Process flow and solution of pcb manufacturing

The process flow and chart of pcb manufacturing are as follows:

For designers, we mainly consider the minimum line width, spacing control and wiring uniformity. Because the distance is too small, the film will be caught, and the film will not fade, resulting in short circuit. The line width is too small, and the film adhesion is insufficient, which leads to open circuit. Therefore, the safe spacing in circuit design (including wire to wire, wire to pad, pad to pad, wire to copper surface, etc.). ) must be considered in production.

1, pretreatment: plate grinding. The main function of the grinding disc: the basic pretreatment is mainly to solve the problems of surface cleanliness and surface roughness. Remove oxidation, increase the roughness of copper surface, and promote the adhesion of thin film to copper surface.

2. Sticking film: Sticking dry film or wet film on the treated substrate by hot pressing or coating, which is convenient for subsequent exposure production.

3. Exposure: align the negative with the substrate with the dry film pressed, and transfer the negative pattern to the photosensitive dry film by ultraviolet irradiation on the exposure machine.

4. Development: The unexposed dry film/wet film is dissolved and washed away by the weak alkalinity (sodium carbonate) of the developer, leaving the exposed part.

5. Etching: After the unexposed dry film/wet film is removed by the developer, the copper surface will be exposed, and the exposed copper surface will be dissolved and corroded by acidic copper chloride to obtain the required circuit.

6. Stripping: Stripping the exposed dry film protecting the width and parallel surface of the copper limb with sodium hydroxide solution to expose the circuit pattern.

7. Browning: The purpose is to form microscopic roughness and organic metal layer on the inner surface of copper, and enhance the adhesion between layers.

8. Lamination: Lamination is a process of bonding all layers of circuits into a whole by using the viscosity of pp sheets. This adhesion is achieved by mutual diffusion and infiltration of macromolecules at the interface, and then interweaving, so that discrete multilayer boards and pp sheets are pressed together to form multilayer boards with the required number of layers and thickness. In practice, copper foil, adhesive sheet (prepreg), inner plate, stainless steel, isolation plate, kraft paper, outer steel plate and other materials are laminated according to the process requirements.

9. Drilling: through holes are generated between layers of the circuit board to achieve the purpose of connecting layers.

12, outer layer pattern electroplating, SES: electroplate the copper layer of holes and wires to a certain thickness (20-25um) to meet the requirements of the copper layer thickness of the final PCB. The useless copper on the surface of the circuit board is etched away, revealing useful circuit patterns.

13, solder resist: solder resist, also known as solder resist and green oil, is one of the most critical processes in PCB production, mainly by screen printing or coating solder resist ink, coating a solder resist layer on the board surface, exposing the wafers and holes to be soldered through exposure and development, and covering other places with solder resist to prevent short circuit during welding.

14. Screen printing of characters: the required characters, trademarks or part symbols are printed on the wooden board by screen printing, and then exposed by ultraviolet radiation on the wooden board.

15. surface treatment: bare copper itself has good solderability, but it is easy to be oxidized by moisture when exposed to air for a long time, and tends to exist in the form of oxide, which is unlikely to remain as original copper for a long time, so it is necessary to surface treat the copper surface. The most basic purpose of surface treatment is to ensure good solderability or electrical performance.

16. molding: cut the PCB into the required size by CNC molding machine.

17. electrical measurement: simulate the state of the board, and conduct electrical performance inspection when energized to see if there is an open circuit or a short circuit.

18. Final inspection, sampling and packaging: check the appearance, size, aperture, thickness and marking of the plate to meet customer requirements. Qualified products are packed in bundles, which is convenient for storage and transportation.