About thermal cooling/ heat generation, thermal resistance, temperature rise, and thermal design of chips
The power loss of a chip, on the one hand, refers to the difference between the effective input power and output power, which is called dissipated power. This part of the loss will be converted into heat release, and heating is not a good thing, which will reduce the reliability of components and equipment, and seriously damage the chip. Power Dissipation, also known as Power Dissipation, is a parameter in the SPEC of certain chips, which refers to the maximum allowable dissipation power. The dissipation power corresponds to heat, and the larger the allowable dissipation power, the higher the corresponding junction temperature.
The temperature rise of a chip is relative to the ambient temperature (25 ℃), so the concept of thermal resistance has to be mentioned. Thermal resistance refers to the ratio between the temperature difference at both ends of an object and the power of the heat source when heat is transmitted to the object, expressed in ℃/W or K/W.
As shown in the figure below, when a chip is soldered onto a PCB board, there are three main ways for the chip to dissipate heat, corresponding to three types of thermal resistance.
1) The thermal resistance from the inside of the chip to the shell and pins - the chip is fixed and cannot be changed.
2) The thermal resistance from chip pins to PCB board - determined by good soldering and PCB board.
3) The thermal resistance from the chip casing to the air is determined by the heat sink and the peripheral space of the chip.
When the thermal resistance is constant, the lower the power consumption, the lower the temperature. Under a certain power consumption, the smaller the thermal resistance, the better. A smaller thermal resistance represents better heat dissipation.
