JP2005057140A - Multilayer wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer wiring board manufacturing method which is capable of manufacturing a multilayer wiring board at a low cost in a shorter time by a droplet discharge system preventing an unnecessary part from being conductive. <P>SOLUTION: The method of manufacturing the multilayer wiring board comprises processes of subjecting the surface of an unburned ceramic board 1 to liquid-repellent treatment, applying a liquid material 22 containing a conductive film forming component by a droplet discharge system on the unburned ceramic board 1 which has been liquid-repellent, stacking up the unburned ceramic boards 1 where the liquid material 22 is applied, and forming a conductive film pattern with the conductive film forming component by thermally treating the stacked unburned ceramic boards 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multilayer wiring board and a method for manufacturing the same.

  As a multilayer wiring board, for example, a low-temperature sintered ceramic multilayer wiring board, a method of screen printing or the like on an unfired ceramic substrate formed by adding a binder and a solvent to a mixture of alumina powder and silica powder, a so-called green sheet After forming a pattern with a metal paste using, and then forming via holes for filling up and down and filling with metal paste, the green sheets (multiple sheets) are aligned and then laminated and crimped And it is manufactured by the manufacturing method which passes through a binder removal and a sintering process.

However, screen printing using a metal paste has a problem that the minimum line width that can be formed is about 50 μm and a printing mask that takes time to create is required, so that it cannot respond quickly to pattern changes. is there.
Therefore, Patent Document 1 discloses a technique that can reduce the cost and shorten the time by using an inkjet method (droplet discharge method) for such a screen printing process.
That is, in Patent Document 1, an unfired green sheet is used as a substrate, and a circuit pattern is drawn using an ink in which a powder such as a metal or a resistor is dispersed in an organic dispersion medium that is easily absorbed by the green sheet. Thereafter, the electronic circuit is baked to realize an electronic circuit that solves the problem that the ink easily flows and wets easily on the substrate.
In recent years, inks used in the ink jet method include metal nanoparticles, and Patent Document 2 discloses this kind of ink.
Japanese Patent Laid-Open No. 58-50795 JP 2002-164635 A

However, the following problems exist in the conventional technology as described above.
When a metal ink is directly applied to a green sheet by an ink jet method, not only the organic dispersion medium in the ink but also metal fine particles are absorbed and penetrated into the green sheet and may reach the back side of the sheet in some cases. . This is because the viscosity of the ink is low and the size of the metal fine particles contained in the ink is considerably smaller than the average pore size of the green sheet. When sintering is performed in such a state, the top and bottom layers of the green sheet are conducted at unintended locations, and the upper and lower layers are conducted at unnecessary portions when the green sheets are stacked. There is a risk that it will not function as a substrate. If it is a paste for screen printing, such a situation will not be caused, but it is difficult to apply ink by an ink jet method because of its high viscosity and large particle diameter, which means that the above-mentioned cost reduction and time reduction are mentioned. The effect cannot be obtained.

  The present invention has been made in consideration of the above points, and a multilayer wiring board capable of reducing the cost and shortening the time by a droplet discharge method while preventing conduction in unnecessary portions, and its An object is to provide a manufacturing method.

In order to achieve the above object, the present invention employs the following configuration.
The method for producing a multilayer wiring board according to the present invention comprises a step of applying a liquid repellency treatment to the surface of an unfired ceramic substrate, and a liquid material containing a conductive film forming component on the liquid-repellent unfired ceramic substrate by a droplet discharge method. A step of applying, a step of laminating a plurality of the unfired ceramic substrates coated with the liquid, a step of heat-treating the laminated unfired ceramic substrates to form a conductive film pattern with the conductive film forming component, It is characterized by having.
Therefore, in the present invention, when the multilayer wiring board is manufactured, the liquid material is applied by the droplet discharge method, so that the cost and the time can be reduced. In addition, when a liquid material containing a conductive film forming component such as conductive fine particles is applied to the surface of an unfired ceramic substrate that has been subjected to lyophobic treatment, that is, a so-called green sheet, a conductive film contained in the liquid material Forming components, solvents and the like do not penetrate deeply into the green sheet and stay on the surface (near the surface), so that unnecessary conduction between the upper and lower layers of the substrate can be prevented.

In the present invention, when the liquid material is applied to the unfired ceramic substrate by a droplet discharge method, the unfired ceramic substrate depends on the contact angle of the unfired ceramic substrate subjected to the liquid repellent treatment to the liquid material. It is also possible to adopt a configuration in which a plurality of liquid droplet application patterns are selected.
As one of the coating patterns, the distance between the centers of the liquid droplets adjacent to each other on the green ceramic substrate is the radius of the liquid droplets when landing on the green ceramic substrate, More than the sum of the radius of the ink jet droplets before landing on the unfired ceramic substrate and smaller than twice the radius of the droplets when landing on the unfired ceramic substrate. It is preferable to have a pattern for discharging a liquid material.
According to this, the liquid droplets are not directly applied to the droplets already applied on the unfired ceramic substrate, but are connected to the droplets already applied on the substrate by the spread of the droplets after landing on the substrate. By discharging in this manner, it is possible to prevent the line from becoming irregular due to the impact generated when the liquid droplet directly hits the liquid droplet already applied on the substrate, thereby preventing problems such as disconnection. Further, by discharging at a discharge interval smaller than twice the radius of the droplet on the substrate, it is possible to prevent the lines from being formed because the droplets are not connected to each other.

Further, as one of the coating patterns, it is preferable to have a pattern for discharging the liquid material so as to cause an overlap of 1% to 10% of the diameter of the liquid material when landed on the unfired ceramic substrate. .
According to this, by setting it to 10% or less, it is possible to prevent the amount of liquid applied per unit length of the line from becoming excessive, and a liquid pool generated by concentrating liquid on a certain part of the line. It is possible to prevent the occurrence of bulges that can cause disconnection of wires and short circuits with other lines. Further, by setting the ratio to 1% or more, it is possible to prevent the droplets from overlapping each other due to the ejection position accuracy error, and to avoid the disconnection of the line.

The coating pattern is preferably applied when the contact angle is 30 ° or more and 60 ° or less.
This is because if the contact angle is smaller than 30 °, the droplets are too spread and spread on the substrate, so that a functional film pattern having a disordered shape is formed. If the contact angle is larger than 60 °, the ejected droplets are transferred to the substrate. This is because when the liquid droplets land on the substrate and come into contact with a droplet already on the substrate, the droplet is taken into the droplet, which may cause problems such as disconnection in the functional film pattern.

Further, as one of the coating patterns, a first discharge step of discharging the liquid material at a pitch larger than the diameter of the droplet after landing on the unfired ceramic substrate, and a discharge position in the first discharge step And a second discharge step of discharging the liquid material at a pitch larger than the diameter of the droplets after landing on the unfired ceramic substrate.
Here, “the diameter of the droplet after landing on the substrate” means the maximum diameter during which the discharged droplet naturally spreads after landing on the substrate and then shrinks with drying. That is, by “discharging at a pitch larger than the diameter of the droplet after landing on the substrate”, the droplets to be continuously discharged do not come into contact with each other even after they naturally spread after landing. It means to discharge.
In addition, “different positions” means that the center positions of the droplets are different, and the droplets ejected by the first step and the droplets ejected by the second step partially overlap each other, Or it does not overlap completely.

According to the present invention, in both the first discharge process and the second discharge process, the droplets and the droplets are discharged separately from each other to the film formation region on the substrate. Therefore, the droplets do not coalesce with each other to generate a bulge.
In addition, since the discharge positions are different between the first discharge process and the second discharge process, the gap between the droplets in the first discharge process can be filled by the second discharge process.
It should be noted that the liquid droplets ejected in the second ejection process may partially overlap the liquid droplets ejected in the first ejection process. That is, since the liquid droplets discharged in the first discharge process have been dried to some extent or completely, there is a risk that the liquid droplets in both processes merge with each other to form a bulge in the same process. It is because it becomes low compared with the case where a droplet is discharged continuously.
According to the present invention, since the risk of bulging is reduced, the liquid repellency of the substrate can be improved and the contact angle between the substrate and the liquid can be increased. For this reason, it is possible to reduce the thickness and the film thickness.
Further, since the droplet discharge method is used, a film can be formed even when the substrate is not flat but uneven. Therefore, for example, a film such as a wiring can be formed across a stepped portion.

In the present invention, it is preferable that the pitch in the second discharge step is substantially the same as the pitch in the first discharge step. Thereby, a process can be simplified and work efficiency can be improved.
However, it is not an absolute requirement that the pitch in the second discharge step be substantially the same as the pitch in the first discharge step. For example, the pitch in the second discharge process can be made approximately twice the pitch in the first discharge process or can be halved.

In the present invention, it is preferable that the pitch in the first discharge step is not more than twice the diameter of the droplet after landing on the substrate. In this case, since a continuous linear film pattern can be formed only by the first discharge process and the second discharge process, the process can be simplified and the working efficiency can be improved.
When the pitch in the first discharge step exceeds twice the diameter of the droplet after landing on the substrate, another discharge step is further performed once or more after the second discharge step. Thus, a continuous linear film pattern can be formed.

  In the present invention, it is preferable that the pitch in the first discharge step is 10 μm or more larger than the diameter of the droplet after landing on the substrate. Thereby, even if the error of the landing position of the liquid droplet is taken into consideration, it is possible to surely perform the discharge so that the liquid droplets to be continuously discharged are not separated from and in contact with each other.

In the present invention, it is preferable that after the second discharge step, there is a third discharge step of discharging a plurality of liquid droplets at a pitch smaller than the pitch in the first discharge step.
A portion where the droplets discharged in the first discharge step and the second discharge step are completely or partially dried is given lyophilicity, and the liquid discharged in the third discharge step is easily adapted. Therefore, according to the present invention, it is easy to keep the droplets discharged in the third discharge step in the film formation region. Accordingly, the pitch in the third discharge step can be discharged at a pitch smaller than the pitch in the first discharge step, and the film thickness can be increased efficiently.
In particular, it is preferable that the pitch in the third discharge step is equal to or less than the diameter of the droplet after landing on the substrate. That is, it is preferable that the droplets in the third ejection step have a pitch that contacts each other after landing. This makes it possible to efficiently increase the thickness.

The coating pattern including the first and second ejection steps is preferably applied when the contact angle is 30 ° or more, and can be suitably selected when the special contact angle is 60 ° or more.
When the liquid repellency of the substrate is 60 ° or less, the liquid material in which the conductive fine particles are dispersed is not sufficiently effective to prevent the liquid from spreading after landing on the substrate, and 60 ° or more is necessary for thickening and thinning. preferable. Also, when the liquid material is overcoated after drying, if the liquid repellency of the substrate is 60 ° or less, the difference in water repellency from the portion where the liquid is dried to become lyophilic is not sufficient. If the amount of the liquid applied is too large, the liquid material does not stay in the dry part first, and the liquid material tends to flow down on the substrate, resulting in a problem that the line width becomes thick. If so, these problems can be solved.

By providing the green ceramic substrate with a step of forming a conductor post for conducting the conductive pattern between a plurality of layers, the wiring formed in each layer can be made conductive.
When the conductor post is formed by a droplet discharge method, photolithography, etching, and a punching process are not necessary for forming the conductor post, and thus the manufacturing process of the multilayer wiring board can be simplified. Thus, the manufacturing apparatus can be downsized, the manufacturing period can be shortened, and the manufacturing cost can be reduced.
Further, according to such a method, a mask is not necessary for forming the conductor post, and therefore, for example, the conductor post can be formed directly from CAD data, and the period from design to completion is shortened. It becomes possible to easily cope with design changes.

The multilayer wiring board of the present invention is characterized by having a conductive film pattern formed by the above-described method for manufacturing a multilayer wiring board as wiring.
Accordingly, in the present invention, it is possible to manufacture a conductive pattern in which unnecessary conduction between the upper and lower layers of the substrate is prevented at a low cost and in a short time.

Embodiments of a multilayer wiring board and a method for manufacturing the same according to the present invention will be described below with reference to FIGS.
(First embodiment)
First, a method for manufacturing a multilayer wiring board according to the present invention will be described.
In this manufacturing method, a step of forming a porous substrate, a surface treatment step of making the surface of the substrate lyophobic, and a liquid material containing a conductive film forming component are applied to the surface of the substrate by a droplet discharge method. A step of providing a through hole in a predetermined position of the substrate and filling a metal material, a step of laminating a plurality of substrates, a liquid material on the substrate is heat-treated to bring a conductive film forming component into contact with each other, And a step of forming a conductive film pattern made of a conductive film forming component.

(Porous substrate forming process)
In the porous substrate forming step, a porous unfired ceramic substrate, a so-called green sheet is formed. In this process, borosilicate glass powder, alumina and forsterite powder as raw materials are mixed in predetermined amounts (for example, borosilicate glass; 40 wt%, alumina; 35 wt% and forsterite; 25 wt%), and this is mixed with solvent and organic binder plastic. An agent is added to form a slurry, and a green sheet having a thickness of 100 μm is formed on the base plate by a doctor blade method.

In addition to forsterite, enstatite (MgO.SiO ₂ ), spinel (MgO.Al ₂ O ₃ ), silica (SiO ₂ ), cordierite (2MgO.2Al) are added to the glass-alumina component system. ₂ O ₃ · 5SiO ₂ ), magnesia (MgO), etc. can be used, but forsterite is preferable from the viewpoint of improving the sinterability, and the addition amount is 25 wt% to increase the relative density. It is preferable from the point.
Further, as the green sheet, in addition to the above glass ceramic system, a composite system of crystallized glass and alumina or other ceramics, a ceramic single phase system, an additive system to alumina, or the like may be used.

(Surface treatment process)
In the surface treatment step, the surface of the green sheet on which the conductive film wiring is to be formed has a predetermined contact angle with respect to the liquid containing conductive fine particles of 30 ° [deg] or more, preferably 60 °, more preferably 90 ° or more. A surface treatment (liquid repellency treatment) is performed so as to be 110 ° or less to form a liquid repellency film 2 on the green sheet 1.
Thus, in order to control the liquid repellency (wetting property) of the surface, various surface treatment methods described below can be employed.

As one of the surface treatment methods, there is a method of forming a self-assembled film made of an organic molecular film or the like on the surface of a green sheet on which conductive film wiring is to be formed.
The organic molecular film for treating the surface of the green sheet modifies the surface properties of the green sheet such as a functional group capable of binding to the green sheet and a lyophilic group or a liquid repellent group on the opposite side (controls the surface energy). ) It has a functional group and a linear or partially branched carbon chain connecting these functional groups, and is bonded to a green sheet to self-assemble to form a molecular film, for example, a monomolecular film.

  The self-assembled film is composed of a binding functional group capable of reacting with constituent atoms such as a green sheet such as a green sheet and other linear molecules, and a compound having extremely high orientation by the interaction of the linear molecules, It is a film formed by orientation. Since this self-assembled film is formed by orienting single molecules, the film thickness can be extremely reduced, and the film is uniform at the molecular level. That is, since the same molecule is located on the surface of the film, uniform and excellent liquid repellency and lyophilicity can be imparted to the surface of the film.

For example, when fluoroalkylsilane is used as the compound having high orientation, each compound is oriented so that the fluoroalkyl group is located on the surface of the film, and a self-assembled film is formed. Uniform liquid repellency is imparted to the surface.
Examples of the compound that forms such a self-assembled film include heptadecafluoro-1,1,2,2 tetrahydrodecyltriethoxysilane, heptadecafluoro-1,1,2,2 tetrahydrodecyltrimethoxysilane, heptadeca Fluoro-1,1,2,2 tetrahydrodecyltrichlorosilane, tridecafluoro-1,1,2,2 tetrahydrooctyltriethoxysilane, tridecafluoro-1,1,2,2 tetrahydrooctyltrimethoxysilane, trideca Fluoroalkylsilanes (hereinafter referred to as “FAS”) such as fluoro-1,1,2,2 tetrahydrooctyltrichlorosilane, trifluoropropyltrimethoxysilane, and the like. In use, it is preferable to use one compound alone, but the use of a combination of two or more compounds is not limited as long as the intended purpose of the present invention is not impaired. In the present invention, it is preferable to use the FAS as a compound for forming the self-assembled film in order to provide adhesion to a green sheet and good liquid repellency.

FAS is generally represented by the structural formula RnSiX (4-n). Here, n represents an integer of 1 to 3, and X is a hydrolyzable group such as a methoxy group, an ethoxy group, or a halogen atom. R is a fluoroalkyl group, and has a structure of (CF ₃ ) (CF ₂ ) x (CH ₂ ) y (where x represents an integer of 0 to 10 and y represents an integer of 0 to 4). In the case where a plurality of R or X are bonded to Si, R or X may all be the same or different. The hydrolyzable group represented by X forms silanol by hydrolysis, reacts with the hydroxyl group of the base such as the substrate (glass, silicon), etc., and bonds to the substrate with a siloxane bond. On the other hand, since R has a fluoro group such as (CF ₃ ) on the surface, the base surface such as a green sheet is modified to a surface that does not get wet (surface energy is low).

A self-assembled film composed of an organic molecular film or the like is formed on a green sheet when the above raw material compound and the green sheet are placed in the same sealed container and left at room temperature for about 2 to 3 days. The Further, by holding the entire sealed container at 100 ° C., it is formed on the green sheet in about 3 hours. What has been described above is the formation method from the gas phase, but the self-assembled film can also be formed from the liquid phase. For example, a self-assembled film can be obtained on a green sheet by immersing the green sheet in a solution containing a raw material compound, washing and drying.
In addition, before forming the self-assembled film, it is desirable to perform pretreatment by irradiating the green sheet surface with ultraviolet light or washing with a solvent.

As another method of the surface treatment, there is a method of plasma irradiation in normal pressure or vacuum. Various types of gas used for the plasma treatment can be selected in consideration of the surface material of the substrate on which the conductive film wiring is to be formed.
For example, tetrafluoromethane, perfluorohexane, perfluorodecane, etc. can be used as the processing gas.

The surface treatment can also be performed by attaching a film having a desired liquid repellency, such as a polyimide film processed with tetrafluoroethylene, to the substrate surface. In addition, you may use a polyimide film as a board | substrate as it is.
In addition, when the substrate surface has a liquid repellency higher than the desired liquid repellency, examples of a method for making it lyophilic include a method of irradiating ultraviolet light of 170 to 400 nm and a method of exposing the substrate to an ozone atmosphere. .

(Droplet discharge process)
Next, as shown in FIG. 1B, a liquid containing a conductive film forming component is provided at a predetermined position on the liquid repellent film 2 of the green sheet 1 by a droplet discharge method.
As the liquid containing the conductive film forming component, a dispersion liquid in which conductive fine particles are dispersed in a dispersion medium is used. The conductive fine particles used here include fine particles of conductive polymer or superconductor in addition to metal fine particles containing any of gold, silver, copper, palladium, and nickel.
About these electroconductive fine particles, in order to improve dispersibility, the organic substance etc. can also be coated and used for the surface. Examples of the coating agent that coats the surface of the conductive fine particles include organic solvents such as xylene and toluene, citric acid, and the like.
The particle diameter of the conductive fine particles is preferably 1 nm or more and 0.1 μm or less. This is because if it is larger than 0.1 μm, clogging of the nozzles of the head of the droplet discharge device described later is likely to occur, and it becomes difficult to discharge by the droplet discharge method. On the other hand, if the thickness is smaller than 1 nm, the volume ratio of the coating agent to the conductive fine particles becomes large, and the ratio of the organic matter in the obtained film becomes excessive.

The liquid dispersion medium containing conductive fine particles preferably has a vapor pressure at room temperature of 0.001 mmHg to 200 mmHg (about 0.133 Pa to 26600 Pa). This is because if the vapor pressure is higher than 200 mmHg, the dispersion medium rapidly evaporates after discharge, making it difficult to form a good film.
The vapor pressure of the dispersion medium is more preferably 0.001 mmHg or more and 50 mmHg or less (about 0.133 Pa or more and 6650 Pa or less). This is because if the vapor pressure is higher than 50 mmHg, nozzle clogging due to drying tends to occur when droplets are ejected by the droplet ejection method, and stable ejection becomes difficult.
On the other hand, in the case of a dispersion medium whose vapor pressure at room temperature is lower than 0.001 mmHg, drying is slow and the dispersion medium tends to remain in the film, and a high-quality conductive film after heat and / or light treatment in the subsequent process. Is difficult to obtain.

  The dispersion medium to be used is not particularly limited as long as it can disperse the conductive fine particles and does not cause aggregation. Specific examples of such a dispersion medium include water, alcohols such as methanol, ethanol, propanol, and butanol, n-heptane, n-octane, decane, toluene, xylene, cymene, durene, indene, and dipentene. Hydrocarbon compounds such as tetrahydronaphthalene, decahydronaphthalene, cyclohexylbenzene, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxy Ether compounds such as ethane, bis (2-methoxyethyl) ether, p-dioxane, propylene carbonate, γ Butyrolactone, N- methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, may be mentioned polar compounds such as cyclohexanone. Of these, water, alcohols, hydrocarbon compounds, and ether compounds are preferable, and more preferable dispersion is preferable from the viewpoints of fine particle dispersibility, dispersion stability, and ease of application to the droplet discharge method. Examples of the medium include water and hydrocarbon compounds. These dispersion media can be used alone or as a mixture of two or more.

The dispersoid concentration when the conductive fine particles are dispersed in a dispersion medium is preferably 1% by mass or more and 80% by mass or less, and can be adjusted according to the desired film thickness of the conductive film. If it exceeds 80% by mass, aggregation tends to occur and it becomes difficult to obtain a uniform film.
The surface tension of the liquid containing the conductive fine particles thus adjusted is preferably in the range of 0.02 N / m to 0.07 N / m. When the liquid material is discharged by the droplet discharge method, if the surface tension is less than 0.02 N / m, the wettability of the ink composition with respect to the nozzle surface increases, and thus flight bending easily occurs. This is because if it exceeds m, the shape of the meniscus at the tip of the nozzle is not stable, and it becomes difficult to control the discharge amount and the discharge timing.

In order to adjust the surface tension, a trace amount of a surface tension adjusting agent such as a fluorine-based material, a silicone-based material, or a nonionic-based material can be added to the liquid material in a range that does not unduly reduce the contact angle with the receiving layer 2. The nonionic surface tension modifier improves the wettability of the liquid to the substrate, improves the leveling property of the film, and helps to prevent the occurrence of crushing of the coating film and the generation of the itchy skin.
The liquid may contain an organic compound such as alcohol, ether, ester, or ketone as necessary.

The liquid preferably has a viscosity of 1 mPa · s to 50 mPa · s. When discharging by the droplet discharge method, if the viscosity is less than 1 mPa · s, the nozzle periphery is easily contaminated by the outflow of ink, and if the viscosity is more than 50 mPa · s, the nozzle hole is clogged frequently. This is because it becomes difficult to smoothly discharge droplets.
In the present embodiment, a gold fine particle dispersion (trade name “Perfect Gold” manufactured by Vacuum Metallurgical Co., Ltd.) in which gold fine particles having a particle diameter of 10 nm are dispersed in α-terpineol was used as the conductive ink.

As a liquid droplet ejection apparatus that ejects a liquid containing such conductive fine particles, an apparatus including the liquid droplet ejection head 10 shown in FIGS. 2A and 2B is preferably used.
Here, as shown in FIG. 2A, the droplet discharge head 10 includes, for example, a stainless steel nozzle plate 12 and a vibration plate 13, which are joined via a partition member (reservoir plate) 14. is there. A plurality of spaces 15 and a liquid reservoir 16 are formed between the nozzle plate 12 and the diaphragm 13 by the partition member 14. Each space 15 and the liquid reservoir 16 are filled with ink, and each space 15 and the liquid reservoir 16 communicate with each other via a supply port 17. A plurality of nozzle holes 18 for ejecting ink from the space 15 are formed in the nozzle plate 12 in a line. On the other hand, a hole 19 for supplying ink to the liquid reservoir 16 is formed in the vibration plate 13.

Further, a piezoelectric element (piezo element) 20 is joined to the surface of the diaphragm 13 opposite to the surface facing the space 15 as shown in FIG. The piezoelectric element 20 is positioned between a pair of electrodes 21 and is configured to bend so that when it is energized, it projects outward. The diaphragm 13 to which the piezoelectric element 20 is bonded in such a configuration is bent integrally with the piezoelectric element 20 at the same time so that the volume of the space 15 is increased. It is going to increase. Therefore, ink corresponding to the increased volume in the space 15 flows from the liquid reservoir 16 through the supply port 17. Further, when energization to the piezoelectric element 20 is released from such a state, both the piezoelectric element 20 and the diaphragm 13 return to their original shapes. Therefore, since the space 15 also returns to its original volume, the pressure of the ink inside the space 15 rises, and ink droplets (liquid material) 22 are ejected from the nozzle holes 18 toward the substrate.
As a droplet discharge method (inkjet method) of the droplet discharge head 10, a known method other than the piezo jet type using the piezoelectric element 20 may be adopted.

By using the droplet discharge head 10 having such a configuration, in this example, as shown in FIG. 1B, a liquid droplet 22 of a liquid material is formed in a desired pattern, for example, at a predetermined position on the receiving layer 2. Discharge and apply to the wiring pattern shape.
Here, in the present embodiment, a coating pattern is selected according to the contact angle of the green sheet 1 with respect to the liquid (metal ink), and here, a case where the contact angle is 30 ° or more and 60 ° or less will be described. .

  The interval between the droplets applied on the green sheet 1 is controlled by controlling the ejection frequency and the relative speed of the droplet ejection head 10 and the green sheet 1. In particular, it is desirable that the droplets 22 adjacent to each other in the same wiring are applied so as to cause an overlap of 1% to 10% of the diameter of the liquid when applied on the green sheet 1. In other words, the interval between the droplets 22 is desirably 90% or more and 99% or less of the diameter of the liquid applied on the green sheet 1. If the interval between the droplets 22 is narrower and the overlap is larger than this, a bulge is generated and a good line cannot be formed. On the other hand, if the interval between the droplets 22 is wider than this and the overlap is small, there is a possibility that the overlap of the liquid does not occur due to the ejection position accuracy error and a cut wiring is formed.

When the liquid material is discharged and applied onto the liquid repellent film 2 in this way, the conductive fine particles 3 in the liquid material mainly do not penetrate deeply into the green sheet 1 as shown in FIG. Since it stays as an aggregate (lumps) of fine particles on the surface (near the surface), the conductive component does not reach the lower surface side of the green sheet 1, and unnecessary conduction between the upper and lower surfaces can be prevented. become.
The aggregate 3a of the conductive fine particles 3 remaining on the liquid-repellent film 2 is also continuously formed in a desired pattern, for example, a wiring pattern formed by all the aggregates 3a that come into contact with each other. It will be in shape.

(Through hole formation and metal filling process)
For the green sheet 1 coated with metal ink, a through hole is formed at a predetermined position using a punching machine, a die press or the like. Note that the through hole may be formed by laser irradiation.
Subsequently, the formed through hole is filled with a metal paste. As the metal filling method, a dispenser or screen printing may be used, but it is preferable to fill the above-described metal ink by using a droplet discharge method from the viewpoint of cost reduction and shortening of work.

(Lamination process)
Thereafter, as shown in FIG. 3, a plurality of green sheets 1 (including the liquid repellent film 2) from which the base plate has been removed are stacked at the same position. Thereafter, if necessary, other passive components are embedded. For example, thermocompression bonding is performed at 100 ° C. and a pressure of 100 to 150 kg / cm ² .
A wiring 31 made of a conductive pattern 4 (conductive film pattern) is formed on the green sheet 1 in FIG. 3 with a liquid repellent film 2 interposed therebetween. Further, a green sheet as an insulating layer having the same configuration is formed on the wiring 31. A (non-fired ceramic substrate) 32, a liquid repellent film 33, and a wiring 34 are formed.
Conductive posts (conductor posts) 35 in which the above-described through holes are filled with metal are formed on the wiring 31 in a continuous state.

Here, when the upper layer wiring 34 is formed, the wiring 34 is formed such that a part of the wiring 34 is located immediately above the post 35 so as to be electrically connected to the wiring 31 through the post 35 formed on the lower layer. . That is, the droplet 22 is ejected from the droplet ejection head 10 to a position directly above the post 35 to form the wiring 34. Therefore, the formed wiring 34 is electrically connected to the lower wiring 31 through the post 35 formed on the lower side.
In FIG. 3, a two-layer wiring composed of a lower layer wiring 31 and an upper layer wiring 34 is used. However, by stacking green sheets, posts, and wirings in this order on the wiring 34 in this order, three or more layers are formed. A multilayer wiring board can be formed.

(Heat treatment process)
Subsequently, a binder removal treatment was performed at 400 ° C., followed by firing at 900 ° C., thereby obtaining a ceramic multilayer wiring board.
In addition, since monomolecular films, such as FAS, are very thin, what decomposes | disassembles after baking and remains on the green sheet 1 becomes a negligible quantity, and adhesive force etc. do not become a problem.

  As described above, in the present embodiment, the conductive film pattern is formed by applying the metal ink to the liquid repellent film 2 formed on the green sheet 1, so that the conductive film forming component contained in the liquid or The solvent or the like does not penetrate deeply into the green sheet 1 and stays on the surface (near the surface) and does not reach the green sheet. Therefore, even when green sheets are stacked in multiple layers, the upper and lower layers are conducted in unnecessary portions, preventing them from functioning as a multilayer substrate, while reducing the cost and shortening the time by using the droplet discharge method. The effect that can be obtained.

(Example)
Thickness of liquid repellent treatment of a liquid in which xylene is added to a gold fine particle dispersion (trade name “Perfect Gold”, manufactured by Vacuum Metallurgical Co., Ltd.) in which gold fine particles having a diameter of 10 nm are dispersed in toluene, and the viscosity is 3 cp. A conductive film line was formed on a 100 μm green sheet by discharging with a droplet discharge device at a predetermined dot interval. The dot interval was changed by adjusting only the ejection frequency while keeping the stage moving speed constant. As an inkjet head, a commercially available printer (trade name “MJ930C”) was used. However, since the ink suction part is made of plastic, the suction part is changed to a metal jig so as not to dissolve in the organic solvent.

The liquid repellent treatment of the green sheet was performed by the following method.
In order to form a liquid repellent self-assembled film on the entire surface of the green sheet, the green sheet and 0.5 ml of tridecafluoro-1,1,2,2 tetrahydrooctyltriethoxysilane are placed in the same sealed container. For 48 hours at room temperature, a self-assembled film having a fluoroalkyl group on the surface was formed on the green sheet. The contact angle of the gold fine particle dispersion with respect to the treated green sheet was about 50 °.

  Then, when the line was formed by discharging at a dot interval of 70 μm, that is, a dot interval at which the overlap of droplets on the green sheet was 2 μm (about 3% with respect to the dot diameter on the green sheet), a dot was formed. Although the shape remained and the shape was wavy, a stable line without disturbance was formed. The green sheet was heat-treated at 300 ° C. for 30 minutes with a hot plate to obtain a gold wire having a thickness of 0.5 μm. Its resistivity was approximately 5 μΩcm.

(Second Embodiment)
When the contact angle of the green sheet with respect to the liquid is 60 ° or more, the droplets applied to the green sheet easily move before drying to form a bulge called a bulge, and the other parts are thin. It can happen that the wire breaks.
For this reason, in the present invention, a plurality of liquid material application patterns are selected in accordance with the contact angle. In the present embodiment, the application pattern particularly suitable for use when the contact angle is 60 ° or more is shown in FIG. This will be described with reference to FIG.

(First discharge process)
First, a droplet L1 of a dispersion liquid containing metal fine particles is discharged from the droplet discharge head 10 and dropped onto a wiring formation region on the substrate W. As shown in FIG. 4, the droplets L1 are ejected at a pitch larger than the diameter after the droplets L1 have landed on the substrate W. That is, the droplets L1 are ejected at regular intervals so as not to contact each other on the substrate W. 4 to 9, a green sheet having a liquid repellent film formed on the surface is illustrated as the substrate W.

  After the droplet L1 is discharged over the entire wiring formation region, a drying process is performed as necessary in order to remove the dispersion medium. The drying process can be performed by lamp annealing, for example, in addition to a process using a normal hot plate or an electric furnace for heating the substrate W. The light source used for lamp annealing is not particularly limited, but excimer laser such as infrared lamp, xenon lamp, YAG laser, argon laser, carbon dioxide laser, XeF, XeCl, XeBr, KrF, KrCl, ArF, ArCl, etc. Can be used as a light source. In general, these light sources have an output in the range of 10 W to 5000 W, but in the present embodiment, a range of 100 W to 1000 W is sufficient.

At this time, not only the removal of the dispersion medium but also the degree of heating and light irradiation may be increased until the dispersion is converted into a conductive film. However, the conversion of the conductive film may be performed collectively in the heat treatment / light treatment process after all the discharge processes are completed, and therefore it is sufficient that the dispersion medium can be removed to some extent in the first discharge process. Therefore, in the case of heat treatment, it is usually sufficient to perform heating at about 100 ° C. for several minutes.
Also, the drying process can proceed simultaneously with the ejection. For example, drying can proceed immediately after landing of the substrate W by discharging to a heated substrate W or by cooling the droplet discharge head 10 and using a dispersion medium having a low boiling point.
After drying, the droplet L1 becomes a dry film S1. As shown in FIG. 5, the volume of the dry film S1 is remarkably reduced by the removal of the dispersion medium, the viscosity is increased, and the dry film S1 is easily fixed at a predetermined position in the wiring formation region.

(Second discharge process)
Next, the droplet L2 of the dispersion liquid is discharged from the droplet discharge head 10 and dropped onto the wiring formation region on the substrate W. The droplet L2 is a droplet of the same dispersion as the droplet L1, and has the same volume. As shown in FIG. 6, the droplet L2 is dropped substantially at the center between the droplet L1 and the droplet L1. That is, the pitch of the droplet L2 and the droplet L1 is the same, and the droplet L2 is also ejected at a pitch larger than the diameter after landing on the substrate W. Accordingly, the droplets L2 do not come into contact with each other on the substrate W.
At this time, the droplet L2 and the dry film S1 are in contact with each other, but since the dispersion medium has already been completely or partially removed from the dry film S1, the two do not attract each other to generate a bulge.
In FIG. 6, the dropping start position of the droplet L2 is set from the left side of the drawing, which is the same as that of the droplet L1, but the dropping may be started from the opposite direction (right side of the drawing). In this case, the first discharge process and the second discharge process can be performed by reciprocating the relative movement between the droplet discharge head 10 and the substrate W once.

In order to remove the dispersion medium after discharging the droplet L2 over the entire wiring formation region, a drying process is performed as necessary, as in the first discharge step. In this case, not only the dispersion medium but also the degree of heating and light irradiation can be increased until the dispersion liquid is converted into a conductive film, but it is sufficient if the dispersion medium can be removed to some extent. Similarly to the first discharge step, the drying process can proceed simultaneously with the discharge.
After drying, the droplet L2 becomes a dry film S2. As shown in FIG. 7, the volume of the dry film S2 is remarkably reduced by the removal of the dispersion medium, the viscosity is also increased, and the dry film S2 is easily fixed at a predetermined position in the wiring formation region.
Thereby, a linear dry film pattern in which the dry film S1 and the dry film S2 are continuous is formed.

Here, the discharge positions in the first discharge process and the second discharge process will be described in more detail with reference to the plan view of FIG.
As shown in FIG. 8, the pitch P1 of the droplets L1 is larger than the diameter R1 of the droplets L1 after landing on the substrate W, and the droplets L1 are ejected at an interval d1 (d1 = P1-R1). The Further, the pitch P2 of the droplets L2 is larger than the diameter R2 of the droplets L2 after landing on the substrate W, and the droplets L2 are ejected at an interval d2 (d2 = P2-R2). Here, the volumes of the droplet L1 and the droplet L2 are equal, and the relationship of R1 = R2 is substantially satisfied. However, in the second ejection step, the lyophilic property is higher on the dry film S1 than on the substrate W. Since R2 increases, R2 becomes slightly larger in the length direction than R1. Further, the pitch P1 and the pitch P2 are equal to each other and have a relation of d1 = d2. However, since R2 is slightly larger in the length direction than R1, d2 is compared with d1. Slightly smaller.
D1 is preferably 10 μm or more. Thereby, even if it considers that the error of the landing position of a droplet and R2 become slightly large, it is possible to reliably perform discharge so that droplets that are subsequently discharged do not come into contact with each other.

(Third discharge process)
Next, the droplet L3 of the dispersion is discharged from the droplet discharge head 10 and dropped onto the dry film S1 and the droplet dry film S2 in the wiring formation region on the substrate W. The droplet L3 is also a droplet of the same dispersion as the droplet L1 and the droplet L2, and has the same volume. As shown in FIG. 9, the pitch P3 of the droplets L3 is smaller than the pitch P1 and the pitch P2, and smaller than the diameter R3 of the droplets L3 after landing on the substrate W. Accordingly, the droplets L3 overlap each other on the substrate W.
At this time, the substrate W on which the droplet L3 lands contacts the dry film S1 and the dry film S2, but since the dispersion medium has already been completely or partially removed from the dry film S1 and the dry film S2, The droplet L3 does not attract the bulge because they attract each other.
In addition, although the droplets L3 overlap each other, the wiring formation region is made lyophilic by the dry film S1 and the dry film S2, so that the droplet L3 leaves the wiring formation region, and the contact angle is preferably 60 [deg] or more. Does not flow out of the wiring formation region processed to 90 [deg] or more. Therefore, the droplet L3 tends to stay in the wiring formation region, does not attract each other to generate a bulge, and the line width does not increase.
The weight d3 of the droplet L3 and the droplet L3 is preferably 20 to 50% of R3. Thereby, it is possible to effectively increase the film thickness, and it is possible to prevent the liquid amount from being excessive and overflowing outside the wiring formation region.

The step of discharging the droplet L3 over the entire wiring formation region can be repeated a plurality of times. Thereby, a wiring with a desired film thickness can be obtained.
In this case, in order to remove the dispersion medium after each discharging step, a drying process is performed as necessary, similarly to the first discharging step and the second discharging step. In this case, not only the dispersion medium but also the degree of heating and light irradiation can be increased until the dispersion liquid is converted into a conductive film, but it is sufficient if the dispersion medium can be removed to some extent. Similarly to the first discharge process and the second discharge process, the drying process can proceed simultaneously with the discharge.
After drying, the droplet L3 becomes a dry film S3 (not shown). The volume of the dry film S3 is remarkably reduced by the removal of the dispersion medium, the viscosity is increased, and the dry film S3 is easily fixed at a predetermined position in the wiring formation region. Therefore, even if the process of discharging the droplets L3 to the entire wiring formation region is repeated a plurality of times, the droplets between the processes do not attract each other and a bulge is not generated.
In addition, since the portion where the droplet has been dropped first is lyophilic, the droplet L3 does not flow out of the wiring formation region. Therefore, even if the droplet L3 is repeatedly ejected, the droplet L3 tends to stay in the wiring formation region, does not attract each other to generate a bulge, and the line width does not increase.
Through the above steps, a dry film layer having a desired thickness can be formed while maintaining a line width substantially equal to the diameter of the droplet.
In addition, although the application pattern in this Embodiment is suitable especially when a contact angle is 60 degrees or more, it cannot be overemphasized that it can be used even if it is 30 degrees-60 degrees.
As described above, in the present embodiment, since droplets can be ejected with an optimum coating pattern corresponding to the contact angle, it is possible to deal with combinations of various metal inks and liquid repellent films.

(Example)
The green sheet formed to a thickness of 100 μm was subjected to atmospheric pressure plasma treatment using CF ₄ gas to make the surface liquid-repellent. The contact angle of the metal ink with this surface was 70 °.
To this green sheet, xylene is added to a gold fine particle dispersion (trade name “Perfect Gold”, manufactured by Vacuum Metallurgical Co., Ltd.) in which gold fine particles having a diameter of 10 nm are dispersed in toluene, the viscosity is 8 cp, and the surface tension is 24 N. / M was discharged at a predetermined pitch by a droplet discharge device to form a conductive film line. The above-described printer head was used as the droplet discharge head.

The ejection was performed using only one nozzle, and ejection was performed at an ejection voltage of 15 V throughout the entire ejection process. The diameter of the droplet after landing on the substrate was about 55 μm.
First, as a first discharge step, the droplets were discharged in a straight line with a pitch of 70 μm and a distance between the droplets of 15 μm so that the droplets were not connected to each other. Then, the drying process for 5 minutes was given at 100 degreeC using the dryer.
Next, as the second discharge step, the pitch was set to 70 μm and the distance between the droplets was set to 15 μm in the same manner as in the first discharge step. The liquid droplets ejected in the second ejection process were ejected so as to land almost in the middle of the liquid ejected in the first ejection process. Then, the drying process for 5 minutes was given at 100 degreeC using the dryer. Thereby, a line without disconnection between the droplets was formed.
Further, as a third step, a step of discharging onto a line formed by the first discharge step and the second discharge step with a pitch of 30 μm and an overlap between droplets of 25 μm is sandwiched by a drying step at 100 ° C. for 5 minutes. Repeated three times. As a result, a line having a good shape was obtained while maintaining the same line width of 55 μm as the diameter of the liquid droplet without increasing the line width every time of overcoating.
It was baked at 300 ° C. for 30 minutes to obtain a gold line having a gold luster. The film thickness was 1 μm and the specific resistance was 5 × 10 ⁻⁶ Ωcm.

It is a principal part side cross section for demonstrating the manufacturing method of this invention to process order. It is a figure for demonstrating schematic structure of a droplet discharge head. It is principal part side sectional drawing which shows an example of the wiring board of this invention. It is process drawing of the manufacturing method which concerns on 2nd Embodiment. It is process drawing of the manufacturing method which concerns on 2nd Embodiment. It is process drawing of the manufacturing method which concerns on 2nd Embodiment. It is process drawing of the manufacturing method which concerns on 2nd Embodiment. It is process drawing of the manufacturing method which concerns on 2nd Embodiment. It is process drawing of the manufacturing method which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 32 ... Green sheet (unfired ceramic substrate), 2, 33 ... Liquid repellent film, 4 ... Conductive film pattern (conductive pattern), 22, L1 ... Droplet (liquid body), 31, 34 ... Wiring, 35 ... Post (conductor post)

Claims (15)

A step of applying a liquid repellency treatment to the surface of the unfired ceramic substrate;
Applying a liquid material containing a conductive film forming component to the green ceramic substrate that has been made liquid repellent by a droplet discharge method;
Laminating a plurality of the unfired ceramic substrates coated with the liquid,
Heat-treating the laminated unfired ceramic substrate to form a conductive film pattern with the conductive film forming component;
A method for producing a multilayer wiring board, comprising: In the manufacturing method of the multilayer wiring board of Claim 1,
A multilayer wiring board comprising: a plurality of liquid droplet application patterns to be applied to the green ceramic substrate according to a contact angle of the liquid-repellent green ceramic substrate to the liquid material. Production method. In the manufacturing method of the multilayer wiring board of Claim 2,
In the coating pattern, the distance between the centers of the liquid droplets adjacent to each other on the unfired ceramic substrate is a radius of the droplet when landing on the unfired ceramic substrate, and the unfired ceramic. The liquid material is larger than the sum of the radius of the ink jet droplets before landing on the substrate and smaller than twice the radius of the droplets when landing on the unfired ceramic substrate. A method for producing a multilayer wiring board, comprising a pattern to be ejected. In the manufacturing method of the multilayer wiring board of Claim 2,
The coating pattern has a pattern for discharging the liquid material so as to cause an overlap of 1% to 10% of the diameter of the liquid material when landed on the unfired ceramic substrate. Manufacturing method. In the manufacturing method of the multilayer wiring board of Claim 3 or 4,
The method for manufacturing a multilayer wiring board, wherein the contact angle is 30 ° or more and 60 ° or less. In the manufacturing method of the multilayer wiring board of Claim 2,
The application pattern includes a first discharge step of discharging the liquid material at a pitch larger than the diameter of droplets after landing on the unfired ceramic substrate;
A second discharge step of discharging the liquid material at a pitch larger than the diameter of the droplet after landing on the unfired ceramic substrate at a position different from the discharge position in the first discharge step. A method for manufacturing a multilayer wiring board. In the manufacturing method of the multilayer wiring board according to claim 6,
A method for manufacturing a multilayer wiring board, wherein the pitch in the second ejection step is substantially the same as the pitch in the first ejection step. In the manufacturing method of the multilayer wiring board of Claim 6 or 7,
A method of manufacturing a multilayer wiring board, wherein a pitch in the first discharge step is not more than twice a diameter of a droplet after landing on the unfired ceramic substrate. In the manufacturing method of the multilayer wiring board in any one of Claim 6 to 8,
A method of manufacturing a multilayer wiring board, wherein a pitch in the first discharge step is 10 μm or more larger than a diameter of a droplet after landing on the unfired ceramic substrate. In the manufacturing method of the multilayer wiring board in any one of Claim 6 to 9,
A method of manufacturing a multilayer wiring board, comprising: a third discharge step of discharging a plurality of liquid droplets at a pitch smaller than the pitch in the first discharge step after the second discharge step. In the manufacturing method of the multilayer wiring board of Claim 10,
A method of manufacturing a multilayer wiring board, wherein a pitch in the third discharging step is equal to or less than a diameter of the droplet after landing on the unfired ceramic substrate substrate. In the manufacturing method of the multilayer wiring board in any one of Claim 6 to 11,
The method for producing a multilayer wiring board, wherein the contact angle is 30 ° or more. In the manufacturing method of the multilayer wiring board in any one of Claim 1 to 12,
The manufacturing method of the multilayer wiring board characterized by having the process of forming the conductor post which makes the said electroconductive pattern conduct | electrically_connect between several layers in the said unbaking ceramic substrate. In the manufacturing method of the multilayer wiring board according to claim 13,
A method of manufacturing a multilayer wiring board, wherein the conductor post is formed by a droplet discharge method. A multilayer wiring board comprising a conductive film pattern formed by the method for manufacturing a multilayer wiring board according to claim 1 as wiring.

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