In this issue, we examine heat flow in a printed circuit board (PCB), which typically is a layered composite consisting of copper foil and a glass-reinforced polymer (FR-4). A cross-sectional view of such a laminated structure is illustrated in Figure 1. The Figure indicates the numbering system that will be used for indicating the different layers, numbered 1 through to … [Read more...]
Thermal interface under a plastic quad flat pack
Introduction Plastic components are designed so that the heat is dissipated by forced or natural convection. The use of plastic packages under conditions where neither cooling method is available introduces new challenges. High heat-dissipation plastic packages require a large-area solid heat sink in order to transfer the heat into the copper thermal lands on the printed … [Read more...]
The thermal conductivity of silicon
The most important material within the semiconductor industry is Silicon. When dealing with electro-thermal device modelling, or the interpretation of fast transient techniques for the measurement of thermal impedance, thermal conductivity of Silicon is required. For steady state thermal analyses at the board and system level, however, accurate values are not required, because … [Read more...]
The coefficient of thermal expansion
This is the second technical data feature that deals with the coefficient of thermal expansion (CTE). The first technical data feature, incorporated in the September 1997 issue, covered semiconductor materials, leadframes and solder alloys. This issue will discuss the temperature dependence of the CTE and present data on other materials that are of importance to electronic … [Read more...]
Measuring fluid velocity in electronic enclosures
Thermal analysis and characterization of electronic systems requires a knowledge of fluid velocity. In pursuit of this information, we often resort to measurement or calculation. The issue of measurement becomes a challenge since we are dealing with rather complex flows that tend to be highly nonisothermal. Therefore, it is our intention in this article to highlight the need … [Read more...]
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