1. System specifications
First, we must first plan the system specifications of the electronic equipment. Contains system features, cost limits, size, operating conditions, and more.
2. Next, you must create a functional block diagram of the system. The relationship between the squares must also be marked.
3. Split the system into several PCBs
Dividing the system into several PCBs not only reduces the size, but also allows the system to upgrade and exchange parts. The system function block diagram provides the basis for our segmentation. Like a computer, it can be divided into a motherboard, a display card, a sound card, a floppy disk drive, a power supply, and the like.
4. Decide to use the packaging method, and the size of each PCB
When the number of technologies and circuits used in each PCB is determined, the next step is to determine the size of the board. If the design is too large, then the packaging technology will change, or re-segmentation. When choosing a technology, you should also consider the quality and speed of the roadmap.
5. Draw a circuit diagram of all PCBs
The details of the interconnections between the parts are shown in the overview. PCBs in all systems must be traced, and most of them today use CAD (Computer Aided Design).
PCB circuit diagram
1. Preliminary design simulation operation
In order to ensure that the designed circuit diagram can work properly, this must first be simulated with computer software. This type of software can read the design and display the operation of the circuit in many ways. This is much more efficient than actually making a sample PCB and then using manual measurements.
2. Place the part on the PCB
The way parts are placed is determined by how they are connected. They must be connected to the path in the most efficient way. The so-called efficient wiring is that the shorter the tie line and the fewer the number of passes through the layer (which also reduces the number of via holes). In order for each part to have perfect wiring, the placement is important.
3. Test wiring possibilities, and operate correctly at high speed
Some of today's computer software can check whether the position of each part is properly connected, or check whether it can operate correctly at high speed. This step is called arranging parts. If there is a problem with the circuit design, the position of the part can be rearranged before the line is exported in the field.
4. Export the line on the PCB
The connections in the overview will now be made in the field. This step is usually fully automated, but in general it is necessary to manually change some parts. The final composition of the PCB is often referred to as Artwork.
Each design must conform to a set of regulations, such as minimum retention gaps between lines, minimum line width, and other similar practical limits. These regulations vary according to the speed of the circuit, the strength of the transmitted signal, the sensitivity of the circuit to power consumption and noise, and the quality of the material and manufacturing equipment. If the current intensity rises, the thickness of the wire must also increase. In order to reduce the cost of PCBs, it is also necessary to pay attention to whether these regulations are still met while reducing the number of layers. If more than two layers of construction are required, then the power and ground planes are typically used to avoid transmission signals on the signal layer and to act as a shield for the signal layer.
5. Wire post circuit test
In order to determine that the line is functioning properly after the wire, it must pass the final test. This test can also check for incorrect connections and all connections go as shown.
6. Create a production file
Because there are many CAD tools for designing PCBs, manufacturers must have standards-compliant files to make boards. There are several standard specifications, but the most common one is the Gerber files specification. A set of Gerber files includes a plan view of each signal, power supply, and ground plane, a plan view of the solder mask and screen print surface, and designated files such as drill holes and pick and place.
Electromagnetic compatibility problem
Electronic devices that are not designed to EMC (electromagnetic compatibility) specifications are likely to emit electromagnetic energy and interfere with nearby appliances. EMC imposes maximum limits on electromagnetic interference (EMI), electromagnetic fields (EMF), and radio frequency interference (RFI). This regulation will ensure the normal operation of the appliance and other nearby appliances. EMC has strict limits on the energy of a device that scatters or conducts to another device, and is designed to reduce the magnetic susceptibility of external EMF, EMI, RFI, etc. In other words, the purpose of this regulation is to prevent electromagnetic energy from entering or being emitted by the device. This is actually a difficult problem to solve. Most of them use power and ground planes, or put PCBs in metal boxes to solve these problems. The power and ground planes prevent the signal layer from being disturbed, and the metal box is similar in effectiveness. We are not too deep on these issues.
The maximum speed of the circuit depends on how it is done according to EMC regulations. Internal EMI, like the current consumption between the conductors, increases as the frequency increases. If the current difference between the two is too large, then the distance between the two must be lengthened. This also tells us how to avoid high voltages and minimize the current consumption of the circuit. The delay rate of the wiring is also important, so the length is naturally as short as possible. Therefore, a small PCB with good wiring will be more suitable for operation at high speed than a large PCB.