In response to the demands of high-performance computing, AI, 5G, and other applications, the shift towards chiplet and the incorporation of HBM memory has become inevitable for advanced chips. As a result, packaging has transitioned from 2D to 2.5D and 3D formats.

With chip manufacturing advancing towards more advanced process nodes, the model of directly packaging chips using advanced packaging technology from wafer foundries has emerged. However, this approach also signifies that wafer foundries will encroach upon certain aspects of traditional assembly and testing, leading to ongoing discussions about the ‘threat’ to traditional assembly and test firms since TSMC’s entry into advanced packaging in 2011.

But is this perspective accurate?

In fact, traditional assembly and test firms remain competitively positioned. Firstly, numerous electronic products still rely on their diverse traditional packaging techniques. Particularly, with the rapid growth of AIoT, electric vehicles, and drones, the required electronic components often still adopt traditional packaging methods. Secondly, faced with wafer foundries actively entering the advanced packaging domain, traditional assembly and test firms have not been idle, presenting concrete solutions to the challenge.

Advanced Packaging Innovations by Traditional Assembly and Test Firms

Since 2023, AI and AI server trends have rapidly emerged, driving the demand for AI chips. TSMC’s 2.5D advanced packaging technology, known as CoWoS, has played a pivotal role. However, the sudden surge in demand stretched TSMC’s capacity. In response, major traditional assembly and test firms such as ASE and Amkor have demonstrated their technical prowess and have no intention of being absent from this field.

For instance, ASE’s FOCoS technology enables the integration of HBM and ASIC. It restructures multiple chips into a fan-out module, which is then placed on the substrate, achieving the integration of multiple chips. Their FOCoS-Bridge technology, unveiled in May this year, utilizes silicon bridges (Si Bridge) to accomplish 2.5D packaging, bolstering the creation of advanced chips required for applications like AI, data centers, and servers.

Additionally, SPIL, a subsidiary of ASE, offers the FO-EB technology, a powerful integration of logic IC and HBM. As depicted below, this technology eschews silicon interposers, utilizing silicon bridges and redistribution layers (RDL) for connections, similarly capable of 2.5D packaging.

Another major player, Amkor, has not only collaborated with Samsung to develop the H-Cube advanced packaging solution but has also long been involved in ‘CoWoS-like technology.’ Through intermediary layers and through-silicon via (TSV) technology, Amkor can interconnect different chips, also possessing 2.5D advanced packaging capabilities.

China’s major assembly and test firm, Jiangsu Changjiang Electronics Technology (JCET), employs the XDFOI technology, integrating logic ICs with HBM through TSV, RDL, and microbump techniques, aimed at high-performance computing.

Given the recent surge in demand for high-end GPU chips, TSMC’s CoWoS capacity has fallen short, and NVIDIA is actively seeking support from second or even third suppliers. The ASE Group and Amkor have secured partial orders through their packaging technologies. This clearly illustrates that traditional assembly and test firms, even when faced with the entry of wafer foundries into the advanced packaging domain, still possess the capability to compete.

In terms of product types, wafer foundries focus on advanced packaging technology for major players like NVIDIA and AMD. Meanwhile, other products not in the highest-end category still opt for traditional assembly and test firms like ASE, Amkor, and JCET for manufacturing. Overall, with their presence in advanced packaging, as well as a hold on the expanding existing packaging market, traditional assembly and test firms continue to maintain their market competitiveness.

(Photo credit: Amkor)

Over the past few decades, semiconductor manufacturing technology has evolved from the 10,000nm process in 1971 to the 3nm process in 2022, driven by the need to increase the number of transistors on chips for enhanced computational performance. However, as applications like artificial intelligence (AI) and AIGC rapidly advance, demand for higher core chip performance at the device level is growing.

While process technology improvements may encounter bottlenecks, the need for computing resources continues to rise. This underscores the importance of advanced packaging techniques to boost the number of transistors on chips.

In recent years, “advanced packaging” has gained significant attention. Think of “packaging” as a protective shell for electronic chips, safeguarding them from adverse environmental effects. Chip packaging involves fixation, enhanced heat dissipation, electrical connections, and signal interconnections with the outside world. The term “advanced packaging” primarily focuses on packaging techniques for chips with process nodes below 7nm.

Amid the AI boom, which has driven demand for AI servers and NVIDIA GPU graphics chips, CoWoS (Chip-on-Wafer-on-Substrate) packaging has faced a supply shortage.

But what exactly is CoWoS?

CoWoS is a 2.5D and 3D packaging technology, composed of “CoW” (Chip-on-Wafer) and “WoS” (Wafer-on-Substrate). CoWoS involves stacking chips and then packaging them onto a substrate, creating a 2.5D or 3D configuration. This approach reduces chip space, while also lowering power consumption and costs. The concept is illustrated in the diagram below, where logic chips and High-Bandwidth Memory (HBM) are interconnected on an interposer through tiny metal wires. “Through-Silicon Vias (TSV)” technology links the assembly to the substrate beneath, ultimately connecting to external circuits via solder balls.

The difference between 2.5D and 3D packaging lies in their stacking methods. 2.5D packaging involves horizontal chip stacking on an interposer or through silicon bridges, mainly for combining logic and high-bandwidth memory chips. 3D packaging vertically stacks chips, primarily targeting high-performance logic chips and System-on-Chip (SoC) designs.

When discussing advanced packaging, it’s worth noting that Taiwan Semiconductor Manufacturing Company (TSMC), rather than traditional packaging and testing facilities, is at the forefront. CoW, being a precise part of CoWoS, is predominantly produced by TSMC. This situation has paved the way for TSMC’s comprehensive service offerings, which maintain high yields in both fabrication and packaging processes. Such a setup ensures an unparalleled approach to serving high-end clients in the future.

Applications of CoWoS

The shift towards multiple small chips and memory stacking is becoming an inevitable trend for high-end chips. CoWoS packaging finds application in a wide range of fields, including High-Performance Computing (HPC), AI, data centers, 5G, Internet of Things (IoT), automotive electronics, and more. In various major trends, CoWoS packaging is set to play a vital role.

In the past, chip performance was primarily reliant on semiconductor process improvements. However, with devices approaching physical limits and chip miniaturization becoming increasingly challenging, maintaining small form factors and high chip performance has required improvements not only in advanced processes but also in chip architecture. This has led to a transition from single-layer chips to multi-layer stacking. As a result, advanced packaging has become a key driver in extending Moore’s Law and is leading the charge in the semiconductor industry.

(Photo credit: TSMC)