Thermal
imaging (Figure 5) illustrates that materials having 'in plane' thermal conductivities of 2 to 4 W/mk will increase a board's ability to remove component-generated heat by a factor of 10 to 20 times over that of conventional epoxy board materials, which typically have a thermal conductivity of 0.2 W/mk. It soon becomes evident that the use of thinner materials and higher strength dielectrics in conjunction with a lower thermal impedance is advantageous for use in all high power and high-density applications.
Figure 5: Thermal management in electronics
RF designs
As the importance of good thermal management applies to high-power digital designs, proper thermal management is equally important in the RF arena, and in particular, to RF power amplifier applications. Often, the use of conventional heat-sinking in high-power RF circuits creates a host of design issues, and, therefore, it becomes increasingly necessary to incorporate unique or novel heat-sinking methods within the active RF realm. Unfortunately, this typically incurs additional costs for engineering, prototyping, and manufacturing.
As RF frequencies and amplifier power demands increase, the need for more efficient heat dissipation becomes the main priority. In addition to the heat-sinking dilemma, the thermal stability of a board material also plays a crucial role in maintaining consistent and reliable operation over a wide temperature range. (Figure 6).
Figure 6: Practical Application: 0.5W heat source
One good example of a thermally-stable material is Arlon's PTFE, which combines excellent thermal conductivity with a high dielectric constant, remaining stable over an unusually wide temperature range. Maintaining a good thermal dielectric constant can dramatically reduce changes in circuit impedance, RF reflection, and dead band shift. (Figure 7).
Figure 7: Temperature Sensitivity to Dielectric Constant
Advancements
The unique combination of specialty materials, appropriate product development methodology, and state-of-the-art manufacturing processes will pave the way for more rapid advancements in digital and RF circuits where high heat and high energy are an inherent part of the design.
The integration of single-sided, multi-layer and rigid-flex technologies with specialty materials can lower overall production costs by reducing or eliminating the need for conventional heat-sinking systems. Additionally, the use of such materials and processes can provide improved longevity, reliability, and weight reduction.
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