Preventing ESD Damage

[Ed Deichler]

 

I recently purchased new synthesizer boards to upgrade the phase noise performance of my K3.  The instructions caution strongly against electrostatic discharge (ESD) damage and recommend using an anti-static mat plus a grounding strap.  Before I run out and buy the mat, I’m wondering is it safe to use rubber gloves to install the new boards.  Is it possible that a static buildup on my body coupled with the gloves will act as a capacitor when I come in contact with the boards?

Any club members who have experience with ESD work, please weigh in.  My homebrew work goes back to the discrete component days, hi.

73 de Ed

[Nashua Area Radio Society]

Hi Ed,

Unless the gloves are ESD compliant, you should always assume NO.

Most of the time when you see people using gloves, the intent is to protect the product from DNA contaminating a board or product.

Static electricity can be stored on any external surface. Gloves too.

Built into the grounding cable, the mat will have a 1Meg resistor in series to ground. The mat protects the product when it is being serviced.  The mat will not discharge the static you’ve generated sufficiently unless you are grounded by an actual wrist strap. That usually gets connected at the mat connector block.

Winter is the worst for ESD damage if the area is not humidity controlled to roughly or at least 40%. You can still generate a charge. You can also still create static electricity even in the summer, although less of a charge. Damage doesn’t  always show up right away. It can show up at any time down the road (latent damage?). Many times you will not see it until later.

I’m not an expert, but I work in a facility where static discharge prevention is very important.

Just for FYI reference (It’s just the Desco version, but you can, and should check out other sources!):

https://www.youtube.com/watch?v=7T5JgdhTi_s

https://www.youtube.com/watch?v=yZPPytNpkOM

https://www.youtube.com/watch?v=WWtyro49iZo

https://www.youtube.com/watch?v=T2kZHSDOOCQ

https://www.youtube.com/watch?v=op-fPgKnTg0

https://www.youtube.com/watch?v=nLS4SyLkq6c

John, N1ERF

 

 

[Nashua Area Radio Society]

Ed — Don’t use rubber gloves. Rubber, like most insulators, can itself hold a static charge of thousands of volts  (think of the plastic tv screen on older CRT’S).

Best for you and me at home is to use a wrist strap which has a ground cable attached. This will safely bleed off any charge on your hand and arm sufficiently to handle ESD sensitive items. The wrist strap cable will have enough resistance so that the charge is bled off slowly from whatever you come in contact with. Keep in mind, the board or component itself may have a charge considerable different than you so and you don’t want a discharge to occur from it to you either. The wrist strap will prevent any damaging discharges.

Lost of sources for wrist straps on line most under $10.00 and overnight delivery from Amazon.

Companies handling lots of ESD sensitive items of course have grounded work benches, often with ionizers, ground mats, esd clothes, shoes, carpets, etc…. Most consumers won’t be able to go that far.

Personally, I’ve handle lots of ESD sensitive boards and components (at home) with just the wrist strap and have had no problems.

Mike H.

K1VLB

[Nashua Area Radio Society]

I typically never worry about ESD as the parts I work with are easily replaced and cheap.

I do my work in my basement with the wood stove going and handle microcontrollers etc. without any wrist strap or anything.

I do however get a nice shock every time I get up and open the damper on the wood stove to add more wood!

Mike (AB1YK)

[Fred Kemmerer]

Hi Ed,

I like Mike’s approach of using a wrist strap that is grounded to your K3’s chassis. If you can find a large anti-static bag, set your radio on this and keep the board in the anti-static bag it will come in until you are ready to install. Put the two bags on top of each other and remove the board. Then install it. The use of the overlapping anti-static bags with the radio chassis ground by one of them will help to avoid static buildup and potential discharge through your board.

– Fred, AB1OC

[Nashua Area Radio Society]

I’m recently retired from the computer industry but we used conductive mats on the work-surface that were grounded to the green wire in the closest power outlet.  A wrist-strap was attached to my wrist with a conductive wire to the same ground point.  That pretty much eliminated any static problems but it may be a bit pricy for the average ham.  You could of course provide similar protection by cobbling together similar stuff from what you have hanging around.

I also put a conductive pad under my work chair.  I found that the fiberglass wheels on my chair would build up a charge when rolled across the nylon carpet in my office.  I fried a bunch of stuff even with a conductive wrist-strap until I figured out what was going on.

Increasing the humidity in the work-area is also a good precaution.  Something as simple as a tea-pot would work.  I have a whole-house humidifier in my home and don’t have a problem with static as a result.

Rich – KE1EV

[Nashua Area Radio Society]

Hi Ed,

ESD wrist straps and mats are used to bleed off static charges and bring all items to a common level.  Large current spikes will puncture and damage static sensitive electronic components.  The usual method to safely reduce the static charge and limit the discharge current spike will usually use a wrist strap with a cord containing an in-line resistance between 1 – 10 Meg Ohms attached to the common ground point.

A useful online video about ESD can be found on youtube: How to Avoid ESD Damage (Official Dell Tech Support) this should give you a good practical down to earth information that your looking for and help avoid some of the more serious pitfalls.  For a little more in depth explanation you might try watching: Funny video on ESD by Apple.

Some ESD wrist straps are all metal (like a watch band), and some will use an elastic band with built in metal contact points or similar conductive materials.  Note: The wrist strap should be supplied with a has an embedded 1Mohm resistor in the lead (usually potted into the cable near the banana plug end).

WARNING: You must Not wear an ESD strap if attempting to troubleshoot an energized circuit with maximum voltage over 500VDC.

As always, take off rings and watches to minimize risks.

Good online sources for wrist straps would be places like Digikey, Newark, Mouser etc.  Here is and example of a low cost one that Digikey can supply.

Hope this helps…

[Fred Kemmerer]

Hi Ed,

Here’s a reasonably priced wrist strap which should do the job –

https://www.amazon.com/Rosewill-Anti-Static-Components-RTK-002-Yellow/dp/B004N8ZQKY/ref=sr_1_3?ie=UTF8&qid=1487848475&sr=8-3&keywords=static+wrist+strap

 

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