Set-top box is an electronic device that converts network broadband, satellite antenna and cable TV signals into TV programs. With the continuous technological progress in the past two years, set-top box manufacturers have added more high-power high-frequency components into the box to achieve the purpose of adding more functions. Once the CPU temperature of the box exceeds 80℃, it will lead to the box to initiate frequency reduction through self-protection and shutdown function. How to avoid the degradation of set-top box performance due to high temperature has become a crucial part of the structure design.

With the trend of smaller and smaller set-top box structure design, how to effectively take away the high heat generated by the high-power CPU and image processing chip of the set-top box through reasonable structure layout has also become a key concern for set-top box structure engineers.

Set-top box heat dissipation is generally passive heat dissipation, the traditional heat dissipation program is the main; now the trend is to eliminate the heat sink, the use of structural heat dissipation parts (today's bracket, metal shell); or heat sink program and heat dissipation structural parts program combination; in different system requirements and environment, choose the best cost-effective program. A, if the heat sink program, it is not recommended to directly use low thermal conductivity of the thermal conductivity of the double-sided adhesive; also not recommended to use does not have the function of shock absorption of the thermal conductivity of the silicon grease; recommended to use the metal hook connection or plastic pushpin to operate, choose 0.5mm thickness of the thermal conductivity of the silicon film with the use of these two programs easy to install and operate, but also can not be used by the glue, heat dissipation will be much better than the thermal conductivity of the double-sided adhesive, more safe and reliable. The total cost, including unit price, manpower, equipment will be more competitive. Second, the choice of heat dissipation structural parts class heat dissipation, it is necessary to consider heat dissipation structural parts in the contact surface of the structure of the form of local protrusion, local avoidance, etc., in the structure of the process and the size of the thermal conductive silicone film to choose a good balance. Under the condition that the process allows, it is recommended not to choose a particularly thick thermal conductive silicone film. Here generally for the convenience of the operation is recommended to use a single-sided was glued, with the glued side to the heat dissipation structure parts; here to particularly choose a good compression ratio to ensure a certain pressure to the thermal conductive silicone film. (The thickness of the thermal conductive silicone film must be selected greater than the theoretical gap between the thermal structure and the heat source upper work difference, generally can be more than 1mm --- 2mm) choose the thermal structure of the heat dissipation also to consider the location of components in the pcb layout, height and package form, you can place some heat sources regular, reduce the cost of the thermal structure. Third, the choice of thermal conductivity. Thermal conductivity selection depends most on the size of the heat source power consumption, as well as the size of the heat sink or thermal structure of the heat dissipation capacity. General chip temperature specifications parameters are relatively low, or more sensitive to temperature, or heat flow density is relatively large (generally greater than 0.6w/cm3 need to do heat dissipation treatment, the general surface is less than 0.04w/cm2 when only natural convection processing can be) these chips or heat sources need to be heat dissipation treatment, and try to choose a high coefficient of thermal conductivity of the thermal conductive silicone film. Consumer electronics industry generally does not allow the chip junction temperature higher than 85 degrees, it is also recommended to control the surface of the chip in the high-temperature test less than 75 degrees, the entire board components are also basically commercial-grade components, so the internal temperature of the system at room temperature is recommended not to exceed 50 degrees. The first appearance of the surface, or the end customer by the surface can contact the recommended temperature at room temperature must be less than 45 degrees. The choice of thermal conductivity of the higher thermal conductivity silicone film can meet the design requirements and retain some design margin.

Generally, the heat flow density on the chip surface is relatively small, and the influence of surrounding heat sources is relatively small, so the thermal conductivity can be low to reduce the cost; the thermal conductivity is the biggest factor affecting the cost of thermal conductive silicone film. Size and thickness will affect the cost of the product.