Page 19 - ChipScale_Jul-Aug_2020-Digital

thermal and interference, the packaging
is the main tool to handle such issues.
The latest advance in this field is
produced for Broadcom (formerly
Avago). As shown in Figure 3, a new
type of double-side BGA packaging
technology has emerged from Amkor,
which produces a very cost-effective,
small form factor and high-performance
component offering full compatibility
on the mid/high 4G frequency band.
Several innovations have led to the
kind of high-end packaging discussed
above. The first and most well-known
Figure 2: Murata vs. Skyworks: module opened view. SOURCES: [2,3]
LGA is the most common packaging
technology for RF. In this structure, the
passive or active components are always
with the lowest interconnection to the
supporting substrate (printed circuit
board [PCB], ceramic, etc.). Also, the
capping (molding, metal lid, etc.) could
be different depending on the thermal
budget of the device. On the module
side, the most advanced LGA serves
the single band in 4G implementation,
low-, mid- or high-band. Depending on
the supplier, different versions of LGA
technology could apply. If we consider
the low-band power amplifier module
integrated duplexer (LB-PAMiD), we
observe, for example, the two different Figure 3: Broadcom opening and component cost breakdown. SOURCE: [4]
SiP architectures using LGA from [2,3]. We could say that for these two technology is the conformal shielding
Murata and Skyworks, as shown in devices, the main influence on the cost that isolates the internal structure. The
Figure 2. came from the LTCC substrate. second is the compartmental shielding.
The two components noted above Today, however, LGA packaging Several assembly players have developed
have the same purpose. One is built has become less interesting for high- a process to realize such functionality.
on a ceramic substrate – a 10-layer end suppliers facing the rise of BGA The most popular method is with a hole
low-temperature co-fired ceramic packaging technology. As the industry is realized by laser drilling and filled with
(LTCC) – and the other on a 6-layer looking for a way to integrate 5G along solder paste. This new development
PCB substrate. Also, the number of with high-performance 4G, packaging allows the evolution of the technique
dies and the packaging are not exactly has to evolve in order to provide a to use wire bonding connected to the
the same for both. Murata chose to solution to reduce the form factor while conformal shielding either at the top, or
integrate a plurality of filters with keeping the relatively high-performance at the sides of the package.
a coupler and is using conformal level. A new module — low-noise power Amkor has also proposed some wire
shielding to protect the component from amplifier module integrated duplexer fences that directly connect the conformal
electromagnetic interference (EMI). (L-PAMiD) — has been seen recently shielding at the top of the package to
Skyworks, however, is more traditional, featuring mid-/high-band compatibility, the PCB substrate at the bottom. The
yet more innovative in terms of filtering and even a full-band 4G diversity third and final technology is the double-
technology. Only four surface acoustic module (SKY53735) has come about. side molding, which is a way to mount a
wave (SAW) filters are integrated into For the full-band 4G diversity module, component die at each side of the PCB
the Skyworks packaging along with it’s the technology (silicon on insulator substrate. On one side the dies are over
several bare dies connected to the PCB [SOI] and SAW filter) that enables the molded, and on the other side the dies are
substrate with gold wire bonding. Both innovation. For the mid-/high-band flip-chipped using thermocompression
packages have roughly the same area, L-PAMiD, the packaging is the key bonding with an underfill. By doing
whereas Skyworks’s PAMiD has a cost enabler for such high integration. This so, the bottom dies are isolated from
that is 49% lower than Murata’s. As has come with new challenges, such as the internal components while the PCB
usual, we estimate that almost 40% internal isolation, external isolation, and substrate required for the devices is
of the component cost came from the high-sensitivity component isolation. drastically reduced [4]. This integration
packaging, including the substrate cost In fact, when the major concerns are

17
Chip Scale Review July • August • 2020 [ChipScaleReview.com] 17