Intermittent electroless nickel deposition in a fine trench flip chip bump pad

An intermittent electroless nickel deposition process was examined which involved periodically removing and reinserting the silicon wafer in the deposition bath. This process results in electroless nickel deposits with a smooth surface appearance and uniform thickness within the bump opening. The intermittent deposition process also results in enhancement in deposition speed. The benefits of this process are ascribed to replenishment of the surface concentration and the breakdown of entrapped gas bubble in the trench area of bump pad.