Printed Circuit Board)
The Chinese name is printed circuit board, also known as printed circuit board. It is an important electronic component and a support for electronic components.
Because it is made by electronic printing, it is called a 'printed' circuit board. ?
In the production process of electronic products, there will definitely be a production process of printed circuit boards.
Printed circuit boards are used in electronic products in all industries.
It is the carrier of the electronic schematic diagram that can realize the design function and turn the design into a physical product.
The appearance of the circuit board is shown in the following figure. The following figure shows the finished circuit board after welding components. Before the PCB appears, the circuit is composed of point-to-point wiring.
The reliability of this method is very low, because as the circuit ages, the rupture of the line will lead to open circuit or short circuit of the line node.
Winding technology is a major advance in circuit technology. This method improves the durability and replaceability of the circuit by winding small diameter wires around the pillars at the connection points.
When the electronics industry developed from vacuum tubes and relays to silicon semiconductors and integrated circuits, the size and price of electronic components were also declining.
Electronic products appear more and more frequently in the consumer field, prompting manufacturers to find smaller and more cost-effective solutions. As a result, PCB was born.
Briefly describe the process of PCB production: material cutting-> Dry film and film-> Exposure-> Development-> Etching-> Film removal-> Drilling-> Copper plating-> Solder resist-> Silk screen-> Surface treatment-> Forming-> Electrical measurement and other steps, take the production process of double-sided plates as an example: first, cutting materials, cutting materials is to cut copper clad laminate into plates that can be produced on the production line, it will definitely not be cut into small pieces.
It is to make a lot of pieces according to the PCB diagram, then open the material, after the PCB is done, then cut into small pieces.
Second, stick a dry film and a film on the copper clad laminate. This film is irradiated by ultraviolet rays and will solidify on the board to form a protective film.
This facilitates subsequent exposure and etching unnecessary copper. Posted dry film before and after as shown in.
Blue is the film, yellow is copper, and Green is the FR4 substrate.
Before pasting: After pasting: then paste the film diagram of PCB diagram. The film diagram is like a black and white negative of a photo, which is the same as the circuit diagram drawn on PCB. As shown in.
The role of the film film is to prevent the ultraviolet light from passing through the place where copper needs to be left.
As shown in the above figure, the white one is not transparent, and the black one is transparent and transparent.
Third, exposure, exposure, exposure is to illuminate the ultraviolet rays to the copper clad plate attached to the film and the dry film. The light shines on the dry film through the black and transparent place of the film, and the dry film is solidified where the light shines, the place where the light is not illuminated is still the same as before.
As shown in the following figure, after the blue dry film is irradiated by ultraviolet rays, the front and back sides are cured, such as the purple part is cured.
The following figure shows the blasting machine. Fourth, development, development is to use sodium carbonate (Called developer, weakly alkaline)
The unexposed dry film is dissolved and washed off, and the exposed dry film will not be dissolved or retained because it is cured.
It becomes the picture below, the blue dry film is dissolved and washed away, and the purple cured one remains.
See the following figure, 5. Etching. In this step, unnecessary copper is etched, and the developed Board is etched with acidic copper chloride, the copper covered by the cured dry film will not be etched, and the uncovered ones will be etched. Left the needed line.
As shown in the following figure, 6. Film Removal. The film removal link is to wash off the cured dry film with sodium hydroxide solution.
During development, the uncured dry film is washed off, the film is washed off the cured dry film, and the two forms of dry film must be washed with different solutions.
So far, the circuits that reflect the electrical performance of the circuit board have been done well.
As shown in the following figure 7, drilling this step begins to punch holes, including the hole of the pad and the hole of the hole.
The following figure shows the PCB drill bit. The minimum drillable diameter of this mechanical drill bit is 0. 2mm hole.
Eight, copper deposition, electroplating this step is to plate the pad hole and the hole wall of the hole with a layer of copper and upper, and the lower two layers can be connected through the hole.
As shown in the following figure: the Via hole wall passes through the copper sinking, electroplating, Copper sinking production line, 9. Solder mask, solder mask is to apply a layer of green oil to the place where it is not welded, and it is not conductive to the outside world. This is through the screen printing process, apply green oil, and then follow the previous process, light exposure, development, and expose the pad to be welded.
As shown in the following figure, X. Silk screen printing and silk screen printing characters are printed with component labels, LOGO and some descriptive characters through screen printing.
Xi. Surface Treatment. This step is to do some treatment on the pad to prevent copper from oxidizing in the air, mainly hot air leveling (That is, spray tin)
, OSP, gold sinking, gold melting, gold fingers and other processes, as shown in the following figure is the OSP process used, is to add a layer of anti-oxide film on the pad, due to heating during welding, these films will automatically retreat.
Twelve, electrical testing, sampling, packaging, after the above production process, a PCB board is ready, but the board needs to be tested, whether there is a short circuit, it will be tested in an electric measuring machine.
After this series of processes, the PCB board is officially ready to be packaged.
Summary: PCB manufacturing process PCB manufacturing is very complicated, and then take the four-layer printed board as an example, the manufacturing process mainly includes PCB layout, core board manufacturing, inner PCB layout transfer, core board punching and inspection, lamination, drilling, copper chemical precipitation of hole wall, outer PCB layout transfer, outer layer PCB etching and other steps.
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