Put the investment in, get the heat out

Within the important lighting and automotive markets, and also throughout motor-control and power-conversion applications generally, there is increasing pressure to miniaturise form factors, reduce costs and further increase system performance. As a result, demand for creative thermal design using high-performing materials and techniques is intensifying and engineers increasingly are required to take a calculated approach, using a combination of products such as gap fillers, thermal gels, carefully sized heatsinks, and thermal-clad substrates.

Thermal-clad substrates allow engineers to use the PCB more effectively as a part of their thermal design, and can be used to supplement or even eliminate a conventional heatsink. This gives extra freedom to operate components at a stable target temperature, which enhances system reliability and, in the case of LED lighting, improves lumen maintenance yielding longer lifetimes and better light quality.

A thermal-clad substrate has significantly greater thermal conductivity than a standard FR4 PCB, and can save the expense and complexity of adding plated thermal vias or heat-spreaders to the FR4. In addition, thermal-clad is more mechanically robust compared to other thermal substrates such as direct-bond copper (DBC) or thick-film ceramics.

Growing demand

Engineers are switching onto the opportunities that this technology can provide, to meet system performance and reliability targets within tight restrictions on overall cost and size. Demands are growing for a wider range of thermal-substrate products offering differentiated properties, as well as increased volume of supply, short lead times, and direct access to design-in support.

The key to optimising the performance of a thermal-clad substrate in a given application lies in the properties of the dielectric. Bergquist, the original pioneer of thermal-clad substrates, addresses a broad spectrum of power requirements with its range of four dielectrics comprising High-Road (HRT), Multi-Purpose (MP), High-Temperature (HT) and special High-Power Lighting (HPL) formulas. HPL is the newest innovation, delivering ultra-high performance for LED lighting applications with the most demanding thermal requirements. Complementing the high-performance dielectrics is a choice of aluminium or copper base layers with various thicknesses, standard brushed finish, and even anodised aluminium colour options. Unique fabrication techniques, developed over several product generations, ensure Bergquist’s T-Clad substrates are ideally suited to today’s high Watt-density surface-mount applications and will outperform alternatives such as thermally enhanced laminated PCBs comprising pre-preg sheets and metal heat-spreader foils.

Various types of substrates from different manufacturers can be compared quite effectively using the thermal conductivity figures published in datasheets. It is important to remember, however, that thermal impedance is the best measure for predicting performance in a real-world application, as this also takes in to account material thickness, interfacial resistances and reinforcement materials that are not always included in bulk material thermal conductivity tests. In addition, information regarding the test procedures used by manufacturers for measuring material properties like thermal conductivity helps customer engineers to verify published figures and compare products from various suppliers independently. To support this, Bergquist uses internationally recognised test standards or, where these are not available, makes information about its test methods freely available to customers.

Power LED technology

Bergquist’s long experience with thermal-clad substrates is of particular value to the LED lighting industry. Power LED technology is still relatively young, particularly in terms of building up reliability data, as devices can have theoretical lifetimes as long as 50,000 hours. Bergquist can provide data from its own programs to help predict the practical lifetimes of individual emitters and light-engine assemblies and hence assist customers to optimise design details and operating parameters.

If having an extensive choice of thermal products and performance is an important advantage for power-systems designers, knowing how and when to use them is equally vital. To help support designers as demand continues to grow for high-quality thermal-clad solutions, Bergquist is increasing its technical strength both in the field and at local engineering centres worldwide.

Bergquist believes the depth and quality of its technical staff supporting customers provides the platform for success, creating a body of knowledge within the organisation that is further sustained by training and knowledge sharing between customer-facing engineers.

Altogether, Bergquist’s recent investment in its T-Clad technology has totalled over $10 million, directed towards driving research and development, increasing technical support, and boosting substrate production capacity by more than 3.5 times to fulfil growing demand. Its over-arching goal is to maintain its leading role in advanced thermal management for more economical cars, higher performing LED lighting and generally more efficient, reliable and usable high-power electronics.