferably 250 g, from the viewpoint of suppressing reactivity and allowing a mild curing reaction to proceed and improving resistance to high temperature, high humidity, and pressurized environments. / Mol or more. On the other hand, in order to sufficiently advance the reaction with the thermosetting resin (for example, epoxy resin) in a short heat treatment process such as reflow, a curing agent having a small steric hindrance in terms of chemical structure is preferable. From this viewpoint, the molecular weight of the curing agent is preferably 1000 g / mol or less, more preferably 600 g / mol or less. The molecular weight described in the present disclosure can be confirmed by gel permeation chromatographic analysis (GPC). In addition, about a commercial item, it can be the value announced by the manufacturer etc. The molecular weight value specified in the present invention may be a value based on any of the above.

  Further, the nitrogen compound having a molecular weight of 220 g / mol or more added as a curing agent has an imidazole structure and / or an amino group. Since these have a lone electron pair contributing to the reactivity with the thermosetting resin, they function well as a curing agent in the present invention.

  As the nitrogen compound having a molecular weight of 220 g / mol or more, an imidazole curing agent is preferable from the viewpoint of improving resistance to high temperature, high humidity, and pressurized environment. Further, by using an imidazole-based curing agent, particularly when the adherend is a Cu plate, the adhesive strength is improved. Preferable specific examples include imidazole curing agents represented by formulas (I) and (II) described later.

  That is, from the above viewpoint, as a curing agent having a molecular weight of 220 g / mol or more suitable for the conductive paste of the present invention, the following formula (I):

A curing agent represented by In the above formula (I), R ₁ is an alkylene chain having 1 to 5 carbon atoms, R ₂ is an alkyl group having 2 to 12 carbon atoms, R ₃ is a hydrogen atom or an alkyl group having 5 or less carbon atoms, and R ₄ is hydrogen. An atom or an alkyl group having 5 or less carbon atoms is represented. Specific examples of the curing agent include 2,4-diamino-6- [2′-undecylimidazolyl- (1 ′)]-ethyl-s-triazine (for example, product name, C11Z-A manufactured by Shikoku Kasei Co., Ltd.). It can be illustrated.

  Further, as an imidazole curing agent having a molecular weight of 220 g / mol or more, the following formula (II):

Is also preferred from the viewpoint of imparting resistance to high temperature, high humidity, and pressurized environment. In the above formula (II), R ¹ represents an alkyl group having 11 or more carbon atoms, R ² represents a hydrogen atom or an alkyl group having 5 or less carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 5 or less carbon atoms. More specifically, 2-undecylimidazole is preferred.

  Examples of the nitrogen compound having an amino group and a molecular weight of 220 g / mol or more include 2,4-diamino-6-methacryloyloxyethyl-s-triazine. For example, any one of 2, 4, and 6 positions of triazine It is preferable to use a nitrogen compound having an amino group. According to such a nitrogen compound, a lone pair of triazine and an amino group forms a conjugated structure, and the reactivity of the amino group with the thermosetting resin proceeds gently, so that it can withstand high temperature, high humidity, and pressurized environments. Resistance can be improved.

  Further, from the viewpoint of improving resistance to high temperature, high humidity, and pressurized environment, the nitrogen compound having an imidazole structure and / or an amino group and having a molecular weight of 220 g / mol or more is most preferably an isocyanuric acid adduct. Specific examples of the isocyanuric acid adduct include 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s— having an imidazole structure and / or an amino group in the molecular structure. Triazine isocyanuric acid adduct dihydrate (for example, product name 2MA-OK manufactured by Shikoku Kasei Co., Ltd.), 2-phenylimidazole isocyanuric acid adduct (for example, product name 2PZ-OK manufactured by the same company), 2-methylimidazole isocyanuric Acid adduct dihydrate (for example, product name 2MZ-OK manufactured by the same company), 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct (for example, product name manufactured by the same company, VT-OK), 2,4-diamino-6-methacryloyloxyethyl-s-triazine isocyanuric acid adduct (for example, product name, MAVT-OK manufactured by the same company), - phenyl-4-hydroxymethyl-5-methylimidazole isocyanuric acid adduct and the like. In particular, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct dihydrate (eg, 2MA-OK described above), and 2- Phenylimidazole isocyanuric acid adducts (for example, 2PZ-OK described above) are preferable from the viewpoint of improving resistance to high temperatures, high humidity, and pressurized environments.

  For example, for the purpose of adjusting the curing speed and / or the curing temperature, as a curing agent other than the nitrogen compound (hereinafter also referred to as an additional curing agent component), for example, a known curing agent as shown below is used. May be. Specifically, alcoholic amines such as monoethanolamine, diethanolamine, and triethanolamine; nonalcoholic amines such as butylamine, diethylenetriamine, xylylenediamine, isophoronediamine, norbornenediamine, metaphenylenediamine, and diphenylguanidine; Amine salts such as chloride salts and bromide salts of organic acids; organic acid dihydrazides; and the like. Triethanolamine, which is an alcoholic amine, and butylamine are preferred. As the additional curing agent component, compounds known as curing agents such as phosphorus compounds, phenol resins, and acid anhydrides can also be used.

  Specific examples of combined use are 2-phenylimidazole isocyanuric acid adduct (for example, 2PZ-OK manufactured by Shikoku Kasei Co., Ltd.) as an imidazole-based curing agent, non-alcoholic amines such as n-alkylamine and / or triethanolamine. In combination with alcoholic amines such as Further, an imidazole curing agent having a molecular weight of 220 g / mol or more and a nitrogen compound having an imidazole structure and / or an amino group having a molecular weight of less than 220 g / mol can be used in combination. Specifically, the molecular weight is 220 g / mol or more. 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct dihydrate or 2-phenylimidazole isocyanuric acid adduct (for example, Shikoku Chemicals) Product name, 2MA-OK or 2PZ-OK) and a compound having a molecular weight of less than 220 g / mol, such as 2-phenylimidazole (for example, product name 2PZ, manufactured by Shikoku Kasei Co., Ltd.), 2-methylimidazole (for example, manufactured by the company) Product name, 2MZ), 2-phenyl-4-methylimidazole (for example, product name 2P4MZ manufactured by the same company) ) And at least one of 2-phenyl-4-methyl-5-hydroxymethylimidazole (for example, product name 2P4MHZ manufactured by the same company) is preferable.

  In the conductive paste, the ratio of the content of the curing agent to the total content of the thermosetting resin, the curing agent and the organic acid is 0.50 from the viewpoint of the curing characteristics of the thermosetting resin and the storage stability of the conductive paste. -20 mass% is preferable, More preferably, it is 2.0-15 mass%, More preferably, it is 3.0-10 mass%. If the fluidity of the conductive paste is ensured in the vicinity of the melting point of the solder particles added to the conductive paste, the molten solder particles can form metal bonds well. Therefore, it is preferable to adjust the addition amount of the curing agent in order to ensure the fluidity. For example, when the melting point of the solder particles to be added is high, the amount of heat given to the conductive paste before the solder particles are melted by heat treatment of the conductive paste increases the resin flow in the temperature range where the solder particles melt. It is difficult to secure the sex. As a specific example, when adding the same type of curing agent, compared to using Sn-58Bi (melting point: 138 ° C.) particles for solder particles, using Sn (melting point: 232 ° C.) for solder particles. However, it is preferable to reduce the addition amount of the curing agent. The conductive paste of the present invention contains a predetermined amount of an organic acid, so that the solder particles can be melted well during heat treatment, and a nitrogen compound having a molecular weight of 220 g / mol having an effect of exhibiting resistance to moist heat. The addition amount may be adjusted within a range in which the resin fluidity that allows the solder particles to melt well can be secured, and the solder particles to be added are not limited to a specific composition.

  Further, the ratio of the nitrogen compound having a molecular weight of 220 g / mol or more to the entire curing agent is preferably higher from the viewpoint of obtaining good resistance of the thermosetting resin to high temperature, high humidity, and pressurized environment, preferably 20 It is at least mass%, more preferably at least 35 mass%, even more preferably at least 45 mass%, and may be 100 mass%. When the nitrogen compound having a molecular weight of 220 g / mol or more and an additional curing agent component are used in combination, resistance to high temperature / high humidity / pressurized environment and desired characteristics due to the additional curing agent component are obtained. The ratio of the additional curing agent component relative to the entire curing agent may be appropriately adjusted as desired. The proportion is preferably 80% by mass or less, more preferably 65% by mass or less, and still more preferably 55% by mass or less.

[Organic acid]
The organic acid contributes to the curing reaction of the thermosetting resin, but is mainly used for the purpose of cleaning the oxide film on the surface of the metal particles contained in the conductive paste and preventing reoxidation. As the organic acid, known monocarboxylic acid, dicarboxylic acid, tricarboxylic acid and the like can be used. Examples include glutaric acid, adipic acid, benzoic acid, stearic acid, citric acid, oxalic acid, succinic acid, sebacic acid, malonic acid, pimelic acid, suberic acid, azelaic acid, citraconic acid, α-ketoglutaric acid, diglycolic acid Thiodiglycolic acid, dithiodiglycolic acid, levulinic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, 4-aminobutyric acid, 3-mercaptopropionic acid, 3-mercaptoisobutyric acid, 3-methylthiopropionic acid, 3 -Phenylpropionic acid, 3-phenylisobutyric acid, 4-phenylbutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, nonanoic acid, oleic acid, linoleic acid, arachidonic acid, undecylenic acid, 2,2- Dimethylbutyric acid, α-linolenic acid, palmitoleic acid, docosahexaenoic acid, Examples include ristoleic acid, CO-FA-S (manufactured by Ito Oil Co., Ltd.), rosin, and modified rosin. Among these, from the viewpoint of the action of cleaning the oxide film on the metal particle surface, the organic acid preferably contains dicarboxylic acid, and more preferably contains glutaric acid or adipic acid. In a preferred embodiment, the organic acid is a dicarboxylic acid. In a more preferred embodiment, the organic acid is glutaric acid and / or adipic acid. In the conductive paste, the ratio of the content of the organic acid to the total content of the thermosetting resin, the curing agent, and the organic acid is the viewpoint of the solder melting characteristics, the curing characteristics of the thermosetting resin, and the storage stability of the conductive paste. To 0.50 to 20% by mass, more preferably 3.0 to 15% by mass, and still more preferably 4.0 to 10% by mass.

[Metal particles]
The conductive paste includes metal particles. From the above viewpoint, the content of the metal particles in the conductive paste is preferably 60 to 95% by mass, and more preferably 80 to 94% by mass. When the content of the metal particles is 95% by mass or less, the viscosity of the paste is optimized, and the printability in screen printing or the like is improved. It is preferable that the content of the metal particles is 60% by mass or more because the precipitation of the metal particles can be suppressed.

  The average particle diameter of the metal particles can be determined according to the use application of the conductive paste. The average particle diameter is preferably 2 to 40 μm, more preferably 5 to 38 μm, and more preferably 10 to 36 μm. The average particle diameter is preferably 2 μm or more from the viewpoint of lowering the oxygen concentration on the surface of the metal particles, and preferably 40 μm or less from the viewpoint of forming a fine printed pattern.

  For example, in screen printing applications, it is preferable to make the particle size distribution of the metal particles broader with emphasis on plate slippage. The particle size distribution in this case is preferably 3 to 40 μm, more preferably 5 to 36 μm. On the other hand, in dispensing applications, it is preferable to make the particle size distribution of metal particles sharper with emphasis on discharge fluidity and hole filling properties. In this case, the particle size distribution is preferably 2 to 30 μm, more preferably 5 to 25. It is also possible to use vias opened in a substrate, prepreg or the like with a laser or the like, and buried in the vias as a conductive paste for filling vias and heat-treated. In addition, as a filling method, a printing machine can be illustrated, for example, More preferably, it is a vacuum printing machine. When used for filling vias, it is preferable to add the refractory metal to the conductive paste to suppress the surface tension during melting of the solder particles, and in that case, the particle size of the metal particles contained in the solder paste The distribution is preferably sharp, preferably 2 to 30 μm, more preferably 5 to 25. Further, the average particle diameter is preferably 1/3 or less of the via diameter.

  The above average particle size and particle size distribution are values measured by a laser diffraction particle size distribution measuring device.

  The elemental composition of the metal specified in this specification can be confirmed by, for example, inductively coupled plasma (ICP) emission analysis. The metal particles may contain unavoidable impurities.

(Solder particles)
The metal particles used for the conductive paste of the present invention include solder particles. In the present disclosure, the solder particles mean metal particles containing Sn and having a melting point of less than 300 ° C. As described above, if the fluidity of the conductive paste is secured in the vicinity of the melting point of the solder particles contained in the conductive paste, the molten solder particles can form metal bonds well. The conductive paste of the present invention contains a predetermined amount of an organic acid, so that the solder particles can be satisfactorily melted during heat treatment, and has a molecular weight of 220 g / mol or more, which has an effect of exhibiting heat and humidity resistance. The addition amount can be adjusted within a range in which the resin fluidity that allows the solder particles to melt well can be secured. The solder particles to be added are not limited to a specific composition.

  From the viewpoint of heat treatment at a heat treatment peak temperature equivalent to that of a general lead-free solder paste, the solder particles preferably have a melting point of 240 ° C. or lower. From the viewpoint of forming an intermetallic compound containing Sn between the metal particles contained in the conductive paste when the conductive paste is heat-treated, the solder particles are Sn particles, or Sn and Ag, Au, Sn alloy particles containing at least one metal selected from the group consisting of Bi, Cu, Ge, In, Sb, Ni, Zn and Pb are preferable. Specifically, Sn-Bi system, Sn-In system, Sn-Cu system, Sn-Zn system, Sn-Ag system, Sn-Au system, Sn-Pb system, Sn-Sb system, Sn-Bi-Ag Type, Sn-Ag-Cu type, Sn-Bi-Cu type, Sn-Zn-Bi type, Sn-Bi-In type, Sn-Ag-In type, Sn-Ag-In-Bi type, Sn-Cu- Examples thereof include Ni-based, Sn-Cu-Ni-Ge-based, and Sn-Ag-Cu-Ni-Ge-based solder particles. As a solder having a recommended heat treatment peak temperature of the conductive paste of 230 ° C. or higher, Sn—Ag—Cu (for example, Sn-3.0Ag-0.5Cu) series or Sn—Ag (for example, Sn-3.5Ag) Systems and Sn are preferred. Moreover, as the lead-free solder whose reflow peak temperature is recommended to be 200 ° C. or lower, Sn alloy particles containing Sn and having a melting point of 200 ° C. or lower containing any of Bi, In, and Zn are preferable. Among these, Sn-58Bi and Sn-57Bi-1Ag are preferable.

  The melting point of the metal particles described in the present disclosure is measured under a nitrogen atmosphere under a temperature increase of 10 ° C./min using a differential scanning calorimeter (DSC), and the endothermic peak at the lowest temperature is in accordance with JIS Z3198-1. The required melting point.

  The solder particles to be used are not limited to one type. For example, Sn particles or Sn alloy particles containing Sn and at least one metal selected from the group consisting of Ag, Au, Bi, Cu, Ge, In, Sb, Ni, Zn, and Pb are separated. It can be used in combination with solder particles having the following composition. For example, by combining Sn particles or Sn alloy particles as the second solder particles with the first solder particles of 42Sn / 58Bi, the Bi composition of the joint after reflow can be reduced. In general, Bi exhibits mechanically fragile characteristics, so that the Bi composition after reflow can be reduced by further using the Sn particles or Sn alloy particles, which leads to improvement in brittleness.

(High melting point metal particles)
The conductive paste of the present invention can obtain the effects such as wet heat resistance of the present invention by using only solder particles as the metal particles. In addition to the solder particles, the high melting point metal particles having a melting point of 300 ° C. or higher. 1 or more types may be included. By adding refractory metal particles, it is possible to impart heat resistance to the metal composition after the heat treatment. That is, by adding the refractory metal particles to the solder particles, more metal having a high melting point is formed by metal diffusion between the refractory metal particles and the solder, and thus heat resistance can be imparted. In addition, since the solder particles can be melted by heat treatment and the refractory metal particles can be joined to each other by metal bonding, a predetermined amount of solder particles is included in addition to the refractory metal particles for the purpose of reducing connection resistance. It is preferable.

  For the above reasons, when refractory metal particles are used, the ratio of the refractory metal particles to the entire metal particles is preferably 15% by mass to 90% by mass. Above all, when importance is attached to forming a joint having excellent solder luster with less unevenness on the surface of the joint, such as a conventional solder paste, the ratio of the refractory metal particles is preferably 15% by mass to 30% by mass. . On the other hand, when emphasizing the formation of a joint having excellent heat resistance, the proportion of the refractory metal particles is preferably 30% by mass to 90% by mass.

  The melting point of the refractory metal particles is more preferably 350 ° C. or higher, further preferably 400 ° C. or higher. The melting point is preferably 2000 ° C. or less, more preferably 1500 ° C. or less, from the viewpoint of lowering the necessary heat treatment temperature in the process of producing high melting point metal particles by atomization or the like. Metal particles used in a general conductive paste are Ag particles or Cu particles. However, the conductive paste containing these metal particles imparts conductivity by bringing the metal particles into point contact with each other using the curing shrinkage of the thermosetting resin during the heat treatment. On the other hand, as disclosed in Patent Document 2, when the conductive paste contains refractory metal particles such as Cu particles and solder particles, a metal is formed between the molten solder and the refractory metal particles. Techniques for forming bonds and improving conductivity have been reported. In the conductive paste of the present invention, it is possible to melt the solder well, and the thermosetting resin cured portion after the heat treatment has a high resistance to high temperature, high humidity, and pressurized environment. Therefore, the conductive paste of the present invention can be suitably used as a conductive paste containing refractory metal particles and solder particles as described above.

  The refractory metal particles contain at least one metal selected from the group consisting of Ag, Bi, Cu, Ge, In, Sn, Sb, Ni, Zn, Pb, and Au, and have a melting point of 300 ° C. or higher. Preferably there is. From the viewpoint of metal diffusibility between the molten solder particles and the refractory metal particles, the refractory metal particles include Cu particles, Ag particles, or alloy particles containing Cu or Ag (both Cu alloy particles and Ag alloy particles, respectively). Is preferred).

  The Cu alloy particles are preferably alloy particles containing Cu and at least one metal selected from the group consisting of In, Ni, Sn, Bi, Ag and Ge. In and Ni have the effect of refining the crystal grains of the Cu-Sn intermetallic compound formed at the interface between the melted solder and the Cu alloy particles, so that the Cu alloy particles contain In or Ni. Is preferred. From the viewpoint of forming a stable alloy phase, the total content of In and Ni in the Cu alloy particles is preferably 0.10 to 10% by mass, more preferably 0.50 to 8.0% by mass, More preferably, it is 1.0-6.0 mass%. Since Sn and Bi have good wettability with molten solder, it is preferable to contain Sn and / or Bi in an amount of 50% by mass or less in total in the Cu alloy particles. From the viewpoint of obtaining good wettability, the total content of Sn and Bi is preferably 10% by mass or more, more preferably 15% by mass or more. Ag is preferable from the viewpoint of forming a joint having heat resistance because it easily forms an Sn component of molten solder and an intermetallic compound having a high melting point.

  Furthermore, it is preferable that Cu alloy particle contains Ag at 95 mass% or less from a viewpoint of making resistance of a solder joint part low, and improving an electrical property. In this case, the content of Ag in the Cu alloy particles is preferably 50% by mass or less from the viewpoint of cost. The content of Ag is preferably 2% by mass or more, more preferably 5% by mass or more, from the viewpoint of obtaining a favorable effect of improving electrical characteristics. Since Ge is preferentially oxidized when the solder is melted and has an effect of suppressing oxidation of other solder components such as Sn, it is preferably contained in Cu alloy particles by 0.10% by mass or more. From the viewpoint of preventing the oxide from inhibiting the solder flow and adversely affecting the bondability, the Ge content is preferably 5.0% by mass or less. In the most preferred embodiment, the Cu alloy particles contain 5 to 15 mass% Ag, 2 to 8 mass% Bi, 49 to 81 mass% Cu, 2 to 8 mass% In, and 10 to 20 mass% Sn.

  Moreover, it is preferable that Ag alloy particle contains Sn from a viewpoint of improving the wettability with the molten solder. Further, the Ag alloy particles are preferably alloy particles containing Ag and In and / or Bi from the viewpoint of improving the bondability at a low temperature.

[Other ingredients]
In addition to the thermosetting resin, the curing agent, the organic acid, and the metal particles, the conductive paste can further include various optional components for improving paste characteristics. Examples of such components include thixotropic agents, antifoaming agents, antioxidants, solvents, halogen compound activators, inorganic fillers, and the like.

(Thixotropic agent)
As the thixotropic agent, any thixotropic agent conventionally used as a flux of Pb-free solder can be used, and examples thereof include castor oil, hydrogenated castor oil, sorbitol-based thixotropic agent and the like.

(Inorganic filler)
The conductive paste may further contain an inorganic filler. Examples of the inorganic filler include ceramic particles such as silica particles. By adding the inorganic filler, for example, when the electronic component and the substrate are bonded with a conductive paste containing a thermosetting resin, a difference in linear expansion coefficient between the electronic component and the bonded portion can be reduced.

<Component mounting board, laminated electronic component, or laminated board using conductive paste>
Another aspect of the present invention is a component mounting substrate including a substrate electrode, an electronic component electrode, and a joint portion interposed therebetween, and the joint portion is formed by heat-treating the above-described conductive paste of the present invention. Provided is a component mounting board.
Another embodiment of the present invention provides a first electronic component having a first electrode, a second electronic component having a second electrode, and a gap between the first electrode and the second electrode. Provided is a multilayer electronic component including an intervening junction, and the junction is formed by heat-treating the above-described conductive paste of the present invention.
In another embodiment of the present invention, a first substrate having a first electrode, a second substrate having a second electrode, and the first electrode and the second electrode are interposed. Provided is a laminated substrate including a bonding portion, and the bonding portion is formed by heat-treating the above-described conductive paste of the present invention.

  Each of the substrate electrode, the electronic component electrode, the laminated electronic component, and the laminated substrate can have any conventionally known configuration. Between each of the electrodes, the conductive paste of the present invention is interposed, and heat treatment is performed at a temperature equal to or higher than the melting point of the solder particles contained in the conductive paste. Bonding by the bonding portion by the conductive resin cured portion can be obtained by a single heat treatment. As a method for applying the conductive paste onto the electrode, general known techniques such as screen printing, dispensing, and transfer can be used.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to this.
The average particle diameter of each metal particle was determined as an average particle diameter value by measuring a volume integrated average value with a laser diffraction particle size distribution measuring device “HELOS & RODOS” manufactured by Sympatec (Germany).
The melting point of the solder particles was measured using “DSC-60” manufactured by Shimadzu Corporation under a nitrogen atmosphere at a temperature increase of 10 ° C./min, and the melting point obtained according to JIS Z3198-1 for the lowest endothermic peak. did. When the endothermic amount was quantified, those with 1.5 J / g or more were regarded as peaks derived from the measurement object, and peaks less than that were excluded from the viewpoint of analysis accuracy.

[Example 1]
(1) Metal Particles Solder particles Bi-42Sn (element composition is Bi: 58 mass%, Sn: 42 mass%) with a particle size of 25 μm to 45 μm manufactured by Yamaishi Metal Co., Ltd. were used as metal particles. When the average particle size of the solder particles was measured with a laser diffraction particle size distribution analyzer (HELOS & RODOS), the average particle size was 35 μm. Further, when the solder particles were measured with a differential scanning calorimeter (Shimadzu Corporation: DSC-50) in a nitrogen atmosphere under a temperature rising rate of 10 ° C./min in the range of 40 to 200 ° C., the temperature became 138 ° C. A melting point was detected.

(2) Thermosetting resin composition As thermosetting resins, epoxy resin (AER260) manufactured by Asahi Kasei Epoxy Co., Ltd., which is a bisphenol A type epoxy resin, and epoxy resin (YL983U) manufactured by Mitsubishi Chemical Co., Ltd., which is a bisphenol F type epoxy resin. As a curing agent, 2,4-diamino-6- [2′-undecylimidazolyl- (1 ′)]-ethyl-s-triazine (C11Z-A (molecular weight: manufactured by Shikoku Kasei Co., Ltd.) 359.5 g / mol)) and n-butylamine, adipic acid as an organic acid, and Gelol D made by Shin Nippon Science Co., Ltd. as a thixotropic agent in a ratio shown in Table 1, and a rotation / revolution mixer (made by THINKY) After kneading at room temperature (25 ° C.) for 5 minutes using Awatori Netaro, defoaming was performed for 3 minutes to prepare a thermosetting resin composition. As the adipic acid, adipic acid particles having an average particle diameter of 3.4 μm were used.

(3) Change in adhesive strength of thermosetting resin composition under high temperature, high humidity, and pressurized environment Between the copper plate of standard test piece CP1100P, the thermosetting resin composition prepared in (2) above The product was interposed between spacers formed of Teflon (registered trademark) heat-resistant tape having a thickness of 100 μm so that the adhesion area was 25 mm × 5 mm, and cured at 180 ° C. for 1 hour to obtain a copper plate sample. The adhesive strength of the obtained copper plate sample is S1, and the copper plate sample is allowed to stand for 1 hour under high temperature, high humidity and pressure conditions (105 ° C./100%/800 torr), and the adhesive strength is S2, respectively. As a result, S1 was 15.1 N / mm ² and S2 was 14.8 N / mm ² . Thereby, the effect of having excellent resistance to high temperature, high humidity, and pressurized environment was confirmed. The evaluation results are shown in Table 1. In this specification, having excellent resistance to high temperature, high humidity, and pressurized environments means that the strength deterioration after exposure to high temperature, high humidity, and pressurized environments is compared to the initial adhesive strength. It means that it satisfies the condition of ((S1-S2) / S1) × 100 <15.

(4) Preparation of conductive paste Kneading with a solder softener (Malcom: SPS-1) so that the composition of the thermosetting resin composition is 15 parts by mass with respect to 85 parts by mass of the metal particles, and a defoaming kneader. (Matsuo Sangyo: SNB-350) was used to produce a conductive paste.

(5) Measurement of solder particle melting characteristics The conductive paste prepared in (4) above is placed on an Au-plated electrode (electrode size: 1 mm × 1 mm) on a printed circuit board (with a solder resist) made of a highly heat-resistant epoxy resin glass cloth. An evaluation sample was obtained by printing and coating and N ₂ reflow (O ₂ concentration: 1000 ppm or less). A reflow simulator (Malcom: SRS-1C) was used as the heat treatment apparatus. In the temperature profile, the temperature was raised from the start of heat treatment (normal temperature) to 160 ° C. at 2.0 ° C./second, and held at 160 ° C. for 360 seconds. A screen printing machine (Microtech: MT-320TV) was used for forming the paste printing pattern. Metal masks and squeegees were used. The printing mask has an opening size of 1.0 mm × 0.60 mm (the center of the substrate electrode and the center position of the printing opening are the same) and a thickness of 0.08 mm. The printing conditions were a speed of 10 mm / second, a printing pressure of 0.1 MPa, a squeegee pressure of 0.2 MPa, a back pressure of 0.1 MPa, an attack angle of 20 °, a clearance of 0 mm, and a printing frequency of once. After reflow, 10 different electrodes were observed with an optical microscope to confirm whether all the molten solder particles were integrated. In the composition of this example, the solder particles were melted well and were all integrated. The results of this evaluation are shown in Table 1.

  From these results, the thermosetting resin composition of Example 1 can melt the solder well, and in addition, the cured portion of the thermosetting resin composition after the heat treatment has a high temperature, high humidity, and pressure. It can be seen that it has excellent resistance to the environment.

[Examples 2 to 13, Comparative Examples 1 to 7]
Thermosetting resin compositions having the compositions shown in Tables 1 and 2 were prepared in the same manner as in Example 1. As a compounding agent not used in Example 1, as an epoxy resin, an epoxy resin manufactured by Asahi Kasei Epoxy (EPN1182 (epoxy equivalent 180 g / eq)) and an epoxy resin manufactured by DIC Corporation (HP4032D (epoxy equivalent 142 g / eq) are used. )) As a curing agent, 2-phenylimidazole (2PZ (molecular weight: 144.2 g / mol)), 2-methylimidazole (2MZ (molecular weight: 82.1 g / mol)), 2-methyl manufactured by Shikoku Kasei Co., Ltd. Imidazole isocyanuric acid adduct dihydrate (2MZ-OK (molecular weight: 587.5 g / mol)), 2-undecylimidazole (C11Z (molecular weight: 222.4 g / mol)), 2-phenylimidazole isocyanuric acid adduct (2PZ-OK (molecular weight: 273.3 g / mol)), 2,4-dia No-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine isocyanuric acid adduct dihydrate (2MA-OK (molecular weight: 384.4 g / mol)), 2,4-diamino -6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine (2MZ-A (molecular weight: 219.3 g / mol)), 2-phenyl-4-methyl-5-hydroxymethylimidazole ( 2P4MHZ (molecular weight: 188.2 g / mol)), 2-phenyl-4-methylimidazole (2P4MZ (molecular weight: 158.2 g / mol)), triethanolamine were used, and glutaric acid was used as the organic acid. In the case of using glutaric acid, before kneading the thermosetting resin composition, a predetermined amount of glutaric acid is added to YL983U, heated and melted at 150 ° C. and cooled, and then the above (2) of Example 1 is used. ) To produce a thermosetting resin composition. With respect to these prepared thermosetting resin compositions, the change in adhesive strength before and after leaving in a high temperature, high humidity, and pressurized environment was measured in the same manner as in (3) of Example 1. The results are described below.

  In Example 2, Example 4 and Example 10 in which only 2MA-OK (molecular weight: 384.4 g / mol) was used as the curing agent, the relation of ((S1-S2) / S1) × 100 <15 was established. It can be seen that the cured portion of the thermosetting resin composition after heat treatment has excellent resistance to high temperature and high humidity environments. Furthermore, from the comparison between Example 2 and Example 10, even when the content of the curing agent in the thermosetting resin composition was increased, by using the curing agent that is an isocyanuric acid adduct, It can be seen that it has excellent resistance to wet and pressurized environments.

  Examples 3 and 9 using only 2PZ-OK (molecular weight: 273.3 g / mol) or 2MZ-OK (molecular weight: 587.5 g / mol) as a curing agent that is an isocyanuric acid adduct, Regarding Example 11 and Example 12 as well, there is a relationship of ((S1-S2) / S1) × 100 <15, and the cured part of the thermosetting resin composition after heat treatment is excellent for high temperature, high humidity, and pressurized environments. It can be seen that it has resistance. From this result, it can be seen that by using a curing agent having a molecular weight of 220 g / mol that is an isocyanuric acid adduct, high resistance to high temperature, high humidity, and pressurized environment can be imparted. It can also be seen that the resistance to high temperature, high humidity, and pressurized environment does not change significantly by the addition of a thixotropic agent and other curing agents having a molecular weight of less than 220 g / mol.

  Furthermore, also in Example 13 using C11Z (molecular weight: 222.4 g / mol) as a curing agent, there is a relationship of ((S1-S2) / S1) × 100 <15, and the thermosetting resin composition after heat treatment It can be seen that the cured part has excellent resistance to high temperature, high humidity, and pressurized environment.

  On the other hand, Comparative Example 1 and Comparative Example 6 using 2P4MHZ (molecular weight: 188.2 g / mol) as a curing agent, Comparative Example 2 using 2MZ-A (molecular weight: 219.3 g / mol), 2P4MZ (molecular weight: Comparative Example 3 and Comparative Example 7 using 158.2 g / mol) Comparative Example 4 using 2PZ (molecular weight: 144.2 g / mol) Comparative Example 5 using 2MZ (molecular weight: 82.1 g / mol) As for all, the relationship of ((S1-S2) / S1) × 100> 15 is established, and the cured portion of the thermosetting resin composition after heat treatment has excellent resistance to high temperature, high humidity, and pressurized environments. I know you don't. The curing agents used in these examples are all curing agents having a molecular weight of less than 220 g / mol.

  In Examples 5 and 7, two types of curing agents, 2P4MZ (molecular weight: 158.2 g / mol) and 2MA-OK (molecular weight: 384.4 g / mol), are used. In Comparative Example 3 and Comparative Example 7, only 2P4MZ is used as the curing agent, and the adhesive strength of the cured part of the thermosetting resin composition is significantly deteriorated due to the high temperature and high humidity environment. By using 2MA-OK having a molecular weight of 220 g / mol or more in Example 7, a relationship of ((S1-S2) / S1) × 100 <15 was obtained, which was excellent for high temperature / high humidity / pressurized environment. It turns out that the thermosetting resin composition hardening part which has tolerance can be obtained.

  In Example 6, two types of curing agents of 2PZ (molecular weight: 144.2 g / mol) and 2MA-OK (molecular weight: 384.4 g / mol) are used. In Comparative Example 4, only 2PZ is used as the curing agent, and the adhesive strength of the cured part of the thermosetting resin composition deteriorates significantly due to high temperature, high humidity, and pressurized environment, whereas in Example 6, the molecular weight By using 2MA-OK of 220 g / mol or more, a relationship of ((S1-S2) / S1) × 100 <15 is established, and thermosetting has excellent resistance to high temperature, high humidity, and pressurized environments. It can be seen that a cured part of the conductive resin composition can be obtained.

  In Example 8, two kinds of curing agents of 2MZ (molecular weight: 82.1 g / mol) and 2MA-OK (molecular weight: 384.4 g / mol) are used. In Comparative Example 5, only 2MZ is used as the curing agent, and the adhesive strength of the cured part of the thermosetting resin composition is significantly deteriorated by high temperature, high humidity, and pressurized environment, whereas in Example 8, the molecular weight is reduced. By using 2MA-OK of 220 g / mol or more, a relationship of ((S1-S2) / S1) × 100 <15 is established, and thermosetting has excellent resistance to high temperature, high humidity, and pressurized environments. It can be seen that a cured part of the conductive resin composition can be obtained.

  Similarly to the above (5) in Example 1, the thermosetting resin compositions having the compositions shown in Tables 1 and 2 were kneaded with solder particles to produce a conductive paste, and the solder particles melted well after reflowing. It was confirmed that everything was integrated. Regarding the solder particle melting characteristics, in any of the conductive pastes of Examples 2 to 13 and Comparative Examples 1 to 7, the solder particles melted well and were completely integrated.

  According to the conductive paste provided by the present invention, it is possible to melt the solder particles contained in the conductive paste satisfactorily, and in addition, the thermosetting resin cured portion after the heat treatment is severe environment, particularly Excellent resistance to high temperature, high humidity and pressurized environment. Therefore, the conductive paste according to the present invention can provide high connection reliability.

Claims (13)

  A conductive paste comprising a thermosetting resin, a curing agent, an organic acid, and metal particles, the curing agent comprising a nitrogen compound having a molecular weight of 220 g / mol or more having an imidazole structure or an amino group, or both, And the electrically conductive paste in which this metal particle contains a solder particle.   The conductive paste according to claim 1, wherein the nitrogen compound is an isocyanuric acid adduct.   The ratio of the content of the curing agent and the organic acid with respect to the total content of the thermosetting resin, the curing agent and the organic acid is 0.50 to 20% by mass, respectively, and occupies the entire curing agent The electrically conductive paste of Claim 1 or 2 whose ratio of a nitrogen compound is 20 mass% or more.   The electrically conductive paste of any one of Claims 1-3 in which the said thermosetting resin contains an epoxy resin.   The electrically conductive paste of any one of Claims 1-4 in which the said organic acid contains glutaric acid or adipic acid.   The conductive paste according to any one of claims 1 to 5, wherein the conductive paste further contains a thixotropic agent.   The solder particles have a melting point of 240 ° C. or less, and the solder particles are Sn particles or Sn and a group consisting of Ag, Au, Bi, Cu, Ge, In, Sb, Ni, Zn, and Pb. The electrically conductive paste of any one of Claims 1-6 which is Sn alloy particle | grains containing at least 1 sort (s) of the metal selected.   The solder particles are Sn alloy particles containing Sn and at least one metal selected from the group consisting of Bi, In, and Zn, and the Sn alloy particles have a melting point of 200 ° C. or less. The conductive paste described in 1.   The electrically conductive paste of any one of Claims 1-8 in which the said metal particle contains at least 1 sort (s) of high melting point metal particle with melting | fusing point of 300 degreeC or more.   The conductive paste according to claim 9, wherein the refractory metal particles are at least one selected from the group consisting of Cu particles; Ag particles; and alloy particles containing at least one of Cu and Ag.   It is a component mounting board | substrate provided with a board | substrate electrode, an electronic component electrode, and the junction part interposed among these, This junction part is formed by heat-processing the electrically conductive paste of any one of Claims 1-10. The component mounting board.   A laminated electronic component comprising a first electronic component having a first electrode, a second electronic component having a second electrode, and a joint interposed between the first electrode and the second electrode A laminated electronic component in which the bonding portion is formed by heat-treating the conductive paste according to any one of claims 1 to 10.   A laminated substrate comprising: a first substrate having a first electrode; a second substrate having a second electrode; and a junction interposed between the first electrode and the second electrode, The laminated substrate in which the junction part is formed by heat-processing the electrically conductive paste of any one of Claims 1-10.