In the production of electronic products, there will be a production process of printed circuit board. Printed circuit boards are used in electronic products in all industries. It is the carrier of electronic schematic diagram that can realize the design function and turn the design into physical products.
The process of PCB production is as follows:
Cutting - > sticking dry film and film - > exposure - > development - > etching - > film stripping - > drilling - > copper plating - > resistance welding - > silk screen printing - > surface treatment - > forming - > electrical measurement
You may not know these terms yet. Let's describe the production process of double-sided board.
1、 Cutting
Cutting is to cut the copper clad laminate into boards that can be produced on the production line. Here, it will not be cut into small pieces according to the PCB diagram you designed. First, assemble many pieces according to the PCB diagram, and then cut them into small pieces after the PCB is finished.
Apply dry film and film
This is to stick a layer of dry film on the copper clad laminate. This film will solidify on the board through ultraviolet irradiation to form a protective film. This facilitates subsequent exposure and etching away unwanted copper.
Then paste the film of our PCB. The film is like a black-and-white negative of a photo, which is the same as the circuit diagram drawn on the PCB.
The function of film negative is to prevent ultraviolet light from passing through the place where copper needs to be left. As shown in the above figure, the white one will not transmit light, while the black one is transparent and can transmit light.
exposure
Exposure: this exposure is to irradiate ultraviolet light on the copper clad laminate attached to the film and dry film. The light shines on the dry film through the black and transparent place of the film. The place where the dry film is illuminated by the light is solidified, and the place where the light is not illuminated is the same as before.
Development is to dissolve and wash the unexposed dry film with sodium carbonate (called developer, which is weakly alkaline). The exposed dry film will not be dissolved because it is solidified, but will still be retained.
etching
In this step, the unnecessary copper is etched. The developed board is etched with acidic copper chloride. The copper covered by the cured dry film will not be etched, and the uncovered copper will be etched. Left the required lines.
Film removal
The step of film removal is to wash the solidified dry film with sodium hydroxide solution. During development, the uncured dry film is washed off, and the film stripping is to wash off the cured dry film. Different solutions must be used to wash the two forms of dry film. Up to now, all the circuits that reflect the electrical performance of the circuit board have been completed.
drill hole
In this step, if the hole is punched, the hole includes the hole of the pad and the hole through the hole.
Copper plating
This step is to coat a layer of copper on the hole wall of pad hole and through hole, and the upper and lower layers can be connected through through through hole.
Resistance welding
Resistance welding is to apply a layer of green oil on the place that is not welded, which is non-conductive to the outside world. This is through the screen printing process, apply green oil, and then similar to the previous process, expose and develop the welding pad to be welded.
Silk screen printing
Silk screen printing character is to print the component label, logo and some description words through screen printing.
surface treatment
This step is to do some treatment on the pad to prevent copper oxidation in the air, mainly including hot air leveling (i.e. tin spraying), OSP, gold deposition, gold melting, gold finger and so on.
Electrical measurement, sampling inspection and packaging
After the above production, a PCB board is ready, but the board needs to be tested. If there is open or short circuit, it will be tested in an electric testing machine. After this series of processes, the PCB board is officially ready for packaging and delivery.
The above is the production process of PCB. Do you understand it. Multilayer boards also need a lamination process. I won't introduce it here. Basically, I know the above processes, which should have some impact on the production process of the factory.
