PCB Tech - What are the wiring principles for automotive circuit boards?

What are the wiring principles for automotive circuit boards?

Wiring is an important part of PCB design, which directly affects the performance of PCB.

How to connect the car circuit board? Here are some principles to share with you.

1. Generally speaking, the power line and the ground line should be connected first to ensure the electrical performance of the circuit board. Within the allowable range, the width of the power and ground lines should be as wide as possible, and the ground line should preferably be wider than the power line. Their relationship is: ground wire>power wire>signal wire. The signal line width is generally 0.2～0.3mm, the thinnest width is 0.05～0.07mm, and the power line is 1.2～2.5mm. The PCB of the digital circuit can form a loop with a wide ground wire, that is, use a ground wire network (an analog circuit cannot be used in this way).

2. For lines with strict requirements for pre-wiring (such as high-frequency circuit boards), the input end and output end should avoid adjacent parallel lines to avoid reflection interference. If necessary, the ground line should be isolated, and the wiring of two adjacent layers should be perpendicular to each other, so parasitic coupling can easily occur in parallel.

3. The case of the oscillator is grounded, and the clock line should be as short as possible and should not be caused anywhere. In the clock oscillation circuit, the special high-speed logic circuit should increase the grounding area instead of adding other signal lines, so that the surrounding electric field tends to zero.

4. In order to reduce the radiation of high-frequency signals, 45-degree folded wiring should be used as much as possible instead of 90-degree folded wiring (double arcs should be used for circuits with strict requirements).

5. No signal line should form a loop. If it is unavoidable, the loop should be as small as possible. The number of holes in the signal line should be as small as possible.

6. The key line should be as short and thick as possible, and protection areas should be added on both sides.

7. When transmitting sensitive signals and noise field band signals through flat cables, the "ground signal-ground" method must be used to extract them.

8. Test points should be reserved for key signals of production and maintenance.

9. After completing the principle wiring, the wiring should be optimized. At the same time, after the initial network check and DRC check are correct, the unused area is filled with the ground wire, the large area copper layer is used as the ground wire, and the unused position is used as the ground wire to connect to the ground wire on the PCB board. Or it can be made into multiple layers, one for each power layer and one for each ground wire layer.

After mastering the above points, I believe your PCB design ability will be greatly improved.