DOUBLE SOLDER BUMPS ON SUBSTRATES FOR LOW TEMPERATURE FLIP CHIP BONDING

摘要

Multiple injections of molten solder are employed to form double solder bumps having outer layers that melt at lower temperatures than the inner portions thereof. During a flip chip assembly process, the reflow temperature is above the melting temperature of the outer layers and below the melting temperature of the inner portions of the solder bumps. As the inner portions of the solder bumps do not collapse during reflow, a flip chip assembly can be made at relatively low temperatures and have a high stand-off height. A structure having double solder bumps facilitates flip chip assembly.