JP5596524B2 - Conductor pattern forming ink, conductor pattern and wiring board - Google Patents

Description

  The present invention relates to a conductor pattern forming ink, a conductor pattern, and a wiring board.

As a circuit board (wiring board) on which electronic components are mounted, a ceramic circuit board in which wiring made of a metal material is formed on a board made of ceramics (ceramic board) is widely used. In such a ceramic circuit board, since the board (ceramic board) itself is made of a multifunctional material, it is advantageous in terms of formation of interior parts by multi-layering, dimensional stability, and the like.
Such a ceramic circuit board is provided with a composition containing metal particles in a pattern corresponding to a wiring (conductor pattern) to be formed on a ceramic molded body made of a material containing ceramic particles and a binder. Thereafter, the ceramic molded body to which the composition is applied is manufactured by degreasing and sintering.

  A screen printing method is widely used as a method for forming a pattern on a ceramic molded body. On the other hand, in recent years, miniaturization of wiring (for example, wiring with a line width of 60 μm or less) and high density circuit boards by narrowing the pitch have been demanded. It is disadvantageous for pitching and it is difficult to meet the above requirements. Therefore, in recent years, a so-called ink jet method has been proposed as a method for forming a pattern on a ceramic molded body, in which a liquid material containing metal particles (ink for forming a conductor pattern) is ejected in droplets from a liquid ejection head. (For example, refer to Patent Document 1). However, in the conventional conductor pattern forming ink, when the ceramic molded body is degreased and sintered, thermal breakage of the ceramic molded body may cause disconnection of a part of the formed conductor pattern. was there. In particular, the occurrence of such a problem has been remarkable with the recent increase in the density of circuit boards due to the miniaturization of wiring and the reduction in pitch. In particular, the occurrence of disconnection was remarkable in the outermost layer such as the surface layer.

  In addition, a droplet discharge device (for industrial use) used for forming a conductor pattern is completely different from that applied to a printer (for consumer use). For example, a large number of droplets are long for mass production. It is required to discharge continuously over time. Also, the ink used for forming the conductor pattern (industrial) is generally poorer in liquid discharge during ejection than the ink used in printers (consumer use), and the ejection part (nozzle) of the inkjet head. Ink tends to remain on the discharge surface. As a result, when the ink is continuously discharged, the components contained in the ink adhere to the ink flow path of the droplet discharge device, and the supply of ink to the droplet discharge head tends to become unstable. Also, the ink used for forming the conductor pattern (industrial) has more compositional restrictions than those used in printers (consumer use) and has sufficient characteristics such as drying and re-dissolvability. In other words, solid content such as metal particles precipitates or aggregates, and the discharge portion of the droplet discharge head is likely to be clogged, resulting in a problem that droplets are frequently bent.

JP 2007-084387 A

  An object of the present invention is to provide a conductive pattern forming ink that can form a highly reliable conductor pattern in which disconnection is prevented and has excellent droplet discharge stability, and a highly reliable conductor pattern. An object of the present invention is to provide a highly reliable wiring board having such a conductor pattern.

Such an object is achieved by the present invention described below.
The conductive pattern forming ink of the present invention is a conductive pattern forming ink used for forming a conductive pattern, which is applied to a ceramic molded body made of a material containing ceramic particles and a binder by a droplet discharge method. And
Metal particles,
An aqueous dispersion medium in which the metal particles are dispersed;
A water-soluble polysaccharide having a weight average molecular weight of 1,000 or more and 5,000 or less;
A polyglycerin compound having a polyglycerin skeleton,
The content of the polysaccharide in the conductor pattern forming ink is 1.0 wt% or more and 28 wt% or less,
The content of the polyglycerin compound in the conductive pattern forming ink is 1.0% by weight or more and 28% by weight or less,
The viscosity at 25 ° C. is 20 mPa · s or less.
Thereby, a highly reliable conductor pattern in which disconnection is prevented can be formed, and a conductor pattern forming ink excellent in droplet discharge stability can be provided.

In the conductive pattern forming ink of the present invention, the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%], and the content of the polysaccharide in the conductive pattern forming ink is X (B). When expressed as [wt%], it is preferable to satisfy the relationship of X (A) + X (B) ≦ 28.
As a result, the reliability of the formed conductor pattern can be made sufficiently high while the droplet discharge stability is particularly excellent.

In the conductive pattern forming ink of the present invention, the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%], and the content of the polysaccharide in the conductive pattern forming ink is X (B). It is preferable that the relationship of 7.5 ≦ X (A) + 4X (B) is satisfied when “wt%” is satisfied.
As a result, the dimensional accuracy and reliability of the formed conductor pattern can be made particularly excellent while the droplet ejection stability is sufficiently excellent.

In the conductive pattern forming ink of the present invention, the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%], and the content of the polysaccharide in the conductive pattern forming ink is X (B). It is preferable to satisfy the relationship of 0.12 ≦ X (A) / X (B) ≦ 12 when [wt%] is set.
Thereby, the discharge stability of the droplet and the reliability of the formed conductor pattern can be made particularly excellent.

In the conductive pattern forming ink of the present invention, it is preferable that maltodextrin that is solid at room temperature is included as the polysaccharide.
Thereby, the discharge stability of the droplet and the reliability of the formed conductor pattern can be made particularly excellent.
In the conductive pattern forming ink of the present invention, it is preferable that the polysaccharide contains a polysaccharide having a carbonyl group reduced.
Thereby, the discharge stability of the droplet and the reliability of the formed conductor pattern can be made particularly excellent.

The conductor pattern of the present invention is formed by the conductor pattern forming ink of the present invention.
Thereby, a highly reliable conductor pattern can be provided.
The wiring board of the present invention is provided with the conductor pattern of the present invention.
Thereby, a highly reliable wiring board can be provided.

It is a longitudinal cross-sectional view which shows an example of suitable embodiment of the wiring board (ceramics circuit board) of this invention. It is explanatory drawing which shows the outline process of the manufacturing method of the wiring board (ceramics circuit board) shown in FIG. FIG. 2 is a manufacturing process explanatory diagram of the wiring board (ceramic circuit board) of FIG. 1. It is a perspective view which shows schematic structure of an inkjet apparatus. It is a schematic diagram for demonstrating schematic structure of an inkjet head.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is a longitudinal sectional view showing an example of a preferred embodiment of a wiring board (ceramic circuit board) of the present invention, and FIG. 2 shows a schematic process of the method for manufacturing the wiring board (ceramic circuit board) shown in FIG. FIG. 3 is a manufacturing process explanatory diagram of the wiring board (ceramic circuit board) of FIG. 1, FIG. 4 is a perspective view showing a schematic configuration of an ink jet apparatus (droplet discharge apparatus), and FIG. It is a schematic diagram for demonstrating schematic structure of the inkjet head (droplet discharge head) with which the droplet discharge apparatus of FIG.

<Conductor pattern forming ink>
The ink for forming a conductor pattern of the present invention is an ink used for forming a conductor pattern which is applied on a ceramic molded body composed of a material containing ceramic particles and a binder. It is an ink used to form a pattern.
In this embodiment, a case where a dispersion liquid in which silver particles are dispersed is used as a dispersion liquid in which metal particles are dispersed in an aqueous dispersion medium.

  By the way, a screen printing method is widely used as a method for forming a pattern on a ceramic molded body. On the other hand, in recent years, miniaturization of wiring (for example, wiring with a line width of 60 μm or less) and high density circuit boards by narrowing the pitch have been demanded. It is disadvantageous for pitching and it is difficult to meet the above requirements. Therefore, in recent years, a so-called ink jet method has been proposed as a method for forming a pattern on a ceramic molded body, in which a liquid material containing metal particles (ink for forming a conductor pattern) is ejected in droplets from a liquid ejection head. Has been. However, in the conventional conductor pattern forming ink, when the ceramic molded body is degreased and sintered, thermal breakage of the ceramic molded body may cause disconnection of a part of the formed conductor pattern. was there. In particular, the occurrence of such a problem has been remarkable with the recent increase in the density of circuit boards due to the miniaturization of wiring and the reduction in pitch.

In addition, a droplet discharge device (for industrial use) used for forming a conductor pattern is completely different from that applied to a printer (for consumer use). For example, a large number of droplets are long for mass production. It is required to discharge continuously over time. Also, the ink used for forming the conductor pattern (industrial) is generally poorer in liquid discharge during ejection than the ink used in printers (consumer use), and the ejection part (nozzle) of the inkjet head. Ink tends to remain on the discharge surface. As a result, when the ink is continuously discharged, the components contained in the ink adhere to the ink flow path of the droplet discharge device, and the supply of ink to the droplet discharge head tends to become unstable. Also, the ink used for forming the conductor pattern (industrial) has more compositional restrictions than those used in printers (consumer use) and has sufficient characteristics such as drying and re-dissolvability. In other words, solid content such as metal particles precipitates or aggregates, and the discharge portion of the droplet discharge head is likely to be clogged, resulting in a problem that droplets are frequently bent.
Therefore, as a result of intensive studies, the present inventor has found that the above problems can be solved by configuring the conductor pattern forming ink as described below.

  That is, the conductive pattern forming ink of the present invention includes metal particles, an aqueous dispersion medium in which the metal particles are dispersed, a water-soluble polysaccharide having a weight average molecular weight of 1,000 to 5,000, and polyglycerin. A polyglycerin compound having a skeleton, wherein the content of the polysaccharide in the conductor pattern forming ink is 1.0 wt% or more and 28 wt% or less, and the inclusion of the polyglycerin compound in the conductor pattern forming ink The rate is 1.0 wt% or more and 28 wt% or less, and the viscosity at 25 ° C. is 20 mPa · s or less. If even one of these requirements is missing, the above problem cannot be solved.

Hereinafter, each component of the conductor pattern forming ink will be described in detail.
[Aqueous dispersion medium]
First, the aqueous dispersion medium will be described.
In the present invention, the “aqueous dispersion medium” refers to one composed of water and / or a liquid having excellent compatibility with water (for example, water at 25 ° C .: a liquid having a solubility in 100 g of 30 g or more). As described above, the aqueous dispersion medium is composed of water and / or a liquid having excellent compatibility with water, but is preferably composed mainly of water. It is preferably 70 wt% or more, more preferably 90 wt% or more.

Specific examples of the aqueous dispersion medium include, for example, water, methanol, ethanol, butanol, propanol, isopropanol and other alcohol solvents, 1,4-dioxane, tetrahydrofuran (THF) and other ether solvents, pyridine, pyrazine, pyrrole and the like. Aromatic heterocyclic compound solvents, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, and aldehyde solvents such as acetaldehyde. Of these, one or a combination of two or more can be used.
The content of the aqueous dispersion medium in the conductor pattern forming ink is preferably 25 wt% or more and 60 wt% or less, and more preferably 30 wt% or more and 53 wt% or less. Thereby, while making the viscosity of an ink suitable, the change of the viscosity by volatilization of a dispersion medium can be made small.

[Silver particles]
Next, silver particles (metal particles) will be described.
Silver particles are the main component of the conductor pattern to be formed, and are components that impart conductivity to the conductor pattern.
The silver particles are dispersed in the ink.

  The average particle size of the silver particles is preferably 1 nm or more and 100 nm or less, and more preferably 10 nm or more and 40 nm or less. As a result, the ink ejection stability can be further improved, and a fine conductor pattern can be easily formed. In the present specification, the “average particle size” means a volume-based average particle size unless otherwise specified.

Further, the content of silver particles (silver particles (metal particles) in which the dispersant is not adsorbed on the surface) contained in the ink is preferably 0.5 wt% or more and 60 wt% or less, and is preferably 10 wt% or more and 45 wt%. The following is more preferable. Thereby, disconnection of a conductor pattern can be prevented more effectively, and a more reliable conductor pattern can be provided.
The silver particles (metal particles) are preferably dispersed in an aqueous dispersion medium as silver colloid particles (metal colloid particles) having a dispersant attached to the surface thereof. Thereby, the dispersibility of the silver particles in the aqueous dispersion medium is particularly excellent, and the ink ejection stability is particularly excellent.

  The content of the silver colloid particles in the ink is preferably 1 wt% or more and 60 wt% or less, and more preferably 10 wt% or more and 50 wt% or less. When the content of the silver colloidal particles is less than the lower limit, the silver content is small, and when a conductive pattern is formed, it is necessary to apply a plurality of times when a relatively thick film is formed. On the other hand, when the content of the silver colloidal particles exceeds the upper limit, the silver content increases and the dispersibility decreases. To prevent this, the frequency of stirring increases.

  Further, the heat loss to 500 ° C. in the thermogravimetric analysis of the silver colloid particles is preferably 1 wt% or more and 25 wt% or less. When the colloidal particles (solid content) are heated to 500 ° C., the dispersant or the like attached to the surface is oxidized and decomposed, and most of them are gasified and disappear. The weight loss due to heating up to 500 ° C. is considered to substantially correspond to the amount of the dispersant in the silver colloid particles. When the loss on heating is less than 1 wt%, the amount of the dispersant with respect to the silver particles is small, and the sufficient dispersibility of the silver particles is lowered. On the other hand, when it exceeds 25 wt%, the amount of the residual dispersant with respect to the silver particles increases, and the specific resistance of the conductor pattern increases. However, the specific resistance can be improved to some extent by heating and sintering after formation of the conductor pattern to decompose and disappear organic components. Therefore, when a ceramic molded body or the like that is sintered at a higher temperature is used as the substrate, such an effect can be easily obtained.

[Dispersant]
The conductor pattern forming ink preferably contains a dispersant.
The dispersing agent forms silver colloidal particles by adhering to the silver particles. Since such silver colloidal particles are excellent in dispersion stability, the discharge stability of the ink droplets for forming the conductor pattern is more excellent.

Although it does not specifically limit as a dispersing agent, it has 3 or more of COOH groups and OH groups, and the number of COOH groups is the same as that of OH groups, or contains hydroxy acid or its salt more than it. Is preferred. These dispersants adsorb on the surface of silver particles to form colloidal particles, and the colloidal liquid is stabilized by uniformly dispersing silver colloidal particles in an aqueous solution by the electric repulsive force of COOH groups present in the dispersant. Has the function of As described above, since the silver colloid particles are stably present in the ink, a fine conductor pattern can be more easily formed. Further, silver particles are uniformly distributed in a pattern (conductor pattern precursor) formed with ink, and cracks, disconnections, and the like are less likely to occur. On the other hand, if the number of COOH groups and OH groups in the dispersant is less than 3 or the number of COOH groups is less than the number of OH groups, the dispersibility of the silver colloid particles cannot be sufficiently obtained. There is a case.
Examples of such a dispersing agent include citric acid, malic acid, trisodium citrate, tripotassium citrate, trilithium citrate, triammonium citrate, disodium malate, tannic acid, gallotannic acid, and pentaploid tannin. Of these, one or a combination of two or more can be used.

  Further, the dispersant may contain mercapto acid or a salt thereof having two or more COOH groups and SH groups. In these dispersants, mercapto groups are adsorbed on the surface of silver particles to form colloidal particles, and colloidal particles are uniformly dispersed in an aqueous solution by the electric repulsive force of COOH groups present in the dispersant. Has the function of stabilizing As described above, since the silver colloid particles are stably present in the ink, a fine conductor pattern can be more easily formed. Further, silver particles are uniformly distributed in a pattern (conductor pattern precursor) formed with ink, and cracks, disconnections, and the like are less likely to occur. On the other hand, when the number of COOH groups and SH groups in the dispersant is less than 2, that is, only one, the dispersibility of the silver colloidal particles may not be sufficiently obtained.

  Examples of such dispersants include mercaptoacetic acid, mercaptopropionic acid, thiodipropionic acid, mercaptosuccinic acid, thioacetic acid, sodium mercaptoacetate, sodium mercaptopropionate, sodium thiodipropionate, disodium mercaptosuccinate, Examples include potassium mercaptoacetate, potassium mercaptopropionate, potassium thiodipropionate, dipotassium mercaptosuccinate, and the like, and one or more of these can be used in combination.

[Polysaccharides]
The conductive pattern forming ink according to the present invention contains a water-soluble polysaccharide having a weight average molecular weight of 1,000 or more and 5,000 or less. By including such a polysaccharide together with a polyglycerin compound, which will be described in detail later, in the conductive pattern formed using the conductive pattern forming ink, it is ensured that unintentional cracks, disconnections, etc. occur. Therefore, the reliability of the formed conductor pattern can be increased.

The conductive pattern forming ink preferably contains a polysaccharide that is solid at room temperature (25 ° C.). Thereby, the reliability of the conductor pattern formed can be made especially excellent.
The weight average molecular weight of the polysaccharide is from 1,000 to 5,000, preferably from 1,200 to 4,500, more preferably from 1,500 to 4,000. . Thereby, the effects as described above are more remarkably exhibited.
Examples of the polysaccharide include cellulose, guar gum, starch (amylose, amylopectin), pullulan, dextrin, fructan, glucomannan, agarose, agaropectin, carrageenan, chitin, chitosan, pectin, alginic acid, hyaluronic acid, maltodextrin, or these Derivatives (for example, polysaccharides in which a carbonyl group is reduced) and the like can be mentioned, and one or more of these can be used in combination.

Among the above, the conductive pattern forming ink preferably contains a solid maltodextrin at room temperature (25 ° C.). Thereby, the discharge stability of the droplet and the reliability of the formed conductor pattern can be made particularly excellent.
In addition, the conductor pattern forming ink preferably contains a polysaccharide having a carbonyl group reduced as the polysaccharide. Thereby, the discharge stability of the droplet and the reliability of the formed conductor pattern can be made particularly excellent.

  The polysaccharide content X (B) in the conductive pattern forming ink is 1.0% by weight or more and 28% by weight or less. This makes it possible to more effectively prevent the occurrence of cracks and disconnections while making the ejection stability of the conductor pattern forming ink particularly excellent. On the other hand, if the content of the polysaccharide is less than the lower limit, it is difficult to reliably prevent the occurrence of cracks. On the other hand, if the content of the polysaccharide exceeds the upper limit, it becomes difficult to make the viscosity of the conductor pattern forming ink sufficiently low, and the droplet ejection stability is made sufficiently excellent. It becomes difficult.

  As described above, the polysaccharide content X (B) in the conductor pattern forming ink is 1.0 wt% or more and 28 wt% or less, but 1.1 wt% or more and 14 wt% or less. Is preferable, and it is more preferable that it is 2.2 weight% or more and 10.5 weight% or less. Thereby, the effects as described above are more remarkably exhibited. When the conductor pattern forming ink contains two or more components as polysaccharides, the sum of the content ratios of these components is preferably within the above range.

[Polyglycerin compound]
The ink for forming a conductor pattern according to the present invention contains a polyglycerol compound having a polyglycerol skeleton. By including such a polyglycerin compound together with the polysaccharide as described above, it is possible to reliably prevent unintentional cracks, disconnections, etc. from occurring in the conductive pattern formed using the conductive pattern forming ink. And the reliability of the formed conductor pattern can be increased.

  The polyglycerin compound may be any one as long as it has a polyglycerin skeleton (a structure in which a plurality of glycerin molecules are condensed). Examples of the polyglycerin compound include polyglycerin and polyglycerin. Examples include monostearate, tristearate, tetrastearate, monooleate, pentaoleate, monolaurate, monocaprylate, polycinnolate, sesquistearate, decaoleate, and sesquioleate. One kind or a combination of two or more kinds can be used. Among these, as the polyglycerol compound, polyglycerol is preferable. Polyglycerin is particularly excellent in the ability to follow expansion and contraction due to temperature changes of the ceramic molded body to which the conductive pattern forming ink is applied, and more reliably removed from the conductive pattern after the ceramic molded body is sintered. Is a component that can. As a result, the electrical characteristics of the conductor pattern can be made higher. Furthermore, since polyglycerin has high solubility in an aqueous dispersion medium, it can be suitably used.

  The weight average molecular weight of the polyglycerin compound is preferably 300 or more and 3000 or less, more preferably 400 or more and 1000 or less, and further preferably 400 or more and 600 or less. Thereby, when the pattern formed using the conductor pattern forming ink is dried, the generation of cracks can be more reliably prevented. On the other hand, when the weight average molecular weight of the polyglycerin compound is less than the lower limit, depending on the composition of the polyglycerin compound, the polyglycerin compound tends to be decomposed when removing the aqueous dispersion medium, and cracks are generated. The effect of preventing is reduced. When the weight average molecular weight of the polyglycerin compound exceeds the above upper limit, depending on the composition of the polyglycerin compound, the solubility and dispersibility in the conductor pattern forming ink may decrease due to the excluded volume effect or the like.

  The content X (A) of the polyglycerol compound in the conductive pattern forming ink is 1.0% by weight or more and 28% by weight or less. This makes it possible to more effectively prevent the occurrence of cracks and disconnections while making the ejection stability of the conductor pattern forming ink particularly excellent. On the other hand, when the content of the polyglycerin compound is less than the lower limit, it is difficult to reliably prevent the occurrence of cracks. On the other hand, if the content of the polyglycerin compound exceeds the upper limit, it becomes difficult to make the viscosity of the conductive pattern forming ink sufficiently low, and the droplet ejection stability is made sufficiently excellent. It becomes difficult.

  As described above, the content X (A) of the polyglycerin compound in the conductor pattern forming ink is 1.0 wt% or more and 28 wt% or less, but 1.1 wt% or more and 14 wt% or less. And is more preferably 2.0 wt% or more and 9.3 wt% or less. Thereby, the effects as described above are more remarkably exhibited. When the conductor pattern forming ink contains two or more components as the polyglycerin compound, the sum of the content ratios of these components is preferably a value within the above range.

  When the content of the polyglycerin compound in the conductor pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductor pattern forming ink is X (B) [wt%], X (B A) + X (B) ≦ 28 is preferably satisfied, X (A) + X (B) ≦ 20 is more preferable, and X (A) + X (B) ≦ 15 is satisfied. It is more preferable to satisfy. As a result, the reliability of the formed conductor pattern can be made sufficiently high while the droplet discharge stability is particularly excellent. Moreover, the deformation of the wiring in the pressing process can be suppressed due to the presence of excess organic matter.

  When the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductive pattern forming ink is X (B) [wt%], 7. It is preferable to satisfy the relationship 5 ≦ X (A) + 4X (B), and it is more preferable to satisfy the relationship 12 ≦ X (A) + 4X (B). As a result, the dimensional accuracy and reliability of the formed conductor pattern can be made particularly excellent while the droplet ejection stability is sufficiently excellent.

  When the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductive pattern forming ink is X (B) [wt%], 0. It is preferable to satisfy the relationship of 12 ≦ X (A) / X (B) ≦ 12, and it is more preferable to satisfy the relationship of 0 · 20 ≦ X (A) / X (B) ≦ 6. Thereby, the discharge stability of the droplet can be made particularly excellent, and the occurrence of disconnection in the inner layer and the surface layer can be more effectively suppressed.

[Other ingredients]
The constituent components of the conductor pattern forming ink are not limited to the above components, and may include components other than those described above.
For example, the conductive pattern forming ink includes polyethylene glycol # 200 (weight average molecular weight 200), polyethylene glycol # 300 (weight average molecular weight 300), polyethylene glycol # 400 (average molecular weight 400), polyethylene glycol # 600 (weight average molecular weight 600). ), Polyethylene glycols such as polyethylene glycol # 1000 (weight average molecular weight 1000), polyethylene glycol # 1500 (weight average molecular weight 1500), polyethylene glycol # 1540 (weight average molecular weight 1540), polyethylene glycol # 2000 (weight average molecular weight 2000), Polyvinyl alcohol # 200 (weight average molecular weight: 200), polyvinyl alcohol # 300 (weight average molecular weight: 300), polyvinyl alcohol # 400 (flat Molecular weight: 400), polyvinyl alcohol # 600 (weight average molecular weight: 600), polyvinyl alcohol # 1000 (weight average molecular weight: 1000), polyvinyl alcohol # 1500 (weight average molecular weight: 1500), polyvinyl alcohol # 1540 (weight average molecular weight: 1540) and an organic binder such as polyvinyl alcohol such as polyvinyl alcohol # 2000 (weight average molecular weight: 2000).
Further, it may contain a surface tension adjusting agent such as acetylene glycol compound, polyhydric alcohol such as ethylene glycol, 1,3-propanediol, 1,3-butylene glycol, propylene glycol, urea, thiourea, etc. Good.

The viscosity at 25 ° C. of the conductive pattern forming ink is 20 mPa · s or less. Thereby, the discharge stability of the droplets can be made sufficiently excellent.
As described above, the viscosity at 25 ° C. of the conductive pattern forming ink is 20 mPa · s or less, preferably 1.5 mPa · s or more and 8.0 mPa · s or less, and preferably 2.0 mPa · s or more and 6. More preferably, it is 0 mPa · s or less. As a result, the discharge stability of the droplets can be made particularly excellent, the wetting and spreading of the ink that has landed on the ceramic molded body can be prevented, and a conductor pattern precursor having a fine line width is formed. be able to.

The contact angle between the conductor pattern forming ink and the ceramic molded body is not particularly limited, but is preferably 40 ° or more and 80 ° or less, and more preferably 50 ° or more and 80 ° or less. If the contact angle is too small, it may be difficult to form a conductor pattern with a fine line width. On the other hand, if the contact angle is too large, it may be difficult to form a conductor pattern with a uniform line width depending on the discharge conditions and the like. In addition, the contact area between the landed droplet and the ceramic molded body may be too small, and the landed droplet may be displaced from the landing position.
The surface tension of the conductor pattern forming ink is preferably 30 mN / m or more and 50 mN / m or less.

<< Method for producing conductive pattern forming ink >>
Next, an example of a method for producing the above-described conductor pattern forming ink will be described.
In this embodiment, the conductor pattern forming ink will be described as a colloidal liquid in which silver colloidal particles are dispersed in an aqueous dispersion medium.
When manufacturing the ink of this embodiment, first, an aqueous solution in which the dispersant and the reducing agent are dissolved is prepared.

As a blending amount of the dispersing agent, it is preferable to blend so that a molar ratio of silver and the dispersing agent in a silver salt such as silver nitrate as a starting material is about 1: 1 to 1: 100. When the molar ratio of the dispersant to the silver salt is increased, the particle size of the silver particles is reduced and the contact points between the particles after the formation of the conductor pattern is increased, so that a film having a low volume resistance value can be obtained.
The reducing agent has a function of generating silver particles by reducing Ag ⁺ ions in a silver salt such as silver nitrate (Ag ⁺ NO ³⁻ ) which is a starting material.

The reducing agent is not particularly limited, and examples thereof include amines such as hydrazine, dimethylaminoethanol, methyldiethanolamine, and triethanolamine; hydrogen compounds such as sodium borohydride, hydrogen gas, and hydrogen iodide; carbon monoxide, Oxides such as hyposulfite hypophosphorous acid, low valent metal salts such as Fe (II) compounds and Sn (II) compounds, saccharides such as D-glucose, organic compounds such as formaldehyde, or the above dispersions Citric acid and malic acid which are the hydroxy acids mentioned as agents, and trisodium citrate, tripotassium citrate, trilithium citrate, triammonium citrate, disodium malate and tannic acid which are hydroxy acid salts It is done. Among them, tannic acid and hydroxy acid can be suitably used because they function as a reducing agent and at the same time exert an effect as a dispersant. Alternatively, mercaptoacetic acid, mercaptopropionic acid, thiodipropionic acid, mercaptosuccinic acid, mercaptosuccinic acid, sodium mercaptoacetate, which is thioacetic acid or mercaptoate, listed above as a dispersant that forms a stable bond on the metal surface, Sodium mercaptopropionate, sodium thiodipropionate, sodium mercaptosuccinate, potassium mercaptoacetate, potassium mercaptopropionate, potassium thiodipropionate, potassium mercaptosuccinate and the like can be suitably used. These dispersants and reducing agents may be used alone or in combination of two or more. When these compounds are used, the reduction reaction may be promoted by applying light or heat.
In addition, the amount of the reducing agent is required to be an amount that can completely reduce the silver salt that is the starting material. However, the excessive reducing agent remains as impurities in the silver colloidal solution, and the film is formed after film formation. The necessary minimum amount is preferable because it causes deterioration of conductivity. Specifically, the molar ratio of the silver salt to the reducing agent is about 1: 1 to 1: 3.

In this embodiment, it is preferable to adjust the pH of the aqueous solution to 6 to 12 after dissolving the dispersant and the reducing agent to prepare the aqueous solution.
This is due to the following reasons. For example, when trisodium citrate, which is a dispersant, and ferrous sulfate, which is a reducing agent, are mixed, the pH is about 4 to 5 and lower than the above pH 6, although it depends on the overall concentration. The hydrogen ions present at this time move the equilibrium of the reaction represented by the following reaction formula (1) to the right side, and the amount of COOH increases. Therefore, thereafter, the electric repulsive force on the surface of the silver particles obtained by dropping the silver salt solution decreases, and the dispersibility of the silver particles (colloid particles) decreases.
−COO ⁻ + H ⁺ → −COOH (1)

Therefore, after dissolving the dispersant and the reducing agent to prepare an aqueous solution, an alkaline compound is added to the aqueous solution to reduce the hydrogen ion concentration.
It does not specifically limit as an alkaline compound to add, For example, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia water, the alkanolamine mentioned above, etc. can be used. Among these, when alkanolamine is used, the pH can be easily adjusted and the dispersion stability of the formed silver colloidal particles can be further improved.
In addition, when there is too much addition amount of an alkaline compound and pH exceeds 12, precipitation of the hydroxide of the ion of the remaining reducing agent like iron ion will occur easily.

Next, in the ink manufacturing process of this embodiment, an aqueous solution containing a silver salt is dropped into an aqueous solution in which the prepared dispersant and reducing agent are dissolved.
The silver salt is not particularly limited, and for example, silver acetate, silver carbonate, silver oxide, silver sulfate, silver nitrite, silver chlorate, silver sulfide, silver chromate, silver nitrate, silver dichromate and the like can be used. . Among these, silver nitrate having a high solubility in water is preferable.

The amount of the silver salt is determined in consideration of the content of the desired colloidal particles and the ratio reduced by the reducing agent. For example, in the case of silver nitrate, 15 to 70 parts per 100 parts by weight of the aqueous solution. The amount is preferably about parts by weight.
The silver salt aqueous solution is prepared by dissolving the silver salt in pure water, and the prepared silver salt aqueous solution is gradually dropped into the aqueous solution in which the dispersing agent and reducing agent described above are dissolved.

In this step, the silver salt is reduced to silver particles by a reducing agent, and the dispersant is adsorbed on the surface of the silver particles to form silver colloidal particles. As a result, an aqueous solution in which silver colloidal particles are colloidally dispersed in the aqueous solution is obtained.
In the obtained solution, in addition to the colloidal particles, a reducing agent residue and a dispersing agent are present, and the ion concentration of the whole liquid is high. The liquid in such a state is likely to coagulate and precipitate easily. Therefore, it is desirable to perform cleaning in order to remove excess ions in such an aqueous solution and lower the ion concentration.

As a washing method, for example, the aqueous solution containing the obtained colloidal particles is allowed to stand for a certain period, and the resulting supernatant liquid is removed, and then pure water is added and stirred again, and further left to stand for a certain period. In addition, a method of repeating the step of removing the supernatant liquid several times, a method of performing centrifugation instead of the above-mentioned standing, a method of removing ions by ultrafiltration, and the like can be mentioned.
Alternatively, cleaning may be performed by the following method. After the solution is prepared, the pH of the solution is adjusted to an acidic region of 5 or less, and the electric repulsive force on the surface of the silver particles is reduced by moving the equilibrium of the reaction of the above reaction formula (1) to the right side. It is possible to remove salts and solvents by washing in a state where metal colloidal particles are aggregated. In the case of a metal colloid particle having a low molecular weight sulfur compound such as mercapto acid on the particle surface as a dispersant, a stable bond is formed on the metal surface. Therefore, the aggregated metal colloid particle has an alkaline pH of 6 or more. By re-adjusting to this region, it is possible to obtain a metal colloid liquid that is easily redispersed and excellent in dispersion stability.

In the ink production process of the present embodiment, it is preferable to adjust the final pH to 6 to 11 by adding an aqueous alkali metal hydroxide solution to an aqueous solution in which silver colloidal particles are dispersed as necessary after the above step.
This is because the concentration of sodium, which is an electrolyte ion, may be decreased because washing is performed after reduction. In the solution in such a state, the equilibrium of the reaction represented by the following reaction formula (2) moves to the right side. To do. If this is the case, the electrical repulsive force of the silver colloid is reduced and the dispersibility of the silver particles is lowered. Therefore, by adding an appropriate amount of alkali hydroxide, the equilibrium of the reaction formula (2) is shifted to the left side, and silver It stabilizes the colloid.
—COO ^— Na ⁺ + H ₂ O → —COOH + Na ⁺ + OH ⁻ (2)

As said alkali metal hydroxide used at this time, the compound similar to the compound used when adjusting pH first can be mentioned, for example.
If the pH is less than 6, the equilibrium of the reaction formula (2) shifts to the right side, so that the colloidal particles become unstable. On the other hand, if the pH exceeds 11, hydroxides of remaining ions such as iron ions This is not preferable because precipitation of selenium tends to occur. However, if iron ions or the like are removed in advance, there is no major problem even if the pH exceeds 11.

Cations such as sodium ions are preferably added in the form of hydroxides. This is because the self-protolysis of water can be used, so that cations such as sodium ions can be added to the aqueous solution most effectively.
Moreover, in the said process of adjusting pH to 6-11, you may use an alkanolamine instead of an alkali metal hydroxide aqueous solution.

By adding other components such as polysaccharides and polyglycerin compounds as described above to the aqueous solution in which silver colloidal particles obtained as described above are dispersed, an ink for forming a conductor pattern (the conductor pattern formation of the present invention) Ink).
In addition, the addition time of other components, such as a polysaccharide and a polyglycerin compound, is not specifically limited, As long as it is after formation of a silver colloid particle, it may be sufficient.

<< Conductor pattern and wiring board >>
Next, the conductor pattern and wiring board of the present invention will be described.
As shown in FIG. 1, a wiring board (ceramic circuit board) 30 includes a laminated board 32 in which a large number (for example, about 10 to 20) of ceramic boards 31 are laminated, and an outermost layer of the laminated board 32, that is, one of them. And a conductor pattern (circuit) 21 made of fine wiring or the like formed on the surface of the substrate.

The laminated substrate 32 includes a conductor pattern (circuit, conductor pattern of the present invention) 20 between the laminated ceramic substrates 31 and 31.
The conductor pattern 20 is a thin film formed by heating (sintering) a pattern (conductor pattern precursor, hereinafter also simply referred to as a precursor) 10 formed by the conductor pattern forming ink of the present invention. It is a conductor pattern, Comprising: Silver particle | grains are mutually couple | bonded and the said silver particle is couple | bonded without gap at least on the conductor pattern surface.

Such a conductor pattern 20 is formed using the conductor pattern forming ink of the present invention. For this reason, the precursor 10 is formed with high accuracy and the occurrence of cracks is prevented. In addition, the conductor pattern 20 has high reliability in which disconnection is prevented.
The conductor pattern 20 as described above is used for high-frequency modules, interposers, MEMS (Micro Electro Mechanical Systems), acceleration sensors, surface acoustic wave elements, antennas, comb electrodes, and the like of mobile telephones such as mobile phones and PDAs. The present invention can be applied to deformed electrodes and other electronic parts such as various measuring devices.

The conductor pattern 20 can be obtained by heating the conductor pattern precursor 10 as a sintering process at 160 ° C. or more for 20 minutes or more. The conductor pattern precursor 10 can be sintered together with degreasing and sintering of the ceramic molded body 15 as described later.
The conductor pattern 20 </ b> A is also formed by the conductor pattern forming ink of the present invention, similarly to the conductor pattern 20.

The ceramic substrate 31 has a sheet shape and supports the conductor pattern 20.
In addition, a contact (via) 33 connected to the conductor pattern 20 is formed on the ceramic substrate 31. With such a configuration, the conductor pattern 20 is electrically connected by the contact 33 between the conductor patterns 20 and 20 disposed above and below.
As will be described later, the ceramic substrate 31 is obtained by forming a material containing ceramic powder such as silicon dioxide, aluminum oxide, and titanium oxide and a binder into a sheet shape, and then heat-treating (sintering treatment). It is a substrate.

Since the wiring board 30 as described above is formed using the conductor pattern forming ink of the present invention, the conductor pattern 20 is prevented from being disconnected and has high reliability.
The wiring board 30 as described above is an electronic component used in various electronic devices, such as circuit patterns composed of various wirings, electrodes, etc., multilayer ceramic capacitors, multilayer inductors, LC filters, composite high-frequency components, and the like. Is formed on a substrate.

<Method for manufacturing wiring board>
Next, a method of manufacturing the wiring board as described above will be described with reference to the schematic process diagram of FIG.
Hereinafter, each step will be described in detail.
[Ceramic compact formation process (substrate preparation process)]
First, as a raw material powder, ceramic powder (ceramic material) made of alumina (Al ₂ O ₃ ) or titanium oxide (TiO ₂ ) having an average particle diameter of 1 μm to 2 μm, and an average particle diameter of 1 μm to 2 μm A glass powder made of borosilicate glass or the like is prepared, and these are mixed at an appropriate mixing ratio, for example, a weight ratio of 1: 1.

Next, a suitable binder (binder), a plasticizer, an organic solvent (dispersant), etc. are added to the obtained mixed powder, and a slurry is obtained by mixing and stirring. Here, polyvinyl butyral is preferably used as the binder, but it is insoluble in water and easily dissolved or swelled in a so-called oil-based organic solvent.
Next, the resulting slurry is formed into a sheet on a PET film using a doctor blade, reverse coater, etc., and formed into a sheet having a thickness of several μm or more and several hundreds μm or less depending on the manufacturing conditions of the product. Then, it is wound on a roll.

Subsequently, the sheet is cut according to the use of the product, and further cut into a sheet having a predetermined size. In this embodiment, for example, it is cut into a square shape having a side length of 200 mm.
Next, a through hole (through hole) is formed at a predetermined position by drilling with a CO ₂ laser, a YAG laser, a mechanical punch or the like as necessary.
Then, by filling the through-hole with a thick film conductive paste in which metal particles are dispersed, a portion (contact precursor 16) to be the contact 33 is formed. As the thick film conductive paste, a conductor pattern forming ink as described later can be used.
Thus, a plurality of substrates (ceramic compact 15) are prepared.

[Conductor pattern precursor forming step]
On the surface of one side of the ceramic molded body 15 obtained as described above, the conductor pattern precursor 10 to be the conductor pattern 20 is formed in a state continuous with the contact precursor 16. That is, as shown in FIG. 3A, the above-described conductor pattern forming ink (hereinafter also simply referred to as ink) 1 is applied onto the ceramic molded body 15 by a droplet discharge (inkjet) method. The precursor 10 is formed.

In the present embodiment, the conductive pattern forming ink can be discharged by using, for example, an ink jet apparatus (droplet discharge apparatus) 100 shown in FIGS. Hereinafter, the inkjet apparatus 100 will be described.
FIG. 4 is a perspective view of the ink jet apparatus 100. In FIG. 4, the X direction is the left-right direction of the base 130, the Y direction is the front-rear direction, and the Z direction is the up-down direction.

The ink jet apparatus 100 includes an ink jet head (droplet discharge head; hereinafter simply referred to as a head) 110, a base 130, a table 140, a control device 190, a table positioning unit 170, and a head positioning unit 180 shown in FIG. And have.
The base 130 is a table that supports each component of the inkjet apparatus 100 such as the table 140, the table positioning unit 170, and the head positioning unit 180.

The table 140 is installed on the base 130 via the table positioning means 170. The table 140 is used for placing the substrate S (the ceramic molded body 15 in this embodiment).
A rubber heater (not shown) is disposed on the back surface of the table 140. The ceramic molded body 15 placed on the table 140 is heated to a predetermined temperature by a rubber heater over the entire upper surface thereof.

  At least part of the aqueous dispersion medium evaporates from the surface side of the ink 1 that has landed on the ceramic molded body 15. At this time, since the ceramic molded body 15 is heated, evaporation of the aqueous dispersion medium is promoted. The ink 1 that has landed on the ceramic molded body 15 is thickened from the outer edge of the surface as it dries. That is, the solid content (particles) concentration at the outer peripheral portion is faster than the central portion and reaches the saturated concentration. Thicken from the outer edge. The thickened ink 1 on the outer edge stops its own wetting and spreading along the surface direction of the ceramic molded body 15, so that the line width can be easily controlled with respect to the landing diameter.

The heating temperature of the ceramic molded body 15 is preferably 40 ° C. or higher and 100 ° C. or lower, and more preferably 50 ° C. or higher and 70 ° C. or lower. By setting it as such conditions, when an aqueous dispersion medium evaporates, it can prevent more effectively that a crack generate | occur | produces.
The table positioning unit 170 includes a first moving unit 171 and a motor 172. The table positioning means 170 determines the position of the table 140 on the base 130, and thereby determines the position of the ceramic molded body 15 on the base 130.

The first moving means 171 has two rails provided substantially parallel to the Y direction and a support base that moves on the rails. The support base of the first moving means 171 supports the table 140 via the motor 172. Then, as the support base moves on the rail, the table 140 on which the base material S is placed is moved and positioned in the Y direction.
The motor 172 supports the table 140 and swings and positions the table 140 in the θz direction.

The head positioning unit 180 includes a second moving unit 181, a linear motor 182, and motors 183, 184 and 185. The head positioning unit 180 determines the position of the head 110.
The second moving means 181 is provided with two support pillars standing from the base 130, a support base provided between the support pillars, the rail support having two rails, and the rails. And a support member (not shown) for supporting the head 110. Then, as the support member moves along the rail, the head 110 is moved and positioned in the X direction.

The linear motor 182 is provided in the vicinity of the support member, and can move and position the head 110 in the Z direction.
Motors 183, 184, and 185 swing and position the head 110 in the α, β, and γ directions, respectively.
By the table positioning unit 170 and the head positioning unit 180 as described above, the ink jet apparatus 100 accurately controls the relative position and posture of the ink ejection surface 115P of the head 110 and the base material S on the table 140. It can be done.

  As shown in FIG. 5, the head 110 ejects the ink 1 from the nozzles (protruding portions) 118 by an inkjet method (droplet ejection method). In the present embodiment, the head 110 uses a piezo method in which ink is ejected using a piezo element 113 as a piezoelectric element. The piezo method has the advantage that the composition of the material is not affected because heat is not applied to the ink 1.

The head 110 has a head body 111, a diaphragm 112, and a piezo element 113.
The head main body 111 has a main body 114 and a nozzle plate 115 on the lower end surface thereof. Then, the main body 114 is sandwiched between the plate-like nozzle plate 115 and the vibration plate 112, whereby a reservoir 116 as a space and a plurality of ink chambers 117 branched from the reservoir 116 are formed.

Ink 1 is supplied to the reservoir 116 from an ink tank (not shown). The reservoir 116 forms a flow path for supplying the ink 1 to each ink chamber 117.
The nozzle plate 115 is attached to the lower end surface of the main body 114 and constitutes an ink ejection surface 115P. In the nozzle plate 115, a plurality of nozzles 118 that discharge ink 1 are opened corresponding to the ink chambers 117. An ink flow path is formed from each ink chamber 117 toward the corresponding nozzle 118.

The diaphragm 112 is attached to the upper end surface of the head body 111 and constitutes the wall surface of each ink chamber 117. The diaphragm 112 can vibrate according to the vibration of the piezo element 113.
The piezo element 113 is provided corresponding to each ink chamber 117 on the opposite side of the vibration plate 112 from the head body 111. The piezoelectric element 113 is obtained by sandwiching a piezoelectric material such as quartz with a pair of electrodes (not shown). The pair of electrodes is connected to the drive circuit 191.

When an electric signal is input from the drive circuit 191 to the piezo element 113, the piezo element 113 is expanded or contracted. When the piezo element 113 contracts and deforms, the pressure in the ink chamber 117 decreases, and the ink 1 flows from the reservoir 116 into the ink chamber 117. Further, when the piezo element 113 expands and deforms, the pressure in the ink chamber 117 increases and the ink 1 is ejected from the nozzle 118. Note that the amount of deformation of the piezo element 113 can be controlled by changing the applied voltage. Further, the deformation speed of the piezo element 113 can be controlled by changing the frequency of the applied voltage. That is, by controlling the voltage applied to the piezo element 113, the ejection conditions of the ink 1 can be controlled.
The control device 190 controls each part of the inkjet device 100. For example, by adjusting the waveform of the applied voltage generated by the drive circuit 191 to control the ink 1 ejection conditions, or by controlling the table positioning unit 170 and the head positioning unit 180, the ejection position of the ink 1 onto the substrate S is controlled. Control.

  By using the ink jet apparatus 100 as described above, the ink 1 can be discharged and arranged with a desired amount and accuracy in a desired place on the ceramic molded body 15 (base material S). Furthermore, since the ink 1 is a conductor pattern forming ink, the conductor pattern precursor 10 can be accurately and easily formed over a long period of time as shown in FIG. Further, even when the application of the ink 1 is temporarily stopped and left for a long period of time, the clogging of the nozzles 118 of the head 110 is prevented. Excellent droplet discharge stability can be obtained.

In addition, you may perform a drying process about the formed conductor pattern precursor 10. FIG. The drying process can be performed under the same conditions as the heating temperature of the ceramic molded body 15 at the time of droplet discharge.
In addition, when forming a general conductor pattern precursor, there was a problem that silver particles aggregated together with volatilization of the aqueous dispersion medium, resulting in bulges and cracks, but the conductor pattern precursor 10 was described above. Such a problem is prevented by including such a polysaccharide and a polyglycerol compound.

  Further, after applying ink 1 by the droplet discharge method, the ceramic molded body 15 is heated to evaporate the dispersion medium such as water, and the ink 1 is applied again on the conductor pattern precursor 10 after the heating. The thick film conductor pattern precursor 10 may be formed by repeatedly performing the above-described processes. In such a case, since the viscosity of the ink 1 once applied to the ceramic molded body 15 increases, the ink 1 is prevented from excessively spreading on the ceramic molded body 15, and the thickness of the conductor pattern precursor 10 is reduced. In addition, the line width and the like can be made more accurate.

Further, in this case, when the drying inhibitor is included in the ink 1 after the dispersion medium is evaporated, there is no possibility that the pattern is lost even when the formed conductor pattern precursor 10 is not completely dried. Therefore, once ink 1 is applied and dried, it is allowed to stand for a long time, and then ink 1 can be applied again.
In this case, since the polysaccharides and polyglycerin compounds as described above are chemically and physically stable compounds, the ink changes in quality even if the ink is applied and dried and left for a long time. There is no fear, ink can be applied again, and a uniform pattern can be formed. Thereby, there is no possibility that the conductor pattern precursor 10 itself has a multilayer structure, and as a result, there is no possibility that the specific resistance between the layers increases and the specific resistance of the entire conductor pattern 20 increases.
After the conductor pattern precursor 10 is formed in this way, the required number of ceramic molded bodies 15 on which the conductor pattern precursor 10 is formed, for example, about 10 to 20 are produced by the same process.

[Lamination process]
Next, the PET film is peeled off from these ceramic molded bodies 15, and these are laminated as shown in FIG.
At this time, the ceramic molded bodies 15 to be laminated are arranged so that the conductor pattern precursors 10 are connected via the contact precursors 16 as necessary between the ceramic molded bodies 15 stacked one above the other.

  Thereafter, the ceramic compacts 15 are pressure-bonded to each other while being heated to a glass transition point or higher of the binder constituting the ceramic compact 15. Thereby, the laminated body 17 is obtained. In addition, in general conductor pattern forming ink, a large amount of drying inhibitor may be added in order to improve droplet discharge stability. In such a case, the additive may be used as crystals in this process. There was a problem that it was easy to precipitate. However, in the present invention, the inclusion of the polysaccharide and the polyglycerin compound as described above in the conductive pattern forming ink 1 makes it possible to make the content of the drying inhibitor relatively low. Can be prevented.

[Heating process]
When the laminated body 17 is formed in this way, for example, heat treatment is performed by a belt furnace or the like. As a result, each ceramic molded body 15 is sintered to become a ceramic substrate 31 as shown in FIG. 1, and the conductor pattern precursor 10 is obtained by sintering the silver colloid particles constituting the conductor pattern precursor 10 to form a wiring pattern. Or a conductor pattern (circuit) 20 composed of an electrode pattern. And the laminated body 17 becomes the laminated substrate 32 shown in FIG. 1 by heat-processing the laminated body 17 in this way.

  Here, the heating temperature of the laminated body 17 is preferably not less than the softening point of the glass material contained in the ceramic molded body 15, and specifically not less than 600 ° C. and not more than 900 ° C. As heating conditions, the temperature is raised and lowered at an appropriate rate, and the maximum heating temperature, that is, the temperature of 600 ° C. to 900 ° C. is maintained for an appropriate time according to the temperature. To do.

  Thus, the glass component of the ceramic substrate 31 obtained can be softened by raising the heating temperature to a temperature equal to or higher than the softening point of the glass, that is, the temperature range. Therefore, after cooling to room temperature and curing the glass component, the ceramic substrate 31 and the conductor pattern 20 constituting the laminated substrate 32 are more firmly fixed.

Further, by heating in such a temperature range, the obtained ceramic substrate 31 becomes a low-temperature sintered ceramic (LTCC) formed by sintering at a temperature of 900 ° C. or lower.
Here, the metals in the ink 1 arranged on the ceramic molded body 15 are fused to each other by the heat treatment and become conductive by being continuous.

By such heat treatment, the conductor pattern 20 is formed by being directly connected to the contact 33 in the ceramic substrate 31 and conducting. Here, if the conductor pattern 20 is merely placed on the ceramic substrate 31, the mechanical connection strength to the ceramic substrate 31 is not ensured, and therefore there is a possibility that the conductor pattern 20 may be damaged by an impact or the like. However, in the present embodiment, as described above, the conductor pattern 20 is firmly fixed to the ceramic substrate 31 by once softening the glass in the ceramic molded body 15 and then curing it. Therefore, the formed conductor pattern 20 has a high mechanical strength.
By such heat treatment, the conductor pattern 20A can be formed at the same time as the conductor pattern 20, whereby a ceramic circuit board (wiring board) 30 can be obtained.

  In the manufacturing method of the ceramic circuit board 30 as described above, since the ink 1 is used in forming the conductor pattern, the ejection stability of the droplet of the ink 1 is excellent, and the conductor pattern precursor 10 is accurately used. Can be formed. Further, the obtained conductor pattern 20 has high reliability in which generation of cracks and disconnection are prevented. The manufactured ceramic circuit board 30 is also highly reliable.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, in the above-described embodiment, the case where the colloid liquid is used as the dispersion liquid in which the metal particles are dispersed in the solvent has been described, but the colloid liquid may not be used.
In the above-described embodiment, the conductor pattern forming ink is described as having silver particles dispersed therein, but may be other than silver. Examples of the metal contained in the metal particles include silver, copper, palladium, platinum, gold, and alloys thereof. One or more of these can be used in combination. When the metal particles are an alloy, the metal is mainly used, and an alloy containing another metal may be used. Moreover, the alloy which the said metals mixed with arbitrary ratios may be sufficient. Further, mixed particles (for example, particles in which silver particles, copper particles, and palladium particles are present in an arbitrary ratio) may be dispersed in a liquid. Since these metals have a low resistivity and are stable and are not oxidized by heat treatment, it is possible to form a stable conductor pattern with a low resistance by using these metals.
Further, for example, in the above-described embodiment, the piezo method is used as the droplet discharge method. However, the present invention is not limited to this, and for example, a method of discharging ink by bubbles generated by heating the ink is known. Various techniques can be applied.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
[1] Production of conductor pattern forming ink (Example 1)
17 mL of trisodium citrate dihydrate and 0.36 g of tannic acid were dissolved in 50 mL of water made alkaline by adding 3 mL of 10N-NaOH aqueous solution. To the obtained solution, 3 mL of 3.87 mol / L silver nitrate aqueous solution was added and stirred for 2 hours to obtain a silver colloid solution. The obtained silver colloid solution was desalted by dialysis until the electrical conductivity was 30 μS / cm or less. After dialysis, the coarse metal colloid particles were removed by centrifugation at 3000 rpm for 10 minutes.

  To this silver colloidal solution, polyglycerin (weight average molecular weight: 500) as a polyglycerin compound, maltodextrin (weight average molecular weight: 4100) as a polysaccharide, and Surfynol 104PG-50 (day Shinshin Chemical Industry Co., Ltd.) and Olphine EXP4036 (Nisshin Chemical Industry Co., Ltd.) were added, and ion-exchanged water for adjusting the concentration was further added to prepare a conductor pattern forming ink. The maltodextrin as a polysaccharide used for the preparation of the conductor pattern forming ink was solid at room temperature (25 ° C.).

(Examples 2 to 20)
A conductor pattern forming ink was produced in the same manner as in Example 1 except that the types and materials of the materials used for preparing the conductor pattern forming ink were changed as shown in Table 1.
(Examples 21 to 28)
As the polysaccharide used for the preparation of the conductive pattern forming ink, each of the reduced maltodextrins (weight average molecular weight: 1200) is solid at room temperature (25 ° C.), except that a part of the carbonyl group is reduced. Except for changing the type of material and the material as shown in Table 2, the type and material of each material were changed as shown in Table 2 in the same manner as in Example 1 to produce a conductor pattern forming ink.
(Comparative Examples 1-11)
A conductor pattern forming ink was manufactured in the same manner as in Example 1 except that the types and materials of the materials used for the preparation of the conductor pattern forming ink were changed as shown in Table 2.
Tables 1 and 2 show the compositions of the conductor pattern forming inks of the examples and comparative examples.

[2] Droplet ejection stability evaluation (stable ejection performance evaluation)
[2.1] Evaluation of landing position accuracy Room temperature 25 ° C., relative humidity 50%, the ink jet apparatus as shown in FIGS. 4 and 5 installed in a class 100 clean room, each of the above examples and comparative examples 1 to 8, In the state where 10 conductor pattern forming inks were filled and the drive waveform of the piezo element was optimized, 50,000 droplets (50000 droplets) were continuously discharged from each nozzle of the inkjet head. About 50000 droplets ejected from a designated nozzle near the center of the inkjet head after filling with the conductor pattern forming ink, the amount of deviation d from the center aiming position of the center position of each landed droplet An average value was obtained and evaluated according to the following four criteria. It can be said that the smaller the value is, the more effectively the occurrence of flight bending is prevented.

In addition, it was difficult for the ink for forming a conductor pattern of Comparative Examples 9 and 11 to eject droplets, and thus the landing position accuracy could not be evaluated.
A: The average value of the shift amounts d is less than 0.03 μm.
B: The average value of the shift amount d is 0.03 μm or more and less than 0.08 μm.
C: The average value of the shift amount d is 0.08 μm or more and less than 0.12 μm.
D: The average value of the shift amount d is 0.12 μm or more.

[2.2] Continuous discharge test (clogging evaluation)
The ink for forming a conductor pattern of each of the examples and comparative examples 1 to 8 and 10 was placed in an ink jet apparatus as shown in FIGS. 4 and 5 installed in a clean room of room temperature 25 ° C., relative humidity 50% and class 100. The ink was filled and the ink jet device was continuously operated for 36 hours to discharge the conductor pattern forming ink. About the occurrence rate of nozzle clogging ([(number of clogged nozzles) / (total number of nozzles)] × 100) of nozzles constituting the inkjet head after continuous operation. Then, it was investigated whether or not clogging could be eliminated by a cleaning member made of a plastic material. The results were evaluated according to the following four criteria.
In addition, it was difficult for the conductive pattern forming inks of Comparative Examples 9 and 11 to discharge droplets, and a continuous discharge test (clogging evaluation) could not be performed.

A: No nozzle clogging occurs.
B: The occurrence rate of nozzle clogging is less than 0.5% (excluding zero), and clogging can be eliminated by cleaning.
C: The occurrence rate of nozzle clogging is 0.5% or more and less than 1.0%, and clogging can be eliminated by cleaning.
D: The occurrence rate of nozzle clogging is 1.0% or more, or clogging cannot be eliminated by cleaning.
In addition, said evaluation was performed on the same conditions about each Example and Comparative Examples 1-8, and 10.

[2.3] Evaluation of Stability of Droplet Discharge Amount In the ink jet apparatus as shown in FIGS. 4 and 5 installed in a clean room of room temperature 25 ° C., relative humidity 50%, class 100, In the state where the conductive pattern forming inks of Comparative Examples 1 to 8 and 10 were filled and the drive waveform of the piezo element was optimized, 100,000 droplets (100,000 droplets) were continuously discharged from each nozzle of the inkjet head. It was. For the two designated nozzles on the left and right ends of the inkjet head, the total weight of the ejected droplets was obtained, and the absolute value ΔW [ng] of the difference between the average ejection amounts of the droplets ejected from the two nozzles was obtained. . The ratio (ΔW / W _T ) of this ΔW to the target discharge amount W _T [ng] of the droplet was determined and evaluated according to the following four criteria. As the value of [Delta] W / W _T is small, it can be said that the greater the stability of the droplet discharge amount.

In addition, the conductive pattern forming inks of Comparative Examples 9 and 11 were difficult to eject droplets, and the stability of the droplet ejection amount could not be evaluated.
A: The value of ΔW / _{W T} is less than 0.020.
B: The value of ΔW / _{W T} is 0.020 or more and less than 0.420.
C: The value of ΔW / _{W T} is 0.420 or more and less than 0.720.
D: The value of ΔW / _{W T} is 0.720 or more.

[3] Production and Evaluation of Ceramic Circuit Board The conductor pattern forming inks obtained in the respective Examples and Comparative Examples 1 to 8 and 10 were put into an ink jet apparatus as shown in FIGS. 4 and 5, respectively.
Next, the ceramic green sheet was heated to 60 ° C. and held. Drops of 15 ng per droplet were sequentially discharged from each discharge nozzle, and 20 lines (precursors) having a line width of 35 μm, a thickness of 15 μm, and a length of 10.0 cm were drawn. The distance between each line was 5 mm. And the ceramic green sheet in which this line was formed was put into the drying furnace, and it heated and dried at 60 degreeC for 30 minutes.

  The ceramic green sheet on which the line was formed as described above was used as the first ceramic green sheet. 20 sheets of this first ceramic green sheet were prepared for each ink. Each sheet was checked for cracks. The results are shown in Table 3. Table 3 shows the number of non-defective products having no cracks in the line among the first ceramic green sheets.

  Next, through holes having a diameter of 100 μm were formed in a total of 40 locations by punching another ceramic green sheet with mechanical punches or the like at both ends of the metal wiring, and each of the obtained Examples and Comparative Examples Contacts (vias) were formed by filling 1 to 8 and 10 conductor pattern forming inks. Further, a 2 mm square pattern is formed on the contact (via), and a terminal portion is formed by using the above-described droplet discharge device using the conductive pattern forming inks of the respective Examples and Comparative Examples 1 to 8 and 10. did.

The ceramic green sheet on which this terminal portion was formed was used as the second ceramic green sheet.
Next, the first ceramic green sheet was laminated under the second ceramic green sheet, and two unprocessed ceramic green sheets were laminated as reinforcing layers to obtain a raw laminate. This raw laminate was prepared for each of the 20 first ceramic green sheets for each ink, and 20 blocks were prepared for each ink.

Next, the raw laminate was pressed at a temperature of 95 ° C. at a pressure of 250 kg / cm ² for 30 minutes, and then in the atmosphere at a temperature rising rate of 66 ° C./hour for about 6 hours and a temperature rising rate of 10 ° C. / The ceramic circuit is sintered according to a sintering profile in which the temperature is continuously raised, such as about 5 hours in time and about 4 hours at a rate of temperature increase of 85 ° C./hour, and then held at a maximum temperature of 890 ° C. for 30 minutes. A substrate was obtained.
After cooling, for each ceramic circuit board, a tester was applied between the terminal portions formed on the 20 conductor patterns to confirm the presence or absence of conduction, and those with a conductivity of 100% were regarded as non-defective products. The conductivity was obtained by dividing the number of conductive patterns in each ceramic circuit board by the number of formed conductive patterns (20).

[4] Production and Evaluation of Ceramic Circuit Board The conductor pattern forming inks obtained in the respective Examples and Comparative Examples 1 to 8 and 10 were put into an ink jet apparatus as shown in FIGS. 4 and 5, respectively.
Next, the ceramic green sheet was heated to 60 ° C. and held. Drops of 15 ng per droplet were sequentially discharged from each discharge nozzle, and 20 lines (precursors) having a line width of 35 μm, a thickness of 15 μm, and a length of 10.0 cm were drawn. The distance between each line was 5 mm. A 1.5 mm square pattern was formed at both ends of each line to form terminal portions. And the ceramic green sheet in which this line was formed was put into the drying furnace, and it heated and dried at 60 degreeC for 30 minutes.
The ceramic green sheet on which the line was formed as described above was used as the first ceramic green sheet. 20 sheets of this first ceramic green sheet were prepared for each ink.

Next, three unprocessed ceramic green sheets were laminated as reinforcing layers under the first ceramic green sheet to obtain a raw laminate. This raw laminate was prepared for each of the 20 first ceramic green sheets for each ink, and 20 blocks were prepared for each ink. The raw laminate was then pressed for 30 minutes at a temperature of 95 ° C. and a pressure of 250 kg / cm ² . About each block, it was confirmed whether the line width of a line had a deformation | transformation by a press process. For the determination, those having no deformation of 10 μm or more with respect to the line width of 35 μm after drawing are regarded as non-defective products, and the results are shown in Table 3. Table 3 shows the number of non-defective products.

Next, in the atmosphere, the temperature is increased continuously at a temperature rising rate of 66 ° C./hour for about 6 hours, a temperature rising rate of 10 ° C./hour for about 5 hours, and a temperature rising rate of 85 ° C./hour for about 4 hours. The ceramic circuit board was obtained through a temperature process and sintering according to a sintering profile of holding at a maximum temperature of 890 ° C. for 30 minutes.
After cooling, for each ceramic circuit board, a tester was applied between the terminal portions formed on the 20 conductor patterns to confirm the presence or absence of conduction, and those with a conductivity of 100% were regarded as non-defective products. The conductivity was obtained by dividing the number of conductive patterns in each ceramic circuit board by the number of formed conductive patterns (20).
These results are shown in Table 3.

As shown in Table 3, the conductor pattern forming ink of the present invention was excellent in ejection stability. In addition, the conductor pattern and the wiring board formed using the conductor pattern forming ink of the present invention showed excellent electrical conductivity and high reliability. On the other hand, in the comparative example, a satisfactory result was not obtained.
Further, when the content of the silver colloid particles in the ink was changed to 20 wt% and 30 wt%, the same result as above was obtained.

  DESCRIPTION OF SYMBOLS 1 ... Conductor pattern formation ink (ink) 10 ... Conductor pattern precursor (precursor) 15 ... Ceramic molding (ceramics green sheet) 16 ... Contact precursor 17 ... Laminate 20, 20A ... Conductor pattern (circuit) 30 ... Ceramic circuit board (wiring board) 31 ... Ceramics board 32 ... Laminated board 33 ... Contact 100 ... Inkjet device (droplet ejection device) 110 ... Inkjet head (droplet ejection head, head) 111 ... Head body 112 ... Vibration plate 113 ... Piezo element 114 ... body 115 ... nozzle plate 115P ... ink ejection surface 116 ... reservoir 117 ... ink chamber 118 ... nozzle (protruding part) 130 ... base 140 ... table 170 ... table positioning means 171 ... first moving means 172 ... mode 180 ... head positioning means 181: second moving means 182 ... linear motor 183,184,185 ... motor 190 ... controller 191 ... driving circuit S ... substrate

Claims (8)

A conductive pattern forming ink that is applied to a ceramic molded body composed of a material containing ceramic particles and a binder by a droplet discharge method, and is used to form a conductive pattern,
Metal particles,
An aqueous dispersion medium in which the metal particles are dispersed;
A water-soluble polysaccharide having a weight average molecular weight of 1,000 or more and 5,000 or less;
A polyglycerin compound having a polyglycerin skeleton,
The content of the polysaccharide in the conductor pattern forming ink is 1.0 wt% or more and 28 wt% or less,
The content of the polyglycerin compound in the conductive pattern forming ink is 1.0% by weight or more and 28% by weight or less,
An ink for forming a conductor pattern, wherein the viscosity at 25 ° C. is 20 mPa · s or less.   When the content of the polyglycerin compound in the conductor pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductor pattern forming ink is X (B) [wt%], X (B The ink for forming a conductor pattern according to claim 1, satisfying a relationship of A) + X (B) ≦ 28.   When the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductive pattern forming ink is X (B) [wt%], 7. The ink for forming a conductor pattern according to claim 1 or 2, wherein a relationship of 5≤X (A) + 4X (B) is satisfied.   When the content of the polyglycerin compound in the conductive pattern forming ink is X (A) [wt%] and the content of the polysaccharide in the conductive pattern forming ink is X (B) [wt%], 0. 4. The conductive pattern forming ink according to claim 1, wherein a relationship of 12 ≦ X (A) / X (B) ≦ 12 is satisfied.   The ink for forming a conductor pattern according to claim 1, wherein the polysaccharide contains maltodextrin that is solid at room temperature.   The ink for forming a conductor pattern according to claim 1, wherein the polysaccharide includes a polysaccharide having a carbonyl group reduced.   A conductor pattern formed with the conductor pattern forming ink according to claim 1.   A wiring board comprising the conductor pattern according to claim 7.

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