9.1 General Precautions 1) Environment The electrostatic level in the work environment where semiconductor devices are handled is generally regarded to be 100V or less. Therefore, consideration is required by not placing any substances that are prone to produce static electricity in the work area or by humidifying the area in the dry period. 2) Work Avoid the insulators that are prone to being charged such as chemical fibers and plastics in the work area and use conductive materials.

Especially when the semiconductor devices susceptible to static electricity are handled, consideration is required such as by storing them in containers of the material with electrostatic countermeasures taken or in conductive containers or by wearing antistatic work clothes and conductive shoes as well as by installing a humidifier or ionizers as needed. 3) Periodical Inspection Periodically check the effects of antistatic measures.

Periodically check the amount of static electricity generated in the process, breaks in ground wires to equipment, jigs, and wrist straps, and antistatic performance of the ionizers. Please note that especially the antistatic performance of the ionizers will decrease unless its needlepoint is periodically cleaned or replaced according to the instruction manual.

9.2 Measures Against Static Electricity During Work 1)Equipment and Jigs Connect test equipment, conveyor, work table, floor mat, tools, solder bath, and solder iron to the ground to prevent the accumulation of static electricity. Use conductive work tables covered with unpainted metal plate (copper or the like) or conductive mat, and use a conductive floor or spread a conductive sheet on the floor. Connect each to the ground. Use conductive carts and chairs and connect them to the ground. Connect moving carts to the ground by metal chains or conductive belts. Connect a cord-type wrist strap to the ground. It is said that using the cordless type causes the human body to remain an electric charge of approximately 200V without removing charged electric potential.

When connecting a wrist strap to the ground, use a grounding jig designed specifically for wrist straps without fixing it to the earth line by an alligator clip or bagworm clip. There are cases where appropriate effects could not be obtained with the oxidized surface of the bare copper wire with deterioration over time when a bare copper wire was connected to the ground by clamping it by an alligator clip. Also, use a humidifier and ionizer as needed.

- Precautions for using a humidifier

Static electricity is prone to be abruptly generated when humidity is 30% to 40% or less. Therefore, it is regarded as appropriate to keep the working environment for semiconductor devices at a humidity of 45% or more.

A substantial amount of static electricity is charged to the body of a human who has walked on a carpet wearing synthetic shoes. The image of changes of this relative to humidity as well as the relationship between the amount of static electricity generated and humidity in the environment generated is shown below. According to the handbook by the United States Department of Defense (DOD-HDBK-263), the relationship between the amount of static electricity generated and humidity by environment is shown as follows: When a humidifier is used, it is recommended to use deionized water to prevent the formation of rust on lead terminals. When using tap water, remove chlorine causing rust by boiling before use.

For plastic packages often used in semiconductor devices, epoxy type resin is often used. Such plastic packages are prone to absorb moisture. Therefore, the characteristics are prone to deteriorate and rust formed on lead terminals when stored at high humidity. Please note that especially damp-proof packed products are susceptible. －Use ionizers as needed.

When using ionizers to neutralize the static electricity generated, fix the bodies in such a way as to prevent direction changes after installation, considering the effective neutralization range of the ionizers.

For the pulse DC type and pulse AC type ionizers, set the appropriate frequency according to the distance to the neutralization object.

To maintain the antistatic performance of ionizers, it is generally said that periodic checks and maintenance are required as shown below. Periodic checks

－Check of antistatic performance

－Check of an ion balance Periodic maintenance

－Cleaning of electrode needle tips (Clean the needle tips with alcohol once every month.)

－Periodic replacement of electrode needles (Replace them every year or every two years depending on the needle tip material.) For details, check the instruction manual for the ionizer used and contact the manufacturer for any questions. 2) Workers Workers must wear antistatic work clothes and conductive shoes and connect the human body to the ground by a wrist strap. Wear gloves to prevent making contact with semiconductor devices with bare hands.

Values of 100 KΩ to 100 MΩ are generally regarded as appropriate as the resistance values of shoes. Periodically clean shoes since the resistance values vary depending on the contamination of the soles of shoes or floor and antistatic effect decreases. 3) Working Method Use a soldering iron for semiconductors and connect the soldering tip to the ground.

When mounting a semiconductor device, in order to prevent breakdown of the semiconductor device, work over a short period of time by decreasing the frequency of handling the same device as well as the handling time.

9.3 Measures Against Static Electricity After Mounting 1) Storage When storing and transferring the PCB substrate after mounting a semiconductor device, store it in a conductive bag or conductive container. In addition, make short-circuit the connector of the PCB substrate by aluminum foil, substrate shorting bar or the like. 2) Handling When handling the PCB substrate after mounting a semiconductor device as well, connect the human body to the ground by a wrist strap or the like. When handling the PCB substrate, pay sufficient attention to static electricity as is the case with mounting the semiconductor device. Before inserting into or removing it from the connector, make sure to turn off the power.

9.4 Human Body Protection Human body grounding is effective as a measure against static electricity. However, when an operator gets an electric shock, he/she is exposed to a higher danger than usual situations. In human body grounding, it is required to consider both measures against static electricity and human body protection.

Normally, resistors are placed in series between a human body and ground. A larger resistance value decreases the effect of measures against static electricity by grounding. In case of a smaller resistance value, high current flows through the body, being exposed to danger, when the operator gets an electric shock.

Generally, a resistance value of 250 KΩ to 1 MΩ is regarded as appropriate between a human body and grounding.

Generally, a resistor with a similar value is built in a commercially available wrist strap.s