JPH0674514B2 - Copper pyrophosphate aqueous solution for anisotropic plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an aqueous copper pyrophosphate solution for anisotropic plating. As shown in FIG. 1, the anisotropy K is the ratio of the elongation A ₁ of the plating in the direction parallel to the width (A ₀ ) of a surface to be plated to the elongation B _{1 in the} direction perpendicular to it. And the expression It is represented by. There is anisotropy when K> 1.

<Prior Art> Photolithography has been often used in the past for the production of precise printed circuit boards. In particular, by using the additive method, a circuit board having a high wiring density can be obtained, which is a considerably advantageous manufacturing method. Has been done.

However, since the value of the anisotropy K does not exceed 1 in the printed circuit board using this manufacturing method, it is difficult to manufacture a thick and fine pattern. For example, when plating a pattern arranged in a certain line shape, the line spacing of the pattern before plating is 100 μm, and if plating with a thickness of 50 μm is applied, the anisotropy K is 1 and the plating width is 50 μm.
It spreads by m and shorts out between the lines.

On the other hand, the present inventors have already proposed Japanese Patent Application No.
57-91590), it was clarified that the value of K is increased by increasing the current density of plating. Therefore, it has become possible to thickly plate a fine printed circuit board.

<Problems to be Solved by the Invention> However, in order to manufacture a printed circuit board having a finer pattern, it is desirable to increase the value of K.

<Means and Actions for Solving Problems> The inventors of the present invention have studied the composition conditions of the copper pyrophosphate plating solution in detail, and as a result, while maintaining the required copper physical properties and surface smoothness, K We have found a composition that can increase the value of.

That is, A. copper ion concentration [Cu ²⁺ ] 22 to 42 g /, B. pyrophosphate ion concentration [P ₂ O ₇ ^{4 −} ] / copper ion concentration [Cu
^2+] weight ratio 6.0 to 8.0, C. ammonia concentration [NH _3] 0.03~0.20mol /, D.2,5- dimercapto-1,3,4-thiadiazole or its salt 5.0 × 10 ^-7 ~2.0 × 10 ^-5 mol /, E.pH is 8.2 ～ 9.0.

In order to prepare the copper pyrophosphate aqueous solution of the present invention, potassium pyrophosphate and copper pyrophosphate are added to a commercially available copper pyrophosphate plating solution, and further ammonia water and a brightening agent for copper pyrophosphate plating are added to adjust the composition conditions described above. Alternatively, a method may be used in which potassium pyrophosphate and copper pyrophosphate are dissolved in water in predetermined amounts, and then ammonia water and a brightening agent for copper pyrophosphate plating are added.

Pyrophosphate ion P ₂ O ₇ ^{4-of the} copper pyrophosphate aqueous solution of the present invention
The value of the weight concentration ratio of copper ion to Cu ²⁺ is P ratio Is 6.0 to 8.0, preferably 6.0 to 7.8, more preferably
It is 6.3 to 7.5. When the P ratio is lower than 6.0, so-called clouding occurs. On the other hand, when it is higher than 8.0, the limiting current density becomes low and it becomes easy to burn.

The copper ion concentration [Cu ²⁺ ] is 22 to 42 g /, preferably
28-42 g /, more preferably 30-40 g /. When the copper ion concentration is lower than 22 g /, the limiting current density is low and it becomes easy to burn. If it is higher than 42g /, cloudiness will occur.

Furthermore, the ammonia concentration [NH ₃ ] is 0.03 to 0.20 mol /
, Preferably 0.05 to 0.20 mol /, more preferably 0.
It is from 08 to 0.16 mol /. When the ammonia concentration is lower than 0.03 mol /, the limiting current density decreases and the gloss range becomes narrow. If it is higher than 0.20mol /, hard and brittle copper is precipitated.

Furthermore, as a brightener, 2,5-dimercapto-1,3,4
-Thiadiazole or its salts are preferred. As its concentration, 5.0 × 10 ^-7 ~ 2.0 × 10 ^-5 mol /, preferably 5.0 × 10
^{-7 to} 6.5 × 10 ^-6 mol /, more preferably 5.0 × 10 ^{-7 to} 3.
4 × 10 ^-6 mol / is good.

The above chemicals are often used as brighteners, and may be reagents or commercially available as brighteners from plating solution manufacturers. It is generally said that the brightener selectively adheres to the convex portion of the copper plating surface to suppress the deposition of plated copper on that portion and relatively promotes the deposition of copper in the concave portion, thereby smoothing. It is being appreciated. If this is correct, it is presumed that the brightener has a negative effect on the anisotropy of plating. However, although the cause is not well understood, the anisotropy is higher than that of the matte bath when the brightener is in an area, particularly in a low concentration area,
In addition, the original effect of the brightening agent, that is, the surface smoothing effect is also functionally sufficient. When the additive concentration is 5.0 × 10 ^-7 mol / or less, the anisotropy does not improve. Further, at 2.0 × 10 ⁻⁵ mol / or more, the surface smoothness is improved, but the anisotropy decreases with the concentration of the brightener, and becomes equal to the anisotropy when a bath containing no brightener is used. The point of the present invention is to increase the anisotropy while maintaining the surface smoothness by adding a slight amount of a brightening agent.

Under the above compositional conditions, PH should be between 8.2 and 9.0, but if PH is lower than this, KOH is used, and if PH is higher, polyphosphoric acid or citric acid is commercially available from each plating solution manufacturer. The pH is adjusted to within the above range, and more preferably to pH 8.4 to 8.8.

When plating is performed using the copper pyrophosphate aqueous solution of the present invention, the current density of the cathode is 3 to 50 A / dm ² , preferably 5
~ 20A / dm ² is good.

Agitation is required, and air agitation, pump agitation, cathode oscillation, or a combination thereof may be used. For example, in the case of air agitation, the air flow rate is 0.01 to 1.0 M ³ / M ² minutes (per unit plating bath liquid area The volume of air flowing in one minute in a standard state) is preferable. The bath temperature during plating is preferably 50 to 60 ° C., as is generally done.

Any plating base may be used as long as it has conductivity.
For example, the metal may be copper, nickel, aluminum or the like.

There is no particular problem with other plating devices as long as they are commonly used.

<Examples> In order to further clarify the aspects of the present invention, examples will be described below, but the present invention is not limited to the following examples, and various modifications can be made.

Examples 1 to 4 Insulating polyimide film (trade name manufactured by DuPont; “Kapton”) having a thickness of 25 μm and copper foil with a thickness of 5 μm and phenol resin adhesive (trade name manufactured by Bostic Co .; “XA-564-
4 ”) to bond. Next, negative resist (trade name, manufactured by Eastman Kodak Co .; "Microresist 747-1
10cst ") is applied to the copper surface after drying so that the resist thickness becomes 3 to 5 μm, and after prebaking, it is exposed with a high pressure mercury lamp through a circuit pattern mask, and a developing solution (trade name of Eastman Kodak Co .; Developer ") and a rinse solution (trade name of" Eastman Kodak Co., Ltd .; "Microresistance"), and post-baked to form a resist in a circuit pattern. Then, the copper foil is removed by etching with a 50% ferric chloride solution.
Furthermore, a resist stripper (trade name of Nagase Kasei Co., Ltd .;
"J-100") is used to remove the resist on the copper foil.

As a result, film thickness 5μm, width 130μm, array pitch 200μm
The following linear pattern was obtained. Next, copper pyrophosphate plating solution (Harshaw Murata Co., Ltd. product name; "Pyrodon Conc")
Then, potassium pyrophosphate, copper pyrophosphate and water were added in appropriate amounts to adjust the composition to a copper ion concentration of 34 g /, Company P = 7, and then an appropriate amount of 28% concentration ammonia water was added to convert to ammonia. Brightness for copper pyrophosphate plating at a concentration of 0.08 mol / (Hershaw Murata brand name; “CP-
2 ") is added at 1.7 × 10 ^-1 mol / mol to adjust the pH of the prepared plating solution to 8.7, and then a pH adjusting solution (Hershaw Murata Co., Ltd.) is added. It was With this plating solution, the linear copper pattern is
The plating was performed under the conditions of 5.8 A / dm ² , air stirring 0.1 M ³ / M ² minutes, and bath temperature 55 ° C. As a result, high anisotropy was exhibited. Further, in Examples 2 to 4, as shown in Table 1, the copper ion concentration, P ratio,
Adjust ammonia concentration and brightener CP-2 concentration to further adjust pH
Using the plating bath adjusted to the above, a copper linear pattern similar to the above was plated under the same conditions. The results of measuring the thickness and width of the resulting pattern are shown in Table 1. In each case, the physical properties of copper were practically sufficient.

Comparative Examples 1 to 2 Insulating polyimide film (Dupont's trade name; “Kapton”) with a thickness of 25 μm and 5 μm thick copper foil with phenol resin adhesive (Bostik's trade name; “XA-564—
4 ”) to bond. Next, negative resist (trade name, manufactured by Eastman Kodak Co .; "Microresist 747-1
10cst ") is applied to the copper surface after drying so that the resist thickness becomes 3 to 5 μm, and after prebaking, it is exposed with a high pressure mercury lamp through a circuit pattern mask, and a developing solution (trade name of Eastman Kodak Co .; Developer ") and a rinse solution (trade name of" Eastman Kodak Co., Ltd .; "Microresistance"), and post-baked to form a resist in a circuit pattern. Then, the copper foil is removed by etching with a 50% ferric chloride solution. Further, the resist on the copper foil is removed by using a resist remover (trade name: "J-100" manufactured by Nagase Kasei Co., Ltd.).

As a result, film thickness 5μm, width 130μm, array pitch 200μm
The following linear pattern was obtained. Next, to the copper pyrophosphate plating solution (manufactured by Harshaw Murata Co., Ltd.), potassium pyrophosphate, copper pyrophosphate and water were added in appropriate amounts, and the composition was 34 g / copper ion concentration.
, P ratio = 7, and further add an appropriate amount of 28% concentration of ammonia water, and convert it into ammonia to a concentration of 0.08 mol /, and further brightener for copper pyrophosphate plating (Hershaw Murata brand name; CP-2 ") was added to adjust the concentration to 3.0 × 10 ^-5 mol / mol, and then the pH of the prepared plating solution was adjusted to 8.
A KOH 5% solution or a pH adjusting solution (manufactured by Hershaw Murata Co., Ltd.) was added so that it became 7.

Using such a plating solution, the above-mentioned linear copper pattern was plated under the conditions of a current density of 5.8 A / dm ² and air agitation of 0.1 M ³ / M ² minutes bath temperature of 55 ° C. Comparative Example 1 The results are shown in Table 1.

In addition, plating was performed in the same manner as in Comparative Example 1 except that a plating solution containing no brightening agent for copper pyrophosphate plating was used. The results are shown in Table 1. (Comparative example 2) <Effect> By using the aqueous solution of copper pyrophosphate composed of the constituent elements of the present application, it is possible to perform plating with high anisotropy K while maintaining a surface property that is functionally sufficient as an electronic component. It is possible to manufacture a printed circuit board having a thick fine pattern.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a printed circuit board. In the figure; 1 is plated copper, 2 is copper foil, 3 is an insulator, A ₀ is the width of the copper foil on the insulator, A ₁ is the line width of the plated copper formed on A ₀ , and B is A ₀ on the formed thickness of the plated copper, a is shows the growth in the direction parallel to the plating surface of the plating copper formed on a _0.

Claims (1)

[Claims] 1. A. Copper ion concentration [Cu ²⁺ ] 22 to 42 g /, B. Pyrophosphate ion concentration [P ₂ O ₇ ⁴ ] / copper ion concentration [Cu
^2+] weight ratio 6.0 to 8.0, C. ammonia concentration [NH _3] 0.03~0.20mol /, D.2,5--dimercapto-1,3,4-thiadiazole or its salt 5.0 × 10 ^-7 ~6.5 × 10 ^-6 mol /, copper pyrophosphate aqueous solution for anisotropic plating