Modeling forSolder Self-Assembly ofMEMS Microstructure PoweredbySurface Tension

Duetothecharacteristics ofminiaturization of size andhighintegration offunctions andsoon,MEMS is taken ashigh-tech frontier of21St century. Theprogress of surface micromachining andbulkmicromachining promotes MEMS technology. But,theinherent defects ofsurface micromachining andbulkmicromachining hinderthe triumphant manufacture of complexthree-dimensional. Surface tension powered MEMS self-assembly candeal with this "bottle neck"successfully. Self-assembly technology is basedontheprinciple ofsurface energy minimization of moltenmaterial. Duringtheprocess ofminimizing the surface energy, surface tension maypull thehorizontal hinge plate uptosomeangle andthenachieve equilibrium state. Inthis paper, finite element method isemployed, anew dynamic MEMS self-assembly modelisdeveloped by SURFACE EVOLVER. Themodelinthispapercan dynamically simulate theanglechange ofmicrostructure during theprocess ofevolvement. Themaincharacteristics ofthis modelare: (1)Itiseasier toobtain thefinal angle than static modelforacertain volumeofsolder paste. (2)Under thecondition ofnochange ofparameters, suchassolder paste volume, padsize andpadfigure, thefinal angle maybe moreprecise compared withtheresults ofprevious researches. Itcanprovide guarantee toprecisely control the final assembly angle ofhinge plate. Designs ofexperiments areplanned andthesolder geometry shapes areestimated fromthis dynamic model, andthearea, energy andforces are derived correspondingly. Further, therelationship between thesolder parameters andtheangle, energy andforces are conducted fromtheaboveresults. Fromtheexperiments we canconclude thatpadsizeandsolder volumearecritical parameters whichinfluence thefinal assembly angle. The experimental results canbeusedtoguide thedesign ofthe self-assembly for3-DMEMS microstructures.