PCB Tech - How to strengthen PCB electroplating process management?

PCB electroplating process management is an important link in electroplating production. It is determined by electroplating workers after tens of millions of trial and error researches. Therefore, the electroplating process is highly scientific. The determination of the process must not only consider the deposition rate of the coating, the current efficiency of the cathode and anode, the balance of metal ion dissolution and deposition, but also the stability of the pH value, the wide range of temperature and current density, as well as the light extraction rate and leveling. The performance, brightness range and other aspects are comprehensively formulated. Therefore, we must pay great attention to the various technical parameters stipulated in the process, and only in this way can we guarantee a good coating. On how to strengthen the management of PCB electroplating process, the author puts forward the following points.

1. Process management

1.1 Pre-processing

The pretreatment of PCB electroplating is the basis of electroplating quality. If the pre-electroplating process is not good, the plating layer is either blooming, bubbles, shelling, or even both, resulting in defective products being scrapped. The pre-treatment of electroplating is mainly to remove oil stains, oxide scale, rust, etc. on the plated parts. This not only guarantees the good bonding force between the substrate and the plating layer, but also accelerates the deposition rate of the plating layer, and at the same time ensures that the plating solution is not contaminated by the oil stains of the plating parts and the introduction of foreign metal impurities.

1.2 Detection and management of bath composition

1.2.1 Laboratory analysis

It is a more scientific management method to take regular testing of the content of the plating solution and adjust it in time. The scale of the test can be large or small. For a pure plating manufacturer, it only needs to be equipped with some simple test equipment and a small amount of investment. The personnel can be part-time and can be operated after training.

1.2.2 Proportion method

Measured with Baume specific gravity method. This method is only suitable for solutions with relatively simple bath composition. For example, chromium plating is dominated by chromic acid, and sulfuric acid accounts for only about 1%, which can be ignored. This method is also suitable for pre-treatment acid (hydrochloric acid or sulfuric acid), as well as the activated acid of each channel, and the Baumé degree can also be used as a reference.

1.2.3 Explore the rules and accumulate experience

Take less and more frequent, gradually explore the law of consumption and bring out the loss to supplement, make the composition relatively stable, and accumulate certain experience. But this method is certainly not scientific enough, it is mainly controlled by experience.

1.2.4 Matters needing attention in PCB electroplating process management

(1) To manage the process well, in addition to carefully controlling the content of ingredients, it is also necessary to pay attention to the water quality of the disposable tank, and to prevent mistaken addition and incorrect addition when adding chemical raw materials. The author once encountered the mistakenly adding thiourea to the nickel plating tank as boric acid, which caused the coating to turn black. Later, more hydrogen peroxide and activated carbon were added, and it gradually became normal after major treatment. Therefore, the author suggests that when adding chemical raw materials to the plating solution, "one look, two inspections, three additions" should be adopted to avoid involuntary losses.

(2) In order to ensure the stability of the plating solution, beware of foreign metal impurities being brought into the plating solution. The author recommends that the nickel-plated products on copper, the nickel plating solution must be regularly electrolyzed with corrugated iron plates with a current density of about 0.05 Am2, otherwise a copper removal agent must be added to ensure the brightness of the small current density area. In addition, if the parts fall into the nickel plating tank or the acid copper plating tank, they must be taken out in time to prevent the accumulation of impurities. For copper parts and zinc alloy workpieces falling, it is recommended to use window screens to make flat screens slightly wider than the bottom of the groove, and to tighten the four corners with plastic tubes (rods). The zinc alloy parts are taken out to avoid or reduce the accumulation of copper and zinc impurities in the nickel plating solution, thereby reducing the failure of the plating solution. (3) Incomplete insulation or bubbling of the hanger makes the chromium plating solution not clean, causing the chromium plating solution to be brought into the cyanide copper plating solution or nickel plating solution, which contaminates the plating solution and causes malfunctions. Therefore, it is required that the insulation of the hanger must be intact. For the hanger that hangs to the end on the automatic line, take the chromium back and then hang the workpiece to avoid chromium contamination of the plating solution.

1.3 Operating conditions

1.3.1 Temperature and current density

In actual operation, it is necessary to choose the best temperature, which is extremely important to the quality and stability of electroplating. It is necessary to screen out the best temperature according to various workpieces and strictly control it. This is an important measure to ensure quality. Temperature and cathode current density are generally proportional. The temperature is high (within the process range), the cathode current density can be opened up, the coating is fine, and the deposition rate is fast.

1.3.2 Conductive contact

Conductive contact generally refers to the contact between the hanger and the pole, the contact between the anode hook and the pole, the contact between the pole and the copper ingot, the contact between the copper bar and the copper ingot, etc., each conductive contact point must maintain the color of copper, so It reduces the resistance or reduces the non-conductivity due to poor local contact, which affects the quality of the plated parts. The author recommends that the conductive contact parts should be brushed frequently and kept clean.

1.3.3 Cathode movement and stirring

The purpose of cathode movement and stirring is to accelerate the convection and diffusion of ions, increase the current density of the cathode, and at the same time improve the uniformity of the coating, and the hydrogen is easy to precipitate. If the cathode movement stroke or frequency does not meet the requirements, it is easy to produce air tumors or streaks when plating large flat workpieces. The stroke of the cathode movement must be controlled at about 10 cm, and the frequency must be 15 min. In addition to the above-mentioned effects, air agitation can also reduce the production of monovalent copper for bright acid copper liquid, but air agitation must be matched with continuous filtration. Its continuous filtration is not less than 5-10 cycles per hour, otherwise it is easy to produce burrs.

2. Quality management

Electroplating enterprises must implement modern quality management. To do a good job in quality management, first of all, we must establish a quality management system in accordance with the GB T19000-ISO9000 quality management standard. To this end, it is necessary to establish electroplating quality standards, including the establishment of quality requirements between various processes, such as sanding, degreasing, and acid etching. At the same time, it is necessary to establish corresponding inspection systems, such as finished product inspection methods, which are inspections one by one. Or sampling inspection and so on. Formulate standards and strengthen inspections to prevent unqualified plating parts from leaving the factory, so that unqualified plating parts between processes do not flow into the next process, blocking the occurrence of batch defective products, and eliminating defective products in the production process, so as to ensure Quality, improve the rate of genuine products. Therefore, the author suggests to strengthen the basic work of modern quality management.

3. Control the quality of raw materials

WhenPCB companies purchase metals and chemical raw materials, they pay more attention to their quality while paying attention to prices. The author believes that price and quality must be considered. If only the price is considered, it will cause unstable plating solution, many failures, and finally the plating company will suffer. When purchasing raw materials, both the price factor and the importance of the quality of the raw materials must be taken into consideration. Price and quality should not be neglected. Only by grasping the quality of raw materials and equipped with a set of modern quality management system can enterprises have good economic benefits.