MIL-PRF-19500-420 Semiconductor Device, Diode, Silicon, Power, Rectifier, Types 1N5550 Through 1N5554, 1N5550Us Through 1N5554Us, Jan, Jantx, Jantxv, Jans, Janhca, Janhcb, Janhcc, Janhcd, Janhce, Jankca, Jankcd, And JankceThis specification covers the performance requirements for silicon, general purpose, semiconductor diodes. The diode is non cavity double plug construction, with high temperature metallurgical bonds \(category 1\) between both sides of the silicon die and terminal pins. Four levels of product assurance are provided for each encapsulated device type as specified in MIL-PRF-19500. Two levels of product assurance are provided for each unencapsulated device type.

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MIL-PRF-19500/420M

6.5.1 PCB mounting with FR4 material for full 3 amp IO. For a PCB mounting example with FR4 material

where the full 3 amp IO rating (half-sine-wave) is used at a TJ of 175�C and ambient temperature of 55�C, the

following steps guide the user in what the PCB pad size will need to be with 1 oz, 2 oz, and 3 oz copper.

For axial-leaded, the lead length for mounting will be .187 inch (4.76 mm) or less from body to entry point on

PCB surface.

Use the IO versus Po curve on figure 13 to look up 3 amps (X-axis) and follow up to the TJ =175�C

curve (lower) for 2.55 watts.

Calculate maximum thermal resistance needed (175�C - 55�C) / 2.55 W = 47�C/W.

Look up thermal resistance of 47�C/W on Y-axis using a thermal resistance versus pad area plot on

one of the three curves on figure 14 for different weights of copper cladding and then intersect

curve horizontally to get answer. These curves assume still air, horizontal position.

In this example, the answer is: 1 oz PCB = .75 in X .75 in (19.05 mm X 19.05 mm), 2 oz PCB = .43 in x .43

in (10.92 mm X 10.92 mm), 3 oz PCB = .29 in X .29 in (7.36 mm X 7.36 mm) for each pad.

Add a conservative guard-band to the pad size (larger) to keep TJ below 175�C.

6.5.2 PCB mounting with FR4 material for 1 amp IO. For a PCB mounting example with FR4 material to support a

1 amp IO square wave switching at a 0.50 duty factor (50 percent duty cycle) at TJ = 100�C and ambient temperature

of 55�C, the following steps guide the user in what the PCB pad size will need to be with 1 oz, 2 oz, and 3 oz copper.

Find size of copper pads on standard FR4 PCB to support operation at 1 amp IO square wave switching at a

0.50 duty factor (50 percent duty cycle) at TJ = 100�C with TA = 55�C.

Calculate peak IF = 1A / 0.50 duty factor = 2 amps.

Use the VF versus IF curve on figure 15 to look up IF = 2 A (Y-axis) and follow across to the TJ = 100�C curve

(middle) for VF = 0.81 V.

Calculate power = IF x VF x duty factor = 2 x 0.81 x 0.50 = 0.81 W.

Calculate maximum thermal resistance needed (100�C - 55�C) / 0.81 W = 56�C/W.

Look up thermal resistance of 56�C/W on the Y-axis using a thermal resistance versus pad area plot on one

of the three curves on figure 14 for different weights of copper cladding and then intersect curve horizontally

to get answer. Curves assume still air, horizontal position.

In this example, the answer is: 1oz PCB = .45 in X .45 in (11.43 mm x 11.43 mm), 2oz PCB = .25 in x .25 in

(6.35 mm x 6.35 mm), 3oz PCB = .17 in X .17 in (4.32 mm x 4.32 mm) for each pad.

A conservative pad guard-band is optional since TJ is only 100�C. NOTE: With multilayer PCBs, forced air

cooling will improve performance. Closed confinement of the PCB will do the opposite. Please use sound

thermal management.