Evaluation of the metal coating porosity of gold finger for secure digital memory card by way of flower of sulfur test methodology

Abstract

With the more and more severe air pollution, the corrosion phenomenon will also directly or indirectly influence the reliability of electronics. In order to ensure the anti-corrosion reliability requirement is enough even if the electronics were used in harsh environment. Therefore, it is necessary to evaluate the anti-corrosion capacity through accelerated corrosion test methodology. Print Circuit Board (PCB) pad design and Print Circuit Board Assembly (PCBA) material were often selected to research the corrosion phenomenon due to the in-field failure with creep corrosion. Besides, passive component and conformal coating have been also mentioned in several literatures in recent years. In general, the conformal coating seems a good system level solution which can protect the board and component to prevent the corrosion occurrence. But the solution is not suitable for gold finger and connector due to the electrical connection. To consider the high potential corrosion risks in gold finger and connector areas. Therefore, 30 um gold plating was often adopted to satisfy the anti-corrosion requirement in harsh environment in the industry. However, it is necessary to evaluate the porosity for metal coating quality even if the same thickness of gold plating. In this paper, the Flower of Sulfur (FoS) test was adopted to evaluate the metal coating porosity of gold finger for Secure Digital (SD) memory card. SD memory card is widely used in the various consumer electronic devices and also has become a widespread means of storing several gigabytes of data in a small size, including digital cameras, camcorders, and video game consoles, mobile phones and so on. In this paper, the gold finger area was selected to research the corrosion phenomenon and also followed FoS test with ASTM B809 standard. Several analytical methods were carried out in this work, including, Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX) and Coulometric Reduction (CR). Finally, we would like to verify the metal coating porosity of gold finger and also ensure that anti-corrosion capacity for various ready-made SD memory card.