ESD Turnover cart wheel system resistance test
The resistance test of the wheel system facing the material turnover cart in the EPA area is unqualified, but it is also proposed that the wheels need to be conductive wheels when they are purchased. However, after the actual arrival of the test, the resistance between the wheels on each layer is too high, then What caused this?
Now we will analyze this problem and rule out the specific cause:
There are generally two reasons for the failure of the resistance test of each deck and wheel system of the turnover cart: one is that the wheels are made of non-static material; the other is that each deck of the turnover cart is disconnected and non-conducting.
First of all, let's take a look at the first reason: the test wheel material and the resistance between the column and the wheel meet the ESD control requirements, and eliminate this problem;
Secondly, the reason why the resistance test of the wheel system on each floor of the turnover cart is high: the fasteners of each layer of the turnover cart are insulated plastic parts, and the column of the turnover cart is disconnected from the layer.
Temporary countermeasures: Use multiple strands of wire and wire to connect each layer of the turnover car platform with the pillars, so that each layer is connected to the metal parts above the wheels;
Long-term countermeasures: In order to fix each layer of the grid table, the turnover cart uses metal fasteners to replace the plastic fasteners of each column on each layer to avoid abnormal conditions of non-conduction.
Finally, after improving the plastic fasteners on each deck of the turnover cart, the measured system resistance of each deck of the turnover cart facing the wheel is all qualified, which meets the requirements of electrostatic protection control: <1×109 ohms.