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Figure 6: Near-field conformal shielding performance measurements from 100MHz to 6GHz.

Materials designers and original equipment Another design factor that can improve
Similar to shielding, material selection manufacturer (OEM) system designers. antenna performance is to optimize the
also has a significant impact on AiP Design considerations for 5G substrates substrate stack-up (see Figure 7). Direct
design and performance—a variety of must account for different package- connection with receive/transmit (RX/
materials provide design options to meet level signal losses including: conductor, TX) signals reduces signal mismatches
different performance levels. In addition dielectric loss, leakage and radiation that can negatively impact the receiver
to materials for mmWave shielding, an losses. Conductor losses must address signal sensitivity and increase power
antenna substrate can have: plating, skin depth, surface roughness, consumption at the transmitter.
• Asymmetrical stack-up; and via (str uct ure,
• <3.3 dielect r ic constant (Dk) pitch and placement).
materials; Key elements affecting
• <0.005 dissipation factor (Df ) dielectric loss include
materials; the substrate materials’
• Ra >300nm (Cu trace surface dissipation factor and
roughness); and dielectric constant. The
• Low Dk/Df solder resist. substrate materials’
thick ness stack-up
Wafer-level processing and LDFO also has a direct effect
packages include: on signal integrity
• Low Dk/Df passivation and mold/ (e.g., core, prepreg
electromagnetic compatibility (EMC); a n d s o l d e r m a s k
• Thick passivation development; thickness). The epoxy
• Mu lt i-l aye r R DL fo r T-l i n e / mold compound may
waveguide; and also come into play for
• Wafer-level magnetic shield. structures where the
mold compound is used
Advanced, high-frequency discrete as a dielectric. Leakage
antenna/transceiver applications employ losses can occur within Figure 7: Optimized substrate stack-up and RDL/via routing can improve
wafer-level package technologies, where the plane due to under- antenna performance by reducing signal mismatch.
the metal RDLs that form the antennas’ etched seed layers and
elements are high precision, repeatable, between substrate layers because of RDL Specific implementations of different
and easily tuned for the application. and via patterning defects. Radiation design aspects in a variety of packaging
Specific AiP platform implementations losses can occur because of: technologies for AiP include:
include: 1) Top layer assembly; 2) Double-
side assembly; 3) Double-side molded • Circuit configuration: stripline, • Body sizes up to 23.0mm with several
assembly; and 4) Double-side molded complainer and microstrip; form factor options;
assembly with exposed die. • Via stub (radiation and reflection); • Up to 14 substrate layers; and
Choosing the right package platform • I m p e d an c e t r an s i t i o n an d • Thin-film RDLs and dielectrics for
for a specific design typically involves discontinuities; and 77GHz and higher applications.
discussions between OSAT package • Spurious resonance frequency spectra.

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