Elecrically Conductive Adhesive Contacts Characterised by the 1/F Noise Behaviour

Today there is growing interest in using electrically conductive adhesives not only for interconnections between liquid crystal displays and printed circuit boards but also in contacts conducting higher currents such as flip-chip and rigid-flexible interconnections, for example in automotive applications. 1/f noise measurements are known as a diagnostic tool to investigate the quality of contacts, the lifetime of chip metallisations and the reliability of semiconductor devices. Resistance fluctuations (which mean noise) are induced by electron mobility fluctuations. In current constrictions, e. g. in a point contact, the noise amplitude is increased in a characteristic manner. This effect allows the characterisation of the point contact behaviour, i. e. the number and size of conducting spots. In this study noise measurements are used to detect the quality of a conductive adhesive contact before and during current and temperature shock damaging for the first time. Additionally the question of current induced electromigration in conductive adhesives is treated. Due to the results substrate plasma pre-treatment is a possibility to improve the adhesive contact quality. Furthermore, electrically conductive adhesive contacts are able to carry higher currents compared to today's standard applications. A technology to prepare anisotropically conductive interconnections with only one conducting particle per contact to separate different failure mechanisms and to realise the noise measurements is presented.