JP2012138526A - Ink for forming conductor pattern, conductor pattern and wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink for forming a conductor pattern that can be ejected stably from a droplet ejection head, and to provide a highly reliable conductor pattern, and a highly reliable wiring board having such a conductor pattern.SOLUTION: An ink 1 for forming a conductor pattern 10 on a substrate by means of a droplet ejection head 110 contains metal particles, an aqueous dispersion medium into which the metal particles are dispersed, and a fatty acid ester of polyethylene glycol. The carbon number of a fatty acid composing the fatty acid ester of polyethylene glycol is 10-20. Content of the fatty acid ester of polyethylene glycol is preferably 0.1-5 wt%.

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, there has been a demand for higher density of circuit boards by finer wiring and narrower pitch, but screen printing is disadvantageous for finer wiring and narrower pitch. Difficult to meet demand. 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). According to this method, it is possible to form a fine conductor pattern as compared with the conventional method, which is advantageous in improving the circuit density.

  However, the ink used for forming the conductor pattern (industrial use) is more limited in composition than ink used in printers (consumer use), and characteristics such as drying and re-dissolvability are not sufficient. However, solid content such as metal particles precipitates or aggregates and adheres to the discharge portion of the droplet discharge head, which may cause clogging, resulting in frequent flying bending of droplets.

JP 2007-84387 A

  An object of the present invention is to provide a conductor pattern forming ink that can be stably ejected from a droplet ejection head, to provide a highly reliable conductor pattern, and to provide such a conductor pattern with reliability. It is to provide a wiring board having high height.

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 for forming a conductive pattern on a substrate by a droplet discharge method,
Metal particles, an aqueous dispersion medium in which the metal particles are dispersed, and a fatty acid ester of polyethylene glycol,
The fatty acid constituting the polyethylene glycol fatty acid ester has 10 to 20 carbon atoms.
Thereby, it is possible to provide a conductive pattern forming ink that can be stably discharged from the droplet discharge head.

In the ink for forming a conductor pattern of the present invention, the content of the fatty acid ester of polyethylene glycol is preferably 0.01 wt% or more and 5 wt% or less.
Thereby, in the ceramic molded body, the affinity of the conductive pattern forming ink can be different between the region to which the composition containing the polyhydric alcohol condensate is applied and the other region. Excessive wetting and spreading of the conductor pattern forming ink on the ceramic molded body can be prevented, and wiring having a smaller line width can be more suitably formed.

The ink for forming a conductor pattern of the present invention preferably further contains a sugar alcohol or a polysaccharide.
This further improves the ejection stability of the ink droplets.
In the ink for forming a conductor pattern of the present invention, the content of the sugar alcohol or polysaccharide is preferably 3 wt% or more and 20 wt% or less.
Thereby, volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be more reliably suppressed, and the conductor pattern forming ink has particularly excellent droplet discharge stability over a longer period of time.

In the conductive pattern forming ink of the present invention, the conductive pattern forming ink is a colloid liquid in which metal colloidal particles composed of the metal particles and a dispersant attached to the surface of the metal particles are dispersed in the aqueous dispersion medium. Preferably there is.
As a result, the dispersibility of the metal particles in the aqueous dispersion medium is particularly excellent, and the ink ejection stability is 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 the wiring board (ceramics circuit board) of this invention. It is explanatory drawing which shows the schematic process of the manufacturing method of the wiring board (ceramics circuit board) shown in FIG. It is a manufacturing process explanatory drawing of the wiring board (ceramics circuit board) of FIG. 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.
Hereinafter, preferred embodiments of the present invention will be described in detail.
<Conductor pattern forming ink>
The ink for forming a conductor pattern of the present invention is an ink used for forming a conductor pattern on a substrate, and in particular, an ink used for forming a conductor pattern by a droplet discharge method.

  The substrate on which the conductor pattern is formed may be any material, but in this embodiment, a ceramic substrate is used as the substrate. In the present embodiment, the description will be made assuming that the ink for forming a conductor pattern is applied to a sheet-like ceramic formed body (ceramic green sheet) made of a material containing ceramics and a binder. The ceramic formed body and the ink applied to the ceramic formed body are sintered as described later to become a ceramic substrate and a conductor pattern, respectively.

Hereinafter, preferred embodiments of the conductor pattern forming ink will be described. 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.
The conductive pattern forming ink (hereinafter, also simply referred to as ink) contains an aqueous dispersion medium, silver particles (metal particles) dispersed in the aqueous dispersion medium, and a polyethylene glycol fatty acid ester as described later.

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 specification, the “aqueous dispersion medium” refers to one composed of water and / or a liquid excellent in compatibility with water (for example, a liquid having a solubility in 100 g of water at 25 ° C. 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.
Further, 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 50 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 diameter of the silver particles is preferably 1 nm or more and 100 nm or less, and more preferably 10 nm or more and 30 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.

In the ink, the average distance between silver particles is preferably 1.7 nm or more and 380 nm or less, and more preferably 1.75 nm or more and 300 nm or less. Thereby, the viscosity of the conductor pattern forming ink can be made more appropriate, and the discharge stability is particularly excellent.
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, it is possible to more effectively prevent disconnection of the conductor pattern while maintaining high ejection stability of the conductor pattern forming ink, and it is possible to provide a more reliable conductor pattern.
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 dispersant is not particularly limited, but may contain a hydroxy acid or a salt thereof having three or more COOH groups and OH groups in total and having the same or more COOH groups as the OH groups. preferable. 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, the silver particles are uniformly distributed in the pattern (precursor) formed by the 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.
Such dispersants include, for example, citric acid, malic acid, trisodium citrate, tripotassium citrate, trilithium citrate, triammonium citrate, disodium malate, tannic acid, gallotannic acid, pentaploid tannin and the like. 1 type or 2 types or more of them can be used in combination.

  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 fine 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, the silver particles are uniformly distributed in the pattern (precursor) formed by the 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.

  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 adhering to the surface, the reducing agent (residual reducing agent) described later, etc. are oxidatively decomposed, and most of them are gasified and disappear. Since the amount of the residual reducing agent is considered to be small, 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, it is effective for a ceramic substrate that is sintered at a higher temperature.
The formation of silver colloid particles will be described in detail later.

<Fatty acid ester of polyethylene glycol>
The ink for forming a conductor pattern of the present invention includes a fatty acid ester of polyethylene glycol (hereinafter also referred to as polyethylene glycol fatty acid ester) which is a condensate of polyethylene glycol and a fatty acid having 10 to 20 carbon atoms. It has characteristics.
By the way, the ink used for forming a conventional conductor pattern (industrial use) is more limited in composition and has characteristics such as drying and re-dissolvability than those used in printers (consumer use). Insufficient solid matter such as metal particles is deposited or aggregated and adheres to the discharge portion of the droplet discharge head, which may cause clogging, resulting in frequent flight bending of droplets.

On the other hand, the present invention uses the conductive pattern forming ink containing the polyethylene glycol fatty acid ester as described above, thereby preventing adhesion and aggregation of metal particles to a member such as metal or glass in the droplet discharge head. Growth and the like can be suppressed, and droplets can be discharged stably. This is because the polyethylene glycol fatty acid ester adheres to the member first to prevent adhesion of metal particles, and the polyethylene glycol fatty acid ester functions as a dispersion aid to prevent aggregation of the metal particles. This is considered to be due to such reasons.
As described above, by using the conductor pattern forming ink of the present invention, adhesion of metal particles into the droplet discharge head and aggregation of the metal particles can be suppressed, and a highly reliable conductor pattern is formed. be able to.

As described above, the number of carbon atoms of the fatty acid component constituting the polyethylene glycol fatty acid ester is 10 or more and 20 or less. When the number of carbon atoms of the fatty acid component is less than the lower limit, the adhesion of metal particles into the droplet discharge head and the aggregation of metal particles cannot be sufficiently prevented. On the other hand, if the number of carbon atoms of the fatty acid component exceeds the upper limit, the storage stability of the conductor pattern forming ink may be lowered.
Thus, although the carbon number of the fatty acid component which comprises polyethyleneglycol fatty acid ester is 10-20, it is more preferable that it is 12-18. Thereby, the effect of this invention becomes a more remarkable person.

Examples of the polyethylene glycol fatty acid ester include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol monooleate, polyethylene glycol distearate, and the like.
Among the above-mentioned, it is preferable to use a monoester, and it is more preferable to use polyethylene glycol monolaurate. As a result, it is possible to more effectively suppress the adhesion of the metal particles into the droplet discharge head and more reliably suppress the aggregation of the metal particles.
The content of the polyethylene glycol fatty acid ester as described above is preferably 0.01 wt% or more and 5 wt% or less, and more preferably 0.1 wt% or more and 1 wt% or less. Thereby, adhesion of metal particles into the droplet discharge head can be more efficiently suppressed, and aggregation of metal particles can be more effectively suppressed.

<Other ingredients>
In addition to the above components, the conductor pattern forming ink of the present invention may contain an organic binder. The organic binder prevents aggregation of silver particles in a pattern formed by the conductor pattern forming ink. That is, in the formed pattern, the organic binder is present between the silver particles, so that the silver particles can be prevented from agglomerating and a crack (crack) can be prevented from being generated in a part of the pattern. Further, at the time of sintering, the organic binder can be decomposed and removed, and silver particles in the pattern are bonded to form a conductor pattern.

  By including the organic binder in this manner, it is possible to prevent the formed conductor pattern from being cracked, but in general, such an organic binder tends to aggregate in the ink. However, by including the above-described polyethylene glycol fatty acid ester in the ink, the dispersion stability of the organic binder in the aqueous dispersant can be improved, and unintentional aggregation of the organic binder can be prevented. .

Although it does not specifically limit as an organic binder, For example, polyethyleneglycol # 200 (weight average molecular weight 200), polyethyleneglycol # 300 (weight average molecular weight 300), polyethyleneglycol # 400 (average molecular weight 400), polyethyleneglycol # 600 ( Weight average molecular weight 600), 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), etc. Polyethylene glycol, polyvinyl alcohol # 200 (weight average molecular weight: 200), polyvinyl alcohol # 300 (weight average molecular weight: 300), polyvinyl alcohol # 400 (average 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), polyvinyl alcohol such as polyvinyl alcohol # 2000 (weight average molecular weight: 2000), polyglycerol compounds having a polyglycerol skeleton such as polyglycerol, polyglycerol ester, etc. Alternatively, two or more kinds can be used in combination. Examples of the polyglycerol ester include polyglycerol monostearate, tristearate, tetrastearate, monooleate, pentaoleate, monolaurate, monocaprylate, polycinnolate, sesquistearate, decaoleate, and sesquioleate. Etc.
Among these, when a polyglycerin compound is used as the organic binder, the following effects can be obtained.

  The polyglycerin compound particularly suitably prevents the pattern from cracking when a pattern (a conductor pattern precursor, which will be described in detail later) formed by the conductor pattern forming ink is dried (dedispersion medium). be able to. This is considered as follows. When the polyglycerin compound is contained in the conductive pattern forming ink, polymer chains exist between the silver particles (metal particles), and the polyglycerin compound makes the distance between the silver particles moderate. Can do. Furthermore, since the polyglycerin compound has a relatively high boiling point, it is not removed when the aqueous dispersion medium is removed, and adheres around the silver particles. As described above, at the time of removing the aqueous dispersion medium, the polyglycerin compound continuously encapsulates the silver particles, and as a result, rapid volume shrinkage due to volatilization of the aqueous dispersion medium is avoided and silver grain growth (aggregation) is hindered. It is considered that the occurrence of cracks in the pattern is suppressed.

  Further, the polyglycerin compound can more reliably prevent disconnection from occurring during sintering when forming the conductor pattern. This is considered as follows. Polyglycerin compounds have a relatively high boiling point or decomposition temperature. Therefore, in the process of forming the conductor pattern from the conductor pattern forming ink, after the aqueous dispersion medium evaporates, the polyglycerin compound is not evaporated or thermally (oxidized) decomposed to a relatively high temperature in the pattern. Can exist. Therefore, until the polyglycerin compound evaporates or is thermally (oxidized) decomposed, the polyglycerin compound exists around the silver particles, and the approach and aggregation of the silver particles can be suppressed, and the polyglycerin compound is decomposed. Later, the silver particles can be joined more uniformly. Furthermore, a polymer chain (polyglycerin compound) exists between silver particles (metal particles) in the pattern during sintering, and the polyglycerin compound can keep the distance between the silver particles. Moreover, this polyglycerin compound has moderate fluidity | liquidity. For this reason, by including a polyglycerin compound, the precursor of the conductor pattern has excellent followability to expansion / contraction due to temperature change of the ceramic molded body.

From the above, it is considered that disconnection of the formed conductor pattern can be more reliably prevented.
Moreover, by including such a polyglycerin compound, the viscosity of the ink can be made more appropriate, and the ejection stability from the ink jet head can be improved more effectively. In addition, film formability can be improved.

  Among the above-mentioned polyglycerin compounds, polyglycerin is preferably used. Polyglycerin is a component that is particularly excellent in the ability to follow expansion and contraction due to temperature changes of the ceramic molded body, and can be more reliably removed from the conductor pattern after the ceramic molded body is sintered. 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 organic binder preferably has a weight average molecular weight of 300 or more and 3000 or less, more preferably 400 or more and 1000 or less, and still more preferably 400 or more and 600 or less. Thereby, when the pattern formed with the conductor pattern forming ink is dried, the occurrence of cracks can be more reliably prevented. In addition, when the sugar alcohol is included in the ink as described later, the affinity between the organic binder and the sugar alcohol becomes sufficiently high, and the pattern formed by the ink has a fluidity for a longer period during sintering. It can be maintained, and the followability to shrinkage and expansion due to temperature change of the ceramic molded body is particularly excellent. On the other hand, when the weight average molecular weight of the organic binder is less than the lower limit, depending on the composition of the organic binder, the organic binder tends to be decomposed when removing the aqueous dispersion medium, thereby preventing the occurrence of cracks. The effect is reduced. When the weight average molecular weight of the organic binder exceeds the upper limit, the solubility and dispersibility in the ink may be reduced depending on the composition of the organic binder due to the excluded volume effect or the like.

Further, the content of the organic binder in the ink is preferably 1 wt% or more and 30 wt% or less, and more preferably 5 wt% or more and 20 wt% or less. This makes it possible to more effectively prevent the occurrence of cracks and disconnections while making the ink ejection stability particularly excellent. On the other hand, when the content of the organic binder is less than the lower limit, the effect of preventing the occurrence of cracks may be reduced depending on the composition of the organic binder. If the content of the organic binder exceeds the upper limit, it may be difficult to make the viscosity of the ink sufficiently low depending on the composition of the organic binder.
Further, the conductor pattern forming ink may contain sugar alcohol or polysaccharide in addition to the above components.

  Sugar alcohol and polysaccharide are components that can contribute to preventing volatilization of the aqueous dispersion medium of the conductor pattern forming ink. When the conductive pattern forming ink contains a sugar alcohol or a polysaccharide, it is possible to more reliably prevent the aqueous dispersion medium from volatilizing in the vicinity of the discharge part of the ink jet device, and to suppress the increase in the viscosity of the ink and the drying. As a result, the ejection stability of the ink droplets is further improved due to a synergistic effect with the effect of including the above-described polyethylene glycol fatty acid ester.

  In addition, since sugar alcohols and polysaccharides have a large number of oxygen per molecular weight, they are easily decomposed and removed when the atmosphere reaches the decomposition temperature of sugar alcohols and polysaccharides. For this reason, when forming a conductor pattern, by making the temperature of the conductor pattern higher than the decomposition temperature of sugar alcohol and polysaccharide, sugar alcohol and polysaccharide are reliably removed (oxidative decomposition) from within the conductor pattern. be able to.

  Examples of sugar alcohols include threitol, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, arabitol, ribitol, xylitol, sorbitol, mannitol, threitol, glycol, tallitol, galactitol, allitol, altritol, dolitol, iditol. Glycerin (glycerol), inositol, maltitol, isomaltitol, lactitol, tranitol and the like, and one or more of these can be used in combination.

  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.

The polysaccharide is preferably 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 preferably 1,000 or more and 5,000 or less, more preferably 1,200 or more and 4,500 or less, and 1,500 or more and 4,000 or less. Is more preferable.

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 content of the sugar alcohol or polysaccharide as described above in the conductive pattern forming ink is preferably 3 wt% or more and 20 wt% or less, and more preferably 5 wt% or more and 15 wt% or less. Thereby, volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be more reliably suppressed, and the conductor pattern forming ink has particularly excellent droplet discharge stability over a longer period of time.

  In addition to the above components, the conductive pattern forming ink may contain an acetylene glycol compound. The acetylene glycol-based compound has a function of adjusting the contact angle between the conductor pattern forming ink and the ceramic molded body within a predetermined range. Further, the contact angle between the conductor pattern forming ink and the ceramic molded body can be adjusted within a predetermined range with a small amount of the acetylene glycol compound. Thus, a finer conductor pattern can be formed by adjusting the contact angle between the conductor pattern forming ink and the ceramic molded body within a predetermined range. Further, even when bubbles are mixed in the discharged droplets, the bubbles can be quickly removed. As a result, generation of cracks and disconnections in the formed conductor pattern can be more effectively prevented.

  Specifically, the compound has a function of adjusting the contact angle between the conductor pattern forming ink and the ceramic molded body to 40 ° or more and 80 ° or less (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.

Examples of acetylene glycol compounds include Surfynol 104 series (104E, 104H, 104PG-50, 104PA, etc.), Surfynol 400 series (420, 465, 485, etc.), Olphine series (EXP4036, EXP4001, E1010, etc.). ("Surfinol" and "Orphine" are trade names of Nissin Chemical Industry Co., Ltd.) and the like, and one or more of these can be used in combination.
The ink preferably contains two or more acetylene glycol compounds having different HLB values. The contact angle between the conductor pattern forming ink and the ceramic molded body can be easily adjusted within a predetermined range.

  In particular, the difference between the HLB value of the acetylene glycol compound having the highest HLB value and the HLB value of the acetylene glycol compound having the lowest HLB value among two or more kinds of acetylene glycol compounds contained in the ink is 4 It is preferably 12 or more and more preferably 5 or more and 10 or less. Accordingly, the contact angle between the conductor pattern forming ink and the ceramic molded body can be easily adjusted within a predetermined range with a smaller amount of the acetylene glycol compound.

When an ink containing two or more acetylene glycol compounds is used, the HLB value of the acetylene glycol compound having the highest HLB value is preferably 8 or more and 16 or less, and preferably 9 or more and 14 or less. More preferred.
Moreover, when using what contains 2 or more types of acetylene glycol type compounds in an ink, it is preferable that the HLB value of the acetylene glycol type compound with the lowest HLB value is 2-7, and it is 3-5. Is more preferable.

The content of the acetylene glycol compound contained in the ink is preferably 0.001 wt% or more and 1 wt% or less, more preferably 0.01 wt% or more and 0.5 wt% or less. As a result, the contact angle between the conductor pattern forming ink and the ceramic molded body can be more effectively adjusted to a predetermined range.
Further, the conductor pattern forming ink may contain 1,3-propanediol in addition to the above components. As a result, volatilization of the aqueous dispersion medium in the vicinity of the ejection portion of the inkjet head can be more effectively suppressed, the viscosity of the ink can be made more appropriate, and ejection stability is further improved.

When 1,3-propanediol is contained in the ink, the content is preferably 0.5 wt% or more and 20 wt% or less, and more preferably 2 wt% or more and 10 wt% or less. Thereby, the ejection stability of ink can be improved more effectively.
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 may contain a polyhydric alcohol such as ethylene glycol, 1,3-butylene glycol, or propylene glycol.

<< 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 in the silver salt such as silver nitrate as a starting material to the dispersing agent 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. As a specific blending amount, 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 or more and 12 or less after preparing the aqueous solution by dissolving the dispersant and the reducing agent.

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 or more and 5 or less, which is 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 target colloidal particles and the ratio reduced by the reducing agent. For example, in the case of silver nitrate, 15 parts by weight with respect to 100 parts by weight of the aqueous solution. The amount is preferably about 70 parts by weight or less.

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 polyethylene glycol fatty acid ester as described above to the aqueous solution in which silver colloidal particles obtained as described above are dispersed, a conductive pattern forming ink (the conductive pattern forming ink of the present invention) is added. )
In addition, the addition time of other components, such as polyethyleneglycol fatty acid ester, is not specifically limited, and may be any time after the formation of the silver colloid particles.

<< Conductor pattern and wiring board >>
Next, the conductor pattern and the wiring board will be described in detail.
FIG. 1 is a longitudinal sectional view showing an example of a wiring board according to the present invention.
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) 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 with the conductor pattern forming ink 1 as described above. The conductive pattern is formed by bonding metal particles to each other, and at least on the surface of the conductive pattern, the metal particles are bonded with no gap.

The specific resistance of the conductor pattern 20 is preferably less than 20 μΩcm, and more preferably 15 μΩcm or less. The specific resistance at this time refers to the specific resistance after heating and drying at 160 ° C. after ink application. When the specific resistance is 20 μΩcm or more, it becomes difficult to use it for applications requiring electrical conductivity, that is, for electrodes formed on a circuit board.
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 manufactured using the above-described conductor pattern forming ink of the present invention, it 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 preferred embodiment of the method for manufacturing a wiring board of the present invention will be described.
FIG. 2 is an explanatory view showing a schematic process of the method for manufacturing the wiring board (ceramic circuit board) shown in FIG. 1, and FIG. 3 is a process explanatory view of the method for manufacturing the wiring board (ceramic circuit board) shown in FIG. is there.

  The method of manufacturing a wiring board according to the present embodiment includes a step of preparing a plurality of sheet-like ceramic molded bodies 15 made of a material including a ceramic material and a binder (ceramic molded body preparing step), Step of forming conductor pattern precursor 10 by discharging conductive pattern forming ink 1 containing metal particles and a dispersion medium in which metal particles are dispersed on at least one surface by a droplet discharge method (conductor pattern precursor 10) Forming step), a step of laminating a plurality of ceramic molded bodies 15 to obtain a laminate 17 (lamination step), and a step of heating the laminate 17 to obtain a wiring substrate 30 having the conductor pattern 20 and the ceramic substrate 31. (Firing step).

Hereinafter, each step will be described in detail.
[Ceramic molded body preparation process (ceramic molded body forming process)]
In this step, a plurality of sheet-like ceramic molded bodies (ceramic green sheets) 15 made of a material containing a ceramic material and a binder are prepared.
The ceramic molded body 15 becomes a ceramic substrate 31 by being sintered as described later.
The ceramic molded body 15 is formed as follows, for example.

First, as shown in FIG. 2, as a raw material powder, ceramic powder (ceramic material) made of alumina (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), or the like having an average particle diameter of 1 μm to 2 μm, and average particles A glass powder made of borosilicate glass having a diameter of 1 μm or more and 2 μm or less is prepared, and these are mixed at an appropriate mixing ratio, for example, a weight ratio of 1: 1.
Thus, the following effects are acquired by including a glass material as a material of the ceramic molded body 15. The glass material melts during sintering and has a function of fixing and closely contacting the ceramic substrate 31 on which the conductor pattern 20 is formed. For this reason, the conductor pattern 20 and the wiring board 30 to be formed are more reliable.

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, the conductive pattern forming ink as described above can be used. The filling of the thick film conductive paste may be performed in this step, may be performed in a conductor pattern precursor forming step described later, or is performed after the conductor pattern precursor forming step. It may be a thing.
Thus, a plurality of ceramic molded bodies 15 are prepared.

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

In this embodiment, the conductive pattern forming ink can be ejected by using an ink jet apparatus (droplet ejecting apparatus) 100 as described later. Since the ink 1 (ink for forming a conductor pattern of the present invention) is excellent in ejection stability, the ink 1 is ejected to a desired location on the ceramic molded body 15 (substrate S) with a desired amount and with high accuracy. Can be arranged.
The formed conductor pattern precursor 10 may be further dried. 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.

Further, after applying ink 1 by the droplet discharge method, the ceramic molded body 15 is heated to evaporate the aqueous 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 process. 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.
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 laminated ceramic green sheets 15 are packaged and sealed in a polyethylene pack, and then the ceramic molded bodies 15 are pressure-bonded to each other while being heated to a temperature higher than the glass transition point of the binder constituting the ceramic molded bodies 15 by an isostatic press. To do. Thereby, the laminated body 17 is obtained.

[Heating process]
Next, when the laminated body 17 is formed in this way, after being opened from the polyethylene pack, heat treatment is performed by, for example, a belt furnace. 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 less.
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 conductor pattern forming ink of the present invention is used, the obtained conductor pattern 20 is highly reliable. Further, the manufactured ceramic circuit board 30 is also highly reliable.

<Droplet discharge head and droplet discharge device>
Next, a droplet discharge device (inkjet device) used in the above-described wiring board manufacturing method will be described with reference to the drawings.
FIG. 4 is a perspective view illustrating a schematic configuration of a droplet discharge device (inkjet device), and FIG. 5 is a schematic diagram illustrating a schematic configuration of a droplet discharge head. 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 droplet discharge device (inkjet device) 100 is a device for discharging a conductor pattern forming ink 1 onto a substrate S (ceramic molded body 15) to form a conductor pattern.
The droplet discharge device 100 includes a droplet discharge head (inkjet 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 shown in FIG. Means 180.

The base 130 is a table that supports each component of the droplet discharge device 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 (conductor pattern forming ink) 1 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 in the base 130, and thereby determines the position of the ceramic green sheet 15 in 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, the discharge position of ink 1 is controlled by adjusting the waveform of the applied voltage generated by the drive circuit 191, or the discharge position of the ink 1 onto the substrate S is controlled by controlling the head positioning unit 180 and the table positioning unit 170. 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).

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 many metals 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.

  For example, in the above-described embodiment, it has been described that the conductive pattern forming ink is applied to the ceramic molded body and sintered to form the ceramic substrate and the conductive pattern. However, the ink is applied to other than the ceramic molded body. The conductor pattern may be formed. As a board | substrate used for formation of a conductor pattern, it does not specifically limit as a board | substrate, For example, the board | substrate etc. which consist of a ceramic sintered compact, an alumina sintered compact, a polyimide resin, a phenol resin, a glass epoxy resin, glass etc. are mentioned. . Further, the conductive pattern forming ink may be directly applied to the ceramic substrate.

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] Preparation of Conductive Pattern Forming Ink The conductive pattern forming inks in each Example and Comparative Example were manufactured as follows.

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 colloid solution, polyethylene glycol monolaurate (trade name “Emanon 1112” manufactured by Kao Corporation), sugar alcohol shown in Table 1, polyglycerin, and Surfynol 104PG-50 (Nissin) 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 conductive pattern forming ink.

(Examples 2 to 10)
A conductor pattern forming ink was prepared in the same manner as in Example 1 except that the types and amounts of materials used for preparing the conductor pattern forming ink were as shown in Table 1.
(Comparative example)
A conductor pattern forming ink was produced in the same manner as in Example 1 except that the polyethylene glycol fatty acid ester was not added.

  Table 1 shows the compositions of the conductive pattern forming inks of the examples and comparative examples. In the table, 1111 is Emanon 1112, 3199 is polyethylene glycol monostearate (trade name “Emanon 3199V”, manufactured by Kao Corporation), 4110 is polyethylene glycol monooleate Kao, trade name “Emanon 4110”), polyethylene glycol Distearate Kao, trade name “Emanon 3299V”) is indicated as 3299, xylitol as XY, sorbitol as SB, maltodextrin (Mw: 2000) as MD, and reduced maltodextrin (Mw: 2500) as LMD.

[2] Production of Ceramic Green Sheet First, a ceramic green sheet (ceramic molded body) was prepared as follows.
1 ceramic powder composed of alumina (Al ₂ O ₃ ) and titanium oxide (TiO ₂ ) having an average particle diameter of about 1 to 2 μm, and glass powder composed of borosilicate glass and the like having an average particle diameter of about 1 to 2 μm. : A mixture obtained by mixing at a weight ratio of 1 and adding polyvinyl butyral as a binder (binder) and dibutyl phthalate as a plasticizer, mixing and stirring, and forming a slurry on a PET film with a doctor blade Was used as a ceramic green sheet and cut into a square shape with a side length of 200 mm.

[3] Adhesion evaluation Only the nozzle plate was removed from the head, and the initial weight was measured with a precision balance. Next, the ink for forming a conductor pattern obtained in each example and comparative example was poured into a petri dish, the nozzle plate whose initial weight was measured was immersed, and left for 7 days in an atmosphere of 25 ° C. and humidity: 50%. .
Thereafter, the nozzle plate was taken out of the ink for forming the conductor pattern after being left, washed and dried, and then the weight of the nozzle plate was measured using a precision balance, and the adhesion was evaluated according to the following four criteria.

A: The rate of change in weight after 7 days from the initial weight is 0.05% or less in absolute value.
B: The rate of change in weight after 7 days from the initial weight is more than 0.05% and 0.2% or less in absolute value.
C: The rate of change in weight after 7 days from the initial weight is greater than 0.2% and 0.5% or less in absolute value.
D: The rate of change in weight after 7 days from the initial weight is greater than 0.5% in absolute value.

[4] Evaluation of droplet discharge stability The ink for forming a conductor pattern obtained in each of the examples and comparative examples was put into an ink jet apparatus as shown in FIGS. First, drawing was performed using the above-described inkjet device equipped with the above-described conductor pattern forming ink, and it was confirmed that the ink was stably ejected. Next, the ink jet apparatus was left for one week in a clean room environment of a room temperature of 35 ° C., a relative humidity of 50%, and a class 100 in a standby state in which the ink jet head was removed from the drawing position. Next, the inkjet apparatus was turned on, and a solid pattern was drawn on 30 ceramic green sheets obtained as described above. When the ejection of ink became unstable, a predetermined cleaning function mounted on the ink jet apparatus was used to return to a stable ejection state. The above operation was performed and the ejection stability was evaluated according to the following evaluation criteria.

A: No nozzle clogging occurs during drawing, and ink is stably ejected. (Discharge stability is good.)
B: Clogging occurs during drawing, and cleaning operations within two times are required until ink ejection is stabilized. (There is no practical problem.)
C: Clogging occurs during drawing, and three or more cleaning operations are required until ink ejection is stabilized. (Practical possible.)
D: Clogging occurs during drawing and does not recover even by a cleaning operation. (Not practical.)
Further, the same operation as described above was performed with the period of the standby state being 30 days, and the same evaluation as above was performed.

[5] Fabrication and Evaluation of Ceramic Circuit Board The conductor pattern forming inks obtained in the respective examples and comparative examples were put into an ink jet apparatus as shown in FIGS. Next, the ink jet apparatus was left for one week in a clean room environment of a room temperature of 35 ° C., a relative humidity of 50%, and a class 100 in a standby state in which the ink jet head was removed from the drawing position.

  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 40 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 2. Table 2 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 A contact (via) was formed by filling the conductive pattern forming ink. Further, a 2 mm square pattern was formed on the contact (via), and the terminal portion was formed using the above-described droplet discharge device using the conductive pattern forming inks of the respective Examples and Comparative Examples.
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 is laminated under the second ceramic green sheet, and two non-processed ceramic green sheets are laminated as a reinforcing layer, and then at a temperature of 95 ° C., 250 kg / cm. ^The raw laminate was obtained by pressing at a pressure of ² for 30 minutes. Twenty such raw laminates were produced for each of the examples and comparative examples.

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 2.

As shown in Table 2, the conductive 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 (7)

Conductor pattern forming ink for forming a conductor pattern on a substrate by a droplet discharge method,
Metal particles, an aqueous dispersion medium in which the metal particles are dispersed, and a fatty acid ester of polyethylene glycol,
The conductive pattern forming ink, wherein the fatty acid constituting the fatty acid ester of polyethylene glycol has 10 to 20 carbon atoms.   2. The conductive pattern forming ink according to claim 1, wherein a content of the fatty acid ester of polyethylene glycol is 0.01 wt% or more and 5 wt% or less.   The ink for forming a conductor pattern according to claim 1, further comprising a sugar alcohol or a polysaccharide.   4. The conductive pattern forming ink according to claim 3, wherein a content of the sugar alcohol or polysaccharide is 3 wt% or more and 20 wt% or less.   5. The conductive pattern forming ink is a colloid liquid in which metal colloidal particles composed of the metal particles and a dispersant attached to the surface of the metal particles are dispersed in the aqueous dispersion medium. The ink for forming a conductor pattern according to the description.   A conductor pattern formed with the conductor pattern forming ink according to claim 1.   A wiring board comprising the conductor pattern according to claim 6.

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