Wet Process and PCB Surface Treatment (2)

14. Etching Resist

Refers to the part of the copper conductor that is to be protected from corrosion, and the anti-corrosion film layer made on the copper surface, such as image transfer photoresist, dry film, ink pattern, or tin-lead coating, etc. are all anti-corrosion resists agent.

15. Hard Anodizing

Also known as “hard anodic treatment”, it refers to placing pure aluminum or some aluminum alloys in a low-temperature anodic treatment solution (sulfuric acid 15%, oxalic acid 5%, temperature below 10 ℃, lead plate for cold electrode, anodic current Density is 15ASF), after long-term electrolysis treatment for more than 1 hour, an anodized film with a thickness of 1-2 mil can be obtained, which has high hardness (ie crystalline A12O3), and can be dyed and sealed again. It is an aluminum material A good anti-corrosion and decorative treatment method.

16. Hard Chrome Plating

Refers to the thick chromium layer plated for wear-resistant and lubricating industrial purposes. Ordinary decorative chrome plating can only be applied to a glossy nickel surface for about 5 minutes, otherwise too long will cause cracks. Hard chrome can be operated for several hours. The traditional bath composition is CrO3250 g/1+H2SO410%, but it needs to be heated to 60℃, and the cathode efficiency is only 10%. Therefore, other electricity will generate a large amount of hydrogen and bring out a large amount of harmful dense fog composed of chromic acid and sulfuric acid, and also cause a large amount of yellow-brown wastewater pollution in water washing. Although the wastewater needs to be strictly treated and the cost will rise, hard chrome plating is a wear-resistant coating on many shafts or drums, so it cannot be completely abolished.

17. Mass Finishing

For many small metal products, it is necessary to carefully remove the edges and corners, eliminate scratches and polish the surface before electroplating, so as to achieve the most perfect base. Usually, the polishing of the base before plating, large objects can be done manually and mechanically with cloth wheels. However, those with a large number of small pieces must rely on the processing of automatic equipment. Generally, the small pieces are mixed with “Abrasive Media” specially made of ceramics of various shapes, and various anti-corrosion solutions are injected to rotate slowly at an oblique position. By rubbing each other, the polishing and finishing of all parts of the surface can be completed within tens of minutes. After being poured out and separated, it can be loaded into the barrel plating tank (Barrel) for rolling plating.

18. Microetching

It is a station in the wet process of the circuit board. The purpose is to remove foreign contaminants on the copper surface. Usually, the copper layer below 100μ-in should be removed by etching, which is called “micro-etching”. Commonly used microetching agents are “sodium persulfate” (SPS) or dilute sulfuric acid plus hydrogen peroxide. In addition, when performing “microsection” microscopic observation, in order to clearly see the structure of each metal layer under high magnification, it is also necessary to microetch the polished metal section. This term is also sometimes referred to as Softetching or Microstripping.

19. Mouse Bite

It refers to the irregular gap on the edge of the line after etching, which is like a bite mark after being bitten by a mouse.

20. Overflow

The liquid level of the liquid in the tank rises over the upper edge of the tank wall and flows out, which is called “overflow”. In each water washing station of the circuit board wet process, a tank is often divided into several parts, which are washed from the dirtiest water in an overflow way, and can be dipped many times to save water.

21. Panel Process Full Plate Electroplating Method

In the orthodox Substractive Process of the printed circuit board, this is the practice of obtaining the outer layer circuit by direct etching. The process is as follows: PTH-full-board thick copper plating to 1 mil on the hole wall-positive film dry film to cover the hole-etching -Remove the film to get the outer layer board of the bare copper circuit. The process of this positive film method is very short, and there is no need for secondary copper, no lead-tin plating and tin-lead stripping, which is indeed a lot easier. However, thin lines are not easy to do well, and the etching process is also difficult to control.

22. Passivation Treatment

It is a term for metal surface treatment, which often refers to the immersion of stainless steel objects in a mixture of nitric acid and chromic acid to force the formation of a thin oxide film to further protect the substrate. In addition, an insulating layer can also be formed on the surface of the semiconductor, so that the surface of the transistor can be electrically and chemically insulated to improve its performance. The formation of such a surface film is also called passivation treatment.

23. Pattern Process Circuit Electroplating Method

It is another way to manufacture circuit boards by the reduction method. The process is as follows: PTH——> once copper plating——> negative film image transfer——> secondary copper plating——> tin lead plating——> etching——> tin stripping Lead -> get the outer layer of bare copper plate. This pattern process of secondary copper and tin-lead plating by negative film method is still the mainstream in various circuit board manufacturing processes. Just because it is a safer practice and less prone to problems. As for the long process, the additional troubles such as tin-lead plating and tin stripping are already secondary considerations.

24. Puddle Effect

It means that when the board is in the horizontal transportation, when the plate is sprayed and etched up and down, the upward surface of the board will accumulate etching solution to form a layer of water film, which hinders the effect of the fresh etching solution sprayed later, and blocks the oxygen in the air. Power boost, resulting in insufficient etching effect, and its corrosion rate is slower than that of spraying on the lower surface. The negative effect of this water film is called Puddle Effect.

25. Reverse Current Cleaning

It is an anode in which the metal work is hung in the cleaning solution, and the stainless steel plate is used as the cathode. The oxygen generated in the electrolysis is used to cooperate with the dissolution (oxidation reaction) of the metal work in the tank liquid, and the surface of the work is removed. This process can also be called “Anodic Cleaning” anodic electrolytic cleaning. It is a commonly used technology for metal surface treatment.

26. Rinsing

In the wet process, in order to reduce the mutual interference of chemicals in each tank, various intermediate transition sections need to be thoroughly cleaned to ensure the quality of various treatments. The water washing method is called Rinsing.