SMA connector male for 1.19mm semi-rigid cable

Release：IBH Advance Material Technology Data：2022/03/17

Heat energy is transferred from regions of high temperature to regions of low temperature via three basic mechanisms; radiation, conduction and convection.

Radiation. Electromagnetic transfer of heat between masses at different temperatures.

Conduction. Transfer of heat through a solid medium.

Convection. Transfer of heat through the medium of a fluid; typically air.

All three of these heat transfer mechanisms are active to some degree in every application. Convection will be the dominant heat transfer mechanism in most applications. Nondominant effects will provide an added contribution to cooling; in some cases, however, they may result in undesirable and unanticipated thermal interactions between components and subassemblies. All three of these mechanisms should be given consideration when developing a successful cooling strategy.

RADIATION

Radiant heat transfer occurs continuously between objects at different temperatures that are exposed to each other.

The net effect on the temperature of an individual part is dependent on a great many factors, including its temperature relative to other parts, relative part orientations, surface finishes and spacing. The difficulty in quantifying many of these factors, combined with the universal presence of radiant energy exchange, makes calculation of radiational temperature effects both a complex and generally imprecise task.

Temperature differentials encountered in practical applications of Vicor converters are never large enough to cause radiational cooling to be the dominant heat transfer mechanism. Radiation will account for less than 10% of total heat transfer in the majority of cases. For these reasons, the presence of radiant cooling is often assumed to provide safety margins over and above the dominant cooling mechanism, and detailed consideration of its effects are neglected. A valid assumption, in most cases, is that the converter will be warmer than its surroundings and radiant energy transfer will aid cooling.

In some cases, however, nearby objects (PC boards, power resistors, etc.) may be much hotter than the converter and net radiant energy transfer may actually increase the converter’s temperature.

Surveying the relative positions and estimated temperatures of converters and surrounding parts is advisable as a means of anticipating the potential effects of radiant transfer. In cases where hot components are in close proximity to the converter, the use of interposing barriers can generally moderate undesirable radiational heating effects.

CONDUCTION

In most applications, heat will be conducted from the baseplate into an attached heat sink or heat conducting member. Heat conducted across the interface between the baseplate and mating member will result in a temperature drop which must be controlled. As shown in Figure 20–2, the interface can be modeled as a “thermal resistance” in series with the dissipated power flow. The baseplate temperature will be the sum of the temperature rise in the interface and the temperature of the member to which

the baseplate is attached.

Temperature rise across a surface interface can be significant if not controlled. The area of the interface should be as large as possible, and the surface flatness of the attached member should be within 5 mils. Thermal compound or a thermal pad should be used to fill surface irregularities. Thermal resistance across surface interfaces can be held to under 0.1˚C/Watt with proper measures.

CONVECTION

Convective heat transfer into air is a common method for cooling Vicor converters. “Free” or “natural” convection refers to heat transfer from a dissipative surface into a cooler surrounding mass of otherwise still air; forced convection refers to heat transfer into a moving air stream.

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