Response
from the ESD Journal Expert
In
response to the question ESD Journal reader Lorrie posed regarding static sensitive
boards carried on type II or II bags Steve Fowler, Fowler Associates, resident
expert for the ESD Journal, writes:
The
question does not have an exact answer.
It depends on
1. The sensitivity of the components on the board
2. The
layout of the board (how are fields coupled to it)
3. Is the person carrying
the board wearing ESD shoes or heel grounders and walking on protected or unprotected
floors?
What Happens?
1.If there no high static fields present, nothing happens.
2. If there are high static fields present, the board will absorb the discharge
of any touching or setting down during its presence in the field. If the board
is charged, it will discharge more abruptly to a metal-out Type III bag than a
metal-in Type III bag. The Type II bag will always discharge the board more safely
than a metalized bag. However a metallized bag in which the board is carried will
always protect it more than a Type II bag if the static field is in motion.
Like I said, this is a very complex issue.
The
best answer is:
"why carry a board on a bag?"
