Author Topic: Diodes - die pictures  (Read 644 times)

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Offline Noopy

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Diodes - die pictures
« on: June 04, 2021, 11:40:09 am »
In this topic I will post pictures of diodes. You can find the overview here: https://www.richis-lab.de/Diode.htm

I 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.  :clap: ;D
1000V / 1A




The die is protected with some white potting.




The die is 0,2mm thick.




0,93mm x 0,95mm
Both 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...  :-/O


https://www.richis-lab.de/Diode02.htm

 :-/O
 
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Offline RoGeorge

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Re: Diodes - die pictures
« Reply #1 on: June 04, 2021, 02:56:52 pm »
Thank you, subscribed!   :)
 
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Offline T3sl4co1l

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Re: Diodes - die pictures
« Reply #2 on: June 04, 2021, 09:13:46 pm »
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.

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Offline Noopy

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Re: Diodes - die pictures
« Reply #3 on: June 05, 2021, 12:24:46 am »
Drop it in acid, see if there's any patterning on top?

Good idea!  :-+ Unfortunately I have lost the die. ::) Will have to decap one more 1N4007.


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.

I´m pretty sure the 1N4007 has nothing like that.
I have taken pictures of two IGBTs and their freewheeling diodes:








International Rectifier IRG4PH40K
https://www.richis-lab.de/Bipolar35.htm






IXYS IXGH48N60C3D1
https://www.richis-lab.de/Bipolar26.htm


And of course the darlington power modules:






Powerex KD324510
https://www.richis-lab.de/Bipolar19.htm




Gleichrichterwerk Stahnsdorf SU510
https://www.richis-lab.de/Bipolar24.htm


But I will have to get a power schottky...  :-/O ;D

Offline David Hess

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Re: Diodes - die pictures
« Reply #4 on: June 05, 2021, 02:32:12 am »
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.
 
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Offline Noopy

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Re: Diodes - die pictures
« Reply #5 on: June 05, 2021, 06:12:54 am »
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.

That 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.

Offline Noopy

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Re: Diodes - die pictures
« Reply #6 on: July 22, 2021, 07:33:55 pm »



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.  |O




3,8mm x 3,4mm




The 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...  :-/O




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

 :-/O
 
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Offline Noopy

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Re: Diodes - die pictures
« Reply #7 on: Today at 04:10:38 am »




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

 :-/O
 
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Offline Miyuki

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Re: Diodes - die pictures
« Reply #8 on: Today at 07:34:39 am »
exe wanted to see a FERD (Field Effect Rectifier Diode). Finally I have taken some pictures of a ST Microelectronics FD40H100.
Interesting 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?
 

Offline Noopy

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Re: Diodes - die pictures
« Reply #9 on: Today at 08:14:52 am »
exe wanted to see a FERD (Field Effect Rectifier Diode). Finally I have taken some pictures of a ST Microelectronics FD40H100.
Interesting 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?

It is a pleasure! I have some more interesting diodes here... ...more interesting than the 1N4007.  :-/O

Yeah, it seems the switching characteristic of the FERD is nothing you want to promote.  ;D



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