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 .