Page 13 - Chip Scale Review_May June_2023-digital

Insertion loss comparison of the test vehicles is shown in
Figure 6. At 1GHz, insertion losses of MCM rtMLF (shown
by two solid lines) are lower than those of two single QFN
packages, which are shown by dotted lines. In conclusion,
the electrical performance of MCM rtMLF is better than two
single QFN packages.
Thermal dissipation performance. Usually, most of the heat
generated from the die is dissipated through the board [10]. A
thermal simulation was done to evaluate and compare thermal
performance for MCM rtMLF and MCM two-layer CSP
structures at different power levels. Figure 7 shows schematics
of the thermal simulation test vehicles. The schematics of
the simulation structures were shown in Figure 7a-d. In this
simulation, the package outline of the thermal simulation
structure was the same except for the die pad structure. For the
MCM rtMLF, exposed pads for heat dissipation were composed
of thick Cu alloy (Figure 7b). However, those of the MCM two-
layer CSP packages were composed of thermal vias (without
via fill, and with via fill) as shown in Figure 7c-d. The thermal Table 4: Results of thermal simulation.
simulation followed the JEDEC (JESD 51-2A) set up for a still-
air environment (Figure 7e). Figure 8 shows the temperature distribution on the package
Table 4 summarized the result of thermal simulation surface when the power per die is 1W. The temperature of
comparison between MCM rtMLF and MCM two-layer dice used in MCM two-layer CSP packages is about 10%
CSP structures. Theta JA (θ JA ), the thermal resistance, is a higher than that of the MCM rtMLF package. Consequently,
parameter for showing heat dissipation performance. Based the MCM rtMLF package shows higher heat dissipation
on the thermal simulation result, the θ JA of MCM two-layer performance than that of MCM two-layer CSP packages.
CSP packages is about 20% higher than that of the MCM
rtMLF package for each value of power applied to the die.

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