Precision PCB Fabrication, High-Frequency PCB, High-Speed PCB, Standard PCB, Multilayer PCB and PCB Assembly.
The most reliable PCB & PCBA custom service factory.
Detailed explanation of the horizontal electroplating line process for high-precision multilayer circuit boards
With the rapid development of microelectronics technology, the manufacturing of printed circuit boards(high-precision multi-layer circuit boards) is developing in the direction of multilayer, layered, functional and integrated, which makes the manufacturing technology of printed circuit boards more difficult. The conventional vertical electroplating process cannot meet the technical requirements for high-quality and high-reliability interconnection holes, so horizontal electroplating technology is produced. This article analyzes and evaluates the horizontal electroplating technology from the principle of horizontal electroplating, the basic structure of the horizontal electroplating system, and the development advantages of horizontal electroplating. It is a great development and progress.
1. Overview
With the rapid development of microelectronics technology, the manufacturing of printed circuit boards(high-precision multi-layer circuit boards) is developing rapidly in the direction of multilayer, layered, functional and integrated. Promote printed circuit design to adopt a large number of small holes, narrow spacing, and thin wires for circuit pattern conception and design, making printed circuit boards (high-precision multi-layer circuit boards) more difficult to manufacture, especially multi-layer circuit boards (high The aspect ratio of the through holes of precision multilayer circuit boards exceeds 5:1 and the deep blind holes that are widely used in laminates make the conventional vertical electroplating process unable to meet the technical requirements for high-quality and high-reliability interconnection holes. The main reason is to analyze the current distribution state from the principle of electroplating. Through actual electroplating, it is found that the current distribution in the hole presents a drum shape, and the current distribution in the hole gradually decreases from the edge of the hole to the center of the hole, which causes a large amount of copper to be deposited on the surface and At the edge of the hole, the standard thickness of the copper layer in the center of the hole that needs copper cannot be guaranteed. Sometimes the copper layer is extremely thin or there is no copper layer. In order to solve the problem of product quality in mass production, current and additives are currently used to solve the problem of deep hole plating. In the high aspect ratio printed circuit board copper electroplating process, most of them are carried out under the condition of relatively low current density with the assistance of high-quality additives, with appropriate air agitation and cathode movement. Enlarge the electrode reaction control area in the hole, and the effect of the electroplating additive can be displayed. In addition, the movement of the cathode is very beneficial to the improvement of the deep plating ability of the plating solution, and the polarization of the plated parts is increased. The formation speed of the crystal nucleus and the growth speed of the crystal grains compensate each other, so as to obtain a high toughness copper layer.
However, when the aspect ratio of the through hole continues to increase or deep blind holes appear, these two process measures appear weak, so horizontal electroplating technology is produced. It is a continuation of the development of vertical electroplating technology, which is a novel electroplating technology developed on the basis of the vertical electroplating process. The key to this technology is to produce a compatible and mutually matched horizontal electroplating system, which can make the plating solution with high dispersion ability, and with the improvement of the power supply mode and other auxiliary devices, shows that it is more excellent than the vertical electroplating method. The functional role.
2. Basic structure of horizontal electroplating system
According to the characteristics of horizontal electroplating, it is an electroplating method in which the printed circuit board is placed from a vertical type to a parallel plating liquid surface. At this time, the printed circuit board is the cathode, and some horizontal electroplating systems use conductive clamps and conductive rollers for current supply. From the convenience of the operating system, it is common to use the roller conductive supply method. The conductive roller in the horizontal electroplating system not only serves as the cathode, but also has the function of conveying the printed circuit board. Each conductive roller is equipped with a spring device, the purpose of which can be adapted to the electroplating needs of printed circuit boards of different thicknesses (0.10-5.0mm). However, during electroplating, all parts in contact with the plating solution may be plated with a copper layer, and the system will not work for a long time. Therefore, most of the currently manufactured horizontal electroplating systems design the cathodes to be switchable to anodes, and then use a set of auxiliary cathodes to electrolytically dissolve the copper on the plated rollers. For the sake of maintenance or replacement, the new electroplating design also considers the parts that are prone to wear and tear to facilitate removal or replacement. The anode is an array of adjustable size insoluble titanium baskets, which are respectively placed on the upper and lower positions of the printed circuit board, and are equipped with a spherical shape of 25mm in diameter and a phosphorus content of 0.004-0.006% soluble copper, cathode and anode. The distance between them is 40mm.
The flow of the plating solution is a system composed of pumps and nozzles, which makes the plating solution flow alternately and rapidly in the closed plating tank back and forth, up and down, and can ensure the uniformity of the plating solution flow. The plating solution is sprayed vertically to the printed circuit board, forming a wall jet vortex on the surface of the printed circuit board. The ultimate goal is to achieve rapid flow of plating solution on both sides of the printed circuit board and through holes to form eddy currents. In addition, a filter system is installed in the tank, and the filter screen used is 1.2 micron to filter out the particulate impurities generated during the electroplating process to ensure that the plating solution is clean and pollution-free.
When manufacturing a horizontal electroplating system, the convenience of operation and the automatic control of process parameters must also be considered. Because in actual electroplating, with the size of the printed circuit board, the size of the through-hole aperture and the required copper thickness, the transmission speed, the distance between the printed circuit boards, the size of the pump horsepower, and the nozzle The setting of the process parameters such as the direction of the current density and the level of the current density requires actual testing, adjustment and control to obtain the copper layer thickness that meets the technical requirements. It must be controlled by a computer. In order to improve the production efficiency and the consistency and reliability of the quality of high-end products, the through-hole processing (including plated holes) of the printed circuit board is formed according to the process procedures to form a complete horizontal electroplating system to meet the development and launch of new products. Needs.
