Reliability analysis and parameter optimisation of board-level BGA packaging structures under thermal-drop impact load

Purpose As electronic products become more pervasive, instances of their unintentional dropping during periods of high power consumption are becoming increasingly prevalent. Thermal loads can induce fatigue damage in the solder joint material, whereas drop impact loads can instantaneously impose substantial mechanical stresses. Consequently, the purpose of this paper is to investigate the mechanical behaviour of solder joints when subjected to the concurrent effects of heat and drop impact loads. Design/methodology/approach In this paper, a three-dimensional finite element model of board-level ball grid array (BGA) package structure is established, and numerical calculations are performed based on thermal-drop impact load sequence coupling. The effects of chip thickness, solder ball height, diameter and array on its temperature field distribution, solder ball stress and average impact life are investigated. Optimisation schemes were designed using Taguchi quadrature and surface response method. The optimal combination of structural parameters to minimise solder ball peeling stress was obtained by mathematical-statistical analysis and regression analysis. Findings The results show that increasing the height and diameter of the solder balls is beneficial to reduce the package temperature under the actual temperature loading induced by the chip power, and the temperature is lowest when the number of solder ball arrays is 12. Under the thermal-drop impact load sequence coupling, the maximum peeling stress value appears at the edge of the contact area between the tip of the outermost fillet ball and the substrate, and the larger the height and smaller the diameter of the ball, the greater the ability to resist the drop impact load. The average collision life was 1.12 times longer at 0.34 mm solder ball height than at 0.32 mm, and 2.02 times longer at 0.56 mm diameter than at 0.58 mm. Under the same conditions, the optimisation results of surface response method are better than Taguchi orthogonal method, and the optimal parameter combinations are chip thickness 0.285 mm, solder ball diameter 0.56 mm, height 0.325 mm and pitch 0.592 mm. The maximum peeling stress is reduced by 19.50% compared with the pre-optimisation period, and the average collision lifetime is increased by 1.98 times, which realises the optimisation of structural parameters of the board-level BGA package. Originality/value This study investigates the reliability of the board-level BGA package structure when subjected to simultaneous thermal and drop impact loads. The investigation encompasses the effects of dimensional parameters on the stress and fatigue life of solder balls. The optimal combination of structural parameters that minimises peeling stress in solder balls is determined. The findings of this study provide a theoretical foundation for enhancing the reliability of BGA package structures under the sequential coupling of thermal-drop impact loads.