JP2009298913A - Conductor pattern-forming ink, conductor pattern and wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor pattern-forming ink which can be stably discharged from a droplet-discharging head, a high reliability conductor pattern, and a high reliability wiring substrate having this conductor pattern. <P>SOLUTION: This conductor pattern-forming ink forms a conductor pattern on a base by the droplet-discharging method and comprises metal particles, an aqueous dispersion medium in which the metal particles are dispersed, and a compound represented by formula (I): RNH-CO-NHR' (wherein R and R' are each H or an alkyl group). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  For example, a photolithography method is used for manufacturing a wiring used for an electronic circuit or an integrated circuit. In this photolithography method, a photosensitive material called a resist is coated on a substrate coated with a conductive film in advance, a circuit pattern is irradiated and developed, and the conductive film is etched according to the resist pattern, thereby forming a wiring made of a conductor pattern. Is formed. This photolithography method requires large-scale equipment such as a vacuum apparatus and a complicated process, and the material use efficiency is about several percent, and most of it must be discarded, and the manufacturing cost is high.

  On the other hand, a method of forming a conductor pattern (wiring) by using a droplet discharge method in which a liquid material is discharged from a liquid discharge head in the form of droplets, a so-called inkjet method has been proposed (for example, see Patent Document 1). ). In this method, a conductive pattern forming ink in which conductive fine particles are dispersed is directly applied to a substrate, and then the solvent is removed and sintered to convert the conductive pattern into a conductive pattern. According to this method, there is an advantage that photolithography is not required, the process is greatly simplified, and the amount of raw materials used is reduced.

  However, with the conventional conductor pattern forming ink, the dispersion medium of the conductor pattern forming ink is in the vicinity of the droplet ejection port of the droplet ejection head (inkjet head) during ejection standby or when ejected continuously for a long time. There has been a problem that conductive fine particles are precipitated by volatilization of the liquid. When conductive fine particles are deposited in the vicinity of the droplet ejection port in this way, the trajectory of the ejected droplet changes (so-called flight bending occurs), making it impossible to land the droplet on the target site. In some cases, the droplet discharge amount may become unstable.

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.

（ただし、Ｒ、Ｒ’は、それぞれ、Ｈまたはアルキル基である。）
これにより、液滴吐出ヘッドから安定して吐出可能な導体パターン形成用インクを提供することができる。 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,
It contains metal particles, an aqueous dispersion medium in which the metal particles are dispersed, and a compound represented by the following formula (I).

(However, R and R ′ are each H or an alkyl group.)
Thereby, it is possible to provide a conductive pattern forming ink that can be stably discharged from the droplet discharge head.

In the conductive pattern forming ink of the present invention, the content of the compound represented by the formula (I) is preferably 5 to 25 wt%.
Thereby, unintentional drying of the conductor pattern forming ink can be prevented more efficiently. As a result, the ink ejection stability can be made particularly excellent.
The ink for forming a conductor pattern of the present invention preferably further contains alkanolamine.
Thereby, the moisture retention of the conductor pattern forming ink can be made higher, and the volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be further effectively prevented.

In the conductive pattern forming ink of the present invention, the alkanolamine is preferably a tertiary amine.
Thereby, the moisture retention of the conductor pattern forming ink can be made higher, and the volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be further effectively prevented.

The ink for forming a conductor pattern of the present invention preferably further contains a sugar alcohol.
Thereby, it can prevent more reliably that an aqueous dispersion medium volatilizes in the discharge part vicinity of an inkjet apparatus, and the raise of the viscosity of an ink and drying are suppressed. As a result, the ink droplet ejection stability is further improved.
In the conductive pattern forming ink of the present invention, the sugar alcohol content is preferably 3 to 20 wt%.
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 ink for forming a conductor pattern of the present invention, the substrate is formed by degreasing and sintering a sheet-like ceramic formed body made of a material containing ceramic particles and a binder. Yes,
The conductive pattern forming ink is preferably applied onto the ceramic molded body by a droplet discharge method.
The ink for forming a conductor pattern of the present invention can be suitably used for forming a conductor pattern on such a ceramic molded body.

The ink for forming a conductor pattern of the present invention is preferably a colloidal liquid in which metal colloid particles composed of the metal particles and a dispersant attached to the surface of the metal particles are dispersed in the aqueous dispersion medium.
Thereby, aggregation of the metal particles in the ink is prevented, the ejection stability is improved, and a finer conductor pattern can be formed.
In the conductive pattern forming ink of the present invention, the dispersant preferably contains mercapto acid having two or more COOH groups and SH groups or a salt thereof.
Thereby, aggregation of the metal particles in the ink is prevented, the ejection stability is improved, and a finer conductor pattern can be formed.
In the ink for forming a conductor pattern of the present invention, the colloidal liquid preferably has a pH of 6-12.
Thereby, aggregation of the metal particles in the ink is prevented, the ejection stability is improved, and a finer conductor pattern can be formed.

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.

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, 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 substrate, 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 compound represented by the following formula (I).

（ただし、Ｒ、Ｒ’は、それぞれ、Ｈまたはアルキル基である。）

(However, R and R ′ are each H or an alkyl group.)

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 a liquid composed of water and / or a liquid having excellent 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.
In addition, the content of the aqueous dispersion medium in the conductor pattern forming ink is preferably 25 to 60 wt%, and more preferably 30 to 50 wt%. 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 to 100 nm, and more preferably 10 to 30 nm. 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, in the ink, the average interparticle distance of silver particles is preferably 1.7 to 380 nm, and more preferably 1.75 to 300 nm. 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) on which the dispersant is not adsorbed on the surface) contained in the ink is preferably 0.5 to 60 wt%, and 10 to 45 wt%. 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 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 a dispersant 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 about 1 to 60 wt%, and more preferably about 10 to 50 wt%. 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.

The heat loss up to 500 ° C. in the thermogravimetric analysis of the silver colloidal particles is preferably about 1 to 25 wt%. 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 for 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.

[Compound represented by formula (I)]
The conductive pattern forming ink of the present invention contains a compound represented by the following formula (I).

（ただし、Ｒ、Ｒ’は、それぞれ、Ｈまたはアルキル基である。）

(However, R and R ′ are each H or an alkyl group.)

  The compound represented by the above formula (I) is a component having a high hydrogen bonding property. For this reason, it has a high affinity with water, can retain an appropriate amount of water, and can prevent unintentional volatilization of the aqueous dispersion medium of the conductor pattern forming ink. As a result, the aqueous dispersion medium can be prevented from volatilizing in the vicinity of the discharge portion of the ink jet apparatus, and the increase in the viscosity and drying of the ink can be suppressed. As a result, the ejection stability of ink droplets is particularly excellent. That is, variation in the weight of ink droplets is small, and clogging, flight bending, and the like are small. In particular, even when the ink jet device is in a standby state without being operated for a long time (for example, 5 days) after the ink for forming a conductor pattern is filled in the ink jet device, the conductor pattern forming ink of the present invention is used. The ink can be ejected to the target position with a uniform amount and with high accuracy.

Moreover, the said compound is comparatively easy to burn, and when forming a conductor pattern, it can remove (oxidative decomposition) more easily from the inside of a conductor pattern.
Further, when the pattern formed by the conductor pattern forming ink is dried (dedispersion medium), the concentration of the compound increases as the aqueous dispersion medium volatilizes. As a result, the viscosity of the conductor pattern precursor is increased, so that the ink constituting the precursor can be more reliably prevented from flowing to an unintended portion. As a result, the formed conductor pattern can be formed into a desired shape with higher accuracy.

In addition, since the ink for forming a conductor pattern has little volatilization of the aqueous dispersion medium, it has excellent storage stability with little change in physical properties such as viscosity over a long period of time.
In addition, when the metal particles (silver particles) are colloidal particles having a dispersant attached to the surface as described above, the compound as described above is bonded to the surface dispersant by hydrogen bonding, and the dispersion stability of the metal particles. Has the effect of improving. Accordingly, the ejection stability of the conductor pattern forming ink is excellent, and the storage stability is also excellent.

  As described above, R and R ′ in the compound represented by the above formula (I) used in the present invention are each hydrogen or an alkyl group, but R and R ′ are both hydrogen. preferable. That is, urea is preferable. As a result, the moisture retention as described above can be made particularly high, and particularly excellent ejection stability can be obtained. Further, when the metal particles are present as colloidal particles as described above, particularly excellent dispersion stability is exhibited.

  The content of the compound represented by the formula (I) in the ink is preferably 5 to 25 wt%, more preferably 8 to 20 wt%, and 10 to 18 wt%. Further preferred. Thereby, the unintentional drying of the conductor pattern forming ink can be prevented more efficiently. As a result, the ink ejection stability can be made particularly excellent.

[Other ingredients]
The conductive pattern forming ink may contain alkanolamine. Alkanolamine is a highly moisturizing component as in the above formula (I). Therefore, the unintentional drying of the conductor pattern forming ink can be prevented more reliably, and the discharge stability of the conductor pattern forming ink can be further improved. Further, by containing alkanolamine, the amine group of the compound represented by the above formula (I) is activated, and the hydrogen bondability of the compound represented by the above formula (I) can be made higher. . As a result, the moisturizing power of the conductor pattern forming ink can be made higher, and unintentional volatilization of the aqueous dispersion medium of the conductor pattern forming ink can be further effectively prevented.
Further, when the metal particles are colloidal particles as described above, the functional group of the dispersant on the surface of the colloidal particles can be activated, and the dispersion stability of the metal particles can be further increased.

Examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, and tripropanolamine.
The alkanolamine is preferably a tertiary amine. Tertiary amines have particularly high moisture retention among alkanolamines, and can make the above effects more remarkable.

Among tertiary amines, it is particularly preferable to use triethanolamine from the viewpoints of ease of handling, high moisture retention, and the like.
The content of alkanolamine in the conductor pattern forming ink is preferably 1 to 10 wt%, and more preferably 3 to 7 wt%. Thereby, the discharge stability of the conductor pattern forming ink can be made more effective.

  The conductive pattern forming ink 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, when the compound represented by the above formula (I) is contained in the ink, the compound and the organic binder are bonded by a hydrogen bond, and the dispersion stability of the organic binder in the aqueous dispersant is 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.

  As the organic binder, those having a weight average molecular weight of 300 to 3000 are preferable, those having 400 to 1000 are more preferable, and those having 400 to 600 are more preferable. 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 to 30 wt%, and more preferably 5 to 20 wt%. 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.

In addition, the conductor pattern forming ink may contain a sugar alcohol in addition to the above components.
Sugar alcohol is obtained by reducing aldehyde groups and ketone groups of sugars.
The sugar alcohol is a component that can contribute to preventing volatilization of the aqueous dispersion medium of the conductive pattern forming ink, like the compound represented by the formula (I) described above. When the conductive pattern forming ink contains a sugar alcohol, the aqueous dispersion medium is more likely to volatilize in the vicinity of the discharge portion of the ink jet device due to a synergistic effect with the moisturizing effect of the compound represented by formula (I) described above. This can be surely prevented, and increase in ink viscosity and drying can be suppressed. As a result, the ink droplet ejection stability is further improved.
In addition, since sugar alcohol has a large number of oxygen per molecular weight, it is easily decomposed and removed when the atmosphere reaches the decomposition temperature of sugar alcohol. For this reason, when forming a conductor pattern, sugar alcohol can be reliably removed (oxidative decomposition) from the conductor pattern by making the temperature of the conductor pattern higher than the decomposition temperature of the sugar alcohol.

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.
The content of the sugar alcohol as described above in the conductive pattern forming ink is preferably 3 to 20 wt%, more preferably 5 to 15 wt%. 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 to 80 ° (more preferably 50 to 80 °). 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 deviate from the landing position.

  Examples of the acetylene glycol compounds include Surfinol 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 the two or more acetylene glycol compounds contained in the ink is 4 It is preferably -12, and more preferably 5-10. 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 the 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 to 16, more preferably 9 to 14. .
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. More preferred.
The content of the acetylene glycol compound contained in the ink is preferably 0.001 to 1 wt%, and more preferably 0.01 to 0.5 wt%. 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 thereof is preferably 0.5 to 20 wt%, and more preferably 2 to 10 wt%. 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. The conductor pattern forming ink may contain thiourea in addition to the urea described above.

<< 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, mercaptoacetate sodium that 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 the compound represented by the formula (I) and alkanolamine as described above to the aqueous solution in which the silver colloidal particles obtained as described above are dispersed, a conductive pattern forming ink ( The conductive pattern forming ink of the present invention is obtained.
The timing of adding the compound represented by the formula (I) and other components such as alkanolamine is not particularly limited, and may be any time after the formation of silver colloidal particles.

《Conductor pattern》
Next, the conductor pattern of this embodiment will be described.
This conductor pattern is a thin-film-like conductor pattern formed by applying the above ink on a ceramic molded body and then heating, and silver particles are bonded to each other. The particles are bound together without any gaps.
In particular, since the conductor pattern is formed using the conductor pattern forming ink of the present invention, disconnection due to defective discharge or contact between adjacent conductor patterns is prevented, and there is no crack, disconnection, etc. And particularly reliable.

The conductor pattern of the present embodiment is formed by applying the above ink on a ceramic molded body by a droplet discharge method to form a pattern (precursor), drying (dehydrating dispersion medium), and then sintering. It is formed.
As drying conditions, it is preferable to carry out at 40-100 degreeC, for example, and it is more preferable to carry out at 50-70 degreeC. By setting it as such conditions, when it dries, it can prevent more effectively that a crack generate | occur | produces. Moreover, sintering should just heat at 160 degreeC or more for 20 minutes or more. The precursor can be sintered together with degreasing and sintering of the ceramic molded body.

The specific resistance of the conductor pattern 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.
Also, when forming the conductor pattern of this embodiment, ink is applied by a droplet discharge method and then preheated to evaporate the dispersion medium such as water, and the ink is again applied on the preheated film. By repeating the step of applying, a thick-film conductor pattern can be formed.

In the ink after evaporating the dispersion medium such as water, the compound represented by the formula (I) and the silver colloid particles remain as described above, so that the formed pattern is not completely dried. But there is no risk of the pattern being washed away. Therefore, it is possible to apply the ink once, dry it, leave it for a long time, and then apply the ink again.
In addition, since the organic binder (especially polyglycerin compound) as described above is a chemically and physically stable compound, the ink may be deteriorated even if it is left for a long time after being applied and dried. The ink can be applied again and a uniform pattern can be formed. Thereby, there is no possibility that the conductor pattern itself has a multilayer structure, and there is no possibility that the specific resistance between the layers increases and the specific resistance of the entire conductor pattern increases.

  By passing through the above steps, the conductor pattern of the present embodiment can be formed thicker than a conductor pattern formed by a conventional ink. More specifically, a film having a thickness of 5 μm or more can be formed. Since the conductor pattern of this embodiment is formed by the above ink, even if it is formed in a thick film of 5 μm or more, the occurrence of cracks is small, and a conductor pattern having a low specific resistance can be configured. The upper limit of the thickness is not particularly required, but if it is excessively thick, it may be difficult to remove the aqueous dispersion medium or the organic binder and the specific resistance may increase. .

Furthermore, the conductor pattern of this embodiment has good adhesion to the substrate as described above.
Note that the conductor pattern as described above is a variant of a high-frequency module, interposer, MEMS (Micro Electro Mechanical Systems), acceleration sensor, surface acoustic wave element, antenna, comb electrode, etc. of a mobile phone such as a mobile phone or PDA. It can be applied to electrodes and other electronic parts such as various measuring devices.

<< Wiring board and manufacturing method thereof >>
Next, an example of a wiring board (ceramic circuit board) having a conductor pattern formed by the conductor pattern forming ink of the present invention and a method for manufacturing the same will be described.
The wiring board according to the present invention is an electronic component used in various electronic devices. A circuit pattern composed of various wirings, electrodes, etc., a multilayer ceramic capacitor, a multilayer inductor, an LC filter, a composite high-frequency component, etc. are formed on the substrate. It is made.

  FIG. 1 is a longitudinal sectional view showing an example of a wiring board (ceramic circuit board) according to the present invention. FIG. 2 is an explanatory view showing a schematic process of the method for manufacturing the wiring board (ceramic circuit board) shown in 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 device (droplet discharge device), and FIG. 5 is an ink jet head (droplet). It is a schematic diagram for demonstrating schematic structure of a discharge head.

As shown in FIG. 1, a ceramic circuit board (wiring board) 1 includes a laminated board 3 in which a large number (for example, about 10 to 20) of ceramic boards 2 are laminated, and an outermost layer of the laminated board 3, that is, one of them. And a circuit 4 made of fine wiring or the like formed on the surface on the other side.
The laminated substrate 3 includes a circuit (conductor pattern) 5 formed between the laminated ceramic substrates 2 and 2 using the conductor pattern forming ink of the present invention (hereinafter simply referred to as ink).
In addition, these circuits 5 have contacts (vias) 6 connected thereto. With this configuration, the circuit 5 is electrically connected by the contact 6 between the circuits 5 and 5 arranged above and below. The circuit 4 is also formed by the conductor pattern forming ink of the present invention, like the circuit 5.

Next, the manufacturing method of the ceramic circuit board 1 is demonstrated with reference to the schematic process drawing of FIG.
First, as a raw material powder, ceramic powder made of alumina (Al ₂ O ₃ ), titanium oxide (TiO ₂ ) or the like having an average particle diameter of about 1 to 2 μm, borosilicate glass having an average particle diameter of about 1 to 2 μm, etc. Are prepared and 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 obtained 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 to several hundred μm depending on the production conditions of the product. Take up 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 is formed at a predetermined position by drilling with a CO ₂ laser, a YAG laser, a mechanical punch or the like as required.
Then, by filling the through hole with a thick film conductive paste in which metal particles are dispersed, a portion to be the contact 6 is formed. Further, a terminal portion (not shown) is formed at a predetermined position by screen printing of the thick film conductive paste. Thus, the ceramic green sheet (ceramic molded body) 7 is obtained by forming the contact and the terminal part. As the thick film conductive paste, the conductor pattern forming ink of the present invention can be used.

  On the surface of one side of the ceramic green sheet 7 obtained as described above, the precursor of the circuit 5 which becomes the conductor pattern in the present invention is formed in a state continuous with the contact. That is, as shown in FIG. 3A, a conductive pattern forming ink (hereinafter also simply referred to as ink) 10 as described above is applied onto the ceramic green sheet 7 by a droplet discharge (inkjet) method, and the circuit 5 A precursor 11 is formed.

In this embodiment, the conductive pattern forming ink is discharged by using, for example, an ink jet device (droplet discharge device) 50 shown in FIG. 4 and an ink jet head (droplet discharge head) 70 shown in FIG. Can do. Hereinafter, the inkjet device 50 and the inkjet head 70 will be described.
FIG. 4 is a perspective view of the inkjet device 50. In FIG. 4, the X direction is the left-right direction of the base 52, the Y direction is the front-rear direction, and the Z direction is the up-down direction.

The ink jet device 50 includes an ink jet head (hereinafter simply referred to as a head) 70 and a table 46 on which a substrate S (ceramic green sheet 7 in the present embodiment) is placed. The operation of the ink jet device 50 is controlled by the control device 53.
The table 46 on which the substrate S is placed can be moved and positioned in the Y direction by the first moving means 54, and can be swung and positioned in the θz direction by the motor 44.

On the other hand, the head 70 can be moved and positioned in the X direction by a second moving means (not shown), and can be moved and positioned in the Z direction by a linear motor 62. The head 70 can be swung and positioned in the α, β, and γ directions by motors 64, 66, and 68, respectively. Based on such a configuration, the ink jet apparatus 50 can accurately control the relative position and orientation of the ink ejection surface 70P of the head 70 and the base material S on the table 46.
A rubber heater (not shown) is disposed on the back surface of the table 46. The entire upper surface of the ceramic green sheet 7 placed on the table 46 is heated to a predetermined temperature by a rubber heater.

At least a part of the aqueous dispersion medium evaporates from the surface side of the ink 10 that has landed on the ceramic green sheet 7. At this time, since the ceramic green sheet 7 is heated, evaporation of the aqueous dispersion medium is promoted. The ink 10 that has landed on the ceramic green sheet 7 thickens from the outer edge of the surface as it dries. That is, the solid content (particle) concentration in the outer peripheral portion is faster than the central portion and reaches the saturation concentration. Thicken from the outer edge. The thickened ink 10 at the outer edge stops its own wetting and spreading along the surface direction of the ceramic green sheet 7, so that the line width can be easily controlled with respect to the landing diameter.
This heating temperature is the same as the drying conditions described above.

As shown in FIG. 5, the head 70 ejects the ink 10 from a nozzle (projecting portion) 91 by an inkjet method (droplet ejection method).
Various known technologies such as a piezo method in which ink is ejected using a piezoelectric element as a piezoelectric element, and a method in which ink is ejected by bubbles generated by heating the ink are applied as a droplet ejection method. can do. Of these, the piezo method has the advantage that it does not affect the composition of the material because it does not apply heat to the ink. Therefore, the above-described piezo method is adopted for the head 70 shown in FIG.

A head body 90 of the head 70 is formed with a reservoir 95 and a plurality of ink chambers 93 branched from the reservoir 95. The reservoir 95 is a flow path for supplying the ink 10 to each ink chamber 93.
A nozzle plate (not shown) that constitutes an ink ejection surface is attached to the lower end surface of the head main body 90. In this nozzle plate, a plurality of nozzles 91 for discharging the ink 10 are opened corresponding to the respective ink chambers 93. An ink flow path is formed from each ink chamber 93 toward the corresponding nozzle 91. On the other hand, a diaphragm 94 is attached to the upper end surface of the head main body 90. The diaphragm 94 constitutes a wall surface of each ink chamber 93. Piezo elements 92 are provided outside the diaphragm 94 so as to correspond to the ink chambers 93. The piezo element 92 is obtained by holding a piezoelectric material such as crystal between a pair of electrodes (not shown). The pair of electrodes is connected to the drive circuit 99.

  When an electric signal is input from the drive circuit 99 to the piezo element 92, the piezo element 92 is expanded or contracted. When the piezo element 92 contracts and deforms, the pressure in the ink chamber 93 decreases, and the ink 10 flows from the reservoir 95 into the ink chamber 93. Further, when the piezo element 92 expands and deforms, the pressure in the ink chamber 93 increases and the ink 10 is ejected from the nozzle 91. Note that the amount of deformation of the piezo element 92 can be controlled by changing the applied voltage. Further, the deformation speed of the piezo element 92 can be controlled by changing the frequency of the applied voltage. That is, by controlling the voltage applied to the piezo element 92, the ejection conditions of the ink 10 can be controlled.

Therefore, by using the ink jet apparatus 50 including such a head 70, the ink 10 can be discharged and arranged with a desired amount and accuracy in a desired place on the ceramic green sheet 7. Furthermore, since the ink 10 is the conductor pattern forming ink of the present invention, drying of the ink 10 in the head 70 is suppressed, and precipitation of metal particles is prevented. Therefore, as shown in FIG. 3A, the precursor 11 can be formed accurately and easily.
After the precursor 11 is formed in this way, the required number of ceramic green sheets 7 on which the precursor 11 is formed, for example, about 10 to 20 are produced by the same process.

  Next, the PET film is peeled off from these ceramic green sheets, and these are laminated as shown in FIG. At this time, the ceramic green sheets 7 to be laminated are arranged so that the precursors 11 are connected via the contacts 6 as necessary between the ceramic green sheets 7 stacked one above the other. Thereafter, the ceramic green sheets 7 are pressed against each other while being heated to a glass transition point or higher of the binder constituting the ceramic green sheets 7. Thereby, the laminated body 12 is obtained.

  After the laminated body 12 is formed in this way, for example, heat treatment is performed by a belt furnace or the like. As a result, each ceramic green sheet 7 is sintered to form a ceramic substrate 2 (wiring substrate of the present invention) as shown in FIG. 3B, and the precursor 11 is a silver colloid constituting the ceramic substrate 2. The particles are sintered to form a circuit (conductor pattern) 5 including a wiring pattern or an electrode pattern. And the laminated body 12 becomes the laminated substrate 3 shown in FIG. 1 by heat-processing the laminated body 12 in this way.

  Here, the heating temperature of the laminated body 12 is preferably not less than the softening point of the glass contained in the ceramic green sheet 7, 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 obtained ceramic substrate 2 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 2 constituting the laminated substrate 3 and the circuit (conductor pattern) 5 are more firmly fixed.
Moreover, by heating in such a temperature range, the obtained ceramic substrate 2 becomes low-temperature sintered ceramics (LTCC) formed by sintering at a temperature of 900 ° C. or less.

Here, the metals in the ink 10 disposed on the ceramic green sheet 7 are fused to each other by heat treatment and become conductive by being continuous.
By such heat treatment, the circuit 5 is directly connected to the contact 6 in the ceramic substrate 2 and is made conductive. Here, if the circuit 5 is merely placed on the ceramic substrate 2, the mechanical connection strength to the ceramic substrate 2 is not ensured, and therefore there is a possibility that the circuit 5 may be damaged by an impact or the like. However, in the present embodiment, as described above, the circuit 5 is firmly fixed to the ceramic substrate 2 by once softening the glass in the ceramic green sheet 7 and then curing it. Therefore, the formed circuit 5 has a high mechanical strength.
Note that, by such heat treatment, the circuit 4 can be formed simultaneously with the circuit 5, whereby the ceramic circuit board 1 can be obtained.

  In such a method of manufacturing the ceramic circuit board 1, the ink 10 (the ink for forming a conductor pattern of the present invention) as described above is applied to the ceramic green sheet particularly when the ceramic substrates 2 constituting the multilayer substrate 3 are manufactured. Since the conductor pattern forming ink 10 can be satisfactorily arranged in a desired pattern on the ceramic green sheet 7, a highly accurate conductor pattern (circuit) 5 is formed. be able to.

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. . Moreover, the ink for forming a conductor pattern 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 Ink for Conductive Pattern Formation Ink for forming a conductive pattern in each example and each comparative example was manufactured as follows.

(Examples 1-12)
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.

In this silver colloidal solution, urea, triethanolamine, sugar alcohol shown in Table 1, polyglycerin, Surfynol 104PG-50 (manufactured by Nissin Chemical Industry Co., Ltd.) and Olphine EXP4036 (Nisshin Chemical Co., Ltd.) Shinko Chemical Co., Ltd.) was added, and ion-exchanged water for concentration adjustment was further added for adjustment to obtain a conductor pattern forming ink.
The content of each constituent material of the conductor pattern forming ink is shown in Table 1.

(Comparative Example 1)
A conductor pattern forming ink was produced in the same manner as in Example 1 except that urea was not added and the blending amounts of the other components were changed as shown in Table 1.
(Comparative Example 2)
A conductor pattern forming ink was produced in the same manner as in Example 1 except that thiourea was added instead of urea and the blending amounts of the other components were changed as shown in Table 1.
Table 1 shows the compositions of the conductive pattern forming inks of the examples and comparative examples. In the table, xylitol was indicated as KI and sorbitol as SB.

[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] Evaluation of storage stability The ink for forming a conductor pattern obtained in each Example and each Comparative Example was dropped on a glass substrate immediately after the production, in an atmosphere of temperature: 25 ° C. and humidity: 50%. I left it alone. After leaving, a glass rod was inserted into the dropped conductor pattern forming ink, and it was confirmed whether or not the conductor pattern forming ink was in a liquid state. The number of days from when the ink was left until the liquid could not be maintained was evaluated as the liquid retention period of each conductor pattern forming ink according to the following four criteria.
A: Liquid retention period is 30 days or more.
B: Liquid retention period is 7 days or more and less than 30 days.
C: The liquid retention period is 3 days or more and less than 7 days.
D: Liquid retention period is less than 3 days.

[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 25 ° C., a relative humidity of 50%, and a class 100 with the ink jet head removed from the drawing position. Next, the inkjet apparatus was turned on, and a solid pattern was drawn on the 20 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 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 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 seconds, 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).
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.

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.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ceramics circuit board (wiring board) 2 ... Ceramics board 3 ... Laminated board 4, 5 ... Circuit (conductor pattern) 6 ... Contact 7 ... Ceramic green sheet 10 ... Ink (ink) for conductor pattern formation 11 ... Precursor 12 ... Laminated body 44 ... motor 46 ... table 50 ... inkjet device (droplet ejection device) 52 ... base 53 ... control device 54 ... first moving means 62 ... linear motors 64, 66, 68 ... motor 70 ... inkjet head (droplet ejection) 70P: Ink ejection surface 90 ... Head body 91 ... Nozzle (protrusion) 92 ... Piezo element 93 ... Ink chamber 94 ... Vibration plate 95 ... Reservoir 99 ... Drive circuit S ... Base material

Claims (12)

Conductor pattern forming ink for forming a conductor pattern on a substrate by a droplet discharge method,
A conductive pattern forming ink comprising metal particles, an aqueous dispersion medium in which the metal particles are dispersed, and a compound represented by the following formula (I).

(However, R and R ′ are each H or an alkyl group.)   2. The conductive pattern forming ink according to claim 1, wherein the content of the compound represented by the formula (I) is 5 to 25 wt%.   The ink for forming a conductor pattern according to claim 1, further comprising an alkanolamine.   4. The conductive pattern forming ink according to claim 1, wherein the alkanolamine is a tertiary amine.   The ink for forming a conductor pattern according to claim 1, further comprising a sugar alcohol.   The conductive pattern forming ink according to claim 5, wherein a content of the sugar alcohol is 3 to 20 wt%. The base material is formed by degreasing and sintering a sheet-like ceramic molded body made of a material containing ceramic particles and a binder,
7. The conductive pattern forming ink according to claim 1, wherein the conductive pattern forming ink is applied onto the ceramic molded body by a droplet discharge method.   The ink for forming a conductor pattern is a colloid liquid in which metal colloid 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.   The conductor pattern forming ink according to claim 8, wherein the dispersant contains mercapto acid having two or more COOH groups and SH groups or a salt thereof.   The ink for forming a conductor pattern according to claim 8 or 9, wherein the colloidal liquid has a pH of 6 to 12.   A conductor pattern formed with the conductor pattern forming ink according to claim 1.   A wiring board comprising the conductor pattern according to claim 11.

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