197 views Yuda Electronic (HK) Technology Co.,Limited. 2019-06-10
Power adapter thermal design is to minimize the heat input from the electronic device and improve the heat dissipation effect. The harmful heat inside the electronic device is discharged into the environment outside the electronic device to obtain a suitable working temperature to ensure the safe operation of the device. The thermal design of electronic devices can be divided into three levels.
(1) System-level thermal design of electronic equipment chassis, frame and square cavity, ie system-level thermal design.
(2) Power adapter thermal design of electronic modules, heat sinks, and PCBs, that is, package-level thermal design.
(3) Component-level thermal design, that is, component-level thermal design.
System-level thermal design mainly studies the influence of the temperature of the environment in which electronic equipment is located. The ambient temperature is an important boundary condition for system-level thermal design. System-level thermal design is the measure to control the ambient temperature to allow the electronic device to operate at a suitable temperature.
The biggest problem faced by system-level manufacturers is the development of a highly efficient chassis, chassis and square cavity so that heat can be quickly introduced into the environment. The design considerations for each type of electronic device are different and a clear understanding of the performance and size constraints of the electronic device is required. For example, a reliable and efficient connection must be made between the metal block and the PCB spacer. Typically, heat passes through the thermal vias on the PCB to the copper blocks of the other layer, after which the heat enters the outer casing or external heat sink in a thermally conductive manner.
The development of package-level thermal design is relatively mature, and there has been a major in electronic component packaging. Package-level thermal design is closely related to the circuit design and structural design of the device. Proper selection of PCB substrates is an important part of package-level thermal design. The type and characteristics of copper clad laminates are the items of concern to PCB design and manufacturing process personnel. In addition to the general requirements for strength, insulation, and dielectric coefficient, there are special requirements for the thermal properties of copper clad laminates. The thermal performance of copper clad laminates has two aspects.
(1) Temperature resistance of copper clad laminates. The epoxy glass cloth copper clad laminate has excellent electrical properties and chemical stability, and the working temperature is -230 ° C to 260 ° C. In addition to the above-mentioned excellent properties, the polyimide copper clad laminate has the characteristics of small dielectric constant and small signal transmission delay.
(2) Thermal conductivity of copper clad laminates. A material with high temperature resistance and high thermal conductivity is selected as the material of the PCB. Under the same conditions, the temperature of the epoxy glass cloth laminate pattern wire can be increased by 40 ° C, while the metal core PCB pattern wire temperature rises less than 20 ° C, so the metal core PCB has been widely used in electronic equipment.
The various components of the electronic device are composed of components of various materials, such as silicon chips, silicon oxide insulating films, aluminum interconnects, metal lead frames, and plastic package housings. These materials have different coefficients of thermal expansion. Once temperature changes are encountered, compressive or tensile stresses are generated at the interface of different materials, thus creating a thermal mismatch stress, referred to as thermal stress. Mismatch in thermal properties of materials is an internal cause of thermal stress, which is an external cause of thermal stress.
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