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Author Topic: ESD precautions  (Read 1672 times)

mckayprod

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ESD precautions
« on: May 29, 2016, 12:56:43 PM »
Not sure where this topic fits in the forum, but I haven't seen it addressed.  I wonder what static discharge precautions the experienced builders and techs are using in this field.  I notice all the semiconductors I buy come in ESD packaging, and my previous job in an ISO 9001 factory setting had all workers in conductive smocks with shoe straps, wrist straps, controlled humidity, the whole deal.  They told us even passive components could be fried or weakened by ESD.  So, to prevent that kind of damage in my own shop, I use a grounded soldering iron and a wrist strap attached to the ground screw on the mains outlet.  Pretty minimal, but better than nothing.  I'd hate to toast a fancy opamp.  Thoughts?

Loudthud

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Re: ESD precautions
« Reply #1 on: May 29, 2016, 11:19:36 PM »
The problem I've had was when the humidity got too low. That's when you start drawing sparks when reaching for doorknobs. MOSFETs are the most sensitive, especially the smaller ones. I use anti-static mats at all work areas. I use a humidifier when things get really bad.

Enzo

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Re: ESD precautions
« Reply #2 on: June 01, 2016, 09:23:11 PM »
In your ISO lab, you have to meet certain standards all the time, whether they mean anything or not at a given moment.  No amount of static discharge is going to hurt a 6L6 or a 10 watt wire wound resistor.

In practice I have never had a problem with static.  In my work in the arcade industry, I had one bad experience. An early generation video logic board on the bench.  We had a shop cat.  I was working on a row of RAM ICs, when kitty came along and brushed herself up along my leg, and WHAM, I lost a whole row of RAMs.  And yes, I had neglected to get out my static mat and wrist strap.  And my bench was in the same room as the furnace that heated the shop, so DRY indeed.  In the field, we had issues with early Midway games like Galaxians and Pac Man.  They were static sensitive.  On a staticky carpet, you could shuffle along and touch the coin door and zap the game into reset.  NO harm, but you lost any money you had inserted.  The fix was to dilute some fabric softener - Downy we used - in a spray bottle and spray the carpet.  In the shop, I made better sure I used my mat.

I agree with LT, the MOSFETs are most sensitive, and I was always careful with CMOS logic ICs, though I never zapped one, even when I was building boards in hotel rooms.

In my experience, for the most part, I don't worry about it in SS audio circuits.  Reasonable precautions seem sufficient.   All semis come in static packaging because they are not going to waste time with two types of package and then try to keep straight what needs it and what doesn;t.  Just use ALL static bags, and whatever needs it is covered.  Tiny little surface mount parts may be more susceptible to static, but I want someone to show me a half watt resistor that was damage by someone not well grounded.  The last thing I will worry about is zapping an MJ15003 while I solder it.

I will say that when I see a part fail, it is more often one with a direct connection to the outside world, rather than one right in the middle of a circuit.   Not always of course, but usually.

Loudthud

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Re: ESD precautions
« Reply #3 on: June 02, 2016, 04:21:34 PM »
The tubes that IC's come in (if you buy enough) generally do not provide ESD protection for the parts, they merely don't generate static. The shielding bags that are generally dark metallic gray or aluminum colored do provide protection. The pink bags and pink bubble wrap generally will discharge any static buildup, but aren't as good as the shielding bags at preventing all damage.

Vitrolin

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Re: ESD precautions
« Reply #4 on: June 03, 2016, 04:35:55 PM »
IC damaged by static doesn't necesarely fail the moment they are exposed to static.

static can make the very thin connections in side ic even thinner, and the will then fry later...

 

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