JP2001284770A - Circuit-patten formation method and wiring board formed thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit-pattern formation method which can prevent an increase in the electric resistance of a circuit pattern formed by an electrophotographic method and to provide a wiring board which is formed by the method. SOLUTION: The circuit-pattern formation method on a ceramic green sheet is composed of a charging process, an exposure process, a developing process, a transfer process and a fixing process. In the developing process, only a chargeable powder 16 for circuit formation is taken out from a two-component developer 15 which is filled into a feed means 14, and the chargeable powder 16 for circuit formation is electrostatically attracted to a latent-image pattern on the surface of a photoreceptor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a circuit pattern and a wiring board formed by the method, and more particularly, to a method for forming a circuit pattern on a ceramic green sheet by electrophotographic printing and a method for forming the circuit pattern. And a wiring board formed by the method.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a circuit pattern on a ceramic green sheet, there has been a screen printing method using a printing paste containing a metal powder. However, in the screen printing method, a screen must be made for each circuit pattern. In the case of a wiring board that often produces a small number of products, the number of screens increases, which is disadvantageous in terms of manufacturing efficiency and cost. In addition, there is a disadvantage that the screen must be re-produced even if the circuit pattern is partially changed, and a flexible response cannot be performed. Therefore, in recent years, an electrophotographic method of printing a chargeable powder for forming a circuit on a ceramic green sheet by electrostatic force has been put into practical use.

The chargeable powder for forming a circuit is mainly composed of a conductive metal powder and a thermoplastic resin. These are mixed at a predetermined weight ratio, and the mixture is melted and kneaded with a kneader. And then finely pulverized by a jet mill to adjust to, for example, a chargeable powder for forming a circuit having an average particle diameter of 20 μm or less, and to classify the powder. Then, the chargeable powder for forming a circuit thus manufactured is printed on a ceramic green sheet by electrophotography, and the ceramic green sheet is heated at 1000 ° C. in a reducing atmosphere to obtain a ceramic green sheet and a circuit pattern. By sintering, a circuit pattern formed on the ceramic substrate is obtained.

JP-A-11-193402 and JP-A-11-233365 disclose that a surface of a conductive metal powder (metal particles) such as copper or nickel is covered with a thermoplastic resin (thermoplastic insulator). Using a two-component developer (electrophotographic developer) composed of a chargeable powder for circuit formation (insulated surface-treated metal particles) and a carrier powder (carrier particles) of iron powder or ferrite. I have. According to this technique, in the developing step, the two-component developer in a state where the chargeable powder for forming a circuit is electrostatically adsorbed on the surface of the carrier powder is held by the developing sleeve by magnetic force, and the two-component developer is used for forming the circuit among the two-component developer. Only the chargeable powder moves toward the electrostatic latent image pattern formed on the photoconductor.

[0005]

However, when a conventional two-component developer is used to print a circuit pattern on a ceramic green sheet by electrophotography,
A phenomenon called carrier development in which when the electrostatic or magnetic balance is lost during the development process, both the chargeable powder for circuit formation and the carrier powder move to the electrostatic latent image pattern formed on the photoreceptor. Occurs. As described above, when the carrier powder moves to the latent image pattern on the photoconductor and the carrier powder is transferred onto the ceramic green sheet in the transfer step and adheres to the circuit pattern, there is a problem that the electric resistance of the circuit pattern increases. is there. That is,
Iron powder-based carrier powder is covered with iron oxide, and ferrite-based carrier powder is a compound with iron oxide.
In the calcination performed at about 1000 ° C. in a reducing atmosphere, the iron oxide component remains in the circuit pattern without being reduced, and as a result, the electrical resistance of the portion is considerably increased, and in some cases, almost broken. become.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a circuit pattern forming method capable of preventing an increase in electric resistance of a circuit pattern formed by electrophotography, and a circuit pattern forming method using the method. It is an object of the present invention to provide a finished wiring board.

[0007]

In order to solve the above-mentioned problems, a circuit pattern forming method according to the present invention comprises a charging step of charging a surface of a photoreceptor, and an electrostatic latent image pattern formed on the photoreceptor. Exposure step to form, take out only the circuit forming chargeable powder from a two-component developer consisting of carrier powder and circuit formation chargeable powder, and electrostatically force the circuit formation chargeable powder onto the latent image pattern A developing step of adhering, a transfer step of transferring the chargeable powder for circuit formation on the latent image pattern onto the ceramic green sheet, and fixing the chargeable powder for circuit formation transferred to the ceramic green sheet. A fixing step, wherein the carrier powder forming the two-component developer comprises: a circuit-forming metal; and an alloy of the circuit-forming metal. Containing more than 50% by weight of one or two or more in total of Gobutsu, surface is characterized in that which has been covered with an insulating coating.

[0008] A wiring board according to the present invention is characterized in that the ceramic green sheet on which the circuit pattern is printed is fired by the circuit pattern forming method described above.

Further, a wiring board according to the present invention is characterized in that the ceramic green sheets on which the circuit patterns are printed are laminated and fired by the circuit pattern forming method described above.

According to the circuit pattern forming method of the present invention,
Two-component developer containing a metal for forming a circuit, and a carrier powder containing at least 50% by weight in total of one or more of alloys and compounds of the metal for forming a circuit and having a surface covered with an insulating film Is used, it is possible to prevent the electric resistance of the circuit pattern from increasing even if the carrier powder adheres to the circuit pattern.

According to the wiring board of the present invention, a metal for forming a circuit and one or more of alloys and compounds of the metal for forming a circuit are contained in a total of 50% by weight or more, and the surface is formed of an insulating film. Using a two-component developer containing the covered carrier powder, the circuit pattern is printed on the ceramic green sheets by electrophotography, and then the ceramic green sheets are fired to form a wiring board.
A wiring substrate having a circuit pattern with low electric resistance can be easily manufactured.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an electrophotographic system used in an embodiment according to a circuit pattern forming method of the present invention. The circuit pattern forming method on the ceramic green sheet includes a charging step of charging the surface of the photoreceptor 12 by the corona charger 11, and irradiating the surface of the photoreceptor 12 with a laser beam 13 to obtain a desired latent image pattern (not shown). In the exposure step of forming the toner, only the chargeable powder for circuit formation 16 is taken out from the two-component developer 15 filled in the supply means 14, and the chargeable powder for circuit formation 16 is electrostatically applied to the latent image pattern on the surface of the photoconductor 12 Developing process for adsorption, ceramic green sheet 17
From the back surface of the substrate, a transfer device 18 applies a charge having a polarity opposite to that of the chargeable powder 16 for circuit formation to the ceramic green sheet 17 and transfers the chargeable powder 16 for circuit formation developed on the latent image pattern onto the ceramic green sheet 17. In the transfer step of transferring, the circuit forming chargeable powder 16 transferred onto the ceramic green sheet 17 by irradiation of the flash lamp 19 is fixed, and a circuit pattern (not shown) is formed on the ceramic green sheet 17. Be composed.

FIG. 2 is a sectional view of the two-component developer used in the circuit pattern forming method of FIG. Two-component developer 1
5 is composed of a chargeable powder 16 for forming a circuit and a carrier powder 21;
1 is electrostatically adsorbed on the surface of the substrate 1. In this case, the mixing weight ratio between the circuit-forming chargeable powder 16 and the carrier powder 21 is as follows:
It is desirable to set 10:90 to 30:70.

When the mixing weight ratio of the carrier powder 21 is 9
If it exceeds 0%, the carrier powder 21 together with the chargeable powder 16 for forming a circuit move to the latent image pattern formed on the photoreceptor 12, so that the carrier development becomes remarkable and it is difficult to form a precise circuit pattern. Becomes

On the other hand, when the mixing weight ratio of the carrier powder 21 is 7
If it is less than 0%, ground fog due to the chargeable powder 16 for forming a circuit is likely to occur.

The carrier powder 21 contains a circuit-forming metal 22 made of copper, nickel, chromium or the like, and the surface of the circuit-forming metal 22 is made of an insulating film made of polystyrene, poly-p-chlorostyrene, polyvinyl toluene, or the like. 23.

The insulating film 23 may be formed by a method such as hybridization or mechanical fusion in which the insulating film 23 is caused to collide with the surface of the circuit-forming metal 22 and mechanically fixed thereto, or the surface of the circuit-forming metal 22 is formed. And a method of polymerizing the insulating film 23.

The thickness of the insulating film 23 is adjusted in accordance with the developing characteristics when the chargeable powder 16 for forming a circuit is developed. The chargeable powder 16 for forming a circuit is the carrier powder 2
If it is desired to increase the resistance (carrier resistance) when moving away from 1 and moving toward the photoreceptor 12 (FIG. 1), the thickness is increased. [Example 1] 1-1. Preparation of Carrier Powder First, spherical nickel powder having an average particle diameter of 43 μm and styrene acrylic resin were mixed at a weight ratio of 60:40,
The mixture is put into a hybridization system manufactured by Nara Machinery Co., Ltd. and treated at 4000 rpm for 3 minutes. As a result, a carrier powder 21 in which a styrene acrylic resin as an insulating film 23 is adhered to the surface of a nickel powder as a metal 22 for forming a circuit is obtained. 1-2. Preparation of Two-Component Developer The chargeable powder 16 for forming a circuit and the carrier powder 21 obtained by the method 1-1 were mixed at a weight ratio of 15:85 to obtain a two-component developer 15. The chargeable powder 16 for forming a circuit has a weight ratio of copper powder to insulating resin of 90:10, and the average particle diameter of the surface of the spherical copper powder covered with the insulating resin is 7.3 μm.
Was used. 1-3. Preparation of Circuit Pattern Using the two-component developer 15 obtained by the method 1-2, the ceramic green sheet on which the circuit pattern is printed by the electrophotographic method shown in FIG. 1 is heated at 1000 ° C. in a reducing atmosphere. Then, the ceramic green sheet and the circuit pattern were sintered to form a circuit pattern on the ceramic substrate.

The printing of such a circuit pattern is performed for 1000 times.
After observing the circuit pattern after performing the process for 75 times,
It was confirmed that the carrier powder was attached to the m line. The electrical resistance of the normal line to which the carrier powder was not attached and the electrical resistance of the line to which the carrier powder was attached were measured, and were 2.3 mΩ / □, respectively. Comparative Example A two-component developer was prepared under the same conditions as in Example 1 except that ferrite having an average particle size of 40 μm was used as the carrier powder, and printing was performed 1,000 times under the same conditions as in Example 1. Next, when the electric resistance of the line to which the carrier powder was attached was measured, it was 3.8 mΩ / □.

As described above, when the carrier powder adheres, the electric resistance is considerably deteriorated when the ferrite carrier powder is used, but the electric resistance hardly changes when the carrier powder of the present invention is used. . Example 2 A two-component developer was prepared under the same conditions as in Example 1 except that the nickel particles of the carrier powder were made of an iron-nickel alloy and the nickel content was changed stepwise between 30 and 70% by weight. did.

Next, printing was performed 1,000 times under the same conditions as in Example 1, and the electrical resistance between the normal line where the carrier powder was not attached and the line where the carrier powder was attached was measured. Table 1 shows the results.

[0022]

[Table 1]

From Table 1, it can be seen that when the nickel content in the carrier powder is less than 50% by weight, the electrical resistance of the line is high and the line does not conduct in some cases. It turns out that it shows a low and favorable value.

According to the circuit pattern forming method of the above-described embodiment, nickel powder as a metal for forming a circuit and iron-nickel alloy as an alloy of the metal for forming a circuit are contained in an amount of 50% by weight or more, and the surface is formed of an insulating film. Since the two-component developer containing the carrier powder covered by the above is used, even if the carrier powder adheres to the circuit pattern, it is possible to prevent the electric resistance of the circuit pattern from increasing. That is, a circuit pattern with low electric resistance can be easily formed.

FIG. 3 is a sectional view of a first embodiment according to the wiring board of the present invention. The wiring board 30 includes a ceramic green sheet 31. Then, after the circuit pattern 32 is printed on the ceramic green sheet 31 by electrophotography using the chargeable powder for forming a circuit of the above-described Example 1 and Example 2, about 10% is printed in a reducing atmosphere.
Bake at 00 ° C.

FIG. 4 is a sectional view of a second embodiment according to the wiring board of the present invention. The wiring board 40 includes first to third ceramic green sheets 41a to 41c. Then, the second and third ceramic green sheets 41b,
The circuit patterns 42a and 42b are printed on the surface 41c by electrophotography using the chargeable powder for forming a circuit of the first and second embodiments. Next, after laminating the first to third ceramic green sheets 41a to 41c, applying pressure, and integrally forming the green sheets, about 10% in a reducing atmosphere.
Bake at 00 ° C.

The circuit patterns 42a and 42b on the second and third ceramic green sheets 41b and 41c, respectively.
Are connected by a via hole 43, which is formed by an existing technology. For example, there is a method of press-fitting a conductor into each via hole using a conductor drawing apparatus. In this case, the circuit patterns 42a, 42
If b is formed by electrophotography and then the via hole 43 is formed, the powder may damage the nozzle of the drawing machine.
It is preferable to form the via hole 43 before forming the circuit patterns 42a and 42b.

According to the wiring board of the above-described embodiment, nickel powder as a metal for forming a circuit and iron-nickel alloy as an alloy of the metal for forming a circuit are contained in an amount of 50% by weight or more, and the surface is coated with an insulating film. Using a two-component developer containing separated carrier powder, a circuit pattern is printed on ceramic green sheets by electrophotography, and then the ceramic green sheets are fired to form a wiring board.
A wiring substrate having a circuit pattern with low electric resistance can be easily manufactured.

[0029]

According to the method for forming a circuit pattern of the present invention, a total of 50% by weight of a metal for forming a circuit and one or more of an alloy and a compound of the metal for forming a circuit is used.
Since a two-component developer containing a carrier powder whose surface is covered with an insulating film is used, even if the carrier powder adheres to the circuit pattern, it is possible to prevent an increase in electric resistance of the circuit pattern. it can. That is, a circuit pattern with low electric resistance can be easily formed.

According to the wiring board of the present invention, a metal for forming a circuit, and one or more of alloys and compounds of the metal for forming a circuit are contained in a total of 50% by weight or more, and the surface is formed of an insulating film. Using a two-component developer containing the covered carrier powder, the circuit pattern is printed on the ceramic green sheets by electrophotography, and then the ceramic green sheets are fired to form a wiring board.
A wiring substrate having a circuit pattern with low electric resistance can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electrophotographic system used in an embodiment according to a circuit pattern forming method of the present invention.

FIG. 2 is a cross-sectional view of a two-component developer used in the circuit pattern forming method of FIG.

FIG. 3 is a sectional view of a first embodiment of the wiring board according to the present invention;

FIG. 4 is a sectional view of a second embodiment according to the wiring board of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 12 Photoreceptor 15 Two-component developer 16 Chargeable powder for circuit formation 17, 31, 41a-41c Ceramic green sheet 21 Carrier powder 22 Metal for circuit formation 23 Insulating coating 30, 40 Wiring board 32, 42a, 42b Circuit pattern

Claims (3)

[Claims] 1. A charging process for charging a surface of a photoconductor, an exposure process for forming an electrostatic latent image pattern on the photoconductor, and a two-component developer comprising a carrier powder and a chargeable powder for forming a circuit. Taking out only the chargeable powder for circuit formation, developing the chargeable powder for circuit formation on the latent image pattern by electrostatic force, and charging the chargeable powder for circuit formation on the latent image pattern with the ceramic A method of forming a circuit pattern, comprising: a transfer step of transferring onto a green sheet; and a fixing step of fixing the chargeable powder for forming a circuit transferred onto the ceramic green sheet, wherein the carrier forming the two-component developer is provided. The powder is one of the metal for forming a circuit, and an alloy and a compound of the metal for forming a circuit.
A method for forming a circuit pattern, comprising a total of 50% by weight or more of a kind or two or more kinds and a surface covered with an insulating film. 2. A wiring board, wherein the ceramic green sheet on which the circuit pattern is printed is fired by the circuit pattern forming method according to claim 1. 3. A wiring board, wherein the ceramic green sheets on which the circuit patterns are printed are laminated and fired by the circuit pattern forming method according to claim 1.