Decision-Based Virtual Metrology Framework to Improve the Efficiency of Solder Resist Opening Qualify Control and an Empirical Study in Printed Circuit Board Manufacturing

As key component of electronic products, the importance of printed circuit boards (PCBs) has increased with the development of new technology. Recently, electronic products become thinner and shorter, combined with the demand of transmission rate and computing power, size of PCBs is becoming increasingly shrinking and therefore face the challenge of manufacturing complexity. Since the quality of PCBs will directly affect the performance and reliability of back-end products, more precise manufacturing and effective quality control are required. Solder resist (solder mask) is the surface coating on PCB, it masks off the traces to protect them from damage and prevent solder short during subsequent fabrication [1]. Each stage of solder resist process parameters and machines may affect its quality. On the surface, required pad part will be retained, called solder resist opening (SRO). The size of SRO is a critical quality characteristic. If out of spec, it may cause abnormalities during subsequent soldering, resulting in yield loss.