JPS61266241A - Surface treating method of copper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a composite material of copper and resin, and in particular, copper is suitable for suppressing the corrosive effect of copper and improving the adhesion between copper and resin. Concerning surface treatment methods.

[Background of the invention]

Currently, epoxy resins are often used as base materials for multilayer printed boards. In order to improve the adhesion between epoxy resin and copper wiring of multilayer printed boards, Eita: Printed wiring materials and processing technology, CMC Co., Ltd., p76-p81.
As described in (1981), a process is usually performed to form an oxide film on the surface of the copper wiring. However, when the type of resin material is changed, it is not always possible to obtain sufficient adhesive strength, and the conditions for forming the oxide film must also be changed depending on the type of resin. In other words, in order to increase the packaging density of semiconductors on the board, higher wiring density is required, and as a result, polyimide-based resin materials are being used for the board with better dimensional accuracy. It has become to. In order to improve the adhesive strength between this polyimide resin and copper wiring, the copper wiring treatment method uses chlorous acid as an oxidizing agent and an alkaline solution containing phosphate ions to form copper oxide on the copper wiring. There is a way to do it. As a result of implementing this method, the adhesive properties were 1.0 kg/■
It has been found that there is a method for surface treatment of copper that exhibits the above-mentioned high beer strength. However, on the other hand, it has been found that as long as an oxide film is used, the oxide film dissolves in an atmosphere where it comes into contact with acid, and the adhesive properties deteriorate. For this reason, we investigated a method of electrically reducing the copper surface as a treatment method that does not use an oxide film and also provides a high beer strength value.

As a result, it was found that there are processing conditions that give beer a high value and also have excellent acid resistance properties. However, the obtained reduction-treated film has variations between samples or within the sample plane due to current density distribution, etc.
Beer strength did not always have high values.

In addition, as a method to improve the adhesive properties between copper wiring and resin,
A method is shown in which the surface of the copper wiring is roughened by etching, the surface of the copper wiring is coated with a film of the coupling agent using a silane-based coupling agent, and then the copper wiring and the resin are bonded. It has been reported that this improves adhesive strength (Patent Publication: 1983-349).
07).

However, sufficient acid resistance has not always been obtained.

[Purpose of the invention]

An object of the present invention is to provide a method for surface treatment of copper that has little variation in adhesive properties with resin, always has stable adhesive strength, and has excellent hydrochloric acid resistance.

[Summary of the invention]

One way to increase the adhesion of copper to resin is to significantly roughen the surface of the copper (size of unevenness:
>6 μm), possible. However, when attempting to form fine copper wiring on an insulating board, the roughness of the copper surface is subject to restrictions. Therefore, in order to form a copper surface treatment film that always has little variation, exhibits high adhesion properties, and has excellent hydrochloric acid resistance while keeping the surface roughness to less than 6 μm, we have developed an oxide film on the copper surface. After formation, it is electrically reduced. Subsequently, when a film of an organic compound containing nitrogen in a heterocycle, which is used as a corrosion inhibitor for copper, was applied to the surface of the reduced film, it was found that the adhesive properties were further improved and the hydrochloric acid resistance was further improved. Ta.

[Embodiments of the invention]

Example 1 The surface of a 70 μm thick steel foil was soaked in distilled water IQ.

The steel foil is oxidized with a solution containing 20 g of NaCQo, 5Qg NaaPo, and 10 g of NaOH to form a film containing copper oxide on the surface of the steel foil. After electrically reducing this film in an alkaline aqueous solution, it was immersed in a solution containing 10-" mojl of 1,2°3-benzotriazole per IQ, dried, and coated with a polyimide prepreg under a pressure of 15
kg/cm'' at 170'C for 1h and bonded. The beer strength of copper foil against polyimide resin is 1.4.
kg/c, and the adhesive properties were good. Regarding hydrochloric acid resistance, we created a multilayer board as shown in Figure 1.
After drilling a hole, it was immersed in a 17.5% hydrochloric acid solution for 1 hour, and the width of penetration of the hydrochloric acid into the interface between the copper foil and the polyimide resin from the side of the through hole was measured. As a result, no penetration of hydrochloric acid was observed, and the hydrochloric acid resistance was good.

Example 2 Pyrrole, dibenzopyrrole, pyrazole, 2,1 instead of 1,2,3-benzotriazole in Example 1
-Benzopyrazole, thiazole.

2-aminothiazole, benzothiazole, 2-aminobenzothiazole, imidazole, 2-aminoimidazole, benzimidazole, 2-aminobenzimidazole, 1,2.3-triazole, 2,1,3-triazole, 1,2. 4-triazole, 4,1,2. -triazole, 3-amino 1,2.4 triazole, alkyl-1゜2.3 benzotriazole, naphtho-1,2
, 8-triazole, alkylnaphtho-1,2,3-triazole, 3-mercapto-1,2,4-triazole, ■-methyl-2-mercaptoimidazole, mercaptobenzothiazole, thiourea.

Similar effects on beer strength and hydrochloric acid resistance were observed when ethylenethiourea, trimethylenethiourea, and phenylenethiourea were used individually or in combination.

Example 3 When an epoxy resin was used instead of the polyimide resin in Example 1, the beer strength was 1.5 kg/ct.
a, and the hydrochloric acid penetration was 2 μm or less, showing good characteristics in both cases.

Comparative Example 1 In Example 1, the step of immersing the substrate in a solution containing 1,2,3-benzotriazole after reducing the oxide film formed on the copper wiring was omitted. The other conditions were the same as in Example 1. As a result, the beer strength was 1.1 kg/c.
m, the amount of hydrochloric acid penetration was 2 μm, and both the adhesive properties and hydrochloric acid resistance of Example 1 were poor.

〔Effect of the invention〕

According to the present invention, it is possible to create a copper surface treatment film that has excellent adhesive properties to polyimide resins or epoxy resins and has excellent hydrochloric acid resistance, so it is effective in surface treatment of copper for multilayer printed boards. be.

[Brief explanation of drawings]

The figure is a cross-sectional view of a multilayer board for evaluating the amount of hydrochloric acid seepage. DESCRIPTION OF SYMBOLS 1... Electrolytic reduction membrane, 2... Copper foil, 3... Polyimide or epoxy resin, 4... Organic compound containing nitrogen in the heterocycle, 5... Throughhole.

Claims (1)

[Scope of Claims] 1. A method for surface treatment of copper, which comprises forming a film of an organic compound containing nitrogen in a heterocyclic ring on copper, and adhering the copper and resin through this film. 2. Claim 1, characterized in that the surface of the copper as the inner layer circuit copper of the printed wiring board is composed of at least one of metal copper, a metal layer containing an oxide, and an oxide film layer. Copper surface treatment method described in section. 3. The copper surface treatment method according to claim 2, wherein the metal layer containing an oxide is electrically or chemically reduced or a combination thereof.