Lead length

As one eaii see, the thermal parameters define a physieally different situation. For a radial-leaded diode, the heat ean only be eondueted from the die, via the leads. The thermal resistanee would then ehange as a funetion of lead-length and is published this way in data sheets. The thermal expression (see Figure A-6a) is... 

This is for the typieal PC board-mounted applieation where only the PC board traees are used to eonduet the heat away from the diode. The typieal value range of the lead-to-air thermal resistanee is between 30 to 40°CAV and is a variable whieh is dependent on the lead length. 

As shown by Fig. 6.23, the channel geometry is relatively complicated for barrier flight melting sections. The geometric constraint on the channel widths are provided by Fq. 6.33. For most commercial designs, W is constant because the lead length of the primary flight is also constant. 

Figure 6.23 Schematic for the position of the barrier flight via the width of the solids channel [W,) and the depths of the solids and melt channels a) a barrier section design with a continuously decreasing /V b) constant-width solids channel, and c) a hybrid design. The designs all utilize a constant lead length for the primary flight...

Figure 7.25 correction factors as a function of W/iVfor single-flighted screws with square-pitched lead lengths (14/D = 0.85)... 

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