Surface Tension-Powered Self-assembly Mechanism And Its Applications In Microelectronic Packaging

It is needed to reduce the size of electronic packaging with more, higher density inputs/outputs (I/Os), and even consist of hybrid micrometer or nano-meter components, because of the requirements of light-weight, small-size, low-cost, and high-performance increasing for electronic products. Using self-assembly in microelectronic packaging technology, huge advantage can be gained to satisfy the market requirements of sophisticated electronic devices.Surface adhesive forces including surface tension forces, electrostatic forces and van der waals forces etc, are overwhelming in the size domain of microstructures. Surface tension forces are widely used in self-assembly in two ways: reorientation of precisely located parts into three-dimensional (3-D) structures, and aggregation of randomly oriented parts. The former way also has two types: using the surface tension forces to push and pull the chip, using the surface tension forces for rotational self-assembly. The latter is closer to self-assembly of molecule.The flip-chip technology using self-aligning solder joints uses the reflow moulding to reshape solder for realizing the self-alignment of chip. The reliability of solder joints is analyzed, and a failure criteria is given out as well. An accurate compute method of surface tension forces has been developed based on the principle of surface energy minimization. The relationships between the surface tension force and the solder joint design parameters are analysed explicitly. Basing on the failure criteria and force computing method, a method has been developed to quantitatively predict the yield of solder flip-chip assembly yield. Yield was found in relation to the mean and the standard deviation of the solder volume distribution, the assembly warpage, and the chip size.The fluidic self-assembly system using the capillary forces is probed into in my thesie finally.A purely geometric model is built to calculate the difference in surface free energy. The difference in surface energy of any kind of binding sites is computed using digital image matching theory, and then the energy plot is emulated which can show the relationship between assembly configuration and energy configuration. An efficient method for predicting the outcome of the fluidic self-assembly is obtained by analyzing the global minimum and the local minima of the energy plot.The pre-assembly design, in terms of dimensions and materials used, can improve the final self-assembly accuracy. Two kinds of surface tension-powered self-assembly technologies have been discussed. The conclusion and modelling methods are very powerful and convenient tool to aid in the design of solder joints for various applications, and maybe be used in other advanced electrionic packaging technologies.