SU1157146A1 - Method of copper electroplating and simultaneous removal of admixtures from electrolyte - Google Patents

Abstract

THE METHOD OF GALVANICAL COPPERING AND SIMULTANEOUS CLEANING OF ELECTROLYTE FROM IMPURITIES by passing current through the cathode and the anode separately at the copper-plating stage and through the anode and additional electrode at the purification stage, which is tallerted by the fact that the copper stages pass a constant current, and at the cleaning stage a periodic alternating current of different polarity with the same half-period form.

Description

: l VI

Ed 11 The invention relates to the electrolytic deposition of metallic coatings, mainly to the purification of electroplating plating of printed circuit boards from metallic and organic impurities that accumulate in the working solution during the production process. There are known methods for the purification of electrolytes from organic impurities during the deposition of metals on printed circuit boards by treatment with activated carbon or hydrogen peroxide 1D. The disadvantages of these methods are the impossibility of continuous cleaning in the working bath and the impossibility of extracting inorganic impurities. The closest to the invention with the technical essence and the achieved result is the method of galvanic copper plating and simultaneous purification of the electrolyte from impurities, mainly including separate current passing at the copper plating stage and the cleaning stage when using an additional electrode of the cathode cathode. the ratio of forward and reverse pulses is 2: 1, the forward pulse is passed through the main cathode and the anode, and the reverse pulse through the additional cathode and the main cathode, which at this stage works as the anode 2J. The disadvantages of this method are the precipitation of a significant amount of metal with impurities at the additional cathode, as well as the insufficient efficiency of extracting organic impurities that deteriorate the quality of the deposited metals as they accumulate in the electrolyte. The purpose of the invention is to reduce the sweat of the deposited metal in the process of electrochemical cleaning and increase the efficiency of electrolyte purification from impurities. This goal is achieved by the method of electroplating and simultaneous purification of electrolyte from impurities by separately passing current through the cathode and anode at the copper plating stage and through the anode and additional electrode - cathode at the purification stage, at the copper plating stage they pass DC and cleaning periodic alternating current of different polarity with the same half-cycle form. Periodic current can be applied in any form (rectangular, sawtooth, sinusoidal, etc.) with equal half periods. Technologically, the most appropriate use of a periodic current of sinusoidal form, for example, alternating current of an industrial frequency of 50 Hz. According to the method, in one bath, the process of metal deposition, in this case copper, is carried out, simultaneously cleaning the electrolyte from impurities by using an additional mesh electrode. In the positive period, the additional electrode is the cathode on which copper is deposited. Together with copper, metallic impurities are deposited on the same electrode, including those in the voltage range to the left of copper. Simultaneously with the electrochemical processes, the organic molecules in the electrolyte are adsorbed on the surface of the additional electrode. Copper electrolytes in the production of printed circuit boards are usually contaminated with organic photoresist components of printed circuit boards, such as benzophenone, Michler's ketone, and oligoether acrylate. These organic compounds have a dipole moment, which allows them to form complexes with copper ions with a positive charge. In the cathode half-period, such a complex molecule is discharged on the electrode surface, which improves the efficiency of organic matter incorporation into the cathode sediment due to specific adsorption. In the anodic half-period, the dissolution of copper from an additional electrode occurs predominantly in areas not blocked by organic impurities, which is more energetically favorable. As the growth and the amount of organic molecules adsorbed and incorporated into the sediment increase, they decrease in solution. Alternating deposition and dissolution of the metal leads to an increase in the copper layer on the additional electrode with a high concentration of organic impurities, which ultimately reduces the loss of the anode metal and increases the cleaning efficiency. The ratio of the rates of deposition and dissolution of the additional electrode is determined by the shape of the current used for cleaning, and the anode used in the electroplating process, the shape of the current used for deposition of the metal on the printed circuit boards. Example 1. In a galvanic bath with copper sulfate electrolyte containing 150 g / l CuSO and 100 g / l. they carry out simultaneous galvanic copper plating of printed circuit board blanks and purify the electrolyte from impurities by a periodic current of variable polarity with a frequency of 50 Hz. The effective value of the current in the positive half-period is twice as much as in the negative and is 1.32 A. A separate transmission of the direct and reverse pulses through the anode and the additional cathode is provided. The amount of electricity passed is 5 A / h per liter of electrolyte. This mode provides cleaning from inorganic impurities. Data on the quality of the precipitation is given in table. 1. Example 2. In a galvanic bath with the composition as in Example 1, a simultaneous galvanic copper plating of PCB blanks with a constant current of 6A is carried out and the electrolyte is cleaned from impurities with a periodic current with equal half-periods with a frequency of 50 Hz. The effective value of the periodic current is 1 A. The current output of the metal at the additional cathode is 1%, which ensures the maximum reduction of metal losses and the highest efficiency of electrolyte cleaning from impurities. The proposed method is applicable to other types of copper electrolytes. The results of the study are shown in Table. 2. The economic effect of using the invention can be obtained by reducing the loss of metal deposited in the electroplating process by 5-7%, increasing the yield of usable products by 2-3% and increasing the efficiency of using electroplating baths by 1.5-2% . Table 1

0.66

42.6 1.0 0.9

5 0.17

20 30

1.83 1.79

1.0

1.0 1.0 1.0 1.0 1.0

.Table 2

thirty

1.79

28-30

1.78

1.80

thirty

Claims (1)

METHOD OF GALVANIC COPPER AND SIMULTANEOUS CLEANING OF ELECTROLYTE FROM IMPURITIES by separately passing the current through the cathode and anode at the copper stage and through the anode and additional electrode, the cathode at the cleaning stage, which means that, in order to reduce metal losses and increase the cleaning efficiency, the copper plating stages allow direct current to pass through, while the cleaning stage passes periodic alternating current of different polarity with the same half-cycle shape.