They almost certainly did specify a Schottky with an appropriate leakage spec. The problem wasn't the spec -- it was that the leakage increased beyond spec over time. More things can go wrong with the metal-to-semiconductor interface of a Schottky than for a regular diode, where there is continuity of crystalline order in going from P to N.? Likely HP had low confidence that they could find Schottkys with trustworthy aging behavior, so went the easy route and chose standard PN junction diodes as a replacement. Even the 1N914/4148 (quite leaky compared to other junction diodes) has much lower leakage than a Schottky with an equivalent forward current rating. Time-related reverse current increases in a junction diode are rarer and more moderate (unless the diode is abused or fabbed in an unclean environment).
-- Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 9/2/2024 3:32 AM, Edward Prest wrote:
That's what they say - but why go to? a 'regular' diode?? And go from 0.3 to 0.7 fwd drop. A better replacement would be a schottky with a low leakage spec.
