1. private communication, K. Taira, Kyosemi co[AU1]
2. N. Tanaka, Nikkei Microdevices, 2006, March, 25–45 [in Japanese]
3. M.B. Prince, 14th Annual Proceedings of Power Sources Conference, 26 (1960)
4. W.R. McKee, IEEE Trans. Components Hybrids Manuf. Technol. 5, 336 (1982)
5. Ball Semiconductor Technology conference, San Francisco, CA, 1998 (It can be purchased at website.)