Thermal interface material can play a large role in the system thermal performance, depending on the design choices made. TIMs are critical to minimize the air gaps between the heat sink and the PCB. TIMs not only provide a thermal interface between the PCB and the heat sink, but can have other functions such as electrical insulation or making a mechanical connection. Many types of TIMs are used in LED systems including greases, tapes, pads, and epoxies. Each has its advantages and disadvantages depending on the application. Many characteristics must be considered when selecting a TIM, not just the thermal conductivity. Often overlooked is the bond line thickness of the material, as the thermal resistance of the material is highly dependent on this thickness. Sometimes a thinner TIM with poor thermal conductivity has a lower thermal resistance than a thicker TIM with better thermal conductivity. Both these attributes must be considered when selecting a TIM and their relative effects can be quantified mathematically. However, though a TIM may have better thermal conductivity than air, its conductivity will not be nearly as good as metal’s, so the approach is not to add material between metal components but rather to fill the voids that are typically occupied by air.