Degradation studies of epoxy coatings on printed circuit boards after pressure cooker test

Abstract

The present work focuses on the investigation of the degradation of screenprinted epoxy coatings on printed circuit boards under multiple corrosion loads realized by the pressure cooker test (PCT). Since methods like the common mechanical shear strength tests are destructive and limited in information, the authors' approach used electrochemical impedance spectroscopy to study the change of their electrochemical behavior and the state of degradation. Complementarily, the Fourier-transformed infrared spectroscopy was used to investigate the possible molecular change of the polymer due to the exposition. The experiments were carried out after different times of load. It could be shown that the complex conditions of the PCT initiate a controversial mechanism. The harsh corrosion load already results in a degradation of the polymer after 8 h but simultaneously the enhanced test temperature leads to ongoing curing processes consuming the remaining parts of resin and curing agents. As a result, the degradation kinetic seems to be delayed and after the test time of 96 h, the epoxy is less degraded than it was expected based on the results after a shorter time exposition.degradation, EIS, epoxy polymer, FTIR, pressure cooker test | INTRODUCTIONEpoxy-based polymers play an important role in electronic packaging, the multifarious material act, for example, as thermomold systems, attachment materials, or adhesives. Prime functions of the polymers are mechanical stabilization, insulation, joining, and corrosion protection of electronic components and bonds. [1][2][3][4][5] The reliability of electronic components depends among others, essentially on the degradation, the adhesion strength on polymer/