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借助有限元模拟仿真软件ANSYS,研究分析了不同的封装体、芯片和框架厚度,以及散热底和芯片基岛尺寸对于小尺寸两边扁平无引脚(DFN)封装器件在回流焊温度条件下的热应力及翘曲变形分布影响。结果表明:封装体等效热应力最大处位置均位于框架、芯片和塑封料将银浆包裹处(即:银浆溢出的三角区域),其数值随封装体厚度减薄呈递减趋势;整体的热应力分布也随之沿着芯片、银浆和框架结合界面的中心位置向银浆三角区域延伸并逐步增大;对于薄型DFN封装体,芯片厚度、散热底和芯片基岛尺寸对于封装体总体翘曲变形的影响较小;框架厚度对于封装体总体翘曲变形及等效应力的影响较大;通过适当地减薄封装体厚度,并同时减薄框架厚度可以有效地降低封装体热应力,且总体翘曲变形都在1um以下。
With finite element simulation software ANSYS, the different package, chip and frame thickness, as well as the heat sink and the chip island size were studied and analyzed. For the small size two-sided flat leadless (DFN) package device under reflow temperature conditions Stress and warping deformation distribution. The results show that the maximum thermal stress of the package is located at the frame, and the value of the chip and the plastic encapsulation (ie, the triangular area overflowed by the silver paste) decreases with the decrease of the thickness of the package. The overall The thermal stress distribution also extends along the center of the bonding interface of the chip, silver paste and the frame to the triangular area of the silver paste and gradually increases. For the thin DFN package, the thickness of the chip, the bottom of the heat sink and the size of the chip island are different for the overall package The influence of warping deformation is small; the thickness of the frame has a great influence on the overall warpage and equivalent stress of the package; by reducing the thickness of the package and reducing the thickness of the frame, the thermal stress of the package can be effectively reduced, And the overall warping deformation are below 1um.