Questions and answers about eight common questions about PCB circuit board design technology

PCB technology is very complicated, and there are many problems involved in all aspects. Whether it is in the design stage or the production stage, I believe there will be many questions that need to be answered. The following are ten frequently asked questions about pcba manufacturer circuit board design technology.

1. When designing a system with DSP and PLD, which aspects should be considered for ESD?
Answer: As for the general system, it is mainly considered that the parts in direct contact with the human body should be properly protected on the circuit and mechanism. As for how much impact ESD will have on the system, it depends on different situations.

2. In the EMC test, it was found that the harmonics of the clock signal exceeded the standard very seriously, but the decoupling capacitor was connected to the power supply pin. What aspects should be paid attention to in the design to suppress electromagnetic radiation?

Answer: The three elements of EMC are radiation source, transmission path and victim; transmission path is divided into space radiation propagation and cable conduction. So to suppress harmonics, first look at the way it spreads. Power supply decoupling is to solve the propagation of conduction mode. In addition, necessary matching and shielding are also required.

3. Among the products with 4-layer board design, why some are surface paving, and some are not?

Answer: The function of paving: 1. Shielding; 2. Heat dissipation; 3. Reinforcement; 4. Process processing needs. Regardless of how many layers of slabs are laid, we must first look at the main reasons. Here we mainly discuss high-speed issues. Surface paving is good for EMC, but copper paving should be as complete as possible to avoid islands.

4. For boards with a frequency above 30M, use automatic wiring or manual wiring when wiring?
Answer: Automatic or manual wiring depends on the support of the software wiring function. Some wiring may be better than automatic wiring manually, but some wiring, such as checking distribution lines, bus delay compensation wiring, the effect and efficiency of automatic wiring will be much higher than manual wiring .

5. In the design, the ground wire is usually divided into protective ground and signal ground; the power ground is divided into digital ground and analog ground. Why is the ground wire divided?

Answer: The purpose of dividing the ground is mainly for EMC considerations, and it is worried that the noise on the digital part of the power supply and the ground will interfere with other signals, especially the analog signal through the conduction path. No matter how you divide it, there is only one land in the end.

6. Is it necessary to add ground wire shields on both sides when fabricating the clock?
Answer: Whether to add a shielded ground wire or not depends on the crosstalk/EMI situation on the board. If the shielded ground wire is not handled well, it may make the situation worse.

7. What countermeasures are there to deploy clock lines of different frequencies?
Answer: For the wiring of the clock line, it is best to conduct signal integrity analysis, formulate corresponding wiring rules, and perform wiring according to these rules.

8. How to indicate the jumper when single-layer board is manually wired?

Answer: The jumper is a special device in the design. There are only two pads. The distance can be fixed or variable. It can be added as needed during manual wiring. There will be a direct connection on the board, and it will also appear in the bill of materials.

The above are the eight frequently asked questions about PCB pcb prototype circuit board design technology. How much do you know?