Papers by Author: Jean Marc Heintz

Abstract: Today, there is a strong push to improve the thermal management of electronic components in order to increase the performance and the reliability of electronic devices. Up to now, most of the heat sinks are mainly made of Copper that presents a good thermal conductivity (TC) but a coefficient of thermal expansion (CTE) much higher than the ceramic of the DBC (direct bonding Copper). It induces interfacial thermal stresses and indeed it decreases the reliability of the global electronic system. Therefore, there is a strong need for the development of novel heat dissipation material having low CTE combined with high TC. Carbon fibres reinforced copper matrix offers a good compromise between thermo mechanical properties (i.e. CTE) and medium TC. In order to increase surface TC, pure Copper can be added on the top surface and/or on the bottom one of the composite heat sink playing the role of heat spreader for hot spots linked with the Si components. The fabrication technique of these materials is based on powder metallurgy technique. The thermal properties of adaptive materials, TC and CTE, have been measured for different Copper thicknesses and architectures ([C/Cu], [Cu – C/Cu] and [Cu – C/Cu – Cu]). Simulation of the TC and CTE have been performed and compared to the experimental results.

Abstract: This study deals with the co-sintering of copper oxide added ANT with alumina tapes and silver ink. AgNb1/2Ta1/2O3 (refered ANT 22) was synthesized using niobium oxide with fine and large grain size to examine the effect of the granulometry on the tape casting. The resulting multilayers were co-fired between 850 and 900°C. Phase identification was investigated by XRD. Energy Dispersive Spectroscopy was performed to study the interdiffusion between the layers. Permittivity and dielectric losses were measured at 50 kHz for both tape cast samples and bullk material. No interdiffusion was observed between ANT/silver and ANT/alumina and this is a very promising result for LTCC applications.

Abstract: A study of the different stages of the electroless deposition of copper on carbon nano fibers activated firstly by a chemical treatment of the carbon nano fiber and secondly by a two-step method has been performed from both a chemical and a morphological point of view. The combination of XPS measurements and scanning electron microscopy imaging has allowed optimizing the 2 different stage conditions. On a first hand, the different oxide concentration and treatment time of the carbon nano fibers and on a second hand the different conditions of the sensibilisation (Sn bath), activation (Pd bath) and coating (Cu bath) have ben studied. The control of the homogeneity and thickness of copper thin films on carbon nano fiber can be obtained and further more sintered in order to obtain fully dense materials.