1N4007, UF4007 diodes from aliexpress. - Page 1
Forum section: electronics / general

author: MasterT
author_rank: Frequent Contributor
timestamp: August 29, 2018, 01:32:53 am
content: I received UF4007, and noticed that leads doesn't match DO-41 package. 0.5 mm diameter instead of 0.7-0.9 mm. Searching through data sheet from different manufacturers I came to conclusion that nobody makes UF4007 in DO-35 or DO-7 cases.Digging up 1N4007, that I received a year ago I discovered that package is also wrong! I never think that someone would re-mark most common diode in the world.Same apply to HER107.Very likely diodes are counterfait, but how I can differentiate one from another? Leakage reverse current below 10 nA for all of them, and capacitance in the same range. I don't have fast pulse generator ( 1A, nsec) to verify fast recovery timing.For my application, uA high voltage power supply diodes lower current /power rating (0.5A instead of 1A or 500mW instead of 1W) is not an issue, only fast switching what is matter.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 29, 2018, 06:15:20 am
content: Do you have a signal generator? A square wave of modest speed should be able to tell 1N4007 apart.Tim

author: MasterT
author_rank: Frequent Contributor
timestamp: August 29, 2018, 07:01:15 am
content: Probably, I could sort out slow diodes, if there is any. I have a pulse generator (DDS) build-in my DSO4072, about 10 nsec or so rise time. Amplitude +-3.5V only.But "idea fix" is to measure recovery timing down to 10 nsec like it shown here:Googling around, I can't see any shortcut, seems it's industry standard to measure at 0.5A forward current switching to 1A - 0.25A in reverse. On 50 OHm in series it requires > 25V power supply, 12.5W thick film resistors (wirewound has too much inductance), and pulse driver about 1A capability. Probably, I could switch on and off forward current too, relaxing power dissipation on resistors, but in this case I need 2 fast switching drivers.Thinking mosfet gate driver TC4427 may works, though it up to 18V only, not 25.

author: xaxaxa
author_rank: Regular Contributor
timestamp: August 29, 2018, 08:15:40 am
content: put it in a boost converter at 100kHz, passing a few watts. 1n4007 will get hot real fast.

author: bd139
author_rank: Super Contributor
timestamp: August 29, 2018, 08:49:13 am
content: I'd just throw them away and buy some new ones from a reputable supplier. Nothing on Aliexpress can be treated at face value. So many problems.Had fake UF diodes before from there. I was trying to build an HT supply to drive an old CRT that needed +/-2KV bias. So I wound a nice transformer on an E core, tested that and all was good running at 30KHz. Connected a string of 4x UF4007's on each leg balanced with 1M resistors and one diode went open circuit instantly. Stuffed a new one in and a different one went pop. Found an old intensity pot I had and wired that up as a potential divider across the 2Kv to ground and connected diode across wiper to ground. Bloody things blew up at 350V.Ordered some from RS branded ON Semi. Worked right away, no problems at all. You get what you pay for.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 29, 2018, 10:57:59 am
content: FYI, you don't need to test at high current. Recovery is a surprisingly consistent phenomenon, like BJT hFE. It has no reason to be consistent, but by coincidence, it usually is.Example, 2N3904 B-C junction:You can see the generator isn't terrifically fast, 10 or 20ns, and probably 50ns would do. Even slower for a general purpose diode (t_rr ~ 2us!).And B-E:This difference, by the way, arises because the B-E junction is more heavily doped. This gives lower Veb (about 7V, versus Vcb >= 60V), and higher hFE. High speed diodes go one further, adding defects with irradiation, and killing carrier lifetime with metal doping (usually gold and platinum). This reduces recovery time, at the expense of Vrrm (but not as much expense as going to heavy doping), and higher Vf. (Gold doped BJTs are around, like the PN2369, and 7400 series TTL.)Tim

author: MasterT
author_rank: Frequent Contributor
timestamp: August 29, 2018, 04:54:43 pm
content: This is what I came up with, simplified recovery time test jig. Driver TC4427, 1.5A, less than 10 nsec for load <100pF.Forward current close to standard, 0.5A, reverse voltage (~5V) and reverse current (0.5A) is lower. My understanding that having both V & A parameters below specification would increase recovery time, since voltage play big role in "extraction" minority carriers. What interesting, not much, I get pretty good data compare to data sheet.Test results (nsec) Data sheet1N4007 - 5000 unspecified.FR107 - 560 500UF4007 - 140 75MUR160 -120 75Not bad at all, for such low price 3-7 cents.

author: splin
author_rank: Frequent Contributor
timestamp: August 30, 2018, 02:22:07 pm
content: Quote from: MasterT on August 29, 2018, 04:54:43 pmFor all those components? The TC4427 alone is over $1 from major distributers and 20 cents or so on AliExpress. Or were you valuing your time?

author: MasterT
author_rank: Frequent Contributor
timestamp: August 30, 2018, 04:23:26 pm
content: Quote from: splin on August 30, 2018, 02:22:07 pmI mean 3-7 cents per single fast switching diode from aliexpr. Mouser is selling ~40 cents CAD each. I'll buy genuine UF4007 and run tests ones more to see if there is noticeable difference.

author: thm_w
author_rank: Super Contributor
timestamp: August 30, 2018, 08:59:40 pm
content: LCSC is another option, it will be genuine but the manufacturers are not big names here in NA:https://lcsc.com/search?q=UF4007%201-4c per diode.Its possible that is what you got from alix already.

author: MasterT
author_rank: Frequent Contributor
timestamp: September 04, 2018, 07:18:36 pm
content: After 3 days waiting time I received my package. Original UF4007, case DO-41, with right leads dimension and manufacturer logo. I also get IXDN614 (14A !) mosfet driver, to follow recommended 0.5A / 1A current with better precision.Interesting, diodes from aliexpress are faster