JPS63182887A - Manufacture of ceramic wiring circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention belongs to the technical field related to ceramic wiring boards. In particular, the present invention relates to a technique for forming circuits on irregularly shaped (three-dimensional) substrates, unlike conventional ceramic printed circuit boards in which circuits are formed on planar substrates. Furthermore, the present invention also relates to technology for making electronic devices more compact and lightweight by applying them to electronic device cases and the like.

[Background Art] In recent years, the demand for smaller and lighter electronic devices has become stricter year by year, and the miniaturization of electronic components is progressing day by day. Electronic circuit boards have also progressed from single-sided wiring to double-sided wiring and then to multilayers, and flexible wiring boards are also being put into practical use to pack as many functions as possible into the limited space of electronic devices.

Furthermore, as a method of packing in functions, a method has been adopted in which the case of the electronic device and the wiring are integrated, that is, a method of providing a wiring circuit on the surface of the case. in this case,
The material used is a metal substrate with an aluminum base and an epoxy resin insulating layer on top. To manufacture this, a circuit is first formed on a flat metal substrate, and then a case is formed using a press, and is used in calculators, small radios, and the like.

As mentioned above, conventional shapes with irregular shapes (non-planar)
Wired circuit boards are almost entirely made of plastic or plastic-metal composite materials, and printed circuit boards made of ceramics have been limited to planar ones.

[Object of the Invention] An object of the present invention is to provide a printed circuit board having an irregular shape that is useful for, for example, making electronic equipment more compact and lighter.

[Disclosure of the Invention] To make a non-planar ceramic wiring circuit board, first,
One possible method is to mold and fire non-planar ceramics and then form circuits by printing or other methods, but this method has the trouble of printing on curved surfaces.

Therefore, the present inventors solved this problem by forming a circuit before firing the ceramic, then molding it into a predetermined three-dimensional shape, and then firing the ceramic and the conductive circuit simultaneously. .

This invention will be explained in detail step by step.

(1) Process of preparing ceramic green sheets.

As the ceramic, considering the properties after molding and firing, it is preferable to use a ceramic raw material powder whose main component is glass having the following composition (A), (B), (C) or (D).

(A) Sing 48-63% by weight Aitos
10 to 25% by weight B, 02 4 to 10% by weight MgO 10 to 25% by weight (B) The composition of the main component is the composition of (A) above, and as a subcomponent T i Ots Z rogSSnow, P2
A glass powder containing 5% by weight or less of a metal compound serving as a nucleating agent of at least one selected from the group consisting of O2, ZnO, MoOs, As, and O.

(C) The main component has the composition of (A) above, and 3 to 20% by weight of the MgO used is BaO, Sro and C.
A glass powder substituted with at least one member selected from the group consisting of aO.

(D) The composition of the main component is the composition of (C) above, and the subcomponent is T i O! , Zr0t, S n Ot, P2
A glass powder containing 5% by weight or less of a metal compound serving as a nucleating agent of at least one selected from the group consisting of O1, ZnOsMoO3, and Aszoi.

The glass having the basic composition (A) is a so-called magnesia aluminosilicate glass, and the reason why this glass is particularly preferable is as follows.

In other words, so that metals such as gold, silver, palladium, and copper, which have low electrical resistance as semiconductors, can be fired simultaneously with ceramics, the sintering temperature of ceramics must be kept below 1000°C, and magnesia aluminosilicate glasses are suitable for this purpose. can meet your requirements. On the other hand, commonly used alumina-based ceramics cannot be used for the purpose of this invention because the temperature is much higher than this.

Furthermore, magnesia aluminosilicate glass is particularly advantageous in terms of electrical properties (electrical insulation, dielectric constant, etc.), coefficient of thermal expansion, and the like.

The reason why the composition range (A) is preferable is as follows.

That is, when the composition ratio of Sin exceeds 63% by weight, it is difficult to form a dense sintered body. If the weight is less than 48 weight, the crystallization temperature will increase, and at a firing temperature of 950° C. or lower, sufficient crystallization may not be achieved or densification may become difficult.

When the composition ratio of Al z Os exceeds 25% by weight,
The temperature at which sintering can be performed increases, and sufficient sintering cannot be performed at a sintering temperature of 950° C. or lower. If the weight is less than 100 oz, the number of cordierite crystals decreases, and many 5ioz MgO-based crystals precipitate, resulting in an increase in dielectric constant.

If the composition ratio of MgO exceeds 25% by weight, this is probably due to the precipitation of magnesium silicate, but deformation becomes large and it is impractical. If it is less than 10% by weight, it will be difficult to form a dense sintered body.

B! 0. If the composition ratio exceeds 10% by weight, the glass phase will increase, foaming will occur easily, and the firing temperature range will become narrower. In addition, the mechanical strength is low, making it impractical.

If it is less than 4% by weight, crystallization of the surface layer of the glass powder progresses too rapidly, making it difficult to form a dense crystalline body.

The nucleating agent is added to promote crystallization, but if the amount of the nucleating agent mentioned above exceeds 5% by weight, crystallization will proceed too rapidly and a dense sintered body will not be obtained.

In the glass having the composition (D) above, if the substitution rate of alkaline earth metal oxide exceeds 20% by weight, the Mgo component becomes too small, resulting in poor precipitation of α-cordierite crystals and poor electrical properties. If it is less than 3% by weight, the effect of substitution will not appear. In the case of this glass,
If the nucleating agent exceeds 3% by weight, crystallization will proceed too rapidly and a dense crystal will not be formed.

Methods for producing green sheets from these ceramic powders are broadly divided into extrusion molding methods and doctor blade molding methods.

In the extrusion molding method, first, a ceramic raw material powder, a binder, a plasticizer, a dispersant, and water (or an organic solvent) are mixed and kneaded, and the mixture is extruded into a sheet from an extrusion die using an extrusion molding machine. It is possible to extrude a thin sheet of 0.2 fi and a thick sheet of several 1 fi.

On the other hand, in the doctor blade molding method, ceramic raw material powder is mixed with a binder, a dispersant, a plasticizer, water and/or an organic solvent, and the slurry is poured through the gap between a knife called a doctor blade and a polyester film. The film is then coated, the slurry is dried on the film, and then peeled off to create a sheet. This method is advantageous for forming thin sheets, and sheets of 0.05 m to 1 piece can be formed.

For the purpose of the present invention, any method may be used, but a combination of binder, plasticizer, and dispersant suitable for each method must be selected.

As the binder used when forming the sheet, cellulose type (methyl cellulose, ethyl cellulose), PVA, acrylic type, polyvinyl butyral, etc. are mainly used.

As the plasticizer, dibutyl phthalate, dioctyl phthalate, glycerin, etc. are used, and as the dispersant, a nonionic surfactant is used.

(2) A method of forming a conductor circuit on a green sheet.

Broadly speaking, two methods are effective for the purpose of the present invention.

The first method is to print directly onto the green sheet, in which the green sheet is pre-drilled (if necessary) and then a conductive paste that matches the ceramic is printed by screen printing.

The second method is to set a transfer paper. This method uses screen printing or transfer printing to print a conductive paste on a polymer film with good thermal decomposition, and then set the transfer paper. This is a method of attaching or pasting onto a green sheet before press forming.

The conductor paste used here is a ceramic material,
In other words, it must be selected depending on the sintering characteristics.

When the ceramic is glass ceramic, as in the case of this invention, it is possible to sinter it at approximately 1000° C. or lower, so metal pastes such as gold, silver, copper, palladium, etc. are used.

According to the direct printing method, the printed metal paste comes into direct contact with the surface of the mold during press forming, and stress is applied to it, so press forming that involves extreme bending, twisting, or drawing is not possible. I can't hope for that.

On the other hand, in the other method of setting the transfer paper, only the film-like transfer mount comes into contact with the surface of the molding die, so there is almost no possibility of major damage to the circuit.

Although it increases the cost, this method is advantageous for ceramics that are highly deformed.

(3) Method of forming into irregular shapes.

Press molding is preferable to mold the circuit-formed green sheet into an irregular shape. The molding conditions are determined depending on the material properties determined by the material composition of the green sheet.

For example, when a ceramic material is extruded using a thermoplastic acrylic binder, a method is used in which the sheet is heated in advance to make it flexible and then press-molded using a cooled mold.

In addition, in the case of ceramic materials such as extrusion-molded sheets using methylcellulose as a binder, which has the property of gelling under heat, a method is used in which the sheet is kept at room temperature or below and then press-molded using a heated mold. .

The key to molding is to release the formed thin sheet from the mold without losing its shape. Conditions for this must be set on a case-by-case basis.

(4) Method of firing.

Points to keep in mind when firing a green sheet formed into a non-planar shape are: ■Appropriate setting of binder removal conditions; ■Appropriate setting of sintering temperature; ■Control of the firing atmosphere. , (2) Matching jigs for holding the sheet, etc. A step-by-step explanation will be given below.

■ Conditions for removing the binder.

The binder required for molding must be removed by decomposition and sintering before sintering. If binder removal is insufficient, binder residue (mainly carbon) remains, which adversely affects the insulation properties of the fired product. If the temperature applied to remove the binder is too rapid, the sheet may blister, crack, or become deformed. Therefore, a method is generally adopted in which the temperature is raised as slowly (as slowly as possible) in a temperature range where the binder decomposes and sinters. For example, in the case of a sheet molded using a methyl cellulose binder, the temperature is raised to 300° C. to 500° C. over a period of 2 hours to 4 hours.

■　Sintering temperature.

The sintering temperature should be set according to the sintering characteristics determined by the type of ceramic material. The glass ceramic system of this invention requires 30 minutes to 3 hours at a temperature of 800°C to 1000°C.

If sintering is insufficient, the density will not rise to the theoretical density, and therefore voids will remain, resulting in a product with low strength and poor moisture resistance. If sintering becomes excessive, the sheet may become soft and deformed, the grains of the ceramic may grow excessively, causing a decrease in strength, and the metal used as a conductor may melt, diffuse, or volatilize.

■ Baking atmosphere.

When using gold, silver, or palladium-based metals as conductors, firing can be done in air, and there is no need to be very careful about the atmosphere. When copper, tungsten, molybdenum, manganese, etc. are used as a conductor, when fired in an oxidizing atmosphere, the metal turns into an oxide and cannot function as a conductor. Therefore, when copper is used, at least A non-oxidizing atmosphere is required, and nitrogen is often used.

■ Baking jig.

If a shaped sheet of irregular shape is placed on the center of a flat plate and fired, it may deform under its own weight if exposed to the high temperatures during sintering. In such a case, it is necessary to take measures such as changing the way it is placed or placing a supporting jig so that it does not deform even under its own weight.

Hereinafter, a more detailed explanation will be given focusing on examples.

First, preparation of the glass ceramic material used in each example will be explained.

[Preparation of glass ceramic materials]

According to the formulation shown in Table 1, each raw material was mixed in the form of oxide and carbonate (ptos in the form of aluminum metaphosphate) and placed in a crucible in an electric furnace at 1450-1550°C. After the mixture was poured into water and melted for 2 to 5 hours, it was poured into water and cooled to obtain a current. This was wet-pulverized in a ball mill and used in the following examples.

The five types of glass powder obtained were formed into a tablet shape (Φ#20mm, thickness #5fl) by dry pressing, and a sintering test was conducted at a temperature of 900 to 950°C. The glass powders from G-4 to G-4 were able to be sintered to the point where a dense sintered body was obtained, but when glass powder from G-5 was used and sintered, the water absorption rate was over 20% by weight. Therefore, it was not used in the experiment.

[Example 1] (1) Green sheet preparation materials and blended glass powder (G-1) 100 parts by weight Methyl cellulose 10 Wax emulsion 5 Diethylene glycol
3 Water 23
The blends of 4 or more were combined and kneaded for about 30 minutes in a pressure kneader, and then applied to an extruder to form a green sheet with a thickness of 1.5 mm.

(2) Conductor paste printing A circuit was printed on the previously prepared green sheet by screen printing using a conductor paste containing copper as the main component.

(3) Press molding The green sheet described above was placed in a mold heated to 100° C. without preheating, and molded into an irregular shape by direct pressure press molding. The shape of this molded product is shown in FIG. In this figure, 1 indicates ceramics and 2 indicates a conductor.

(4) Firing The product was fired in a box-shaped electric furnace in an air atmosphere by keeping the maximum temperature at 950°C for 1 hour. To remove the binder, the temperature is 30°C to 50°C during the temperature increase process.
The temperature was raised within a range of 0°C over 3 hours.

As a result of the above process, as shown in FIG. 1, an irregularly shaped ceramic printed circuit board with a conductor circuit formed on the back surface of the case was obtained.

[Example 2] (1) Preparation of green sheet It was conducted using the following materials and formulations.

Glass powder (G-2) 100 parts by weight
Methylcellulose 12 Wax emulsion 4 Diethylene glycol
3 #Water
The above blends were kneaded in a pressure kneader for about 30 minutes, and then molded into a green sheet with a thickness of 1.8 fl by an extruder.

(2) Creation of transfer film printed with conductor paste Polymethyl methacrylate resin sheet (thickness 10μ
), a circuit was printed using a screen printing method using a conductor paste containing fine powders of silver and palladium as main components.

(3) Simultaneous molding of transfer film and green sheet in close contact.

A transfer film was set on the green sheet prepared in (1) above, and placed in a mold kept at about 70°C.
It was molded into an irregular shape as shown in FIG. 1 by direct pressure press molding.

(4) Firing Firing was performed under the same conditions as in Example 1 to obtain an irregularly shaped ceramic printed circuit board.

[Example 3] (1) Preparation of green sheet It was conducted using the following materials and formulations.

Glass powder (C;-3) 100 parts by weight Polyvinyl butyral 15 Dibutyl phthalate 6 Antifoaming agent
1 Toluene 20 #Methyl ethyl ketone 20 Ethyl alcohol 7 This mixture was placed in a ball mill, dissolved, mixed and pulverized for 24 hours, and then defoamed using a vacuum defoaming machine to create a slurry. Next, this slurry was formed into a green sheet with a thickness of about 1 mm by a doctor blade method.

(2) Printing of conductive paste A conductive paste containing gold as a main component was printed on the green sheet prepared in (1) above by screen printing to form a circuit.

(3) Press molding After preheating the above green sheet (placed in a dryer set to 70°C for 15 minutes), it is placed in a mold kept at 20°C or below, and then directly press molded as shown in Figure 1. It was molded into an irregular shape as shown in the figure.

(4) Firing Ceramic circuit boards were obtained by firing under substantially the same conditions as in Example 1 to form irregularly shaped conductor circuits.

[Example 4] (1) Preparation of green sheet It was conducted using the following materials and formulations.

Glass powder (G-4) 100! Parts Polyvinyl butyral 15 Dibutyl phthalate 5 Antifoaming agent
1 Toluene 20 Methyl ethyl ketone 20 Ethyl alcohol 7 This mixture was placed in a ball mill, dissolved, mixed and pulverized for 24 hours, and then defoamed in a vacuum deaerator to create a slurry. Next, this slurry was formed into a green sheet with a thickness of about 1 crane by a doctor blade method.

(2) Simultaneous adhesion molding of transfer film and green sheet The green sheet prepared in (1) above was coated with (
Set the transfer film prepared in 2), preheat it to about 70℃ (place it in a constant temperature machine set to 70℃ for 15 minutes), put it in a mold kept below 20℃, and perform direct pressure press molding. , and was molded into an irregular shape as shown in FIG.

(3) Firing The ceramic circuit board was fired under the same conditions as in Example 1 to obtain a ceramic circuit board on which an irregularly shaped conductor circuit was formed.

Table 1 [Margin below] [Effects of the invention] This invention provides ceramic green sheets with 10
A circuit was formed on a ceramic green sheet using a ceramic material that can be sintered at 00°C or below, and using at least one metal selected from gold, silver, palladium, and copper as a conductor for the circuit. After that, it is press-molded and then fired, making it possible to create irregularly shaped ceramic circuit boards that were previously difficult to create through a simple process.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a ceramic circuit board obtained according to an embodiment of the invention. ■: Ceramics 2: Conductor Patent applicant Toshimaru Takemitsu (and 2 others), patent attorney representing Matsushita Electric Works Co., Ltd. Figure 1

Claims (2)

[Claims] (1) 1000℃ as a ceramic green sheet
After forming a circuit on a ceramic green sheet using a ceramic material that can be sintered as follows and using at least one metal selected from gold, silver, palladium, and copper as a conductor for the circuit, A method for producing a non-flat ceramic wiring circuit board, which is characterized by press molding and then firing. (2) The following (A) and (B) are used as ceramic materials.
, (C) or (D). A method for manufacturing a ceramic wiring circuit board according to claim (1), characterized in that a glass powder having a composition of (C) or (D) is used. (A) SiO_248-63% by weight Al_2O_310-25% by weight B_2O_34-10% by weight MgO 10-25% by weight (B) The composition of the main component is the composition of (A) above, and the subcomponents are TiO_2, ZrO_2, SnO_2, P_2
A glass powder containing 5% by weight or less of a metal compound serving as a nucleating agent of at least one selected from the group consisting of O_5, ZnO, MoO_3, and As_2O_3. (C) 3 to 20% by weight of MgO in the composition of (A) above
A glass powder in which is substituted with at least one member selected from the group consisting of BaO, SrO and CaO. (D) The composition of the main component is the composition of (C) above, and the subcomponents are TiO_2, ZrO_2, SnO_2, P_2
A glass powder containing 3% by weight or less of a metal compound serving as a nucleating agent of at least one selected from the group consisting of O_5, ZnO, MoO_3, and As_2O_3.