Not to Touch PCB Boards by Hands

It is the common sense for PCB engineers that man can not touch the circuit boards directly by bare hands, but why? In this article, let’s find the reasons together.

1.The dangers of static electricity

Under different circumstances, electrostatic voltage carried by human body vary from several volts to hundreds volts to tens of thousands of volts. Touch electronic components directly by bare hands will generate electrostatic discharge, then devices are easily damaged and reliability are reduced; even worse, electrostatic discharge can make causes the device breakdown at once.

In addition, the electrostatic discharge process simultaneously radiates radio waves at a certain frequency and interferes with peripheral microprocessors, causing the application to run in disorder and seriously affecting the normal operation of the device.

Therefore, try to avoid direct human contact with electronic components in the daily work, especially in the charged state.

2.Effect by static electricity on the core board feedback loop

Human touch (the introduction of human equivalent resistance and other interference) can change the characteristic of feedback loop (including the pole offset), resulting in feedback loop oscillation and instable DC-DC output voltage.

Instable DC-DC output voltage can make the system restart (DC-DC automatically reduce the output voltage), even worse, it will burn out the main circuit board (DC-DC automatically adjusts the output voltage), thus the charged motherboard is not allowed to touch.

3.How to prevent the static electricity

a.anti-static cordless wrist band

According to the corona discharge effect and the principle of the tip discharge, when the accumulated charge exceeds a certain value, the potential difference is discharged to the space to achieve the purpose of eliminating static electricity. Static dissipative time: less than 0.5s; features: convenient, reliable.

b.anti-static wrist strap

Human skin contacts with the wrist strap made from the static conductive material directly, thus when the wrist strap grounding, discharge static electricity generated by human can be quickly discharged. Electrostatic discharge time is less than 0.1s.

c.anti-static PU coating gloves

Anti-static PU coating gloves can further prevent static electricity from being transmitted to printed circuit boards by hand contact. Hand back conductive wire spacing is 10mm.

4.Hardware protection

Electrostatic discharge immunity: air discharge ± 15KV, contact discharge ± 8KV;

Electrical fast transient burst: interference frequency is 5KHz or 100KHz, pulse group time 300 (1 ± 20%) ms;

Lightning (surge) immunity: 2KV capacitive coupling and gas discharge tube coupling, 1 time/min;

Conducted harassment immunity: 3V capacitive coupling and gas discharge tube coupling, test frequency is from 150KHz to 80MHz.

5.Software protection

The operating system is usually stored in Flash. Static interference of the Flash and unexpected power-off are prone to make the operating system lost and the file system damaged. Except the normal operation system, design a backup system in the normal flash storage area is necessary, thus when something wrong goes about the Flash, the backup system starts automatically to ensure that the product is still able to work stable.

Now you must understand why it is not allowed to touch the printed circuit board by hand, right?

Dangers of Not Recycling PCBs

That PCB boards are found in all types of electronics is clear, but what’s perhaps not so clear is why there is so much emphasis on recycling them. As mentioned before, PCBs are a treasure of valuable materials that can be recovered and reused through the process of electronic waste recycling.

Actually, the dangers of not recycling e-waste or just sending to landfills always ignored by people, but the dangers are severe than you can imagine. Electronics contain plenty of hazardous substances, so if we just sending them to landfills, they easily get released into the environment and leak into the groundwater which will potentially pollute the water we drink and pose a serious threat to human health.

Electronics recycling is the most effective way to not just prevent pollution and possible ill-health, but also conserve natural resources. When we recycle valuable materials from electronics, we eliminate the need for extracting these elements from the nature. While resource conservation is a direct advantage of recycling electronic waste, cost and energy savings are the indirect benefits.

Learn more about how to tackle e-waste like PCBs, please visit www.epcb.com