Electroplating process management in PCB production
Electroplating process management is an important part of electroplating production, which is determined by electroplating workers after tens of millions of repeated trial and study obtained.
Therefore, the plating process has a strong scientific. The process must be determined not only by the deposition rate of the coating, the current-efficiency of the anode and the cathode, the balance of dissolution and deposition of the metal ions, but also the stability of the pH. Temperature and current density range of broad, and the light rate, leveling performance, bright range and other aspects of the comprehensive formulation.
We must attach great importance to the various technical parameters of the process, the only way to ensure good plating plating. On how to strengthen the management of electroplating process, the author made the following observations.
1, process management
Pre-plating is the basis of plating quality. Pre-plating is not good, the coating is not hair, is the bubble, shelling, or even both caused scrapped. Plating pre-treatment is to remove the plating on the oil, scale, rust and so on. This ensures that the substrate and coating a good combination of force, but also to speed up the deposition rate of the coating, while ensuring plating is not due to plating oil, the introduction of different impurities contaminated.
If there is a galvanized manufacturer, galvanized and found that the coating has a serious blister, burr, so repeatedly adjust the bath, the problem can not be solved. As a result, a master chef found that the workpiece had a layer of glue-like substance stuck to the surface before entering the groove. The original is filled with concentrated sulfuric acid container lined with rubber dissolved in the workpiece surface, can not be cleaned caused. Therefore, the authors suggest that the pre-treatment must be in accordance with the provisions of the process of degreasing, rust, and observe the surface condition of the workpiece.
Pre-plating ultrasonic degreasing, chemical degreasing, anion, anode electrolytic degreasing, pickling descaling and rust and other processes. Need to degrease, rust analysis of the composition of the regular liquid, regular feeding, alkali tank to be regularly filtered, acid tank regularly out of cylinder foot, update and so on. So degreasing, rust liquid in good condition, so as to ensure the quality of the coating.
1.2 bath component detection and management
1.2.1 Laboratory Analysis
To regularly test the content of plating solution, and timely adjustment is a more scientific management approach. The test scale can vary from simple plating manufacturers, simply equipped with some simple laboratory equipment, a small amount of investment, staff can part-time, can be trained to operate.
1.2.2 gravity method
Baume measurement method. This method is only applicable to the relatively simple solution of the bath composition, such as chromic chromic acid-based, only about 1% sulfuric acid can be neglected. This method is also applicable to the pre-treatment of acid (hydrochloric acid or sulfuric acid), and each activated acid, with Baume reference can be.
1.2.3 groping law, gain experience
Adoption of less plus plus, and gradually explore the consumption and loss out of the law to supplement, so that the composition is relatively stable, and accumulated some experience. However, this method is not enough science, mainly based on experience and control.
1.2.4 process management precautions
(1) to manage the process, in addition to carefully control the content of ingredients, but also pay attention to disposable water with the tank, and add chemical raw materials, to prevent mistaken addition and false addition. The authors have encountered the thiourea mistaken for boric acid added to the nickel plating tank, resulting in coating black, then added more hydrogen peroxide and activated carbon, large after normalized gradually. Therefore, the authors suggest that when adding chemical raw materials in the bath, to “look, second test, three add,” to avoid incoherent loss.
Chloride in the bright acid copper liquid can be removed by the silver salt method, the calculated amount of silver nitrate (remove 1 chloride need 5 parts of silver nitrate) dissolved in distilled water, and then dissolved in distilled water, sodium carbonate, sodium carbonate The solution is gradually added to the silver nitrate solution, to make it alkaline to stop, then rinse with distilled water several times, the precipitate is silver carbonate. Add to the copper acid solution under agitation, Ag2CO3 + 2HCl = 2AgCl + H2O + CO2. Can be filtered. The method is good, but expensive, so use less on production. Chlorine can also be used chlorine method, the lower the cost, but must pay attention to the essentials.
First with the analysis of pure zinc powder 1 ~ 3g L water into a paste, gradually stirring, add to the acid copper solution, plus complete set 0.5h (acid copper liquid without warming), add powdered activated carbon 1.5 ~ 2.0g L, stir, stand 0.5 ~ 1.0h, filtered. The author told this method of a mistreatment of hydrochloric acid units, and the other is a town with tap water tank units, the results of the former good effect, the latter due to precipitation overnight, then filtered, the results no effect.
(2) In order to ensure the stability of bath, beware of foreign metal impurities into the bath. The authors suggest that nickel-plated copper products, nickel plating solution must be regularly corrugated iron sheet, 0.05A dm2 current density around the regular electrolysis, or we should add copper agent to ensure that the small current density of light. In addition, the parts fall into the nickel plating bath or acid copper plating bath, should be promptly removed to prevent the accumulation of impurities. For pieces of copper and zinc alloy drop, it is recommended to use window screening slightly wider than the bottom of the flat screen shade, four corners with plastic tube (rod) tie tight, the get off work will be four plastic rods a carry, about to fall copper and Remove the zinc alloy parts, to avoid or reduce the accumulation of copper and zinc impurities in the nickel plating solution, thereby reducing bath failure.
(3) Insulation is not complete or hanging rack bubbling, chrome plating liquid cleaning is not clean, resulting in chrome plating liquid to cyanide copper plating solution or nickel plating solution, polluting the bath, resulting in failure. Therefore, the requirements of the insulation must be good hanging, hanging on the end of an automatic line to hang, take the chromium and then hung on the workpiece, to avoid chromium pollution bath.
1.3 operating conditions
1.3.1 Temperature and current density
In practice, to choose the best temperature, which is the quality and stability of the plating is extremely important. According to a variety of artifacts filtered out the best temperature, and thus strict control, which is an