JPH11135943A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board which is small in thickness, light in weight, and high in reliability, and where a connection via can be formed in all inner circuit boards. SOLUTION: Inner circuit boards 3 and 5 and copper foil-clad resin sheets 1 are combined through the intermediary of an insulating resin layer 2 formed on the surface of the inner circuit board are thermocompressed into one piece for the manufacture of a multilayer printed wiring board, wherein a first process where a through-hole 6 required for an inner circuit board is previously formed, a second process where a conductor bump 4 is formed on the surfaces of the inner circuit boards respectively by the use of conductive paste, and a third process where the opposed wiring layers are electrically connected together with the conductor bumps 4 when a thermocompression bonding operation is carried out for the manufacture of the multilayer printed wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin and lightweight multilayer printed wiring board, and more particularly, to a method for connecting wiring layers with a non-penetrating type conductive wiring portion, and for achieving high-density wiring and mounting. The present invention relates to a method for manufacturing a highly reliable printed wiring board with a high yield while reducing man-hours.

[0002]

2. Description of the Related Art As a method of manufacturing a multilayer printed wiring board, there are generally known two methods, a lamination bonding method and a build-up method.

In a method of manufacturing a multilayer printed wiring board by a laminating method, a plurality of inner layer circuit boards on which a desired circuit is formed are prepared by etching copper foil on both sides or one side of a copper clad laminate used as an inner layer board. Then, the copper foil surface treatment is performed, the copper foil is laminated by heating and pressurizing through a prepreg, then a hole is formed in a predetermined position, the entire surface is chemically plated, and then electroplating is performed. Thickness is applied by processing, and electrical connection between wiring layers is performed to obtain a multilayer printed wiring board.

In a method of manufacturing a multilayer printed wiring board by a build-up method, a photosensitive resin is applied on an inner layer circuit instead of a prepreg, a desired portion is removed by selective exposure and development, and an interlayer connection via is formed. Chemical plating is applied to the entire surface, and then thickened by electroplating, and electrical connection of interlayer vias is performed to obtain a multilayer printed wiring board. In a normal build-up substrate, this process is repeated to form a plurality of interlayer vias.

[0005]

However, in the former method, a thin and light-weight and highly reliable multilayer printed wiring board can be manufactured. However, when an ultra-thin prepreg is used, the production of the prepreg is difficult. However, there are problems such as difficulty in stable application of resin and handling during molding and shortage of resin for filling between circuits. further,
Although vias for interlayer connection can be formed, vias for all-layer connection cannot be formed.

In the latter method, if the steps of forming the insulating layer and forming the conductor are repeated many times, it is possible to form all-layer connection vias, but the process is long and the yield is reduced, and the number of steps is increased. It was a factor of cost increase due to passing. Further, the adhesion between the interlayer insulating resin and the plating film is weak, and the reliability tends to be poor.

[0007] Under these circumstances, there has been a demand for the development of a highly reliable multilayer printed wiring board in which all-layer connection vias can be formed.

An object of the present invention is to provide a highly reliable multilayer printed wiring board which is thin and lightweight and in which connection vias for all layers can be formed.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above-mentioned object, and as a result, in the step of heating and pressurizing an inner layer circuit board which has been subjected to through-hole processing in advance to integrally form the same. By forming a conductive bump at a predetermined position on the inner layer circuit and forming a resin layer on the inner layer plate or the inner layer plate arranged opposite to each other, electrical connection between the inner layer circuits facing each other by the formed conductive bump is formed. Have been obtained and the above object has been achieved, thereby completing the present invention.

That is, the present invention relates to a multi-layered structure obtained by combining a plurality of inner-layer circuit boards and a resin sheet with a copper foil via an insulating resin layer formed on the surface of the inner-layer circuit board, and integrally forming the resultant under heat and pressure. In the method for manufacturing a printed wiring board, a step of forming a through hole required in the inner layer circuit board in advance, a step of forming a conductive bump on the surface of the inner layer circuit board using a conductive paste, And a step of electrically connecting the opposing wiring layers by the conductive bumps during molding.

Hereinafter, the present invention will be described in detail.

As the inner circuit board used in the present invention, a circuit is formed in advance on an inner layer board such as an epoxy resin copper-clad laminate or a polyimide resin copper-clad laminate used for multilayer printed wiring, and a necessary through hole is formed. Formed by a conventional method.

In order to insulate between the inner circuits, an insulating resin layer is formed on the surface of the inner circuit board. The insulating resin layer may be formed on both sides or one side of the required inner layer circuit board of the plurality of inner layer circuit boards, or on the required surface. Examples of the insulating resin layer used here include an epoxy resin, a polyimide resin and a modified resin thereof, and these can be used alone or in combination.
Further, it may contain an insulating inorganic or organic filler. The method for forming these insulating resin layers is not particularly limited, and they can be formed by a known method such as a printing method, a dipping method, and a coating method using a roll coater or a curtain coater. The resin forming the insulating layer is preferably the same as the resin applied to the copper foil described later, but may be different.

As the resin sheet with a copper foil used in the present invention, a sheet obtained by applying an insulating resin to a copper foil used for multilayer printed wiring is usually used. Examples of the insulating resin used here include an epoxy resin, a polyimide resin, and their modified resins, and these can be used alone or in combination. Further, it may contain an insulating inorganic or organic filler.

In the present invention, the conductive paste used to form the conductive bumps includes conductive powders such as gold, silver, copper, and solder powder, alloy powders thereof, for example, polycarbonate resin, polysulfone resin, polyester resin, and the like. A conductive composition prepared by mixing with a binder component such as a phenoxy resin, a phenol resin, or a polyimide resin is used.

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a layer structure of an eight-layered multilayer printed wiring board according to the present invention before molding, and FIG.
FIG. 2 is a cross-sectional view of an eight-layer multilayer printed wiring board of the present invention formed with the layer configuration of FIG. 1. In FIG. 1, an inner layer circuit and a through hole 6 are formed in advance on an inner layer circuit board 5 of the three inner layer circuit boards, and an insulating resin layer 2 is formed on both surfaces of the inner layer circuit board by a printing method or the like. . Similarly, a conductor bump 4 is formed on the inner circuit board 3 on which the inner circuit and the through hole 6 are formed in advance.

The inner circuit board 5 on which the resin insulating layer 2 is formed is aligned with the inner circuit board 3 on which the conductor bumps 4 are formed, and the resin sheet 1 with copper foil is further placed on both surfaces of the entire board. If they are formed integrally, electrical connection is made by the conductor bumps, and the multilayer printed wiring board shown in FIG. 2 can be manufactured.

[0019]

In the multilayer printed wiring board of the present invention, a thin and lightweight multilayer board is formed by forming an insulating resin layer on the surface of the inner circuit board, and an interlayer connection is formed on the surface of the inner circuit board processed through holes. For conductive bumps (conductive paste)
Thus, a highly reliable multilayer printed wiring board capable of connecting vias of all layers could be provided.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

EXAMPLE As an inner circuit board for forming a resin insulating layer, an epoxy resin double-sided copper-clad laminate TLC-W- having a copper foil thickness of 18 μm and a board thickness of 0.1 mm was used.
Using 551M (trade name, manufactured by Toshiba Chemical Co., Ltd.), a resin insulating layer having the following resin insulating layer composition was formed to a thickness of 50 μm by a roll coater on an inner layer circuit board on which through-hole processing and circuit formation had been performed. (Resin insulating layer composition) Epoxy resin Epicoat 828 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) 67.4 parts Epicron TSR-601 (trade name, manufactured by Dainippon Ink & Chemicals, Inc.) 67.4 parts Curing agent 2E4MZ 4.4 parts Insulating inorganic substance TiO ₂ 17.3 parts Solvent Methyl cellosolve 233.0 parts Copper foil thickness 18μm, board thickness 0.
1mm epoxy resin double-sided copper-clad laminate TLC-W-55
Using 1M (Toshiba Chemical Co., trade name), two inner layer circuit boards with through-hole processing and circuit formation, both sides printed with silver-based conductive paste CT (Toshiba Chemical Co., trade name) on both sides A conductor bump having a height of 0.1 mm was formed.

As a resin sheet with a copper foil, a resin layer having the following resin composition for a copper foil was formed on one side of an 18 μm copper foil.
It was applied to a thickness of μm to make two resin sheets with copper foil. (Resin composition for copper foil) Epoxy resin Epicron 152 (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) 49.7 parts EPU-6 (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.) 21.3 parts Curing agent DDS 14.2 parts Insulating inorganic material Heidilite H-43M (trade name, manufactured by Showa Denko KK) 17.3 parts Solvent methyl ethyl ketone 133.0 parts Toluene 100.0 parts Then, the inner circuit board on which the resin insulating layer is formed and the inner circuit board on which the conductive bump (conductive paste) is formed are aligned. ,
A resin sheet with a copper foil was superimposed on both sides, and integrally formed by heating and pressing to obtain a 0.6 mm 8-layer plate. When a continuity test was performed on the multilayer printed wiring board of the example manufactured in this way, no defect was found in any connection.

COMPARATIVE EXAMPLE A copper foil thickness of 18 μm and a board thickness of 0.
1mm epoxy resin double-sided copper-clad laminate TLC-W-55
Using 1M (Toshiba Chemical Co., trade name), two inner layer circuit boards with through-hole processing and circuit formation, both sides printed with silver-based conductive paste CT (Toshiba Chemical Co., trade name) on both sides A conductor bump having a height of 0.1 mm was formed.

The thickness of the copper foil is used as the inner layer circuit board on which no conductor bumps are formed.
18μm, 0.1mm thick epoxy resin double-sided copper-clad laminate T
Through-hole processing and circuit formation were performed using LC-W-551M (trade name, manufactured by Toshiba Chemical Corporation).

As a resin sheet with a copper foil, a resin layer having the same resin composition for a copper foil as in the example was formed on one surface of a copper foil of 18 μm.
It was applied to a thickness of 50 μm to make two resin sheets with copper foil. With the bump-free inner layer circuit board inside, two conductor bump-forming inner layer circuit boards are superposed and aligned via a 50 μm-thick glass epoxy prepreg TLP-551 (trade name, manufactured by Toshiba Chemical Corporation). Further, resin sheets with copper foil were superimposed on both sides, and were integrally formed by heating and pressing to obtain a 0.6 mm 8-layer plate. A continuity test was performed on the multilayer printed wiring board of the comparative example manufactured in this manner.
A defect was found in the connection of the points.

[0026]

According to the present invention, there is provided a highly reliable multilayer printed wiring board which is thin and lightweight and in which all-layer connection vias can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a layer configuration of a multilayer printed wiring board according to the present invention before molding, in a separated manner.

FIG. 2 is a cross-sectional view of an eight-layer multilayer printed wiring board according to the present invention in which the one having the layer configuration of FIG. 1 is molded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resin sheet with copper foil 2 Resin insulating layer 3, 5 Inner layer circuit board 4 Conductor bump 6 Through hole

Claims (1)

[Claims] 1. A multilayer printed wiring board formed by combining a plurality of inner-layer circuit boards and a resin sheet with a copper foil via an insulating resin layer formed on the surface of the inner-layer circuit board, and integrally forming the resultant under heat and pressure. In the manufacturing method, a step of forming in advance a through hole necessary for the inner layer circuit board, a step of forming a conductive bump on the surface of the inner layer circuit board using a conductive paste, And a step of electrically connecting the opposing wiring layers by the conductive bumps.