JPS6026692A - Electroplating method - Google Patents

Abstract

PURPOSE:To obtain electroplating having uniform thickness without increasing electric power consumption by disposing a current rectifying plate formed with many honeycomb-shaped through-holes opening to face a cathode and an anode in an electrolytic cell between said cathode and anode. CONSTITUTION:An electroplating device is constituted by providing oppositely a cathode 6 and an anode 7 in an electrolytic cell 4, circulating a plating cell 5 in said cell by a pump 11 and supplying air through a pipe 10. A current rectifying plate 1 having through-holes 2 consisting of honeycomb-shaped pipes 3 is disposed between the cathode 6 and anode 7 of such electroplating device. The above-mentioned through-holes 3 which open to face the cathode 6 and the anode 7 have <=20mm. individual size and <=90% porocity in orthogonal projection to the cathode 6. The length of the pipes 3 is >=1/3 the spacing between the electrodes. If such plate 1 is installed, uniform electroplating is accomplished without increasing the bath voltage and the cathode chamber and the anode chamber are separated, by which the formation of sludge is prevented.

Description

[Detailed description of the invention] This invention relates to a highly improved electroplating method.

Over the past few years, electroplating methods have been useful for manufacturing printed wiring boards that require precision from the viewpoint of technical excellence and labor saving, and various improvements have been made in this regard.

By the way, when manufacturing a printed wiring board, electroless plating is applied to an insulating substrate, and then electroplating is applied to form a circuit. One of the circuit forming methods is called the tenting method. There is a method of formation in which through-holes are formed in an insulating substrate, and the printed wiring board substrate, which is electroless plated on the entire surface, is used as a cathode and the entire surface is formed in an electrolytic bath. After electrolytic copper plating,
In this method, an etching resist is applied to both ends of the through hole and a portion that will become a circuit, a circuit is formed by etching, and the etching resist is removed to produce a printed wiring board.

By the way, when electroplating is performed on a printed wiring board substrate as described above, a large amount of electroplating is deposited on the edge of the substrate or near the entrance of the through hole (edge portion), making it difficult to form a plated film with a uniform thickness. It was difficult to obtain.

In order to overcome all of these drawbacks, attempts have been made to conduct electroplating by installing a rectifying plate in which circular holes are bored in a plastic insulating plate with a thickness of about 1 to 5 mm between the cathode and the anode. However, not only is the uniformity effect still low, but the electric resistance between the electrodes increases due to the parts other than the holes in the current rectifying plate, which requires increasing the bath voltage, resulting in increased power consumption. Moreover, because the cathode chamber and the anode chamber are divided and separated, there are unavoidable drawbacks and defects, such as a decrease in the rate of conversion to metal ions at the anode, and the generation of sludge.

In view of the current situation, the present invention provides a structure between a cathode and an anode in an electrolytic cell, which has an opening facing the cathode and anode, has an individual size of 20+ nm or less, and has a porosity that is an orthogonal projection onto the cathode. So 90
% or more, and the length is 1/3 or more of the electrode gap, by arranging a current rectifier plate with many honeycomb-shaped through holes and performing electroplating, electroplating with a uniform thickness can be achieved. The purpose of the present invention is to provide an electroplating method that can be performed without consuming power and without generating sludge, and the present invention will be described in detail below with reference to illustrated embodiments in which the present invention is applied to the manufacture of printed wiring boards. do.

In the figure, reference numeral 1 denotes a current rectifier plate having a large number of noricum-shaped through holes 2, and a collection of regular hexagonal columnar tubes 3 made of synthetic resin such as vinyl chloride resin (C honeycomb tube). ing. The length of the through hole 2 is 1 between the electrodes.
/3 or more, and its size (hexagon size) is 2
It is less than 0rtan, and the smaller the value within the manufacturing limitations, the more preferable it is. By configuring the shape of the through hole 2 as described above, the current flowing from the anode to the cathode can be effectively reduced, and the electroplating can be made to have a uniform thickness.

In addition, the proportion occupied by the through-holes of the current rectifier plate 10, that is, the porosity, needs to be 90% or more when orthogonally projected onto the cathode, thereby suppressing an increase in electroplating resistance and increasing the bath voltage. In addition, electroplating can be uniformly performed without any separation, and the generation of sludge can be completely prevented without separating the cathode chamber and the anode chamber.

The current rectifying plate 1 is arranged so that the electrolytic cell faces the electrolytic cell (eyeglasses) as shown in FIG. It is desirable that the distance between the current rectifier plate 1 and the cathode 6 be equal to or more than 20 m+n and equal to or less than 1/3 of the electrode distance.

In Figure 3, 8 is a support base for the current rectifier plate 1, and 9 is a support base for the current rectifying plate 1.
10 is an open end of a pipe for circulating the plating solution in the electrolytic cell 4; 10 is an open end of an air supplying vibrator for stirring the plating solution near the cathode; 11 is a pump for circulating the plating solution; 12
A plating liquid overflow reservoir, 13 indicates the direction of flow due to overflow of the plating liquid. Note that as the plating solution, for example, a copper birophosphate aqueous solution, a copper sulfate aqueous solution, etc. are used.

Printed wiring board substrate 2a, 6, 9.12 A/dm2 in which an insulating substrate having a through hole with a diameter of 1.0 mm is plated with electroless copper
When copper plating was performed at various plating speeds, the distribution of the copper plating film thickness on the board surface and the distribution of copper plating on the through-hole area were as follows. When using a current rectifier plate (
properties) were much more uniform than when not used (conventional method).

Table 1 Thickness distribution on the substrate surface cμm) Table 2 Thickness distribution inside the through hole As is clear from the above explanation, in the present invention, electroplating can be performed uniformly, and it is particularly suitable for manufacturing printed wiring boards. It is extremely effective when electroplating printed wiring board substrates that have been electrolessly plated to form circuits, and it also does not increase power consumption and prevents the generation of sludge. Excellent practical effects can be obtained.

[Brief explanation of the drawing]

The drawings show an example of a current rectifier plate, etc. for carrying out the present invention, and FIG. 1 is a front view of the current rectifier plate, FIG. 2 is a side view thereof, and FIG. 3 is a state in which the current rectifier plate is used. FIG. 1. Current rectifying plate 2: Through hole 3: Pipe 4. Electrolytic bath 5, plating solution 6: cathode 7: anode 8. Support stand 9, open end 10 of circulation vibrator: open end 11 of air supply pipe: pump 12 for plating liquid circulation, overflow reservoir 13: flow direction of overflow of plating liquid Patent applicant: Hitachi Chemical Co., Ltd. company

Claims (1)

[Claims] Between the cathode and anode in the electrolytic cell, there is an opening facing the cathode and anode, each diameter is 20 mm or less, the porosity is 90% or more in orthogonal projection to the cathode, and the length is An electroplating method characterized by arranging a current rectifier plate having a large number of honeycomb-shaped through holes in which the distance is 1/3 or more of the pole spacing.