In the PCB industry, all the uv light sources for parallel exposure machines are chosen because the photoinitiator absorbs the ultraviolet light and releases the active electron. After being obtained by some organic monomers, it can produce polymerization and has a better binding force with the substrate.
In the PCB industry, the wet film or dry film is used for graphic transfer. The characteristic of the film is that it will polymerize after ultraviolet irradiation, while it is left on the PCB. This allows the circuitry on the plate to be transferred to the circuit board.
And the parallel exposure lamp is the light that comes from the lamp is reflected and parallel, so that you can do more fine lines.
Other exposure machines use ultraviolet light, but with less precision.
The so-called graphics transfer is to copy the design drawing from your computer to your product (the same as developing the picture from the negative of the previous picture). However, it is necessary to consider the feasibility of production and mass production. Currently, there are some industrial photoinitiators that release active electrons after absorbing energy (ultraviolet light), and these electrons can be obtained by some organic monomers to produce polymerization. The monomers without polymerization can be easily removed in the weak alkali environment, and the materials after polymerization have better binding force with the host, and are also very resistant to acid and base. So you can reference it to mass production.
That is to say, the advantages of the above process determine that the PCB production will choose this process, and because this process is chosen, the light initiator inside needs to be stimulated by ultraviolet (energy), so uv is also selected. This light primer cannot be excited by visible or infrared light. So uv is a necessary condition in this process.
In addition, even if there are visible or infrared light initiators, there will be many other problems when applied to production. Visible light is everywhere. How to prevent the external light from interfering with production? Infrared ray is to have heating effect, how does product assure to work under thermal radiation, assure quality?