Effect of Physical Properties of Al–Si Electrode Films on the Deformation Behaviors and the Strength of Thick Al Wire Bonds during Thermal Cycle Test

Abstract

The deformation behaviors of Al-Si films and the strength change of Al wire bonds on Al-Si films during heating and cooling cycles have been investigated as a function of substrate temperature of the sputtering process; the purpose was to clarify reliability of both Al wire bonds and Al-Si films for use in insulated gate bipolar transistor (IGBT) modules. The extent of deformation in Al-Si films sputtered at 593 K during heating and cooling cycles was the smallest among films sputtered at room temperature (RT), 473 K, and 593 K. The strength of Al wire bonds on Al-Si films sputtered at the three temperatures was the highest for Al-Si films sputtered at 593 K. The reliability of Al wire bonds on Al-Si films formed at 593 K was about two times higher than the bond reliability on Al-Si films formed at RT and 473 K.

Reliability Enhancement of Thick Al–Cu Wire Bonds in IGBT Modules Using Al₂Cu Precipitates

“…35) As modules are composed of different materials with different thermal expansion coefficients, thermal stresses are induced at solder and wire bond joints. 1,4,5) The reliability enhancement of Al wire bonds is especially crucial to raise the reliability of IGBT modules at high temperatures because breaks in the Al wire itself can occur 1,68) through crack propagation along the small grain boundaries near the bonding interface due to tensile thermal stress generated during the operating cooling process 25) in the modules as schematically shown in Fig. 2.…”

Effect of Texture and Grain Size on the Deformation Behavior of Sputtered Thick Al-Si Films during Cyclic Heating and Cooling

“…They also show that bonding strength depends on the film quality and increases with decrease of Al film hardness. 3) On the other hand, it is also important to understand how the thick Al-1 mass% Si electrode films on the IGBT chip behave during heating and cooling cycles from the view point of reliability.…”