Data centers bring thermal management challenges

Next-generation data centers bring thermal management challenges for I/O modules as data-center architects and operators face higher-speed data throughput and growing power density requirements, according to a recent Molex report. These challenges result in a need for new heat dissipation solutions for critical servers and interconnect systems. The report discusses these challenges and advances in thermal management to address the need for next-generation cooling of servers and data centers.

(Source: Molex)

Molex’s In-Depth Report of Thermal Management Solutions for I/O Modules covers the limitations of traditional thermal characterization and management as a result of faster data rates and optical I/O module power requirements that are driving traditional forced-air-cooling to operational limits. The shift to 224 Gbits/s PAM-4 interconnects between servers and network infrastructure, as an example, doubles the per-lane data rate and produces nearly a 4× increase in power density, which increases thermal management costs and complexities, according to the report.

Optical modules are reaching as high as 40 W over long-range coherent links, up from 12 W a few years ago, Molex said.

“As demand for faster, more efficient data processing and storage continues to rise rapidly, so does the heat generated by the high-performance servers and systems needed to scale generative AI applications and support the transition from 112 Gbits/s PAM-4 to 224 Gbits/s PAM-4,” said Doug Busch, VP & GM, Enabling Solutions Group, Molex, in a statement. “The integration of optical connectivity and optical modules, applied with new cooling technologies, will optimize airflow and thermal management within next-gen data centers.

The report covers both traditional cooling methods, like forced airflow, liquid cooling and heat sinks, as well as new innovations in server and optical module cooling to support 112G and 224G connectivity, including Molex’s drop-down heat sink (DDHS) solution that can replace riding heat sinks.

It also discusses direct-to-chip liquid cooling, immersion cooling and the role of heat sinks as well as the cooling methods that are most effective for meeting the power demands in chips and I/O modules. Part of the discussion includes the costs and risks associated with immersion cooling.

Molex solutions

Molex highlights two of its latest cooling solutions for optical modules, including DDHS and its liquid cooling solution, called the integrated floating pedestal.

The DDHS design eliminates the direct contact between the optical module and thermal interface material (TIM) that can create durability issues, while increasing heat transfer efficiency. Molex said it allows for implementation of the TIM for more than 100 insertion cycles and it can be implemented in different single-row and stacked-cage configurations. It offers up to a 9°C improvement at 35 W, compared to a zipper fin-heat-sink solution, according to the company.

For cooling pluggable I/O modules, Molex’s integrated floating pedestal liquid allows the heat to flow directly from the module, generating the heat, to the pedestal over the shortest possible conduction path. This results in lower thermal resistance and improved heat transfer efficiency.

In this design each pedestal that contacts the module moves independently, allowing the implementation of a single cold plate to different 1×N and 2×N single-row and stacked-cage configurations. One example cited is a solution for a 1×6 QSFP-DD module that uses six independently moving pedestals, which can compensate for varying port stack heights while ensuring thermal contact.

The report also addresses the need for new standardization and testing for next-generation cooling approaches. One example is the use of case temperature as a specification.

A key factor in the design of cooling strategies for optical modules is the use of case temperature as a specification or limit in the module temperature. However, Molex said “a case temperature specification alone will not provide an accurate reflection of the internal temperature of the critical components on the module.”

Molex is collaborating with other industry leaders, as part of the Open Compute Project (OCP) and its Cooling Environments project, to develop next-generation cooling technologies and testing strategies for today’s data centers.