Effectiveness of workstation design on reducing musculoskeletal risk factors and symptoms among semiconductor fabrication room workers

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Abstract

The aim of this study was to evaluate the effect of ergonomic workstation design on musculoskeletal risk factors (MRFs) and musculoskeletal symptoms (MSSs) reduction among female semiconductor fabrication room (fab) worker. A prospective study was conducted to follow up 40 female fab workers over 3 months after intervention. The intervention program focused on reducing shoulder loadings for 20 female fab workers by redesigning nine workstations. Simultaneous comparisons were made for the other 20 female fab workers using original workstations. One customized observation checklist and Nordic musculoskeletal questionnaire were used to evaluate workers’ MRFs and MSSs, respectively. One month after intervention, MRFs of awkward shoulder postures and repetitive motions and MSSs in shoulders for the intervention group were significantly lower than those for the control group. The lowering effects persisted for 3 months on awkward shoulder postures but lasted for only 1 month on repetitive motions and shoulder symptoms after intervention.

Relevance to industry

This study demonstrates a systematic approach for assessing effectiveness of ergonomically redesigned workstations tailored for female fab workers on reducing their awkward shoulder postures and shoulder symptoms. Industries can use our findings to design or evaluate their ergonomic intervention programs in the workplace or use our workstation specifications to purchase their manufacturing equipments in the future.

Introduction

Semiconductor manufacturing (SIC code 3674) workers are potentially exposed to ergonomic hazards in the manufacturing process. Previous studies investigating work-related musculoskeletal symptoms (MSSs) in this industry have shown that semiconductor fabrication room (fab) workers have heavily involved in repetitive motion tasks of manual wafer handling and static postures of wafer inspection (Pocekay et al., 1995; Wald and Jones, 1987). Their work tasks also included frequent use of video display terminals (VDTs) for process control. It was reported that musculoskeletal problems of overexertion and repetitive motion accounted for 6.2 per 10,000 full-time workers with nonfatal occupational injuries and 7.5 illnesses involving days away from work in the semiconductor industry in the United States in 2003 (Bureau of Labor Statistics (BLS), 2003). It was found that the prevalence of at least one body area discomfort was 55% in a study on 119 VDT users of a Taiwanese semiconductor company (Hsu and Wang, 2003).

Due to the globalization of economic activities and trades in semiconductor industries, most manufacturing equipments and automated machines used in Taiwanese companies were usually imported from other countries (MOEA, 2003). The human interface with improper anthropometric data for users in different countries might result in unexpected ergonomic problems, especially those of workstation-related tasks and jobs. Because the semiconductor industries usually needed to change their manufacturing process rapidly to meet the world market demands, their ergonomic hazards from inappropriate workstation designs could be more severe than other industries. Moreover, such ergonomic hazards could also affect company's productivity due to the increase of employees’ sick leaves for MSSs (Aaras and Westgaard, 1987).

A prospective study showed that 10–23% nonsymptomatic computer users had more frequent MSSs in shoulder, elbow, and low back, and 14–22% had more intense symptoms after the 17–23 months follow-up (Juul-Kristensen et al., 2004). It was demonstrated that the duration of daily VDT use longer than seven hours was associated with more shoulder, neck, and low back symptoms among 1545 clerical workers (Rossignol et al., 1987). Static posture in poorly designed workstation was attributed to neck and upper extremity loadings (Sillanpaa et al., 2003).

Several intervention studies have been carried out in the past to reduce office workers’ ergonomic hazards from VDT use by improving workstation designs. Computer users with wrist or forearm support were found to have fewer musculoskeletal discomforts than those with floating keying conditions (Cook et al., 2004). Aaras et al., 1998, Aaras et al., 2001 also showed that office workers with forearm supports at VDT workstations could effectively reduce their maximum voluntary contraction (MVC) of static right trapezius muscle load from 1.5% to less than 0.3%, and significantly lower their intensity of shoulder pains. By contrast, similar studies on redesigned workstation have not yet been conducted in the semiconductor manufacturing industry. Moreover, designing optimal fixed workstations for all workers in the semiconductor manufacturing fabs was a challenge because several fab workers with different heights usually shared one fixed workstation during their work. Therefore, this study was conducted to assess whether redesigning fixed workstations for optimal VDT use could effectively reduce musculoskeletal risk factors (MRFs) and MSSs among female fab workers who could not have their own adjustable workstations during the work.

Section snippets

Subjects

Subjects were all recruited from bay operators in the manufacturing fab of a semiconductor company. Based on findings of a previous company survey, these workers had complains of MSSs, including shoulders (68%), forearms (29%), back (21%), legs (15%), and neck (12%). After a walk-through observation on their working environment and discussing with company's managers in the risk management and facility departments, we found MSS in shoulders were the most prevalent and urgent ergonomic issue

Subjects’ basic characteristics

All of the mean age, height, weight, employment duration in the fab, employment duration in the company, and duration of working practices were not significantly different between the intervention group and the control group (Table 1). On average, their mean age, height, and weight were 26.8 year-old, 161.4 cm, and 54.3 kg, respectively. The mean employment duration in the fab and company was 2.1 and 4.5 years, respectively. Although the duration of working practices were not different between

Discussion

The findings in this prospective study suggested that ergonomically redesigned workstation was an effective intervention program to reduce female fab workers’ awkward shoulder postures and shoulder symptoms. The intervention program was effective, because using workstation with appropriate height of keyboard shelf could reduce workers’ shoulder flexion and abduction angles. By lowering the keyboard shelf's height from 1100 to 950 mm, shoulder flexion and abduction angles became fewer than 15° in

Acknowledgements

We thank the employees and managers of the study company for their invaluable support for this study. This study could not be completed without their full cooperation in carrying out the questionnaires survey and workstation modification. We are also sincerely grateful to Dr. Jia-Hua Lin of the Liberty Mutual Research Institute for Safety in the USA for his critical comments on helping us preparing this manuscript.

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