edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 26 NO. 2 22 ELECTRO-THERMAL SIMULATION AND RELIABILITY OF A BALL GRID ARRAY Norelislam El Hami1, Aicha Koulou2, Maria Zemzami3, and Abdelkhalak El Hami4 1Science and Engineering Laboratory, ENSA, University Ibn Tofail, Kenitra, Morocco 2EST, University Ibn Tofail, Kenitra, Morocco 3ENSAM, Mohamed V University, Rabat, Morocco 4Laboratory of Mechanics of Normandy, INSA, Rouen, France abdelkhalak.elhami@insa-rouen.fr EDFAAO (2024) 2:22-30 1537-0755/$19.00 ©ASM International® INTRODUCTION Reliability is defined in industry standards as “the ability of a product to function under given conditions and for a specified period without exceeding acceptable failure levels.” The goal of solder joint reliability assurance programs is to ensure that failure rates remain below an acceptable level by the end of the design life. In critical applications such as flight or space avionics or medical products, the goal is for solder joints to remain failurefree throughout the design life. To achieve these goals, it is essential to understand and quantify the loads, deformations, and failure mechanisms experienced by solder interconnects in the field. In Clech et al.[1] and Kannan et al.,[2] the failures in the electronic component of about 55% are mainly due to the existence of high temperature during its operation.[3] The impact of temperature goes beyond material degradation and affects reliability of electronic packages as well. Temperature rise generates thermal stresses in structures that consist of different materials with different thermal expansion coefficients. The impact of the mismatch of thermal expansion coefficient may be augmented by non-uniform temperature distribution within the structure, as in the case of electronic packages. The level of thermal stresses within electronic packages is a key factor directly affecting package reliability.[4] This article is structured in three main sections. In the first section, mathematical elaborations of the coupling equations for the electro-thermal and thermomechanical domains are provided. The second one focuses on the overview of the system, describing the geometry, the materials attached to it—especially the SAC (the acronym SAC stands for the elements tin, Sn, silver, Ag, and copper, Cu, of which the alloy consists) alloys—and the initial and boundary conditions. In the third section, the multiphysic numerical simulation achieved on ANSYS Workbench in order to define the most convenient and reliable solder alloy after submission to electro-thermal load is illustrated and mechanical outputs are analyzed and discussions are held. THEORETICAL STUDY OF ELECTRO-THERMAL COUPLING The reliability of an electronic package is strongly dependent on its electrical, thermal, and mechanical behavior. Thermal management controls device temperature that affects functional performance as well as long-term reliability. The failures resulting from high stresses/strains can be driven by the thermal expansion differentials due to different expansion properties and temperature gradients. ELECTRICAL FIELD The electric current density, S, in conductors can be estimated using Ohm’s law and the law of charge conservation that are:[7] J = - ς ·∇V = −1/ϱ · ∇V (Eq 1) ∇J = 0 (Eq 2) where: ς is the conductivity, ϱ the resistivity, and V represents the electric potential. The physical phenomena that condition the electrical behavior of semiconductor devices are intimately linked to component temperature. The Joule effect is considered as heating that occurs in a conductor carrying an electric current. Joule heat is proportional to the square of the current and is independent of the current direction.[11] It
RkJQdWJsaXNoZXIy MTYyMzk3NQ==