Research On The Thermal Deformation And Stress Of Metal Package With Low Resistance Leads

With the process in modern science and technology, development of electronic industries, and extensive use of electronic devices, the study of the reliability and failure in packages of electronic devices has been developed deeply. Actually the malfunction and failure of electronic devices are related to the mechanical properties of materials. In many cases, it is mechanical failure, caused by the thermal stress, mechanical vibration and micro-cracks, to lead to damage in devices. During the manufacturing and working process, thermal stresses were set up in interfaces by the mismatch of thermal expansion coefficients of the various materials used in the packages and the change of temperature. In poor packages, too large stresses are formed, which often results in cracking of chips and delaminating at mounting interfaces. Therefore, it is necessary to establish and develop a set of convenient and efficient method to test and calculate thermal stresses and deformation in the study of package design and reliability analysis.Thermo-mechanical reliability of the metal packaging with low resistance and high electric current was studied in this paper. Thermal deformations and stresses of two mental packaging structures made in China and abroad respectively, were investigated by both experimental and numerical methods. Laser speckle interferometry was used as the experimental method to test the Coefficient of Thermal Expansion (CTE) of the metal composite leads used in the packaging structures and the thermal deformations of the entire packaging structures due to the change of temperature from room-temperature to 150oC. ABAQUS/Standard Finite Element (FE) code was used to simulate the thermal deformations and stresses from room-temperature to 150oC for the packaging structures. The results of numerical simulations were in good agreement with those of experiments. It showed that the predicted thermal stresses and deformations in the working condition were qualitatively reliable. Moreover, the technique of elements deactivating and activating was used in FE analysis to simulate the manufacturing process of the packaging structures. The residual thermal deformations and stresses during the process were obtained. The results of FE simulation shows that the mental package made abroad has lower thermal stress and higher reliability during working and manufacturing process than that made in China. It is mainly because that the two packaging structures were manufactured in different forming processes: one was punched and the other was brazed....