Reasons for using lead-free solders rather than isotropically conductive adhesives in mobile phone manufacturing

European Union directive Restrictions on Hazardous Substances (RoHS, 2002/95/EC) will ban the use of lead and certain other substances in electronic equipments on July 1^st 2006. The ban of lead has caused a switch to lead-free solders rather than to isotropically conductive adhesives (ICAs), even if the latter posses many valuable qualities. The reason from manufacturing perspective is the minimum amount of changes in equipments and processes. ICAs have also reliability concerns since they have less resistance against loads from damp heat and impact stresses than tin-lead or lead-free solders. However, the future phone or accessory functionalities may require the use of MEMS (Micro Electro Mechanical Sensors). With MEMS some ICA advantages over solders become important. These are the lower bonding temperature, lower modulus of elasticity and the elimination of the need to clean.