sales@ipcb.com
To manufacture PCBs, the first step is PCB design, which is usually done through CAD (Computer Aided Design). CAD is used to draw schematics and design the layout of the PCB. Possible errors can be detected in advance before the PCB is manufactured. After testing and checking the correct alignment and location of all components on the PCB, the PCB can be manufactured according to the layout.
The general PCB design flow is as follows: Pre-preparation; PCB Structure Design; PCB Layout; Layout; Layout Optimisation and Silkscreen; Network and DRC Check and Structure Check; PCB Fabrication.
First: Pre-preparation. This includes preparing component libraries and schematics. ‘Workers must sharpen their tools before they can do their job well.’ To make a good board, in addition to designing the schematic, you have to draw it. Before proceeding with the PCB design, first prepare the schematic SCH component library and the PCB component library. Component library can use peotel's own library, but it is generally difficult to find the right one. It is better to make your own library according to the standard size data of the selected device. In principle, PCB libraries should be made first, then SCH libraries. PCB libraries are very demanding and have a direct impact on board installation. SCH component library requirements are relatively loose, as long as attention to the definition of the pin content and correspondence with the PCB components can be. PS: Pay attention to the hidden pins in the standard library. After that is the schematic design, after which we can start the PCB design.
Second:PCB structure design.In this step, according to determine the size of the circuit board and a variety of mechanical positioning, PCB design environment to draw the PCB surface, and according to the positioning requirements to place the required connectors, buttons / switches, screw holes, assembly holes and so on. And fully consider and determine the wiring area and non-wiring area (such as screw holes around how much area belongs to the non-wiring area).
Third: PCB layout.To be frank, layout is to put the device on the board. At this point, if all the above preparations are done, you can generate a netlist on the schematic (Design->Create Netlist), and then import the netlist on the PCB (Design->Load Nets). You can see that the whole device stack is collapsed and there are flying wires between the pins to illustrate the connections.
PCB
Then you can set up your equipment. The general layout is based on the following principles:
1.According to the reasonable division of power efficiency, generally divided into: digital circuit area (i.e., fear of interference and interference), analogue circuit area (fear of interference), power drive area (interference source).
2.Circuits performing the same function should be placed as close together as possible, and components should be adjusted to ensure the simplest connection.At the same time,adjust the relative positions of the function blocks so that the connections between the function blocks are as simple as possible.
3.For high quality components, consider the mounting position and mounting strength.Heat generating electronic components should be placed separately from temperature sensitive components,and thermal convection measures should be considered if necessary.
4.Locate I/O drivers as close as possible to the board edges and lead-in connectors.
5.Clock generators (e.g. crystal oscillators or clock oscillators) should be located as close as possible to the equipment that uses the clock.
6.A decoupling capacitor (typically a monolithic capacitor with good high-frequency performance) between the power input pin and ground of each IC.A tantalum capacitor can also be added around the IC when the board space is dense.
7. Relay coil to add a discharge diode (1N4148 is enough).
8. Layout requirements should be balanced, dense, orderly, not top-heavy.
Special attention is required.When placing components,the actual size of the components (occupied area and height) and the relative position of the components must be taken into account to ensure the electrical performance of the circuit board and the feasibility of production and installation. At the same time, for the sake of convenience, under the premise of guaranteeing that the above principles can be embodied,the placement of the components should be modified appropriately so that they can be placed neatly and aesthetically. For example, the same components should be neatly placed in the same direction.
Previous PCB design often focus on the visual effect of the circuit board, but now it is different.The automatically designed PCB is not as beautiful as the manually designed one, but the electronic effects can satisfy the specified requirements and ensure the complete performance of the PCB design.