Actively cooled electromagnetic actuators, as used in for example the EUV lithography machines from ASML, are prone to failure by delamination of interfaces associated with the polymer-based potting material that serves both for heat conduction, load transfer and mechanical integrity of the actuator. The mechanisms of failure due to thermo-mechanical loads and the role of the microstructure of the potting material in these failure mechanisms are currently not well understood, which hampers the development of electromagnetic actuators with an economically viable and reliable lifetime.
The objective of this project is to develop a fundamental understanding of the mechanical characteristics of the heterogeneous potting material over the actuator operating temperature range, which consists of an epoxy matrix filled with boron nitride platelets and a copper chrome oxide. As a starting point, a basic micromechanical modelling framework has already been developed for this.
During the course of the project, this numerical framework will be developed further. Among other things, experimental data for both the epoxy matrix and potting material will be used to fit and validate the numerical micromechanical model. In addition, the effects of adhesion between the boron nitride platelets and the epoxy matrix will be investigated, as well as variations in platelet size, shape, orientation and geometrical distribution. The copper chrome oxide will be accounted for via a homogenization step with the epoxy matrix material.
Figure 1: SEM image of the heterogeneous potting material and a schematic representation of an electromagnetic actuator cross-section.
