Electrochemical migration in electronics: effect of contamination and bias conditions

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Abstract

A number of reliability issues are caused by mechanisms different from the conventional corrosion due to specific aspects of the printed circuit board assembly (PCBA). The size of the components and the distance between them, combinations of dissimilar metals, voltage and temperature gradients – all together influence susceptibility of electronic PCBA to corrosion. When electronics is operating under humid conditions, the cleanliness of the PCBA becomes essential, since corrosion related failures in electronics can occur at extremely low levels of moisture and contamination. A synergetic effect of the aspects mentioned above makes it challenging to predict the lifetime of electronic device.
The aim of this work is to investigate corrosion influencing factors, which at a later stage improve capabilities of predicting the functioning and herewith reliability of electronics under certain climate, contamination, and bias conditions. In this work, the effect of ionic contamination such as sodium chloride and weak organic acids, as they are used in no-clean fluxes, was studied under water droplet and humidity elevation at room temperature conditions. The effect of pH and tin ion dissolution on the probability for electrochemical migration was studied on surface mount chip components under water droplet conditions, as a function of applied voltage (DC and square wave unipolar/ bipolar). The leakage current and impedance was studied on the surface insulation resistance patterns precontaminated with sodium chloride and weak organic acids exposed to accelerated humidity conditions.
The results from pH and tin ion dissolution study under water droplet condition showed electrochemical migration dependence on duty cycle and period, which was dependent on the amount of sodium chloride in the water droplet. Overall the tendency of increase in time to electrochemical migration with decrease of duty cycle was observed. The testing of the printed circuit boards under humid conditions showed a correlation between the hygroscopic property of contaminants and leakage current measured on the boards. A significant increase of leakage current was observed at humidity levels close to the critical or deliquescence of the contaminants.
Original languageEnglish
Publication date2014
Publication statusPublished - 2014
EventEuropean Corrosion Congress - Palazzo dei Congressi of Pisa, Pisa, Italy
Duration: 8 Sep 201412 Sep 2014
http://www.eurocorr2014.org/scope.htm

Conference

ConferenceEuropean Corrosion Congress
LocationPalazzo dei Congressi of Pisa
CountryItaly
CityPisa
Period08/09/201412/09/2014
Internet address

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