However, manufacturing these high-performance packages requires careful material selection, rigorous process control, and continuous innovation in package manufacturing techniques. The latest IDTechEx report, “Materials and Processes for Advanced Semiconductor Packages 2027–2037: Technologies, Players, and Forecasts,” analyzes these challenges in relation to 2.5D package materials and process flows—including silicon, organic-based materials, and glass—as well as Cu-Cu hybrid junctions for 3D integration. The report also provides 10-year forecasts for advanced semiconductor package modules based on organic dielectrics and glass, covering both per-unit and per-surface projections.

Materials for 2.5D Interposers:
In 2.5D packaging, the various chiplets are horizontally interconnected by interposers, for which three main materials are considered: silicon (Si), organic materials, and glass. Silicon interposers are the industry standard for high-performance computing (HPC) due to their ability to support fine routing, but their high cost and package area limitations pose a challenge. To mitigate these, localized Si bridges represent the next step forward. Organic interposers offer a cost-effective alternative, particularly with fan-out panel-level packaging (FOPLP), which increases area utilization and reduces costs by up to 60%. However, achieving silicon-like fine routing remains difficult.

Glass interposers, or glass-core substrates (GCS), have the potential to support high routing density, provide good dimensional stability, reduce warping in large-area packages, offer an adjustable coefficient of thermal expansion, and enable low-loss electrical performance, among other advantages. Importantly, glass is also compatible with panel-level processing, making it attractive as package sizes continue to increase for AI and HPC chips. However, several manufacturing challenges remain, including process control and performance improvement in via forming and metallizing through glass, handling large panels, glass cracking and mechanical reliability issues, cleanliness and contamination control, and more. Mitigating failures in glass substrates requires optimization at the design, materials, and process levels, rather than a one-off solution. Therefore, although glass offers great potential as a scalable materials platform, its adoption will depend on whether the manufacturing ecosystem is able to address these challenges on a large scale.

In general, as the ecosystem evolves, each material brings its own advantages and challenges to 2.5D encapsulation, focusing on balancing performance, scalability, and cost.

Cu-Cu Hybrid Bonding:
Wafer-to-wafer (W2W) and chip-to-wafer (D2W) hybrid bonding are two key approaches to 3D hybrid bonding, each with distinct advantages and challenges. W2W bonding, the more established process, involves joining two complete wafers, typically in a single, uniform step. This approach benefits from a consistent surface, making alignment and bonding relatively straightforward. Because the wafers always maintain a round shape, the process can be optimized for high throughput, making it suitable for large-scale production. However, W2W bonding is less flexible when handling chips of varying sizes and is limited by the requirement to bond identical wafers.

On the other hand, hybrid D2W bonding is more complex and overcomes the limitations of W2W bonding when working with high-performance chips of varying sizes. Instead of bonding entire wafers, D2W involves the precise bonding of individual chips onto a target wafer, enabling the integration of chips of different sizes and types into a single package. This flexibility makes D2W bonding ideal for advanced packaging techniques, such as chiplet integration, allowing manufacturers to combine chips with different functions. However, D2W bonding presents significant manufacturing challenges. It demands ultra-clean, particle-free surfaces and precise alignment, as any contamination or misalignment can lead to defects that significantly compromise bond quality.
Furthermore, D2W bonding introduces complications related to chip aspect ratios. Chips with higher aspect ratios can cause one-sided bonding problems, where the bonding front begins along one side, potentially resulting in a scaling effect. The use of flexible organic supports or adhesives during chip cutting further complicates the process. Furthermore, D2W bonding is more sensitive to waiting times, which can degrade surface quality before bonding occurs.

Despite these challenges, the flexibility and accuracy of D2W joining are becoming increasingly critical for high-performance applications, while integrated hybrid joining tools are emerging to address many of these obstacles.

Thermal interface materials for next-generation advanced semiconductor packaging:
Thermal management is also a critical consideration in advanced semiconductor packaging. In 2.5D packages, high-power logic chips and HBM stacks are placed side-by-side under the same heatsink, increasing the overall package power and creating local hot spots. In 3D packaging, the challenge is compounded, as vertically stacked chips can create hidden heat sources with limited heat dissipation paths.

This increases the importance of thermal interface materials (TIMs) for 2.5D and 3D packages. TIM selection is determined by several factors, including thermal resistance, material thermal conductivity, mechanical reliability, contact quality, ease of testing, cost, and compatibility with large-scale manufacturing.
Various TIM1 and TIM1.5 solutions are being explored, including polymer-based thermal greases, solid metallic TIMs such as indium foils, liquid metals, and graphene-based materials. The IDTechEx report examines the potential roadmap for TIMs in advanced semiconductor packaging, key considerations for material selection, candidate materials, and relevant use cases.

The report includes 10-year forecasts for advanced semiconductor package modules with organic and glass-based dielectrics, covering both unit shipments and total module area. The forecasts assess adoption in AI accelerators, server CPUs, ADAS chips in autonomous vehicles, and consumer electronics, with particular emphasis on the growing importance of large-area advanced package platforms in AI and HPC applications.