Thermal Characterisation of Hybrid, Flip-Chip InP-Si DFB Lasers.

WA detailed thermal analysis of a hybrid, flip-chip InP-Si DFB laser is presented in this work. The lasers were experimentally tested at different operating temperatures, which allowed for deriving their thermal performance characteristics: the temperature dependence of threshold current, lasing slope, and output spectrum. Using these data, the laser thermal resistance was calculated (Rth = 75.9 K/W), which allows for predicting the laser temperature during operation. This metric is also used to validate the thermal finite element models of the laser. A sensitivity study of the laser temperature was performed using these models, and multiple routes for minimising both the laser thermal resistance and thermal coupling to the carrier die are presented. The most effective way of decreasing the laser temperature is the direct attachment of a heat sink on the laser top surface.

Study of the effect of Sn grain boundaries on IMC morphology in solid state inter-diffusion soldering.

This paper reports on 3D phase field simulations of IMC growth in Co/Sn and Cu/Sn solder systems. In agreement with experimental micrographs, we obtain uniform growth of the CoSn3 phase in Co/Sn solder joints and a non-uniform wavy morphology for the Cu6Sn5 phase in Cu/Sn solder joints. Furthermore, simulations were performed to obtain an insight in the impact of Sn grain size, grain boundary versus bulk diffusion, IMC/Sn interface mobility and Sn grain boundary mobility on IMC morphology and growth kinetics. It is found that grain boundary diffusion in the IMC or Sn phase have a limited impact on the IMC evolution. A wavy IMC morphology is obtained in the simulations when the grain boundary mobility in the Sn phase is relatively large compared to the interface mobility for the IMC/Sn interface, while a uniform IMC morphology is obtained when the Sn grain boundary and IMC/Sn interface mobilities are comparable. For the wavy IMC morphology, a clear effect of the Sn grain size is observed, while for uniform IMC growth, the effect of the Sn grain size is negligible.

Novel technology for microlenses for imaging applications.

Microlenses are an important functional element of a modern imaging device. Typically, they are fabricated from organic materials on top of individual pixels. Though they are widely used, they do exhibit a number of limitations. These are, but not limited to, thermal stability, radiation sensitivity, outgassing properties, additional topography, and difficulty in manufacturing asymmetrical, noncircular microlens designs using conventional manufacturing techniques. In this paper, we present a novel approach for the fabrication of microlenses. We report on the design, manufacturing, and characterization of microlenses fabricated from classical dielectric materials used in the manufacturing of CMOS semiconductor devices. These microlenses rely on a Fresnel optical design, provide functionality similar to the classical microlenses, and do not suffer from their limitations. We subjected these microlenses to several environmental reliability stress conditions, including pressure, temperature, humidity, and their variation. Moreover, we test their sensitivity to gamma rays and protons.