Can the anti-static bubble film be placed on the circuit board
People in our company like to put pink anti-static foam (a thin sheet about 30*30 in roll) under the PC board. They use the foam because it helps prevent the board from sliding around on the anti-static workbench, and they think it will extend the life of the workbench surface. However, I think this is bad practice because foam is an insulator. But on the other hand, I have found that objects placed on the foam (on the workstation surface) can slowly dissipate their charge, based on my measurements with an electrostatic voltage tester. So, is this approach acceptable?
my reply:
Pink foam is generally acceptable if it is dissipative and electrically grounded. But it really depends on the ESD sensitivity of the product you want to protect.
To measure the resistance to ground (RTG) of antistatic foam, you can use an AAC-TR-800 megohmmeter. Try measuring at 10V and 100V. For safety reasons, the resistance should be controlled at 105~109 ohms. You say you measured with an electrostatic field tester, which is ok, but not entirely sure that the foam is safe. The more important criterion is that the working surface should discharge the static charge within 100 milliseconds. If it takes a few seconds to clear the static, that is too long and could put your ESD sensitive devices at risk of an ESD event. Of course, other materials are also available to place WIP (work in process) on the bench for static protection and anti-slip properties at the same time. For example, anti-static table mats are an excellent choice in this regard.
Some questions you need to be aware of during the control process: What is the electrostatic sensitivity of the part I am trying to achieve ESD protection? Is the foam conductivity at a safe dissipative level? Can the foam release its charge in about 100 milliseconds? Has the foam been grounded? Has the operator worn the antistatic wrist strap correctly? If all of these questions are yes, then you have taken some effective ESD precautions.