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ESD and EMC sensitivity of IC
This application note describes basics of the ESD and EMC sensitivity of
http://www.nxp.com/documents/applicatio ... N10853.pdf
Integrated circuits are sensitive to electrostatic discharge (a sudden and short-time flow of
currents) and electromagnetic fields (at which they can be source or victim of both of it).
This application note shall be understood as an introductive basic description of
• what electrostatic discharge is
• how sensitive devices can be protected against electrostatic discharges
• what electromagnetic compatibility means
• and how electromagnetic sensitivity can be tested.
But by no means, this application note does not substitute any of the corresponding
engineering standards and standard operation procedures.
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Here are a couple of old posts of mine on 6502.org that might be helpful.
I store my ICs in old 2oz tobbaco tins. They stack neatly, are labeled for ease of finding chips and, being metal, I don't need to worry about static precautions since an electrostatic field cannot penetrate a conductive enclosure.
Be careful. In the mid-1980's I worked at a company that made VHF and UHF power transistors. I was initially hired to help get the new CMOS line into production which they had acquired from another company. The managers thought they were going to be really tough on the matter of handling to avoid damage from static and minimize losses, and were real sticklers about everyone using the anti-static lab coats, anti-static mats or the work benches, the wrist straps, finger cots, etc. etc.-- but there were still a lot of losses. Here's why.
These RF transistors looked like little satellites, with their wide, flat leads looking like solar panels coming out the sides, and they were carried from the die-attach stations, to the wire-bond stations, to capping, to DC test, to gross leak and fine leak, to RF test, and so on, going between buildings, all on aluminum trays, and usually some of the transistors' leads which stuck out the sides would touch the side of the tray. The workers would pick up the tray with no intention of touching the parts right then, so they weren't grounded, and they'd zap a few parts because their ESD would go through the tray and into the parts.
Fortunately the CMOS logic ICs
have protection diodes so they're a lot tougher than our RF transistors above. These diodes are extremely small though in order to hold the capacitance down; so if the ESD is bad enough, it can still blow them and destroy the part. If a PC board or IC sits on the bottom of your metal can and only signal pins and not ground or power-supply pins are touching the can and you reach for the can when you're well charged up on a dry day, the only way for the IC or PC board to come to the same static voltage level as the can is through a signal pin, and you can
still blow it.
All CMOS or even NMOS parts should only be handled at a an anti-static work station. It is not necessary to go with the anti-static flooring, the anti-static grounded lab coat, the finger cots, the air ionizer, or even a grounded wrist strap, but you should at least have:
- an antistatic mat like Jameco sells, and ground it to one of your pieces of equipment whose chassis is grounded through the third prong on the power plug. The resistance of the mat is low enough to slowly dissipate static, but way too high to let you feel any current going through your body even if you have one arm on the mat and the other comes directly in contact with the power mains. Letting a hot part fall out onto the mat will mar it (my own has many scars) so using a metal tray would be a good move. With everything at the same static potential, you don't have to worry about any ESD damaging parts.
- I also used the kind of wire used for DMM probes, and stripped a couple of inches of insulation off one end and wrapped it around the soldering iron heating element right near the handle, and put an alligator clip on the other end to clip to the anti-static mat.
- Before you touch anything static-sensitive when you sit down to your work, touch something grounded to discharge any static in your body, and then keep in contact with the mat as you work. This will be almost automatic if you normally wear short sleeves, since at least one bare forearm will normally be on the mat all the time.
I've never damaged anything with static doing things this way. If it's too unnatural to keep some part of your arm or hand in contact with the mat all the time, then maybe you should get the grounded wrist strap too. Altogether we're only talking about a $30 investment here. If you elect to go without it, it doesn't seem to matter how careful you are-- you'll pay the price once in awhile if you work with these parts enough.
I link to an NXP ap note on ESD precautions also in the data sheet for my 4Mx8 10ns 5V SRAM module
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Some good information there guys.
We teach ESD precautions as part of the electronics modules where I work. The soldering stations are all fitted out with ESD safe gear including conductive mats and wriststraps. The posters on the walls read 'STATIC ZAP MAKES SCRAP!'
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