JICOSH was closed in 2008. For further information, please contact JISHA.
JICOSH Home > Case Studies > Case No.7
Case No.7

Electrocuted while repairing semi-conductor manufacturing equipment 

Click Here
[Circumstances of Incident]

This accident occurred in a semi-conductor manufacturing plant where 4Mbit memories and other products are produced.

The victim in this accident worked for a subcontractor of the parent company, which owned the plant where the victim and his colleagues were engaged in silicon wafer polyimide processing and back face processing. On the day of the accident, two maintenance workers, including one leader, started repair work when a sputtering unit used in the processing wafer surface failed.

As the first step, workers tried to replace a power amplifier and an intermediate amplifier with no success in restoring the functions of the unit. They then checked the voltage inside the high-frequency power source unit and detected abnormal figures in the voltages of four inspection terminals.

After taking a rest break, the leader made a telephone call at about 2:30 to the maintenance company responsible for the unit to report their failure in repairing the sputtering unit. He came back to the repair site about one hour later, and found the victim lying unconscious on the floor between the sputtering unit and the power source rack.

The victim's body showed evidence of electric current passing through from the first and second fingers of the right hand to both knees and legs. In addition, some rubber-like material was adhering to a burned spot near the bottom of the metal cap on the top of the power amplifier in the high-frequency power unit. 


The following can be cited as the causes of this accident.

1. The power source was turned on.

Although the leader had turned off the power switch of the high-frequency power unit by himself before taking break, the victim turned on the switch while the leader was talking to the maintenance company by phone to locate the failure and perform other repair work.

2. Personal protective equipment to prevent electric shock was not used.

The victim was wearing polyester work clothes for the clean room, with a hood and anti-static rubber shoes, but no anti-shock protective equipment.

3. Wrong operational procedures

The sputtering unit handling manual indicates that the unit can generate electrical discharges and requires adequate precautions for high voltages. However, the worker started the operation without reconfirming the contents of the manual.    

[Type of business] Electronic and electric equipment parts manufacturing industry
[Type of accident] Electric shock
[Number of victims]One fatality