Numerical Simulation Of The Laser Welding On High-silicon Aluminum Alloy For Electronic Packaging

High-silicon aluminum materials has been widely used for electronicpackaging in recent years, but high-silicon aluminum internally contains a largenumber of silicon particles, and also because of the surface oxide film, the weldingproperties is poor, with a higher tendency to crack formation. Pulsed laser weldinghas lower welding heat input, suitable for micro-parts and precision components. Inthis paper, the numerical simulation method is used to research temperature field,welding stress field and post-weld residual stress distribution of pulsed laserwelding of high-silicon aluminum alloy shell, trying to find a reasonable weldingparameters, in order to avoid the formation of cracks and overheating tendency ofthe chip on the backplane of the shell.After a comparative analysis, a Gaussian surface heat source plus acombination of three-dimensional cone heat source heat source model was used.According to the characteristics of the pulse laser power, triangular periodicfunction was used, so the cyclic loading of the heat source power was achieved.Through thermal simulation of the welding process of the shell, the temperaturedistribution and the trend of the shell in the welding process were analyzed. In thewelding heating process, the temperature gradient near the connector is higher, andthe shell temperature continued to rise with the welding process, the chip fixed onthe bottom plate has a large tendency to overheat in the completion of the lastchannel welds.Through the simulation of shell welding stress changes and post-weld residualstress, the presence of the puddle terminal biaxial tensile stress in the brittletemperature range was analyzed, therefore a higher tendency to solidificationcracking formation was existed. There’s higher longitudinal tensile residual stressin shell welds at room temperature, and brittle crack formation tendency of certainlow plasticity.Through the simulation, the influence to welding shell temperature distribution bythe laser pulse width, welding speed and intermittent was analyzed, the reasonablespecification was determined to ensure that the weld appearance forming andsealing performance. The options of welding speed range is very limited, and by reducing the pulse width or use intermittent welding, it can effectively reduce thetemperature of the soleplate to avoid chip overheating.In order to verify the accuracy of the simulation, the determination of thedynamic temperature field welding and the detection after welding residual stresswere done. By comparison, the high accuracy of temperature field simulation wasverified, and due to the existence of initial stress, in the powder molding highsilicon aluminum shell, the detection results and the simulation results are of largedifferences.