Packages thermal resistance

Table A-3 Typical Surface Mount Package Thermal Resistances...

Eoamed polystyrene sheet has exceUent strength, thermal resistance, formabUity, and shock resistance, as weU as low density. It is widely known for its use in beverage cups, food containers, building insulation panels, and shock absorbent packaging. Polystyrene products can be recycled if suitable coUection methods are estabUshed. Eoamed polystyrene sheet can also be easily therm oformed (see Styrene plastics). 

Table A-2 Thermal Resistances of Common Thru-hole Power Packages...

As one can see by the typical values of the junction-to-air thermal resistance, it doesn t require much power to result in very high junction temperatures. If the designer can possible mount the power package on any metal surface to increase the radiating surface area, it will only improve the junction temperature. 

Packaging and multilayer barrier films produced from COC materials exhibit improved moisture and thermal resistance. Thus, they are suitable for... 

Indirect liquid cooling (cold plate) More efficient than thermal conduction Require pump to overcome overall pressure drop in the loop Require low thermal resistance packaging at component level... 

Note that the packages shown in Fig. 1.21 do not use active cooling (fan cooling). Heatsinks with cooling fins and fan are commonly used to cool electronic microchips including Si CMOS microprocessors. They have thermal resistances < 0.5 K/W. The use of active cooling devices would reduce the power efficiency of LED-based systems and are therefore not used. 

Fig. 1.21 Thermal resistance of LED packages (a) 5 mm (b) low-profile (c) low-profile with extended lead frame (d) heatsink slug (e) heatsink slug mounted on printed circuit board (PCB). Trade names for these packages are Piranha ((b) and (c), Hewlett Packard Corp.), Barracuda ((d) and (e), Lumileds Corp.), and Dragon ((d) and (e), Osram Opto Semiconductors Corp.) (adopted from ref. [69]).

Numerical simulations of the junction temperature increase of a laser diode array have been performed for a package configuration as illustrated in Fig. 33. Calculations have been performed with and without a CVD diamond heat-spreader. The decrease in thermal resistance has been calculated for different values of the heat-spreader thickness, depth and thermal conductivity. The simulations have been performed for an array of laser diodes which are individually 200 pm wide... 

FIGURE 1.1.3 Thermal resistance as a function of thermal conductivity for packages measuring... 

Figure 1.1.5 shows the thermal resistance (0j-a) of other packages (OD 30, 40 and 50 mm thickness 1.0 mm power consumption 3 W) as a function of thermal conductivity. In this example, two AI2O3 ceramics are included. The thermal resistance of these packages decreases with increasing package size. 

The thermal resistance of AN75W packages is comparable to that measured on packages produced from high TC AlN, especially for small outline packages mounted on PWB. 

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