Papers by Author: L.J. Ernst

Abstract: Substrate transfer technology for SOI and non-SOI single-crystalline silicon wafers was demonstrated allowing for high-performance low-power RF applications. 3D deformable electronics could be realized by vertically thinning and laterally partitioning of the silicon substrate on sub-millimeter scale. By varying the partition dimensions and the geometry of connecting bridges, the level of acceptable deformations can be controlled. The targeted applications of this technology are wireless ID tags and sensor networks. The mechanical properties such as crack, interfacial delamination are critical to reach the flexible substrate. In this contribution, results of our work on mechanical reliability issues of poly- and single crystalline silicon on ultra-thin polyimide substrates are presented. To improve reliability, square and hexagonal segmentation with different size is applied to the silicon layer before it is transferred onto an ultra-thin polyimide substrate using wafer-to-wafer substrate transfer technique based on a temporary glass carrier. Generation of cracks within the silicon and dielectric layers is then studied under controlled bending and tensile loads. The formation of cracks is studied experimentally using specially for this purpose designed bending and tensile tools. Ultra-thin interfacial delamination are also focused in this work by experimental and FE simulation method. A new test setup is designed for mixed mode bending testing which has capacity to observation specimen and recording the crack length and crack opening by microscope. The critical energy release depended on mixed angle can be reach by combination experimental data with FEM simulation.

Abstract: Dyneema composite is used in lightweight armour applications, because of its high specific material properties such as strength and stiffness. In armour applications, Dyneema composite is used to protect people or vehicles from projectile impact. In order to be able to guarantee a certain protection level, an accurate prediction of fracture phenomena that are caused by projectile impact is required. Currently, fracture phenomena such as delamination and fibre fracture are not accurately described. This is because a good understanding of fracture phenomena in Dyneema composite lacks. Therefore, both Dyneema fibre and Dyneema composite are analysed by different (impact) experiments to gain more insight in both the fracture phenomena as well as in the material properties. Parallel to these experiments, a start is made with the development of a new material model in ABAQUS\Explicit using cohesive zone techniques that is able to predict the fracture phenomena due to projectile impact.

Abstract: Pattern shift is one of the main failures of micro-electronics. In this paper, the influence of plastic deformation values of micro-structures of IC packages on the pattern shift of metal lines is studied by maximum plastic strain theory using a certain 2D FEM model with different design parameters, “d”, “w”, “t_epo”, “t_Teos”, “t_glue” “sy_glue” and “sy_al”. For different critical process step, the final process temperature is acted as a representative parameter to analyze its impact. Furthermore, Response Surface Model (RSM) of plastic strains is established using any two design parameters. Results show that “w”, “t_epo”, “t_Teos”, “t_glue” “sy_glue” and “sy_al” will have different influence on pattern shifting while “d” have little impact.

Abstract: The passivation cracking of Micro-structures of IC packages is studied by maximum principal stress theory using a certain 2D FEM model with different design parameters, pitch of lines, width of line, thickness of epoxy, thickness of dielectric layer, thickness of glue, the glue material’s yielding stress and Aluminium yielding stress (following as “d”, “w”, “t_epo”, “t_Teos”, “t_glue” “sy_glue” and “sy_al” respectively). For different critical process steps, the final process temperature is acted as a representative parameter to analyze its impact. Furthermore, Response Surface Model (RSM) of principal stress is established using any two design parameters. Results show that “d”, “w”, “t_epo”, “sy_glue” and “sy_al” will have great influence on passivation cracking while “t_Teos” have a little impact.

Abstract: When studying 3D fatigue crack growth behaviors of materials, to determine the crack opening stress intensity factor ratio is the key issue. Elastic-plastic Fracture Mechanics theory and physical mechanism of cracks’ closure phenomena caused by plastic deformation are employed here. A model for determining the crack opening stress intensity factor ratio under tri-axial stress state is presented. The comparison of the present model with available data and models shows quite good agreement.

Abstract: Passivation crack is one of the main failures of micro-electronics. And the IC interconnect has a large varying range values comparing with its geometry size. In this paper, the influence of geometry values of micro-structures of IC packages on passivation cracking is studied by maximum principal stress theory using a certain 2D FEM model with different design geometry parameters, pitch of lines, width of line, thickness of epoxy, thickness of dielectric layer and the Aluminum yielding stress (following as “d”, “w”, “t_epo”, “t_Teos” and “sy_al” respectively). For different critical process step, here the final process temperature is acted as a representative parameter to analyze its impact. Furthermore, Response Surface Model (RSM) of principal stress is established using any two design parameters. Results show that width of line, thickness of dielectric layer and the Aluminium yielding stress will have great influence on passivation cracking while other parameters having little impact.