Return to index

Handling static sensitive devices

Many components in modern cars are sensitive to static damage. This note gives some information and advice about the safe handling of such equipment. Examples are the Engine Control Module (ECM), Powertrain Control Module (PCM), Instrument Panel Cluster (IPC), Radio, Electronic Brake Control (EBC) and many others.

Please read all these notes together.

Many electronic equipments can be considered to be "static sensitive". This means that their electronic components are vulnerable to damage from the natural static electricity that builds up on people and other objects if not properly discharged.

In the event of static damage, components might fail immediately or might continue to operate, but suffer unexpected failure later.

To eliminate the problem you, and the work place where you handle static sensitive components must be designed to discharge any static electricity that might build up and in a safe manner. "Safe" means safe to you and the component/device being handled.

Static electricity arises when non-conducting materials move (rub) over each other. The most spectacular is the lightning discharge in a thunderstorm caused by two air masses moving past each other. This involves considerable amounts of energy and very high voltages (many thousands). However, electronic components can be damaged at much lower voltages, starting from as low as five volts.

Static electricity is generated every time you move, but the principal causes are walking on a man made surface (e.g. a nylon carpet), movement in your chair (clothes against the fabric of the seat) and movement between your clothes and yourself. As a rule man made materials (nylon, polyester) are more vulnerable than natural materials such as leather and cotton. Voltages of hundreds to low thousands are common.

The "snap" of a static discharge that you can hear on a dry day occurs at voltages far in excess of those at which damage might occur in electronic devices. Thus you will not be aware if you are carrying dangerous levels of static, you must assume that you are. To protect an electronic device, you, your tools, your work bench and the electronic device must be at the same potential. Practically speaking that potential value is ground.

In order to discharge any static electricity that might build up, you need to discharge it to ground. For the home hobbyist, the best way to achieve this is by wearing an appropriate wrist strap. The wrist strap will have a wire to ground to discharge any body potential. The ground wire MUST contain a series resistor of at least 1 million ohms, (10M is a good value) for YOUR PERSONAL SAFETY.

Your work environment needs to be grounded, also through a similar size resistor. I use a mat of conducting foam, sold to transport chips. I buy it in sheets a bit bigger than 8.5x11 paper. (However, never apply power to your project while it is resting on such material, you have shorted out all the tracks.)

If you use a wrist strap, you should check it before each use, a VOM (Volts Ohms meter) should be sufficient for this.

If you don't have a wrist strap, you need to keep yourself grounded. Sitting in a grounded chair will work, or keep one hand on the grounded work surface. You must also minimize the generation of static by keeping still in your chair, not moving your feet over the floor etc. If you do move, re-ground yourself before you do anything else. I use the case of my bench power supply if I am not wearing my wrist strap. If you are taking a computer apart, the metal box of the power supply is good, but only if you have left the computer plugged in. The ideal is if you have a switched outlet, where you can switch off the supply but leave the ground connected. Most US 110v outlets are not switched however.

You must bring components into the "safe area" after removing any static that might be present on them. This will be done while they are in their case or protective cover. Static removal is achieved by wiping the item's bag onto a grounded object. If you are wearing a wrist strap, you will serve this purpose by simply picking up the item. Components and equipment provided in a "silvered" bag can be considered to be static sensitive and this "wiping" action is a key part of discharging any static that might be present. You do this before removing the device from the bag, but after opening it.

Occasionally it is necessary to solder static sensitive devices. In this case you should ground your soldering iron bit again through at least a 1M resistor. The soldering iron will generally have a screw terminal on the side for this purpose. The use of a soldering iron which includes an isolation transformer in the base is recommended, as the chance of damaging leakage current from the line is greatly reduced.

If the environment is very dry (e.g. some offices with air conditioning), the risk of static damage is very much greater. High humidity helps to reduce static damage. If you work with electronic equipment (computers) in a very dry environment, humidifying the air could be good for both you and the equipment.

In practice, electronic devices that are fully attached to their board are less vulnerable to the problem of static than discrete components that have not yet been attached. It would also be true to say that most hobbyists are not going to come into contact with the very sensitive devices, but it is still wise to take precautions.


As with all safety related advice, these notes on handling static sensitive devices are offered to you on a "use at your own risk" basis.

Submitted by: Jon Gordon-Smith; checked by Bruce Roe.