JPH07226575A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To ensure adhesion between plated conductor and a board by a method wherein a metal foil is laminated and pressed on an insulating board material via a roughened surface, the metal foil is etched and eliminated from the insulating board material, and a circuit is formed by applying the wiring work containing electroless plating to a replica surface of the insulating board material. CONSTITUTION:A copper foil 1 which is composed of one or more kinds of copper and the like and has a roughened surface is laminated and pressed on a glass cloth base material epoxy prepreg 2 via the roughened surface. After the copper foil is etched and eliminated from the glass cloth base material epoxy prepreg 2, the wiring work containing electroless CL plating 5 is applied to a replica surface of the glass cloth base material epoxy prepreg 2, and a circuit is formed. Thereby sufficient adhesion between a plating film and the insulating board can be obtained.

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 printed wiring board.

[0002]

2. Description of the Related Art One of the methods for manufacturing a printed wiring board is a method of forming a conductor pattern by using an insulating substrate without a copper foil as a starting material and plating only a necessary portion on the substrate. In this method, the adhesion between the insulating substrate and the conductive metal formed by electroless plating is extremely important for various characteristics of the printed wiring board.

A general method for ensuring the adhesion between the insulating substrate and the plated metal is to provide an adhesive layer of ABS, rubber or the like on the substrate surface and treat it with a chemical roughening solution to remove the adhesive. The surface is provided with an uneven shape, and the anchor effect of this roughened surface is utilized.

In addition to this, a method of roughening without using an adhesive has also been proposed. In Japanese Patent Laid-Open Nos. 62-98696 and 3-161992, a metal foil having a rough surface is insulated. A method is disclosed in which a roughened surface transferred to the surface of a substrate is exposed by melting and removing a metal foil on an insulating substrate by laminating and pressing with a substrate, and a circuit is formed on the roughened surface.

[0005]

By the way, among the above-mentioned conventional methods, the method of roughening an adhesive requires the use of a roughening liquid, and most of the roughening liquids that can be used include an oxidizing agent. However, it is highly toxic, has a bad working environment, and requires special waste liquid treatment. In addition, such an adhesive that can be roughened generally has low electric insulation, and usually has low humidity resistance and high temperature insulation. In addition, since the heat resistance of the adhesive is insufficient, there has been a problem that the adhesiveness at high temperature is significantly reduced.

On the other hand, the methods disclosed in JP-A-62-98696 and JP-A-3-161992 do not use an adhesive layer and transfer the roughened shape of the metal foil to roughen the surface. As a result, it is possible to eliminate the deterioration of the characteristics caused by the adhesive and the handling risk and the deterioration of the environment due to the roughening of the adhesive, but in either case, a conductor circuit including a large solid pattern is formed. In addition, the adhesion between the conductive metal and the insulating substrate by electroless plating is not always sufficient, such as when blistering occurs partially when forming a thick conductive circuit of 0.05 mm or more. There wasn't.

It is an object of the present invention to provide a method for manufacturing a printed wiring board having excellent adhesion between the plated conductor and the substrate.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention add an additive to roughen a substrate surface by transferring a rough surface shape of a metal foil without using an adhesive and to form a circuit on the rough surface of the substrate. In the method of manufacturing a printed wiring board by the method, the inventors have earnestly studied a method for ensuring sufficient adhesion between the plated conductor and the substrate. As a result, the adhesion between the plated conductor and the substrate is
It largely depends on the surface roughness of the metal foil that transfers the rough surface shape,
The inventors have found that it is closely related to the parameter in the lateral direction as well as the parameter in the height direction of the unevenness of the rough surface of the metal foil, and completed the present invention.

JP-A-62-98696 and JP-A-3-161992 disclose an additive method in which a roughened surface shape of a metal foil is transferred to roughen the surface of the substrate and a circuit is formed on the roughened surface of the substrate. Disclosed is a method for manufacturing a printed wiring board according to claim 1, and applicable ten-point average roughness (Rz) of a rough surface of a metal foil.
And the height of unevenness.

However, in order to secure a sufficient adhesion between the plated conductor and the substrate, it cannot be said that the definition by the parameters in the height direction of the unevenness of the metal foil for transferring the rough surface shape is sufficient. It turns out that lateral parameters also need to be added. For example, the cross-sectional curves of the two surface models shown in FIG. 1 have exactly the same value if they are expressed by the ten-point average roughness (Rz) and the maximum height (Rmax), but the characteristics of the substrate surface to which the shape is transferred are It is very different, and the adhesion when plated is also different. In order to distinguish such two surfaces, it is appropriate to display the parameters in the lateral direction as well as in the uneven direction. However, the surface roughness of the metal foil for transferring the rough surface shape is not limited to the parameter of the method of height of unevenness. A technique for defining a lateral parameter has not been disclosed or proposed in the related art. In addition,
At present, the surface roughness display method adopted in Japanese Industrial Standard JIS B0601 “Definition and Display of Surface Roughness” also includes three types of parameters (center line average roughness: Ra 10 Point average roughness: Rz, maximum height: Rm
ax, centerline average roughness: Ra) only.

The method for producing a printed wiring board according to the present invention comprises laminating and pressing a metal foil having a roughened surface, which is made of at least one kind of metal, with an insulating substrate material through the roughened surface, and then pressing. After removing the metal foil from the insulating substrate material by a method including etching, perform wiring processing including electroless plating on the replica surface of the insulating substrate material to which the roughened surface shape of the metal foil is transferred to form a circuit. Is characterized by.

The roughened surface of this metal foil has a standard length of 2.5 m.
It is preferable that the total number of peaks per m is 120 or more, and the height of the peaks of 2 μm or more is randomly surrounded by at least 100 or more. The main terms used here have the following meanings. Section curve: When the roughened surface is cut by a plane perpendicular to the roughened surface,
Contours appearing at the cut ridge: Convex portion in cross-section curve Valley: Recessed portion in cross-section curve Peak of peak: Bottom of peak: Bottom of valley Average line: Geometrical shape of roughened surface in extracted portion of cross-section curve A straight line or a curve with a line that is set so that the sum of squares of the deviation from that line to the cross-section curve is minimized. Mountain height: Two peaks and valley bottoms that are adjacent to each other are parallel to the average line.
When sandwiched by straight lines, the value obtained by measuring the distance between these two straight lines on the unevenness of the cross-section curve Reference length: Length of the part where a certain length of the cross-section curve is extracted

The metal foil used in the present invention is not particularly limited in its type and may have a desired roughened surface. In addition to a foil formed of a single metal, a composite foil composed of two or more kinds of metal layers, or a metal foil formed on a support such as an organic film or a SUS plate may be used. The thickness of the metal foil is not particularly limited, but if the support is not used, it is preferably 12 to 70 μm in terms of handling and cost.

The height of the peaks of the rough surface of the metal foil is 20 μm or less, preferably about 2 to 10 μm. It is more preferable that all the peaks forming the rough surface are uniform in the range of 3 to 7 μm. . In addition, the number of peaks is 120 or more per standard length of 2.5 mm in the sectional curve, and the height is 2
It suffices that 100 or more mountains of μm or more are randomly included. Note that defining the number of peaks per reference length as a parameter in the lateral direction of the surface roughness is synonymous with defining the average interval of the unevenness in the cross-section curve, and in this case, the average of the unevenness is It can be said that the distance is about 20 μm or less.

The method for roughening the surface of the metal foil is electrolytic deposition (electroplating). When forming a rough surface with copper, a copper sulfate bath or the like can be used, and when forming a rough surface with nickel, a Watt bath or the like can be used.

Such a metal foil has a special rough surface shape, and the surface morphology of the copper foil is different from that of the copper foil used for the copper-clad laminate because of the difference in purpose of use and required characteristics. It is not appropriate to apply copper foil for rough surface transfer. In general, copper foil for copper-clad laminates often has a low-profile rough surface for fine line formation and high-speed transmission of high-frequency signals. Although there is no problem with the number, the height of the mountain is small and it is insufficient. Further, there are some copper foils for copper-clad laminates that satisfy the regulation of the height of peaks, but most of them have a small number of peaks, which is also unsuitable for transferring rough surface shapes.

The insulating substrate material laminated with the roughened metal foil includes epoxy, modified polyimide, polyimide,
Thermosetting resins such as phenol, which are used for general copper-clad laminates, and thermoplastic resins such as polyethylene, Teflon, polyether sulfone, and polyetherimide are used. These can be used as a sheet in which a base material such as paper or glass cloth is impregnated with varnish or a film containing no base material. In addition, a metal foil rough surface coated with a varnish-like resin and dried can also be used.

After laminating the metal foil with the insulating substrate material, an etching solution is used to remove the metal foil from the insulating substrate material. For example, when etching a copper foil (thickness: 35 μm), this etching solution includes ammonium persulfate, an aqueous solution of copper chloride and hydrochloric acid, and an aqueous solution of iron chloride and hydrochloric acid, which are generally used as an etching solution for printed wiring boards. In addition to the aqueous solution, an alkaline aqueous solution mainly containing a copper ammonium complex can be used. The processing conditions of the above etching solution are a temperature of 30 to 80 ° C. and a dipping time of 5 to 30.
It's a minute. Instead of immersion, the treatment liquid may be sprayed. It is desirable to mechanically polish the metal foil surface before etching.

The catalyst treatment prior to electroless plating may use a palladium catalyst or the like. A catalyst-containing material may be used instead of the catalyst treatment. As the electroless plating, electroless copper plating, electroless nickel plating, or the like is used. Copper conductors are generally used as conductors for printed wiring boards. When the conductor is formed only by electroless copper plating, it is preferable to use an electroless copper plating solution for thickening. When using electroplating together, electroless plating is performed after electroless plating after the above catalyst treatment.

[0020]

As described above, according to the method of the present invention, after the metal foil and the resin layer are laminated, the concavo-convex shape of the metal foil is transferred to the surface of the resin substrate from which the metal foil has been removed, so that an effective anchor formation is achieved. Even without providing an adhesive layer, it is possible to secure sufficient adhesion between the electroless plating and the resin substrate, and it is possible to form a conductive pattern having a strong peeling strength without plating swelling.

[0021]

Example: A copper raw material is dissolved in a sulfuric acid solution, and lead is used as an anode.
A copper foil is electrochemically electrodeposited on the drum using the rotating drum facing it as a cathode, and the copper foil is continuously peeled off from the rotating drum, and a roll-shaped raw foil (raw foil) having a thickness of about 30 μm is formed.
Was produced. Then, using a copper sulfate plating bath, burn plating was performed on the raw foil to deposit the seed humps by electrodeposition, and then smooth plating was performed to grow the seed humps and roughen the surface. Next, GE in which the rough surface of the copper foil is a glass cloth-based epoxy prepreg
-671YX ₂ L (manufactured by Hitachi Chemical Co., Ltd .; trade name)
It was configured so as to come into contact with and was laminated and pressed. The lamination conditions at this time are as follows: molding pressure 40 kg / cm ² , temperature 170 ° C.,
The time is 90 minutes. Next, after making a hole with an NC drill, the copper foil is completely removed using a cupric chloride etching solution, and the palladium catalyst is immersed in a treatment solution containing palladium chloride to start electroless copper plating. Was granted. Next, using a dry film photoresist, Fotec SR-3000EB-35 (manufactured by Hitachi Chemical Co., Ltd .; trade name), lamination, exposure, and development were sequentially performed to form a plating resist. Next, electroless copper plating was performed under the following conditions to produce a double-sided plate. CuSO ₄ .5H ₂ O: 1 g / l EDTA.4Na: 40 g / l 37% CH ₂ O: 3 ml / l Plating solution additive: Little pH: 12.4 Plating solution temperature: 70 ° C. Plating film thickness: 35 μm

Comparative Example 1 The raw foil used in Example 1 was sequentially subjected to burn plating and smooth plating while changing the additives in the copper sulfate plating bath used in Example 1 to deposit copper on the rough surface. Was made. Next, in the same manner as in Example 1, lamination, drilling, copper foil etching, palladium catalyst application, plating resist formation, and electroless copper plating were sequentially performed to produce a double-sided plate.

Comparative Example 2 Using the copper sulfate plating bath used in Example 1, the raw foil used in Example 1 was sequentially subjected to burn plating and smooth plating under plating conditions different from those of Example 1, and copper was electroplated. It was deposited and deposited and roughened. Next, in the same manner as in Example 1, lamination, drilling, copper foil etching, palladium catalyst application, plating resist formation, and electroless copper plating were sequentially performed to produce a double-sided plate.

Comparative Example 3 Acrylonitrile butadiene rubber, alkylphenol resin, epoxy resin, silica and zirconium silicate were dissolved in a mixed solvent of cellosolve acetate and methyl ethyl ketone using a kneader and a stirrer to prepare an adhesive solution having a solid content of 25%. Then, this was dip-coated on the surface of a glass cloth-based epoxy substrate E-67 (manufactured by Hitachi Chemical Co., Ltd .; trade name) so that the thickness after drying would be about 25 μm.
A substrate with an adhesive was produced by heating and curing at 0 ° C. for 60 minutes. After drilling by the same method as in Example 1, chromic acid mixed acid (chromic acid: 55% 1,
It was immersed in sulfuric acid: 300 ml / l) at 40 ° C. for 15 minutes, washed with water and neutralized. Then, a palladium catalyst was applied, a plating resist was formed, and electroless copper plating was sequentially performed in the same manner as in Example 1 to produce a double-sided plate.

In order to investigate the surface roughness of the copper foil used for transferring the rough surface shape, the ten-point average roughness (Rz) was measured using a fine shape measuring instrument ET-30HK (manufactured by Kosaka Laboratory Ltd.). Then, using the obtained chart as a sectional curve, the height and number of peaks per standard length of 2.5 mm were counted. The specifications of the detector (stylus) are a tip curvature radius: 0.5 μm and an apex angle: 90 degrees. In counting, only peaks having a height of 1 μm or more were targeted, and those having a height smaller than that were removed. In addition, when the elevation of the valley bottom adjacent to the summit is different, and the height of the mountain changes depending on how to choose the valley bottom, the one with the higher height was selected. The results are shown in Table 1.

Next, in order to evaluate the adhesion between the substrate and the plating film, first, the appearance was observed for the presence or absence of plating blisters, and then the peeling strength of the plating film was measured at 25 ° C. and 150 ° C. The peeling width of the plating film was 10 mm, the peeling angle was 90 degrees, and the peeling speed was 50 mm / min. The results are shown in Table 2.

The copper foil for rough surface transfer used in Comparative Example 1 is R
Although the z value is larger than that of the example and the number of peaks having a height of 6 μm or more is larger than that of the example, the total number of peaks is smaller than that of the example. The copper foil used in Comparative Example 2 has a larger total number of peaks than those of the Examples, but many of them have a small height, and the number of peaks having a height of 2 μm or more is smaller than that of the Examples. In addition, in Comparative Examples 1 and 2, since the adhesion between the substrate and the plating film was insufficient, swelling occurred in the electroless copper plating.

From these results, in the method for manufacturing a printed wiring board according to the present invention, the adhesion between the plating film and the substrate is sufficiently secured, and the adhesive layer of Comparative Example 3 is provided to roughen it. It can be seen that the decrease in the adhesive strength at high temperature is less than that of

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

As described above, according to the present invention, since the surface is roughened without using the adhesive, the deterioration of the characteristics caused by the adhesive and the risk of handling due to the roughening of the adhesive and the environment. It is possible to manufacture a printed wiring board which eliminates the above deterioration, has excellent heat resistance and electric insulation properties, and has sufficient adhesion between the plated film and the insulating substrate.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a cross section of a rough surface of a metal foil for explaining the operation of the present invention.

2A is a cross-sectional photograph of the surface of a metal foil for rough surface transfer showing an embodiment of the present invention, FIG. 2B is a cross-sectional photograph of the surface of a metal foil for rough surface transfer showing a conventional example, and FIG. It is a cross-sectional photograph of the metal foil surface for rough surface transfer which shows another prior art example.

FIG. 3A is a diagram showing a relationship between surface position and roughness showing an embodiment of the present invention, FIG. 3B is a diagram showing a relationship between surface position and roughness showing a conventional example, and FIG. 10] is a diagram showing the relationship between the surface position and the roughness, showing another conventional example.

4 (a) to 4 (f) are cross-sectional views of respective steps for explaining one embodiment of the present invention.

5A to 5E are cross-sectional views of respective steps for explaining a conventional example.

[Explanation of symbols]

 1 Copper Foil 2 Prepreg 3 Through Hole 4 Plating Resist 5 Electroless Copper Plating 6 Resin Substrate 7 Adhesive

Claims (3)

[Claims] 1. A metal foil having a roughened surface made of at least one kind of metal is laminated and pressed with an insulating substrate material through the roughened surface, and then the metal foil is etched from the insulating substrate material. After the removal by a method including, a wiring process including electroless plating is performed on the replica surface of the insulating substrate material on which the roughened surface shape of the metal foil is transferred, and a circuit is formed to produce a printed wiring board. Law. 2. The roughened surface of the metal foil has a total of 120 or more peaks per standard length of 2.5 mm, of which the peak height is 2
The method for manufacturing a printed wiring board according to claim 1, wherein at least 100 or more having a size of μm or more are randomly surrounded. 3. The method for manufacturing a printed wiring board according to claim 1, wherein the roughening method of the metal foil is electrolytic deposition.