JP2010027300A - Conductive paste and manufacturing method of conductive paste, and multilayer wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste for filling a via-hole which is preferable from a point of reducing an environmental load since lead is not contained, and which has high connection reliability in the via-hole since there is no occurrence of a flaw in the via-hole after lamination on the multilayer circuit board, and in which resistance value of the via-hole can be reduced much and a binder resin is not contained. <P>SOLUTION: Unleaded solder particles having the melting point of 110 to 240°C, metal particulates having particulate diameter D<SB>90</SB>of 0.1 to 5 μm in which integrated amount of particle size distribution in the accumulated particle curve is 90%, and dispersion medium are contained in the conductive paste. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductive paste for filling a via hole to form a via, and more particularly to a conductive paste used for filling a via hole of a multilayer wiring board formed by stacking a plurality of wiring boards.

  Advances in the highly information-oriented society have led to faster information processing in electronic devices (higher operating frequency) and wider frequency bands for information communications (broadband). There is a need for a wiring board. Further, the wiring board material is required to have a low relative dielectric constant and dielectric loss tangent.

  As this high-density multilayer wiring board, a buildup multilayer board in which buildup layers made of a photosensitive epoxy resin are successively stacked above and below a core layer made of a glass epoxy board has been proposed since the 1990s. This build-up multilayer board is used in many electronic devices today because fine wiring is easier compared to conventional multilayer boards.

  However, in the build-up multilayer wiring board, the through-hole diameter and wiring interval of the core substrate are different from the via diameter and wiring interval of the build-up layer stacked above and below the core layer in order to ensure the insulation reliability of the substrate. In addition, there is a problem that the via wiring for connecting each layer is formed by copper plating, and the via cannot be formed on the via in the manufacturing process. Therefore, in the build-up multilayer wiring board, a limit has begun to appear in order to cope with the further higher density demanded in recent years.

  As a solution to these problems, a coreless all-layer IVH (Intermediate Via Hole) substrate that has a high degree of freedom in wiring design and excellent transmission characteristics has recently attracted attention. Via wiring for connecting each layer in the coreless all-layer IVH substrate is formed of a conductive paste composition. Therefore, it is possible to form a via-on-via structure and a pad-on-via structure in which a via is formed on the via, and sufficiently meet the recent demand for higher density.

  The conductive paste composition for filling via holes is generally composed of conductive particles, a resin and a solvent. The conductive paste composition for filling a via hole is produced by roughly kneading each of these components with a planetary mixer, kneading with a three roll, and defoaming with a planetary mixer.

  The conductive paste composition for filling via holes is roughly classified into a metal pressure contact paste and a metal diffusion paste. The metal pressure contact paste is intended to conduct electricity by contacting metal particles due to solvent volatilization, resin curing shrinkage, and lamination pressure. As the metal particles in the metal pressure contact paste, silver powder, copper powder, silver-coated copper powder or the like is used.

  The metal diffusion paste contains metal particles that melt at a temperature lower than the laminating temperature and diffuse into the copper foil, which is a conductor pattern, and the metal particles are diffused and alloyed by the solvent volatilization and laminating pressure to achieve conduction. is there. For this reason, high connection reliability can be expected in the metal diffusion paste.

  The metal particles used in the metal diffusion paste include eutectic solder (Sn / Pb: mp 183 ° C.), lead-free solder powder (for example, Sn / Ag / Cu: mp 220 ° C.), Sn plating (Sn: mp 232 ° C.) Cu A core, Sn plating Ag core, etc. can be mentioned. Among these, eutectic solder contains Pb and has a large environmental load, so it cannot be used. Sn-plated Cu core and Sn-plated Ag core are not preferred because of their high cost. Therefore, lead-free solder powder (lead-free solder particles) is often used as the metal particles used in the metal diffusion paste.

Patent Document 1 describes a wiring board having an insulating substrate, a conductor wiring layer, and a via-hole conductor. As the conductive paste for forming the via-hole conductor, in the example of Patent Document 1, a conductive paste containing silver-coated copper powder, Pb—Sn alloy, epoxy resin, and solvent is described. In the present invention, the molten tin component reacts with the copper component by heating during the production of the wiring board, and an intermetallic compound such as Cu ₃ Sn is generated. Further, it is described that the intermetallic compound can firmly bond the copper powder or between the copper powder and the conductor wiring layer to improve heat resistance and conductivity.

Patent Document 2 discloses a via hole containing a first alloy particle that is a lead-free solder particle, at least one second metal particle selected from the group consisting of Au, Ag, and Cu, and a binder resin. A conductive paste composition is described.
Japanese Patent No. 3187373 JP 2007-96120 A

  The conductive paste described in Patent Document 1 uses a lead-containing solder as a solder. Such a lead-containing solder has a problem because when the wiring board using the lead-containing solder is discarded, the lead may be eluted from the board and the groundwater may be contaminated, and the environmental load is large. . In addition, the electronic component goes backward in the direction of making Pb free.

  The paste described in Patent Document 2 uses a lead-free solder and is a paste containing a resin. However, from the standpoint of producing a higher performance wiring substrate, the conductive paste composition in the via is highly metal diffusion bonded and the resistance value of the via is required to be very low. Since the paste described in Document 2 contains a binder resin, there is still room for improvement in terms of reducing the resistance value of vias and improving heat dissipation.

  Therefore, the present invention is preferable from the viewpoint of reducing environmental load because it does not contain lead, and there is no defect in the via hole after lamination on the multilayer wiring board, the connection reliability of the via hole is high, and the resistance of the via hole is high. It is an object of the present invention to provide a conductive paste for filling a via hole that does not contain a binder resin and can have a very small value.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems are solved in specific lead-free solder particles, metal fine particles having a specific range of particle diameters, and a conductive paste containing a dispersion medium. The inventors have found that this can be solved, and have completed the following invention.
The first aspect of the present invention is a lead-free solder particle having a melting point of 110 ° C. or higher and 240 ° C. or lower, and a particle size D _{90 of} 90% in the cumulative particle size curve of the particle size distribution is 0.1 μm or more and 5 μm or less. A conductive paste containing metal fine particles and a dispersion medium.

  In 1st this invention, it is preferable that an electrically conductive paste contains an organometallic compound further. The organometallic compound decomposes during the heat treatment process to generate active metal atoms, which promotes low-temperature and short-time sintering between the metal fine particles.

  In the first aspect of the present invention, the organometallic compound is preferably a fatty acid metal salt. Furthermore, the fatty acid metal salt is preferably an organic metal compound (amine-coordinated fatty acid metal salt) obtained by reacting a tertiary fatty acid metal salt and / or a fatty acid metal salt with an amine compound. Alternatively, an organic metal compound obtained by reacting tertiary fatty acid metal silver and / or fatty acid metal silver with an amine compound is preferable. By using these preferred forms of organometallic compounds, active metal atoms can be generated by decomposition at a lower temperature.

  In the first aspect of the present invention, the mass ratio of the organometallic compound to the dispersion medium is preferably 0.25 or more and 10.0 or less. By adjusting to this range, it is possible to improve the printing specification and uniform dispersibility of the conductive paste and to be able to fire for a short time.

  In the first aspect of the present invention, the mass ratio of the metal fine particles to the organometallic compound is preferably 0.5 or more and 5 or less. By adjusting to this range, it can be fired for a short time. The conductivity of the obtained sintered body can be improved, and the quality of the sintered body can be prevented from becoming brittle.

  In the first invention, the lead-free solder particles are Sn, Sn-Ag, Sn-Cu, Sn-Sb, Sn-Bi, Sn-In, Sn-Zn, Sn-Ag-Cu, Sn-Ag- One or more types of lead selected from the group consisting of In, Sn-Ag-In-Bi, Sn-Zn-Bi, Sn-Ag-Bi, Sn-Ag-Cu-Bi, and Sn-Ag-Cu-Sb Non-containing solder particles are preferred. These lead-free solder particles are reliable in the effect of metal diffusion of tin.

In the first aspect of the present invention, metal fine particles are preferably a boiling point at atmospheric pressure is a metal fine particle ionization constant Ka was treated with 1.0 × 10 ^-5 or more organic acids at 200 ° C. or less. By using such fine metal particles treated with a predetermined organic acid, the surface of the fine metal particles treated with the organic acid increases the number of active metal atoms having a high energy state under low-temperature heating, thereby reducing the temperature for a short time. Sintering is possible.

  In the first aspect of the present invention, the organic acid is preferably an organic acid having 1 to 3 carbon atoms. By using such an organic acid, it is possible to prevent the organic matter from remaining after the decomposition of the molten salt and to prevent the sintering with highly active metal atoms.

  In the first invention, the metal fine particles are preferably silver and / or copper fine particles, and more preferably silver fine particles. Thereby, resistance of the sintered compact obtained after heat processing can be made low.

  In the first invention, the dispersion medium is preferably at least one selected from the group consisting of an aromatic solvent, an ether solvent, a glycol ether solvent, an acetate ester solvent, and a saturated hydrocarbon solvent. . These dispersion media can maintain the dispersion stability and chemical stability of the conductive paste without reacting with materials such as metal fine particles used in the conductive paste.

  2nd this invention is a manufacturing method of the electrically conductive paste of 1st this invention characterized by including the dispersion | distribution process. The conductive paste of the first aspect of the present invention can be easily manufactured by simply dispersing a predetermined material with a dispersing device.

  The second aspect of the present invention preferably includes a step of adding and dispersing the metal fine particles to the dispersion medium and then adding and dispersing the organometallic compound as the dispersion step. If the metal fine particles are dispersed in the dispersion medium in the presence of the organometallic compound, the organometallic compound increases the viscosity in the system and reduces the dispersibility of the metal fine particles. As a result, a non-uniform location is generated in the sintered body, which may cause defects. Such a problem can be prevented by including the step of adding the organometallic compound and dispersing it again.

  The third aspect of the present invention is a multilayer wiring board having a conductive portion formed by filling a via hole with the conductive paste of the first aspect of the present invention. Since the multilayer wiring board of the present invention is formed using the conductive paste of the first present invention, the resistance value of the via hole is very small, and the moisture absorption heat resistance, connection reliability, and conductor adhesive strength are excellent. It is a thing.

  Since the electrically conductive paste of this invention does not contain lead, it is preferable from the point which reduces environmental impact. Further, the lead-free solder component is highly metal diffusion bonded between the metal fine particles and the metal forming the conductor pattern, and the metal fine particles having a particle size larger than the metal nanoparticles are also sintered together. As a result, the multilayer wiring board using the conductive paste of the present invention can have a very small resistance value of the via hole, and has excellent moisture absorption heat resistance, connection reliability, and conductor adhesive strength. can do.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

[Conductive paste]
The conductive paste of the present invention contains lead-free solder particles, metal fine particles, and a dispersion medium. Furthermore, an organometallic compound may be included.

<Lead-free solder particles>
The lead-free solder particles used in the present invention are lead-free solder particles having a melting point of 110 ° C. or higher and 240 ° C. or lower. Examples of such lead-free solder particles include Sn, Sn—Ag, Sn—Cu, Sn—Sb, Sn—Bi, Sn—In, Sn—Zn, Sn—Ag—Cu, and Sn—Ag—In. , Sn-Ag-In-Bi, Sn-Zn-Bi, Sn-Ag-Bi, Sn-Ag-Cu-Bi, and Sn-Ag-Cu-Sb. Further, the composition and melting point of these lead-free solder particles are described below.

  Sn (232 ° C), SnAg3.5 (221 ° C), SnCu0.7 (227 ° C), SnSb5 (232-240 ° C), SnBi58 (138 ° C), SnIn52 (118 ° C), SnZn9 (199 ° C), SnAg4Cu0. 5 (217-224 ° C), SnAg3.9Cu0.6 (217-223 ° C), SnAg3Cu0.5 (217-220 ° C), SnAg3.5Cu0.9 (217 ° C), SnAg3.8Cu0.7 (217-218 ° C) ), SnAg2.8In20 (175-187 ° C), SnZn8Bi3 (191-198 ° C), SnAg3.4Bi4.8 (201-215 ° C), SnAg2Bi7.5 (191-216 ° C), SnAg1Bi57 (137-139 ° C), SnAg2.5Cu0.5Bi1 (214-221 ° C.), SnAg Cu0.75Bi3 (207-218 ° C), SnAg2.5Cu0.8Sb0.5 (217-225 ° C), SnAg0.2Cu2Sb0.8 (219-235 ° C), SnAg3.5In4Bi0.5 (210-215 ° C), SnAg3. 5In8Bi0.5 (197-208 ° C.). In addition, the number after each said element represents the composition (mass%) of this element. The composition of Sn is other than the other components. For example, in “SnAg3.5”, Sn is 96.5% by mass and Ag is 3.5% by mass.

These lead-free solder particles are reliable in the effect of metal diffusion of tin. A mixture of two or more of these lead-free solder particles can also be used.
The average particle size of the lead-free solder particles is preferably 20 μm or less, and more preferably 10 μm or less. By setting it as such a particle size, it becomes easy to fill the conductive paste into the via hole, and metal diffusion is likely to occur.

<Metal fine particles>
The particle size of the metal fine particles according to the present invention is the particle size at D ₉₀ when the cumulative amount occupies 90% in the cumulative particle size curve in the particle size distribution.

The metal fine particles used in the present invention have a particle diameter D _{90 of} 90% or more in the cumulative particle size curve of the particle size distribution is 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more. . If the particle diameter D ₉₀ of the metal fine particles is too small, the surface activity is too high and it is necessary to coat with a strong dispersant, and because the coating is stabilized by the coating of the dispersant, the coating dispersant is difficult to be detached during low-temperature firing. There is a risk of low temperature short time sintering. The upper limit of the particle diameter D ₉₀ of the metal fine particles is at 5μm or less, preferably 2μm or less, more preferably 1μm or less. If the particle diameter D ₉₀ of the metal fine particles is too large, the metal fine particles are precipitated in the conductive paste, making it difficult to form a uniform conductive paste, resulting in poor dispersion stability.

Further, the metal type of the metal fine particles according to the present invention is not particularly limited, but considering the reduction in resistance after the heat treatment of the conductive paste, noble metals such as copper, silver, palladium, platinum are preferable, and silver, copper Is preferable, and silver is particularly preferable. The metal fine particles may be composed of an alloy of two or more of these metals, or may be a mixture of two or more metal fine particles. Moreover, the core-shell type fine particle which coat | covered the surface of the metal fine particle with the other metal may be sufficient. Specific examples include a mixture of silver fine particles and copper fine particles, silver / copper alloy fine particles, and core-shell type fine particles in which the surface of the silver fine particles is coated with copper.
The metal fine particles may be metal compound fine particles. As the metal compound fine particles, metal oxide fine particles such as silver oxide, copper oxide, palladium oxide and platinum oxide are preferable, and among them, silver oxide and copper oxide fine particles are preferable.

(Organic acid-treated fine metal particles)
The metal fine particles according to the present invention are preferably metal fine particles treated with a predetermined organic acid (hereinafter sometimes referred to as organic acid-treated metal fine particles). By using such fine metal particles treated with a predetermined organic acid, the surface of the fine metal particles treated with the organic acid increases the number of active metal atoms having a high energy state under low-temperature heating, thereby reducing the temperature for a short time. Sintering is possible. More specifically, under low temperature heating, a molten salt is formed from positively charged atoms and organic acid anions on the surface of the metal fine particles, and the molten salt is reductively pyrolyzed to form highly active metal atoms, thereby Low temperature and short time sintering is possible.

The organic acid-treated metal fine particles of the present invention are obtained by treating metal fine particles with an organic acid having a boiling point of 200 ° C. or less under normal pressure and an ionization constant Ka of 1.0 × 10 ⁻⁵ or more. Specifically, the metal fine particles are supported on the organic acid, or are washed with an organic solvent after the support.

When the ionization constant Ka of the organic acid is smaller than 1.0 × 10 ⁻⁵ , it is difficult to form a molten salt for forming the above-described highly active metal atoms in the heat treatment process. In addition, when the boiling point of the organic acid under atmospheric pressure is higher than 200 ° C., the organic matter remains after the molten salt is decomposed, which causes a problem that the above-described high active metal atoms impede the sintering. Arise.

The boiling point of the organic acid under normal pressure is preferably 150 ° C. or lower, more preferably 120 ° C. or lower. The ionization constant Ka of the organic acid is preferably 5.0 × 10 ⁻⁵ or more, more preferably 7.0 × 10 ⁻⁵ or more. In addition, if the organic acid has an excessively large number of carbon atoms, the organic matter tends to remain after decomposition of the molten salt, which becomes an obstacle to sintering due to the above-described highly active metal atoms. Organic acids are preferred.

  The molecular formula, melting point, boiling point under normal pressure, and ionization constant Ka of the organic acid suitable for the present invention are shown below, but the organic acid that can be used in the present invention is not limited to the following. Of these organic acids, formic acid and trifluoroacetic acid are preferred, and formic acid is more preferred. In addition, an organic acid may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  The method for obtaining the organic acid-treated metal fine particles by treating the metal fine particles with the organic acid described above is not particularly limited, but after stirring and mixing the organic acid and the metal fine particles, and separating the excess organic acid from the metal fine particles, A method in which the metal fine particles are dried or washed with an organic solvent is preferred. In this treatment method, stirring, mixing, and separation may be repeated before drying or washing with an organic solvent. In this treatment method, a solution obtained by mixing a solvent in which an organic acid is dissolved and an organic acid may be used. In this case, the amount of organic acid supported on the metal fine particles can be adjusted by adjusting the concentration of the solution.

  In the treatment method with an organic acid, means for stirring, mixing, and separation are not particularly limited. As the drying means, natural drying, natural drying in an inert gas atmosphere such as nitrogen gas, room temperature vacuum drying, and the like are preferable. In the drying means, mechanical pulverization means may be used in combination. The amount of organic acid supported on the metal fine particles can be adjusted by adjusting the drying time, the degree of vacuum, etc. in the drying means.

  In addition, in the case of washing with an organic solvent after supporting an organic acid, examples of the organic solvent to be used include ketone solvents such as acetone, cyclohexanone and inphorone, tetrahydrofuran (THF), 1,4-dioxane, diethyl ether, dimethoxyethane, An ether solvent such as diisopropyl ether, an alcohol solvent such as ethanol, propanol and butanol, a glycol ether solvent such as ethyl cellosolve and butyl cellosolv, or a mixed solvent of two or more of these organic solvents can be used.

  Examples of such a washing method using an organic solvent include a method in which metal fine particles carrying an organic acid and an organic solvent are mixed and stirred, followed by solid-liquid separation, followed by drying. The amount of organic solvent used for washing is arbitrary. In addition, when washing the fine metal particles after supporting the organic acid with an organic solvent, as described above, the organic acid and the fine metal particles may be stirred, mixed, separated, dried and then washed with the organic solvent. Although it may be washed with an organic solvent without drying, it is efficient to wash with an organic solvent without drying.

  In this washing method using an organic solvent, means for stirring, mixing, and separation are not particularly limited, but natural drying, room temperature vacuum drying, and the like are preferable as the drying means. In the drying means, a mechanical pulverization means may be used in combination. Adjusting the amount of organic acid supported on the metal fine particles by appropriately adjusting the type, amount used, cleaning method, washing time, etc. of the organic solvent when washing the metal fine particles after supporting the organic acid with such an organic solvent can do.

  As another method of the organic acid treatment in the present invention, there is a method in which metal fine particles are exposed to vapor of an organic acid. In this method, the amount of organic acid supported on the metal fine particles can be adjusted by adjusting the partial pressure of the organic acid and the exposure time. Also in this case, after the carrying treatment, washing with an organic solvent may be performed as described above.

  Metal fine particles treated with an organic acid can be obtained by the above-described method. The amount of organic acid supported on the surface of the metal fine particles varies depending on the degree of the treatment. The amount of the organic acid supported on the metal fine particles is not particularly limited as long as it is an amount that can increase the number of highly active metal atoms that enables low-temperature sintering as described above.

  As described above, the surface of the metal fine particles treated with the organic acid can be sintered at a low temperature for a short time by increasing active metal atoms having a high energy state under low temperature heating. In this case, not only the metal fine particles with high active metal atoms increased under low-temperature heating, but also between the metal fine particles with high active metal atoms and the metal fine particles with few high active metal atoms increased. Low temperature sintering becomes possible by surface diffusion of active metal atoms.

  Therefore, when using the organic acid-treated metal fine particles of the present invention, a mixture containing the organic acid-treated metal fine particles of the present invention and metal fine particles not treated with an organic acid may be used. In this case, the metal fine particles not treated with the organic acid may be fine particles made of the same metal as the metal fine particles of the organic acid-treated metal fine particles, or may be different. In any case, in order to effectively exhibit the low temperature and short time sinterability by the organic acid-treated metal fine particles of the present invention, 10% by mass or more, preferably, based on the mass of all metal fine particles (100% by mass) Is preferably 20% by mass or more of organic acid-treated metal fine particles.

<Organic metal compound>
The conductive paste of the present invention preferably contains an organometallic compound. The organic metal compound is preferably a fatty acid metal salt that can be decomposed in the heat treatment process to generate an active metal atom, particularly a tertiary fatty acid metal salt that can be decomposed by low-temperature firing to generate an active metal atom. And / or those having a structure in which an amine compound is coordinated to a fatty acid metal salt obtained by reacting a fatty acid metal salt with an amine compound (hereinafter sometimes referred to as “amine-coordinated fatty acid metal salt”) are preferred. Since the active metal atom can be generated by decomposition at a lower temperature, the fatty acid metal salt obtained by reacting the tertiary fatty acid metal salt and / or the fatty acid metal salt with an amine compound is a fatty acid silver salt. Is preferred.

  Moreover, as a fatty acid which comprises the fatty acid metal salt which can be used in this invention, since an organic substance does not remain easily after decomposition | disassembly of a fatty acid metal salt, it is C5-C30, especially 7-20, especially 8-15. Specific examples are as follows.

(Primary fatty acid)
Hexanoic acid Octanoic acid Decanoic acid Dodecane (lauric) acid Tetradecane (myristic) acid Hexadecane (palmitine) acid Octadecane (stearin) acid

(Secondary fatty acid)
2-ethylbutyric acid 2-methylhexanoic acid 2-ethylhexanoic acid 2-propylpentanoic acid

(Tertiary fatty acid)
Pivalic acid Neoheptanoic acid Neononanoic acid Neodecanoic acid

  Among these, in the present invention, as described above, tertiary fatty acid metal salts, particularly tertiary fatty acid silver salts are particularly preferable. Therefore, tertiary fatty acid silver salts include silver pivalate, silver neoheptanoate, Examples thereof include neononanoic acid silver salt and neodecanoic acid silver salt. Of these, silver neodecanoate is particularly preferably used because it is decomposed at a low temperature and has little influence from remaining organic substances.

  Further, the amine compound to be reacted with the fatty acid metal salt is not particularly limited as long as it can react with the fatty acid metal salt, but, as in the case of the fatty acid metal salt, after the decomposition of the amine coordinated fatty acid metal salt. Since organic matter does not easily remain, 1, 2 and tertiary amines having 3 to 20 carbon atoms are preferable, and 1, 2 and tertiary amines having 5 to 10 carbon atoms are more preferable. Furthermore, a primary or secondary amine having 5 to 10 carbon atoms is more preferable from the viewpoint of the stability of the amine coordinated fatty acid metal salt to be formed. Specific examples include amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, isopentylamine, 2-methylbutylamine, dipropylamine, dibutylamine, dipentylamine, N-methylbutylamine and the like.

The amine-coordinated fatty acid metal salt according to the present invention is a molar ratio (fatty acid metal salt: amine compound) of the fatty acid metal salt and the amine compound, preferably 1: 2 to 1:20, more preferably 1: 2. It can be obtained by charging at ˜1: 10 and reacting by heating in an inert gas atmosphere. In the heating reaction under an inert gas atmosphere, when the unreacted amine compound is vaporized before the end of the reaction, the charged amount of the amine compound is set to be larger than the molar ratio of fatty acid metal salt to amine compound 1: 2. The unreacted amine compound is distilled off under reduced pressure after completion of the reaction. The heating temperature and the heating time may be appropriately adjusted according to the types of the fatty acid metal salt and the amine compound while keeping the generated organometallic compound within a range where it is not decomposed. Further, as described above, the amount of the amine compound charged is larger than the molar ratio of the fatty acid metal salt to the amine compound of 1: 2, and after the reaction is completed, the unreacted amine compound is distilled off under reduced pressure to obtain the amine-coordinated fatty acid metal salt. In the vacuum distillation when obtained, the degree of vacuum, the heating temperature and the heating time may be appropriately adjusted so that the produced amine-coordinated fatty acid metal salt is not decomposed.
In addition, the amine compound used in the reaction may be dehydrated by heating and refluxing with a dehydrating agent such as potassium hydroxide before the reaction.

  The heating temperature during the reaction between the fatty acid metal salt and the amine compound is preferably 30 ° C. or higher and 130 ° C. or lower, more preferably 40 ° C. or higher and 100 ° C. or lower, and the heating time is preferably 5 minutes or longer and 4 hours or shorter, more preferably. Is 15 minutes or more and 3 hours or less.

  The amine-coordinated fatty acid metal salt obtained by reacting as described above is particularly preferably one in which a fatty acid metal salt is two-coordinated with an amine compound. What has a fatty acid metal salt as a main component is preferable. Here, the main component includes 80% by mass or more, preferably 90% by mass or more, of amine-coordinated fatty acid metal salt in which the amine compound is 2-coordinated based on the whole organometallic compound (100% by mass). It means being.

  The active metal atoms generated by decomposition of these organometallic compounds in the heat treatment process are the same as the active metal atoms generated from the organic acid in the heat treatment process on the surface of the organic acid-treated metal fine particles of the present invention described above. is there. Therefore, the organometallic compound is effective as a component of the conductive paste of the present invention in that it promotes low-temperature and short-time sintering between the metal fine particles of the present invention. In addition, the active metal atoms generated by the decomposition of these organometallic compounds during the heat treatment process can fill the gaps in the sintered body layer formed by the organic acid-treated metal fine particles of the present invention at a low temperature. . Thereby, a denser sintered body layer is formed. Therefore, the organometallic compound is also effective as a component of the conductive paste of the present invention in that it can achieve good electrical conductivity.

In the conductive paste of the present invention, these organometallic compounds may be used alone or in combination of two or more. In the conductive paste of the present invention, a general dispersant may be used in combination with the above-described organometallic compound. In this case, the following dispersants can be used in combination with the organometallic compound. Can be used.
BYK-Chemie's dispersant BYK series, sorbitan derivatives represented by sorbitan monolaurate (SPAN series, Tween series), anionic surfactants (sulfonic acid type, carboxylic acid type), cationic surfactants (4 Quaternary ammonium salts), alkylamines, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, polyacrylonitrile, polypyridine, polystyrene sulfonic acid, hydroxypropylcellulose, or copolymers thereof. One of these dispersants that can be used in combination may be used alone, or two or more thereof may be mixed and used.

  In the conductive paste of the present invention, the content ratio of the metal fine particles and the organometallic compound (metal fine particles / organometallic compound) is preferably 0.5 to 5 and more preferably 1 to 3 in terms of mass ratio. . If the content ratio of the organometallic compound is larger than this range, it takes time for the thermal decomposition, which prevents short-time firing. Or the organic component which remain | survives in sintered bodies, such as a sintered film after baking, will increase, and will prevent electroconductivity. On the other hand, if the content ratio of the metal fine particles is larger than this range, the film quality of the sintered body such as the sintered film becomes brittle and the adhesion to the substrate is lowered.

  In addition, in the case of mixing and using the above-described dispersant that can be used together with the organometallic compound, in order to reduce the amount of organic components remaining in the sintered body such as the sintered film after firing, so as not to impede the conductivity extremely In addition, the content ratio of the dispersant that can be used in combination with the organometallic compound is preferably in the range of the dispersant / organometallic compound that can be used in combination of 0.001 to 0.5 in terms of mass ratio.

<Dispersion medium>
The dispersion medium used in the conductive paste according to the present invention reacts with lead-free solder particles, metal fine particles (or organic acid-treated metal fine particles), an organic metal compound used as necessary, and the dispersant that can be used in combination. Without being particularly limited, the dispersion stability and chemical stability of the conductive paste can be maintained. Examples of the dispersion medium include ketone solvents such as cyclohexanone and isophorone, glycol ether solvents such as ethyl cellosolve and butyl cellosolve, hexylamine, octylamine, dipropylamine, dibutylamine, dioctylamine, N-methylbutylamine, triethylamine, Amine solvents such as trioctylamine, saturated hydrocarbon solvents such as n-hexane, n-heptane, n-octane and n-decane, aromatic solvents such as toluene and xylene, THF, dibutyl ether, diisopropyl ether, etc. And ether solvents such as ethyl acetate, ethyl acetate, butyl acetate, propyl acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. Among them, aromatic solvents, ether solvents, glycol ether solvents, acetate ester solvents, and saturated hydrocarbon solvents are preferable in order to impart good print properties in conductive pastes such as thixotropic properties. Of these, glycol ether solvents and acetate ester solvents are particularly preferred for the chemical stability of the conductive paste.

  In the case of an amine solvent, the dehydration operation may be performed by heating and refluxing together with a dehydrating agent such as potassium hydroxide before producing the conductive paste. Also preferred are those having good boiling point and evaporation rate of the solvent, rheological properties of the conductive paste, and wettability to the substrate. For this purpose, isophorone, ethyl cellosolve, hexylamine, octylamine, dipropylamine, N -Methylbutylamine is preferred. These dispersion media may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  It is preferable that the content rate of the dispersion medium in the electrically conductive paste of this invention is a content rate which can prepare the electrically conductive paste of the following solid content concentration. That is, the solid content concentration of the conductive paste of the present invention is to obtain the dispersion stability of the conductive paste, and to obtain a coating film having a uniform film thickness and uniform film quality using the conductive paste. The solid content concentration when the total amount of the metal fine particles, the organometallic compound used as necessary, and the dispersant that can be used in combination is defined as the solid content is preferably 50% by mass or more and 95% by mass or less, and 60% by mass. % To 90% by mass is more preferable. Therefore, the amount of the dispersion medium used is adjusted so as to achieve such a solid content concentration.

  As will be described later in the method for producing a conductive paste, metal fine particles, a dispersion medium, and an organometallic compound used as necessary are first mixed to form a metal fine particle composition. From the viewpoint of dispersibility of the metal fine particles, it is preferable that lead-free solder particles are mixed with the fine particle composition to form a conductive paste composition. From this point of view, the solid content in the above range of the amount of the dispersion medium used is one excluding lead-free solder particles.

  In the conductive paste of the present invention, the content ratio of the organometallic compound to the dispersion medium (organometallic compound / dispersion medium) is preferably 0.25 to 10.0, more preferably 0.00. 35 or more and 8.0 or less. If the content ratio of the dispersion medium is larger than this range, the time required for volatilization of the dispersion medium at the time of firing becomes longer, which impedes firing for a short time and is one of good printing characteristics of the conductive paste. The thixotropy is impaired. On the other hand, if the content ratio of the organometallic compound is larger than this range, the time required for the thermal decomposition of the organometallic compound becomes longer, which impedes short-time firing, and the dispersibility of the metal fine particles and the organometallic compound is reduced. It becomes worse and the uniform dispersibility of the conductive paste is impaired.

  In the conductive paste of the present invention, the blending ratio of lead-free solder particles and metal fine particle composition (metal fine particles + dispersion medium + preferably organometallic compound) (lead-free solder particles / metal fine particle composition) is: The mass ratio is preferably 80/20 to 20/80, more preferably 70/30 to 30/70, and particularly preferably 60/40 to 40/60. If it is out of the above range, printability may be deteriorated or diffusion bonding of the conductor pattern with the metal may be poor.

[Method for producing conductive paste]
As a method for producing the conductive paste of the present invention, the lead-free solder particles, metal fine particles, a dispersion medium, the organometallic compound used as necessary, and the dispersing agent that can be used in combination are mixed and dispersed to be uniform. There is no particular limitation as long as it is a method of processing into a conductive paste. Specific examples include a method using a ball mill, jet mill, Eiger mill, paint shaker, homogenizer, ultrasonic homogenizer, roll mill, kneader, kneader and the like.

  In order to improve the dispersibility of the metal fine particles, first, the metal fine particles, the dispersion medium, the organometallic compound used as necessary are mixed and dispersed to form a metal fine particle composition, and then the metal. A method of mixing the fine particle composition and lead-free solder particles is preferable in the present invention.

  In particular, the method for producing a conductive paste according to the embodiment of the present invention containing an organometallic compound includes a dispersion step in which the metal fine particles are added and dispersed in a dispersion medium, and then the organometallic compound is added and dispersed again. It is preferable that That is, when the metal fine particles of the present invention are dispersed in a dispersion medium in the presence of an organometallic compound, the organometallic compound increases the viscosity in the system, thereby reducing the dispersibility of the metal fine particles of the present invention. There is a problem that a film defect occurs, for example, a protrusion derived from an aggregate of metal fine particles is seen in the formed sintered film. Therefore, it is preferable to disperse the metal fine particles in the dispersion medium in advance and then add the organometallic compound to further disperse.

[Multilayer wiring board]
Next, a multilayer wiring board using the conductive paste of the present invention will be described. The insulating material used for the multilayer wiring board is not particularly limited, and a thermoplastic resin composition such as a mixed composition of a polyaryl ketone resin and an amorphous polyetherimide resin described later, a liquid crystal polymer, a thermoplastic polyimide resin, or the like. Or a thermosetting resin composition made of epoxy resin, BT resin or thermosetting polyimide resin impregnated with glass cloth or aramid fiber, or ceramic made of alumina or low temperature fired ceramic (LTCC) can be used.

  Among the above, in order to promote metal diffusion bonding, the relationship between the lead-free solder particles in the conductive paste and the insulating material made of the thermoplastic resin composition is important, and in the melting point of the lead-free solder particles It is preferable to use a thermoplastic resin composition having a storage elastic modulus of 10 MPa or more and less than 7 GPa. The storage elastic modulus of the thermoplastic resin composition is a value measured using a viscoelasticity evaluation apparatus at a measurement frequency of 1 Hz and a temperature increase rate of 3 ° C./min.

  It is assumed that the thermoplastic resin composition has a storage elastic modulus of 10 MPa or more and less than 7 GPa so that the thermoplastic resin composition has some flexibility and does not melt at the melting point of the lead-free solder particles. This means that a certain degree of elastic modulus is maintained.

  In FIG. 1, the outline of the manufacturing method of the multilayer wiring board using the electrically conductive paste of this invention is shown. As described above, at the melting point of the lead-free solder particles, the thermoplastic resin composition does not melt and retains a certain degree of elastic modulus, so that the conductive properties when the wiring board 100 is laminated by thermal fusion are as follows. The paste can be clamped by the thermoplastic resin composition that is the side surface of the via hole 30, and pressure can be applied to the conductive paste. Thereby, it is considered that the tin component in the lead-free solder particles can diffuse into the metal forming the metal fine particles and / or the conductor pattern 20 to form a metal diffusion bond.

  From the above viewpoint, it is preferable to use a mixed composition of a polyaryl ketone resin and an amorphous polyetherimide resin. When a mixed composition of polyetheretherketone and amorphous polyetherimide is used as the thermoplastic resin composition constituting the insulating material, as shown in FIG. 2, lead free from 130 ° C. to 240 ° C. The storage elastic modulus of the thermoplastic resin composition at the melting point of the solder particles is 10 MPa or more and less than 7 GPa.

<Insulating base material 10 made of thermoplastic resin composition>
The thermoplastic resin composition forming the insulating substrate 10 made of a thermoplastic resin composition is a mixture of a polyaryl ketone resin and an amorphous polyetherimide resin having a crystal melting peak temperature (Tm) of 260 ° C. or higher. It is preferable to use a composition. Note that the polyaryl ketone resin and the amorphous polyetherimide resin are compatible systems, and these mixed compositions have one crystal melting peak temperature. That is, in the above, it means that one crystal melting temperature of the mixed composition of the polyaryl ketone resin and the amorphous polyetherimide resin is 260 ° C. or higher.

  This polyaryl ketone resin is a thermoplastic resin having an aromatic nucleus bond, an ether bond and a ketone bond in its structural unit, and representative examples include polyether ketone, polyether ether ketone, polyether ketone ketone, etc. Of these, polyetheretherketone is preferred. Polyether ether ketone is commercially available as “PEEK151G”, “PEEK381G”, “PEEK450G” (all are trade names of VICTREX), and the like.

  The amorphous polyetherimide resin is an amorphous thermoplastic resin containing an aromatic nucleus bond, an ether bond and an imide bond in the structural unit, and is not particularly limited. Polyetherimide is commercially available as “Ultem CRS 5001”, “Ultem 1000” (both are trade names of General Electric).

  The mixing ratio of the polyaryl ketone resin and the amorphous polyetherimide resin is 30% by mass or more and 70% by mass or less of the polyaryl ketone resin in consideration of adhesion to the other wiring boards 100a and 300 to be laminated. It is preferable to use a mixed composition containing an amorphous polyetherimide resin and inevitable impurities. Here, the reason why the content of the polyaryl ketone resin is limited to 30% by mass or more and 70% by mass or less is that when the content of the polyaryl ketone resin is too high, the crystallinity of the thermoplastic resin composition is high. This is because the lamination property at the time of multilayering is lowered, and if the content of the polyaryl ketone resin is too low, the crystallinity itself of the thermoplastic resin composition as a whole is lowered, and the crystal melting peak temperature is 260 ° C. It is because reflow heat resistance falls even if it is above.

  This thermoplastic resin composition may contain an inorganic filler. There is no restriction | limiting in particular as an inorganic filler, Any well-known thing can be used. Examples thereof include talc, mica, mica, glass flake, boron nitride (BN), plate-like carbon cal, plate-like aluminum hydroxide, plate-like silica, and plate-like potassium titanate. These may be added singly or in combination of two or more. In particular, a scale-like inorganic filler having an average particle size of 15 μm or less and an aspect ratio (particle size / thickness) of 30 or more can keep the linear expansion coefficient ratio in the plane direction and the thickness direction low, and the thermal shock cycle test. This is preferable because generation of cracks in the substrate at the time can be suppressed.

  The added amount of the inorganic filler is preferably 20 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. This is because if the amount of the inorganic filler added is too large, a problem of poor dispersion of the inorganic filler occurs, and the linear expansion coefficient tends to vary or the strength tends to decrease. In addition, if the amount of the inorganic filler added is too small, the effect of reducing the linear expansion coefficient and improving the dimensional stability is small, which is caused by the difference in the linear expansion coefficient with the other wiring substrate 300 or the conductive pattern 20 in the reflow process. This is because internal stress is generated, and the substrate is warped and twisted.

  In addition, the thermoplastic resin composition has various additives other than other resins and inorganic fillers, such as a stabilizer, an ultraviolet absorber, a light stabilizer, a nucleating agent, a colorant, and a lubricant, to the extent that the properties are not impaired. In addition, flame retardants and the like may be appropriately contained. As a method of adding various additives including these inorganic fillers, a known method, for example, the following methods (a) and (b) can be used.

  (A) Various additives were mixed with a polyaryl ketone resin and / or an amorphous polyetherimide resin base material (base resin) at a high concentration (typically about 10 to 60% by mass). A method of preparing a master batch separately, adjusting the concentration of the master batch and mixing the resin, and mechanically blending it using a kneader or an extruder. (B) A method in which various additives are mechanically blended directly with a resin to be used using a kneader or an extruder. Among these methods, the method (a) is preferable from the viewpoint of dispersibility and workability. Further, the surface of the insulating base material 10 made of the thermoplastic resin composition may be appropriately subjected to corona treatment or the like for the purpose of improving the lamination property.

<The manufacturing method of the wiring board 100a provided with the insulating base material 10 which consists of a thermoplastic resin composition>
1A to 1E show a process for manufacturing a single-layer wiring board 100a. First, as shown to Fig.1 (a), the insulating base material 10 which consists of a thermoplastic resin composition is prepared. The insulating substrate 10 is preferably in the form of a film, a thin plate or a sheet. As a forming method, a known method such as an extrusion casting method using a T die or a calendar method can be adopted, and the method is particularly limited. However, an extrusion casting method using a T-die is preferable from the viewpoints of sheet formability and stable productivity. The molding temperature in the extrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film-forming properties of the resin used, but is generally polyaryl ketone resin and amorphous having a crystal melting peak temperature of 260 ° C. or higher. In the case of a mixed composition of a conductive polyetherimide resin, the temperature is 360 to 400 ° C. In addition, it is necessary to form an amorphous film by rapidly forming a film during extrusion casting. Thereby, since the area | region where an elasticity modulus falls in 170-230 degreeC vicinity is expressed, thermoforming and heat fusion in this temperature range are attained. Specifically, the elastic modulus starts to decrease at around 170 ° C., and thermoforming and heat fusion are possible at around 200 ° C. The graph shown in FIG. 2 is obtained by measuring the elastic modulus at a temperature rising rate of 3 ° C./min. When the temperature rising rate is 10 ° C./min, the transition from amorphous to crystalline is delayed. In the vicinity of 230 ° C., the elastic modulus is the lowest.

  Subsequently, as shown in FIG.1 (b), metal foil is affixed on the surface of the insulating base material 10 which consists of a thermoplastic resin composition. As described above, since the insulating base material 10 made of the thermoplastic resin composition is in an amorphous state, the crystallization of the thermoplastic resin does not proceed greatly, and it takes a relatively short time at a temperature slightly above the glass transition temperature. Thus, the metal foil can be attached without causing crystallization of the insulating base material. Further, when forming the insulating base material 10, a metal foil may be laminated at the same time to obtain the stage shown in FIG. An example of the metal foil is a copper foil.

  Next, as shown in FIG. 1C, a via hole 30 is formed at a predetermined position of the insulating base 10 using a laser or a mechanical drill. Next, a conductor pattern 20 is formed as shown in FIG. 1D by a normal method such as applying a resist to the surface of the metal foil in a circuit pattern, etching, and removing the resist. In addition, after forming the via hole 30, the copper foil may be attached to form the conductor pattern 20, or the conductor pattern 20 may be formed and then the via hole 30 may be formed. Is not particularly limited. Next, via holes 30 are formed by filling the via holes 30 with a conductive paste by vacuum printing to form a single-layer wiring board 100a as shown in FIG.

<Behavior of elastic modulus with respect to temperature of insulating substrate 10 made of thermoplastic resin composition>
Here, the behavior of the elastic modulus with respect to the temperature of the insulating substrate 10 made of the thermoplastic resin composition will be described. As a thermoplastic resin composition, a mixed composition of a polyaryl ketone resin and an amorphous polyetherimide resin having a crystal melting peak temperature (Tm) of 260 ° C. or higher, particularly a polyether as a polyaryl ketone resin FIG. 2 shows the behavior of the elastic modulus with respect to temperature of the insulating base material 10 when ether ketone is used.

  “Before lamination” is a graph showing the behavior of the elastic modulus with respect to the temperature of the insulating base material 10 before lamination as the multilayer wiring board 200. Also, “after lamination” is displayed as a graph showing the behavior of the elastic modulus with respect to the temperature of the insulating base material 10 after the multilayer wiring board 200 is formed by heating and pressurizing under predetermined conditions. . In the state before lamination, as described above, the insulating base material 10 is formed into an amorphous film by rapid cooling. Therefore, the elastic modulus is sufficiently lowered in a relatively low temperature region of around 200 ° C. Thereby, the insulating base material 10 before lamination can be thermoformed and heat-sealed at a relatively low temperature.

  The insulating base material 10 formed into an amorphous film changes into a crystalline film by heating and pressure molding under predetermined conditions when the multilayer wiring base material 200 is manufactured. Along with this, the elastic modulus of the insulating base material 10 changes greatly, and the behavior as shown in the graph after lamination in FIG. 2 is exhibited. As a result, the effect of promoting metal diffusion bonding is exhibited, and the resistance value of the via hole of the multilayer wiring board 200 can be made extremely small, and the moisture absorption heat resistance, connection reliability, and conductor adhesive strength are excellent. It is believed that

<Method for Manufacturing Multilayer Wiring Board 200>
1E to 1G show the manufacturing process of the multilayer wiring board 200a. As shown in FIG. 1F, a plurality of produced single-layer wiring boards 100a are overlapped. In the illustrated form, three single-layer wiring boards 100a are overlaid. In addition, the lowermost substrate is superposed in a different direction so that the conductor pattern 20 is formed outside the multilayer substrate. Specifically, as shown in FIG. 3, the cushioning film 51, which has three cushion films 51 and wiring bases 100 a having elasticity and releasability from the lower side, in the laminated jig 50 with a built-in heater, are formed thereon. After that, the pressing jig 52 is pushed down in the direction of the arrow shown in the drawing, so that the three wiring base materials 100a are thermocompression bonded, and these are laminated and integrated to form the multilayer wiring board 200a. As the lamination conditions of each layer, from the viewpoint of effectively causing metal diffusion bonding, it is preferable that the temperature is 150 ° C. or more and less than 260 ° C., the pressure is 3 MPa or more and less than 8 MPa, and the press time is 10 minutes or more and less than 40 minutes. The lamination temperature is preferably equal to or higher than the melting point of the lead-free solder particles.

  1 (h) to (l) show a multilayer structure in which a wiring board 100b provided with an insulating base material 10 made of a thermoplastic resin composition and a wiring board 300 made of a material other than the thermoplastic resin composition are alternately stacked. It is the figure which showed the process of manufacturing the wiring board 200b. First, as shown in FIG.1 (h), the insulating base material 10 which consists of a thermoplastic resin composition is prepared. The molding method is the same as in the case of FIG. Next, as shown in FIG. 1 (i), a via hole 30 is formed at a predetermined position of the insulating substrate 10 using a laser or a mechanical drill. Then, a conductive paste is filled in the formed via hole 30 by vacuum printing, and a single-layer wiring board 100b in which the via 40 as shown in FIG. 1J is formed is manufactured.

  Next, as shown in FIG. 1 (k), the manufactured single-layer wiring board 100b and the wiring board 300 made of a material other than the thermoplastic resin composition different from the wiring board 100b are alternately stacked. In the illustrated embodiment, the wiring board 300 made of a material other than the thermoplastic resin is disposed on both sides of the wiring board 100b in the middle.

  Then, under predetermined conditions, the layers are heat-sealed to produce a multilayer wiring board 200b as shown in FIG. The lamination method and lamination conditions are the same as the method and conditions shown in FIG.

  In addition, in the manufacturing method shown to Fig.1 (a)-(g), the conductor pattern 20 is formed in the single side | surface of the single layer wiring board 100a, and also shown to FIG.1 (h)-(l). In the manufacturing method, the conductor pattern 20 is formed on both surfaces of the wiring board 300 made of a material other than the thermoplastic resin composition without forming the conductor pattern 20 on the single-layer wiring board 100b, but the multilayer wiring board 200a to be manufactured is formed. As long as the conductor pattern 20 is formed at a desired position in 200b, the position where the conductor pattern is formed in the single-layer wiring boards 100a, 100b, 300 is not particularly limited, and can be changed as appropriate.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not restrict | limited at all by these Examples.

Example 1
Silver fine particles (manufactured by Mitsui Kinzoku Co., Ltd., particle diameter D ₉₀ = 0.5 μm) and formic acid (purity 98-100%) were mixed and stirred at a weight ratio of 1: 1.2, and then formic acid was removed by centrifugation. . Thereafter, acetone having the same volume as formic acid was added, mixed and stirred, and then the acetone was removed by centrifugation, followed by drying in a nitrogen atmosphere to produce formic acid-treated silver fine particles.

  10.5 g of ethyl cellosolve as a dispersion medium was added to 19 g of the formic acid-treated silver fine particles, and the mixture was dispersed with an ultrasonic homogenizer for 30 minutes. Thereafter, 12.6 g of neodecanoic acid silver salt (manufactured by Wako Pure Chemical Industries, Ltd.), which is a tertiary fatty acid silver salt, was added and the touch mixer was applied for 10 minutes. Thereafter, an ultrasonic homogenizer was applied for 10 minutes. Here, the solid content concentration of the formic acid-treated silver fine particles and neodecanoic acid silver salt with respect to ethyl cellosolve in the prepared silver fine particle composition was 75.0% by weight, and the weight ratio of the solid content was formic acid-treated silver fine particles: neodecanoic acid silver salt = 1.5: 1. Moreover, the weight ratio (neodecanoic acid silver salt / ethyl cellosolve) of the neodecanoic acid silver salt and ethyl cellosolve in this silver fine particle composition is 1.2.

As the lead-free solder particles, SnAg3Cu0.5 (average particle size 5.6 μm) having a melting point of 217 to 220 ° C. was prepared.
A mixture of the above-mentioned silver fine particle composition and lead-free solder particles in a mass ratio of 60/40 (silver fine particle composition / lead-free solder particles) is roughly kneaded with a planetary mixer and then kneaded with three rolls. Further, defoaming with a planetary mixer, a conductive paste having a viscosity of 33 Pa · s (1 rpm) at 25 ° C. measured with a Brookfield viscometer DV-III spindle CP52 (angle 3.0 °, φ2.4 cm) Obtained.

  Next, as an insulating base material made of a thermoplastic resin, a polyether ether ketone resin (product name PEEK450G) and a polyetherimide resin (product name PEI Ultem 1000) are used in a mass ratio of 40/60 (polyether ether ketone / polyether imide). To 100 parts by mass of the blended resin mixture, 39 parts by mass of mica having an average particle size of 3.5 μm and an average aspect ratio of 50 as an inorganic filler was added and melt-kneaded, and this kneaded product was further extruded by a T-die extrusion casting method. The film was rapidly cooled to obtain a film having a thickness of 100 μm.

  The elastic modulus of this film at a melting point of 217-220 ° C. of SnAg 3 Cu 0.5 was 37 MPa under the conditions of 1 Hz and a temperature rising rate of 3 ° C./min. Moreover, the copper foil (thickness 12 micrometers) was laminated at the time of extrusion, and the single-sided copper clad board was produced besides the film.

  Next, a via hole having a hole diameter of 100 μm was formed at a predetermined position of the single-sided copper-clad plate using a laser. Next, as shown in FIG. 1D, a conductor evaluation pattern having a bottomed via hole is formed by applying a resist to the surface of the copper foil in a circuit pattern, etching, and removing the resist. A circuit processed substrate was prepared. Next, this via hole is filled with the conductive paste composition adjusted as described above using a vacuum printing method, and after filling, the solvent is volatilized at 125 ° C. for 45 minutes to form a via, as shown in FIG. A simple single-layer wiring board 100a was produced.

  Next, three single-layer wiring boards 100a thus produced were stacked with only the lowermost single-layer board being changed in its direction, and SnAg3Cu0.5 in the via had a melting point of 217-220 ° C. or higher and 240 ° C., 5 MPa 30 These were collectively laminated under the conditions of min. To obtain a 0.3 mm three-layer multilayer wiring board 200a.

(Example 2)
A multilayer wiring board was obtained in the same manner as in Example 1 except that a conductive paste was obtained with a silver fine particle composition and lead-free solder particles in a mass ratio of 40/60 (silver fine particle composition / lead-free solder particles). . The evaluation results are shown in Table 2.

(Example 3)
A multilayer wiring board was obtained in the same manner as in Example 1 except that the conductive paste was obtained as SnBi58 (average particle size 5.3 μm) having a melting point of 138 ° C. as lead-free solder particles in Example 1. The evaluation results are shown in Table 2.

(Comparative Example 1)
A multilayer wiring board was obtained in the same manner as in Example 1 except that the conductive paste was obtained without containing lead-free solder particles in Example 1. The evaluation results are shown in Table 2.

<Evaluation method>
The following evaluation was performed on the multilayer wiring board produced above. The respective evaluation results are shown in Table 2.
(Connection reliability)
The multilayer wiring board is dried at 125 ° C. for 4 hours. Then, after the heat treatment was repeated twice in a reflow oven having a peak temperature of 250 ° C. in a constant temperature and humidity chamber of 30 ° C. and 85% humidity, the following connection reliability test was performed.

Thermal shock test A cycle of 9 minutes at -25 ° C and 9 minutes at 125 ° C was repeated 1000 times.
The obtained multilayer wiring board was evaluated according to the following criteria. The resistance change rate is a value represented by “| resistance value before test−resistance value after test | / resistance value before test” × 100 (%).
○: Resistance change rate is less than 20%.
X: Resistance change rate is 20% or more.

(Conductor adhesive strength)
A wire was soldered to the conductor pattern portion exposed on the multilayer wiring board, the wire was pulled up, and the strength when the conductor pattern portion was peeled was measured.
A: The strength was 1 N / mm or more.
X: The strength was less than 1 N / mm.

  The multilayer substrate using the conductive paste composition of the present invention showed good results in all evaluations (Examples 1 to 3). On the other hand, in Comparative Example 1, since the lead-free solder particles are not contained, the conductive paste composition does not perform metal diffusion bonding with the conductor pattern, and shows inferior results in the thermal shock test and the conductor adhesive strength. It was.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, it can be changed as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a conductive paste, a manufacturing method of the conductive paste, and a multilayer wiring board that involve such a change Should also be understood as being included within the scope of the present invention.

It is the figure which showed the outline | summary of the manufacturing method of the multilayer wiring board 200 using the electrically conductive paste composition of this invention. It is the figure which showed a mode that the elasticity modulus of the specific thermoplastic resin composition which comprises the insulating base material 10 changes with temperature. It is a conceptual diagram of the lamination jig | tool 50 for manufacturing the multilayer wiring board 200 by thermocompression bonding the wiring board 100. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Insulation base material which consists of thermoplastic resins 20 Conductor pattern 30 Via hole 40 Via 100a, 100b Single layer wiring board 200a, 200b Multilayer wiring board 50 Lamination jig 51 Cushion film 52 Pressing jig

Claims (16)

Lead-free solder particles having a melting point of 110 ° C. or higher and 240 ° C. or lower, metal fine particles having a particle size D _{90 of} 90% in the cumulative particle size curve of the particle size distribution and 0.1 μm or more and 5 μm or less, a dispersion medium, Conductive paste containing. Furthermore, the electrically conductive paste of Claim 1 containing an organometallic compound. The conductive paste according to claim 2, wherein the organometallic compound is a fatty acid metal salt. The conductive paste according to claim 3, wherein the fatty acid metal salt is an organic metal compound obtained by reacting a tertiary fatty acid metal salt and / or a fatty acid metal salt with an amine compound. The conductive paste according to claim 3 or 4, wherein the fatty acid metal salt is a fatty acid silver salt. The conductive paste according to claim 2, wherein a mass ratio of the organometallic compound to the dispersion medium is from 0.25 to 10.0. The conductive paste according to claim 2, wherein a mass ratio of the metal fine particles to the organometallic compound is 0.5 or more and 5 or less. The lead-free solder particles are Sn, Sn—Ag, Sn—Cu, Sn—Sb, Sn—Bi, Sn—In, Sn—Zn, Sn—Ag—Cu, Sn—Ag—In, Sn—Ag—. One or more lead-free solder particles selected from the group consisting of In—Bi, Sn—Zn—Bi, Sn—Ag—Bi, Sn—Ag—Cu—Bi, and Sn—Ag—Cu—Sb The electrically conductive paste in any one of Claims 1-7. 9. The metal fine particles according to claim 1, wherein the metal fine particles are metal fine particles treated with an organic acid having a boiling point of 200 ° C. or less under normal pressure and an ionization constant Ka of 1.0 × 10 ⁻⁵ or more. Conductive paste. The conductive paste according to claim 9, wherein the organic acid is an organic acid having 1 to 3 carbon atoms. The conductive paste according to claim 1, wherein the metal fine particles are silver and / or copper fine particles. The conductive paste according to claim 1, wherein the metal fine particles are silver fine particles. The dispersion medium according to any one of claims 1 to 12, wherein the dispersion medium is at least one selected from the group consisting of an aromatic solvent, an ether solvent, a glycol ether solvent, an acetate ester solvent, and a saturated hydrocarbon solvent. The conductive paste described in 1. The manufacturing method of the electrically conductive paste in any one of Claims 1-13 characterized by including a dispersion | distribution process. The method for producing a conductive paste according to claim 14, wherein the dispersion step includes a step of adding metal fine particles to a dispersion medium to disperse, and then adding an organometallic compound to disperse again. A multilayer wiring board having a conductive portion formed by filling a via hole with the conductive paste according to claim 1.

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