To predict the lifetime of a power module based on a defined

This indicates a higher reliability of materials with increased

mission profile, lifetime models were developed for the standard

mechanical strength. In addition, high values for parameters such

packaging technologies. These models take the relative

as total elongation at break point to an increased robustness

temperature swing ΔT, the mean Tvjm, and maximum junction

against the plastic deformation.

temperatures Tvjmax as well as the duration of thermal stress

( ton) into account.

Moreover, strong changes in the material properties caused by temperature treatment, such as a reduction of mechanical

The novel joining technology. XT for PrimePACK power modules

strength due to significant changes in the microstructure should

has been introduced to meet the future requirements of higher

be avoided within the operation temperatures. And finally, the

reliability and temperature stability. Using copper wire bonds for

maximum operation temperature should be low in relation to the

the top-side interconnect and silver sintered die attach layers led

melting temperature of the respective material, so that damage

to a significant increase of lifetime. With the introduction of these

by material creeping is minimized.

new interconnect methods it was possible to increase the lifetime and temperature stability of power modules.

The majority of existing modules is characterized by standard joining technologies such as aluminum wire bonding and soft

Failure Mechanisms

In general, thermally induced mechanical stresses in a chip-to substrate or a wire bond interconnect are caused by a coefficient of thermal expansion( CTE) mismatch between the joint partners or by an inhomogeneous spatial temperature distribution during thermal cycling. Thus, the degradation and failure of the interconnects are defined by the properties of the interconnect materials themselves. The ability of a material or interconnection to withstand a given thermally induced stress is determined by several key properties. In general, a low plastic deformation during temperature cycling results in lower mechanical damage.

soldering. They suffer from low inherent mechanical strength and low melting temperatures resulting in a limited reliability at operation temperatures excceding 150 ° C. Figure 1 depicts the novel joining technology. XT used in the Prime-PACK module with

IGBT5.

One method to increase the reliability of the top-side interconnects is to replace aluminum by copper wire-bond material. Because of its much higher yield and tensile strength combined with a lower CTE, the amount of plastic deformation for a given temperature cycle is significantly reduced compared to aluminum.