Thermacore used Flomerics' Flotherm thermal simulation software to solve a challenging thermal management problem in a tower mounted amplifier (TMA) for a cellular base station. Thermal simulation showed that the heat from the 1 by 1.5 inch amplifier chips did not spread out sufficiently to utilize the full extent of the heat sink, causing the chips to overheat. The problem was addressed by adding a vapor chamber to each chip to reduce the spreading resistance and utilize the full extent of the heatsink. The simulation showed this approach reduced the temperature at the base of the heat sink to acceptable levels.

Thermal challenge in cellular base station

Matt Connors, Applications Engineering Supervisor for Thermacore, said that in the past the company would have used a spreadsheet to evaluate the design. ''But for the last several years we have used thermal simulation software to evaluate nearly every thermal management challenge provided by our customers,'' Connors said. ''This method requires far fewer assumptions and provides much more accurate results than we were ever able to obtain with a spreadsheet. Accuracy is critical in thermal design because our customers want to know what will and won't work as quickly as possible so they can get their product into manufacturing and start generating revenues.''

''When we first decided to use thermal simulation we polled our customers and asked them which software package they would like to have us use,'' Connors said. ''They said that they preferred Flotherm over the other leading thermal simulation packages. They use Flotherm themselves so they have confidence in its predictions and can easily incorporate our models into their full system models. Since we began using Flotherm we have been very impressed with its ability to accurately simulate thermal management challenges. On average, our simulation results predict real-world measurements within 5%.''

The simulation results showed that the vapor chamber efficiently spread the heat across the full width of the heatsink so that each of the fins was fully utilized. This reduced the temperatures at the base of the heat sink to acceptable levels. Thermacore built a physical model consisting of a heat source equivalent to a single RF amplifier chip and the vapor chamber and the third of the heat sink that cools this chip. As usual, the physical testing results matched the simulation results within 5%. The improved cooling enables more powerful amplifiers to be placed in compact enclosures.

''This application demonstrates how simulation provides a competitive advantage to thermal solutions companies that are experienced in its use,'' Connors concluded. ''Simulation is much more accurate than conventional formula-driven thermal engineering methods and also takes less time. So we can investigate more design alternatives with a very high level of confidence in the accuracy of the results. Thermacore's strength is not in selling metal by the pound but rather in the design expertise that we deliver to our customers. Our expertise in thermal simulation plays a key role in meeting and exceeding our customers' expectations.''