As the demand for artificial intelligence (AI) and high-performance computing (HPC) systems continues to push the boundaries of semiconductor performance, the packaging process is facing new challenges that go beyond traditional concerns about interconnect density. The focus is now shifting towards the mechanical and process-control limitations of advanced packaging.

At the heart of the issue is warpage, a problem that becomes more pronounced as package sizes grow. Packaging that was once thought of as a passive shell is now being recognized as an integral part of system performance. Factors such as substrate behavior, thermal paths, power delivery, and process sequencing all play a crucial role in determining what can be built and manufactured at scale.

Sandeep Razdan, director of the Advanced Technology Group at NVIDIA, highlighted at the iMAPS conference that, “What really drives performance today is not really the number of flops or teraflops per GPU, but rather the system architecture and the system performance as a whole.” As packaging becomes an active part of system performance, packaging issues such as warpage, alignment, and bonding yield are now seen as potential bottlenecks that must be addressed before scaling up advanced systems.

Warpage has emerged as one of the most significant issues in advanced packaging. It is not merely a nuisance; it’s a structural challenge that stems from material imbalances within the packaging stack. These imbalances are exacerbated as larger and more complex systems are built, with silicon placed on top of organic materials and multiple layers with differing thermal and mechanical behaviors.

The introduction of glass into packaging processes has been suggested as a solution to reduce warpage. Glass is thermally stable and dimensionally flat, making it a good match for silicon wafers. However, it brings its own set of challenges, particularly in terms of brittleness and microcracking. As the size of glass panels increases, these mechanical problems become more pronounced, and handling defects such as edge damage and microcracks become critical factors that can affect the yield of advanced packaging processes.

Hybrid bonding, which offers high interconnect density, has become essential for AI and HPC systems. However, as pitch sizes shrink, the yield is increasingly driven by stress rather than defects. The challenges with hybrid bonding become more complex as copper density increases and mechanical stress grows, affecting yield and process control. As the pitch size reduces to 2-3 microns, the stress-driven regime begins to dominate, presenting new manufacturing hurdles that require more refined techniques for handling contamination, alignment, and topography.

Advanced packaging is entering a phase where each process step affects subsequent steps, and mechanical stability must be maintained throughout. From backside power delivery to thinning processes, the challenges are becoming more interdependent. For example, the precision required for backside processing is now a critical part of the overall packaging process, as grinding and bonding must be tightly controlled to avoid defects.

As packaging sizes grow and processes become more complex, the entire stack’s stability—thermal, mechanical, and electrical—must be considered holistically. This requires a shift from optimizing individual unit processes to managing the cumulative effect of all steps involved in the packaging process. Understanding how the materials and processes interact at every stage of assembly will be key to continuing the evolution of advanced packaging for AI and HPC applications.