Thermal conductive silicone film backing whether single-sided or double-sided will increase its thermal resistance, thereby reducing the thermal conductivity.

One of the main reasons for single-sided backing or to play a fixed role, simply put, the advantages of single-sided backing and double-sided backing is a fixed device, eliminating the need for screws to fix the radiator, saving costs. In fact, the principle of double-sided backing or based on the single-sided backing, but the double-sided backing stability will be stronger, this is based on the customer's design needs and structural needs.

Single-sided backing of thermally conductive silicone film.
Single-sided backing is mainly to facilitate the installation of thermal conductive silicone lamination, not easy to install, so the use of single-sided backing, the side of the thermal conductive silicone film ready to glue on the PCB board, the other side on the shell.
It can stick to the surface of the heat source on one side, when the assembly process of the heat sink or shell have relative sliding, the thermal conductive silicone film will not be moved to cause the position offset, to play a fixed role.
Thermal conductive silicone film double-sided adhesive backing.
Double-sided backing is mainly because the product does not have a fixed device or inconvenient to fix, double-sided backing can be used to fix the heat sink, the IC and heat sink stick, without the need to design another fixed structure.
It can be used to fix the heat sink, no need to design a separate fixing structure, such as no locking screws, reducing customer costs. However, the thermal conductivity of the silicone film backing will become worse, and the coefficient of conductivity will be much lower. Double-sided adhesive backing thermal conductivity will be worse than single-sided adhesive backing thermal conductivity, but whether it is single-sided or double-sided adhesive backing, the thermal conductivity will affect a lot lower become lower. The thermal conductivity becomes worse, but the cost will increase.
In general, whether the thermal conductive silicone film backing, single-sided backing or double-sided backing, but also according to the actual situation to decide!