PCB (Printed Circuit Board, Printed Circuit Board) is a basic and critical components. PCB board production process is very important, the following details of its main steps flow as follows:
A. The Design Schematic and Layout:
In the PCB board production process, the first need to design the schematic diagram and layout. Designers use professional circuit design software to draw the circuit connection diagram, and determine the location of circuit components, size and layout rules.
B.PCB Design:
According to the schematic diagram and layout rules, the designer uses PCB design software to design the PCB. The design includes wiring, laying copper, adding component pins and wires.
C. The Output Gerber File:
After completing the PCB design, you need to export the design results into a Gerber file. Gerber file is a standard PCB production file format, contains the board’s laminated information, component locations and pads and other data. PCB production file format also contains CAD, 99sE two formats.
If you already have the relevant drawing information, You can send an attachment to sales4@xcepcb.com , we quote you a satisfactory price.
D. PCB Board:
After getting the Gerber (or CAD, 99sE) file, Xinchenger factory engineers will analyze it and make PCB according to the file. Board including the coating of photopolymer, exposure, development and etching steps, the final formation of copper board with circuit alignment.
a. Inner Layer: Mainly for the production of PCB circuit boards for the inner layer of the line;
The production process is:
1, Cut Board: PCB substrate cut to production size.
2, Pre-treatment: Clean the surface of the PCB substrate to remove surface contaminants.
3, Pressure film: The dry film on the surface of the PCB substrate to prepare for the subsequent image transfer.
4, Exposure: The use of exposure equipment using ultraviolet light on the laminated substrate exposure, so that the image of the substrate will be transferred to the dry film.
5, DE: Will be exposed after the substrate through the development, etching, film, and then complete the production of the inner layer of the board.
b. Internal Inspection: Mainly to detect and repair the board line.
1, AOI: AOI optical scanning, can be the image of the PCB board and has been recorded good board data for comparison, in order to find the board image above the gap, depression and other bad phenomena.
2, VRS: AOI detected by the bad image data transmitted to the VRS, by the relevant personnel for overhaul.
3, Fill Line: The gold wire will be soldered on the gap or depression to prevent electrical malpractice.
c. Press-fit: As the name suggests, it is to press several inner laminates into one board.
1, Browning: Browning can increase the adhesion between the board and resin, as well as increase the wettability of the copper surface.
2, Riveting: PP will be cut into small sheets and normal size so that the inner layer of the board and the corresponding PP MouJin.
3, Stacking and Pressing, hitting the target, gong edge, grinding edge.
E. Plating:
After making the PCB board needs to be plated to increase the conductivity of the circuit alignment and corrosion resistance. This step includes surface treatment, pickling, passivation and copper plating process.
F. Drilling:
Holes need to be drilled in the PCB to mount components and connect laminates. This process step uses a drill press to locate and drill holes in the board to ensure the accuracy of the hole diameter and location.
a. A copper: For the outer layer of the board has been drilled holes plated with copper, so that the board of all layers of line conduction.
1, Deburring line: Remove the burrs on the edge of the holes of the board to prevent bad copper plating.
2, In Addition to The Glue Line: Remove the hole inside the glue residue; in order to increase the adhesion in the micro-etching.
3, A Copper (PTH): Copper-plated holes to make the board layers of line conduction, while increasing copper thickness.
b. The Outer Layer: The outer layer with the first step of the inner layer of the process is roughly the same, its purpose is to facilitate the subsequent process to make the line.
1, Pre-processing: By pickling, grinding and brushing and drying to clean the surface of the board in order to increase the adhesion of the dry film.
2, Pressure Film: The dry film on the PCB substrate surface, for the subsequent image transfer to prepare.
3, Exposure: UV light irradiation, so that the dry film on the board to form a polymerized and unpolymerized state.
4, Development: Will not be polymerized in the exposure process of dry film dissolved, leaving the pitch.
c. The second copper and etching; the second copper plating for etching;
1, The Second Copper: Electroplating graphics, for the holes are not covered with dry film in the place of the ferry chemical copper; while further increasing the conductivity and copper thickness, and then after tin plating to protect the integrity of the line, the holes when etching.
2, SES: Through the film, etching, tin stripping and other processes to deal with the outer dry film (wet film) attached to the area of the bottom of the copper etching, the outer layer of the line to the completion of the production.
G. Lower Material:
After drilling, PCB boards need to be designed according to the requirements of the material. This includes cutting the board into the required size, and edge polishing treatment to make the board flat and smooth.
1, Pre-processing: Acid washing, ultrasonic washing and other processes to remove board oxides and increase the roughness of the copper surface.
2, Printing: Cover the PCB boards with solder resist ink where soldering is not required to protect and insulate the boards.
3, Pre-baking: Drying the solvent inside the solder resist ink, and at the same time make the ink harden for exposure.
4, Exposure: Curing solder resist ink by UV light irradiation, forming polymer through photosensitive polymerization.
5, Developing: Remove the sodium carbonate solution inside the unpolymerized ink.
6, After Baking: So that the ink is completely hardened.
H. Pad Coverage:
In order to facilitate the welding of components, PCB board pads need to be covered to prevent oxidation and other phenomena. Covering material can be solder paste or spray tin.
I. Component Installation:
After the completion of the pad coverage, the use of automatic mounter or manual way to accurately install the components on the PCB board. At the same time need to be soldered to ensure a reliable connection between the components and pads.
J. Cleaning and Testing:
After completing the installation of components, the PCB board needs to be cleaned to remove surface residues. Then conduct strict electrical performance tests and appearance checks to ensure the quality of the PCB board.
K. Final Board Test:
After testing, the need for final board testing to verify that the performance of the PCB board meets the design specifications. Tests include connectivity tests, electrical characteristics tests and reliability tests.
L. Packaging and Delivery:
PCB boards that pass the final board test will be packaged appropriately and delivered to customers or production lines for use.
The above is the main process of PCB board production. Our company requires strict operation and control in each step of the PCB printing process to ensure the quality and performance of the PCB board. As far as we are concerned, making high quality PCBs is crucial to the stability and reliability of electronic products. This is also our responsibility to our customers, and at the same time, it is also our unchanging mission!
PCB Design Schematic and Layout
A. Design Process:
1, Circuit schematic design: Circuit schematic design is mainly the use of Protel DXP schematic editor to draw the schematic.
2, Generate network statements: Network statements is to show the circuit schematic and the link between each component in the report, it is connected to the circuit schematic design and circuit board design of the bridge and link, through the circuit schematic network statements, you can quickly find the link between the components, so as to provide convenience for the back of the PCB design.
3, PCB circuit board design: PCB design is based on the circuit schematic diagram to achieve the desired function, the design of PCB diagrams, you need to consider a lot of factors, including the structure of the machinery, the external connection layout, the layout of the components, wiring, heat dissipation, electromagnetic compatibility and so on. In order to finalize this step often requires numerous revisions of the circuit schematic.
4, PCBA control board production: After procurement of components, PCB board to get, in accordance with the schematic, after the SMT on the pieces, welded on a variety of components, and DIP plug-in process, so that our control board on the production is complete.
B. The Principle of Component Placement
First of all, placed with the structure of the components have a close match, such as power sockets, indicators, switches, connectors, interfaces, etc.; Second, placed special components, such as large components, heavy components, heat components, IC, etc.; Finally, placed small components; components should be considered when the layout of the line, try to choose the layout design that facilitates the wiring.
- 1, Crystal should be placed close to IC;
- 2, IC decoupling capacitor layout should be as close as possible to the IC’s power supply pins, and make the shortest loop formed between the power supply and ground;
- 3, Heat-generating components should generally be evenly distributed to facilitate the heat dissipation of the single board and the entire machine, in addition to temperature detection components other than temperature-sensitive devices should be away from the components that generate large amounts of heat.
C. Alignment Principles
1, High-speed signal alignment as short as possible, the key signal alignment as short as possible;
2, An alignment do not play too many over-holes, not more than two over-holes;
3, The alignment corners should be greater than 90 degrees as far as possible, to eliminate the corners below 90 degrees, but also minimize the use of 90-degree corners;
4, Double-sided panel wiring, the two sides of the wire should be mutually perpendicular, diagonal, or bent alignment, avoid parallel to each other, in order to reduce parasitic coupling;
5, The audio input line should be equal in length, the two lines are placed close to each other, and the audio line is outsourced to the ground;
6, The amplifier IC can not walk under the line, amplifier IC under the more than over the hole and GND connection;
7, No ground layer in the double-sided panel, the crystal capacitor ground should be used as far as possible to connect a short line to the device away from the nearest crystal GND pin, and try to reduce the number of holes;
8, The power cord, USB charging input to go thick line (“= 1mm), over the hole at both sides of the copper, and then in the copper laying a few more holes.
In general, the first thing to do is to wire the power and ground lines to ensure the electrical performance of the circuit board. Within the scope of conditions allow, try to widen the power supply, ground line width, it is best to ground line than the power line width, their relationship is: ground > power line > signal line, usually the signal line width: 0.2 ~ 0.3mm, the thinnest width of up to 0.05 ~ 0.07mm, the power line is generally 1.2 ~ 2.5mm.
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