Enhanced Polymer Passivation Layer for Wafer Level Chip Scale ...

Figure 2.3 Cross section of a typical Polyimide-RDL WLCSP [28]
WLCSP combines the conventional chip scale package advantages of thinning,
miniaturizing, low mass packaged chips, and ease of handling with an efficient volume
production approach based upon batch packaging at the wafer level [30]. Table 2.1 compares the
differences between traditional packaging and wafer level packaging [8].
Many companies around the world are developing or have begun providing devices
packaged in chip size fashion. Amkor, Fujitsu, Shell Case, Chip Scale, Oki, Unitive, Flip Chip
Technologies (FCT), Fraunhoffer Technical University, Tessera, and some other companies have
all shown diligence in the area [8]. Although all of these technologies result in packaged area
array chips, the technologies still differ, sometimes significantly, in processing steps such as
redistribution technologies, encapsulated technologies, and flex tape technologies. Table 2.2 lists
and compares the key process features for most of manufactures [6] while Figure 2.4 shows
some of their products such as (1). The Casio Wrist Camera with super CSP 48 developed by
Fuji, (2). The Ultra CSP by Flip chip International, (3). The National Semiconductor Micro-
SMD, (4). The Ericsson Bluetooth, and (5). The Tessera Wafer-Level Camera (WLC)
technologies.
17