Temperature control with a thermoelectric cooler (TEC) during laser decapsulation of plastic packages
Ablation was carried out on high voltage Schottky rectifiers at 25°C and −5°C (with a thermoelectric cooler or TEC), at 1.0 W and 3.9 W of laser power. In-situ measurement of the reverse current was conducted and correlated to the device junction temperature. It was found that the usage of a TEC increases the number of laser scans to reach the set current compliance of 100 µA after exposing the die, for ablation at 3.9 W, although eventual damage to the device is still unavoidable. The incorporation of a TEC below the sample is also demonstrated to be effective in reducing the device junction temperature during laser ablation.
Determination of temperature change inside IC packages during laser ablation of molding compound
Abstract In addition to chemical jet etch method, decapsulation performances of electronic packages for failure analysis are virtually enhanced using lasers. Nevertheless circuits inside package could be subjected to a local thermal elevation during the package ablation process. In this paper, we introduce an innovative technique to measure the thermal behavior of an encapsulated system in situ and in real time during laser decapsulation. Measurements of the heat elevation during ablation process in the three regions of interest for failure analysis are discussed: over IC, bonding and lead-frame.
Laser removal of molded flashes from a leadframe heatsink surface
Epoxy residues on a leadframe heatsink surface of a molded integrated circuit package are a major concern for the subsequent solder plating process. Studies using a pulsed green laser to remove the epoxy residues from precoated copper-based leadframes were carried out. Effects of the laser beam mode profile and process variables on the effectiveness of residue removal and surface morphology of the heatsink were investigated. Ring marks that appeared on the laser-irradiated area were analyzed by secondary ion mass spectroscopy to determine the depth profiles of the layered structures. Calculations were carried out to estimate the temperature rise in the surface due to the laser irradiation. It is concluded that laser deflashing can be a process suitable for production uses.