Improvement of S-Ratio Measurement Method for Single-In-Line Package Leadframe Roughness

This paper aims to report the improved method for surface area increase (S-ratio) measurement that is used for controlling surface roughness of single-in-line package (SIP) leadframe. The background of this paper is from resin bleed out and delamination issues that were found in a production line, even the roughness was controlled by S-ratio. S-ratio surface roughness was rechecked and confirmed with the cross-section electron micrographs. The S-ratio results did not coincident to the cross-section leadframe surface topography. Therefore, S- ratio measurement method was revised and adjusted for improving measurement accuracy and precision. The S-ratio experiments were performed with 2 laser confocal microscope models from Olympus and Keyence. The measurement methods were varied with cross-hair center pad reference, magnification, and laser scan speed. In addition, stitching technique was tried to enlarge the measured area. The surface profile and S-ratio results showed that the precise and accurate S-ratio can be evaluated even by Olympus or Keyence with fine scan mode at 100X with cross-hair center pad reference. Moreover, S-ratio from stitching mode can be used to enlarge the analysis area.