Schottky diode, how would you assess this?

[Seekonk]

I use a 15A 45V 15SQ045 diode for some low voltage application in solar. Just got some 20SQ050 to evaluate (they were free). Both are made by PSC.  As a general rule I figure the higher you go in rated voltage, the higher the forward voltage would be.  I tested both diodes in series with thermal breaks to prevent heating effects. The 15A diodes at 7A were about 0.304V and the 20A diodes were about 0.354V.  A little higher difference than I would have expected, but thought a voltage breakdown test might explain that.  The leakage test was done at room temperature.  The 15A 45V diodes had 1ma of leakage between 57 and 61V with the majority being 60V or above.  The 20A 50V diodes were between 54 and 63V with the majority being 60V or below.   I though, lets heat them up with 7A for a while.  The 15A 45V diodes had 1ma of leakage hot between 55 and 60V.  The 20A 50V diodes hot were between 35V and 44V.

Why would anyone select these 20A diodes.  Is this just marketing hype or are they fake.  The data doesn't make any sense to me. The 20A diode meets spec, the 45V just seems to do a lot better.

[Marco]

PSC?

I see 15SQ045 from SMC and 20SQ050 from HY Electronic, a Taiwanese+Chinese conglomerate.

[iMo]

..As a general rule I figure the higher you go in rated voltage, the higher the forward voltage would be.

Afaik the general rule is the the higher current rating (higher current density) the higher the forward voltage drop..

[DavidAlfa]

Similar question to why would anyone buy/sell 1N4001, 4002, 4003, 4004, 4005, 4006... When the 4007 is basically the same thing, standing higher voltage and much more widely used?
Why don't they simply sell the 4007 alone, removing the extra work from handling 7 products to just one ?

[BrokenYugo]

Similar question to why would anyone buy/sell 1N4001, 4002, 4003, 4004, 4005, 4006... When the 4007 is basically the same thing, standing higher voltage and much more widely used?
Why don't they simply sell the 4007 alone, removing the extra work from handling 7 products to just one ?

Depending on the datasheet I think the whole range is one or two processes, where they make nothing but 1N4007 and maybe 1N4004. The lower spec parts are just derated 4004/4007. I guess they do this for regulated legacy design stuff where making any change requires a lot of work. Nobody in their right mind would specify a 1N4005 unless they were required to, may as well just use the jellybean 1N4007.

[MarkT]

..As a general rule I figure the higher you go in rated voltage, the higher the forward voltage would be.

Afaik the general rule is the the higher current rating (higher current density) the higher the forward voltage drop..

As a general rule the higher the current spec the larger the device, so there's no requirement of current density to depend on current rating.

I think you'd have to do a multidimensional plot of device specs for a large variety of devices to spot any trends.  Add cost as one dimension of course!

[Vovk_Z]

Afaik the general rule is the the higher current rating (higher current density) the higher the forward voltage drop..

No. Voltage drop depends on a current but not on a current limit. And the large the current - the larger the voltage drop, proportionally to a current flow.

[Vovk_Z]

Why would anyone select these 20A diodes.  Is this just marketing hype or are they fake.  The data doesn't make any sense to me. The 20A diode meets spec, the 45V just seems to do a lot better.

There is better semiconductors and worse semiconductors. The only a bit strange thing is here that they are from the same manufacturer.

[Marco]

What manufacturer? Is PSC short for something everyone but me knows?

[Vovk_Z]

As I could google PSC is Panjit Semi Conductors.

[Smokey]

I said this recently in another thread too, but when I'm buying parts from digikey some of these new companies I've never heard of still sketch me out a little bit. 
I wonder sometimes what the policies are at big engineering companies with real engineering departments these days. 

[Marco]

I'd never really seen Panjit called PSC.

15SQ045/20SQ050 are generic names for P600/R6 packaged diodes which Panjit doesn't seem to sell. In fact the only active device Panjit has in that package is SB1545S.

[Konkedout]

I have been designing power supplies since 1980, and I see a few good but many not-so-good answers to this question.  I have not heard of PSC semiconductors.

For schottky diodes, the voltage rating is by far most important.  Current rating will depend heavily on temperature and cooling.

There are different schottky diode technologies.  Chromium barrier, Platinum barrier, and Silicon Carbide (much newer) to name a few.  Guard ring protection reduces the chances of sudden failure due to reverse overvoltage.

If you want to study specifications go with an established manufacturer such as ON or Vishay or Diodes Inc.  Buy some cheapies if you want but I would not start out with those.

As for 1N4001-1N4007 what was said is mostly correct.  Those parts have been around since the stone age.  (exaggerating a little.)  Correct that there is no functional advantage to the lower voltage types.  I believe that when these parts were introduced, the processing and production yield was not as good, so it was easier to make a 1N4001 than a 1N4007 and the price differed accordingly.

[tooki]

Similar question to why would anyone buy/sell 1N4001, 4002, 4003, 4004, 4005, 4006... When the 4007 is basically the same thing, standing higher voltage and much more widely used?
Why don't they simply sell the 4007 alone, removing the extra work from handling 7 products to just one ?

This has been discussed in detail in other threads, like https://www.eevblog.com/forum/beginners/diodes-1n4001-1n4007-are-they-really-all-different/

In a nutshell: depending on manufacturer, they may not be manufactured using the same process, so for some manufacturers, other characteristics may vary. Not really relevant for their intended use as low frequency rectifiers, but becomes interesting when using them for nonstandard purposes.