How is the inner layer of the PCB made?

PCB (Printed Circuit Board, Printed Circuit Board) the production of the inner layer is the entire PCB production process is very important part of its production accuracy and process directly affects the performance and use of PCB. The following will be a detailed introduction to the production process of PCB inner layer:

First, prepare the copper foil and substrate

First of all, you need to prepare for the production of the inner layer of copper foil and substrate. Copper foil is the production of circuit board conductive lines of the main material, usually choose electrolytic copper foil or calendered copper foil. The substrate is used to support the structure of the circuit board, usually composed of glass fibre cloth and epoxy resin and other materials.

Second, the production line design

Next, the line design is required. According to the functional requirements of the circuit board, use circuit design software to draw the circuit board line diagram. The line diagram includes conductive lines, component locations, connection ports, and so on.

Third, the production of dry film

Line design is completed, you need to make dry film. Dry film is a circuit board for the production of the inner layer of the line of film materials, with high precision, high stability, high insulation performance and other advantages. Dry film production process includes coating, pre-baking, exposure, development and other links.

Coating: The dry film is coated on the clean surface of copper foil to form a uniform film.

Pre-baking: The solvents in the dry film are evaporated to improve the adhesion and stability of the dry film.

Exposure: The line design drawings are placed on the dry film, and the photosensitive materials on the dry film are chemically reacted by UV irradiation to form conductive line patterns.

Development: the unexposed part of the dry film stripped, so as to get the desired conductive line graphics.

Fourth, the pressure film and exposure

The production of dry film and copper foil for the press, to further enhance the adhesion of dry film and copper foil. Subsequent exposure, the circuit board graphics transferred to the dry film.

V. Etching

After exposure to the surface of the copper foil covered with a layer of dry film, through the etching process will not be covered by the dry film of copper foil partially etched away, so as to form the required conductive line graphics. The etching process can be carried out in an acid or alkaline solution for a short period of time. In the etching process need to control the etching solution concentration, temperature and flow rate and other parameters to ensure the etching quality and accuracy.

Sixth, peel off the protective film

Finally, peel off the protective film on the surface of the dry film, revealing the conductive line pattern. At this point, the inner layer of production has been completed, you can carry out subsequent processing, such as the outer layer covering, punching, plug-ins and other links.

To sum up, the production of PCB inner layer mainly includes the preparation of materials, production line design, production of dry film, pressure film and exposure, etching and peeling protective film and other steps. Each step requires the control of process parameters and material quality to ensure the production quality and precision of the inner layer. At the same time, continuous exploration of new processes and technologies is also the key to improving PCB performance and reducing costs.