JPH05167248A - Method of manufacturing printed wiring board - Google Patents

Abstract

PURPOSE:To prevent the generation of a negative etchback in an internal circuit, which is attendant on the removal of an oxidation treatment copper foil, and to improve the reliability of an interlayer connection in a method of forming a wiring, in which the surface of an insulating substrate roughened by transfer of the oxidation treatment copper foil. CONSTITUTION:A copper oxide film 2 is formed on the surface of a copper-foil 1, the copper foil 1 is laminated along with an internal layer circuit in such a way that this surface formed with the copper oxide film 2 and an insulative organic substrate 3 is in contact with each other and after perforation is performed, a metallic copper film and the copper oxide film are dissolved and removed by a method comprising an electrolytic etching and after that, a wiring is formed by a technique comprising an electroless plating.

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 In recent years, electronic devices have become more and more demanded to be smaller, lighter and more multifunctional, and accordingly, demands for higher density and higher reliability in printed wiring boards are increasing. The subtractive method is the mainstream for printed wiring boards at present, in order to deal with such problems.
With this manufacturing method, it is difficult to make the wire fine and to make it into a small-diameter through hole, and there is a limit to sufficiently cope with high density. On the other hand, an additive method has been proposed in which a conductive metal is plated to a desired thickness by electroless plating of an insulating substrate to form a wiring pattern.

Since the additive method has good throwing power of the electroless plating for through-holes, uniform plating can be obtained even in the through-holes, which has a higher aspect ratio than the subtractive method. Further, the pattern formability is affected by the resist resolution and etching accuracy in the subtractive method, but is high in the additive method because it depends only on the resist resolution. Therefore, it is theoretically suitable for manufacturing a fine pattern, high aspect ratio high density wiring board. In the production of a printed wiring board by such an additive method, the adhesion between the insulating substrate and the conductive metal formed by electroless plating is extremely important for the various characteristics of the printed wiring board. A typical method for securing the adhesion between the insulating substrate and the plated metal is A
By providing an adhesive layer of BS thread, rubber or the like on the substrate surface and treating it with a chemical roughening liquid, fine irregularities on the surface of the adhesive are given, and the anchor effect of this roughened surface is utilized. It is a thing.

However, in this method, since the adhesive layer is roughened, a roughening liquid must be used. Most of the roughening liquids that can be used contain an oxidizing agent and are highly toxic.
Therefore, the working environment is bad and special waste liquid treatment is required. In addition, such an adhesive that can be roughened generally has poor electrical insulation properties, and has poor moisture-resistant insulation properties and high-temperature insulation properties. In addition, since the heat resistance of the adhesive is insufficient, the dimensional change rate is high, and its application is limited. As a method of improving this, as disclosed in Japanese Patent Laid-Open No. 63-168O77, the insulating substrate is roughened without providing an adhesive layer on the substrate surface, and the insulating substrate and the plated metal are sufficiently There is a method to secure good adhesion. This method, by contacting the copper foil with a treatment liquid containing an oxidant, to form copper oxide on the surface of the copper foil, laminating an insulating organic substrate on the surface where the copper oxide is formed,
By removing the copper foil and the copper oxide from the insulating organic base material, the insulating organic base material is roughened, and electroless plating and good adhesion are obtained.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method disclosed in Japanese Patent No. 8077, the adhesive layer does not exist on the surface of the insulating substrate, and the adhesion between the roughened insulating substrate and the electroless plating is good, so that the electrical insulating property between the patterns is improved. The conductor adhesion strength or dimensional stability at high temperature can be improved. When the above method is applied to form an outer layer of a multilayer board, as a manufacturing method thereof, a copper foil is contacted with a treatment liquid containing an oxidant to form copper oxide on the surface of the copper foil, and a surface on which the copper oxide is formed. Laminated with the inner layer circuit so that the insulating organic base material is in contact, form a through hole, remove metallic copper and copper oxide from the insulating organic base material, perform wiring processing including electroless plating, and form wiring The method to do is general.

However, in this method, the oxidation-treated copper foil is removed after the through holes are formed, and the oxidation-treated copper foil is removed by an aqueous solution of copper chloride and hydrochloric acid, an aqueous solution of iron chloride and hydrochloric acid,
Since an etching solution that is generally used in the manufacture of printed wiring boards, such as ammonium persulfate aqueous solution, is used, the inner layer conductor of the copper foil facing the inside of the hole is also etched at the same time as the outer layer oxidation treated copper foil to be dissolved and removed. The so-called negative etch back occurs, and if the amount of this negative etch back is large, it becomes a factor of lowering the electrical connection between layers such as yellowing due to thermal shock and the occurrence of plating voids.

[0007]

A method of manufacturing a printed wiring board according to the present invention is characterized in that a conductor layer and an insulating layer are alternately laminated by a manufacturing process including the following steps in order. a. A step of forming copper oxide on the surface of the copper foil by contacting or anodizing the copper foil with a treatment liquid containing an oxidizing agent. b. A step of laminating the copper foil and the inner layer circuit so that the copper oxide formation surface of the copper foil and the insulating organic base material are in contact with each other. c. A process of forming through holes or non-through holes and performing smearing treatment if necessary. d. A step of removing metallic copper and copper oxide, or only metallic copper from the insulating organic base material by a method including electrolytic etching. e. A step of forming wiring by performing wiring processing including electroless plating after etching.

Various methods can be used for forming the copper oxide on the surface of the copper foil used in the present invention. For example, a method of immersing and treating a copper foil of a treatment liquid containing an oxidizing agent such as sodium chlorite, sodium hypochlorite, potassium chlorate, potassium persulfate, sodium persulfate, potassium persulfate, and ammonium persulfate. Is. In this case, the treatment liquid may be sprayed instead of immersion. Copper oxide can also be formed by anodic oxidation. The copper foil to be used may be another metal foil or a copper foil formed on a support of an organic film. When the support is not used, the thickness of the copper foil is not particularly limited, but it is 18 in terms of handling and price.
It is preferably about 70 μm.

Further, in order to increase the adhesion between the printed wiring board produced by the method of the present invention and the plated metal, it is preferable to roughen the surface of the copper foil in advance. The surface roughening method includes polishing, honing, etching, electroplating, electroless plating and the like. For example, a copper foil for a copper-clad laminate can be favorably used. Before the copper oxide treatment, the copper foil is preferably degreased and washed, or treated with an aqueous solution of hydrochloric acid or an aqueous solution of sulfuric acid so that the copper oxide is uniformly formed.

The insulating organic base material laminated with the copper foil formed with copper oxide includes epoxy, modified polyimide, polyimide,
A thermosetting resin used for a general copper clad laminate such as phenol or a thermoplastic resin such as polyethylene, Teflon, polyethersulfone, or polyetherimide is used. These can be used as a sheet material obtained by impregnating paper or glass cloth with a resin, or may be in the form of a film. A copper foil on which copper oxide is formed and an insulating organic base material are laminated together with an inner layer circuit, a through hole or a non-precious hole is drilled, and then smearing is performed if necessary. As the smear treatment, general methods such as concentrated sulfuric acid treatment, alkaline permanganate treatment, and plasma treatment can be used. Further honing may be performed.

The electrolytic etching is performed by using an oxidation-treated copper foil laminated with an insulating organic base material and using metallic copper as an anode. Since the cathode is in a reducing state during electrolysis, the material is not so selected, but it is preferably insoluble and has a low electric resistance, copper,
Aluminum, stainless steel, etc. can be used. When removing metallic copper and copper oxide from the insulating organic base material, the electrolytic solution is not particularly limited, but an acidic solution such as an aqueous solution of phosphoric acid, an aqueous solution of chromic acid, or an aqueous solution of sulfuric acid / copper sulfate is preferable.
The voltage condition is, for example, 1 to 10V. The electrolytic solution should be agitated to prevent the passivation of the electrodes.

After the electrolytic etching, an etching solution generally used in the production of printed wiring boards, such as an aqueous solution of copper chloride and hydrochloric acid, an aqueous solution of iron chloride and hydrochloric acid, an aqueous solution of ammonium persulfate, can be used in combination. In this case, since the inner layer conductor facing the inside of the hole is etched at the same time as the oxidation-treated copper foil to be electrolytically removed, the thickness of the oxidation-treated copper foil to be etched is preferably 10 μm or less. Further, if necessary, it may be treated with an acidic solution such as an aqueous solution of sulfuric acid for the purpose of dissolving copper oxide. In the case of removing only metallic copper from an insulating organic base material, since copper oxide is soluble in an acidic aqueous solution, it is desirable that the electrolytic solution is neutral or alkaline, and copper pyrophosphate and potassium pyrophosphate are preferable. An aqueous solution or the like is used.

As in the case of removing metallic copper and copper oxide, after the electrolytic etching, an etching solution generally used in the production of printed wiring boards can be used together, but in order to prevent the dissolution of copper oxide. Ammonia alkaline copper etching solution and the like are good. Also in this case, since the inner layer conductor facing the inside of the hole is etched at the same time as the metal copper to be dissolved and removed, the thickness of the metal copper to be etched is preferably 10 μm or less. In addition,
After dissolving and removing only metallic copper from the insulating organic base material, to reduce undissolved copper oxide on the insulating organic base material to metallic copper, sodium borohydride, potassium borohydride,
It is dipped or sprayed in a treatment liquid containing a reducing agent such as dimethylamine borane, diborane, hydrazine. Cathodic reduction may be performed using an external power source.

As the catalytic treatment prior to electroless plating, a general method used for catalytic treatment of printed wiring boards is used. It is also possible to use a material containing a catalyst instead of the catalyst treatment. As the electroless plating, electroless nickel plating, electroless copper plating, or the like is used. General electroless copper plating is used for the conductor of the printed wiring board. When the conductor is formed only by electroless copper plating, a thick electroless copper plating solution having excellent mechanical properties of plated copper is used. When using electroplating together, electroless copper plating is performed after the above catalyst treatment, and then electroplating.

[0015]

In the printed wiring board manufacturing method of the present invention, an oxidized copper foil is used for roughening the surface of the insulating substrate, and the copper foil is dissolved and removed by electrolytic etching. Since this oxidized copper foil has no electrical connection to the inner layer conductor and is independent, the reliability of the interlayer connection is reduced even if there are through holes or non-through holes and the inner layer conductor in the hole faces. It is possible to dissolve and remove the oxidation-treated copper foil used for roughening without causing the negative etch back of the inner layer conductor that causes the above. Therefore, the copper oxide and hydrochloric acid aqueous solution, iron chloride and hydrochloric acid aqueous solution, ammonium persulfate aqueous solution, etc. that are commonly used in the production of printed wiring boards are only used for etching to remove the oxidation-treated copper foil used for surface roughening. The connection reliability between layers is improved as compared with the case of performing.

[0016]

[Example] 35 μ for copper foil-clad laminate manufactured by Nippon Denki Co., Ltd.
m copper foil was prepared, and as a pretreatment, the copper foil was immersed in a degreasing liquid made by Shipley Co., Ltd., a neutral cleaner for 5 minutes, washed with running water, further immersed for 2 minutes in a 10% sulfuric acid aqueous solution, and washed with running water. . This copper foil was subjected to a copper oxide forming treatment under the following conditions. _{NaOH = 15g / 1 Na 3 PO} 4 · 12H 2 O = 30g / 1 NaC1O 2 = 8O8 / l becomes pure water = 11 amounts solution temperature = 85 ° C. copper dipping time = 120 seconds after the copper oxide formation, washed with running water And dried at 80 ° C. for 30 minutes.

Next, a copper clad laminate MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) on which a wiring pattern is formed by photo-etching is used as an inner layer circuit, and a glass cloth-containing epoxy prepreg GE-167 is used. (Manufactured by Hitachi Chemical Co., Ltd.,
Laminate pressing was performed with a structure such that the copper oxide forming surface of the above-mentioned oxidation-treated copper foil was in contact with the copper oxide via the product name). Laminating conditions are as follows: molding pressure 35 kgf / cm ² , temperature 170 ° C. 90
It's a minute. Next, drilling was performed with an NC drill machine. The upper cover plate is an aluminum plate (thickness: 100 μm) and the lower cover plate is a phenol plate (thickness: 1.5 mm), and the drill conditions are as follows.

Drill diameter = O. 9 mm rotation speed = 60 krpm feeding speed = 3600 mm / min

Next, by electrolytic etching under the following conditions,
The oxidation-treated copper foil was removed by dissolution. Copper sulfate = 80 g / 1 Concentrated sulfuric acid = 200 g / 1 Etching liquid additive = Small amount Pure water = 11 Etching liquid temperature = 25 ° C Cathode = Copper current density = 3 A / dm ² Activity including palladium chloride after washing with water A palladium catalyst for initiating the electroless copper plating reaction was applied by immersing in a chemical treatment solution.

Next, a photosensitive dry film for electroless copper plating, Photec SR-3OOO (Hitachi Kasei Kogyo Co., Ltd., trade name, thickness 35 μm) was roughened with a Tokojo laminator. Laminated on the substrate. Next, a photomask on which a desired pattern was drawn was brought into close contact with this, irradiated with 90 mj / cm ² by an ultraviolet exposure device, and further heated at 80 ° C. for 5 minutes. A resist image was formed by spraying this with 1, 1, 11-trichloroethane and developing it.

Next, electroless copper plating having the following composition and conditions was performed. CuSO ₄ 5H ₂ O = 1 g / 1 EDTA.4Na = 40 g / 1 pH = 12.3 Plating solution additive = Small amount Plating solution temperature = 70 ° C Plating film thickness = 35 μm

Comparative Example The copper foil used in the examples was subjected to the same oxidation treatment, washing with water and drying as in the examples, laminated with the same constitution and conditions as the examples, and punched. Next, spray etching was carried out using a copper chloride / hydrochloric acid etch solution to dissolve and remove metallic copper and copper oxide in the outer layer. Then, under the same conditions as in the example, a plating catalyst was applied, the resist used in the example was subjected to the same conditions as the example, such as lamination, exposure, and development, and electroless copper plating was performed under the same conditions as the example. It was With respect to the above Examples and Comparative Examples, the reliability of through-hole connection was evaluated by a hot oil test. 260 ° C ± 5 ° C, 10 seconds oil immersion, room temperature
Immersion in water for 10 seconds and magic dry (trichloroethane) immersion at room temperature for 10 seconds were set as one cycle, and after a predetermined number of treatments, the cross section of the through hole was observed to examine the occurrence of cracks. In addition, in Examples and Comparative Examples, the amount of negative etchback was measured by observing the through holes even before applying the plating catalyst. Tabulated those results

[0023]

[Table 1]

[0024]

According to the present invention, it is possible to manufacture a printed wiring board which eliminates the deterioration of insulation resistance and heat resistance due to the adhesive and has high reliability of connection between layers.

[Brief description of drawings]

1A to 1E are process diagrams of a printed wiring board according to an embodiment of the present invention.

[Explanation of symbols]

 1 Copper Foil 2 Copper Oxide 3 Insulating Organic Base Material 4 Interior Conductor 5 Interior Substrate 6 Hole 7 Plating Resist 8 Copper Plating

Claims (3)

[Claims] 1. A method of manufacturing a printed wiring board, characterized in that conductor layers and insulating layers are alternately laminated by a manufacturing process including the following steps in order. a. A step of forming copper oxide on the surface of the copper foil by contacting or anodizing the copper foil with a treatment liquid containing an oxidizing agent. b. A step of laminating the copper foil with the inner layer circuit so that the copper oxide forming surface of the copper foil is in contact with the insulating organic base material. c. A step of forming through-holes or non-through-holes and performing smear treatment if necessary. d. A step of removing metallic copper and copper oxide, or only metallic copper from the insulating organic base material by a method including electrolytic etching. e. A step of forming a circuit by performing wiring processing including electroless plating after etching. 2. The printed wiring according to claim 1, wherein in the step d, when only metallic copper is removed from the insulating organic base material, electrolytic etching and etching with an ammonia alkaline copper etching solution are used together. Method of manufacturing a plate. 3. In the step d, when only metallic copper is removed from the insulating organic base material, some undissolved copper oxide on the insulating organic base material is brought into contact with a treating solution containing a reducing agent or externally. The method for producing a printed wiring board according to claim 1 or 2, wherein the wiring is formed by a method including electroless plating after reduction to metallic copper by an electrochemical method using a power source.