What Is PCB Circuit Design?
PCB design is based on the circuit schematic diagram to realize the design of specific functions on the PCB board. PCB design should take into account various factors such as layout design, external connection layout, and optimal layout of internal electronic components.
The role of PCB design is to standardize design operations, improve production efficiency and improve the quality of electronic products.
Materials Needed for PCB Design
1. Schematic: A complete electronic document format that produces the correct netlist (providing the layout and functionality required by the PCB)
2. Mechanical dimensions: Provide PCB with physical information such as the specific location and direction identification of electronic devices
3. Device packaging: Provide device packaging library, packaging methods and electronic material specifications for PCB circuit boards
4. Wiring guide: Provide specific signal requirements description, impedance and other design for PCB
PCB Circuit Design Process
1. Netlist input
2. Rule setting
3. Component layout
4. Wiring
5. Inspection and Review
6. Design Output
1. Netlist Input
There are two ways to input the netlist. One is to use the OLE Power PCB Connec TIon function of Power Logic, select Send Netlist, and apply the OLE function to keep the schematic diagram and PCB diagram consistent at any time and minimize the possibility of errors.
Another method is to directly load the netlist in Power PCB, select Fil-Import, and import the netlist generated by the schematic.
2. Rule Setting
If the design rules of the PCB have been set in the schematic design stage, there is no need to set these rules, because when the netlist is input, the design rules have been entered into Power PCB along with the netlist.
If the design rules are modified, the schematic diagram must be synchronized to ensure that the schematic diagram and the PCB are consistent. In addition to design rules and layer definitions, there are some rules that need to be set, such as Pad Stacks, which need to modify the size of standard vias. If the designer creates a new pad or via, be sure to add Layer 25.
Note: PCB design rules, layer definitions, via settings, and CAM output settings have been made into a default startup file named Default.stp. After the netlist is imported, the power network and ground are assigned to the power layer according to the actual design situation. and strata, and set other advanced rules.
After all the rules are set, in Power Logic, use the Rules From PCB function of OLE Power PCB ConnecTIon to update the rule settings in the schematic diagram to ensure that the rules of the schematic diagram and the PCB diagram are consistent.
3. Component Layout
After the netlist is input, all components will be placed at the zero point of the workspace and overlapped together. The next step is to separate these components and arrange them neatly according to some rules, that is, component layout.
Power PCB provides two methods, manual layout and automatic layout.
Manual layout
A. Draw the board outline for the structural dimensions of the tool printed board.
B. Disperse Components, the components will be arranged around the edge of the board.
C. Move and rotate the components one by one, put them within the edge of the board, and arrange them neatly according to certain rules.
Auto Layout
Power PCB provides automatic layout and automatic local cluster layout, but for most designs, the effect is not ideal and is not recommended.
Precautions
A. The first principle of layout is to ensure the routing rate of wiring, pay attention to the connection of the flying wires when moving the device, and put the connected devices together
B. Digital devices and analog devices should be separated and kept as far away as possible
C. Place the decoupling capacitor as close as possible to the VCC of the device
D. Consider future soldering when placing devices, not too dense
E. Use the Array and Union functions provided by the software to improve the efficiency of layout
4. Wiring
There are also two ways of wiring, manual wiring and automatic wiring. The manual routing functions provided by Power PCB are very powerful, including automatic pushing and online design rule checking (DRC). Automatic routing is performed by Specctra’s routing engine. Usually these two methods are used together.
Manual wiring
A. Before automatic wiring, manually lay out some important networks, such as high-frequency clocks, main power supplies, etc. These networks often have special requirements for wiring distance, line width, line spacing, shielding, etc. Such as BGA, it is difficult to arrange automatic routing in a regular manner, and manual routing is also required.
B. After the automatic wiring, the wiring of the PCB should be adjusted by manual wiring.
auto-routing
After the manual routing is over, the rest of the network is handed over to the autorouter from the fabric. Select Tools->SPECCTRA, start the interface of the Specctra router, set the DO file, and press ConTInue to start the automatic wiring of the Specctra router. After the end, if the routing rate is 100%, then you can manually adjust the wiring; if not When it reaches 100%, it means that there is a problem with the layout or manual routing, and the layout or manual routing needs to be adjusted until all the layouts are completed.
Precautions
A. Make the power and ground wires as thick as possible
B. The decoupling capacitor should be directly connected to VCC as much as possible
C. When setting up Specctra’s DO file, first add the Protect all wires command to protect manually routed wires from being rerouted by the autorouter
D. If there is a mixed power supply layer, this layer should be defined as Split/mixed Plane, and it should be divided before wiring. After wiring, use Pour Manager’s Plane Connect for copper pouring
E. Set all device pins to thermal pad mode by setting Filter to Pins, selecting all pins, modifying properties, and ticking before Thermal option
F. Turn on the DRC option during manual routing and use Dynamic Route
5. Inspection and Review
Check: Checked items include spacing, connectivity, high-speed rules, and power planes. These items can be selected from Tools->Verify Design. If a high-speed rule is set, it must be checked, otherwise this item can be skipped. Errors are detected and placement and routing must be modified.
Note: Some errors can be ignored. For example, part of the Outline of some connectors is placed outside the board frame, and errors will occur when checking the spacing; in addition, after each modification of the traces and vias, the copper must be re-clad.
Review
The review is based on the “PCB checklist”, which includes design rules, layer definition, line width, spacing, pads, and via settings; it is also important to review the rationality of device layout, power supply, ground network routing, and high-speed clock network. The wiring and shielding, placement and connection of decoupling capacitors, etc.
If the review fails, the designer should revise the layout and wiring. After passing the review, the reviewer and the designer sign respectively.
6. Design Output
The PCB design can be output to a printer or output as a light drawing file. The printer can print the PCB in layers, which is convenient for designers and reviewers to check.
The light drawing file is handed over to the board manufacturer to produce the printed board. The output of light drawing files is very important, which is related to the success or failure of this design. The following will focus on the precautions for outputting light drawing files.
A. The layers that need to be output are wiring layer (including top layer, bottom layer, middle wiring layer), power layer (including VCC layer and GND layer), silk screen layer (including top layer silk screen, bottom layer silk screen), solder mask layer (including top layer solder mask) and bottom solder mask), in addition to generate a drill file (NC Drill)
B. If the power layer is set to Split/Mixed, then select Routing in the Document item of the Add Document window, and use Pour Manager’s Plane Connect to copper-clad the PCB diagram each time before outputting a light drawing file;
C. If it is set to CAM Plane, select Plane. When setting the Layer item, add Layer25, and select Pads and Viasc in the Layer25 layer. In the device setting window, change the value of Aperture to 199
D. When setting the Layer of each layer, select Board Outline
E. When setting the Layer of the silk screen layer, do not select Part Type, select the top layer (bottom layer) and Outline, Text, Line of the silk screen layer
F. When setting the Layer of the solder mask layer, select the via hole to indicate that no solder mask is added to the via hole, and not to select the via hole to indicate the home solder mask, which is determined according to the specific situation.
G. When generating the drill file, use the default settings of PowerPCB and do not make any changes
H. After all light drawing files are output, open and print with CAM350, and check by designers and reviewers according to the “PCB Checklist”
IPC Standards Commonly Used in PCB Circuit Design
Why Are IPC Standards Important?
The IPC standard ensures that manufacturers make safe, reliable, and high-performance PCB boards by focusing on manufacturing details and working to maintain quality throughout the manufacturing process.
These standards help different companies maintain the same parameters for PCB quality assurance and reliability so that they can meet customer expectations and production process improvements in many different ways.
The Ipc Standard Supports PCB Manufacturers in Several Ways
Maintain the quality and reliability of the final product: IPC standards will help manufacturers make products of higher quality and reliability. When manufacturers maintain standards from the very first steps of the manufacturing process, the final product will perform better and last longer. Product quality and reliability should be maintained to compete in the electronics industry, so manufacturers should always maintain these two factors.
Consistency: Maintaining consistency in quality and other parameters is the most difficult task for manufacturers. By maintaining IPC certification, PCB manufacturers can maintain their consistency and ultimately increase customer satisfaction.
Better Communication: IPC standards ensure that the same language is used internally and externally to define terms related to the life cycle of electronic equipment, which also reduces the risk of communication errors. With IPC standards, customers, suppliers, suppliers, regulators and others involved in the process will be able to better communicate with each other.
Maintain your reputation: IPC is an internationally recognized standard, so everyone in the electronics industry knows it. If you hire a new employee who doesn’t know anything about your company and you follow IPC standards in your industry, he/she will no doubt follow your reputation without difficulty. Therefore, this process will improve the quality of your products and improve your reputation so that you will be able to attract more customers to buy your products.
Lower costs: When you follow IPC standards in every step of the manufacturing process, the final product will be of better quality and it will also be reliable to use, so there is no need to quality check every product it is manufactured, which Will reduce the cost of testing. Since everyone in the process communicates using the same terminology, there is also less chance of delays and rework due to miscommunication, which also cost the company.
Commonly Used IPC Standards
IPC-2581: It is a standard for sending information between a PCB circuit designer and a manufacturer or assembly company. It helps provide a standardized format for exchanging design data, which helps ensure consistent production results.
IPC-2221: This is a standard for designing PCBs that addresses topics related to PCB circuit design such as design, layout, materials, mechanical and physical properties, electrical properties, thermal limitations, parts lists and more.
IPC-6012B: It determines the qualifications and performance required for rigid PCB manufacturing. It meets product requirements in terms of structural integrity, solderability and conductor spacing.
IPC-A-600F: It sets the acceptable standard for the PCB, it describes what the target condition of the PCB is, and what are the acceptable and non-compliant conditions for all parts of the PCB. It describes everything from gold fingers to copper plating.
IPC-TM-650: IPC publishes Test Methods for PCB Boards under IPC-TM-650, which provides guidelines for evaluating various aspects of a PCB. It provides a test method to test the surface electromagnetic migration tendency of a board, measure the resistance to current passing through the surface of a PCB substrate, a method of ionic cleanliness test, etc.
In addition to these standards, there are many more standards for every aspect of PCB circuit design, even the tiniest aspects you can’t imagine. All of these positions are dedicated to delivering reliable and better electronics.
About Wonderful
Shenzhen Wonderful Technology Co., Ltd. is China’s top model and small batch circuit board manufacturer.
The company targets precision circuit board samples and small batches as the main target market. Since its establishment, it has adhered to the development concept of good quality and important reputation.
Invest huge sums of money to introduce advanced equipment, strictly regulate the operating standards and QC standards for incoming and outgoing materials, to ensure that the shipped products reach Seiko quality.
The self-developed ERP management system can realize the whole process of paperless operations such as online ordering, online payment, online production progress query, online logistics tracking, and online statistical report production, which greatly improves work efficiency.
It ensures that each order can be shipped quickly. After more than ten years of development, the company’s products and services have been well received by the market.
As well as the opening of an electronic component mall, integrated circuits, semiconductors, resistors, capacitors and other products are sold.
The company’s scale is developing rapidly, and the sample and small batch shipment capacity reaches 500 models/day.
The products are widely used in communications, medical equipment, industrial control products, aviation, military products, testing instruments,Automotive, computers and other peripheral products.
We will continue to pay attention to customers, with efficient delivery speed and perfect after-sales service, to become the most trusted brand supplier in the PCB industry.
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