JP4610027B2 - Electrolytic copper plating solution for forming acicular crystals and method for forming acicular film - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to an electrolytic copper plating solution capable of forming a needle-like crystal coating and a method for forming a needle-like copper coating using the same, and more specifically, a uniform needle-like copper coating can be deposited on an object to be plated. It can be used to improve the adhesive strength of many metals and resins, including the adhesion of copper foil and resin on conductor circuits such as multilayer printed circuit boards and copper-clad laminates. The present invention relates to an electrolytic copper plating solution and a method for forming a needle-like copper film, and a plated product obtained by this method.
[0002]
[Prior art]
Conventionally, a multilayer printed circuit board prepares a copper clad laminate for an inner layer by processing a copper foil of a copper clad laminate to form a printed wiring, and this copper foil is subjected to surface pretreatment (generally following degreasing, After roughening with a soft etching treatment and activation treatment represented by ammonium persulfate, sodium persulfate, cupric chloride, sulfuric acid-hydrogen peroxide, etc., it is further represented by blackening treatment or brown treatment. In this process, a needle-like film of copper oxide or cuprous oxide is formed, and a copper-clad laminate or copper foil for outer layers is laminated on this copper-clad laminate for inner layers via a thermosetting resin-impregnated substrate (prepreg). It was manufactured as a multi-layer laminate having high adhesion by bonding.
[0003]
The multilayer laminate produced in this way needs to be energized to each layer. Therefore, it is necessary to make holes in the laminate and perform through-hole plating. Due to the penetration of the solution and the plating solution in the electroless copper plating step, the copper oxide or cuprous oxide film is dissolved, and pink rings (haloing) are generated.
[0004]
On the other hand, by forming a printed wiring using a copper clad laminate using a previously roughened copper foil, the multilayered printed circuit board is formed by omitting the roughening of the copper foil and the formation of an oxide film. However, according to this method, since the surface of the copper foil is roughened, there is a problem that the pattern accuracy of the printing etching resist and the etching resist by the ultraviolet baking method is inferior.
[0005]
In recent years, a method of utilizing a specific electroless copper plating method has been developed as a method for solving such drawbacks of the copper clad laminate and improving the adhesive strength (Japanese Patent Laid-Open Nos. 61-15980 and 61). -15981, 61-41775).
However, in the above electroless copper plating, formalin is indispensable as a reducing agent. This formalin has (1) abnormal precipitation of copper on the resin, (2) unstable bath, 3 There was a problem that the smell was strong and there was a risk of carcinogenicity.
[0006]
Recently, the present inventors have developed a method for forming a uniform needle-like copper film having excellent adhesion by electroless copper plating (Japanese Patent Laid-Open No. 4-116176, WO 97/46731). According to this technique, a copper-clad laminate having high adhesion without the above-mentioned drawbacks can be obtained, but it is basically electroless plating, the deposition rate is slow, and the life of the liquid is not so long. was there.
[0007]
[Problems to be solved by the invention]
Compared to electroless plating, electroplating has a faster film formation rate and easier bath management, so if a uniform needle-like copper film with excellent adhesion can be obtained by electroplating, technically, It is also very advantageous economically.
An object of the present invention is to satisfy such a demand and to provide a technique capable of obtaining a uniform needle-like copper coating having excellent adhesion by electroplating.
[0008]
[Means for Solving the Problems]
The present inventor has paid attention to an acidic copper plating bath having a high copper film deposition rate, and has been diligently examining the possibility of obtaining a uniform acicular crystal copper coating in this bath and the conditions thereof. The present inventors have found that a uniform needle-like copper film can be obtained by the presence of both a sulfur-based compound and the present invention.
[0009]
That is, the present invention provides an electrolytic copper plating solution for forming needle crystals, wherein a transition metal element and a sulfur compound are added to an acidic copper plating solution.
The present invention also provides a method for forming a needle-like copper film by electroplating an object to be plated in the above-mentioned electrolytic copper plating solution for forming a needle-like crystal, and a plated product obtained by this method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The electrolytic copper plating solution for forming needle crystals of the present invention (hereinafter referred to as “the copper plating solution of the present invention”) is prepared by adding both a transition metal element and a sulfur compound to a normal acidic copper plating solution. The
[0011]
Examples of the acidic copper plating solution used in the copper plating solution of the present invention include a copper sulfate plating solution and a copper pyrophosphate plating solution. Of these, the copper sulfate plating solution may have a composition in a generally used range, for example, 60 to 120 g / l as copper sulfate, 150 to 250 g / l as sulfuric acid, and hydrochloric acid at a concentration of about 30 to 100 ppm as chlorine ions. Can be used.
[0012]
Moreover, as a transition metal element added to this acidic copper plating solution, periodic table group VIII elements, such as nickel, cobalt, iron, etc. are mentioned. The amount of the transition metal element added varies depending on the type of metal, but in the case of a Group VIII element of the periodic table, it is preferably about 200 to 10,000 mg / l.
[0013]
Furthermore, examples of the sulfur compound added to the acidic copper plating solution include thiosulfate, thiosulfate such as sodium thiosulfate, potassium thiosulfate, calcium thiosulfate, iron thiosulfate, and copper potassium thiosulfate. The amount added is preferably about 100 to 10,000 mg / l.
[0014]
In addition to the transition metal elements and sulfur compounds described above, known additives such as brighteners and surfactants can be added to the copper plating solution of the present invention as long as the effects of the present invention are not impaired.
[0015]
Next, a method for forming a needle-like copper film using the copper plating solution of the present invention (hereinafter referred to as “the method of the present invention”) will be described.
[0016]
The method of the present invention can basically be carried out under substantially the same conditions as with conventional acidic copper plating solutions. That is, it can be carried out with air or stirring at a bath temperature of about 20 to 40 ° C. and a current density of about 0.1 to 5 A / dm ² .
[0017]
In order to obtain a target copper film having uniform needle-like crystals in the method of the present invention, a copper film having a thickness of about 0.2 μm or more is required, and the plating time is preferably set to 1 minute or more.
[0018]
Moreover, the apparatus and power supply required for implementation of the method of this invention can use the same thing as the conventional acidic copper plating.
[0019]
[Action]
The present invention was developed based on analysis of abnormal precipitation in electrolytic copper plating. That is, the formation of the acicular crystal plating film is a kind of abnormal precipitation and should be avoided to obtain a glossy film.
[0020]
On the other hand, in the plating method that replaces the roughening treatment, the precipitation of needle crystals, which are abnormal precipitation, is essential. And found a sulfur compound. That is, the present invention is characterized in that the value of abnormal precipitation that should be avoided is recognized from another viewpoint.
[0021]
【Example】
EXAMPLES Next, although an Example and a test example are given and this invention is demonstrated in more detail, this invention is not restrict | limited at all by these Examples.
[0022]
Example 1
Nickel sulfate 20 g / l and sodium thiosulfate 1.5 g / l were added to a copper sulfate plating solution for a substrate having the following composition to prepare the copper plating solution of the present invention. In this copper plating solution, electroplating was performed on a copper clad laminate (double-sided substrate; copper foil 18 μm). The plating conditions were a current density of 1 A / dm ² , a plating time of 1 to 5 minutes, and a bath temperature of 25 ° C. Similarly, electroplating was performed on a patterned substrate obtained by patterning the copper-clad laminate by a conventional method.
[0023]
When the surface state of both the obtained substrates was observed with an electron microscope, a copper film of needle-like crystals was precipitated by plating for 1 minute on both the copper-clad laminate double-sided substrate and the patterning substrate.
Also, the adhesion strength of the plating was confirmed by peeling the gum tape.
[0024]
(The present plating solution composition)
_{CuSO 4 · 5H 2 O 75g /} l
H ₂ SO ₄ 180 g / l
Cl ^- 60ppm
_{NiSO 4 · 6H 2 O 20g /} l
_{Na 2 S 2 O 3 · 5H} 2 O 1.5g / l
Brightener ^* 2ml / l
* Cu-Brite TH-MI (manufactured by Sugawara Eugleite Co., Ltd.)
[0025]
【The invention's effect】
According to the present invention, an acicular crystal plating film can be obtained in a short processing time and at a low cost.
The acicular crystal plating film obtained by the present invention can be advantageously used for adhesion between copper and resin, for example, circuit formation such as multilayer printed wiring boards, adhesion between copper foil and resin such as copper clad laminates, etc. it can.
more than

Claims (2)

An electrolytic copper plating solution for forming a needle crystal in which a transition metal element selected from nickel, cobalt or iron and thiosulfuric acid or a salt thereof are added to an acidic copper plating solution, wherein the addition amount of the transition metal element is 200 An electrolytic copper plating solution for forming needle crystals, characterized in that the amount of thiosulfuric acid or a salt thereof is from 100 to 10,000 mg / l. Electroplating in an acidic copper plating solution containing a transition metal element selected from 200 to 10,000 mg / l nickel, cobalt or iron and 100 to 10,000 mg / l thiosulfuric acid or a salt thereof A method for forming a needle-like copper film, comprising: