TABLE OF CONTENTS As discussed in Chaps. 1 and 6, environmentally benign electronics manufacturing, especially in Japan and the European Union, wants to be lead-free. Today, the most likely solder candidate is the Sn-Ag-Cu family, with a melting point temperature higher than 213 C. Thus, the maximum reflow temperature of the lead-free solder tends to rise from 220 to 260 C or even higher. This trend leads to serious problems on current die attach materials for molded-plastic integrated circuit (IC) packages. In this chapter, a couple of new die attach films developed by Hitachi for a lead-free soldering environment are presented.
For photonic and fiber-optic devices and packaging, lead-free solders [e.g., indium (In) and tin-indium (Sn-In)] used as joining materials have become ever more popular due to their ductility. Since flux and high-temperature solder reflow are not compatible with the optoelectronics packages, low-temperature, fluxless bonding techniques are therefore very desirable. In this chapter, the low-temperature fluxless bonding technique using In-Sn lead-free solder, developed by the University of California-Irvine, is discussed.
Silver pastes have been widely used for die attach materials for more than 40 years. However, due to lead-free soldering, most of the current silver pastes will crack and delaminate the package (as shown in Fig.7.1) during the higher-temperature reflow profile.1 9 As discussed in Chap. 6, the popcorn phenomenon has been under control through various formulation changes in epoxy molding compounds to reduce the amount of moisture absorption. However, die attach materials for lead-free soldering...
