Field failure due to creep corrosion on components with palladium pre-plated leadframes Ping Zhao, Michael Pecht * CALCE Electronic Products and Systems Center, University of Maryland, Building 088, Room 0122, College Park, MD 20742, USA Received 14 November 2002; received in revised form 3 February 2003 Abstract Creep corrosion is a mass-transport process during which solid corrosion products migrate over a surface. It has been identified as a failure mechanism responsible for the malfunction of electrical contacts and connectors. For components with noble metal pre-plated leadframes, creep corrosion is a potential reliability risk for long-term field applications. This paper explains the source, process and possible products of creep corrosion on integrated circuit (IC) packages. The operating environment for telecom equipment is introduced as an example demonstrating the corrosive environ- ments for electronic components. Field failure due to creep corrosion on plastic encapsulated components with pal- ladium pre-plated leadframes is presented and analyzed. Similar phenomenon has been reproduced in an accelerated manner using mixed flowing gas (MFG) testing in the laboratory. Ó 2003 Elsevier Science Ltd. All rights reserved. 1. Creep corrosion and palladium pre-plated leadframe In leadframe micro-electronic packages, it is necessary to protect the exposed leadframe from oxidation and corrosion so the part can be soldered with high quality onto a printed wiring board (PWB). In addition, com- ponent lead finishing improves solder joint reliability, and enhances the electrical contact by reducing oxides, and provides an acceptable cosmetic appearance [1,2,9]. There are two categories of leadframe finishing methods. One is the post-encapsulation process with tin– lead or other tin-based alloys, which is realized by hot dipping or electroplating. The other method is the pre- encapsulation process with some kind of precious metal, which is known as the pre-plated leadframe process. The possibility of palladium as a plating material in electronic products was first proposed in the mid 1970Õs [3]. An electrolytic plating of pure palladium over nickel was found to provide corrosion resistance and wear properties similar to that of hard gold [4]. The success of palladium-plated contacts and connectors eventually led to its consideration for replacement of solder finishing of leadframes in the semiconductor industry. Noble metal pre-plated leadframes have been used in electronic packaging since 1989 [5]. Palladium plated leadframes in semiconductor devices have many advantages over conventional solder-coated leadframes [5–7]. First, the introduction of the palla- dium pre-plated leadframe totally eliminates the solder coating process in manufacturing, shortens cycle time, and reduces the overall production costs. Second, since lead in solder dipping and cyanide in silver spot plating are removed from the process, pre-plating eliminates the health and safety concerns associated with exposure to these hazardous materials in the work place and in manufactured goods, and there are also no associated environmental waste disposal issues to these hazardous materials. Third, the performance and reliability can be improved due to higher IC planarity and lower solder bridging possibility. In the standard packaging process for plastic com- ponents, the ‘‘trim and form’’ process after encapsula- tion can expose the leadframe material on the leads. Microelectronics Reliability 43 (2003) 775–783 www.elsevier.com/locate/microrel * Corresponding author. Tel.: +301-405-5316; fax: +301-314- 9269. E-mail address: pecht@calce.umd.edu (M. Pecht). 0026-2714/03/$ - see front matter Ó 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0026-2714(03)00064-7