Hans Walter

Learn More
The paper addresses the determination of the effects of time and temperature on strength and lifetime of structural polymer composites. For some time, this topic has already concerned the aerospace industry during their fatigue tests of light structures made of fiber reinforced polymer (FRP) under various loading modes. More recently, the issue has also(More)
Three different types of iron oxo-hydroxo colloids with well-defined sizes and chemistries have been synthesized by hydrolysis of Fe(III) in acidic and alkaline medium as well as by oxidative hydrolysis of Fe(U), resulting in solutions of &FeOOH (30 nm), a hexanuclear complex (HN, 2 nm), and a polynuclear oxidation product (OP, 3 nm). These colloids were(More)
Simple adhesion tests like the pull-out test or the button shear tests have been used in industry for decades. They offer a great potential for comparison of different molding compounds, encapsulants, or adhesives on different types of sub-strates with or without surface treatment. However, for theoretical prediction purposes, interface fracture mechanics(More)
Experimental and FEM studies have been undertaken in order to characterize the non-Fickian behavior of moisture absorption, temperature-dependent residual moisture content and hygroscopic swelling of epoxy molding compounds exposed to moist environments. Moisture absorption and desorption tests of two molding compounds and two IC packages using these(More)
Thermal fatigue of solder joints is investigated by means of the finite element method (FEM). During the usual thermal cycle regime with relatively slow temperature ramping rates, solder constitutive response is dominated by secondary creep. In the paper secondary creep laws are given for SnPb and SnAgCu solders, based on our own measurements and literature(More)
Interfacial adhesion between the Epoxy Molding Compound (EMC) and the copper-based leadframe is one of the major concerns in the qualification of plastic packages. Since the conventional shear testing methods used in industry do not consider the residual stresses in the shear samples, they are only used as a qualitative testing method for the EMC(More)
The properties of epoxy based materials alter, when exposed to humid environment and temperature. To better understand the failure mechanisms on microelectronic packaging we examine these epoxies (aromatic epoxy: l,3-Bis-(2,3-epoxypropyl)-benzene and amine hardener: 1,2-Diaminoethan ) under different initial conditions of temperature (300-400 K) &(More)
For high temperature interconnection sintered silver can be used, however, it induces new demands on the thermo-mechanical design. That issue requires knowledge on the thermo-mechanical reliability of silver sintered devices, the subject of this paper. Material characteristics of the sinter layers are needed for simulation, which are addressed in the first(More)
The time and temperature dependant creep deformation of solder alloys has to be studied to describe material characteristics and failure behaviour, in order to use it for lifetime evaluation by FE-simulations. It is often found in the literature that the material behaviour of eutectic SnPb solder is described considering only secondary creep. As this paper(More)