STUDYING THE EFFECT OF THALLIUM ON FORMING INTERMETALLIC COMPOUNDS IN AL-AU SYSTEM

Welded joints of aluminum conductors with a gold substrate are the most common in the production of various types of semiconductor devices. During testing and operation, intermetallic compounds may form in the joint area, which cause embrittlement and increase electrical resistance. This study objective is to investigate the effect of thallium impurity element, which is initially present in the gold coating produced by the galvanic method, or which has diffused from the substrate during testing or operation of radio electronic devices, on the degradation and disruption of the welded joint of gold coating with aluminum or aluminum alloy wire. The paper examines the complex effect of thallium impurity element on the thermodynamic and kinetic parameters of forming intermetallic phases in binary aluminum gold system. The relevance of the paper is in the critical role of Al Au compounds in microelectronics, where their reliability determines the operational characteristics of integrated circuits and semiconductor devices. Studies of Al Au compounds were carried out using scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). Based on the obtained results, key mechanisms of the effect of thallium impurities on diffusion processes and phase formation in Al Au system have been identified. It is shown that grain boundary diffusion and associated Kirkendall effect play a decisive role in degradation of Al Au compounds.