In order to enhance the reliability of a flip chip on organic board package,underfill is usually used to redistribute the thermomechanical stress created by the coefficient of thermal expasion(CTE)mismach between the silicon chip and organic substrate.However,the conventional underfill relies on the capilary flow of the underfill resin and has many disadvantages.In order to overcome these disadvantages,many variations have invented to improve the flip chip underfill process.