3D laser trimming technology for regulating embedded thick-film carbon resistors on a random access memory module

This study presents a novel solution for regulating embedded thick-film carbon resistors on random access memory (RAM) modules using 3D laser trimming technology. The embedded passive components, which are printed on a substrate using liquid-polymer ink, are employed due to their rapid response time. The original resistance of such resistors, however, is less than the target value. Hence, a 3D laser trimming technology is proposed for etching thick-film resistors and reaching a target resistance value with online assistance of a four-wire resistance measurement device. A laser beam deflection path with a spiral cycle is manufactured on the printed thick-film to superficially thin the resistor using a wobble-grinding function in a layer-by-layer manner. Resistance material was removed by each laser pulse until the target resistance was obtained. Twelve RAM modules were tested. Experimental results demonstrate that the resistance value of the trimmed resistors was an averaged accredited percentage of 88.54% with a tolerance of 5%. All trimmed resistors with a tolerance of 10% were obtained. Furthermore, 144,000 embedded thick-film carbon resistors on 1800 RAM modules were trimmed in a factory using the proposed scheme. Measurement results indicate that an average accredited rate of 95.67% with tolerances of 5–20% was obtained for industrial applications. Therefore, the proposed technology is a practical and efficient solution for regulating thick-film carbon resistors on RAM modules and other related products.