JPH1187912A - Manufacture of double-sided wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a double-sided wiring board which is capable of not only easily controlling the thickness of the wiring board but also securing mechanical strength. SOLUTION: This manufacture is provided with a process for making a through-hole 4 in a thickness direction at a prescribed part of an insulating core sheet 1, the process for providing a conductive projection 5 on one main surface of conductor foils 2 and 2' corresponding to the through-hole 4, the process for making the conductive projections 5 face each other and positioning, laminating and arranging the conductor foils 2 and 2' on both sides of the insulating core sheet 1 via an insulating sheet layer 3, the process for pressing and integrating the laminated body and forming a double-sided conductor foiled laminated board for which the tip parts of the corresponding conductive projections 5 are electrically connected with each other inside the through-hole 4 of the insulating core board 1 and the process for patterning the wiring of the double-sided conductor foils 2 and 2'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a double-sided wiring board, and more particularly, to a method for manufacturing a double-sided wiring board having excellent strength and dimensional accuracy.

[0002]

2. Description of the Related Art In the construction of a double-sided wiring board, electrical connection between wiring pattern layers integrally provided on both main surfaces via an insulating layer (interlayer insulating layer) is generally performed as follows. A hole penetrating in the thickness direction is formed in the insulator layer, and a conductive plating layer is provided on the inner wall surface of the hole, so that a so-called through-hole connection method is used. Further, in order to simplify the through-hole connection process, attempts have been made to fill a through-hole formed in an insulator layer with a conductive paste. That is, instead of forming a hole that penetrates (penetrates) the interlayer insulating layer at an electrical connection point between the wiring pattern layers and grows a conductive plating layer on the inner wall surface of the hole, a through hole connection is formed. ,
It is known that a conductive paste is filled and buried in a hole to form a required through-hole connection.

For example, a double-sided wiring board is generally manufactured by the following procedure. First, an electrolytic copper foil provided with conductive bumps (conductive protrusions) at predetermined positions in advance on both main surfaces of a prepreg layer (glass-epoxy resin type) in which an epoxy resin is impregnated and adhered to a glass cloth. ,
Overlay and arrange with electrolytic copper foil without conductive bumps,
Heat and pressure molding to produce double-sided copper-clad laminates.

The thickness of the prepreg layer and the thickness of the electrolytic copper foil are selected and set in accordance with the design specifications of the double-sided wiring board (thickness of the wiring board, wiring pattern width and wiring density).
Further, in the process of the heating and pressure molding, the resin in the glass-epoxy resin-based prepreg layer forming the interlayer insulator layer adopts a softened molten state, so that the tip of the conductive bump penetrates the prepreg layer, An electrical connection is formed in contact with the facing electrolytic copper foil surface.

[0005] Thereafter, the copper foil surface of the double-sided copper-clad laminate is subjected to photo-etching and wiring patterning to produce a double-sided wiring board having a desired wiring pattern.

On the other hand, with the recent tendency to be light and thin,
Various types of wiring boards, including double-sided wiring boards, are also required to be lighter and thinner, and thinner wiring boards, more multilayer wiring, finer wiring, higher density wiring, and the like are being pursued.

[0007]

However, in the case of a double-sided copper-clad board in which through holes are connected between wiring pattern layers by penetrating the conductive bumps through the interlayer insulating layer, the following problems are recognized. For example, thickness
Even if the thickness of the glass / epoxy resin prepreg layer and the electrolytic copper foil are selected and set at the specification of about 0.2mm, the double-sided wiring manufactured by the variation of the material (quality) and the manufacturing process / operation etc. It is difficult to always control the thickness of the plate within an allowable range (for example, ± 10%), and there is a concern that the production yield may be reduced.

Further, in addition to the above-mentioned thickness variation, the mechanical strength of the double-sided wiring board is inferior and damage is liable to occur, or warpage that makes positioning and mounting of electronic components difficult is caused. There's a problem. In other words, mounting and assembling work is non-mass-produced as a double-sided wiring board that is light, thin, short, and can be used as a highly reliable mounting circuit device.
There are problems such as complication, and the production method cannot be said to be a satisfactory method in practical use.

The present invention has been made in view of the above circumstances, and provides a method of manufacturing a double-sided wiring board capable of ensuring not only easy control of the thickness of the wiring board but also mechanical strength. For the purpose of providing.

[0010]

According to a first aspect of the present invention, there is provided a method of forming a hole penetrating a predetermined portion of an insulating core plate in a thickness direction, and a step of forming a conductive foil corresponding to the formed hole. A step of providing conductive protrusions on one principal surface; a step of positioning, stacking and arranging conductive foils on both surfaces of the insulating core plate with insulating sheet layers interposed therebetween and with the conductive protrusions facing each other; Forming a double-sided conductor foil-clad laminate in which the tips of the corresponding conductive protrusions are electrically connected in the perforated holes of the insulating core plate, and And a wiring patterning process.

According to a second aspect of the present invention, in the method for manufacturing a double-sided wiring board according to the first aspect, the conductive projections are provided by screen printing and drying of a conductive paste.

According to a third aspect of the present invention, in the method for manufacturing a double-sided wiring board according to the first or second aspect, the insulating sheet layer is a glass / epoxy resin pre-flag.

In the present invention, the insulating core plate contributes to the control of the thickness and the mechanical strength of the double-sided wiring board to be manufactured, and generally has a thickness of about 0.1 to 1.0 mm. Examples thereof include insulators such as glass / epoxy resin, polyimide resin, bismaleimide triazine resin, phenol resin, polyester resin, melamine resin, and polycarbonate resin sheets (or films or thin plates). The through-holes are formed in the insulating core plate by, for example, drilling or punching.

The conductor foil may have a thickness of, for example, 12
Electrolyzed copper foil and aluminum foil having a thickness of about 35 μm or the like can be mentioned. The material and thickness of the foil are appropriately selected depending on the use and thickness of the double-sided wiring board to be manufactured. The conductive protrusions are formed on one main surface of the conductive foil by screen printing of a conductive resin paste using a metal mask, for example, and by appropriately repeating drying after printing to obtain predetermined dimensions (bottom diameter, height). ) Can be formed in a conical shape or a pyramid shape. The size and shape of the conductive protrusions are not limited to the above-described shapes, but are desirably sufficient to sufficiently fill the through holes of the opposing core substrate.

The conductive resin paste is prepared by mixing a conductive powder such as silver, gold, copper and solder powder, an alloy powder or a composite (mixed) metal powder thereof, and a resin binder component. Pastes.

As the resin binder component, for example, thermoplastic resins such as polycarbonate resin, polysulfone resin, polyester resin and phenoxy resin, and thermosetting resins such as phenol resin, polyimide resin and epoxy resin are generally used. No. In addition, methyl methacrylate, diethyl methyl methacrylate,
Trimethylolpropane triacrylate, diethylene glycol diethyl acrylate, methyl acrylate,
UV-curable resins such as acrylates such as ethyl acrylate, diethylene glycol ethoxylate acrylate, and acrylates of ε-caprolactone-modified dipentaerythritol, and methacrylates, and electron beam-curable resins.

Further, as the insulating sheet disposed on the surface of the insulating core plate, for example, a thermoplastic resin film (sheet) may be mentioned, and its thickness is generally 30 to 100 μm.
The degree is preferred. Here, examples of the thermoplastic resin sheet include sheets such as a polycarbonate resin, a polysulfone resin, a thermoplastic polyimide resin, a tetrafluoroethylene resin, a hexafluoropropylene resin, and a polyetheretherketone resin. The thermosetting resin (prepreg) sheet kept in a state before curing includes epoxy resin, bismaleimide triazine resin, polyimide resin, phenol resin, polyester resin, melamine resin, or butadiene rubber, butyl rubber, natural rubber, neoprene Examples include sheets of raw rubber such as rubber and silicone rubber. These synthetic resins are:
The sheet may be used alone, or may contain an insulating inorganic or organic filler, and may be a sheet formed by combining with a reinforcing material such as glass cloth or mat, organic synthetic fiber cloth or mat, or paper.

According to the first to third aspects of the present invention, the wiring patterns connected between the layers are formed on both surfaces of the insulating core plate. In other words, since an insulating substrate whose thickness is controlled and specified in advance and which guarantees a predetermined mechanical strength is used as a core, and a wiring pattern is formed on the surface of the core substrate, the thickness is approximately constant and appropriate. A double-sided wiring board having mechanical strength is manufactured with high yield. In addition, the interlayer connection of the double-sided wiring pattern is performed in the step of pressure integration, in which the insulating sheet is inserted, and the front end of the conductive protrusion which faces / inserts into the through hole of the core substrate and the inside of the through hole are filled. On the other hand,
Since the insulation and separation of adjacent interlayer connections are also made properly,
A highly reliable interlayer connection is formed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. 1, 2 and 3. FIG.

1 to 3 are cross-sectional views schematically showing steps of manufacturing a double-sided wiring board according to an embodiment of the present invention. First, a cured substrate (core substrate) 1 of a glass epoxy resin having a thickness of about 0.3 mm, electrolytic copper foils 2 and 2 ′ having a thickness of 18 μm, and a diameter of
0.5 mm thick metal screen plate formed by drilling 0.5 mm holes at predetermined positions, silver powder-phenol resin conductive paste, and glass epoxy resin prepreg (uncured) having a thickness of about 100 μm 3 Were prepared respectively.

Next, a through hole 4 having a diameter of about 0.6 mm is formed at a predetermined position (location) of the core substrate 1 by drilling, and a metal screen is formed on one main surface of the electrolytic copper foils 2 and 2 ′. The plates were positioned and arranged, and a silver powder-phenol resin-based conductive paste was printed at a position facing the through hole 4. 165 Printed conductive paste
After drying at ℃ for 15 minutes, printing and drying were repeated four times at the same position using the same metal screen plate, and then subjected to a heating effect treatment to form a cone (bottom diameter 0.5 mm,
Conductive bumps 5 each having a height of 0.5 mm) were provided.

Thereafter, as shown in cross section in FIG. 1, a core substrate 1 provided with the through holes 4, electrolytic copper foils 2, 2 ′ provided with conductive bumps 5 at predetermined positions on one main surface, and a glass epoxy resin The system prepreg 3 was positioned and laminated and arranged. Next, the laminate was set on a heating press via a contact plate, and heated at 175 ° C. and pressurized at a pressure of 60 kg / cm ² for 1 hour to cure the glass / epoxy resin prepreg 3. At the same time, the front ends of the conductive bumps 5 penetrating the glass-epoxy resin-based prepreg 3 are pressed into the through holes 4 of the core substrate 1 facing each other so as to be in contact with and connected to each other. , 2 'are electrically connected to each other.

FIGS. 2 and 3 show the state of the conductive bumps 5 in the above-mentioned pressure molding step. First, the tip of the conductive bumps 5 is press-fitted with a glass-epoxy resin prepreg 3. I do. Subsequently, as shown in FIG. 2, the tips of the conductive bumps 5 face each other in the through holes 4 of the core substrate 1, and the tips of the conductive bumps 5 contact and connect with each other. As shown, the through holes 4 in the core substrate 1
While filling the inside, an interlayer connection portion 5 'is formed.

Next, a required etching pattern is printed by screen printing on the copper foils 2 and 2 'of the double-sided copper foil-clad laminate, and the unnecessary copper foil is etched using an aqueous solution of ferric chloride as an etching solution. After the removal, the etching resist was removed to obtain a double-sided wiring board having a required through-hole connection portion 5 '.

In the wiring board manufactured as described above, the connection resistance of the double-sided wiring pattern layer is, for example, 2.1Ω, and this value takes into account the copper foil pattern resistance (1 mΩ of copper foil pattern resistance per bump). Then, the average of the through-hole connection resistance was 1 mΩ, and both the via connection resistance and the copper foil pattern resistance had little variation.

Further, about ten double-sided wiring boards manufactured by the above-mentioned manufacturing means were tested and evaluated, and the thickness was 0.51 to 0.56 mm, which was ±% of the design / specification value. It was confirmed that the thickness could be easily controlled within the range. That is, each of these double-sided wiring boards depends on the thickness of the fixed core substrate 1.
Not only is the final thickness easily controlled, but also the strength and non-deformability of the core substrate 1 itself are promoted to improve mechanical strength and prevent warpage.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. For example, the interlayer insulator layer
Instead of the glass-epoxy resin prepreg, a thermoplastic resin may be used, and the conductive protrusions may be formed of a conductive composition other than silver powder-phenol resin.

[0028]

According to the first to third aspects of the present invention, an insulating substrate whose thickness is controlled and defined in advance and which guarantees a predetermined mechanical strength is used as a core. A wiring pattern for through-hole connection is formed. That is, since a core substrate having a substantially constant thickness and a suitable mechanical strength is used as an inner layer, a double-sided wiring board having a controlled thickness and good mechanical strength can be provided with good yield. Moreover, the through-hole connection between the double-sided wiring patterns
Providing a double-sided wiring board with highly reliable through-hole connection, which is performed by contacting the tip of the conductive protrusion and filling in the through-hole and easily securing insulation and separation of adjacent through-hole connections it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a state of lamination and arrangement of respective materials in a method for manufacturing a double-sided wiring board.

FIG. 2 is a cross-sectional view schematically showing a state in which opposing conductive protrusion tips are press-fitted into through holes of a core substrate in the method for manufacturing a double-sided wiring board.

FIG. 3 is a cross-sectional view schematically showing a state in which a tip end of a conductive protrusion facing and filled with a through hole of a core substrate in a method of manufacturing a double-sided wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Core board 2, 2 '... Electrolytic copper foil 3 ... Insulator layer (glass epoxy resin prepreg) 4 ... Through-hole 5 ... Conductive protrusion (bump) 5' ... Through-hole connection part

Claims (3)

[Claims] 1. A step of forming a hole penetrating in a thickness direction at a predetermined position of an insulating core plate; and a step of forming a conductive projection on one main surface of a conductive foil corresponding to the hole. Positioning and laminating and arranging the conductor foil with insulating sheet layers interposed on both surfaces of the insulating core plate and facing the conductive protrusions; and press-integrating the laminate to form the corresponding conductive protrusions Forming a double-sided conductor foil-clad laminate in which the leading ends of the double-sided conductor foils are electrically connected in the perforations of the insulating core plate; and wiring-patterning the double-sided conductor foil. Manufacturing method of a double-sided wiring board. 2. The method for manufacturing a double-sided wiring board according to claim 1, wherein the conductive projections are provided by screen printing and drying of a conductive paste. 3. The method for manufacturing a double-sided wiring board according to claim 1, wherein the insulating sheet layer is a glass-epoxy resin-based pre-leg.