With the growing demand for high-performance and miniaturized electronic devices, the semiconductor industry is rapidly evolving toward complex multi-layer structures and advanced packaging technologies. These developments enable greater functionality and efficiency in smaller form factors, but they also introduce significant mechanical challenges during wafer processing.
One of the key mechanical issues is wafer bowing, a symmetric curvature of the wafer caused by internal stress imbalances. This deformation typically results from mismatches in thermal expansion coefficients (CTE) between different materials and from residual stresses introduced during thin film deposition processes. When materials like metals or oxides are deposited on silicon and then subjected to thermal cycling, they expand and contract differently than the substrate, inducing tensile or compressive stress that bends the wafer either upward or downward.
According to SEMI and recent industry reports, bowing-related deformation is responsible for up to 15–20% of yield loss in certain wafer-level packaging processes.
Although there are existing strategies to mitigate film stress through material selection and process optimization, wafer bowing remains a persistent issue, especially as devices become thinner and more thermally sensitive.
Aluminum is common material used in the welding industry due to its suitable properties, Although aluminum welding generally has disadvantages. One of these weaknesses is the formation of porosity, which will affect the welded joint's mechanical properties. porosity is formed due to two mechanisms, shrinkage porosity caused by shrinkage during the metal solidification process and gas porosity caused by air trapping and undissolved hydrogen. The welding process often produces gases such as hydrogen, carbon dioxide and steam. During welding, the metal goes into a liquid state and then cools at a rapid rate. because In a liquid there is a higher solubility of a gas than in a solid, This may trap gases inside the material and create bubbles when the welding takes place. n order to minimize the problems with the porosity of the material due to welding, it is necessary to control the speed of the process, thermal gradient, dynamics of melt pool flow and solidification. Therefore, in order to solve this problem, we use laser beam welding.
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