- May 24, 2017 -
The first step is to build up the wiring between the parts. We use the negative transfer (Subtractive transfer) will work in the film on the metal conductor. The technique is to spread a thin sheet of copper foil over the entire surface and remove the excess. Additional transfer Pattern (Additive) is another way of using fewer people, this is only in place where necessary to apply copper wire method, but we do not talk about here.
If it is made of double sided panels, the copper foil on both sides of the PCB substrate will be covered with copper foil. If it is made of multilayer plates, the plates will be glued together in the next steps.
A positive photoresist (positive, photoresist) is made of a photosensitive agent that dissolves under illumination (negative photoresist is broken if it is not illuminated). There are many ways to treat photoresist on copper surface, but the most common way is to heat it up and roll it on the surface containing photoresist (called dry film photoresist). It can also be sprayed in liquid form, but the dry film provides relatively high resolution, and also produces finer wires.
The hood is just a template for making PCB layers. Prior to exposure to UV light, the light shield on the PCB board prevents the photoresist in some areas from being exposed (assuming positive photoresist). These are covered by photoresist and will become cabling.
Other bare copper parts to be etched after photoresist development. The etching process may either dip the board into the etching solvent or spray the solvent onto the board. Commonly used as etching solvent with ferric chloride (Ferric, Chloride), (Alkaline, Ammonia) alkaline ammonia sulfuric acid and hydrogen peroxide (Sulfuric Acid + Hydrogen Peroxide (Cupric Chloride), and copper chloride) by oxidation of the oxide (Cu+2FeCl3=CuCl2+ 2FeCl2). After etching, remove the remaining photoresist. This is called the Stripping program.