JP3465016B2 - Method for improving adhesion of resin to copper surface and high adhesion electroless copper plating bath used for the method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the adhesiveness of a resin to a copper surface, and more specifically, the adhesiveness between a copper circuit and a resin such as prepreg required in a manufacturing process of an electronic circuit board or the like. And a non-electrolytic copper plating solution used therefor.

[0002]

2. Description of the Related Art In recent years, with the trend toward smaller size, lighter weight, higher speed, and higher performance of electronic devices, there is an increasing demand for thinning, multilayering and high density of printed wiring boards. In order to meet such demands, a build-up method is currently drawing attention, and an insulating layer and a conductor layer are stacked one by one and the layers are connected to each other in many cases to manufacture a multilayer wiring board.

Currently, in the manufacture of a multilayer wiring board, for example, a core material having copper circuits formed on both upper and lower surfaces is bonded and laminated with a copper foil through an adhesive sheet obtained by impregnating a glass cloth called prepreg with an epoxy resin adhesive. It is often performed by heating and pressurizing. Then, in this method, in order to secure the adhesion between the copper circuit and the prepreg and to prevent the phenomenon called haloing, the surface of the copper circuit formed on the core material is subjected to blackening treatment, reduction treatment, Cu treatment. -Ni-P
It has been performed that chemical conversion treatment such as plating is performed to replace the smooth copper circuit surface structure with irregularities such as needles.
The prepreg, which is an adhesive resin, digs into the uneven copper surface obtained in this way, and excellent anchorage between the copper surface and the resin was obtained due to the anchor effect.

Although the above treatment is effective for improving the adhesiveness and preventing haloing, it is becoming a problem when the printed wiring board is required to be smaller and have higher performance. That is, in order to achieve downsizing and high performance of the printed wiring board, it is necessary to form the circuit pattern with higher precision and higher density. If such a concave-convex structure is used, problems such as deterioration of circuit accuracy and variations will occur. Further, if there is a partial unevenness in the above-mentioned treatment, it may directly lead to defective adhesion, resulting in a defect of the entire printed wiring board. Especially in recent build-up methods, this problem is a particularly serious problem. In other words, the build-up method generally involves performing chemical conversion treatment on a copper circuit formed on a resin, forming an insulating resin on the copper circuit by coating, etc., and drying it to form a resin film layer, which is then electrolessly formed. A copper film is formed by copper plating or a combination of copper plating and electrolytic copper plating, and then circuit formation, chemical conversion treatment, and resin layer formation are sequentially repeated to form a multilayer printed wiring board. At this time, the copper circuit surface and the resin layer are formed. Ensuring adhesion with was a particular problem.

[0005]

[Problems to be Solved by the Invention]
If the same copper surface-resin adhesion as in the case of blackening treatment etc. is guaranteed, it becomes possible to form a more precise and higher density printed circuit, and it becomes smaller and higher in performance. It is possible to manufacture printed wiring boards. The present invention has been made from such a viewpoint, and an object thereof is to provide a method for improving the adhesiveness between a copper surface and a resin such as prepreg while keeping the copper surface smooth. Is.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have performed electroless copper plating containing a specific compound without changing the structure of the copper surface. The present invention has been completed by finding that the adhesiveness with a resin can be improved.

That is, the present invention provides a method for improving the adhesion of a resin to a copper surface, which comprises immersing the copper coating in an electroless copper plating bath containing a sulfur compound.

The present invention also provides a highly adhesive electroless copper plating bath containing copper ions, a copper ion complexing agent, formaldehyde or its derivative as a reducing agent, and a sulfur compound.

[0009]

The sulfur compounds added to the electroless copper plating bath used in the method of the present invention include sulfur sulfides such as sodium sulfide, ammonium sulfide, calcium sulfide, lithium sulfide, sodium hydrogen sulfide and ammonium hydrogen sulfide. Inorganic compounds, thiocyan compounds such as potassium thiocyanate and ammonium thiocyanate, 2-mercaptobenzothiazole, thiomalic acid, thiocyanuric acid,
Examples include sulfurized organic compounds such as thioglycolic acid. These sulfur compounds were added to the electroless copper plating bath in an amount of 0.
It is preferable to add about 01 to 50 mg / l, and it is particularly preferable to add about 0.1 to 1 mg / l.

In order to carry out the method of the present invention, a copper foil or a copper film which has been subjected to ordinary electroless copper plating or electrolytic copper plating may be immersed in an electroless copper plating bath containing the above sulfur compound.

The electroless copper plating bath to which the above-mentioned sulfur compound is added is not particularly limited, and an ordinary electroless copper plating bath may be used. However, electroless copper plating using formaldehyde or its derivative as a reducing agent. A bath is preferred.

In this electroless copper plating bath, formaldehyde as a reducing agent, hypophosphite and DMAB are used.
In addition to their derivatives and the like, copper sulfate as a copper ion source, cupric chloride, copper nitrate, etc., and as a complexing agent for copper ions, EDTA, tartaric acid, malic acid, citric acid, quadrol, glycine, etc. Those salts can be used. The blending amount of these may be about the same as in the conventional electroless copper plating bath using formaldehyde.

The dipping conditions in the electroless copper plating bath are not particularly limited, but dipping at a temperature of about 50 to 70 ° C. for about 5 to 30 minutes is sufficient.

The following are examples of preferable pretreatments for the electroless copper plating treatment according to the present invention. [Basic operation step] Alkaline degreasing step (50 to 70 ° C; 3 to 10 minutes) ↓ Soft etching step (20 to 30 ° C; 1 to 5 minutes) ↓ Acid activity step (20 to 30 ° C; 1) ~ 5 minutes) ↓ Electroless copper plating step Note) In the above, washing with water is performed between the steps.

Although the adhesion between the copper coating and the resin can be improved by the above method, in order to obtain higher adhesion, the electroless copper plating coating obtained as described above is treated with a sulfur-containing compound solution. It is preferable to immerse in.

The sulfur-containing compound used here is selected from sulfurized inorganic compounds, thiosulfuric acid or salts thereof, thiocyanic acid or salts thereof, and sulfurized organic compounds.
Of these, as the sulfide inorganic compound, sodium sulfide,
Examples thereof include calcium sulfide, ammonium sulfide and the like, polysulfides thereof, sodium hydrogen sulfide, calcium hydrogen sulfide, ammonium hydrogen sulfide, etc., and salts of thiosulfates and thiocyanates include alkali metal salts such as sodium and potassium. Etc. Examples of the sulfurized organic compound include 2-mercaptobenzothiazole, thiomalic acid, thiocyanuric acid, and thioglycolic acid.

As the solvent for dissolving the sulfur-containing compound,
Water is used, and the concentration of sulfur-containing compound after dissolution is 0.0
It is desirable to set it to about 1 to 50 mg / l.

It is sufficient that the copper film is immersed at a temperature of about 20 to 50 ° C. for about 1 to 5 minutes.

By doing so, the adhesion between the resin and the resin can be improved without changing the structure of the copper film, and it can be advantageously used when high adhesion between the copper film and the resin is required. . In particular, the method of the present invention is useful for forming a precise and fine circuit as compared with the conventional adhesion improving method.

[0020]

Although the reason why the adhesion between the copper plating film and the resin is improved by the method of the present invention has not always been clarified, the sulfur compound contained in the electroless copper plating is codeposited in the copper film. However, it is presumed that this will increase the adhesiveness by reacting with the epoxy groups in the adhesive resin.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Adhesion test with resin: commercially available double-sided copper clad plate (5 × 10 c
m) was pretreated in the following steps and conditions, and then immersed in an electroless copper plating bath having the following composition containing a sulfur compound as an additive. After dipping, each sample was washed with water and dried, and then 500 μm of epoxy resin (manufactured by Hitachi Chemical Co., Ltd.)
It was applied in a thickness of m. After drying at 70 ° C. for 30 minutes, the adhesive strength of each sample was examined by a 90 ° peeling test described below. The results are also shown in Table 1.

[Pre-treatment process] Alkali degreasing ^* (60 ° C, 5 minutes) ↓ Soft etching ^** (room temperature, 2 minutes) ↓ Acid activity ⁺ (room temperature, 2 minutes) * OP-144 (Ebara Eugelite) Co., Ltd.) ** PERPOSIT ETCH 748 (Shipley Far East Co., Ltd.) + 10% -H ₂ SO ₄

[Electroless copper plating] Electroless plating bath composition Copper sulfate pentahydrate 0.03M EDTA / tetrahydrate 0.24M Formalin 0.2M Dipyridyl 10ppm Additive (Table 1) Electroless plating conditions Bath temperature 60 ℃ pH 12.5 Immersion time 15 minutes

[90 ° peeling test] A copper end of a sample in which a knife was inserted in a width of 10 mm was vertically peeled off by an Instron tester at a crosshead speed of 3 mm / sec. The state of the peeled surface of the resin or copper foil was also observed with a scanning electron microscope (SEM).

[0026]

[Table 1]

As is clear from this result, the adhesiveness of the copper film treated by the electroless copper plating containing the sulfur compound with the resin was obviously higher than that in the case where it was not contained.

Example 2 Hand Heat Resistance Test: Each sample of Example 1 was subjected to a solder heat resistance test as follows. That is, each sample was floated in a solder bath heated to 260 ° C., and the time until the occurrence of blistering of the resin was measured as the heat-resistant time. The results are shown in Table 2.

[0029]

[Table 2]

From these results, it was revealed that the heat resistance and adhesion of the copper film treated by the electroless copper plating containing a sulfur compound to the resin are higher than those not containing it.

[0031]

EFFECTS OF THE INVENTION According to the method of the present invention, it is possible to improve the adhesiveness with a resin without forming irregularities on the surface of the copper film, which is advantageous when high adhesiveness between the copper film and the resin is required. In particular, it is extremely useful for forming a printed circuit board having a small size and high performance, which is capable of forming a precise and high-density printed circuit. that's all

─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideomi Takahashi 4834 Rokuura-machi, Kanazawa-ku, Yokohama-shi, Kanagawa Kanto Gakuin University (72) Inventor Hidefumi Nagata 4834, Rokuura-cho, Kanazawa-ku, Yokohama, Kanagawa (72) Inventor Isamu Mochizuki 4834 Rokuura-cho, Kanazawa-ku, Yokohama-shi, Kanagawa, Kanto Gakuin University (72) Inventor Ken Kobayashi 4834 Rokuura-cho, Kanazawa-ku, Yokohama, Kanagawa (56) Reference Japanese Patent Laid-Open No. 3-215699 (JP) , A) JP-A-6-306622 (JP, A) JP-A-8-209354 (JP, A) JP-A-4-192218 (JP, A) JP-A 61-153281 (JP, A) JP-A 59-23862 (JP, A) JP-B 3-76599 (JP, B2) JP-B 7-37113 (JP, B2) JP-B 4-55550 (JP, B2) Journal of Japan Institute of Electronics Packaging, Vol. 1, No. 1, PP. 66-69 (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 18/40

Claims (4)

(57) [Claims] 1. A copper foil or an ordinary electroless copper foil
Form an electroless copper plating film by immersing a copper film that has been plated with copper or electrolytic copper in an electroless copper plating bath containing a sulfur compound
And the adhesion improving method of the resin to the copper surface, wherein Rukoto to bond the copper surface and resin. 2. The method for improving the adhesion of a resin to a copper surface according to claim 1, wherein the sulfur compound is a metal sulfide compound, a thiocyanate compound or a sulfurized organic compound. Wherein the electroless copper plating bath, formaldehyde <br/> or claim first is for the derivative with a reducing agent
Item 3. A method for improving the adhesiveness of a resin to the copper surface according to item 2 or item 2. 4. A method according to any one of claims 1 to 3.
It is used in the method for improving the adhesion of resin to the copper surface described in paragraph
That, copper ions, a complexing agent for copper ions, including formaldehyde or a derivative thereof and a sulfur compound as the reducing agent No No
Electrolytic copper plating bath.