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.

 

 

Overview of 5G mmWave Development and 6G Roadmap:

 

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

 

Antenna Integration Technologies for 5G mmWave:

 

Antenna Integration Technologies for Applications Beyond 100 GHz:

 

10-year granular market forecast of:

 

5G infrastructure:

 

5G consumer devices: Smartphone and CPE

 

To find out more about the IDTechEx report report "Antenna in Package (AiP) for 5G and 6G 2024-2034: Technologies, Trends, Markets", including downloadable sample pages, please visit www.IDTechEx.com/AiP.

 

For the full portfolio of 5G, 6G, RFID & Telecoms market research from IDTechEx, please see www.IDTechEx.com/Research/5G.

 

IDTechEx provides trusted independent research on emerging technologies and their markets. Since 1999, we have been helping our clients to understand new technologies, their supply chains, market requirements, opportunities and forecasts. For more information, contact research@IDTechEx.com or visit www.IDTechEx.com.