Handling of microelectronic devices
The voltage and current requirements for microelectronic devices are of a very low magnitude. It is therefore necessary to observe strict precautions to avoid damage or destruction when carrying out functional testing and fault diagnosis. There are some devices whose circuits can, by the very nature of their construction, be damaged or destroyed by “Static Electricity” discharges resulting simply from the manner in which they are handled.
These device are referred to as “Electrostatic-Sensitive Devices” (ESD). The type of devices that are most susceptible to damage by static electricity On aircraft precautions
When replacing Line Replacement Units (LRUs), containing ESDs on aircraft, the following safety precautions must be observed.
1. All electrical power from the system should be removed by pulling the system circuit breaker(s).
2. If the power is not removed during LRU removal or installation, transient voltages may cause permanent damage.
3. After the removal of an LRU from its rack, a conductive shorting dust cap must be installed on each of its electrical connectors. Under no circumstances must the electrical pins in the connectors be touched by hand.
4. The conductive dust caps from the unit to be installed can be use on the unit being removed.
5. The removed unit is then transported with the conductive dust caps fitted.
Aircraft are often fitted with racks containing removable circuit boards, or cards, which often contain ESDs.
During the removal and replacement of the cards, the following procedure is to be followed:
1. The body of the operator must be grounded by using the wrist strap provided, connected to the appropriate ground jack.
2. The card is removed using the top and bottom, or left and right, extractors on the card. Touching the connectors, leads or edge connectors of the card must be avoided.
3. The removed card is placed in the conductive bag, which is then secured, in accordance with the manufacturer’s approved procedure.
