source:power adapter Popular:adapter release time:2021-11-11 09:16:02 Article author:sznbone
The early industrial standards for heat transfer in power adapters were mainly semi-standards, which stipulated the test standards for IC packaging in natural convection, wind tunnel, and infinite flat panel test environments.
Since 1990, the JEDECJC51 committee has invited manufacturers and experts to start formulating new industrial standards for heat transfer, some of which are related to thermal management. Compared with the semi-standard, the new heat transfer industry standard has the same basic measurement methods and principles, but its content is more complete. In addition, some definitions are explained more clearly.
Two thermal resistance values are defined in the semi-standard: RJA and RJC. Among them, in natural convection or wind tunnel environments, RJA measures the heat transfer from the chip interface to the atmosphere. Since the measurement is carried out under standard and standardized conditions, different results can be used to qualitatively compare the convenience of package heat dissipation for different substrate designs and environmental conditions. RJC refers to the thermal resistance transferred from the chip interface to the integrated circuit package shell. The isothermal surface must be touched during measurement. This value is mainly used to evaluate the performance of the radiator.
With the change of packaging form, the new JEDEC standard adds RJB, φJT, JB and other measurement parameters. RJB is the thermal resistance from the chip interface to the test board, in an environment where almost all heat is transferred from the chip interface to the test board. This value can be used to evaluate the heat transfer efficiency of printed circuit boards. φJX is a heat transfer characteristic parameter, which is defined as follows.
(1) The definitions of _ and r are similar, but the difference is that _ refers to most heat transfer, and r refers to all heat transfer. When the actual electronic system is radiating, heat is transferred from the top and bottom of the package or even around it, and the heat is not necessarily unidirectional. Therefore, the definition of the package is more consistent with the measurement of the actual system. (2) jt refers to the thermal resistance generated when part of the heat is transferred from the chip interface to the upper case of the package. This value can be used to predict the chip interface temperature from the IC package surface temperature of the actual system product.
(3) JB is similar to RJB. RJB refers to the thermal resistance generated when part of the heat is transferred from the chip interface to the lower board in the natural convection and wind tunnel environment. It can be used to predict the joint temperature from the plate temperature.
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