4.4.3. Eyestrain
The survey also showed that workers from LPL perceived
that they were suffering more eyestrain (MS =
2.39) than did workers fromCL (MS=2.83) (Table 5.1
and 5.2). Most complaints from LPL came from the
die-bonding (1.5) and wire-bonding (1.8) processes in
FOL where all machines are equipped with VDTs. The
VDTs mounted on top of the LPL’s FOL machines were
flashing at the rate of 2,500±250 images per hour. The
workers are required to monitor the bonding-process
images to ensure that quality parameters are maintained.
There are approximately 20,000 images flashing
per machine throughout the eight working hours
of a shift. The continuous VDT image flashing causes
eyestrain for workers. Eyestrain is caused by the excessive
use of VDTs in the die-bonding process. The
die-bonding machines with attached VDTs serve as a
position-measure vision tool; the system monitors and
measures the chip-placement position. The placement
of chips on the lead-frames requires precise positioning
to ensure that the later wire-bonding process bonds in
the right places.Workers also suffer eyestrain from the
wire-bonding process. Similar to die-bonding, wirebonding
(also with VDTs) is an ultra-high-speed running
process, with bonding speeds of approximately
12,500 wires per hour. The bonding wires (as tiny as
25 micrometers) require precise positioning.TheVDTs
serve as a measure and positioning vision system that
adjusts the chips’ position via an electronic feedback
looping system that enables the machine to minimize
bad bonding.