How to ground ESD to rechargeble lithium ion battery

[allenlsk]

Hi,

WE are doing a portable device which having a metal part that can be direct contact by user. this metal part is extend all the way 30mm from the outer casing to the inner part of the device. The inner portion of the metal is close to some of the electronic component. So, we design a grounding cable to ground the metal part direct to the ground pin of the Chargeble Lithium ion battery.

But, the 6Kv ESD still make the meter shutdown / hang. Is it because of the battery that is not able to ground the ESD? we say that is because when we direct shotting the ESD to the Battery Ground, the ESD gun do not show discharged.( like what is shown the time i shot to the ground table )

Please help

Thanks

 

[rikie_rizza]

So the portable device is a meter?

You cannot ground ESD to a battery...you must ground ESD to...ground!
But, your system with metal contact can still be build if your system is ESD protected. Use ESD clamping diode or other ESD protection device (IC) between the metal plate and the electronic system.

Recheck your system for false design.

 

[allenlsk]

Thanks for the reply,

When you say must ground to ground, do you mean the ground plane in the PCBA or the external ground?

please advice

 

[ilikebbs]

why do you ground the metal part direct to the ground pin of the Chargeble Lithium ion battery?
It will be better that gound your ESD to ground plane far way any component.

 

[allenlsk]

Hi, all,

just find out that we are grounding to the Battery(+) terminal instead of ground terminal.

anyone can advice, will this be better / worst ?

Thanks

 

[e_eja]

do not use metal part as a ground but use C or RC between ground chasis and metal part

 

[rikie_rizza]

It will worsen your system because discharge from human model ESD may fluctuate DC voltage of the battery. Ground it to its chase...do you know why in all portable devices, there is an aluminum foil surrounding its chase? I think its what they call chasing ground.

 

[synq]

you guys miss the whole point, no need to discharge the esd to ground in portable devices, however you can still provide massive esd dissipation plane, other genral method is to provide zig zag pcb traces to the edge of pcb to negative ground potential, refer esd protection devices as well, other simple job is to provide clearance to contactable surface more than 20cm to handle nearly 20kv esd discharge, if space is a constrain still try vishay electronics for esd protection diodes something like VESD05A1B-02Z