Must-know! The factors influencing the etching of PCB boards are crucial to the production quality.

Author: Jack Wang

Factors Affecting the Etching of PCB Boards 

The process of transforming a circuit board from a luminous board into one that displays a circuit diagram is rather complex. Currently, the "pattern electroplating method" is typically adopted in circuit board processing. That is, a layer of lead-tin corrosion-resistant coating is pre-applied to the part of the copper foil on the outer layer of the circuit board that needs to be retained (i.e., the circuit pattern part), and then the remaining copper foil is chemically etched. This process is called etching. 

The etching method uses an etching solution to remove the copper foil outside the conductive circuit, while the engraving method uses an engraving machine to remove the copper foil outside the conductive circuit. The former is a common chemical method, and the latter is a physical method. The circuit board etching method is a chemical etching method that uses concentrated sulfuric acid to corrode the unnecessary copper-clad circuit board, and the engraving method uses physical means to engrave the copper-clad board with a special engraving machine and cutting head to form the circuit wiring. 

Factors Affecting the Etching of Circuit Boards 

1. Type of Etching Solution: Different etching solutions have different chemical compositions, resulting in different etching rates and etching coefficients. For example, the etching coefficient of an acidic copper chloride etching solution is generally 3, and that of an alkaline copper chloride etching solution can reach 4. Recent studies have shown that the nitric acid-based etching system can almost achieve no side etching, and the etched lines are almost perpendicular to the sidewalls. 

2. Etching Method: Immersion and bubbling etching will cause significant side corrosion, while splash and spray etching have less side corrosion, and spray etching has the best effect. 

3. Density of the Etching Solution: If the density of the alkaline etching solution is too low, the side corrosion will be aggravated. Selecting an etching solution with a high copper concentration is beneficial for reducing side corrosion. 

4. Etching Rate: If the etching rate is too slow, it will lead to serious lateral corrosion. Improving the etching quality is closely related to accelerating the etching rate. The faster the etching speed, the shorter the residence time of the substrate in the etching solution, the smaller the amount of lateral etching, and the clearer and neater the etched pattern. 

5. pH Value of the Etching Solution: When the pH value of the alkaline etching solution is high, the side corrosion increases. In order to reduce the side corrosion, the pH value should generally be controlled below 8.5. 

6. Thickness of the Copper Foil: It is best to use (ultra-thin) copper foil for etching thin lines, and the lateral corrosion is the smallest. Moreover, the thinner the line width, the thinner the copper foil should be, because the thinner the copper foil, the shorter the time it stays in the etching solution, and the smaller the amount of side etching. 

The etching of circuit boards can identify the positions of wires and component mounting on the circuit board, remove the unnecessary copper sheets, and form the actual circuit. 

Do you want to improve the etching quality of PCB boards? The composition of the solution, the characteristics of the board material, and the operation details should not be underestimated. PCBMASTER is online 24 hours a day to interpret the key factors for you and help with efficient production.

Author: Jack Wang