Fabrication of Micro Bump Using Electroless Plating

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Recently, the formation of microelectrode on the IC chip and the high density wiring board have become important. First, a microbump formation on the aluminum electrode using the electroless nickel plating was investigated. The micro nickel bumps of 20 mum wide and 15 mum high were formed by applying the nickel displacement process instead of the zincate process on the aluminum. It is important to control the behavior of the early stage of deposition reaction in the bump formation. The flat bumps were formed on the electrode by activating with the dimethyl amine borane (DMAB) solution in place of the nickel displacement solution. We examined the plating of the high density wiring as the next research that is required to IC mounting. Generally, the palladium catalyst has been used as the pretreatment to initiate the electroless nickel plating on copper. However, the extraneous deposition did not occured using the mixed solution of DMAB and nickel instead of the palladium catalyst solution. The electroless nickel films can be obtained on the copper substrate adding DMAB into the electroless nickel plating bath. Furthermore, the selective nickel deposition was formed by the control of the oxidation of reducing agent and early stage of electroless nickel plating.