Page 43 - Chip Scale Review_May June_2021-digital

of parts to be taken from a substrate;
2) the production volume; and 3)
production leveling. In particular,
production leveling can avoid material
wastes and reduce variable costs
of production. For this production
leveling, it is necessary to possess
FOWLP technology complying with
customers’ requests and to have a
sufficient product portfolio.
To comply with customers’ requests,
our FOWLP technology offers “resin
body type” and “silicon body type”
platfor ms. The silicon body type
FOWLP utilizes the rigidity of silicon,
which enables ultra-small and ultra-
thin dies to be mounted on a small
and thin package. The silicon body
type FOWLP has a three-dimensional
structure by silicon processing—i.e.,
concave pockets are formed on the
silicon substrate by lithography and
wet etching. This package is achieved
without debonding technology by
forming the Cu interconnect, internal
terminals, and external terminals on
the three-dimensional structure using
electroplating. Then, resin sealing and
resin grinding are done. Because of
the three-dimensional structure, there
are challenges in pattern fabrication
tec h n o l o g i e s a s s o c i a te d w i t h
lithography, such as resist profiles
and a large depth of focus exposure.
It is important to select the right
equipment and optimize the design
rules to address these challenges.
By optimizing the design rules, we
have prevented abnor mal grow th
during electrolytic plating in terminal

Figure 2: Package structure on the silicon body
type FOWLP. Figure 3: Basic process flow for a silicon body type FOWLP.

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