As computer technology continues to evolve, chips, processors, connectors, and materials change to ensure faster performance, more storage, and greater bandwidth. Some examples of advanced computing applications include recent explosive growth in AI-enabled devices, machine learning, large data centers, and high-performance computing (HPC). For example, HPC can perform quadrillions of calculations per second, far beyond the approximately three billion calculations per second of a standard 3-GHz processor.
These applications have the potential to revolutionize our daily lives by working with massive data sets, automating tasks, and optimizing operations from manufacturing to healthcare and beyond. But getting the most out of cutting-edge computing capabilities means finding ways to stack chips into larger packages that can handle the volume of data and signal transmission needed.
This leads to further challenges for thermal management because high-performance chips emit more heat, and combining them further concentrates that heat. This, in turn, can damage the substrate, solder, and other components, risking device failure. For this reason, thermal management is critical in larger and more complex packages. Here, we’ll take a closer look at these larger chip packages and some effective thermal management options for them.
What is CoWoS Packaging?
Instead of single chips, advanced computing systems often rely on multiple chips working in conjunction with each other. Also called chip-on-wafer (CoW) packages, this refers to a stack of chips on a silicon wafer, also called a silicon interposer or carrier. The interposer is then secured to a substrate layer, to which various components are added to interconnect the chips.
The entire assembly is known as a chip-on-wafer-on-substrate (CoWoS) and is an advanced method for packaging multiple chips into a compact, efficient configuration for high-performance computing and AI applications. Whereas previous packaging methods faced memory limitations, CoWoS enables heterogeneous integration of high-bandwidth (HBM) and logic SoC on a single component. These features are essential for contemporary data centers dependent on HBM to improve memory capacity and bandwidth.
Thermal Interface Materials and Cooling Technologies in CoWoS
A downside to this increased computing power is heat generation. Each chip creates heat, and when they are stacked into larger groups, that heat multiplies and is highly concentrated. This can lead to thermal stress, especially when materials have varying coefficients of thermal expansion. And that may result in warping, seal failures, solder failure, separation of components, or delamination, which can trigger data loss, equipment malfunctions, and safety risks.
While greater chip integration produces more heat, CoWoS packaging also facilitates more effective thermal management via several important design features:
- More thermally efficient materials, such as copper graphene and liquid nanometals
- Precision-engineered thermal interface materials (TIMs) that balance temperature stability with performance
- Novel heat dissipation structures and active cooling technologies
Overcoming Heat Challenges in High-Density Semiconductor Packaging with Advanced Modules
Innovations in high-thermal-conductivity materials make it possible to manage the heat generated by CoWoS devices and dissipate it effectively. Some examples include:
- Liquid metal-based thermal interface materials (LM TIMs), comprised of metal nanoparticles with enhanced thermal conductivity
- Soft thermal composites, featuring LM particles capable of fine-tuning thermal and electrical conductivity levels
- Photo-responsive materials, such as gel and phase-change materials (e.g., reduced graphene oxide, expanded graphite, and porous biochars)
These advancements carry many promising industry applications. For example, TIMs made of LM-based e-skins allow medical technicians to target tumors with greater precision and efficiency. LM TIMs also support more rapid advancement of soft electronics, which depend on greater heat dissipation to improve working performance.
CoWoS packaging can also incorporate physical structures that facilitate cooling and heat management, such as:
- Heat spreaders and heatsinks with fins that collect heat from localized hot spots, then dissipate it along the axial length or surface of a device. This takes advantage of the device’s physical design to reduce temperature gradients.
- Vapor chambers, which are flexible thermal modules that enable heat transfer between two and sometimes three dimensions.
- Microfluidic cooling solutions, such as etched channels, are also known as embedded, 3D-heterogenous, or integrated cooling systems. These can bring liquid cooling materials into the chip itself, much closer to the transistors and heat-generating activity, bringing effective cooling to the point of need.
Need help solving CoWoS thermal challenges?
By dramatically increasing computing power, CoWoS technology opens the door to more robust and efficient data transmission and analysis. However, with that power comes the challenge of thermal management. T-Global Technology provides a range of products and materials that keep CoWoS devices cool and functional.
Contact us to learn more about our thermal interface products and how they can improve thermal management for your next project.