A Review of Electrically Conductive Adhesive Technology for Use in Surface-Mount Microelectronics

Interest in alternatives to lead solders continues to increase due to several initiatives addressing the reduction of lead usage and subsequent exposure to the environment. Alternative materials can be categorized into two main groups: electrically conductive adhesives (polymers) and non-lead solders. Over the past ten years, many non-leaded solders have been developed and introduced to the electronics industry. Despite some success regarding processability, several issues still exist regarding use of these materials as “drop-in” replacements for traditional leaded solders, e.g. eutectic tin-lead. This paper provides an overview of the second alternate material group, i.e. electrically conductive adhesives. An attempt is made to compare characteristics of these materials to the tin-lead benchmark. A summary of key material properties is also included. Finally, a position is presented regarding the approaches taken in evaluating these materials as suitable substitutes for tin-lead eutectic solder. Focus is on applications in surface mount technology (SMT) interconnection since solder is the primary bonding medium for interconnection. In general, these materials are acceptable for most applications. Applications under harsh service and environmental conditions, however, would require evaluation on a case-by-case basis.