[time-nuts] Conducting Bench Top Material

[d.seiter at comcast.net]

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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