Page 20 - Chip Scale Review_November December_2021-digital

A new, higher density QFP

By Chu-Chung (Stephen) Lee, Yao Jinzhong, Glenn G. Daves [NXP Semiconductors N.V.]
This technical article (part 2) is a continuation of the Emerging Technologies column entitled, “A new, higher density QFP”
in the September • October 2021 issue of Chip Scale Review.
M axQFP (Figure 1) is a

new high-density quad
f lat pack (QFP) that
combines both gull-wing and J-leads
in an over-molded package body. The
outer row of leads are gull-wing (GW)
leads, with the J-leads located inward
towards the center of the package
and interstitially between two GW
leads. The external lead pitch between
adjacent leads of the same type (e.g.,
J-leads) is 0.65mm and that between
adjacent leads of different types (i.e.,
bet ween the J- and GW-leads) is
0.325mm. As an example, on the 100-
lead MaxQFP (10x10mm body size),
each side of the package has 13 GW-
leads and 12 J-leads resulting in a total
of 25 leads per side and 100 leads for
the package. One notable feature of
MaxQFP is that these two rows of leads
are not located on the same plane during
molding—i.e., there is no dam bar on
the lead frame strip. This design allows
the leads to be vertically displaced from
each other even at the position of the
molded body. The resulting separation Figure 1: a): (left) MaxQFP packages combine both QFP gull-wing and PLCC J-leads; b) (right) A top view of
reduces the chances of shorting between the 172-lead MaxQFP package is pictured, showing outer gull-wing and inner J-leads, positioned interstitially; c)
leads and effectively enables almost the (left) Bottom view of the 172-lead MaxQFP package; and d) (right) Close-up view of the same package.
entire perimeter of the package to be
used for I/O.
Two MaxQFP body sizes have been
developed to date: a 172-lead (16x16mm
body size) version and a 100-lead version.
Together, these are able to replace five
JEDEC-compliant QFPs with lead counts
of: 64, 80, 100, 144 and 176 as illustrated
in Figure 2.
Fo r h ig h - p owe r a p pl ic a t io n s ,
MaxQFP_EP (exposed pad) has also been
developed as shown in Figure 3. It is
similar to the QFP_EP, where a portion of
the die flag is exposed, enabling it to be
soldered to a printed circuit board (PCB)
resulting in short thermal connection
between the PCB, package, and die. Its
thermal performance is significantly
better than can be achieved by a similar Figure 2: MaxQFP simplifies package portfolios. The 100-lead MaxQFP (10x10mm) replaces the 64-, 80-, and
100-lead QFPs, while the 172-lead MaxQFP (16x16mm) can replace both the 144- and 176-lead QFP.

18 Chip Scale Review November • December • 2021 [ChipScaleReview.com]
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