JPH04139787A - Electroplating method of printed wiring board - Google Patents

Abstract

PURPOSE:To prevent abnormal deposition of an electroplated copper layer, by detecting each addition concentration of a plurality of additives, and independently adding each additive to plating solution, on the basis of the detected data and according to characteristics necessary for the electroplating layer of a printed board. CONSTITUTION:In an electroplating process, additive is analyzed by analyzing apparatuses 13, 15 which can selectively analyze the concentration of each additive so as to correspond with each additive, and insufficient additive is independently supplied to copper electroplating solution 1, in the state that mixing is not generated. In 1l of the copper electroplating solution 1 whose main component is copper sulfate, the concentration of carrier additive 12 is 10-30ml, that of brightener additive 11 is 0.4-0.7ml, and that of leveler additive 14 is 0.5-1.0ml. By using the copper electroplating solution 1 wherein three kinds of additives which are not mixed are independently added to plating solution in the above-mentioned manner, and by using a copper electrode containing phosphorus as an anode 2, a printed wiring board 3 whose aspect ratio is 15 is subjected to copper electroplating.

Description

[Detailed Description of the Invention] [Summary] Regarding the electrolytic copper plating method for printed wiring boards, in order to improve the throwing power when electrolytically copper plating printed wiring boards with a high aspect ratio, a long period of time is required at low current density. Aiming at an electrolytic copper plating method that produces a smooth and dense plating layer without causing pits in the resulting coating layer, several additives made of organic substances are added. A printed wiring board to be electrolytically plated is immersed in an electrolytic plating solution containing metal ions, and a voltage is applied between the printed wiring board and the electrodes immersed in the electrolytic plating solution. In the electrolytic plating method for depositing metal ions on the printed wiring board, a plurality of additives made of organic substances are added to the electrolytic plating solution, and the concentration of each of the plurality of additives is determined separately. A predetermined amount of each additive is added to the electrolytic plating solution according to the required characteristics of the electrolytic plating layer of the printed wiring board based on the detection information detected by an analytical device capable of selective detection. The components are added without being mixed separately.

[Industrial application field] The present invention relates to a method for electrolytic copper plating of printed wiring boards.

In recent years, printed wiring boards used in the electronic circuit configuration of high-speed computers are required to form electronic circuits with high density, and for this reason, many inner layer conductors are laminated and the diameter of through holes is made fine. There is a trend in which printed wiring boards with a high aspect ratio (through-hole diameter/printed wiring board thickness) are required.

[Prior Art] A conventional method for electrolytic copper plating on such a printed wiring board is shown in FIG. This electrolytic copper method No. 1
Table 1 shows the composition of electrolytic copper coating solution 1 used in the method shown in Table 7.

In this table, additives are chemicals composed of organic compounds,
Usually commercially available products are mixtures of polymeric compounds such as surfactants, sulfur-based organic compounds, etc. in appropriate proportions, and for example, improve the gloss of the deposited surface of the electrolytic copper plating layer. As such, a product such as Kabalacid GS (manufactured by Schering Co., Ltd., trade name: Kabalacid GS) is used as such an additive.

Further, the amount of chlorine ions in this electrolytic copper plating solution is, for example, when an aqueous solution of hydrochloric acid containing chlorine ions is added, the amount of the aqueous solution of hydrochloric acid is converted into the amount of chlorine ions.

The electrolytic plating conditions when performing electrolytic copper plating on a printed wiring board using such an electrolytic copper plating solution will be explained using Table 2.

As shown in Table 2 and Figure 4 above, the anode 2 is a phosphorous-containing copper plate or a spherical phosphorus-containing steel, and the phosphorus content is 0.
．． The content is controlled at 0.02 to 0.08% by weight.

Then, the printed wiring board 3 to be electrolytically plated is used as a cathode,
A second component added to the electrolytic copper coating solution 1.
The content of the additive 4 that appears is detected by an analyzer 5 using a circulating current voltage method (CVS method), and electrolytic copper plating is performed while replenishing the additive based on the detected information.

[Problem to be solved by the invention]

However, in recent years, printed wiring boards used in the electronic circuits that make up high-speed computers are required to have a high aspect ratio, and even in such products, it is necessary to ensure that the thickness of the electrolytic copper plating layer is uniform. There is a demand for a product that is large and dense, does not cause out-of-focus, and has a glossy plating layer.

Therefore, in order to obtain a plating layer with a uniform thickness even in the electrolytic copper plating layer in the through holes of the printed wiring board, the current density of the current flowing between the printed wiring board and the anode during electrolytic copper plating is reduced. It has been practiced to perform electrolytic copper plating for a long time.

However, when electrolytic copper plating is performed at such a low current density for such a long period of time, there is a problem in that the anode becomes overvoltage and additives added to the electrolytic copper plating solution are oxidized and decomposed.

As a result of the oxidative decomposition of this additive, the electrolytic copper plating layer 7 within the through hole 6 becomes a lump-shaped deposited film called nodule plating, as shown in FIG. 5(a).
As shown in Figure (b), when patterned copper plating is performed by coating the printed wiring board 3 with the resist film 8 in a predetermined pattern, out-gross occurs when the plating layer is abnormally deposited along the boundary surface 8A of the resist film 8. There is an outbreak. Further, as shown in FIG. 5(C), the plating layer on the surface of the patterned electrolytic copper plating formed has a concave concave focus 9.

If such an electrolytic copper plating layer is abnormally deposited, it rarely occurs when the electrolytic copper plating solution is prepared and the plating solution is new, but if the electrolytic copper plating solution is used for a long time, Deterioration was observed, and in a printed wiring board with a current density of 0.5 A/C1 m'' during electrolytic copper plating, a pattern width of 70 μm, and an aspect ratio of 15, I
When operating for 1 hour with OA current, that is, l0AH/j!
Abnormal precipitation is observed at this stage.

As a result of various experiments, the inventors have found that the above-mentioned abnormal precipitation of the electrolytic copper plating layer is caused by using the electrolytic copper plating solution for a long time, that is, by electrolytic copper plating for a long time at a low current density. It has been found that in some cases, the organic compound constituting the additive undergoes oxidative decomposition and products of components other than the organic compound are generated in the electrolytic copper plating solution.

The present invention solves the above-mentioned problems and provides electrolytic copper that prevents abnormal precipitation of the electrolytic copper plating layer even when electrolytic copper plating is performed on a printed wiring board with a high aspect ratio at a low flow density for a long time. The purpose is to provide a plating method.

[Means to solve the problem]

The electrolytic copper plating method for a printed wiring board of the present invention which achieves the above object includes immersing the printed wiring board to be electrolytically plated in an electrolytic plating solution containing metal ions to which a plurality of additives made of organic substances are added. In an electrolytic plating method in which a voltage is applied between a printed wiring board and an electrode immersed in the electrolytic plating solution, metal ions in the electrolytic plating solution are deposited on the printed wiring board, the electrolytic plating solution A plurality of additives made of organic substances added thereto are individually detected by an analytical device capable of selectively detecting the concentration of each of the plurality of additives, and based on the detected information, the printed wiring board is According to the required characteristics of the electrolytic plating layer, a predetermined amount of each additive is added to the electrolytic plating solution without being mixed separately.

In addition, each of the additives mentioned above is a carrier additive that prevents pits in the electrolytic plated layer, a brightener additive that imparts density to the electrolytic plated layer, and a leveler additive that imparts smoothness to the electrolytic plated layer. This is a characteristic feature.

Furthermore, in the electrolytic copper plating 11, the content of the carrier additive is 1O~30~! , leveler additive content is 0.4
~0.7 mjl! , the brightener additive content is 0.
5-1. It is characterized by Oa+A.

[For production]

The organic compound additive added to the electrolytic copper plating solution mentioned above consists of a surfactant, a carrier additive that has the function of preventing pits from occurring on the surface of the electrolytic copper plating layer, and a sulfur containing sulfur. A brightener additive which is made of an organic compound and has the function of making the coating of the plating layer dense and glossy, and a leveler additive which is made of an organic compound and has the function of smoothing the coating of the plating layer. A product is used that is mixed in a predetermined amount.

By the way, when additives with different functions are mixed and added to the electrolytic copper plating solution, each additive has a different lifespan, so if the carrier additive is consumed during electrolytic copper plating, the carrier additive's lifespan is different. This results in the inconvenience that the function is lost and pits are formed in the formed plating layer.

Therefore, in the present invention, the above additives are analyzed in the electrolytic plating process using an analytical instrument that can selectively analyze the concentration of each additive, and the missing additives are removed. They are supplied into the electrolytic copper plating solution without being mixed separately.

In this way, the additives in the electrolytic copper plating solution can be added to the electrolytic solution in the necessary amount to satisfy their functions, so there is no shortage of additives in the electrolytic solution. , a smooth electrolytic copper plating layer that is always stable, free of pits, and dense and has good gloss can be obtained.

〔Example〕

Table 3 shows the composition of the electrolytic copper plating solution used in the method of the present invention.

Table 3 In the electrolytic copper plating solution 11 containing copper sulfate as a main component, the concentration of the carrier additive is 10 to 30mf, the concentration of the brightener additive is 0.4 to 0.1val, and the concentration of the leveler additive is 0.5mf.
5-1. On/! Added. This carrier additive is a surfactant manufactured by Schering Co., Ltd. and has the trade name: Hetting.
Agent Kabalaside) IL-G-40, and the brightener additive is manufactured by Schering Co., brand name: Bright.
nerR Kabalaside HL-G ・40, the leveler additive is manufactured by Schering and has the trade name: Ba5ic Le.
Veller Kabalacid HL-G 40.

As shown in FIG. 1, the above-mentioned phosphorus-containing steel electrode was formed using the electrolytic copper plating solution 1 in which the three types of additives were added separately to the electrolytic copper plating solution without mixing them. Anode 2
When a printed wiring board 3 with an aspect ratio of 15 was plated using electrolytic copper, the operation of the electrolytic copper plating solution was 5.
0 to 80 A) l/f, and compared to the conventional case in which the above-mentioned additives were added to the plating solution in a pre-mixed state, the life span was increased by 5 to 8 times.

In this way, by mixing additives with each function within the range shown in Table 3 per 1 liter of the electrolytic copper plating solution, the life of the electrolytic copper plating solution can be increased by 5 to 8 times as in the present invention. However, when the additive content deviated from the range shown in Table 3 above, an electrolytic copper plating solution with the above characteristics could not be obtained.

Furthermore, the present inventors conducted an experiment to confirm the above.

First, add 40 g/f of copper sulfate, 300 g/l of sulfuric acid, and chlorine ions of chlorine to 1 liter of electrolytic copper plating solution so that the amount of each chemical is within the range of the amount of each chemical shown in Table 3 above. The content is 30Il1g/l, the amount of carrier added is 20mIl/1, and the amount of brightener added is 0゜6++l/i! Mix to prepare an electrolytic copper plating solution, adjust the amount of leveler added as shown in Figure 2, set the temperature of the electrolyte to 22°C, and place a printed wiring board with an aspect ratio of 15 in it. Electrolytic copper plating was performed at a current density of .5^/da''.

As shown in Figure 2, the amount of leveler added is 0.7
ral/l~1. Throwing properties were 80% or less outside the Ovg l/1 range.

Furthermore, in order to keep the electrolytic copper plating solution within the mixing amounts of each chemical shown in Table 3 above, copper sulfate was added to the electrolytic copper plating solution Il at 40 g/l and sulfuric acid was added at 300 g/l. , the chlorine ion content is 3Orag/l, the amount of carrier added is 2Orag/1, and the amount of leveler added is 0.6
An electrolytic copper plating solution was prepared by mixing ml/l, and the amount of brightener added was varied as shown in Figure 3, and a printed wiring board with an aspect ratio of 15 was coated with a current density of 0.3 A/l. Electrolytic copper plating was performed using DM.

As shown in FIG. 3, the amount of brightener added is 1.
If it is 0IIl/1 or more, the operation amount of the electrolytic copper plating solution, that is, the amount of current applied, will be shortened, and the amount of brightener added will be 0.
．． If it is less than 5a+l/1, a phenomenon such as clouding of the electrolytic copper plating layer will occur and the density of the plating layer will be impaired, so the amount of brightener added should be 0.5 to 1.0+l/1.
The range of l is optimal.

Furthermore, if the amount of carrier added is less than 1 l/j2 in the mixing amount of the chemicals shown in Table 3 above, many pits will occur on the surface of the plating layer, and if it is more than 30 ra 1, the plating layer will become cloudy. The result was that the gloss of the electroplated layer deteriorated.

Among the above additives, the concentration of carrier additives, brightener additives, and leveler additives can be analyzed by the circulating current voltage method (CVS method). The concentration of additives can be selectively analyzed only by high performance liquid chromatography (HPLC).

The machining 11 was carried out using an analytical instrument 5 using the circulating current voltage method (CVS method), the carrier additive 12 was carried out using an analytical instrument 13 using the polarography method, and the leveler additive 14 was carried out using a high performance liquid chromatography method (HPLC method). The concentration of each additive in the electrolytic copper plating solution is measured using an analytical device 15 that can selectively measure the concentration of each additive.

Then, detect the amount of each additive in the electrolytic copper plating solution,
When appropriate amounts of each of the above additives are added separately based on the detected values, a dense, smooth, and high-quality electrolytic copper plating layer that does not generate pits can be formed on high aspect ratio printed wiring boards at low current density. Even when electrolytic copper plating is performed for hours, it can be obtained stably.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a high quality electrolytic copper plating layer can be obtained even when electrolytic copper plating is performed for a long time at a low current density on a printed wiring board with a high aspect ratio. There is.

[Brief explanation of drawings]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is a relation diagram between leveler addition amount and throwing property, Fig. 3 is a relation diagram between brightener addition amount and operating amount of electrolytic copper plating solution, and Fig. 4 The figure is an explanatory diagram of a conventional method, and FIG. 5 is a diagram of an inconvenient state in the conventional method. In the figure, 1 is an electrolytic copper plating solution, 2 is an anode, 3 is a printed wiring board,
5.13.15 is an analytical instrument, 11 is a brightener additive, 12 is a carrier additive, and 14 is a leveler additive. And Belapina is -1 ("'Ukamaun table-i At-1/J2 1/4 draw tro wound (G) (C)

Claims (3)

[Claims] (1) Multiple additives made of organic substances (11, 12, 14
), the printed wiring board (3) to be electrolytically plated is immersed in the electrolytic plating solution (1) containing metal ions, and the printed wiring board (3) and the electrolytic plating solution (1) are immersed in the electrolytic plating solution (1). In an electrolytic plating method in which a voltage is applied between the immersed electrodes (2) and metal ions in the electrolytic plating solution (1) are deposited on the printed wiring board (3), adding to the electrolytic plating solution A plurality of additives (11, 12,
14) with analytical equipment (5, 13, 15) capable of selectively detecting the concentration of each of the plurality of additives separately.
), and based on the detection information, a predetermined amount of each additive (11, 12, 1
4) is added without being mixed separately. (2) Each of the plurality of additives (11, 12, 14) is a carrier additive (1) that prevents pits in the electroplated layer.
2) Claim (1) characterized in that the present invention comprises a brightener additive (11) that imparts density to the electrolytic plated layer, and a leveler additive (14) that imparts smoothness to the electrolytic plated layer.
Electrolytic plating method for printed wiring boards described. (3) Per 1 liter of the electrolytic copper plating solution, the content of the carrier additive (12) is 10 to 30 ml, and the content of the leveler additive (
According to claim (1) or (2), the content of the brightener additive (14) is 0.4 to 0.7 ml, and the content of the brightener additive (11) is 0.5 to 1.0 ml. Electrolytic plating method for printed wiring boards described.