Optimization of Surface Cleaning Process for Flexible Printed Circuit Substrates Using Plasma
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Abstract
Flexible printed circuits are currently a key component of touch screen panels for mobile phones. The parts need a strict quality control to prevent dust from covering the circuit surface. Plasma cleaning of electronic circuits is an effective method to clean off small dust particles from the work surface. However, the improper setup of plasma cleaning process can lead to the burnt surface as a result. Hence, this research applies a technique of experimental design to determine an optimal condition of plasma cleaning process for flexible printed circuit substrates. Factors examined in the experiments were the amount of argon, power of radio frequency and speed of plasma cleaning. A response variable was the contact angle of deionized liquid on the workpiece surface. According to the experimental results, the optimal cleaning condition comprised of using 8 dm3/min argon gas, 140 W radio frequency and 35 mm/s cleaning speed. By using this condition, the contact angle was in the range of 10 to 30 degrees, which caused no burning on the workpiece surface. After applying such condition to a production line, the burning defect can be reduced from 24.8% to 3.21% of 3 million parts produced per month, which is equivalent to the reducing of 744,000 to 96,300 defectives found monthly.
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