First, the inner layer; Mainly to do the internal circuit of PCB circuit board; The production process is as follows:

1, board cutting: cut PCB substrate to production size.

2. Pretreatment: clean the surface of PCB substrate to remove surface pollutants.

3. Film pressing: stick the dry film on the surface of PCB substrate to prepare for the subsequent image transfer.

4. Exposure: Exposure equipment is used to expose the substrate with the film by ultraviolet light, so as to transfer the image of the substrate to the dry film.

5. DE: Develop, etch and demould the exposed substrate, thus completing the manufacture of the inner panel.

Second, internal inspection; Mainly testing and repairing circuit boards.

1, AOI:AOI optical scanning, which can compare the image of PCB with the recorded data of good products, so as to find defects such as gaps and depressions on the board image.

2. VRS: The bad image data detected by AOI is transmitted to VRS, and relevant personnel will maintain it.

3. Wire patching: Weld a gold wire in the gap or depression to prevent electrical defects.

Third, suppression; As the name implies, it is to press multiple inner plates into one plate.

1, Browning: Browning can increase the adhesion between the board and the resin and increase the wettability of the copper surface.

2. Riveting: cut the PP into small pieces with normal size, so that the inner panel can fit the corresponding PP..

3. Stacking, pressing, shooting, trimming and grinding.

Fourth, drilling holes; According to the customer's requirements, holes with different diameters can be drilled with a drilling machine, so that holes can be punched between boards, which is convenient for subsequent processing of plug-ins and can also help the boards to dissipate heat.

5. Primary copper; Copper plating is carried out on the drilling holes of the outer plate to make the circuits of each layer of the plate conductive.

1, deburring line: deburring the edge of the plate hole to prevent poor copper plating.

2. Glue joint removal: remove the glue residue in the hole; So as to increase the adhesion during micro-etching.

3. Copper (pth): Copper plating in the hole makes each layer of the board conductive, and at the same time increases the thickness of copper.

Sixth, the outer layer; The outer layer is basically the same as the inner layer in the first step, and its purpose is to facilitate the subsequent process to make circuits.

1, pretreatment: clean the board surface by pickling, grinding and drying to increase the adhesion of dry film.

2. Film pressing: stick the dry film on the surface of PCB substrate to prepare for the subsequent image transfer.

3. Exposure: ultraviolet irradiation is carried out to make the dry film on the plate form polymerized and unpolymerized states.

4. Development: Dissolve the unpolymerized dry film during exposure, leaving a gap.

Seventh, secondary copper and etching; Secondary copper plating and etching.

1, copper 2: electroplating pattern, where the dry film is not covered in the hole, chemical copper shall be applied; At the same time, the conductivity and the thickness of copper are further increased, and then tin plating is carried out to protect the integrity of lines and holes during etching.

2.SES: Etch the bottom copper in the area where the external dry film (wet film) is attached through process treatment such as film removal, etching and tin removal to complete the external circuit.

Eight, solder resist: it can protect the circuit board and prevent oxidation.

1, pretreatment: pickling, ultrasonic water washing and other processes are carried out to remove the oxide on the board surface and increase the roughness of the copper surface.

2. Printing: cover the parts of PCB that don't need to be soldered with solder resist ink to protect and insulate.

3. Pre-baking: dry the solvent in the solder resist ink and harden the ink for exposure.

4. Exposure: The solder resist ink is cured by ultraviolet light irradiation, and a polymer is formed by photosensitive polymerization.

5. Development: removing the sodium carbonate solution in unpolymerized ink.

6. Post-baking: completely harden the ink.

Nine, the text; Printed text.

1, pickling: clean the surface of the plate, remove surface oxidation and strengthen the adhesion of ink.

2. Text: Print text to facilitate the subsequent welding process.

X. surface treatment OSP；; ; The side of bare copper plate to be welded is coated with an organic film to prevent rust and oxidation.

XI。 Forming; It is convenient for customers to install and assemble SMT boards.

Twelve, flying needle test; Test the circuit of the board to avoid the short circuit board from flowing out.

Thirteen. FQC； ; Final inspection, sampling and full inspection after the completion of all processes.

14. Packaging and delivery; Vacuum package PCB board, package and deliver, and complete delivery.

In order to obtain the best performance of electronic circuits, the layout of components and wires is very important. In order to design PCB. Good quality and low cost should follow the following general principles:

general layout

First consider the size of the PCB. Excessive PCB size, long printed line, increased impedance, decreased anti-noise ability and increased cost; Too small, heat dissipation is not good, and adjacent lines are easily disturbed. After determining the PCB size, determine the position of special components. Finally, according to the functional units of the circuit, all components of the circuit are laid out.

When determining the position of special parts, please follow the following principles:

① Shorten the wiring between high-frequency components as far as possible, and minimize their distribution parameters and mutual electromagnetic interference. Do not get too close to the easily disturbed components, and keep the input and output components as far away as possible.

② There may be a high potential difference between some elements or wires, so the distance between them should be increased to avoid accidental short circuit caused by discharge. High-voltage components should be arranged as far as possible in places that are hard to reach when debugging.

(3) Parts with weight exceeding 15 g shall be fixed with brackets and then welded. Those big, heavy and hot components should not be mounted on printed boards, but on the floor of the whole machine case, and heat dissipation should be considered. Heat sensitive elements should be far away from heating elements.

④ The layout of adjustable components such as potentiometer, adjustable inductance coil, variable capacitor and microswitch should consider the structural requirements of the whole machine. If it is adjusted in the machine, it should be placed above the printed board where it is easy to adjust; If it is adjusted outside the machine, its position should be suitable for the position of the adjustment knob on the chassis panel. ?

According to the functional units of the circuit, the layout of all components of the circuit shall conform to the following principles:

① Arrange the position of each functional circuit unit according to the circuit flow, so as to make the layout convenient for signal circulation and keep the signals in the same direction as much as possible.

② Centering on the core components of each functional circuit, layout is carried out around them. Components should be laid evenly, neatly and compactly on the PCB board, and the leads and connections between components should be reduced and shortened as much as possible.

(3) In high-frequency circuits, the distribution parameters between components should be considered. In general circuits, elements should be arranged in parallel as much as possible. This is not only beautiful, but also easy to assemble, weld and mass production.

④ Components located at the edge of the circuit board are generally not less than 2 mm away from the edge of the circuit board. The best shape of the circuit board is rectangular. The length-width ratio is 3: 2 or 4: 3. Is the surface size of the circuit board greater than 200 mm? 150 mm, the mechanical strength of the circuit board should be considered.

wiring

Its principles are as follows:

(1) The wires used for input and output terminals shall be as parallel as possible. It is best to add grounding wire between lines to avoid feedback coupling.

② The minimum width of printed circuit board leads is mainly determined by the adhesive strength between the leads and the insulating substrate and the current value flowing through them.

When the thickness of copper foil is 0.05 mm and the width is 1 ~ 15 mm, and the current is 2 A, the temperature will not be higher than 3℃, so the conductor width is1.5 mm. For integrated circuits, especially digital circuits, the line width of 0.02~0.3 mm is usually selected. Of course, as long as it is allowed, try to use wide wires, especially power and ground wires.

The minimum distance between wires is mainly determined by the worst insulation resistance and breakdown voltage between wires. For integrated circuits, especially digital circuits, the pitch can be as small as 5 ~ 8 um as long as the process allows. ?

(3) The bending of printed wires is generally circular, and the right angle or included angle will affect the electrical performance in high-frequency circuits. In addition, try to avoid using a large area of copper foil, otherwise the copper foil will easily swell and fall off after heating for a long time. When a large area of copper foil must be used, it is best to use a grid shape, which is beneficial to eliminate the volatile gas generated by the heating of the adhesive between the copper foil and the substrate.

Binding zone

The central hole of the pad is slightly larger than the diameter of the device lead. If the pad is too large, it is easy to form virtual welding. The outer diameter d of the gasket is generally not less than d+ 1.2 mm, where d is the lead aperture. For high-density digital circuits, the minimum diameter of the pad can be d+1.0 mm. ..