Elecraft KXPA100 Assembly Manual - Manual (Page 5)

5
Preventing Electrostatic Discharge Damage
Sensitive components may be damaged by Electrostatic Discharge (ESD) simply by touching them or a circuit
board containing them unless you take specific steps to prevent such damage. Damage may occur with static
discharges far too little for you to notice.
A damaged component may not fail completely at first. Instead, the damage may result in below-normal
performance for an extended period of time before you experience a total failure.
Parts which are especially ESD-sensitive are identified in the parts list and in the assembly procedures.
We strongly recommend you take the following anti-static precautions (listed in order of importance) to ensure
there is no voltage difference between the components and any object that touches them:
 Leave ESD-sensitive parts in their anti-static packaging until you install them. The packaging may be a
special plastic bag that allow static charges to flow harmlessly over their surface, or a component’s
leads may be inserted in conductive foam that keep them at the same potential.
 Wear a conductive wrist strap with a series 1-megohm resistor that will constantly drain off any static
charge that accumulates on your body. If you do not have a wrist strap, touch a ground briefly before
touching any sensitive parts to discharge your body. Do this frequently while you are working. You can
collect a destructive static charge on your body just sitting at the work bench.
WARNING
DO NOT attach a ground directly to yourself without a current-limiting resistor as this poses a
serious shock hazard. A wrist strap must include a 1-megohm resistor to limit the current flow. If
you choose to touch an unpainted, metal ground to discharge yourself, do it only when you are
not touching live circuits with any part of your body.
 Use a grounded anti-static mat on your work bench (see below).
 If you pick up a pc (printed circuit) board that was not placed on an anti-static mat or in an anti-static
package, first touch a ground plane connection on the board such as a connector shell or mounting
point.
 If you use a soldering iron to work on a circuit board, be sure your iron has an ESD-safe grounded tip
tied to the same common ground used by your mat and wrist strap.
Choosing an Anti-Static Mat
An anti-static mat must bleed off any charge that comes in contact with it at a rate slow enough to avoid a shock
or short circuit hazard but fast enough to ensure dangerous charges cannot accumulate. Typically, a mat will
have a resistance of up to 1 Gigaohm (10
9 ohms). Testing a mat requires specialized equipment, so we
recommend that you choose an anti-static mat that comes with published resistance specifications and clean it as
recommended by the manufacturer. Testing has shown that many inexpensive mats that do not specify their
resistance have resistance values much too high to provide adequate protection, even after they were cleaned
and treated with special anti-static mat solutions.
Suitable anti-static table mats are available from many sources including:
 U-line (Model 12743 specified at 10 7
ohms)
 Desco (Model 66164, specified at 10 6 to 10 8 ohms)
 3M TM Portable Service Kit (Model 8505 or 8507, specified at 10 6 to 10 9 ohms)