Consumer devices requiring integration of wireless, video, audio and storage technologies are now the norm. However, as more components are packed onto boards in order to produce the advanced functionality required by modern users, substantial heat and EMI issues arise, with less space to solve the problem. Hence, engineers are challenged to diagnose and resolve the common causes of slower operating speeds, component failures and thermally induced stress.

How can different engineering approches align resources and work together to reduce thermal stress and EMI emissions more efficiently, pass internal reliability requirements and increase product life to enhance the overall system? In reviewing electronic-component designs, all engineers need to be aware of the potential thermal and EMI issues. EMI is found in most of today's devices due to the use of microprocessors, RF chipsets, voltage regulators and other ICs that have high frequency and broad use. Typically, these issues are dealt with at the source or as close to that source as possible with BLS (board-level shielding).

When engineers first realised that thermal issues impact the reliability of systems, designers often turned to a thermal-interface material and heat sink to enhance the heat dissipation. However, these components add weight and cost to the system, and many of the newer and smaller applications simply do not have the space required.

Figure 1: Board-level shielding with combined thermal interface.

A new approach to simultaneously reduce heat and EMI noise would be to apply a TIM (thermal-interface material) to a BLS. By adding a TIM, such as that in Figure 1, the heat is more efficiently transferred from the IC to the large metal surface of the BLS. This heat dissipation would be enhanced by adding a second TIM between the BLS and a second, larger heat spreader (Figure 2).

Figure 2: Board-level shielding with second thermal interface.

A common mistake in managing the heat from ICs is not putting a thermal material between the IC and the BLS. If a TIM is not placed between the BLS and the IC (Figure 3), the excess heat created by the IC is not directly removed. Instead, the heat would simply radiate into the air gap and the metal of the BLS would have little effect on heat dissipation: this creates a problem because air is a very good thermal insulator and does not directly transfer heat. The TIM eliminates the air gap and efficiently transfers heat from the IC to the BLS. The metal of the BLS then effectively expands the surface area for heat dissipation.

Figure 3: Board-level shielding without thermal interface.

There is no single way to protect products from EMI and heat problems. However, by considering both issues earlier on in the design process, costly problems in product testing can be avoided. Companies such as Laird are working on convergence technologies that can combine solutions for EMI and thermal-management concerns into one product. Considering both these problems early in the design process can help eliminate costly issues.