How to install PCB electronic heat sink?

A heat sink is a device that dissipates heat from heat-prone electronic components in electrical appliances. It is usually made of aluminum alloy, brass or bronze in the form of plates, sheets, or multiple sheets. For example, a CPU in a computer requires a relatively large heat sink, and power tubes, line tubes, and amplifier tubes in a TV all require heat sinks. Generally, a heat sink should be coated with a layer of thermal conductive silicone grease on the contact surface between the electronic component and the heat sink during use, so that the heat generated by the component can be more effectively transferred to the heat sink and then dissipated into the surrounding air through the heat sink. Many devices in communication products have relatively high power consumption and require heat sinks for heat dissipation. Common methods of fixing heat sinks include mechanical fixing and adhesive fixing. Common installation problems include adhesive heat sink falling off, screw-mounted heat sinks causing PCB bending, and even device failure, especially BGA solder joint failure.

(1) Use mechanical methods to fix the heat sink. An elastic installation method should be used. It is strictly forbidden to use inelastic screws for fixing. The main function of thermal conductive silicone is to fill the gap between the heat sink and the component, improve the heat transfer efficiency, accelerate the heat dissipation, and ensure the normal working temperature of the components.

(2) It is not recommended to share a heat sink with multiple chips, especially BGA chips. They will collapse freely during welding, and their height from the PCB surface is difficult to control. Therefore, when multiple chips share a heat sink, the heat sink can only be installed and fixed by a thermal conductive pad plus a heat sink and fixed mechanically. However, this design often causes the BGA solder joints to be flattened or broken due to the installation sequence of the screws during installation.

(3) When using the adhesive process, the matching of the adhesive area and the contact surface of the heat sink and the wettability of the adhesive and the heat sink surface should be considered (for example, some adhesives are not wettable with Ni plating), otherwise it is easy to fall off.