PCB News - What problems should be paid attention to in the use of components in the PCB proofing process?

What problems should be paid attention to in the use of components in the PCB proofing process?

In the PCB circuit board proofing, the reasonable and effective use of components is an important guarantee for the stability and quality of the circuit board. So, what issues should be paid attention to when using components in the PCB proofing process?

1. Limit the output current to avoid the locking effect of the CMOS circuit:

The lock-in effect refers to the existence of parasitic PNP transistors and NPN transistors in the internal structure of the CMOS circuit, and a parasitic PNPN thyristor structure is formed between them.
The common solution is to use a resistor to isolate each output terminal from its cable, and use two high-speed switching diodes to clamp to VDD (drain power) and VSS (source power) with the cable. .

2. Use filter network:

Sometimes a long input cable is required between the CMOS circuit system and the mechanical contacts, which increases the possibility of electromagnetic interference, and a filter network should be considered.

3. Form RC network:

For the sensitive input terminals of bipolar devices, an RC network composed of a resistor with a larger resistance value and a capacitor of at least 100pF can be used to reduce the impact of electrostatic discharge.

4. Avoid floating the input pins of CMOS devices:

This is because once the input pin is suspended, the input potential will be in an unstable state, which will not only destroy the normal logical relationship of the circuit, but also easily cause electrostatic breakdown and external noise interference. The redundant input terminal should be handled separately according to the function of the circuit.

The above are a few issues that engineers should pay attention to when using components in the PCB proofing process detailed by engineers. I hope it will be helpful to our customers and friends. iPCB is a high-tech manufacturing enterprise focusing on the development and production of high-precision PCBs. iPCB is happy to be your business partner. Our business goal is to become the most professional prototyping PCB manufacturer in the world. Mainly focus on microwave high frequency PCB, high frequency mixed pressure, ultra-high multi-layer IC testing, from 1+ to 6+ HDI, Anylayer HDI, IC Substrate, IC test board, rigid flexible PCB, ordinary multi-layer FR4 PCB, etc. Products are widely used in industry 4.0, communications, industrial control, digital, power, computers, automobiles, medical, aerospace, instrumentation, Internet of Things and other fields.