PCB etching process is an essential part of the production of PCB, it is through a chemical reaction that will not cover the copper layer corrosion, thus forming the circuit board on the line required.
PCB printed circuit factors affect the characteristics of the etching solution, a choice of etching solution etching solution selection is very important, it is so important because it is in the printed circuit board manufacturing process directly affects the precision and quality of high-density fine wire image.
1) the concentration of the etching solution: should be based on the principle of metal corrosion and the type of structure of the copper foil, through the test method to determine the concentration of the etching solution, it should have a greater margin of choice, that is, refers to a wider range of processes.
2)The composition of chemical composition of the etching solution: The chemical composition of the etching solution is different, its etching rate is not the same, and the etching coefficient is also different.
3) temperature: The temperature on the etching solution characteristics of the impact is relatively large, usually in the chemical reaction process, the temperature accelerates the fluidity of the solution and reduces the viscosity of the etching solution to improve the etching rate plays a very important role. The temperature is too high, but also easily causes some of the chemical components in the etching solution to volatilization, resulting in the chemical composition of the etching solution in the proportion of imbalance, and at the same time, the temperature is too high, may cause the polymer antioxidant layer is destroyed and affect the etching rate. The etching layer is destroyed and affects the service life of the etching equipment. Therefore, the etching solution temperature is generally controlled within a certain process range.
4) The thickness of the copper foil used: the thickness of the copper foil has an important impact on the circuit pattern of the wire density. In thin copper foil, the etching time is short, and side corrosion is very small; conversely, side corrosion is very large. Therefore, according to the technical requirements of the design the circuit pattern of the wire density, and wire precision requirements, the thickness of copper foil. At the same time, the copper elongation, surface junction product structure, etc., will have a direct impact on the characteristics of the etching solution.
5) The geometry of the circuit: circuit graphics wire in the X direction and the distribution of the position of the direction of the Ya, if not balanced, will have a direct impact on the flow rate of the etching solution on the board. Similarly, if the same plate on the narrowly spaced wire parts and widely spaced wire parts state, widely spaced wire distribution parts, etching will be excessive. Therefore, this requires the designer in the circuit design, should be the first to understand the feasibility of the process, as far as possible to achieve a uniform distribution of circuit graphics across the board, the thickness of the wire should be as consistent as possible. Especially in the production of multi-layer printed circuit boards, with a large area of copper foil as a grounding layer, the quality of etching has a great impact on the proposed design into a mesh pattern is appropriate.
Process Flow
1. Production of printed photoresist film
a. Printing photoresist film is one of the most important steps in the PCB etching process. First of all, we need to prepare the printing photoresist liquid and printing machine.
b.Coat the printed photoresist uniformly on the copper layer, and dry and expose it through the printing machine.
c. After exposure, the unexposed part will be cleaned with a developing solution, so that the desired pattern can be obtained.
2. Etching treatment pcb corrosion
a. After the completion of the pattern production, needs to be etched. First, need to prepare the etching solution and stirrer.
b. Put the copper plate into the etching tank and add enough etching solution. Start the stirrer to make it mix evenly.
c. In a certain period, the etching solution will corrode off the copper layer that is not covered with printed photoresist, thus forming the desired line.
3. Cleaning treatment
a. After the completion of etching, need to carry out the cleaning process. First need to prepare the cleaning fluid and cleaning tank
b. PCB into the cleaning tank, and add a sufficient amount of cleaning fluid. Start the stirrer to make it evenly mixed.
c. In a certain period, the cleaning solution will be printed photoresist and other impurities cleaned.
4. Drilling Process
a. Drilling is another important step in PCB production. First of all, you need to prepare the drill bit and drilling machine.
b. Place the PCB on the drill press and use the appropriate size drill bit to drill the holes.
c. After drilling, use a vacuum cleaner to remove the metal chips.
5. Soldering
a. Soldering is the last step in PCB fabrication. First of all, you need to prepare the soldering wire and soldering station.
b. Heat the solder wire to a molten state and apply it to the components to be soldered.
c. Place the component on the PCB and use the soldering station to perform the soldering process.
Precautions
1. When making printed photoresist film, it is necessary to pay attention to the uniformity of photoresist and exposure time.
2. In the etching process, you need to control the concentration and temperature of the etching solution. pcb corrosion