The supply chain log jam continues, with procurement specialists facing one of the most challenging macroeconomic environments in years. Historically, OEMs sourcing thermal management solutions faced lead times between 12 to 18-weeks for fans and as little as four to six-weeks for solutions like thermal interface materials (TIM). Today, lead times for fans, TIMs and heat sinks have more than doubled, tripled or even quadrupled in some cases. While fans usually have relatively longer lead times, the 300 per cent increase has made things particularly challenging.
Long lead times are causing purchasing departments to scramble for equivalents or ‘crosses’. Buyers often ask distributors to match the original product’s exact specifications. However, these exercises often fail because the search criteria are too narrow. Understanding which specifications are necessary and which are flexible can make a huge difference. Here are some tips.
For fans, size and voltage are hard requirements. For new designs, common sizes and voltages will create a deeper pool of options. For example, 40 and 80mm square fans with 12 or 24V operating voltage are more readily available since they’re commonly used for 1U and 2U server racks.
Airflow is the most important variable for cooling but the maximum airflow (usually listed in CFM) is not the same as the system’s operating airflow.
The number of wires on a fan can be relatively flexible. For example, a four-wire fan can be used in a two-wire design by cutting off the other wires during installation.
Thermal interface material format (dispensable or tape/pads) is usually a hard requirement. Other features such as thermal conductivity, gap pad softness or minimum bond lines are a little more flexible. Engineers can help broaden the search by providing an acceptable, rather than a particular, number. For example, when replacing a 5W/m-K gap pad, an engineer may allow pads as low as 3W/m-K. This is especially true in low power applications where decreased conductivity will lead to a small increase in temperature.
Lastly, regarding silicone based thermal interface materials, swapping to a non-silicone based TIM may be an option.
Another important consideration is air v sea shipment. Prior to recent supply chain disruptions, it was common for companies to authorize air shipments. With air shipment costs increasing three-fold or more (especially on heavier items such as fans) there is understandable reluctance to incur extra costs. However, air may be the right choice, given long lead times.
Working directly with a product specialist provides a better handle on lead times, end-of-life warnings, impact of customization and pricing. A proactive specialist distributor will consider all available options. Volume price breaks and stocking agreements are essential when considering price, availability and, most important in this environment, commitment.