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View Full Version : "The Shocking Truth", Apple's internal video about electrostatic discharge damage



Floppies_only
April 21st, 2010, 08:13 PM
Gang,

The other night I dug out my pirated DVD of some of Apple's internal videos and re-watched the one that explains how semiconductors are damaged by static electricity (sometimes without anything coming into contact with the board or component). It's on Youtube:

(Parts 1 through 4)

http://www.youtube.com/watch?v=4WHbcd4NGJQ

http://www.youtube.com/watch?v=AT2bhYLgFiM

http://www.youtube.com/watch?v=8DXjx2k1kYk

http://www.youtube.com/watch?v=ACstwfL4x84

The video got me to wondering. Actually, I have three cards that have been sitting next to my TV for years, waiting to be installed. The video said that they should be in a bag or in a computer to be protected, so I'm probably screwed anyway. But I was just wondering if anybody knew if they could be damaged by the field that the TV generates when it first turns on. Anybody?

Thanks,
Sean

lutiana
April 21st, 2010, 10:25 PM
Alright, I learned some things from this video. Very well worth watching.

Dwight Elvey
April 22nd, 2010, 07:08 AM
Hi
Yes, putting it in front or close to a tube type color TV can
damage by static electricity.
One thing he said was a little incorrect. Being on a board
does offer some protection but can increase the chance of
being damaged. Three factors:
1. The capacitance of the line or trace: The amount of charge,
such as from coming near a non-conducting surface with a charge
on it is reduced by a larger trace.
2. Alternate path to ground: On a board most sensitive inputs
are also connected to output drives. These are usually a diode
voltage away from the ground and power rails.
3. Adjacent trace sheilding: A static field gets didstributed across
many traces.
The transistors he was blowing up were unprotected gate VFETs.
They are quite easily damaged. At a place where I worked, over
time, the soldering irons had lost their ground pins ( I suspect
plugging then into cheap extention cords ). They used these to
solder in a bunch of VFETs. Almost 80% were blown!
The other part that you'll find is very sensitive to static is the
CMOS analog gates. Some of the numbers I recall are 4051 and 4052.
These need extra careful handling.
When I was at Intel ( years ago ), a work was carrying a EPROM
at arms length, pins facing away and holding the case.
I asked if she was trying to see if she could destroy the chip.
She said that she'd just seen a movie on how static could damage
parts and was being especially careful to not damage that part.
I was shocked. I explained to her( although I doubt it soaked in )
that the way she was carrying the part was just about as bad
as could possibly be done.
If as a last resort, you closed hand is a Faraday shield. I told
her that if she couldn't find a proper protective surface to put
it in or on, she should put it in her closed hand.
She didn't get it. What she got from the movie was "Don't touch
the leads".
Dwight

Floppies_only
April 22nd, 2010, 05:24 PM
Gang,

The other night I dug out my pirated DVD of some of Apple's internal videos ... It's on Youtube:

(Parts 1 through 4)

Somebody asked me if I posted pirated videos to YouTube. I didn't. I just posted the links to them here.

Sean

Tetrium
April 22nd, 2010, 08:07 PM
Nice vid, learned a couple new things. I had no idea that holes in a antistatic bag made the bag useless.

lutiana
April 22nd, 2010, 11:34 PM
Somebody asked me if I posted pirated videos to YouTube. I didn't. I just posted the links to them here.

Sean

Yeah, that was me, it just sounded kind of dangerous. But I realized afterwards that it was just a link to what someone else posted. Thanks for it, as I said I learned a lot from it actually.

Raven
April 23rd, 2010, 07:17 AM
Interesting - this has convinced me to use my IBM wriststrap kit that I recently got on a regular basis.

Edit: One thing I don't get though - the rubber mat is supposed to be grounded to the wall's "earth ground", right? How do you do that? Mine has two snaps for hooking it up to your wriststrap, and then the wriststrap has an alligator clip for clipping to the chassis or some such. As far as I can tell that gets you no *proper* ground....?

hargle
April 23rd, 2010, 08:57 AM
A true anti-static rubber mat should be laced with a wire mesh on the inside of it, and that all connects to a wire, and then you ground that onto an outlet. that's what we used back in the days of Zeos anyway.

barythrin
April 23rd, 2010, 10:03 AM
Dell (I temporary worked there in the assembly line for a few months ..like..10 years ago) had their folks stand on those mats with an ESD band on. It was one of the very few things I was impressed with there. It would actually sound a loud beep if you weren't grounded to the mat or stepped off of it. It was a good thing as most of the kids working back there don't know anything about computer or ESD, all the parts are made to snap into place with plastic to ease the use for non-technical folks.

Raven
April 23rd, 2010, 10:31 AM
I guess mine is just designed for chassis-grounding then.

hargle
April 23rd, 2010, 11:30 AM
>Mine has two snaps for hooking it up to your wriststrap, and then the wriststrap has an alligator clip for clipping to the chassis or some such. As far as I can tell that gets you no *proper* ground....?

I suspect that one snap is for your wrist strap, the other snap is for the wire that leads to the actual ground. Just laying the chassis on the mat (provided there's metal touching it) should be enough to ground it.

Back in the ole old days, we used to even plug machines into the wall (but left powered off) and then you knew the chassis was always grounded through the power supply, and as long as you touched it before picking up components, you were reasonably well grounded. It's a bit tougher now with ATX type power supplies and instant on. Dropping a screw or something onto a motherboard even though it's "off" can often mean a shower of sparks!

Tetrium
April 23rd, 2010, 11:46 AM
I only use a wrist strap with the alligator clip and attach it to the case I'm currently working on. I usually wear something with short sleeves anyway and have plenty metal objects around I can touch.
So far I haven't zapped anything yet...atleast I hope so heh.
I try to never touch any of the chips or leads and handle everything by the edge, the slots or a part of the pcb that's 'blank'. Also I never work on my conputers when it's (almost) freezing or very dry, my dry skin turns into a walking deathbomb for any microchips!!

Floppies_only
April 23rd, 2010, 02:47 PM
Edit: One thing I don't get though - the rubber mat is supposed to be grounded to the wall's "earth ground", right? How do you do that? Mine has two snaps for hooking it up to your wriststrap, and then the wriststrap has an alligator clip for clipping to the chassis or some such. As far as I can tell that gets you no *proper* ground....?

What I would do is connect the second wire to the snap on the mat and then unscrew the screw that holds the plate on an electrical outlet enough to clip the alligator clip onto it. I would also have the machine to be worked on plugged in and turned off. That way you are attached to the mat, the mat is attached to the building's ground, and the machine's chassis and ground circuits are attached to the building's ground.

Oh, if there was paint on the screw I'd file it off first.

Sean

NeXT
April 23rd, 2010, 03:28 PM
I have been doing electronics work and soldering on my (carpet) floor for years now.

Raven
April 23rd, 2010, 04:54 PM
What I would do is connect the second wire to the snap on the mat and then unscrew the screw that holds the plate on an electrical outlet enough to clip the alligator clip onto it. I would also have the machine to be worked on plugged in and turned off. That way you are attached to the mat, the mat is attached to the building's ground, and the machine's chassis and ground circuits are attached to the building's ground.

Oh, if there was paint on the screw I'd file it off first.

Sean

I don't have electrical outlets, unfortunately. I live in a not-yet-finished basement, and my stuff all runs off of extension cords from upstairs, and one socket down here that's way across the room. I also don't have a second wire - just the first one. It's set up like this:

()------------------------------------------------{ o }-------------------------------------------------<
Wrist strap, then snap, then clip, respectively.

I imagine it would work if I clipped to a proper ground though as you say.

This morning I did some stuff and clipped the clip to the metal basement window, which is embedded in concrete at ground-level - is that a ground? >.O

basman74
April 23rd, 2010, 11:25 PM
This morning I did some stuff and clipped the clip to the metal basement window, which is embedded in concrete at ground-level - is that a ground? >.O

Generally speaking, if one needed to connect to ground/earth and doesn't have access to an electrical outlet, one could try either:

1.) Connect to a METAL WATER PIPE (but DO NOT CONNECT IT TO A GAS PIPE - STAY AWAY FROM THOSE!), or
2.) After checking that an area of ground soil has NO GAS/WATER/ELECTRICAL PIPES UNDERNEATH, drive a 40cm metal stake into the GROUND SOIL and connect to that.

digger
April 24th, 2010, 05:10 AM
Even though most of us know about the dangers that static electricity imposes to electronic components, I still learned quite a bit from it. It is a very useful video indeed, and cool to see Steve Wozniak in his younger years. It's good to see that his playful enthusiasm hasn't changed compared to then. :) Thanks for pointing this one out!

basman74
April 24th, 2010, 06:52 AM
Just watched the videos - very interesting and informative! Thanks for sharing these!

Note to self: must not use old toothbrushes to clean prototype boards :lol:

Dwight Elvey
April 24th, 2010, 07:35 AM
I have been doing electronics work and soldering on my (carpet) floor for years now.

Hi
Do that with an ungrounded soldering iron on an unprotected
VFET and you'd blow it out.
Most components are relatively forgiving for small discharges.
Many are tested to take a human body sized capacitor ( I forget
the amount ) and 1Kv discharge.
Dwight

Dwight Elvey
April 24th, 2010, 07:47 AM
I only use a wrist strap with the alligator clip and attach it to the case I'm currently working on. I usually wear something with short sleeves anyway and have plenty metal objects around I can touch.
So far I haven't zapped anything yet...atleast I hope so heh.
I try to never touch any of the chips or leads and handle everything by the edge, the slots or a part of the pcb that's 'blank'. Also I never work on my conputers when it's (almost) freezing or very dry, my dry skin turns into a walking deathbomb for any microchips!!

Hi
Holding boards only by the edges is one of the easiest ways to damage them.
I've heard this several times and every time I hear it I cring a little.
A lightning rod is a pointy stick. Every time you reach your arm out
with the board floating ( well insulated ), you can induce damaging charges
on it, the next time you put it down.
When moving a board, you should alway have it wrapped in foil or
anti-static cover.
When moving it about on at a grounded station, you should always
have it connected to something grounded. Your hand to a strap works
here.
If you have a board in your hand, you should always have body contact
with a power or ground trace. You should always make contact with
the surface you are going to place it on first with your other hand.
You should never carry the board at arms length, away from your
body. You should never let the board electrically float relative to
your body.
Dwight

per
April 24th, 2010, 09:15 AM
I've just started to learn about electrophysics in school, so this thread came in with about the right timing.

Here in Norway we got quite humid air, and I have found that it reduces the risk of building up charge. However, I didn't know some components were that sensitive. In fact, I blew a transistor on a "MHz display" (from a pentium machine) not too long ago problably because of something like this. Perhaps this can be related to the EEPROM failures some of the XTIDE owners experiences?

I have not experienced zapping any chips before, but one factor may be that I'm usually working with my early IBM PC's, and old TTL chips seems to be more tolerant.

Floppies_only
April 24th, 2010, 02:57 PM
You should never let the board electrically float relative to
your body.
Dwight

Because of inductive coupling to a non-conductive body near the board.

Sean

Raven
April 24th, 2010, 06:50 PM
Ok I don't want to sound like an idiot, but what did he mean by "electrically float"? Did he just mean without contact with a conductor or ground?

k2x4b524[
April 24th, 2010, 10:09 PM
thank god i live in washington state.. humid air... all my boards are out in the open. i watched this too, amazing stuff

TomFCS
April 25th, 2010, 05:19 AM
So, if open air circulation itself, can create enough static to be harmful, was constructing this parts storage cabinet (http://www.welook4things.com/04-25-10/album/slides/parts_cabinet_1050.html) a bad idea? The goal here was to reduce humidity and avoid corrosion. Unfortunately, the only area I have available to use for parts storage can be extremely humid in the summer months.

Raven
April 25th, 2010, 08:16 AM
I keep my parts in a tower of plastic drawers 9 high, in which the cards lay on top of one another unprotected and I've not had any immediate problems from this.. the video scared me, however. :/

I used to keep them alllll together in a pile.

We do keep our house at a neutral humidity though... perhaps that helps?

Floppies_only
April 25th, 2010, 05:19 PM
Ok I don't want to sound like an idiot, but what did he mean by "electrically float"? Did he just mean without contact with a conductor or ground?

That's what it sounds like. I got this from Wikipedia, but that's no guarantee that it supports the "common sense" meaning of the phrase:

"A system where the system ground is not actually connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground."

Sean

saundby
April 26th, 2010, 01:16 AM
Electrically floating means it's not tied to anything electrically--there's an insulator between it and what's around it, whether air or bare fibreglass at the edges of the board.

So, here's what's happening in that situation. The board is generally at some fairly fixed level of potential. The novice carefully picks it up by the edges, to avoid a shock to the board. The are at a different potential to the board already, and haven't equalized themselves with the board. They then carefully hold the board out from their body and begin moving. Friction between the floor and their feet, and the air and their body, builds a static charge. Because their hand is stuck out from their body, the charge will be greatest between there and their feet across their body. The hand that's holding the board will be at some high level of potential, their feet the opposite, like a cap.

If they then discharge to the board, eitheer by now touching a conductive element or because the potential difference between them and the board is enough to bridge the gap of the insulating material, it'll be about as big a charge as they can get into the board. Say goodbye to FETs, A-series CMOS, and a lot of NMOS and PMOS.

If, instead, they had started out by first discharging themselves in the board's area to get close to its potential and discharge any big charges they may have built up getting there, brush their hand down themselves firmly to get rid of local charges on the hand, then firmly grasped the board by a ground trace, then spread their grip to an entire edge connector before lifting it, tucking it under their arm against their body and walking with it that way, the chances of a deadly charge are far less, and won't be made worse as they move.

Oh, and since the most common black dyes are carbon based, black clothes are good for more than looking cool. They'll keep the charges equalized across you like a resistive strap. Just keep your ankle strap on...and leave the circuits alone on cold windy days. ;)

tezza
April 26th, 2010, 03:29 AM
Thanks for posting a link to those videos. Very educational. I can now understand why my PS/2 board stopped working when I washed it. It was probably the way I handled the board.

I will be a lot more careful in the future.

Tez

Dwight Elvey
April 26th, 2010, 06:42 AM
Ok I don't want to sound like an idiot, but what did he mean by "electrically float"? Did he just mean without contact with a conductor or ground?

Hi
Yes, not connected.
The safe process of handling a board is:
1 . While holding a common grounded surface ( something electrically connected to the board )
2. Pick up the board, making sure that you are electrically connected to traces on the board
( best is power and ground )
3. Hold the board close to your body, not at arms length ( charges like pointy things like lightning rods
and out stretched arms ).
4. Put your other hand on the electrical surface of the destination of the board
5. While still in contact with the surface, put the board there.

A floating board is subject to induced charges but a board that is in contact with
a large body ( yours ) can't take on a charge relative to that body.
By touching the final surface, you drain off your bodies charge safely away from the
board.
If you want to make some good static cloths the where, take some cotton cloths
and don't put it through the rinse. The detergent will make it slightly conductive.
Dwight

andy
April 26th, 2010, 08:18 AM
I learned a few things from that, such as the pink anti static bags not shielding things from externally generated ESD.

I'm more amazed at how often poor handling doesn't result in failure. I often see boards and chips on ebay that are photographed while sitting on carpet. Even when I ask them to use an anti-static bag, they often ship it in peanuts, or regular bubble wrap.

modem7
April 27th, 2010, 04:08 AM
Practice safe SEX (Static Electricity eXit).

Note that anti-static grounding leads have 1 MegaOhm or so of resistance built into them.
That's done for safety purposes. Not safety of the equipment, but safety of you.

Still, if I'm working on a live power supply or a live VDU, I won't wear an anti-static wrist strap (to protect what chips there are).
In that scenario, there is no way that I want to be grounded, or connected to a return path, even if there is 1 MegaOhm in the lead.

saundby
April 29th, 2010, 02:20 AM
Yeah, 25kV isn't something you want a path to.

Once I was checking out a color monitor power supply. My benchtop housekeeping was a little lax that day. I'd left a roll of solder midships with the end of the solder pulled out and trailing over the edge of the bench. I powered up the supply, saw a good 25kV on it open-circuit, then reached over and hit the switch on my load box to test its regulation under load. As I did so, the anode cap popped off the fixture. The stiffness of the anode cable pulled it right into the roll of solder.

Guess where the end of the solder was hanging...

It hit me on the left thigh, I jumped left. Then it hit the right side. I jumped again. After 2 or 3 iterations I collected myself enough to switch off my low voltage DC supply.

I caught my breath about half an hour later, and ever since my "situational awareness" of my benchtop has been significantly enhanced.

Floppies_only
April 30th, 2010, 12:40 AM
I learned a few things from that, such as the pink anti static bags not shielding things from externally generated ESD.

I'm more amazed at how often poor handling doesn't result in failure. I often see boards and chips on ebay that are photographed while sitting on carpet. Even when I ask them to use an anti-static bag, they often ship it in peanuts, or regular bubble wrap.

I also read that the silver bags are the ones we want. I can't remember who in this thread keeps telling to walk with smelly boards under our armpits, but I think that's not good enough. My understanding is that the proper way to transport computer electronics with semiconductors is to remove them from a grounded computer (plugged in, turned off) while wearing a ground strap, put them into a protective bag, move or store them, then reverse the process as needed. If you're replacing bad chips, the board also needs to be on a grounded work station mat.

On a side note, I had the happy discovery that my EGA cards were actually stored away from the TV and in bags. Although I've got some memory boards that have been sitting next to the TV for a long time. It will be interesting to see if they work.

Sean