PCB News - PCB electroplating must see 25 basic knowledge

Today we are going to share with you about PCB board electroplating master some basic knowledge in daily production, qualifications of qualified electroplater, namely, operation mode, process management, process specification requirements, at the same time be able to correctly treat the standardization of the process operation and closely related to the product quality, strictly speaking, not strictly regulate the operation can not be plated to the qualified plating products!

1. Why can the electrolyte conduct electricity?

A: An electrolyte conducts electricity in a different way than a metal conductor. In a metal conductor, current is carried by the movement of free electrons, in an electrolyte by charged ions. In an electrolyte, because the charges of positive and negative ions are equal, there is no electronicity, which is called neutral. When we apply a voltage to the electrolyte, the ions run towards the opposite electrode due to the attraction of a strong electric field. The cation goes to the cathode, the anion goes to the anode. Their motion allows a current to pass through, which is how an electrolyte conducts electricity.

2. In the electroplating process, the hanger is hot and hot, is it caused by the high temperature of the plating solution?

Answer: Although the heating of the hanger is related to the temperature of the solution, the main reason is:

(1) The current through the hanger is too large.

(2) The contact on the hanger is bad, and the resistance increases so that the hanger heats up.

3. What are the main factors controlling the thickness of electrodeposits?

A: Current density, current efficiency and plating time are the main factors controlling electroplating thickness.

4. Are the brass plating and bronze plating the same gold plating?

A: No, brass plating is an alloy plating of copper and zinc, and bronze plating is an alloy plating of copper and tin.

5. What relationship does Faraday's law represent? Describe Faraday's law and the second law?

A: Faraday's law describes the relationship between the amount of charge passing through an electrode and the weight of the reactants in the electrode, also known as the law of electrolysis.

Faraday's law: The weight of a metal during electrolysis is proportional to the current and time passed through the electrolyte.

W=KIt

W -- Weight of precipitated matter (g)

K -- Proportionality constant (electrochemical equivalent)

I -- Currunt strength (ampere)

T -- Power time (hour)

Faraday's second law: when the same amount of current passes through different electrolytes, the weight of the metal precipitated is proportional to the chemical equivalent of each electrolyte.

K=CE

C -- proportionality constant. E -- chemical equivalent

6. Why the plating parts from chemical oil removal to weak acid erosion, the middle of the clean water?

Answer: Because the usual chemical oil removal solution is alkaline, if the oil removal solution directly into the acid corrosion solution, it will play acid, alkali neutralization reaction, reduce the acid concentration and effect. Neutralization reaction products adhere to the workpiece, will affect the quality of the coating. Therefore, after chemical oil removal, the workpiece must be washed with water to enter the acid corrosion solution.

7. Burr and coarse particles of electroplating are usually caused by those reasons. How to solve them?

Answer: the coating appears burr, coarse grain, mainly is the plating solution by suspension impurity pollution caused. Its sources are: dust in the air, anode slime, metal impurities hydrolysate. In addition, there are abnormal bath composition and operating conditions are not required, and so on. The solution is to adjust bath composition and operating conditions. If it is caused by suspended impurities, the plating solution should be filtered.

8. How about the basic procedure of preparing electroplating solution:

Answer: The basic procedure of preparing electroplating solution is as follows:

(1) Put the required electroplating drugs with good juice quantity into the feeding tank (small tank) first, and then add an appropriate amount of water to dissolve, pay attention to not pour the drugs directly into the plating tank.

(2) The impurities contained in the solution can be removed by various chemical methods and treated with activated carbon.

(3) The solution that has been treated and standing is filtered into a clean plating tank and added to a standard amount of water.

(4) Adjust the plating solution process specifications (pH value, temperature, additives, etc.).

(5) Electrolytic deposition with low current density to remove other metal ion impurities until the solution is suitable for operation.

9. Why should laurel be insulated?

Answer: hang provide manufacture to divide hang hook and product contact conductive part commonly outside, the rest all should besmear on insulating material, in order to reduce current loss and metal loss, ensure product effective area electroplating, raise effective current, make hang provide durable.

10. What is the rust removal effect of sulfuric and hydrochloric acid? Can nitric acid remove rust?

A: Product rust removal generally with concentrated hydrochloric acid effect, can achieve high efficiency, even if the time is too long some will not produce corrosion, damage the matrix metal phenomenon. Sulfuric acid is better to remove rust stains on the surface, but the rust removal is very slow, and too long time will produce corrosion phenomenon, damage to the product matrix. Nitric acid can not be used for rust removal, because its oxidation is very strong, in the case of metal oxidation, produce a large number of highly toxic nitrogen oxide gas.

11. What is the effect of pretreatment on the quality of electroplating coating?

Answer: it has been proved from long-term production practice that most of the quality accidents in electroplating production are not caused by the electroplating process itself. Most of them are due to improper pretreatment of metal products. It will not be the level of the coating, adhesion, corrosion resistance and other properties, and the quality of pretreatment is closely related. The surface state and cleanliness of metal products before electroplating are important links to obtain high quality coating. In the rough metal surface, it is difficult to obtain smooth and bright coating, and the coating pores are many, so that the corrosion resistance is reduced. If there is some kind of grease on the metal surface, the normal coating can not be obtained.

12. What is the definition of free cyanide in cyanide bath?

A: In cyanide baths, the excess cyanide that is not bound to the complex salt is called free cyanide.For example, the free cyanide in the cyanide copper plating solution is the excess cyanide that forms [Cu(CN)3]= complex ions.

13. In cyanide copper plating, the anode produces passivation and poor dissolution. Why does the content of free cyanide increase?

Answer: in cyanide copper plating electroplating, the anode dissolves poorly, although a part of cyanide root on the anode oxidation consumption, but on the cathode due to the discharge of copper cyanide complex ion, produced more free cyanide root, and make the plating solution free cyanide content increased.

14. What is the effect of acid bright copper plating anode material on coating quality?

Answer: in the process of acid bright copper plating, if the use of electrolytic copper anode, it is easy to produce copper powder, causing rough coating, and the consumption of brightener is fast, so the use of copper anode containing a small amount of phosphorus (0.1 ~ 0.3%), can significantly reduce the copper powder. However, if the copper anode with too high phosphorus content is used, the dissolution performance of the anode will be worse, resulting in the decrease of copper content in the bath.

15. In nickel plating solution, when the anode area decreases and the anode current density increases, does the pH value of the solution rise or fall?

A: The pH of the solution decreases. This is because the anode decreases, the current density increases, the anode passivates and does not dissolve. After the anode passivates, oxygen is precipitated, and H+ in the solution increases, resulting in an increase in acidity and a decrease in pH.