ESD problems
Coop123
Posts: 4
in Propeller 1
Has anyone had issues with the Propeller and ESD. And what you do to prevent this from killing the chip?
Comments
Cold dry air in winter coupled with central heating is a recipe for very large amounts of static electricity
making damage much more likely. There's nothing special about the Prop, all CMOS chips are vulnerable.
Use a conductive wrist strap and bench (wood is fine). Do not wear synthetics, cotton/wool only is
really going to help. Consider ways to humidify the room.
Never ever touch a chip by its legs until you've grounded yourself to the anti-static packaging it comes
in - then everything is at the same potential.
When the air is very dry potentials can rise to many kV on any insulating surface very easily indeed.
Perhaps you can post a pic of your board and the schematic?
Are you using the DIP or QFP version? Are all power and grounds connected and short? Do you have proper bypass caps?
Have you tested to see if the dead chips work in rcfast mode (ie a dead PLL)?
Protection diodes can only do so much, and are typically designed for a model of a kV or 2 through a
modest resistance. With dry conditions the voltages typically seen are 10's of kV - just peeling
sticky tape from a roll can actually generate x-rays due to the massive tribo-electric voltages. No MOS chip
can handle that.
The best practice is to always handle components as if they have no protection, so always in anti-static
conducive bags/foam.
As an aside, when I was working in the defense industry we had to certify our chips / components and manufacturing procedures were up to standards, extremely high standards, including daily / hourly ESD checks on every piece of equipment and every manufacturing procedure. I would write you up if you had the wrong type of clothing, no wrist / leg straps, not using proper assembly procedures and soldering techniques. The biggest problem was extra "stuff" on the assembly tables: lamps, magnifiers, cleaning rags, smoke removal fans, coffee and cold drink cups, and personal radios and cellphones, believe it or not!
While we did not use Prop products, we used Atmel chips, the engineers took these chips and used them as coin change and key FOBs for about six months. If the IC pins did not fall off the IC's were put into PCBs - they all worked LOL
+1
I have worked in (and enforced) well-controlled environments in the past, but my own hobby work bears no resemblance to best practices.
It would be good to learn how/why you suspect these failures can be attributed to ESD. Is it possible that something else is amiss?
+1
I've abused the heck out of the P1 and haven't killed one from ESD yet. I've killed a couple PLLs, fried pins and completely released the magic smoke beyond identification.
Without seeing anything from your application, it's either a psu issue or a input issue. All prop power pins need to be connected as well as properly bypassed. A well regulated supply, fed into a properly bypassed chip is where most people go wrong.
The other thing that kills props is voltages > 3.6v. Okay, so there's some wiggle room here but this seems to be the SAFE limit for a few reasons. Anything over this will raise the supply voltage, and this is the way I've fried more chips than I want to admit. Had a few 12v signals get to the propeller pins. bye bye propeller.
A photo of your bench setup would tell us a lot and help us advise you. It COULD be static, but I doubt it.. Unless you're petting your cat while prototyping, you're probably safe there.
-Phil
Btw my desk is 20 years old. Have to be careful.
What evidence do you have that this is an ESD problem and why would you jump to that conclusion? For sure there is a problem since you have failures but I've never seen any ESD failures with Props so it seems unlikely. As noted by others, your problems are probably due to another cause however you need to provide some photos and schematics etc if you would like some informed feedback.