The Development Of Assembly Technology For Lead-Free Low Temperature Solder

Fujitsu introduced new assembly technology for lead-free low temperature solder in the world's fastest Super Computer and the New models of Global Server. A Step-soldering process using two types of lead-free solders is introduced. Over 10,000 bumps with 153um pitches flip-chip solder bumping, and up to 6,000 I/Os surface mount PGA joint for large-size MCMs are used. These Lead-free solders have excellent characteristics in thermal fatigue life, and have lower-Alpha particles. This system improves 10 times of solder joint reliability and reduced the defect rate cased by Alpha particles. This paper describes the assembly technology of low temperature solder. This is one of a "Green" technology for the new century which is compatible to high density product design and low cost manufacturing under the concept of "Eco-Design".