Is it possible that the metal shell of the interface is directly connected to GND, causing ESD?

Nubility

Is it possible that the metal shell of the interface is directly connected to GND, causing ESD? [Copy link]

 

Recently, a colleague who was a big jerk is going to run away. It turns out that he was responsible for testing the board designed by the stupid leader. After more than a year of testing, there are still various problems and it has never been able to go into mass production (mainly due to the leader). Then the stupid leader handed over most of the colleague's work to me.

My colleague told me that the most serious problem is that the metal interface of the board will freeze due to static electricity. I took a look at the PCB file and found that the metal shells of all interfaces were directly connected to GND, and there was no special treatment for GND on the PCB.

I heard from some old masters that the metal shells of these interfaces should not be directly connected to GND at all. The safest way is to connect the chassis ground and GND with a traditional 1M resistor in parallel with a 10nF capacitor. It is also very simple to connect GND directly, but there is no chance of disconnection when the PCB is directly connected to GND.

wangerxian

I can only redesign the board.

qwqwqw2088

The metal shell of the interface is directly connected to GND, causing ESD

It is possible.

qwqwqw2088

Because it may form an unnecessary current path within the system

However, if ESD protection components such as TVS diodes, ESD diodes, etc. are not properly designed in the design,

Even if the case is not directly connected, it is still very vulnerable to electrostatic discharge testing.

Pathan

There are only two corresponding methods for all interference: blocking and diverting:

1. Block: TVS, 1M resistor, RC, etc.

2. Introduction: There is a closer route from the metal baffle to the ground

chineseboyzxy

The audio, video, and radio frequency sockets are all grounded. How can they work without grounding?

Nubility

chineseboyzxy posted on 2024-8-30 08:51 Audio, video, radio frequency, sockets are all grounded. How can they work without grounding?

Is the case also connected directly to GND

beyond_笑谈

The shell can be connected to GND, 100% sure. ESD protection should be done at the interface

Nubility

beyond_笑谈Published on 2024-8-30 10:48 The shell can be connected to GND, 100% sure. ESD protection should be done at the interface

The chip is relatively close to the interface, and the metal shell of the interface is directly connected to the GND copper foil of all layers.

Dxiaobai

Nubility posted on 2024-8-30 11:17 The chip is relatively close to the interface, and the metal shell of the interface is directly connected to the GND copper foil of all layers

In theory, the shell should be connected to the ground, but there is no problem with connecting it to the signal ground. The RF SMT is connected to the signal ground, and some RJ45s are also connected to the signal ground. The main reason for static electricity to cause a crash should still be a protection problem.

Nubility

Dxiaobai posted on 2024-8-30 13:47 In theory, the shell should be connected to the ground, but there is no problem with connecting it to the signal ground. The RF SMT is connected to the signal ground, and some RJ45s are also connected to the signal ground. Static electricity will...

The radio frequency should be fine. Generally, if the radio frequency antenna seat is not exposed to the outside, there will be no static electricity.

beyond_笑谈

Nubility posted on 2024-8-30 11:17 The chip is relatively close to the interface, and the metal shell of the interface is directly connected to the GND copper foil of all layers

The interface should be protected by ESD (such as TVS, etc.) protection components. In the previous explosion-proof controller, all ground signals were connected together and connected to the shell. The ESD test passed

秦天qintian0303

It also depends on the PCB design. The ground must be complete, and the energy must be able to dissipate.

Nubility

Qintianqintian0303 posted on 2024-9-1 19:06 It also depends on the PCB design, the ground must be complete, and the energy must be able to dissipate

All the metal pins on the shell are connected to the GND copper foil in a 10-shaped way, and the metal pins are very close to the chip and far away from the power inlet. So I currently think that the charge has affected the chip before it flows into the ground.

Nubility

beyond_笑谈Published on 2024-8-30 15:50 The interface should be protected by ESD (such as TVS, etc.) protection components. In the previous explosion-proof controller, all ground signals were connected together and connected to the shell...

The ground is connected together, but the specific connection method should be very particular. Even if it is directly connected on the circuit, the connection method can still be changed on the actual PCB, such as digging grooves in the copper foil.

ruyi1pei2003

This is indeed the case.

beyond_笑谈

Nubility posted on 2024-9-1 19:16 The ground is connected together, but the specific connection method should be very particular. Even if it is directly connected on the circuit, the connection method can still be changed on the actual PCB, and the copper foil can be...

GND can be cut when connected to large-capacity capacitors. Simply put, the GND of TVS and capacitors should be connected first.