LEAD-FREE SOLDER STRUCTURE AND METHOD FOR HIGH FATIGUE LIFE

摘要

A METHOD AND STRUCTURE FOR SOLDERABLY COUPLING AN ELECTRONIC MODULE (E.G.A CERAMIC OR PLASTIC BALL GRID ARRAY MODULE) TO A CIRCUIT BOARD.A LEAD-FREE SOLDER BALL IS SOLDERED TO THE MODULE WITHOUT USING A JOINING SOLDER TO EFFECTUATE THE SOLDERING.THE SOLDER BALL COMPRISES A TIN-ANTIMONY ALLOY THAT INCLUDES ABOUT 3TO ABOUT 15% ANTIMONY BY WEIGHT. THE SOLDER BALL IS SOLDERED TO THE CIRCUIT BOARD WITH A LEAD-FREE JOINER SOLDER. THE JOINER SOLDER COMPRISES A TIN-SILVER-COPPER ALLOY THAT INCLUDES BY WEIGHT ABOUT 95.5-96.0% TIN, ABOUT 3.5-4.0% SILVER, AND ABOUT 0.5-1.0% COPPER.THE RESULTANT SOLDER CONNECTION BETWEEN THE MODULE AND THE CIRCUIT BOARD HAS A FATIGUE LIFE OF AT LEAST ABOUT 90% OF A FATIGUE LIFE OF A REFERENCE STRUCTURE. THE REFERENCE STRUCTURE HAS A 90Pb/10Sn SOLDER BALL JOINED TO BOTH THE MODULE AND THE CIRCUIT CARD BY A 63Sn/37Pb JOINER SOLDER.(FIGURE 2)