公开(公告)号：PL374701A1

公开(公告)日：2005-10-31

申请号：PL37470103

申请日：2003-09-12

Applicant: IBM

Inventor： INTERRANTE MARIO ,  FAROOQ MUKTA G ,  SABLINSKI WILLIAM EDWARD

IPC: B23K1/00 ,  B23K35/14 ,  B23K35/26 ,  B23K101/40 ,  B23K101/42 ,  C22C13/00 ,  H05K3/34 ,  B23K31/02

Abstract: A lead free solder hierarchy for use in the second level solder connection of electronic components such as joining an electronic module to a circuit board. An off-eutectic solder concentration of SnCu or SnAg is used for the module side connection. This off-eutectic solder contains sufficient intermetallics to provide the module side connection with a robust second level assembly and rework process. The off-eutectic composition provides an inter-metallic phase structure in the module side fillet during assembly. The inter-metallic phase structure eliminates problems of tilt and collapse during second level assembly and aids in rework by providing a more cohesive joint allowing removal of the columns from the board without simultaneous removal from the module.