Product verification and defect repair - status and considerations

Product verifications have become a cost-intensive and time-consuming aspect of modern electronics production, but with the onset of an ever-increasing miniaturisation, these aspects will become even more cumbersome. One may also go as far as to point out that certain precision assembly, such as within the biomedical sector, is legally bound to have 0 defects within production. Since miniaturisation and precision assembly will soon become a part of almost any product, the verifications phases of assembly need to be optimised in both functionality and cost. Another aspect relates to the stability and robustness of processes, a pre-requisite for flexibility. Furthermore, as the re-engineering cycle becomes ever more important, all information gathered within the ongoing process becomes vital. In view of these points, product, or process verification may be assumed to be an important and integral part of precision assembly. In this paper, product verification is defined as the process of determining whether or not the products, at a given phase in the life-cycle, fulfil the established specifications. Since the product is given its final form and function in the assembly, the product verification normally takes place somewhere in the assembly line which is the focus for this paper.

Microstructure characterization of 316L deformed at high strain rates using EBSD

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s− 1 at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain.