JPH03296295A - Manufacture of multilayer printed circuit board - Google Patents

Abstract

PURPOSE:To prevent and suppress generation of negative etchback by covering a conductor circuit in a through hole or a nonthrough hole with etching resist when metal copper and copper oxide or only metal copper is melted to be removed from an insulation organic board. CONSTITUTION:Copper foils are formed as outermost layers, and so laminated together with an inner layer circuit that the forming surface of a copper oxide 1 is brought into contact with a base material 2 of insulating organic material. A through hole or nonthrough hole is formed, and smeared as required. An inner layer conductor 3 in the through or nonthrough hole is covered with insoluble or hard soluble substance to copper etchant. The surface of a board is polished to expose the foil. Metal copper and copper oxide or only the metal copper is removed from the organic base material. As required, the conductor covering substance in the through or nonthrough hole is removed, and wired including electroless plating to form a wiring.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a multilayer printed wiring board.

[Conventional technology]

In recent years, demands for electronic devices such as smaller size, lighter weight, multi-functionality, and lower prices have become more active, and accordingly, demands for lower prices, higher density, and higher reliability for printed wiring boards have also increased.

In response to these needs, the current mainstream manufacturing method for printed wiring boards is the Zab1 Ractical method.
The manufacturing process is complex and long, making it difficult to reduce costs. Additionally, it is said that there is a limit to how high density can be achieved because it is difficult to make wires thinner and through holes smaller, so additive methods are attracting attention.

The additive method is a method in which a conductive metal is plated to a desired thickness on an insulating substrate by electroless plating to form a wiring pattern. Adhesion with conductive metal formed by plating is extremely important for printed wiring boards.

The best way to improve adhesion between an organic substrate (insulating substrate) for a printed wiring board and plated metal is to treat the surface of the organic substrate physically or chemically to make it hydrophilic. This is a method to roughen and roughen the surface.

Among these methods, the most commonly used methods are:
In this method, a resin layer that can be made hydrophilic by treatment with a chemical roughening liquid and a rough surface with fine irregularities is provided on the substrate surface, and then treated with a chemical roughening liquid.

However, in this method, a roughening liquid must be used to roughen the surface of the adhesive layer-coated substrate.

Most of the roughened surfaces available contain oxidizing agents and are highly toxic. This requires a poor working environment and special waste liquid treatment.

Additionally, components soluble in the roughening solution generally have poor electrical insulation properties.

For example, there is deterioration in moisture-resistant insulation properties and high-temperature insulation properties. Furthermore, since the adhesive layer has low heat resistance and a high rate of dimensional change, there are limits to its application to multilayer printed wiring boards that require high dimensional accuracy and through-hole connection reliability.

As a method to improve this, Japanese Patent Application Laid-Open No. 63-168077
As shown in the above publication, there is a method of roughening the insulating substrate itself without providing an adhesive layer on the surface of the substrate. In this method, copper foil is brought into contact with a treatment solution containing an oxidizing agent to form copper oxide on the rough surface of the copper foil, and a base material of an insulating organic material is laminated on the surface on which copper oxide has been formed. roughen the insulating organic substrate by removing copper foil and copper oxide from
It provides good adhesion to electroless plating.

Up to now, the above-mentioned substrates have been applied to double-sided boards by wiring forming methods such as full additive methods and semi-additive methods.

[Problem to be solved by the invention]

The method disclosed in JP-A-63-168077 does not have an adhesive layer on the surface of the insulating substrate and has good adhesion between the roughened substrate and the electroless plating, so there is no electricity between the patterns. Although it improves insulation properties, conductor adhesion strength at high temperatures, and dimensional stability, to date its application has been limited to double-sided boards and has not been used for multilayer boards.

A method for manufacturing a multilayer board having the above-mentioned substrate as the outermost layer involves contacting a copper foil with a treatment solution containing an oxidizing agent to form oxidation 114 on the rough surface of the copper foil. As the outermost layer, the copper oxide formation surface and the insulating organic material base material are laminated together with the inner layer circuit, a through hole is formed, and metallic copper and oxide are removed from the insulating organic base material. A basic method is to form wiring through wiring processing including electrolytic plating.

However, in this method, the step of removing the oxidized copper foil is performed immediately after forming the through hole, so the inner layer conductor facing inside the hole is also etched at the same time as the outer layer of the oxidized copper foil that is to be dissolved and removed. Negative stress occurs, and if the amount of negative stress is large, it becomes a factor that causes a decrease in through-ball connection reliability, such as embrittlement against thermal shock and the occurrence of plating defects.

The present invention provides a method for manufacturing a multilayer printed circuit board 1 to a wiring board that prevents and suppresses negative leakage of inner layer conductors in through holes or non-through holes and has excellent connection reliability.

[Failure to solve the problem]

The present invention has a manufacturing process including the following steps in order:
This is a method for manufacturing a multilayer printed wiring board having a structure in which conductor circuits and insulating layers are alternately laminated.

(a) A step of forming copper oxide on the rough surface of the copper foil by contacting the copper foil with a treatment liquid containing an oxidizing agent or using an electrochemical method.

(b) A step of laminating the copper foils as the outermost layer together with the inner layer circuit so that the surface on which the copper oxide is formed is in contact with the base material of the insulating organic material.

(c) A step of forming through holes or non-through holes and performing smear treatment if necessary.

(d) A step of coating the inner layer conductor in the through hole or the non-through hole with a substance that is insoluble or poorly soluble in a copper etching solution that serves as an etching resist.

(e) A step of polishing the substrate surface to expose the copper foil.

(f) A step of removing metallic copper and copper oxide or only metallic copper from the insulating organic substrate.

(g) If necessary, the step of removing the conductor coating material in the through hole or non-through hole and performing wiring processing including electroless plating to form wiring.

There are various methods for forming copper oxide on the surface of the copper foil used in the present invention. For example, the copper foil is treated by immersing it in a treatment solution containing an oxidizing agent such as sodium chlorite, sodium hypochlorite, potassium persulfate, potassium chlorate, or potassium perchlorate. In this case, spraying of the treatment liquid may be used instead of immersion. Copper oxide can also be formed by anodic oxidation.

The copper foil used may be one in which the copper foil is formed on a support such as another metal foil or an organic film. When a support is not used, there is no particular restriction on the thickness of the copper foil, and from the viewpoint of handling and cost, a thickness of 18 to 70 μm is preferable.

Further, in order to increase the adhesive strength 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. Methods for roughening the surface include polishing, honing, etching, electroplating, and electroless copper plating. For example, copper foil for copper foil-clad laminates can be used satisfactorily.

Before copper oxide treatment, in order to ensure that copper oxide is formed uniformly, it is recommended that the copper foil be degreased and treated with an aqueous solution of hydrochloric acid or an aqueous sulfuric acid solution. As the insulating organic material to be laminated, thermosetting resins used in common copper foil-clad laminates, such as epoxy, modified polyimide, polyimide, and phenol, can be used. For these, prepreg is used, which is a paper base material or glass fiber cloth material coated with the resin described in "2".

Thermoplastic materials such as polyethylene, Teflon, polyethersulfone, and polyetherimide may also be used.

After laminating the copper foil on which copper oxide has been formed, the insulating organic base material, and the inner layer circuit, and drilling through holes or non-through holes, smear treatment is performed as necessary. For the smear treatment, general methods such as concentrated sulfuric acid treatment, alkaline permanganate treatment, and plasma treatment can be used. Rough honing may also be performed.

Copper ethotinc' for the resist of the inner layer circuit inside the hole? The following which are insoluble or poorly soluble are applicable at night.

(1) Acid- or alkali-resistant polymeric material.

(2) Nickel, solder, tin, and gold by electroless or displacement plating (3) Copper oxide by oxidation treatment (4) Films by treatment with alkylimidazole, benzotriazole, and stearic acid As a polymer with good acid and alkali resistance Examples include polyethylene, polystyrene, polyester, and methacrylic resin. These can be dissolved in a soluble solvent, and after coating, the solvent can be evaporated. For example, in the case of polyethylene, toluene can be used. These can be used with both acidic and alkaline etchants. Also effective is the hole-filling ink that is commonly used in the 4J hole-filling method for manufacturing copper through-hole boards to protect the copper in the through-holes from etching. Both heat drying type and ultraviolet curing type can be used, and are sold by Sanei Chemical Co., Ltd., etc. Many of them act as a strong resist against acidic enthesis, and some can be used in alkaline conditions.

Nickel and solder are electroless plated. −
For boat fishing, it is necessary to apply a plating catalyst prior to the plating process. As the plating catalyst, in addition to a two-liquid type of stannous chloride and palladium chloride, palladium colloid, etc., an acidic aqueous solution of noble metal ions can also be used. Nickel plating containing a boron thread reducing agent has catalytic activity on the copper surface and can be deposited without the addition of a plating catalyst. Tin and gold are produced by displacement plating. Although it is possible to use these with an acidic etching solution, it is preferable to use an alkaline etching solution. These plating solutions are sold by Okuno Pharmaceutical Co., Ltd., Nippon Kanigen Co., Ltd., etc.

Copper oxide can be obtained by contacting the copper foil with an oxidizing agent-containing treatment solution similar to that used for forming copper oxide on copper foil.
It becomes a resist of raw esochingun night.

Alkylimidazole forms a compound with copper, alkylimidazole copper, and benzotriazole and stearic acid are adsorbed on the copper surface or form a poorly soluble film, which serves as a resist for alkaline etching solution.

When forming an etching resist on the inner layer circuit inside the hole,
After drilling or smearing, it is preferable to clean the forming surface as necessary. After forming an etching resist on the inner layer circuit in the hole, an etching solution is used to remove metallic copper and copper oxide or only metallic copper. This etching solution must be compatible with the aforementioned etching solution, such as ammonium persulfate aqueous solution, which is commonly used as an etching solution for printed wiring boards, an aqueous solution of iron chloride and hydrochloric acid, an aqueous solution of copper chloride and hydrochloric acid, An alkaline aqueous solution containing copper ammonium and complex ions can be used.

Note that when metallic copper and copper oxide or only metallic copper are dissolved and removed using the etching solution, polishing or the like is performed to expose the surface to be etched. Sanderherd polishing, puff polishing, etc. can be used.

After removing metallic copper, copper oxide, or metallic copper from the insulating organic substrate, the in-hole ethosin brace I- is peeled off, if necessary. Polyethylene, polystyrene, 2-polyester, methacrylic resin, etc. are peeled off using a dissolved solvent during application.

For example, in the case of polyethylene, toluene is used. Filling ink can be removed with an alkaline aqueous solution, and copper oxide and alkylimidazole copper can be removed with an aqueous hydrochloric acid solution. It is preferable to remove the dirt using a spray or an ultrasonic cleaner.

For the catalyst treatment prior to electroless copper plating, a general method used for catalyst treatment of printed wiring boards is used. Instead of catalytic treatment, catalyzed materials can also be used.

As the electroless plating, electroless nickel plating, electroless copper plating, etc. are used. Generally, electroless copper plating is used for the conductors of printed wiring boards.

[Effect]

In the multilayer printed wiring board manufacturing method of the present invention, when metal copper and copper oxide or only metal copper are dissolved and removed from an insulating organic substrate, conductor circuits in through holes or non-through holes are covered with etching resist.

Therefore, when etching only metallic copper, copper oxide, or metallic copper, negative etching of the inner layer conductor, which causes poor connection reliability, is prevented and suppressed, compared to the case where no etching resist is formed on the conductor circuit. Connection reliability is improved, and it becomes possible to manufacture highly reliable multilayer printed circuit boards 1 to wiring boards by the additive method.

〔Example〕

Prepare 351Jm copper foil for copper foil-clad laminates made by Hiki Denki Co., Ltd. As a pretreatment, soak the copper foil in Neutral Clean, a degreasing solution made by Shisoplay Co., Ltd. for 5 minutes, rinse with running water, and then 10% sulfuric acid. It was immersed in water for 2 minutes and washed under running water. This copper foil was subjected to copper oxide formation treatment under the following conditions.

NaOH=15g/A Na3PO4-12H20=30g//NaCl20z
=80g/l pure water
-14 volume Liquid temperature -85°C Copper foil immersion time -120 seconds After forming copper oxide, it was washed with running water and dried at 80°C for 30 minutes.

Next, a copper-clad laminate MCL-E-67 (Hitachi Chemical Co., Ltd., trade name) on which a wiring pattern was formed by photoetching was used as the inner layer circuit, and Glass Seller Epoxy Prepreg GE-67 (Hitachi Chemical Co., Ltd., trade name) was used as the inner layer circuit. Laminate pressing was performed with the above-mentioned copper-clad configuration using the Reykja knob. Lamination conditions are molding pressure 35kgf/c and temperature 1
90 minutes at 70°C.

Next, holes were made by drilling. Top plate ten-tan aluminum + anti-(100μmt), bottom plate (anti-phenol +
ff11.5mmt), and the trill conditions are as follows.

(mm) (krpm) (mm/m1n)
0.9 60 3600 Next, hole filling ink 5EP-490W (trade name, Sanei Chemical Co., Ltd.) was filled into the holes, and after drying at 100° C. for 60 minutes, the ink on the substrate surface was removed by Hough polishing.

5 Next, the metallic copper and copper oxide were spray etched using an aqueous solution of copper oxide and hydrochloric acid.

After washing with water, the hole-filling ink was removed with a 3% NaOH aqueous solution shower at 40°C, and the plate was washed with running water.

Next, a palladium catalyst was applied to start the electroless copper plating reaction by immersing it in an activation treatment solution containing palladium chloride.

Next, electroless copper plating was performed with the following composition and conditions.

CuS○a・5HzO=1 g/12 EDTA・4Na -40g/42 p)T=12.3 37%CH40=3 m 7! / R plating solution additive - Small amount Plating solution temperature -70℃ Plating film thickness -35 μl [Comparative example] The copper foil used in the example was subjected to the same oxidation treatment, water washing, and drying as in the example, and the same configuration as in the example was prepared. The copper foil and copper oxide were etched using the same method and conditions as in the example. Thereafter, application of a plating catalyst and electroless plating were performed using the same method and conditions as in Example 6.

Regarding the above Examples and Comparative Examples, through-hole connection borrowing and M properties were evaluated using a true oil test. 260°C±
Immersion in oil at 5°C for 10 seconds, immersion in water at room temperature for 10 seconds,
Magic dry for 10 seconds at room temperature (trichloroethane)
After a predetermined number of immersion cycles, the cross section of the through ball was observed to check for cracks.

In addition, for the Examples and Comparative Examples, the cross-sections of the through balls were also observed before being immersed in the electroless copper plating solution, and the amount of negative etch was measured. The results are shown in the table.

It is possible to prevent and suppress the occurrence of cracking, and it is possible to manufacture a multilayer printed wiring board with excellent connection reliability.

[Brief explanation of drawings]

FIG. 1 is a process diagram of a multilayer printed wiring board according to an embodiment of the present invention. ■ Oxidation-treated copper foil 2 Organic base material 3 Inner layer conductor 4 Hole 5 Hole-filling ink 6 Copper plating [Effects of the invention] According to the present invention, C4 to the origin of negative enochihasoku

Claims (2)

[Claims] 1. A method for manufacturing a multilayer printed wiring board having a structure in which conductor circuits and insulating layers are alternately laminated, using a manufacturing process including the following steps in order. (a) A step of forming copper oxide on the rough surface of the copper foil by contacting the copper foil with a treatment liquid containing an oxidizing agent or using an electrochemical method. (b) A step of laminating the copper foils as the outermost layer together with the inner layer circuit so that the surface on which the copper oxide is formed is in contact with the base material of the insulating organic material. (c) A step of forming through holes or non-through holes and performing smear treatment if necessary. (d) A step of coating the inner layer conductor in the through hole or non-through hole with a substance that is insoluble or poorly soluble in a copper etching solution that serves as an etching resist. (e) A step of polishing the substrate surface to expose the copper foil. (f) A step of removing metallic copper and copper oxide or only metallic copper from the insulating organic substrate. (g) If necessary, the step of removing the conductor coating material in the through hole or non-through hole and performing wiring processing including electroless plating to form wiring. 2. In claim 1, the copper etchant-insoluble or poorly soluble film provided as an etching resist in the through hole or the non-through hole comprises at least one of the following:
A method of coating inner layer conductors. (a) Acid- or alkali-resistant polymeric material. (b) Nickel, solder, or tin, gold by electroless or displacement plating (c) Copper oxide by oxidation treatment (d) Coating by alkylimidazole, benzotriazole, stearic acid treatment