Universal approach using a stress sensing system for IC packages (Infineon and Sensitec)
The internal stresses within microelectronic packages are influenced by package design, materials used, assembly processes, and environmental aging effects. By understanding the local stresses and their variations within a package, it is possible to employ FEM simulations to optimize device design and predict reliability. In the iRel40 project, stress sensing dies are used to measure stress in IC packages of different geometries, materials, and assembly technologies or even In-Situ during reliability experiments. By improving and standardizing the measurement process with SMC (stress measurement chip), it ensures uniformity and reliability in measuring and analyzing the internal stresses within the packages for different applications.
Sensitec and Infineon utilized the stress measurement chip in different packages to address distinct concerns. Fraunhofer ENAS standardized the utilization and post-processing techniques for the SMC. In the case of the SO16 test vehicle developed by Sensitec, the investigation pertains to stress variations during the manufacturing process. Conversely, the TO263 test vehicle by Infineon emphasizes stress development during accelerated reliability tests.
A universal approach was developed at FhG ENAS to enhance SMC efficiency. It utilizes a bus system with a standardized interface for data acquisition and processing. Alongside hardware development, a new evaluation software was introduced to handle larger data volumes, facilitate user-friendly post-processing, and enable comparison of measured data. The software allows direct loading of raw data into the analysis tool and incorporates additional features like temperature calibration, peak extraction, time interpolation, and various types of plots like shown in figure 1.
Fig 1: TO263-7-3 test vehicle with Stress Measurement Chip SMC (source: Infineon). Surface plot Difference stress on SMC surface measured In-Situ during temperature loading and evaluated with ‘SMC-Analyzer’ from Fraunhofer ENAS
The standardized interface facilitates seamless integration of the system into various applications, allowing for easy adaptation. Furthermore, the improved post-processing capabilities create additional opportunities for leveraging the SMC measuring technique especially in combination with finite element analysis (FEA) or machine learning techniques.
This standardized approach enables accurate stress evaluation, which can be used for various purposes such as device optimization, reliability prediction, and performance enhancement. This integration enhances virtual prototyping capabilities and contributes to the improved reliability of new products.