IDTechEx Discusses Which Substrate Tech Rules for 5G and 6G AiP

Antenna packaging methodologies have evolved significantly to counter the escalating signal attenuation in high-frequency communications like 5G mmWave and anticipated 6G networks.

Previously, antennas were positioned on PCBs; now, there's a shift towards integrating antennas directly onto the same package as the RF chip. Known as Antenna-in-Package (AiP), this advanced packaging technique capitalizes on the short wavelengths of mmWave applications, allowing for the creation of notably compact antennas seamlessly embedded within semiconductor packages. Unlike traditional discrete antennas assembled on PCBs, AiP integrates the antenna with the transceiver on a single chip, offering advantages such as improved antenna performance and substantially reduced package footprints.

While 6G research is progressing, the 5G mmWave market remains in its early stages, awaiting widespread adoption across various applications and user ecosystems. The advancement of Antenna-in-Package (AiP) technology is closely intertwined with the growth of both the 5G mmWave and future 6G markets. With AiP expected to be integral to all 5G mmWave-based stations and 5G-enabled devices such as smartphones, its ongoing development is pivotal.

In the development of Antenna-in-Package (AiP) technology for high-frequency communication devices, cost-effectiveness is paramount, aiming for a target price of $2 per 1x1 AiP module to enable widespread adoption. Achieving affordability involves overcoming a chicken-and-egg challenge where adoption must precede cost reduction through economies of scale. Utilizing cost-effective packaging materials and processes and ensuring miniaturization are crucial, especially for integration into consumer devices like smartphones. High performance is vital, necessitating the fabrication and integration of high-gain, broadband mmWave antenna arrays, alongside addressing electromagnetic compatibility (EMC) and optimizing signal integrity (SI) and power integrity (PI). Reliability is ensured through efficient heat dissipation, while scalability enables modules to meet diverse application needs. IDTechEx’s report, “Antenna in Package (AiP) for 5G and 6G 2024-2034: Technologies, Trends, Markets”, delves into key considerations such as antenna element choice, substrate technology, integration of passive devices, and supply chain maturity. This article will focus on the choice of substrate technology, as it is the key influencer of all the abovementioned requirements.

Various factors must be considered when determining the appropriate substrate technology for AiP. These include core material choices, such as coefficient of thermal expansion (CTE), Young’s modulus, moisture absorption, and thermal conductivity. The manufacturing capability of chosen substrates, including via size, metal layer counts, and line/space features, is also crucial. Moreover, Dk and Df for antenna layers, bumping technology, embedding technology, among others, play significant roles. For instance, lower insertion loss correlates with reducing the number of metal layers in routing, necessitating scaling dimensions of microvias (blind vias). Additionally, high current densities from power amplifier ICs demand numerous through-vias or plated-through-holes (PTHs) on the package substrate, underscoring the importance of precise dimensions for supporting I/O density and signal integrity. Effective power delivery requires specific aspect ratios at < 20 µm pitch, highlighting the complexity of substrate design. AiP substrate material requirements significantly influence antenna performance. A lower dielectric constant (Dk) widens bandwidth and enhances gain, while a high Dk enables smaller AiP sizes. Low dielectric loss (Df) contributes to increased efficiency. High Young's modulus ensures stiffness and reduces warpage, while low coefficient of thermal expansion (CTE) cores better match silicon. Zero moisture absorption is crucial for stability. Smooth surface roughness is needed for low-loss interconnects. Passive component integration requires thicker metallization, low dielectric losses, and flexibility in metal layers.

Presently, four substrate candidates are being considered for AiP technology: HDI (High Density Interconnect) based on low-loss materials, LTCC (Low-Temperature Co-fired Ceramics), High-Density Fan-Out, and glass substrate technology. Among these options, HDI is currently the incumbent technology for AiP. On the other hand, LTCC technology finds its primary application in high-frequency communication sectors, notably in the defense and aerospace industries, where cost considerations hold less weight.

Comparing organic-based substrates like HDI and Fan-out, HDI-based AiP demonstrates the highest supply chain and market maturity, translating into price advantages. However, its routing features, including metal roughness, line/space features, and via diameter, as well as overall package thickness, lag behind emerging fan-out technology. With the ongoing trend of wearables miniaturization, fan-out technology is expected to play a pivotal role in AiP development. Turning to inorganic packages like LTCC and Glass, inorganic AiP offers superior device reliability due to its non-reactivity with moisture compared to organic-based substrates. Glass exhibits notably better routing features than LTCC. However, the primary challenge for glass substrates lies in their immaturity within the supply chain and ecosystem. While LTCC boasts manufacturing and supply chain maturity, it faces hurdles in improving routing features. LTCC substrates, produced through screen-printing and co-firing, feature large RDL features (~100 μm), resulting in decreased signal routing density and increased module complexity.

Back to the initial question – which substrate tech rules for 5G and 6G AiP? IDTechEx anticipates that HDI will maintain its leading position across both infrastructure and consumer devices in the foreseeable future. This is attributed to the maturity of its supply chain and its cost-effectiveness as primary drivers. Nevertheless, this doesn't discount the potential role of inorganic substrates. IDTechEx foresees continued growth in the LTCC and glass market for AiP, particularly with the expanding 5G mmWave market. As for consumer devices, the emergence of mmWave-enabled gadgets is expected to propel the adoption of fan-out technology for AiP despite HDI's current dominance. Fan-out technology offers advantages in package miniaturization and performance, with the higher cost being justified by economies of scale.

The IDTechEx report “Antenna in Package (AiP) for 5G and 6G 2024-2034: Technologies, Trends, Markets”, delves into AiP technologies tailored for 5G mmWave and emerging 6G networks. It analyzes substrate technologies, including organic, LTCC, and glass, alongside packaging methods such as flip-chip and fan-out, from material properties to manufacturing feasibility. The report explores antenna integration beyond 100 GHz, offering case studies and addressing prevalent challenges, projecting a future driven by advanced semiconductor packaging solutions.

Key Aspects of the Report Include

Overview of 5G mmWave Development and 6G Roadmap:

• Explore the status of 5G mmWave development, technology innovation roadmap, key applications, and market outlook.
• Understand the landscape of 6G, including potential spectrum, enabling THz communication technologies, key research and industry activities, roadmap, technical targets, and applications.

Deep Dive into Beamforming Technologies Enabled by Phased Array Antenna for 5G mmWave:

• Compare beamforming technologies of 5G sub-6 vs mmWave.
• Examine phased array technologies, including antenna, semiconductor, and packaging integration components, technical requirements, trends, and design considerations.

Antenna Integration Technologies for 5G mmWave:

• Discuss antenna substrate technology, benchmarking, material requirements, and packaging for phased arrays.
• Explore various antenna packaging technologies for 5G mmWave, including antenna on PCB and antenna in package (AiP), categorized by packaging technologies: Flip-chip vs fan-out. Also, discuss substrate material choices, such as LTCC, low-loss organic-based, and glass, covering production challenges, material choices and benchmark, solutions/case studies from key players, and substrate design considerations for each packaging technology.

Antenna Integration Technologies for Applications Beyond 100 GHz:

• Address challenges in 6G transceiver development, focusing on power requirements, antenna gain, and phased array demands.
• Discuss various potential packaging technologies for beyond 100 GHz applications, covering thermal management options and low-loss material choices for antenna substrates. Include case studies showcasing D-band (110-170 GHz) phased array technology.

10-year granular market forecast of:

5G infrastructure:

• 5G mmWave base station forecast 2023-2034
• Antenna Elements Forecast (Infrastructure)
• AiP for 5G mmWave infrastructure shipment forecast 2023-2034
• AiP for mmWave 5G infrastructure shipment forecast by packaging technology 2024-2034
• mmWave antenna substrate forecast for 5G infrastructure (m2) 2023-2034
• mmWave antenna substrate forecast by material type for 5G infrastructure 2023-2034

5G consumer devices: Smartphone and CPE

• AiP module shipment in mmWave compatible smartphone forecast 2023-2034
• AiP module shipment in mmWave-compatible smartphones by packaging technology 2023-2034
• mmWave smartphone antenna area substrate by packaging technology 2023-2034
• 5G mmWave CPE shipment forecast 2023-2034
• 5G CPE mmWave AiP module shipment forecast by packaging technology 2023-2034
• 5G CPE mmWave AiP substrate area forecast by packaging technology 2023-2034