Abstract In the PCB production process, it is necessary to use dry film, solder resist ink and Other photosensitive materials. In order to ensure that the production process does not produce undesired exposure, in the dry film. Photoresistance soldering process often uses a yellow light tube that does not contain ultraviolet components.
Although the yellow light has no UV component and avoids the influence on the product, the dim light has a negative effect on the production efficiency of the employee. The article tests the influence of the LED lamp on the PCB photosensitive material, and analyzes the LED lamp used in the PCB production process. The feasibility of this provides a new attempt to improve production efficiency and reduce costs.
1 Background
In the PCB production process, the formation of each layer and the final solder mask are inseparable from the photosensitive material. These photosensitive materials include dry film, solder resist ink, etc. The process of pattern formation is divided into three steps, and the whole board is covered with photosensitive material. Exposure. Development. The exposure is carried out by ultraviolet light. In order to ensure that the PCB production board coated with photosensitive material before exposure does not produce undesired exposure, in the production process, a yellow light tube containing no ultraviolet component is often used. While ensuring product quality, it also brings some negative effects. Employees work under yellow light conditions for a long time, which is prone to fatigue and lead to low plate bias and low production efficiency. The yellow light tube is shown in Figure 1.
In order to improve the quality of the products and the production efficiency of the employees, test the influence of LED tubes on the photosensitive materials of PCBs, try to replace the yellow light tubes without ultraviolet rays with LED tubes.
2 Light and LED tube related theoretical knowledge
2.1 visible wavelength
The wavelength range of visible light is between (770 and 350) nm.
Electromagnetic waves with different wavelengths cause different color perceptions of the human eye.
(770~622) nm, feeling red; (622~597) nm, orange; (597~577) nm, yellow; (577~492) nm, green; (492~455) nm, blue ochre; ~350) nm, purple. Figure 2 shows the position of the visible spectrum in the electromagnetic spectrum.
Among them, ultraviolet light is a general term for radiation from 10 nm to 400 nm in the electromagnetic spectrum, which can not cause people's vision. Ultraviolet light can make photographic film containing silver bromide sensitive. Ultraviolet light can also polymerize photosensitive material to make PCB. Graphics.
2.2 Yellow light tube and LED tube
2.2.1 Yellow light tube
At present, the lamp used in the production environment of PCB photosensitive materials is a yellow light tube. This type of lamp does not contain ultraviolet light, so it does not cause exposure of the photosensitive material. The spectrum of the yellow light tube and the ordinary white light tube is shown in Fig. 3.
2.2.2 LED tube
LED tube is also commonly known as light tube. Fluorescent tube, its light source uses LED as the illuminant. Its characteristics are that the light does not contain ultraviolet and infrared rays, does not produce radiation (the light of ordinary lamps contains ultraviolet and infrared rays), the wavelength is stable. For example, the nm LED tube has a wavelength range of (445~447.5) nm, while the ordinary fluorescent tube is (380~780) nm. The main wavelength of the 440 nm LED tube is concentrated at (440~455) nm. The content can be ignored.
The spectrum is shown in Figure 4.
3 photosensitive material sensitization principle
3.1 photosensitive material sensitization principle
Generally, the photochemical reaction refers to the polymerization of a photosensitive polymer produced by absorbing a certain wavelength energy (generally 300 nm to 400 nm). The photosensitive material is shown before and after ultraviolet light irradiation.
3.2 Photosensitive wavelengths of commonly used dry film and solder resist inks
The photosensitive wavelengths of commonly used dry film and solder resist inks are shown in Table 1.
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