In a previous blog post about our third grade enrichment study of static electricity, I shared a list of questions and ideas that students generated based on their experimentation (See the class description and info here: http://enrichmentatres.blogspot.com/2015/01/static-electricity-hair-raising.html ). This week I received a response from an ESD engineer at IBM. It is so exciting to share how student's thinking and learning connects to the real world and this interaction will be a great example of how applying your learning is important! I feel so grateful to live in a community where professionals are willing to spend time supporting student inquiry.
Here is the IBM engineer's response to our inquiry about static electricity:
Hello Mrs. Rankin's third grade class,
Thank you for your note and the
information you have come up with, I'm personally very passionate about
this topic of Electrostatic Discharge (ESD) since I've done lots of
research, published lots of papers and lead a team at IBM on this topic.
I'll comment on your list below which I think is a very good list,
nice job class!!!
1) Wear special clothes
**Do not wear fleece (maybe leather? We are not sure what material would work best)
---> IBM: We have all areas that will come in direct contact with computer chips
once they are packaged handle them with wrist straps on, dissipative
coats, dissipative shoes, we even have floors which are dissipative
including making sure the wax used to clean the floors is dissipative.
We don't do anything special with hats or gloves specifically for ESD
because we have wrist straps and/or floor shoes which dissipate any
charge out of the body and the jackets help minimize the body getting
charged up in the first place.
*Make your chips bigger so the wires will not be as small
Ideally this is an excellent idea but unfortunately with computer
chips trying to pack more stuff inside them and the number of pins a
computer chip has increasing the wires are actually shrinking over time.
Thus the way we have to deal with this is instead of using one wiring
level we have to use many wiring levels connected on top of each other
to get the volume of metal in the wires we need.
*Cover the wires on your chips with something that keeps the static away from the wires
The static is typically stored in either a person, machine or inside
the computer chip itself. So cover the wires with something that keeps
the static away from wires won't typically help. However, you have a
good idea in general, if you cover the wires with materials that help
keep them cooler rather than having them heat up so much (thermally
dissipative material) then that will help. Great idea!!!
*Have back up wires on your chips
IBM: We essentially have parallel
wires, not backup ones so the idea is a good one. Thus the way we have
to deal with this is instead of using one wiring level we have to use
many wiring levels connected on top of each other to get the volume of
metal in the wires we need.
*Do not have carpets in your lab (We think tile or wood might be better)
--> IBM: Typically we use tile floors
that are dissipative. However, we do have part of our lab with carpet
but it is very special ESD carpet that has wires running through it that
get connected to earth ground to dissipate the charge.
*Do not touch chips, but use tweezers or robots
--> IBM: Great idea and yes we make
anyone even using tweezers to wear dissipative jacket and have wrist
strap on and have dissipative shoes. Robots and tweezers typically have
dissipative materials on the "fingers" that grab the computer chips so
the computer chips don't get charged up.
*Only make chips when it is the right weather (we get lots more static shocks in the winter)
--> IBM: Yes, ESD is very sensitive to
humidity and when relative humidity in the winter is very low we get
more static charge which we have to find ways to deal with. Ideally we
would only make things in the summer but unfortunately for our business
we have to operate year round so we find ways to deal with extra static
electricity in the winter which is by using things like ionizers which
"balance or uncharge" objects and we will use very good wrist straps,
dissipative jackets and dissipative footwear and floors.
*Put your chips in special packages
--> IBM: When the chips are made they are
put in antistatic bags and trays to ensure they don't get charged up
during transportation. So yes we do this all the time, excellent
thought by the class!!!
We are wondering if you do any of these things already? We were also
wondering if there were things we missed that you doing your lab ?
--> IBM: Great set of questions, in
addition to controlling static charge as listed in the above answers.
We also do ESD testing with ESD testers to see how robust the chips we
build are against ESD events. ESD events are mainly (3) kinds, ones
which come from humans known has "Human Body Model (HBM) discharge" ,
ones which come from machines "Machine Model (MM) discharge" and ones
which come from the chip itself being triboelectrically charges (aka
frictional/rubbing two materials together charge) know as charge device