JP3332047B2 - Processing method of inner layer copper foil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic equipment, electrical equipment,
The present invention relates to a method for treating a copper foil for an inner layer circuit used for manufacturing a multilayer printed wiring board used for a computer, a communication device, and the like. In particular, the present invention relates to a method for manufacturing a multilayer printed wiring board that completely prevents the occurrence of “halos” or “pink rings”.

[0002]

2. Description of the Related Art In a multilayer printed circuit board, as a method for improving a multilayer adhesiveness of an inner layer board on which a printed circuit is formed, a method using a copper foil having fine irregularities formed on both sides in advance, a printed circuit for the inner layer, and the like. After formation, a. A method of forming copper oxide fine irregularities on a copper foil surface using an oxidizing aqueous solution, b. There is known a method of treating a copper foil surface with a silane-based or organic titanate-based coupling agent. From the viewpoint of adhesiveness and economy, usually a printed circuit for the inner layer is formed on a copper-clad laminate with a glossy surface, and then treated with an oxidizing alkaline aqueous solution to form a brown or black copper oxide fine uneven film. What was used is used.

[0003] However, when the inner plate having the copper oxide fine unevenness formed thereon is subjected to electroless plating and then electroplating, a so-called halo or pink ring is easily generated, and a printed material such as an insulating material is formed. There is a disadvantage that causes a reduction in the reliability of the wiring board.

[0004] As a method for preventing halo or pink ring generated when the brown or black copper oxide fine unevenness is used, c. a method of reducing the copper oxide fine uneven film on the surface of the copper foil obtained in step a) with a reducing agent aqueous solution to change it to a cuprous oxide or metallic copper fine uneven film (Japanese Unexamined Patent Publication No.
No. 6-153797) has been disclosed. These methods are effective methods for preventing the generation of halos, but the surface of cuprous oxide or metallic copper is unstable and easily changes, and it is necessary to perform the next step as soon as possible after the treatment. . In addition, when performing the reduction treatment, hydrogen gas is generally generated, and if no countermeasures are taken, there is a danger of explosion and the like. Further, the conditions for the reduction treatment are difficult, and strict management of the treatment liquid is required. In addition, there are limitations on the laminating press conditions of the processing plate.

On the other hand, d. a method of dissolving and removing the fine uneven film of copper oxide on the surface of the copper foil obtained in the step (a) with an acidic chelate solution having a pH of 3.5 to 4.0 (PRINTED CIRCUITFAB)
RICATION, AUGUST, 1984), and a treatment solution is commercially available from McDermid. This method comprises the steps of c. Compared to the reduction method, the method is advantageous in that the safety and the laminating press conditions are wide, but it has drawbacks that stable non-halo treatment cannot be performed stably and that the inner layer adhesive strength is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention stably and completely suppresses the generation of halo and suppresses the decrease in adhesive strength to an acceptable level by using an inner layer copper foil treating solution commercially available from McDermid. It is an object of the present invention to provide a simple method. As a result, the present inventors have found a method of performing a soft etching more than a certain amount before the oxidation treatment, dissolving the copper oxide film after the oxidation treatment, and further performing a rust prevention treatment on the surface thereof. It was completed. Further, it has been found that the present invention can significantly reduce the standard processing time of the inner copper foil processing method marketed by McDermid.

[0007]

According to the present invention, a copper foil surface of an inner layer plate on which a printed circuit is formed as an intermediate layer is first soft-etched with an etching agent to a thickness of 1.0 μm to 3.0 μm to obtain a fine rough surface. After the surface treatment, the surface is treated (pre-dip) with an alkaline aqueous solution, and further oxidized with an alkaline sodium chlorite aqueous solution to obtain 30 to 60 mg /
After forming a copper oxide fine unevenness film (black oxide) of dm ^2, the copper oxide film is 90-99 with an acidic chelate aqueous solution.
% Dissolution removal (post-dip), followed by immersion in a copper rust preventive solution such as benzotriazole to form a rust preventive film. This is an inner layer copper foil processing method.

[0008] In order to completely prevent the generation of halo according to the present invention, the outline of the inner layer copper foil treatment step is as follows: (1) soft etching → (2) washing with water → (3). Pickling → (4) Rinse → (5). Predip → (6). Black oxide
→ (7). Rinse → (8). Post dip → (9). Rinse → (10). Rust prevention treatment → (11). Rinse → (12). Dry.

The multilayer printed board of the present invention is an inner layer board on which an inner layer printed circuit used as an intermediate layer is formed, in which a copper foil surface is chemically oxidized to form a black or brown copper oxide fine uneven film. Multilayer printed wiring of inner surface plate, prepreg used for multi-layer bonding, prepreg for forming outer layer and copper foil or laminated material such as single-sided copper-clad laminate, and copper foil on both outer surfaces manufactured by lamination molding method It is made by drilling through holes in a plate, desmearing, and then electroless plating, and is the most commonly used one.

As the soft etching solution used in the present invention, known substances such as copper chloride, iron chloride, sodium persulfate, potassium persulfate, and hydrogen peroxide-sulfuric acid can be used. Among them, particularly preferred is sodium persulfate 1
100 g / 1 (liter) aqueous solution at 30-40 ° C, 1-4
In this method, the amount of etching is 1.0 μm or more, and preferably 1.5 to 3.0 μm.

Here, for pickling, a 1 to 20% w / w solution of sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid or the like is used. Particularly preferably, a 10 w / w% aqueous solution of sulfuric acid is used at a treatment temperature of 20 to
35 ° C., treatment time 1-2 minutes.

The pre-dip uses an aqueous alkali solution such as sodium hydroxide and potassium hydroxide. Particularly preferred among these is sodium hydroxide, which has a concentration of 3
A solution adjusted to be 0 to 50 g / l is used. Preferred processing conditions are a temperature of 45 to 55 ° C. and a time of 1 to 2 minutes.

As the black oxide, an alkaline aqueous solution such as sodium chlorate, sodium chlorite, sodium persulfate and potassium persulfate is used. Among them, preferred is sodium chlorite, having a concentration of 100 to 140 g.
/ L (liter), a solution adjusted to be alkaline at a sodium hydroxide concentration of 30 to 50 g / 1 is used. Preferred processing conditions are a temperature of 70 to 80 ° C. and a time of 3 to 6 minutes.

The post-dip is performed by adding a mineral acid or an organic acid such as sulfuric acid, phosphoric acid, nitric acid, and acetic acid to an aqueous solution of ethylenediaminetetraacetic acid (EDTA) to obtain an EDTA concentration of 0.05 to 10%.
A solution adjusted to be 0.20 M and pH 3.5 to 4.0 is used. Preferred conditions are a temperature of 50 to 60 ° C. and a time of 3 to 6 minutes.

As the copper-based rust preventive used in the present invention,
Known compounds such as benzotriazole, benzothiazole, tolyltriazole, alkylimidazole, and benzylimidazole can be used. Particularly preferred among these are aqueous solutions of benzotriazole 0.5-5 g / l (liter), preferably 1-3 g / l, 30-80 g / l.
C., preferably at 50 to 70.degree. C. for 0.5 to 5 minutes, preferably 1 to 3 minutes.

The drying conditions are not particularly limited as long as the water content of the inner plate on which the printed circuit is formed can be sufficiently removed. Preferred drying conditions are 90 ° C.
For 30 to 60 minutes.

[0017]

A sufficiently thick oxide film can be formed on the surface of the copper circuit of the inner layer circuit board, and after the oxide film is dissolved and removed, a roughened surface having a sufficient anchor effect can be left. Thereby, the adhesive strength between the prepreg resin and the copper circuit can be increased. Furthermore, by rust prevention treatment,
The solubility of the oxide film in an acid such as plating can be reduced, and the generation of halo can be completely suppressed. Further, the treatment film can be stabilized, and the storage stability can be increased.

[0018]

Next, the present invention will be described in detail with reference to examples. Example 1 A copper foil having a thickness of 70 μm was formed on both sides, and the thickness was 0.8 m.
An electric circuit was formed on both sides using a glass cloth-based epoxy resin laminate (EL-170 manufactured by Mitsubishi Gas Chemical Co., Ltd.). Next, a soft etching aqueous solution having a concentration of 100 g / 1 (liter) of sodium persulfate was immersed at 35 ° C. for 2 minutes to perform soft etching of about 1.5 μm.

This soft-etched laminate was immersed (pre-dip) in a 40 g / l aqueous sodium hydroxide solution at 50 ° C. for 1 minute. Next, an aqueous solution of alkaline sodium chlorite (sodium chlorite 120 g / l,
The copper circuit surface is oxidized (blackened) by immersing it in sodium hydroxide (40 g / l) at 75 ° C. for 3 minutes to further roughen the circuit surface and to obtain 50 mg of the second copper oxide film. / Dm ² (black oxide).

Next, a solution prepared by adding sulfuric acid to an EDTA aqueous solution (EDTA concentration 0.10 M, PH 3.7)
Immersion at 55 ° C for 3 minutes to dissolve and remove about 95% of the cupric oxide film on the circuit surface (post dip)
did.

Next, a 3 g / 1 aqueous solution of benzotriazole was prepared and immersed at 70 ° C. for 1 minute to form a rust preventive film on the circuit surface (rust preventive treatment). Next, after sufficiently washing with pure water, it was dried at 90 ° C. for 60 minutes.

The prepreg having a thickness of 0.1 mm (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was manufactured by impregnating and drying a glass cloth substrate with an epoxy resin on both surfaces of the intermediate layer.
GEPL-170) was stacked three by three, and further, a copper foil having a thickness of 18 μ was stacked on the outside thereof, and 30 kg / cm
^{2. A} four-layer printed wiring board was obtained by laminating at 170 ° C. for 60 minutes. The lamination was performed within one day after the treatment of the intermediate layer.

Next, 0.4 mmφ is applied to the four-layer printed wiring board.
Using a drill bit, the number of revolutions was 80,000 rpm,
Drilling was performed under a drilling condition of a feed speed of 1.6 m / min (20 μ / rev). Next, a desmear treatment, an electroless plating treatment, and an electroplating treatment (copper sulfate bath) were performed.

The through-hole portion of the printed wiring board thus processed was polished horizontally until the intermediate layer was sufficiently observed, and the occurrence of halos was observed with a microscope. The observation place is the initial stage of drilling (1 to 500 holes) and thereafter (100 holes).
(1 to 1500 holes). The interlayer adhesion between the inner copper foil and the resin in the four-layer printed wiring board was measured. Table 1 shows the processing conditions, halo size, and inner layer adhesive strength.

Example 2 The same procedure as in Example 1 was carried out except that the conditions of the processing steps were changed to 2 minutes for pre-dip, 4 minutes for black oxide, 6 minutes for post-dip, and 2 minutes for rust prevention treatment. Was. Example 3 Example 3 was carried out in exactly the same manner as in Example 1, except that the condition of the treatment step was changed to 3 μm for soft etching.

Example 4 The procedure of Example 1 was repeated, except that the conditions of the processing steps were changed to 3 μm for soft etching, 2 minutes for black oxide, 2 minutes for post-dip, and 1 minute for rust prevention treatment. . Example 5 The same procedure as in Example 1 was carried out except that the laminate was formed after standing for 7 days after the treatment of the intermediate layer.

Comparative Example 1 The procedure of Example 1 was repeated, except that the post-dip treatment and the rust prevention treatment were not performed. Comparative example 2 Except not performing a rust prevention process, it carried out exactly like Example 1. Comparative example 3 It carried out exactly like Example 5 except not performing a rust prevention treatment. Comparative Example 4 Except that the amount of soft etching was set to 0.5 μm, the same procedure as in Example 1 was performed.

[0028]

[Table 1]Example Comparative example Processing conditions, measurement items & units 1 2 3 4 5 ^*  1 2 3 ^* 4 Soft etching amount (μm) 1.5 1.5 3 3 1.5 1.5 1.5 1.5 0.5 Pre-dip (min) 1 2 1 1 1 1 1 1 1 Black oxide (min) 3 4 3 2 3 3 3 3 3 Post-dip (min) 3 6 3 2 3-3 3 3Rust prevention treatment (min) 1 2 1 1 1---1 Halo size 1-500 hole 0 0 0 0 0 250 60 40 100 (μm) 1001-1500 hole 0 0 0 0 0 200 40 40 80 Inner layer adhesive strength (kg / cm) 1.3 1.2 1.4 1.4 1.4 0.3 1.2 1.2 1.0 * In Example 5 and Comparative Example 3, lamination molding was performed after being left for 7 days after the treatment.

[0029]

As described above, it is clear from the detailed description and the examples that the multilayer printed wiring board according to the processing method of the present invention can completely prevent the occurrence of halo or pink ring. The soft etching treatment of the present invention can be easily achieved by selecting the soft etching conditions, and the rust prevention treatment is only added to the existing steps. With a very simple change, a multilayer printed wiring board with improved reliability can be manufactured with good productivity, and its industrial significance is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuo Tanaka 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Examiner in the Tokyo Plant Takashi Nakagawa (56) References JP-A-2-230794 ( JP, A) JP-A-4-247692 (JP, A) JP-A-4-17395 (JP, A) JP-A-4-3334091 (JP, A) JP-A-5-160564 (JP, A) Hei 3-71516 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 3/38 H05K 3/46

Claims (5)

(57) [Claims] 1. A copper circuit provided on an inner layer circuit board is treated with an oxidizing alkaline aqueous solution to obtain a copper circuit of 30 to 60 mg / dm ^2.
After the formation of a copper oxide film, the oxide film on the surface of the copper circuit is dissolved and removed by 90 to 99% with an acidic chelate solution adjusted to pH 3.5 to 4.0, and further treated with a rust preventive solution. A method for treating an inner layer copper foil, comprising forming a rust preventive film on a copper circuit surface. 2. The method for treating an inner layer copper foil according to claim 1, wherein the surface of the copper circuit is soft-etched by 1.0 to 3.0 μm before oxidizing the copper circuit provided on the inner layer circuit board. 3. The method according to claim 1, wherein the treatment with the oxidizing alkaline aqueous solution is a two-stage treatment of an alkaline aqueous solution and an alkaline sodium chlorite aqueous solution. 4. The method for treating an inner copper foil according to claim 1, wherein the acidic chelate solution is a solution comprising ethylene dian tetraacetate and a mineral acid or an organic acid. 5. The rust preventive solution is 0.5 to 5 g / 1 (liter).
Benzotriazole aqueous solution at a processing temperature of 30 to 8
The method for treating an inner layer copper foil according to claim 1, wherein the immersion treatment is performed at 0 ° C for 0.5 to 5 minutes.