[time-nuts] Conducting Bench Top Material

Bob Camp lists at cq.nu
Thu Jan 28 12:21:03 UTC 2010


Hi

If we ever go back to tubes we're going to have a bunch of tech's knocked out on the floor. Nobody has a clue about high voltage any more. You had to have a good respect for it on a tube circuit or you got in big trouble. 

Bob


On Jan 27, 2010, at 9:23 PM, Steve Rooke wrote:

> Wasn't life so much easier with valves (tubes)...
> 
> :-)
> 
> Steve
> 
> 2010/1/27 Bob Camp <lists at cq.nu>:
>> Hi
>> 
>> If you are manually loading up a wire bonder with conventional CMOS chips, ESD damage is a very real thing. You can haul the chip over to a SEM and actually take pictures of he craters you blast in it. Very cool pictures. No cat's, carpets, or Windhurst machines needed.  Just normal operators with missing wrist straps will do the trick quite nicely.
>> 
>> Bob
>> 
>> 
>> On Jan 26, 2010, at 2:21 AM, d.seiter at comcast.net wrote:
>> 
>>> Back about 1981, we had piles of 6502s, etc and decide to some "antistatic testing". We put a 40pin ZIF socket into a VIC-20, and then set about trying to fry the uP using carpet, a cat, car seats, etc. The DUT was then put back into the VIC and series of tests run to verify operation. I don't think we ever had a failure. Of course, there may have been some hiding that we missed, but all the static damage I've seen has been pretty severe.
>>> 
>>> That said, I always use a wrist strap and mat if I'm working on something I don't want to break further.
>>> 
>>> -Dave
>>> ----- Original Message -----
>>> From: "Charles P. Steinmetz" <charles_steinmetz at lavabit.com>
>>> To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
>>> Sent: Monday, January 25, 2010 11:27:11 AM GMT -07:00 US/Canada Mountain
>>> Subject: Re: [time-nuts] Conducting Bench Top Material
>>> 
>>> Bruce wrote:
>>> 
>>>> Although over the years the non-conductive top has been an asset in
>>>> avoiding short circuits, etc., I am concerned about static discharges when
>>>> handling modern semiconductors. Would it make sense to spray the Masonite
>>>> with a weak copper sulphate or similar solution so as to make the masonite
>>>> slightly conductive, but not so conductive that 155 VAC connections
>>>> could not
>>>> safely rest upon it? Is there a better-suited material that could be used
>>>> to replace the Masonite?
>>> 
>>> I notice that many folks who have contributed on this thread use
>>> anti-static benchtops, but I have never found it necessary (and I try
>>> to keep the RH in my house under 45% -- it is generally 20% or less
>>> in the winter). I've been fooling with static-sensitive parts for 35
>>> years and haven't lost one to static yet. With that perspective, my
>>> preferred benchtop is white Formica with a very, very slightly
>>> pebbled surface. Very durable, including to molten solder, and small
>>> parts show up well. I use rubberized "gunsmith" mats for preventing
>>> scratches to delicate workpieces (these happen to be anti-static, but
>>> that is not why I have them).
>>> 
>>> Other bench thoughts:
>>> 
>>> Bench depth is very important. I sometimes work on equipment that is
>>> more than 24" deep, so I want at least 30" of clear space in front of
>>> any obstructions (power strips, Variac, test equipment,
>>> whatever). In the past, I used a "flying bridge" over the rear 18"
>>> of a 48"-deep bench to elevate the test equipment, which worked very
>>> well. Now I use 24" deep adjustable wire-rack shelving units behind
>>> a 30" benchtop (As others have pointed out, you can do the same with
>>> equipment racks -- I'm not a fan of rack-mounting test equipment
>>> unless the racks are anchored and everything is on slides, which I
>>> was not prepared to do). I don't have enough shop real estate to
>>> have a permanent access aisle behind the test equipment, so the bench
>>> and racks have large (5") locking polyurethane wheels and can be
>>> pulled out relatively easily for reconfiguration. This provides
>>> plenty of stability for electronic projects, but you wouldn't want to
>>> mount a big vise on the bench and try to bend 1" rebar. For that, I
>>> have a separate metalworking shop.
>>> 
>>> Bench height is also important. I prefer a tall bench, suited to
>>> working standing or sitting on an ergonomic stool, so my bench top is
>>> 44" above the floor -- a bit below my standing elbow height.
>>> 
>>> Finally, one can never have too many power outlets, or too much
>>> light, in a workshop. Lighting should be arranged so that it doesn't
>>> cause specular reflections from the workpiece or the faces of test equipment.
>>> 
>>> Best regards,
>>> 
>>> Charles
>>> 
>>> 
>>> 
>>> 
>>> 
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>> 
>> 
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> 
> 
> 
> -- 
> Steve Rooke - ZL3TUV & G8KVD
> A man with one clock knows what time it is;
> A man with two clocks is never quite sure.
> 
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