Development of Indium bump bonding for the ATLAS Insertable B-Layer (IBL)

About half of the ATLAS pixel modules have been assembled with the Selex indium bump bonding process. The requirements of the ATLAS Insertable B-Layer (IBL) detector ask for larger and thinner chips, two critical parameters for bonding processes. We report on the research and development carried on with Selex to produce modules with 100 mu m thick and 18.8 x 20.2 mm(2) area read out chips bonded with indium bumps.