Diodes - die pictures - Page 1
Forum section: electronics / projects

author: Noopy
author_rank: Super Contributor
timestamp: June 04, 2021, 11:40:09 am
content: In this topic I will post pictures of diodes. You can find the overview here:https://www.richis-lab.de/Diode.htmI have already a BAV45 (https://www.richis-lab.de/Diode01.htm) and a lot of zenerdiodes in the voltage reference section (https://www.richis-lab.de/REF00.htm).Today 1N4007, everybody knows it.1000V / 1AThe die is protected with some white potting.The die is 0,2mm thick.0,93mm x 0,95mmBoth surfaces are completely covered with tin.That is an interesting picture. On the side of the die there is an unsteady crossover (upper part is 0,04mm, lower part is 0,13mm). I assume that is the border of an epitaxial layer. I assume there was an n+ wafer then they added an epitaxial n layer to get high voltage ratings and then they added a p layer. Either they diffused the p doping or there was another epitaxial step. At the lower end of the die edge there could be another unsteady crossover. Can´t be sure...https://www.richis-lab.de/Diode02.htm

author: RoGeorge
author_rank: Super Contributor
timestamp: June 04, 2021, 02:56:52 pm
content: Thank you, subscribed!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 04, 2021, 09:13:46 pm
content: Drop it in acid, see if there's any patterning on top?I suspect old diodes like those, won't have much (probably just guard rings?), but some power schottky are made with fine cells like MOSFETs. Should be interesting to see.Tim

author: Noopy
author_rank: Super Contributor
timestamp: June 05, 2021, 12:24:46 am
content: Quote from: T3sl4co1l on June 04, 2021, 09:13:46 pmGood idea!Unfortunately I have lost the die.Will have to decap one more 1N4007.Quote from: T3sl4co1l on June 04, 2021, 09:13:46 pmI´m pretty sure the 1N4007 has nothing like that.I have taken pictures of two IGBTs and their freewheeling diodes:International Rectifier IRG4PH40Khttps://www.richis-lab.de/Bipolar35.htmIXYS IXGH48N60C3D1https://www.richis-lab.de/Bipolar26.htmAnd of course the darlington power modules:Powerex KD324510https://www.richis-lab.de/Bipolar19.htmGleichrichterwerk Stahnsdorf SU510https://www.richis-lab.de/Bipolar24.htmBut I will have to get a power schottky...

author: David Hess
author_rank: Super Contributor
timestamp: June 05, 2021, 02:32:12 am
content: High voltage diodes like the 1N4007 usually have a PIN structure but I do not know that it will be apparent. They can work in place of dedicated RF PIN diodes.

author: Noopy
author_rank: Super Contributor
timestamp: June 05, 2021, 06:12:54 am
content: Quote from: David Hess on June 05, 2021, 02:32:12 amThat is what I wanted to say with the epitaxial n layer. As far as I'm informed the i-region often is not intrinsic but ligthly n-doped.I'm not sure about the visual aspect either. In theory the crystal junction shouldn't be visible but in practice the world often isn't perfect.I don't think the crossover is caused by the die separation. It's too unsteady.

author: Noopy
author_rank: Super Contributor
timestamp: July 22, 2021, 07:33:55 pm
content: exe wanted to see a FERD (Field Effect Rectifier Diode). Finally I have taken some pictures of a ST Microelectronics FD40H100.The die is connected with four quite big bondwires and the die is 0,2mm thick.I killed round about ten diodes to get one complete die! After burning the epoxy the remaining stuff is still quite stiff. It seems like the die is desoldered and lifted a little while being in the furnance. When you remove the package remainings the bondwires tend to break the die.3,8mm x 3,4mmThe metal layer is very clean. You see no structures except a trench at the edge of the die.But let´s remove the metal layer...Hey, there are more structures! I don´t think they planed the surfaces. I assume the metal layer is thick enough to cover the unevenness.In a power MOSFET you often find small square transistors (https://www.richis-lab.de/FET07.htm) or thin transistor stripes (https://www.richis-lab.de/FET15.htm). Here it looks like we have staircase-shaped MOSFETs with quite big structures.I assume the bright parts are contact areas to the metal layer.It looks like the other "staircases" are the gate areas connected to the frame of the structure.That sound reasonable: Source is connected over a large area and gate is connected around the frame of the structure.https://www.richis-lab.de/Diode03.htm

author: Noopy
author_rank: Super Contributor
timestamp: August 05, 2021, 04:10:38 am
content: Diotec BY550-50, a standard rectifier that can conduct up to 5A and block up to 50V. There are bigger versions blocking up to 1000V.That looks quite similar to the 1N4007 but there are additional metal discs between the die and the contacts.The edge length of the die is 2,3mm. That gives you 0,95A/mm² while the 1N4007 works with 1,13A/mm².The die is 0,26mm thick and seems to consist of two layers (0,06mm/0,20mm). Probably the die is manufactured epitaxial.https://www.richis-lab.de/Diode04.htm

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 05, 2021, 07:34:39 am
content: Quote from: Noopy on July 22, 2021, 07:33:55 pmInteresting stuff to see, thanks 🖤I just wonder why even ST did not tell switching characteristics in the datasheet. Are they so ashamed of how bad it really is?

author: Noopy
author_rank: Super Contributor
timestamp: August 05, 2021, 08:14:52 am
content: Quote from: Miyuki on August 05, 2021, 07:34:39 amIt is a pleasure! I have some more interesting diodes here... ...more interesting than the 1N4007.Yeah, it seems the switching characteristic of the FERD is nothing you want to promote.

author: Noopy
author_rank: Super Contributor
timestamp: December 05, 2021, 04:47:40 am
content: We need pictures of a point-contact diode! Let´s take a look into a OA741 built by the Werk für Fernsehelektronik Berlin.You can scrape off the label.One of the connection pins is surrounded by solder, on which a thin germanium crystal is located. A gold wire contacts the crystal from above. The curve described by the wire ensures that the wire maintains contact with the crystal during production.The tip diode is a Schottky diode. The active area results from the contact of the metallic tip with the semiconductor material. Ultimately this is an advancement of the open crystal detectors used as demodulators in old radio receivers.The crystal is about 80µm thick. The edge length is 1,3mm. The special surface structure resulted from the etching process which was used to remove imperfections from the surface of the crystal.The gold wire has a diameter of about 0.04mm. It is fused with the semiconductor crystal. To fuse the wire a high current is conducted through the diode which strongly heats the junction. Even without a fused contact a Shottky diode junction is formed at the contact point of the gold wire but the stability and current-carrying capacity are lower. Point-contact diodes that are not welded however offer lower junction capacitances which is why they are used as HF diodes.https://www.richis-lab.de/Diode05.htm

author: RoGeorge
author_rank: Super Contributor
timestamp: December 05, 2021, 11:16:01 am
content: What's all those triangle-shaped bumps on the Ge crystal?Isn't the surface supposed to be mirror clean, like a Si wafer?

author: Noopy
author_rank: Super Contributor
timestamp: December 05, 2021, 11:21:52 am
content: Back in the days the etching process wasn't as good as today. But it was ok. Eventually the diode is just were the gold wire is welded onto the crystal that was quite a rude process/diode type.Edit: But to be honest I don't know where the structure comes from. Crystal lattice?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 05, 2021, 04:37:21 pm
content: I would guess potassium hydroxide etch, it's anisotropic at least in silicon, tending to make pyramidal pits -- with respect to whatever crystal plane is commonly used, of course. If that's the case, then it appears they:1. Cut along a crystal plane parallel to one of those pyramid faces,2. Etched long enough that the pit size became quite exaggerated, enough to see on magnification.And if that's all the case, apparently also the etching process doesn't interrupt itself, so tends to maintain the faceted appearance?Were those awfully rugged, then? I can't imagine e.g. dumping a capacitor into a common diode today and getting anything but a short circuit (or an open circuit, at higher energy levels). I suppose a schottky junction is still a short circuit, of sorts, but a practical one as it just so happens!Tim

author: Noopy
author_rank: Super Contributor
timestamp: December 05, 2021, 04:54:36 pm
content: Well these point contact diodes were rugged with respect to the open crystal detectors in the old radios.It´s interesting that science isn´t sure about the nature of these fused junction:Some state the tip forms a p-junction. But gold is nothing to dope germanium so that doesn´t sound reasonable.Some state the melting and recrystallization develops p-doping. But no one explains how that should be possible.Some state it´s still a Schottky junction. That´s also my opinion.

author: Noopy
author_rank: Super Contributor
timestamp: December 05, 2021, 09:51:29 pm
content: I got a special teaching document used in the Werk für Fernsehelektronik which explains these point contact diodes and now I have to correct myself:It seems like the welding of the gold wire really generates a p-doped area in the n-doped crystal. I still don´t understand how that works on an atomic level.In addition the document describes that they added 1% gallium to the gold wire. The gallium diffuses into the germanium and gives you an additional p-doping.BTW: The document describes two types of etching agents for cleaning the germanium surface:- nitric acid, hydrofluoric acid, acetic acid and potassium bromide- hydrogen peroxide, hydrofluoric acid and deionized waterDoesn´t sound healthy like always in the semiconductor industry.

author: Gyro
author_rank: Super Contributor
timestamp: December 05, 2021, 10:24:17 pm
content: Quote from: Noopy on December 05, 2021, 04:47:40 amThis puts me in mind of a very old article (maybe an early Practical Wireless) on constructing your own transistor.Irrc, it used a small ebonite knob as the basic framework, and the guts from two Germanium point contact diodes. Both diodes were carefully cracked open and the crystal and lead of one of them glued into the centre hole, the wire being the base connection. The two other leads, with their point contact wires still attached were then screw tag attached at each side of the hole and bent so that their point contacts were brought into spring contact with the surface of the Germanium crystal - as close together as possible and physically separated by a thin sliver of Mica, again glued to the edge of the hole.I don't remember the 'forming' details clearly, but it involved passing current through one of the point contact wires until it reached red heat, presumably locally modifying the doping of the crystal to some fairly shallow depth. Irrc, this process was repeated several times until the desired (some?) gain, ... or total failure, was achieved.I don't remember the year of the article, but it must have been at the point where transistors were rather expensive relative to Germanium diodes... or it was for masochistic readers!I'd love to find the article again. Maybe it's hidden away somewhere in the americanradiohistory archive - if I had a better idea where to look.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 06, 2021, 06:24:49 am
content: Gold shouldn't do anything by itself, other than kill carrier lifetime I think (at least, that's the effect in Si), which probably doesn't have much effect here other than perhaps reducing the reverse breakdown voltage. Some germanium will end up alloyed into it I think, but that's not very important, it'll still be largely metallic.Gallium, that makes sense. And it doesn't take much, so yeah.Oh wait, for schottky diodes, all that's needed is a doped substrate -- the contact potential with the metal is what makes the diode, doping isn't needed. Well, interesting then that the above could perhaps make a junction diode, albeit a rather thin one I think (given the heavy doping and short diffusion time)?I've certainly heard of alloy diodes/transistors -- using a whole blob of In, but not of using alloys in turn to do it.Tim

author: Noopy
author_rank: Super Contributor
timestamp: December 06, 2021, 07:04:17 am
content: Quote from: Gyro on December 05, 2021, 10:24:17 pmI have read similar stories.Quote from: T3sl4co1l on December 06, 2021, 06:24:49 amYes, without welding the parts together you have some kind of schottky diode.Quote from: T3sl4co1l on December 06, 2021, 06:24:49 amA thin one, yes.The document I have here states that the welding process was done with 0,6A-1,2A for 0,2s.

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 12, 2021, 08:17:05 pm
content: Quote from: Gyro on December 05, 2021, 10:24:17 pmI've seen it before to and tracked it down, January 1954 issue. Good scan here:http://www.douglas-self.com/ampins/wwarchive/wwarchive.htm#homeWhole magazine scan here:https://worldradiohistory.com/UK/Wireless-World/50s/Wireless-World-1954-01-S-OCR.pdfarticle on PDF page 24.

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2021, 08:52:01 pm
content: Thank you! It's ages since I last saw that (in paper form from a long dead neighbour!) - quite nostalgic.

author: Noopy
author_rank: Super Contributor
timestamp: February 09, 2022, 11:19:37 am
content: We had the gold wire point-contact diode OA741 (https://www.richis-lab.de/Diode05.htm) now let´s take a look into a tungsten wire point-contact diode.Here we have a Д2Ж (D2Ž) built in the semiconductor plant Novosibirsk. The family D2 contains seven variants, the D2Ž has the highest breakdown voltage of 150V. The leakage current is 0,25mA. The maximum mean current flow is 8mA. The maximum peak current is 25mA.On the contact sheet there is a diode showing the current flow direction, the name Д2Ж and the logo of the semiconductor plant Novosibirsk. I don´t know what 1.70 means.It´s a glass housing with metal caps at both ends.The wire colour shows that it isn´t gold but probably tungsten. Sometimes the tungsten contains some dopant like aluminium.For proper pictures a higher glass uniformity would be nice.You can remove the caps at the ends. Under the caps there are shells in which they pushed cylinders carrying the germanium die and the point contact wire.The geometry of the wire guarantees a spring effect pushing the wire onto the die and compensating different thermal expansion.The tip of the wire is round about 30µm in diameter.The edge length of the die is 1,2mm. The structure on the surface is formed while the impurities are etched away.The wire was fused to the die. You can clearly see the molten germanium and the discoloration due to the heat generated in this process.The die is at least 200µm thick while the die in the OA741 was just 80µm thick. Perhaps that is due to the different voltage ratings (40V vs. 150V).The die sits on a round carrier that is put on the cylinder sitting in one of the shells of the package.There is a crack going from one side of the die to the other. Since the diode wasn´t in use it seems like the fuse process cracked the die due to the heat exposure.https://www.richis-lab.de/Diode06.htm

author: serg-el
author_rank: Regular Contributor
timestamp: February 10, 2022, 10:21:30 am
content: Quote from: Noopy on February 09, 2022, 11:19:37 amDate of manufacture.January 1970http://www.155la3.ru/d2.htm

author: Noopy
author_rank: Super Contributor
timestamp: February 10, 2022, 06:45:14 pm
content: Quote from: serg-el on February 10, 2022, 10:21:30 amYou are right!

author: exe
author_rank: Unknown
timestamp: February 18, 2022, 12:30:40 pm
content: Quote from: Noopy on August 05, 2021, 08:14:52 amHi there! FERD diodes are marketed as energy-efficient solution for switching regulators. Unfortunately, there is actual data on switching performance. I could only find on ST's website a comment from an ST's employee that they reasonably fast because they don't have pn junction, and they are more like schottky or mosfets or something like that (again, no specific numbers). I'm a big fan of FERD diodes, and I wanted to know the numbers. So, I decided to measure it myself.The setup is the following: AD2 generates bipolar square wave (+-1V), which is passed through the DUT (diode under test, haha) and 100 Ohm resistor. The yellow trace is from the siggen, the blue one is voltage across the resistor. The recovery is the positive spike on blue trace (ideally there should be none).As we can see, FERD diodes are significantly faster than 1n4004 (I measured FERD40U50CFP and FERD60M45CT). But there is one thing that troubles me. It seems on switching edges the voltage across resistor can exceed output of signal gen. I wonder if that is due to parasitic inductance. Unfortunately, I don't have shorter cables ready at hand, but let me know if it makes sense to re-do measurements with shorter cables.To confirm that I'm measuring recovery time and not something else, I also measured BAT41. It showed virtually no recovery. That small spike could be inductive kickback or something. After doing all the measurement I also tried MBR745, which is shottkey. And, guess what, I see some "recovery" on the plot. It's nowhere near as bad but still noticeable. I was puzzled.But then I realized that power diodes have quite some capacitance. So, I put back my trusty BAT41 and added 1n cap. Guess what, it started to look like MBR745 (1n is datasheet value for diode capacitance). With 3n cap (capacitance of FERD diodes) the waveform looked like a FERD diode in terms of "recovery".So, I'd say FERD diodes are fast, but have significant capacitance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 18, 2022, 01:38:52 pm
content: Think it would make sense to do it at higher signal level, or lower impedance. It's hard to tell recovery from capacitance at this scale; indeed you often see signal schottky diodes with "recovery" ratings, but it's basically just capacitance in the fixture (similar signal levels and resistance as this).The spike is relative to the previous baseline, as that's what the junction capacitance was charged to; so it can apparently overshoot the input by about Vf. Indeed, the 1N4004 generates voltage once charged, acting something like a microscopic battery -- exponential charge(Vf) curve included. Once its stored charge is released (or decays -- it's also a very leaky battery, t ~ 10us), voltage is free to swing to zero or reverse. (Its recovery can be modeled as a nonlinear capacitance, and indeed this is how SPICE does it.) The long "drool" tail is where recovery losses are dissipated -- some current continues to flow but the junction voltage is already reversed, thus dissipating quite large peak power, hence why these are unsuitable for high frequency application.When the device has capacitance, there is current flow in reverse, but only in relation to change in voltage (dV/dt). This is a subtle difference compared to a merely decreasing current, so it does indeed again look like recovery. The key is, the power spent in reverse recovery is reabsorbed on the forward swing -- capacitance is conservative. (It's dissipated in this circuit anyway, because the capacitance is dis/charged by the 100 ohm resistor; but if you measured the power in each component, you'd see it's absorbed by the resistor, not the diode. We can take advantage of this with an LC circuit, as in a resonant converter, where the capacitive energy can be recycled into the next phase and so on.) So it appears the FERD is capacitance-dominant.Note the 1N4004 has a not-quite-flat Vf at turn-on: it settles down very slightly. This is in part due to absorbing some extra charge -- the charge which is released during recovery. The excess Vf is known as forward recovery, and is usually quite minor, but can be problematic for some types against fast waveforms.Although the leads are quite long/loose, it appears risetime is modest in comparison, or the 100 ohm load is adequate damping; no inductive effects appear to be at play here. Just capacitive coupling.Tim

author: Noopy
author_rank: Super Contributor
timestamp: May 08, 2022, 12:27:06 pm
content: Let´s take a look into a tunnel diode! Here we have a Russian АИ201Г (AI201G) based on GaAs.The group AI201 is used for RF oscillators. AI101 is used for amplifiers and AI301 are used for fast switching.There are also GI30x diodes built with Ge. The GI308 is a special variant with a MESA structure.There is also a military version: 3I201GThe last letter is used for binning the diodes. A has a very low capacitance of 8pF max Л will burden your circuit with up to 50pF.In the datasheet there is an U/I graph showing the typical tunnel diode behaviour.The pn junction has a very high doping concentration. Due to this high doping at very low voltages electrons are tunneling through the junction leading to a fast rise of current (left part).At higher voltages the electric field stops this tunneling before the normal diode current occurs (right part).The two graphs are connected but due to the fast travelling from the left to the right part you often don´t see this part doing a curve trace.The current peaks up to 16-22mA at low voltages. The ratio of the first current peak to the following low current in the valley is a quality attribute for a tunnel diode. The datasheet specifies a Ip/Iv of 10 for the IA201G.The base element of the package is a ceramic cylinder with two metal elements at the ends acting a electrical contacts. The whole part is covered with a clear coating.The semiconductor crystal is placed on a notch in the anode contact. In this part the crystal is placed off-center.There is a wire connecting the crystal to the cathode which is torn off in this picture.The diameter of the wire is ~30µm. The end is sharpened to reduce the contact area.The edge length of the crystal is 0,7mm. The structure of the surface is due to etching which was done to remove impurities.The die thickness is 0,2mm. Since it isn´t placed in the middle of the package we can take a look at the bottom of the crystal.The pn junction must be highly doped in order to perform the function of a tunnel diode. For this reason, the junction cannot be constructed in the same way as for normal point-contact diodes. The high doping of a tunnel diode requires the direct alloying of an inverse doping agent, as it is done in alloy transistors. In the case of a tunnel diode, however, care must be taken to keep the alloying process short in order to produce as abrupt a pn transition as possible.At the same time, it is important to keep the parasitic capacitance of the pn junction low. The alloy pill seen here therefore has a diameter of just 25µm. To further reduce the capacitance, one can etch down the semiconductor crystal after the alloying process to create a MESA structure. The remaining pillar is then very thin and correspondingly sensitive to mechanical and electrical stress. The GI308 mentioned above uses such a structure.Another AI201G with a more acurate placed crystal. Here you can see how the bondwire is aranged.It looks like here the doping area is a little bigger (~40µm).This diode is placed on some kind of a socket.https://www.richis-lab.de/Diode07.htm

author: RoGeorge
author_rank: Super Contributor
timestamp: May 08, 2022, 01:00:15 pm
content: That's exactly how tunneling works!

author: Noopy
author_rank: Super Contributor
timestamp: May 08, 2022, 01:05:45 pm
content: Absolutely right: you have to be fast enough for tunneling!

author: Miyuki
author_rank: Frequent Contributor
timestamp: May 08, 2022, 02:46:27 pm
content: What causes them to "wear out" and lose parameters over time?It is some diffusion issue?

author: Noopy
author_rank: Super Contributor
timestamp: May 08, 2022, 03:03:57 pm
content: Quote from: Miyuki on May 08, 2022, 02:46:27 pmAs far as I know driving them at high currents (within the specs) degenerates the junction. The ultra high doping around the abrupt junction tends to mix to a rather normal junction.I have ordered one of these MESA type tunnel diodes. Their small area (high current density) made them especially sensitive.The alloy process was pretty tricky. Heating and cooling had to be very fast.

author: David Hess
author_rank: Super Contributor
timestamp: May 09, 2022, 06:51:12 am
content: Quote from: Noopy on May 08, 2022, 03:03:57 pmThen why do silicon tunnel diodes not degrade under the same conditions? Are they different in requiring a lower current density in operation?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 09, 2022, 07:05:38 am
content: Silicon diffuses slower at a given temp?Tim

author: Noopy
author_rank: Super Contributor
timestamp: May 09, 2022, 09:17:54 am
content: Silicon diffuses slower and I assume it´s also due to more modern technology.Back in the days there were no Si tunnel diodes, just GaAs and Ge and we know these old diodes are pretty touchy.Nowadays it seems like we can make everything possible and I´m sure there is some magic put into modern Si tunnel diodes.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 09, 2022, 01:52:07 pm
content: Diffusion in germanium is relatively fast. It is not just the tunnel diodes that wear out. Germanium transitors are also known for aging.Germanium detectors for gamma / X-ray spectroscopy even need cooling well below room temperature just for storrage.

author: Noopy
author_rank: Super Contributor
timestamp: June 07, 2022, 11:31:01 am
content: Just a small update regarding the point contact diode.Dr. Matthias Falter describes in his book "Dioden- und Transistortechnik" that due to surface effects in every n-doped semiconductor negative charges are pushed away from the surface. If you have a n-type semiconductor with some p-doping in it you automatically get an pn-junction.The fusing of the point contact diode amplifies the effect. I melts the Ge and the electric field moves n-dopant into the crystal while it moves p-dopant to the surface.https://www.richis-lab.de/Diode05.htm#Spitzendiode

author: Noopy
author_rank: Super Contributor
timestamp: November 02, 2022, 07:51:39 pm
content: You can find no direct information about the NT-1103. The designation indicates that the manufacturer was the German company Nortron. Datasheets still exist for a few diodes with similar designations. There are hints that the NT-1103 is a Zener diode with a Zener voltage of 3,9V. On the present model the breakdown voltage is 3,75V (5mA). The forward voltage is 0,64V (5mA).The structure appears quite crude. It is an n-doped silicon die alloyed with a piece of aluminum. The aluminum serves as a p-dopant, resulting in the desired pn structure.The silicon wafer is about 0,16mm thick. It is mounted on a metal plate, which in turn is soldered to the contact pin.The surface of the silicon wafer is very smooth also at the lateral edges. Apparently, it was subjected to an etching process after being cut into this shape. This cleans the surface and reduces the imperfections. At the front corner, however, a piece broke out afterwards.Finally, the diode was protected against the environmental conditions with a varnish.The contact area is located in a recess. The alloying of aluminum was not done with the large aluminum element. With such a large mass, it would be difficult to adjust the alloying process precisely and reproducibly. For this reason, an additional aluminum layer about 15µm high was deposited on the silicon surface instead, which was used for alloying. Later the large aluminum element was joined.https://www.richis-lab.de/Diode08.htm

author: Noopy
author_rank: Super Contributor
timestamp: November 11, 2022, 09:11:02 pm
content: S2 is the SMD marking of the varactor diode BBY40.We don´t know the manufacturer. The pinning shown here is taken from the NXP datasheet.The edge length of the die is 0,4mm. There are a lot of edges at the edges of the die.Perhaps that is due to the special doping distribution that is very important in a good varactor diode.I don´t know why there is just one round corner.https://www.richis-lab.de/Diode09.htm

author: Noopy
author_rank: Super Contributor
timestamp: January 08, 2023, 08:26:40 pm
content: Just a small ZD15, a 15V Z-diode.The semiconductor is cylindrical. On one side, it is connected flatly to one of the contact elements. On the other side, there is a thin metal pin between the semiconductor and the contact element.The sheet metal parts are surprisingly large. The curved contact could be intended to absorb thermomechanical stresses. The large surfaces should also improve heat dissipation.The semiconductor itself has a diameter of 0,9mm and a length of 0,8mm. The surface is rough and does not reveal any special structures.The surface on which the semiconductor is contacted by the metal pin is covered with a silicone-like material. No special structure can be seen at the junction. Thus, it remains unclear how exactly the Z-diode is constructed.https://www.richis-lab.de/Diode10.htm

author: iMo
author_rank: Super Contributor
timestamp: January 08, 2023, 08:39:30 pm
content: Isn't it a piston from Titanic's steam engine ?

author: RoGeorge
author_rank: Super Contributor
timestamp: January 08, 2023, 08:42:01 pm
content: Was the Zener working before decapping?

author: Noopy
author_rank: Super Contributor
timestamp: January 08, 2023, 08:51:01 pm
content: Quote from: imo on January 08, 2023, 08:39:30 pmIndeed!Quote from: RoGeorge on January 08, 2023, 08:42:01 pmI can´t tell with 100% certainty but it should have been ok before decapping.

author: Noopy
author_rank: Super Contributor
timestamp: January 08, 2023, 08:57:23 pm
content: Oh, wait a minute! I think I was wrong!I got this part from the Tele Quarz Group CCO 200:https://www.richis-lab.de/osc_03.htmBack then I wondered why the voltage rating of this Z-Diode is that high but now I think that is no zener but a tantalum capacitor with 15µF! That would explain why there is no junction...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 08, 2023, 09:20:07 pm
content: I mean... it'ssort ofa diode, right? It's polarized, right?Tim

author: Noopy
author_rank: Super Contributor
timestamp: January 08, 2023, 09:30:12 pm
content: Absolutely! It acts differently with different polarities, it´s kind of a diode!

author: exe
author_rank: Unknown
timestamp: January 09, 2023, 01:47:26 pm
content: Tantalums also have sound visual polarity indication. I once reverse biased it and it blew in my face with a bang

author: Noopy
author_rank: Super Contributor
timestamp: January 09, 2023, 05:18:43 pm
content: Quote from: exe on January 09, 2023, 01:47:26 pmYes, they give a very clear feedback!

author: SeanB
author_rank: Super Contributor
timestamp: January 12, 2023, 12:11:22 pm
content: Just do not do that with 4700uf 35V tantalum block units, they internally contain a pcb with a load of smaller tantalum capacitors on it, then are potted in soft silicone and then soldered shut. They do go bang nicely, and with a few blasts as well. Never got to do that with the monolithic 10 000uF round ones, though I suspect that would result in a lot of shrapnel, as those are pretty big, and also pretty expensive as well.

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 12:00:36 pm
content: Many beautiful pictures posted here.I will post some of the pictures I took.EFD108 is a germanium point contact diode in a DO-7 type package.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 17, 2023, 12:26:20 pm
content: That's a very good looking pic.Lens? Camera? Photo stacking?

author: mister_rf
author_rank: Contributor
timestamp: January 17, 2023, 01:20:17 pm
content: Old pic, old setup.A Canon EOS 5D (the first version) camera, MP-E65 mm lens, manual rail, stacked in Helicon Focus, edited.

author: mister_rf
author_rank: Contributor
timestamp: January 18, 2023, 09:36:42 am
content: СВЧ Д401 Point contact Germanium diode, for applications up to 10 GHz, used in old instruments as mixer and detector. Available in a ceramic case with hard leads. Manufactured in the former Soviet Union, mid 1980s.

author: magic
author_rank: Super Contributor
timestamp: January 18, 2023, 09:42:31 am
content: I see that you found an image hosting site more reliable than the ImageShacks and Imgurs of the worldBTW, do you really need to embed full res versions inline? It sorta wastes everyone's (and your host's) bandwidth while being of little use because the images are resized anyway. With a bit more effort you could embed the auto-generated 1~2Mpx previews and make them links to the originals.

author: mister_rf
author_rank: Contributor
timestamp: January 18, 2023, 04:07:56 pm
content: Ah, yes, the bandwidth. I think I've ignored this old dial-up era rule, mea culpa. You can see that I'm a still a rookie here, nevermind my subscription year.As for the commons/wiki just as a simple hosting, I think there are other advantages for everyone besides free hosting.So here we are, this time with some more work from my part.On topic:E220/82.5-0.005ː Selenium cartridge rectifier; Peak Reverse Voltageː 220 Volts, voltage RMS under capacitive load: 82.5 Volts, with nominal currentː 5 mA. Made in German Democratic Republic, 1950s.

author: mister_rf
author_rank: Contributor
timestamp: January 19, 2023, 07:59:45 am
content: D355N2000: Rectifier diode, 355 A, 2000 V; Manufactured in România, I.P.R.S. Băneasa, 1980s

author: Noopy
author_rank: Super Contributor
timestamp: March 27, 2023, 06:55:16 pm
content: The RCA CA3039 contains an array of fast diodes. The schematic above is taken from the datasheet of Intersil, where the CA3039 was still manufactured for a while. The device contains six independent diodes, with diode D6 connected to the substrate.The integrated diodes have a very low capacitance of 0,65pF (at a reverse voltage of -2V). Reverse recovery time is typically given as 1ns (at 10mA).The above table is from the 1978 data book "RCA Linear Integrated Circuits" and shows not only the forward voltage versus current, but also the deviation between any two diodes. Up to a current of about 1mA, the difference typically stays in the range of about 0,5mV. At higher currents, the value increases to 3mV. Specified is a maximum of 5mV at 1mA.The very similar characteristics of the diodes are ideal for building modulators and demodulators. In general, the specifications of the device make it well suited for high frequency applications.The potential of pin 10 is connected to the die and additionally to the housing.The dimensions of the dies are 1.1mm x 1.0mm. The circular structure in the lower left corner is used to check the alignment of the masks against each other.The bondpad of pin 1 is round (bottom right). In the upper area, two squares are provided where two additional bondpads could be applied. Most likely, the design has been used with other interconnections and the numbers 5516 identify the mask of the CA3039. Unlike the other bondpads, the bondpad in the lower left corner lacks the square below it. This is where the substrate is contacted.The structures are transistors in which base and collector are short-circuited. The relatively highly doped base-emitter junction enables the fast switching times, but also leads to a low breakdown voltage of typically 7V. The datasheet even specifies just 5V as the minimum breakdown voltage.Since the collector has a very large interface with the substrate, the parasitic capacitance with respect to the substrate is much larger (3,2pF) than the junction capacitance (0,65pF).https://www.richis-lab.de/Diode11.htm

author: Noopy
author_rank: Super Contributor
timestamp: August 10, 2023, 06:53:27 pm
content: The OA81 is a germanium diode that was produced by several manufacturers. The optical appearance of the present diode would speak for Valvo as manufacturer, but they usually printed the company name on it. The OA81 blocks up to 75V permanently and 100V for a short time (at 75°C). The different values result from the power dissipation. At 100V and 75°C the leakage current is 450µA, which results in a power dissipation of 45mW. In the thermally well insulating glass housing, 45mW can already cause a considerable temperature rise and consequently lead to destruction of the diode.At a current of 100µA, the forward voltage is typically 0.2V, but it rises rapidly with current and is already 2,45V typ at 30mA. The maximum is 3,3V.The maximum permissible peak current is 150mA. In addition, a short-term overload operation with 500mA is allowed. Continuously 50mA are allowed at room temperature, at 75°C just 17mA. However, these values are only valid as long as no recurrent blocking voltage is applied. If a reverse voltage of 100V is applied alternately with the forward current, the current must not exceed 20mA (6.6mA at 75°C). Otherwise there is also the danger that the diode is thermally overloaded.Operation at ambient temperatures above 75°C is generally not specified, since the germanium becomes uncontrollably conductive at these temperatures and thus the diode function is no longer given.The black paint can be scraped off. As usual for such diodes, the construction is fused into a glass housing.Inside the housing, the familiar structure of a point contact diode can be seen, in which a wire rests on a semiconductor crystal. The operation of such a diode and some technical backgrounds are documented with the OA741 (https://www.richis-lab.de/Diode05.htm). It is noticeable here that the tip rests relatively obliquely on the semiconductor.Besides gold, tungsten was usually used as a material for the wire. Since this is obviously not gold, tungsten was probably used in the OA81.The tungsten wire was apparently welded to the contact wire of the diode. The high temperatures have produced a number of tarnish colors.The wire is 60µm thick. The end is usually chemically sharpened. After forming, the tip is melted into the germanium crystal to some extent, which can be seen here from the partially shiny surface.The second wire of the diode forms a plate in the housing on which the germanium crystal is soldered. The germanium crystal has an edge length of 1,1mm and is 0,2mm thick. The regularly structured surface results from the etching process, which removes impurities on the surface.Apparently, only the fourth placement attempt of the wire was successful. Four contact points can clearly be seen on the surface. Judging from the previous placement of the wire, one of the two contacts in the lower right corner was ultimately successful. For the other two contacts, the wire does not appear to have fused with the semiconductor.https://www.richis-lab.de/Diode12.htm

author: exe
author_rank: Unknown
timestamp: August 10, 2023, 08:18:36 pm
content: Wow, didn't know germanium diodes were so finicky. Forward voltage of 3.3V@30mA sounds ridiculous by modern standards. It also rises rapidly with current. Doesn't look like a typical pn-junction. Can it be due to the point contact? I mean, it only conducts in small area/volume of the die, or not?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 10, 2023, 08:37:56 pm
content: Yes, point contact; the resistance is all in that tiny little spot. So it works well for small signals, but a 6AL5 for example outperforms it at... um, certain currents I think? Not actually high currents, and not very much at low currents given the low drop. 6AL5 outperforms most silicon diodes at low currents though (of course, if you wholly ignore the heater power cost).Given the trouble of heaters, and generally high plate voltages outside of diodes, it's no accident tubes went away.Tim

author: Noopy
author_rank: Super Contributor
timestamp: August 11, 2023, 11:12:08 am
content: Quote from: exe on August 10, 2023, 08:18:36 pmIt is a pn-junction but probably one wouldn´t call it typical.A point contact in the first place is kind of a Schottky diode.The high current that melts the contact area generates a pn-junction. In the molten semicondcutor material negative charge carriers are traveling deeper into the semicondcutor and positive charge carriers are accumulating at the surface.Sometimes the point contact wires were doped a little to add some p dopant.

author: Noopy
author_rank: Super Contributor
timestamp: December 14, 2023, 07:36:41 pm
content: The Д405Б (D405B) is a microwave diode in a cartridge housing. It is a point contact diode. According to the datasheet, it is designed for operation in the wavelength range around 3 cm, which corresponds to a frequency of 10 GHz. The printed logo is reminiscent of the contact wire of a point contact diode and belongs to the Russian factory for semiconductor components Tomilinsky.The D405 is available with different polarities. In the variant with the additional index П (P), the anode potential is applied to the thinner contact. In the variant without П, the anode potential is applied to the contact with the larger diameter.The larger contact is filled with a light-colored potting compound. There is often a screw there, which is also the case here. However, the screw cannot be moved after it has been exposed. The screw was probably glued in, as the housing must be as tight as possible to ensure a long service life.When I tried to cut off the lower element, the housing broke. Here you can see how far the thread of the lower part protrudes into the ceramic cylinder.The part with the thinner connection contains the contact wire of the diode.The thread runs completely through the ceramic cylinder.The geometry of the wire provides a certain elasticity, which ensures good contact and at the same time limits the contact pressure to a certain extent.The wire disappears into a black mass, which probably serves as mechanical stabilization.The contact elements are screwed into the ceramic cylinder as far as they will go. The screw in the larger contact can then be used to move the wire and the semiconductor crystal towards each other until the desired contact pressure is achieved. A light-colored material can be seen between the ceramic body and the thread of the contact, which fixes the thread and seals the inside.The wire has a diameter of approximately 50µm. At the tip, the diameter is approximately 15µm. The so-called diode bible (Halbleiterdioden - Leitfaden für Erwachsenen-Qualifizierung und Ausbildung im VEB Werk für Fernsehelektronik by Heinz Hornung) states that tungsten or molybdenum or alloys of the two materials are usually used for such high-frequency diodes. The surface was obviously coated with gold. The diode bible further describes that the tips often just have a diameter of 8µm.Ordinary tip diodes are formed. This involves a relatively high current flowing through the tip contact, which heats up the contact area locally and thus melts it. During this formation, a pn junction is formed and the contact area is mechanically stabilized. More extensive melting produces a higher dielectric strength, which is desirable for conventional diodes such as the OA741 (https://www.richis-lab.de/Diode05.htm). At the same time, however, the junction capacitance increases. If the diode is to be used at very high frequencies, this is a major disadvantage. The diode bible explains that high-frequency diodes based on gallium arsenide are still formed. High-frequency diodes based on silicon, on the other hand, are usually not formed. The simple contact already provides a sufficient rectification effect. The physical effects that occur at the contact surface are described in more detail with the OA741.The optical appearance of the wire tip also indicates that no forming took place here. No remnants of a broken connection can be seen. The surface is slightly darker directly at the tip and slightly to the side, but this could have been caused during processing or by the operating current.The silicon crystal inside the thicker contact has an edge length of 1 mm.The crystal shows an interesting surface. Different exposures can be used to bring out different characteristics. Dirt has accumulated on the surface. According to the optical appearance, it could be solder.A contact point with the wire tip is not visible. This also indicates that the diode was not formed.Apart from the "dirt", two different structures are visible on the crystal surface. There are furrows from the top right to the bottom left, as would be expected after mechanical processing. In addition, there are structures that often occur during etching processes. However, these structures are rather irregular here.https://www.richis-lab.de/Diode13.htm

author: Miyuki
author_rank: Frequent Contributor
timestamp: December 15, 2023, 09:51:02 am
content: That chip looks like covered with some hieroglyphsMaybe it is the way they put the magic smoke in

author: Noopy
author_rank: Super Contributor
timestamp: December 15, 2023, 10:16:20 am
content: Some magic incantations?

author: RoGeorge
author_rank: Super Contributor
timestamp: December 15, 2023, 10:52:10 am
content: Quote from: Miyuki on December 15, 2023, 09:51:02 amLooks like hieroglyphs from an alien spaceship.

author: iMo
author_rank: Super Contributor
timestamp: December 15, 2023, 11:04:33 am
content: The crystals were made of the rare material found in the Podkamennaya Tunguska River..

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2023, 03:12:00 pm
content: Quote from: RoGeorge on December 15, 2023, 10:52:10 amGoa'uld technology.

author: Noopy
author_rank: Super Contributor
timestamp: January 23, 2024, 05:13:12 am
content: The ГИ308Б (GI308B) is a germanium-based tunnel diode. The G stands for germanium. The following two characters show the applications for which the diode is optimised. I3 stands for switching applications. The datasheet mentions switching devices in the sub-nanosecond range. The variant specified for military applications has a 1 in the first position of the designation: 1И308Б.The datasheet already reveals that it is a MESA diode. The index refers to one of nine bins with different capacitances and peak voltages. Diodes with the index B offer a capacitance of 0,7pF to 2pF and a peak voltage of 70mV to 110mV. Whilst the AI201G still had connection terminals, the GI308B makes direct contact with the small housing. This reduces the inductance, which is helpful for high-frequency applications. The diameter of the housing is just 3,6mm and the height is specified with 1,6mm.The individual tunnel diodes are shrink-wrapped in plastic film with small pieces of paper.On the label you can see that it originally read ГИ308Г (GI308G), which has been corrected to ГИ308Б (GI308B). The symbol reminiscent of an X and the three characters on the far right cannot be assigned.The company to which the logo belongs has a long history and has been renamed several times during this time. At the time of manufacture, it was probably Moscow plant no. 311. The company still exists today and is called Optron.Coloured dots indicate the different bins. The green dot in combination with a black and a white dot stands for the GI308B.The housing is based on a ceramic cylinder. The ends of the cylinder are closed with metal plates. The wider element consists of two parts soldered together. It can be assumed that during production the diode was inserted into the housing through the wider element.The wider contact of the tunnel diode is smooth.I wasn´t able to open the solder joint, but both metal elements eventually detached from the ceramic body. This revealed that the semiconductor was connected to the contact of the housing via a thin metal grid. The wide metal grid and the connection via two sides ensures a low parasitic inductance, which is necessary to achieve short switching times and high frequencies. The datasheet specifies 0,2nH to 0,35nH.The die has an edge length of 0,36 mm. The small, not quite centred element is the actual diode. The metal grid contacts this element. It also rests on the edges, which increases the mechanical stability. The edges must therefore be insulating.The metal grid is soldered onto the diode. The diode structure is mechanically and thermally very sensitive. Accordingly, a low-melting solder had to be used here.In the picture below you can already see that the diode structure consists of a larger element that tapers towards the substrate.The so-called diode bible explains what can be seen here (Halbleiterdioden - Leitfaden für Erwachsenen-Qualifizierung und Ausbildung im VEB Werk für Fernsehelektronik by Heinz Hornung). In the manufacture of such a tunnel diode, a very small bead of a metal mixture is first applied to a germanium crystal and alloyed with it. The diode bible speaks of a tin-antimony-arsenic mixture. Tin is the carrier material, arsenic is the dopant and arsenic improves wetting. After alloying, the germanium crystal is selectively electrolytically removed. The result is a mushroom shape with a very small pn junction and a correspondingly small junction capacitance.In addition to the small active area, very high doping with an abrupt pn junction is also necessary to achieve the desired tunnelling diode effect. The very high doping and the small active area are the reason why such tunnel diodes can be damaged even at low currents. For this reason, tunnelling diodes must not be measured with a diode tester, for example. Another weak point is the mechanical stability. The diode bible describes that the construction is therefore moulded with a lacquer. This was apparently not necessary with the GI308B.While removing the grid the mushroom head also breaks off and the base of the construct becomes visible. The mushroom head had a diameter of about 60µm. The diameter of the base at the upper end is just about 10µm.https://www.richis-lab.de/Diode14.htm

author: exe
author_rank: Unknown
timestamp: January 23, 2024, 08:47:03 am
content: Quote from: Noopy on January 23, 2024, 05:13:12 am"91Г" looks like abbreviation of "1991 Год", or year of production.As of "X", I don't really know, I think it may mean "trust the correction" ("исправленному верить"), or it's a signature of the person who did the packaging, but I don't have any evidence to support that. So, pure speculation)

author: Noopy
author_rank: Super Contributor
timestamp: January 23, 2024, 07:34:26 pm
content: Thank you for your explanation exe!I got the same explanation from another supporter. He also told me that on old typwriters there was no 1 and so one often used the I instead. It seems I´m to young to know this...

author: Noopy
author_rank: Super Contributor
timestamp: May 11, 2024, 03:50:08 am
content: The SKiiP 81 AN 15 T10 module is a three-phase bridge rectifier built by Semikron. The datecode is made up of two numbers for the year and two numbers for the calendar week. The last number stands for the production batch of that week. The module was therefore produced in calendar week 7 of 2004.The package type is called MiniSKiiP. Variant 8a was used here. However, the illustration does not quite match the module in question. The SKiiP 81 AN 15 T10 only contains the bridge rectifier and the temperature sensor. The chopper path is not fitted.The two images above show the basic structure of the MiniSKiiP modules and how they can be integrated into an application. The picture on the left is from Semikron. The picture on the right is from Vincotech, a subsidiary of Mitsubishi Electric Corporation, which also uses the MiniSKiiP modules.The module is based on a ceramic carrier on which the semiconductors are located. The potentials of the circuit are routed upwards through the package using spring contacts. The thinner spring contacts of the smaller module types can be seen here. The package variant 8 has larger, barrel-shaped contacts. A circuit board is then placed on the top. Two screws generate the necessary contact pressure, which is distributed over the entire surface by a plastic element.This overview gives a feeling for the module variants that Semikron had on offer and how the designations are made up. Module variant 8 allows currents of up to 130A, while the smaller module variants do not allow more than 75A.The datasheet for the SKiiP 81 AN 15 T10 specifies a dielectric strength of 1.500V and a current carrying capacity of 100A (at 85°C) for the diodes, whereby the current is limited by the spring contacts. Up to 1.000A are permissible for short periods.On the underside of the module the ceramic substrate is coated with a copper layer. The datasheet specifies a maximum thermal resistance of 1K/W for each diode.The gel potting was probably inserted through the two holes in the upper area after assembly. The package shows some options. The three high-current contacts and the control contact of the chopper can be inserted on the right. On the left, there is the option of controlling thyristors with six control contacts.The plastic housing can be lifted off the ceramic carrier relatively easily.The high-current contacts have angled, spring-loaded metal strips on both sides. The contacts are a little longer than plastic housing so that a certain amount of contact pressure is created during assembly.The cylindrical high-current contacts are open on one side. The package has wedge-shaped elements that retract into these gaps. The small contacts consist of just one piece of wire that has been bent several times to create a certain spring effect.The ceramic plate is 1 mm thick. Where the gel potting is not evenly flat, it disturbs the view, but the functions can still be easily recognised.The diodes of the rectifier bridge are represented by individual semiconductors. The PTC, which can be used to determine the temperature of the module, is located in the top right-hand corner. The chopper is obviously constructed with two transistors. In addition to the freewheeling diode Dbr, there is also a diode Dt in parallel with the transistors.The edge length of the diodes is 7mm. Seven bondwires contact the diodes.The diodes appear to have a MESA structure, a black coating protects this area.The shiny surface of the temperature sensor suggests that it is a diode. However, measurements show that it is actually a PTC resistor.https://www.richis-lab.de/Diode15.htm

author: Noopy
author_rank: Super Contributor
timestamp: October 17, 2024, 03:16:27 am
content: The capacitance diodes documented here come from the estate of Professor Heinz Beneking. Professor Beneking was one of the first to carry out research and teaching in the field of semiconductor technology in Germany. He worked at the RWTH Aachen.The capacitance diodes, also known as reactance diodes, are wrapped in paper. You can read on the paper that they are development parts from Telefunken.An attached measurement protocol reveals that these are germanium goldwire diodes. The series resistance and the capacitance at 0V, 3V and 10V were determined for all four diodes. The abbreviation in the bottom left corner refers to the Ulm tube factory, where the diodes were measured on November 5, 1959.A bag containing four diodes is included in the measurement protocol. A piece of paper glued to the glass body shows the number of each diode. The cathode side is painted red.The package consists of two metal sleeves that are fused into a glass cylinder. The sleeves in turn contain cylinders from which short pieces of wire protrude.The glass obscures the view of the diode's construction. However, you can already see that the metal strip on the right carries a small, thin disk that is contacted by a short, surprisingly strongly bent piece of wire. The piece of wire is soldered onto the metal strip protruding in from the left.The piece of wire was lost when the package was opened. It appears to have broken off.The disk on the right is the germanium crystal. The diameter of the disk is 0,5 mm. The wire made contact with a round element that is located in a small recess. The diameter of this element is 65µm. Apparently, they used no gold wire but applied a small gold contact to the germanium crystal.In the pictures above there seemed to be a surface structure. However, it is some kind of dirt that can be wiped off with isopropanol. The crystal is smooth.https://www.richis-lab.de/Diode16.htm

author: Noopy
author_rank: Super Contributor
timestamp: October 29, 2024, 07:45:09 pm
content: The last part of the estate of Professor Heinz Beneking. The envelope shown here contains several bags of diodes. Varactor diode is an alternative name for a capacitance diode.The envelope was folded from a Telefunken technical drawing. It is dated July 26, 1961 and shows a typical high-frequency diode. The small dimensions are necessary to keep parasitic capacitances and inductances small. The component bears the designation OA1123. However, no further information can be found with this designation. The envelope contains three different packages, only one of which corresponds to the drawing. It could be that these are different package variants of the same diode. Of course, this cannot be said with absolute certainty. A measurement of the forward voltage shows that these are germanium diodes.The envelope contains a note specifying a maximum frequency well above 10GHz. Professor Beneking received the diodes on March 13, 1963.There are three bags of one package variant, each containing one diode. Three-digit numbers and the word “green” can be found on the bags. Some characteristics are also noted.With a length of 4,9mm and a diameter of 3,5mm, this package is slightly larger than the package in the drawing.On one side is the number 299, which was also noted on the corresponding bag. The color dot underneath appears yellowish, although you can see a hint of green.The glass element is quite inhomogeneous, which clouds the view of the semiconductor. However, a disk can already be seen on the right, which is contacted with a wire from the left.If you open the package, you can examine the structure more closely. The contact wire has a diameter of 30µm. It has no tip at the end.On the other side of the diode there is a base on which the semiconductor crystal is soldered.Either the semiconductor crystal is relatively small or part of it is covered by the solder.With the appropriate exposure there is an element on the surface that appears gold-colored. This diode is therefore similar to the “1959” experimental diode.The diode shown here is only present once and was therefore not opened. The package corresponds to the illustration on the technical drawing.You can see through the glass that a wire is contacting a semiconductor crystal. Compared to the first diode, the contact area on this crystal appears to be slightly higher.The third package variant has the same geometry as the second one, but only one side has a cylindrical contact.One side has already detached from the glass element. The germanium crystal with a diameter of 0,5 mm can be seen. The contact wire has remained on the crystal.The germanium crystal is clearly visible. The contact wire appears to have been attached to it with solder.https://www.richis-lab.de/Diode17.htm

author: Noopy
author_rank: Super Contributor
timestamp: February 23, 2025, 07:09:31 pm
content: The above diode was located in a so-called switchplexer, an LMSP43AA from Murata (https://www.richis-lab.de/modem02.htm#LMSP43AA). This switchplexer realizes a switching and filtering of the antenna signals in cell phones. The SMD code reveals that it is a pin diode, a BAR64. The manufacturer cannot be determined with certainty. The BAR64 is produced by Infineon, among others. With dimensions of 1,0mm x 0,6mm, it should be a SOD-923 package.pin diodes have a non-doped or only weakly doped layer between the p-doped and n-doped areas. In this layer the free charge carriers have a very long lifetime, so that the rectifier function of the diode is greatly slowed down. Thanks to this property, pin diodes can be used as switches for high-frequency signals. They are switched conductively by allowing a DC current to flow through the diode. Inductors and capacitors ensure that the control current only flows in the area of the diode and does not affect the rest of the circuit. If a reverse voltage is applied, the high-frequency signal is strongly attenuated.Infineon states that the BAR64 can be used for frequencies up to 3GHz. The low capacitance of typically only 0,22pF is important in this context. For the relatively similar SC79 package, Infineon states a parasitic inductance of only 0,6nH. With a current flow of 10mA, the resistance of the diode is 2,1Ω.The edge length of the die is just 0,26 mm. Imagine searching for this die in some tiny epoxy residues...https://www.richis-lab.de/Diode18.htm

author: mr ed
author_rank: Regular Contributor
timestamp: February 25, 2025, 03:50:01 pm
content: How about tiny mmwave diodes with 10fF junction (not my SEM image). There are 2 back to back Schottky diodes with an air bridge to reduce parasitics. About a 1um junction.

author: Noopy
author_rank: Super Contributor
timestamp: February 25, 2025, 03:55:32 pm
content: Nice!I like such "flying structures". Reminds me of the Fluke RMS converter:https://www.richis-lab.de/RMS01.htm

author: MathWizard
author_rank: Super Contributor
timestamp: February 25, 2025, 05:55:34 pm
content: Great pictures. If I saw something like the SKiiP 81 AN 15 T10 module, I'd probably never expect some diodes.Why do point contact diodes, use a little tiny point contact ? Why don't they use a much bigger contact area, either with more pins, or plates, etc?

author: Noopy
author_rank: Super Contributor
timestamp: February 25, 2025, 06:25:00 pm
content: Point contact diodes are either very old or high frequency diodes.If you have high frequency you want a small capacitance and the point contact is the right way to go.In the old days the point contact diode was an easy way to get an pn junction: Put the needle on a doped semiconductor and fuse it with high current. You get a pn junction without masking and doping (besides the doping the crystal has in the beginning).In theory it should be possible to increase the contact area but then it would be hard to put enough power into the junction without destroying the crystal. And as soon as you integrate some defects into the pn junction you have a non ideal diode.

author: mr ed
author_rank: Regular Contributor
timestamp: February 26, 2025, 11:36:28 am
content: This is the old school point contact Schottky diode. Tungsten pin manually placed on an array of etched anodes. Low capacitance but max rf power of 1 mW,. The point contact is not fused so the junction is fragile. But, it has an incridible cutoff frequency of 10THz, 0.5fF and 30 ohms.Update : I found the source info for this diode. "T. W. Crowe, R. J. Mattauch, H. P. Roser, et al “GaAs Schottky diodes forTHz mixing Applications”, Proc. IEEE, Vol. 80, Issue 11, pp. 1827-1841, Nov., 1992."