Author Topic: Transistors - die pictures  (Read 15187 times)

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Offline ocw

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Re: Transistors - die pictures
« Reply #125 on: July 17, 2020, 09:21:24 pm »
magic, you seem more comfortable in reviewing Id/Vgs curves.
The attachment shows the five curves from each of the two halves of one SD2942 almost overlapping as compared to the five curves from half of another SD2942 not coming close to the first ten.
 

Offline magic

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Re: Transistors - die pictures
« Reply #126 on: July 18, 2020, 04:55:01 am »
This is kinda offtopic, but no, really not. It doesn't matter how you show it, it's just a philosophical question:

For a FET in the pentode region, is its Vds/Ids characteristic really anything other than just the drain impedance? If it takes different gate voltages to get the desired drain current on two parts, and then their drain impedance is about the same (high enough it's hardly even seen on those plots) is that really a difference in the Vds/Ids characteristic or just Vgs mismatch? That's all I have ever said, and as you see, I really don't  have that much to say :)

Also, I realize that drain impedance is probably not what you care about as long as it's "high enough", which probably isn't even that very high, as your schematic shows a 700Ω drain load.

If anything, it looks like the mismatched parts have different transconductance too, which might be relevant besides the different Id at given Vgs.
« Last Edit: July 18, 2020, 04:59:15 am by magic »
 

Online T3sl4co1l

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Re: Transistors - die pictures
« Reply #127 on: July 18, 2020, 10:34:27 am »
In the pentode region, the MOS equivalent of Early effect, is channel length modulation.  Drain conductance (y_oe) is usually very small indeed.

Tim
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Offline Noopy

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Re: Transistors - die pictures
« Reply #128 on: July 23, 2020, 10:30:42 am »
Today I have a MJL21193 for you (250V/16A/30A):



The package has notches to increase the creepage distance.




The die is quite big: 3,64mm x 3,54mm




It´s a perforated Emitter MESA-Transistor just like the new BUX22 (https://www.richis-lab.de/Bipolar08.htm)






 :popcorn:
 
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Offline exe

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Re: Transistors - die pictures
« Reply #129 on: July 23, 2020, 11:35:24 am »
I wonder what is the biggest bjt (in terms of die area) ever produced?
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #130 on: July 23, 2020, 11:47:39 am »
I have a halfbridge brick sitting here (KD324510). The dies in there are much bigger. Could be something around factor three. I will take some pictures!  ;D

Offline capt bullshot

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Re: Transistors - die pictures
« Reply #131 on: July 23, 2020, 01:09:35 pm »
It's not a BJT anyway, I've seen IGBT dice of 11mm * 16mm and larger. You'd find them in modules like this one:



Also have a few BJT modules, but their potting is pitch black, so one can't see the dice.
Safety devices hinder evolution
 
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Offline duak

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Re: Transistors - die pictures
« Reply #132 on: July 23, 2020, 07:31:36 pm »
I have some old BJT six-pack modules for a servo drive.  While looking for information on them I ran across the attached paper on the development of similar devices.  Page 2 shows the pre-potted assembly but without device ID or dimensions.  Assuming the overall dimensions are at least 30 mm x 50 mm the largest dice are maybe 10 mm x 10 mm.  If memory serves, these modules are attached with M4 or M5 screws so these dice could be even larger than that.

This fellow built a 3 phase linear amplifier using similar devices: http://wunderkis.de/pwramp3/index.html

I toyed with the idea of making an electronic load with one of modules I have.  I've used one as a battery simulator to test a 50 A battery charger because it was easier than wiring a bunch of power MOSFETs or BJTs in parallel - I just needed a few zener diodes, resistors and wires with ring terminals.  The module was prone to high frequency oscillation when in the linear region at some currents so it seems that the basic devices are reasonably fast.  I think I read somewhere that these are triple diffused epitaxial to minimize switching losses.

These devices remind me of old IC engines with 5 litre cylinders and a 1000 RPM redline.  If memory serves, these run at about 2 kHz.

 

Offline capt bullshot

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Re: Transistors - die pictures
« Reply #133 on: July 23, 2020, 08:08:50 pm »
This fellow built a 3 phase linear amplifier using similar devices: http://wunderkis.de/pwramp3/index.html
That's me, by the way.


Quote
I toyed with the idea of making an electronic load with one of modules I have. 
I'd recommend against that:
- they "like" to oscillate
- their DC SOA isn't that great, they can die at way lower power levels than their maximum ratings if used in DC linear mode (I had this once or twice in my amplifier trying to use is as a DC current source). With AC output, even at as low frequencies as 50Hz, the SOA gets better.

Safety devices hinder evolution
 

Offline duak

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Re: Transistors - die pictures
« Reply #134 on: July 23, 2020, 10:11:43 pm »
Ah, the capt himself.  Nice job on the driver and the write up is very clear - thank you!

Yes, the DC SOAs on the modules I have are not so good - a Pdmax of 200 W for a devices with a BVCEO of 500 V and an ICMAX of 100 A, clearly optimized for switching.  Their instability was a bit of a surprise as the servo drive they are from had 10 to 30 cm long wires and bus bars all over the place carrying drive signals and switched currents.  However, because it was a PWM, the devices weren't in the linear regime long enough to encounter trouble from oscillation.  After encountering the oscillation and reading the write up, it's back to the old plan.  Too bad, because the module would be simple to mount on a heat sink and wire up.
« Last Edit: July 29, 2020, 05:05:14 pm by duak »
 

Offline Wolfgang

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Re: Transistors - die pictures
« Reply #135 on: July 23, 2020, 10:24:48 pm »
Ah, the capt himself.  Nice job on the driver and the write up is very clear - thank you!

Yes, the DC SOAs on the modules I have are not so good - a Pdmax of 200 W for a devices with a BVCEO of 500 V and an ICMAX of 100 A, clearly optimized for switching.  Their instability was a bit of a surprise as the servo drive they are from had 10 to 30 cm long wires and bus bars all over the place carrying drive signals and switched currents.  However, because it was a PWM, the devices weren't in the linear regime long enough to encounter trouble from oscillation.  After encountering the oscillation and reading the write up, it's back to the old plan.  Too bad, because the module be simple to mount on a heat sink and wire up.

Try linear mosfets (IXYS). They are made for electronic loads.
 

Offline David Hess

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Re: Transistors - die pictures
« Reply #136 on: July 24, 2020, 04:06:10 am »
Try linear mosfets (IXYS). They are made for electronic loads.

The problem is that unless you need maximum power in fewer packages, bipolar transistors just cost less for a given die area and power dissipation is proportional to die area.  So linear MOSFETs come with a double price premium which might even make lateral MOSFETs price competitive.
 

Online T3sl4co1l

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Re: Transistors - die pictures
« Reply #137 on: July 24, 2020, 04:53:32 pm »
Try linear mosfets (IXYS). They are made for electronic loads.

The problem is that unless you need maximum power in fewer packages, bipolar transistors just cost less for a given die area and power dissipation is proportional to die area.  So linear MOSFETs come with a double price premium which might even make lateral MOSFETs price competitive.

If you can find them...

But all of the above seem to be superseded by SuperJunction types, which regularly give DC SOA curves.  I've tested a few and found them to be accurate.  I'm not sure how they do it -- SJ have higher power density than ever, but they still manage not to runaway.

Tim
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Bringing a project to life?  Send me a message!
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #138 on: July 28, 2020, 05:58:47 pm »

Today I have a 2N2857 HF-Transistor for you.
It´s a quite interesting transistor manufactured by Central Semiconductor.




Central Semiconductor builds obsolete transistors. Originally the 2N2857 was built by Motorola.
This 2N2857 has a datecode 1738!  :-+




It has four pins. The housing is isolated.




To isolate the transistor it was package on the collector pin.  :-+ ;D
Thermal resistance is probably a bit higher...






The die is ~350µm*350µm.
There is a second transistor on the die probably to test the die. Interesting... Why didn´t they do the testing with the 2N2857 transistor itself?  :-//


And it glows:



1mA



5mA

 8)

Breakdown voltage is quite low (around -6V) because of high doping for high switching frequency.


More pictures here::

https://www.richis-lab.de/Bipolar16.htm

 :popcorn:
 
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Offline exe

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Re: Transistors - die pictures
« Reply #139 on: July 28, 2020, 06:13:42 pm »
Please excuse my ignorance, where is the second bjt located? Is it two big pads on the left on the close up shot?
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #140 on: July 28, 2020, 06:17:14 pm »
Please excuse my ignorance, where is the second bjt located? Is it two big pads on the left on the close up shot?

Yes it is. The two bigger pads are base and emitter and the smaller at the bottom corner is the collector.
Looking very carefully you can spot the corners of the emitter area around the emitter pad.

Online RoGeorge

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Re: Transistors - die pictures
« Reply #141 on: July 28, 2020, 06:26:44 pm »
I wouldn't expect it to be that smol!   ;D

Offline David Hess

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Re: Transistors - die pictures
« Reply #142 on: July 28, 2020, 06:56:28 pm »
There is a second transistor on the die probably to test the die. Interesting... Why didn´t they do the testing with the 2N2857 transistor itself?  :-//

Could the tests be destructive like base-emitter breakdown voltage?
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #143 on: July 28, 2020, 07:08:17 pm »
There is a second transistor on the die probably to test the die. Interesting... Why didn´t they do the testing with the 2N2857 transistor itself?  :-//

Could the tests be destructive like base-emitter breakdown voltage?

Never heard of such testing but that would explain the second transistor...

Offline exe

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Re: Transistors - die pictures
« Reply #144 on: July 28, 2020, 07:16:00 pm »
How do they pick and place such small dies? Or even cut them...

Those metal can packages... I have an urge to buy just for the sake of owning it.

PS I have Russian МП-42 (MP-42) somewhere, an old germanium transistor. I wanted to put it into use, but may be I should crack it open and see what's inside :). Can't find it atm, must be hiding from me....
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #145 on: July 28, 2020, 07:21:00 pm »
How do they pick and place such small dies? Or even cut them...

Those metal can packages... I have an urge to buy just for the sake of owning it.

PS I have Russian МП-42 (MP-42) somewhere, an old germanium transistor. I wanted to put it into use, but may be I should crack it open and see what's inside :). Can't find it atm, must be hiding from me....

And look at these small bond wires you have to place them accurate on the bondpad.
The handling must be pretty tricky.
Fascinating engineering!

The MP-42 is afraid...  ;D

Offline David Hess

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Re: Transistors - die pictures
« Reply #146 on: July 29, 2020, 02:50:03 am »
There is a second transistor on the die probably to test the die. Interesting... Why didn´t they do the testing with the 2N2857 transistor itself?  :-//

Could the tests be destructive like base-emitter breakdown voltage?

Never heard of such testing but that would explain the second transistor...

It occurred to me because RF transistors often have a rated base-emitter breakdown voltage of only 3 volts instead of the more common 5 volts.
 

Offline Zoli

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Re: Transistors - die pictures
« Reply #147 on: July 29, 2020, 04:28:48 am »
How do they pick and place such small dies? Or even cut them...

Those metal can packages... I have an urge to buy just for the sake of owning it.

PS I have Russian МП-42 (MP-42) somewhere, an old germanium transistor. I wanted to put it into use, but may be I should crack it open and see what's inside :). Can't find it atm, must be hiding from me....
Back in my times(30+years ago) I've opened quite a few from the MP38-42/P401-3 series; first, they are all Ge transistors; second, all of the structures are visible with the naked eye(die connection:1.00X0.01 mm Al or similar flat); third , don't blame my memory if there's something totally diferent inside; I just try to remember best of my impressions.
 

Offline Noopy

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Re: Transistors - die pictures
« Reply #148 on: July 29, 2020, 06:02:07 am »
Back in my times(30+years ago) I've opened quite a few from the MP38-42/P401-3 series; first, they are all Ge transistors; second, all of the structures are visible with the naked eye(die connection:1.00X0.01 mm Al or similar flat); third , don't blame my memory if there's something totally diferent inside; I just try to remember best of my impressions.

Like this one?
https://www.richis-lab.de/Bipolar06.htm
That's more mechanical engineering than electrical engineering.  ;D


Regarding the test-transistor:
Perhaps it was easier to test a transistor with all three terminals on the surface instead of the other transistor with it's collector on the back of the die...


Offline magic

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Re: Transistors - die pictures
« Reply #149 on: July 29, 2020, 06:40:38 am »
These two transistors have the same collector ;)
 


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