Solder Flip Chip
Flip Chip Assembly Contents
Solder bumped flip chip has been in use at IBM since the 1960s. The IBM solder bumping process, termed C4, utilizes a high melting point solder which, if used on a low tg board such as FR-4, cannot be reflowed. However, the bumps can be utilized as standoffs, and joined to a thin layer of eutectic solder that is applied to the surface of the pads on the interconnecting substrate. The other option is to form eutectic bumps to the die and reflow directly onto the prepared pads of the interconnecting substrate. This method of flip chip mounting is directly compatible with surface mount processes. Figure 5 shows the process flow for a eutectic solder flip chip line.
Figure 5: Process flow for mounting solder flip chip devices. (Courtesy of National Semiconductor)