JPH1117347A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board having superior heat and moisture resistances and high insulation reliability between conductive circuits formed on a board and an insulation layer and manufacture thereof. SOLUTION: This board has a first conductive circuit, insulation layer and second conductive circuit on a board. The insulation layer is made of a polyimide resin or polyamide-imide resin. It is made by coating the polyimide resin or polyamide-imide resin on the conductive circuit formed on the board, drying and forming the other conductive circuit with a conductive paste thereon, and drying to cure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a method for forming a crossed conductive circuit with a printed wiring board, as described in "Electronic Materials", October 1995, pp. 84-88, issued by the Industrial Research Council, A method of forming a conductive circuit on both sides of a substrate is known. As another method, a method is known in which a through hole is provided in a substrate, and a lead wire is inserted between the through holes to make connection.

However, the method of forming conductive circuits on both sides of a substrate requires use of both sides of the substrate even when the number of crossing conductive circuits is small, so that it takes time and effort to form the conductive circuits, and the manufacturing cost is increased. Is disadvantageously increased. In addition, the method of providing through holes in the board and inserting a lead wire between the through holes to connect
Lead wires must be prepared according to the length between the through holes, which is not sufficient in terms of productivity and price.

Further, it has been attempted to form a conductive circuit crossing one side of the substrate by a printing method via an insulating layer such as an epoxy resin or an acrylic resin. However, the circuit is inferior in moisture resistance and heat resistance, and is not reliable. It was not always enough in point.

[0005]

SUMMARY OF THE INVENTION According to the first aspect of the present invention, there is provided a printed wiring board which is excellent in heat resistance and moisture resistance and has high insulation reliability between a conductive circuit on a substrate and a conductive circuit on an insulating layer. Is what you do. According to a second aspect of the present invention, there is provided, in addition to the first aspect of the invention, a printed wiring board having a high insulation reliability between the conductive circuits and a small resistance change. . The third aspect of the present invention provides an inexpensive printed wiring board by simplifying the steps in addition to the first or second aspect of the present invention. The invention according to claim 4 is excellent in heat resistance and moisture resistance,
Another object of the present invention is to provide a method of manufacturing a printed wiring board having high insulation reliability between a conductive circuit on a substrate and a conductive circuit on an insulating layer. According to a fifth aspect of the present invention, there is provided, in addition to the fourth aspect of the invention, a printed wiring board having a high insulation reliability between conductive circuits and a small resistance change. .

[0006]

SUMMARY OF THE INVENTION The present invention relates to a printed wiring board having a conductive circuit on a substrate, an insulating layer formed thereon, and a conductive circuit formed on the insulating layer. The present invention relates to a printed wiring board which is a layer formed of a polyamideimide resin. The present invention also relates to a printed wiring board in which two or more insulating layers are formed and the size (area) of each layer is reduced gradually each time the insulating layer is formed on the printed wiring board. The present invention also relates to a printed wiring board in which the conductive circuit formed on the insulating layer is a cured product of a conductive paste. Further, the present invention is characterized in that a polyimide resin or a polyamide-imide resin is applied on a conductive circuit formed on a substrate, and after drying, a conductive circuit is formed thereon with a conductive paste, and then dried and cured. To a method for manufacturing a printed wiring board. Further, the present invention relates to a method for manufacturing a printed wiring board, wherein a polyimide resin or a polyamideimide resin is repeatedly applied in the method for manufacturing a printed wiring board, and the application area is sequentially reduced each time the application is performed on the upper portion. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a substrate used in the present invention, it is preferable to use a copper-clad laminate in which a copper foil is adhered to a paper phenol laminate, a glass epoxy laminate or the like. The conductive circuit on the substrate can be formed, for example, by etching the copper foil of the copper-clad laminate by a known method.
The copper foil thickness of this conductive circuit is generally 35 μm or 18 μm.
m.

It is necessary to use a polyimide resin or a polyamide imide resin as an insulating layer formed on the above-mentioned conductive circuit, and other resins or substances are inferior in heat resistance and moisture resistance and easily cause electrolytic corrosion. Disadvantages arise.

The polyimide resin used in the present invention has a structure in which an imide bond obtained by subjecting a tetracarboxylic anhydride and an aromatic diamine to ring-closing dehydration polycondensation is repeated. The polyamideimide resin is a heat-resistant polymer obtained by subjecting a tricarboxylic acid and an aromatic diamine to ring-closing dehydration polycondensation and having a structure in which an imide bond and an amide bond are repeated. The polyimide resin and the polyamide-imide resin are particularly excellent in moisture resistance and heat resistance as the insulating layer in the present invention, and contribute to insulation between the conductive circuit on the substrate and the conductive circuit on the insulating layer.

The insulating layer is formed of two or more layers, and each time the insulating layer is formed on the upper portion, the size (area) of the layer is sequentially reduced to reduce the step at the end portion, or by heating the uncured insulating layer. Preferably, the edge of the insulating layer is thermally softened to reduce the step at the end. In particular, if the step can be reduced to １ ／ or less of the thickness of the insulating layer, a conductive circuit formed on the insulating layer can be formed. This is preferable because unevenness in thickness can be suppressed. The thickness of the insulating layer is 3
The range is preferably from 0 to 60 μm, and more preferably from 40 to 50 μm.

As the conductive paste formed on the insulation, silver paste, mixed paste of silver and copper, copper paste, etc. are used. In particular, it is preferable to use a paste having a specific resistance of 100 mΩ or less, and more preferably a paste of 60 mΩ or less. It is more preferable to use The method for forming a conductive circuit using the conductive paste is not particularly limited, but is preferably formed by a screen printing method in terms of workability, productivity, and the like. The thickness of the conductor circuit is preferably in the range of 5 to 20 μm, more preferably in the range of 10 to 15 μm.

[0012]

Next, the present invention will be described in detail with reference to examples. Example 1 50 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy, trade name: Epicoat 1004) and a resole type phenol resin (manufactured by Hitachi Chemical Co., Ltd., trade name: VP)
50 parts by weight of −11 N, average molecular weight of 450) were mixed in advance with 1 part by weight of 2-ethyl-4-methylimidazole and uniformly mixed to obtain a resin composition. Next, 50 parts by weight of ethyl carbitol and 50 parts by weight of butyl cellosolve were added to the resin composition and uniformly mixed to obtain a resin solution.
Next, silver powder (manufactured by Tokurika Chemical Laboratory, trade name: TCG-1) 8
00 parts by weight was added to the resin solution obtained above, and the mixture was uniformly dispersed with a stirrer to obtain a silver paste.

Thereafter, a copper-clad laminate [Hitachi Chemical Co., Ltd.
And trade name MCL-437F (SRD)], and etching a 35 μm thick copper foil to a width of 1 mm and a length of 3
A conductive circuit of 0 mm was formed. Further, a polyimide resin [manufactured by Central Glass Co., Ltd., trade name PP200]
0] is printed twice, and the thickness is 30 μm and the length × width is 28 mm ×
An insulating layer of 2 mm was formed. After drying this at 100 ° C. for 2 hours, hot air is blown onto the insulating layer at 170 ° C. for 30 minutes for 2 minutes, and the end of the insulating layer is heat-cured to make the upper portion curved, and the step of the insulating layer is set to 20 μm. did.

Next, the silver paste obtained above was screen-printed to a thickness of 15 μm in a direction orthogonal to the conductive circuit of the copper foil.
A conductive circuit having an m and a width of 1 mm and a length of 10 mm was formed and dried and cured at 160 ° C. for 60 minutes to obtain a printed wiring board. The specific resistance of the printed conductive circuit of the obtained printed wiring board was 60 μΩ · cm, and the adhesiveness was also good. The insulation resistance of the conductive circuit formed on the substrate by etching and the conductive circuit formed by printing was 10 ¹⁰ Ω or more.

Further, as a result of performing a thermal shock test on the printed wiring board, the rate of change in specific resistance was 5%. In addition, as a result of performing a wet and medium load test on the printed wiring board, the insulation resistance of the conductive circuit formed by etching on the substrate and that of the conductive circuit formed by printing were 10 ⁸ Ω or more. The cooling test was performed at 125 ° C. for 30 minutes to −65 ° C. for 30 minutes for 100 cycles.
Held for 00 hours.

Comparative Example 1 Instead of the insulating layer of Example 1, a resin solution obtained by adding 15 parts by weight of ethyl carbitol and 15 parts by weight of butyl cellosolve to the resin composition obtained in Example 1 and uniformly mixing was applied three times. A printed wiring board was obtained through the same steps as in Example 1 except that an insulating layer having a thickness of 40 μm was formed, and the drying and curing conditions of the conductive circuit were changed to 160 ° C. for 30 minutes.

The specific resistance of the printed conductive circuit of the obtained printed wiring board was 65 μΩ · cm, and the adhesion was good. The insulation resistance of the conductive circuit formed on the substrate by etching and the conductive circuit formed by printing was 10 ¹⁰ Ω or more. Further, as a result of performing a thermal shock test on the printed wiring board, the rate of change in specific resistance was as large as 10%. The resistance dropped to 10 ⁵ Ω.

Example 2 After a conductive circuit similar to that of Example 1 was formed on the copper-clad laminate used in Example 1, polyimide resin (manufactured by Central Glass Co., Ltd., trade name: PP2000) was formed on the conductive circuit. Print and
An insulating layer having a thickness of 20 μm and a length × width of 28 mm × 2.6 mm was formed. After drying at 100 ° C. for 2 hours, the polyimide resin used above was printed again to form an insulating layer having a thickness of 20 μm and a length × width of 28 mm × 2.0 mm. This was dried and cured at 170 ° C. for 30 minutes.

Next, the silver paste obtained in Example 1 was screen-printed to a thickness of 1 in a direction perpendicular to the conductive circuit of the copper foil.
A conductive circuit having a length of 5 μm, a width of 1 mm and a length of 10 mm was formed, and dried and cured at 160 ° C. for 60 minutes to obtain a printed wiring board.

The specific resistance of the printed conductive circuit of the obtained printed wiring board was 60 μΩ · cm, and the adhesion was good. The insulation resistance of the conductive circuit formed on the substrate by etching and the conductive circuit formed by printing was 10 ¹⁰ Ω or more. Furthermore, as a result of performing a thermal shock test on the printed wiring board, the rate of change in specific resistance was 4%. In addition, as a result of performing a wet and medium load test on the printed wiring board, the insulation resistance of the conductive circuit formed by etching on the substrate and that of the conductive circuit formed by printing were 10 ⁸ Ω or more.

[0021]

According to the first aspect of the present invention, there is provided a printed wiring board which is excellent in heat resistance and moisture resistance and has high insulation reliability between a conductive circuit on a substrate and a conductive circuit on an insulating layer. Claim 2
The invention described in the above is a printed wiring board having a particularly high insulation reliability among the conductive circuits of the invention described in the first aspect and further having a small resistance change in addition to the invention described in the first aspect. Claim 3
The invention described is a printed wiring board which is inexpensive due to simplification of the process in addition to the invention described in claim 1 or 2. Claim 4
According to the described invention, a printed wiring board having excellent heat resistance and moisture resistance and having high insulation reliability between the conductive circuit on the substrate and the conductive circuit on the insulating layer can be manufactured. According to the fifth aspect of the present invention, it is possible to manufacture a printed wiring board having a particularly high insulation reliability between the conductive circuits and a small resistance change in addition to the fourth aspect of the invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Sukekawa, 2525, Mawatari, Hitachinaka City, Ibaraki Prefecture 561 (72) Inventor Kazuhiro Chiba 1-2-2, Minatochuo, Hitachinaka City, Ibaraki Prefecture 1457 37 Ashizaki, Hitachinaka City, Prefecture

Claims (5)

[Claims] 1. A printed wiring board in which a conductive circuit is formed on a substrate, an insulating layer is formed on the conductive circuit, and a conductive circuit is formed on the insulating layer, wherein the insulating layer is formed of a polyimide resin or a polyamideimide resin. Is a printed wiring board. 2. The printed wiring board according to claim 1, wherein two or more insulating layers are formed, and the size (area) of the layers is gradually reduced each time the insulating layer is formed thereon. 3. The printed wiring board according to claim 1, wherein the conductive circuit formed on the insulating layer is a cured product of a conductive paste. 4. A conductive circuit is formed by applying a polyimide resin or a polyamideimide resin onto a conductive circuit formed on a substrate, drying, forming a conductive circuit on the conductive circuit with a conductive paste, and then drying and curing. Manufacturing method of printed wiring board. 5. The method for manufacturing a printed wiring board according to claim 4, wherein the polyimide resin or the polyamideimide resin is repeatedly applied, and the application area is gradually reduced each time the polyimide resin or the polyamideimide resin is applied to the upper portion.