Verification of the thin film metal layer thickness by energy dispersive X-ray

Abstract

Leadframe fabrication process normally involves additional thin film metal layer plating on the bulk copper substrate surface for wire bond purpose. The recent commonly adopted plating materials are silver, tin, and copper flake. To assess the thickness quality, the conventional X-section methods involving grinding and polishing process are utilized. However, the process may lead to inaccurate results, which stems from the occurrence of sample preparation artifact, such as smearing effect attributable to the grinding or polishing process. Thus, alternative advanced methods are developed for assessing the thin film metal layer thickness, such as Focus Ion Beam (FIB), SIMS profiling or XPS, readily available in worldwide market. However, these alternative measurement services are very costly and time consuming per sample measure. To cater the cost and long sample preparation time due to the abovementioned advanced methods, an Energy Dispersive X-ray (EDX) can be applied. In this study, the newly invented methodology breakthrough had been validated by applying EDX for the first time on known bulk elemental analysis purpose. EDX feature is not only useful for elemental analysis but also applicable for thin film-metal layer thickness measurement and bulk material densification determination. A promising result was observed from the detailed experiment work through applying EDX in this evaluation.