> As you can see the case is made nwith a process called rotomoulding.
> I don't know the specifics of the process and materials used but I 
> can tell
> you for sure that the cases come to the assembly area with lots of 
> static
> (i.e.. Plastics "stick" to them...)
>
> Now, the system has a RTC on it and a PIC (16C63B) the problem I'm
> having is that some RTCs (DS1307) are being damaged and I think is 
> due to
> static....

Some or all of:

    Static control.
    Static protection.

A high humidity atmosphere will reduce electrostatic charge.
Many companies sell static control surface treatment products eg 3M. 
Most are not adequate for delicate electronic product protection.
SOME clothes treatment fabric softener products will help.
High capacity Negative Ion Generators are available to neutralise 
static charge.
Wiping all surfaces with a grounded conductive material will help.
Storage for a while after surface treatment will help.
Rubbing some plastics with some other materials or against each other 
can generate static charge.
Transport and store in ESD discouraging containers and environment.

All workers must have ESD protective equipment in this sort of 
environment.
Earth straps, bench mats, floor mats, heel grounders, negative ion 
generators, ...
Ensure workers clothes and seating etc do not cause ESD.

If there is heavy electrostatic contamination then either you are 
going to allow the workers to be charged by the product or the product 
to be discharged by the workers.

An electrostatic meter will tell you when you have problems, if you 
have cured them, and what remains. Can be very cheap & simple if 
desired.

Butyl rubber roofing and pond lining material can make extremely cost 
effective antistatic mats for floors and benches and transport boxes.
Conductivity depends on carbon loading (I think) and varies. Get 
multimeter and insert two probe tips into sheet perhaps 2cm apart. ANY 
conduction on any range means it is probably OK. Some Butyl rubbers 
are VERY low resistance and a potential shock hazard as they then 
constitute an earthed surface.

Use real ESD wrist straps or at least add say 1 megohm resistor in 
ground lead to reduce shock hazard. DO NOT use plain wire to ground.

Protect ICs at all times AND protect connectors etc on finished 
boards. Ensure staff know and follow ESD safe procedures. Provide 
earthing points for staff to use when they sit or handle or approach 
equipment (include resistors).

Ensure soldering and desoldering equipment etc is ESD safe. Also 
ensure that if hand irons are used that tips do not have leakage 
voltages on them - death to ICs.

Where should I send the invoice ? :-)


        Russell McMahon




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