With the rapid development of the electronics industry, PCB wiring is becoming more and more sophisticated. Most PCB manufacturers use the PCB dry film process to complete graphics transfer, and the use of PCB dry film is becoming more and more popular. The following is an introduction from the Shenzhen EMS manufacturer’s factory-Kingford on the problems of the PCB dry film process: the dry film mask is damaged and leaks during dry film electroplating.
table of Contents
1. What is PCB dry film
2. The dry film mask is damaged
3. Seepage in dry film electroplating
1.What is PCB dry film?
1.1. Definition
PCB dry film is a kind of polymer compound; it can produce a kind of polymerization reaction (the reaction process of synthesizing polymer from monomer) after being irradiated by ultraviolet rays to form a stable substance attached to the board surface so as to block electroplating The function of etching.
1.2. Main features of PCB dry film
Under certain temperature and pressure, it will stick firmly to the board surface;
Under certain light energy irradiation, energy will be absorbed, and cross-linking reaction will occur;
The Part that is not irradiated by light has no cross-linking reaction and can be dissolved by weak lye.
1.3. The layering of PCB dry film
Generally divided into three layers, one layer is a PE protective film, the middle is a dry film layer, and the other is a PET protective layer. Both the PE layer and the PET layer are only protective and must be removed before lamination and development. What really works is the middle layer of dry film, which has a certain viscosity and good photosensitivity.
1.4 Classification of PCB dry film
The dry film can be divided into four categories according to thickness: (0.8mil, 1.2mil, 1.5mil, 2.0mil)
0.8mil thick dry film is mainly used for FPC fine circuit production.
1.2mil dry film is mainly used for inner layer board operations.
1.5mil, the dry film is mainly used for outer layer operation. Of course, it can also be used for inner operation. However, because it is thicker, it is prone to undercut during the etching process, and the cost is relatively high, so it is generally not used as an inner layer.
2.0mil dry film is mainly used for boards with special requirements; for example, when the larger secondary hole 1.5mil dry film cannot meet the requirements, it is used.
2. There are holes in the dry film mask
Many customers believe that after a problem with PCB, the dry film process such as a hole phenomenon, the temperature, and pressure of the film should be increased to enhance its binding force. In fact, this view is incorrect because the temperature and pressure are too high. Excessive volatilization of the solvent of the layer makes the PCB dry film brittle and thinner, and it is easy to break through the holes during development. We must always maintain the toughness of the dry film. Therefore, after the holes appear, we can improve from the following points:
1. Reduce the temperature and pressure of the film
2. Improve drilling and piercing
3. Increase exposure energy
4. Reduce shadow pressure
5. The parking time after pasting should not be too long so as not to cause the semi-fluid medicinal film in the corner to spread and thin under the action of pressure.
6. Do not stretch the dry film too tightly during the pasting process
With the rapid development of the electronics industry, PCB wiring is becoming more and more sophisticated. Most PCB manufacturers use the PCB dry film process to complete graphics transfer, and the use of PCB dry film is becoming more and more popular. The following is an introduction from the Shenzhen EMS manufacturer’s factory-Kingford on the problems of the PCB dry film process: the dry film mask is damaged and leaks during dry film electroplating.
table of Contents
1. What is PCB dry film
2. The dry film mask is damaged
3. Seepage in dry film electroplating
1.What is PCB dry film?
1.1. Definition
PCB dry film is a kind of polymer compound; it can produce a kind of polymerization reaction (the reaction process of synthesizing polymer from monomer) after being irradiated by ultraviolet rays to form a stable substance attached to the board surface so as to block electroplating The function of etching.
1.2. Main features of PCB dry film
Under certain temperature and pressure, it will stick firmly to the board surface;
Under certain light energy irradiation, energy will be absorbed, and cross-linking reaction will occur;
The Part that is not irradiated by light has no cross-linking reaction and can be dissolved by weak lye.
1.3. The layering of PCB dry film
Generally divided into three layers, one layer is a PE protective film, the middle is a dry film layer, and the other is a PET protective layer. Both the PE layer and the PET layer are only protective and must be removed before lamination and development. What really works is the middle layer of dry film, which has a certain viscosity and good photosensitivity.
1.4 Classification of PCB dry film
The dry film can be divided into four categories according to thickness: (0.8mil, 1.2mil, 1.5mil, 2.0mil)
0.8mil thick dry film is mainly used for FPC fine circuit production.
1.2mil dry film is mainly used for inner layer board operations.
1.5mil, the dry film is mainly used for outer layer operation. Of course, it can also be used for inner operation. However, because it is thicker, it is prone to undercut during the etching process, and the cost is relatively high, so it is generally not used as an inner layer.
2.0mil dry film is mainly used for boards with special requirements; for example, when the larger secondary hole 1.5mil dry film cannot meet the requirements, it is used.
2. There are holes in the dry film mask
Many customers believe that after a problem with PCB, the dry film process such as a hole phenomenon, the temperature, and pressure of the film should be increased to enhance its binding force. In fact, this view is incorrect because the temperature and pressure are too high. Excessive volatilization of the solvent of the layer makes the PCB dry film brittle and thinner, and it is easy to break through the holes during development. We must always maintain the toughness of the dry film. Therefore, after the holes appear, we can improve from the following points:
1. Reduce the temperature and pressure of the film
2. Improve drilling and piercing
3. Increase exposure energy
4. Reduce shadow pressure
5. The parking time after pasting should not be too long so as not to cause the semi-fluid medicinal film in the corner to spread and thin under the action of pressure.
6. Do not stretch the dry film too tightly during the pasting process
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