Author Topic: Decapping and Chip-Documentation - Howto  (Read 4935 times)

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Online magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #25 on: January 17, 2020, 06:14:42 pm »
No. These are pretty much bare dies with solder blobs on them that you just put on your board upside down and reflow. Sometimes with interesting side effects.

https://www.raspberrypi.org/blog/xenon-death-flash-a-free-physics-lesson/

COBs are potted to protect their bonding wires from being torn. And maybe to stop light as well ;)
« Last Edit: January 17, 2020, 06:19:19 pm by magic »
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #26 on: January 17, 2020, 07:31:06 pm »
But it's been designed to be used like that, as the die of a CCD or a COG that can also be seen, which is not, I think, the same thing as if by removing the epoxy package it's been designed to be in and protected by, you had left it naked and exposed. Humidity and IIRC sodium are chip killers, and both can be in the air.
« Last Edit: January 17, 2020, 08:16:12 pm by GeorgeOfTheJungle »
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Offline imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #27 on: January 17, 2020, 08:08:12 pm »
All chips are covered by few hundreds nm of glass passivation. The only openings are at the pads for the bond wires.
I wanted to see the die of the LT1021 Vref - I put the DIL8 epoxy into the direct flame of my kitchen stovetop, kept there for a couple of minutes (the package was yellow hot) and then I threw it into cold water. The epoxy package desintegrated while squeezed with fingers. No acids required.
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #28 on: January 17, 2020, 08:13:28 pm »
All chips are covered by few hundreds nm of glass passivation. The only openings are at the pads for the bond wires.
I wanted to see the die of the LT1021 Vref - I put the DIL8 epoxy into the direct flame of my kitchen stovetop, kept there for a couple of minutes (the package was yellow hot) and then I threw it into cold water. The epoxy package desintegrated while squeezed with fingers. No acids required.

Do me a favor: plug it in and let me know for how long it works ;D
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Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #29 on: January 17, 2020, 08:41:58 pm »
Wow, this is a beautiful photo!


https://www.richis-lab.de/Howto_Licht.htm
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #30 on: January 17, 2020, 08:46:43 pm »
Thanks!  :-+

One of my favourites:



Soon I´ll have a MEMS-Sensor... Really cool pictures…  8) ;D 8)

New pictures will be bigger. 700px are outdated.
One day I´ll update the old ones…  :-/O
 
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Offline imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #31 on: January 17, 2020, 08:48:53 pm »
The chip itself is produced at pretty high temperatures. The wafers are yellow/white hot during various diffusion processes (around 1000 degC). Thus to put a chip die into a kitchen stovetop flame is for the die the same fun as when you sit yourself into a steam sauna. The aluminum or copper metalisation layers will not desintegrate as they are hold together by the glass passivation layer. Of course, nobody would guarantee you the chip may work after such an exercise.
« Last Edit: January 17, 2020, 08:51:56 pm by imo »
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #32 on: January 17, 2020, 08:51:17 pm »
The chip itself is produced at pretty high temperatures. The wafers are yellow hot during various diffusion processes (around 1000 degC). Thus to put a chip die into a kitchen stovetop flame is for the die the same fun as when you sit yourself into a steam sauna. The aluminum or copper metalisation layers will not desintegrate as they are hold together by the glass passivation layer. Of course, nobody would guarantee you the chip may work after such an exercise.

You are right but a torch can ruin the metal layer:

 
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Offline imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #33 on: January 17, 2020, 09:03:15 pm »
It could be the metallization layers get ruined by the gases streaming off the epoxy package penetrating the glass passivation layer, when put into torch (the epoxy package contains up to 8% of water and 17% of epoxy resin).
Nice pictures!
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #34 on: January 17, 2020, 09:03:40 pm »
The chip itself is produced at pretty high temperatures. The wafers are yellow/white hot during various diffusion processes (around 1000 degC). Thus to put a chip die into a kitchen stovetop flame is for the die the same fun as when you sit yourself into a steam sauna. The aluminum or copper metalisation layers will not desintegrate as they are hold together by the glass passivation layer. Of course, nobody would guarantee you the chip may work after such an exercise.

I think the idea is not to go further than 600˚C or so maximum (aluminium melts at 660). 400˚C in noopy's oven seems to work fine: https://www.richis-lab.de/decap-ofen.htm

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Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #35 on: January 17, 2020, 09:06:54 pm »
Thanks!  :-+

One of my favourites:



Yep, that's even better!  :-+

What's a MEMS-Sensor, a solid state microphone?
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #36 on: January 17, 2020, 09:10:47 pm »
It could be the metallization layers get ruined by the gases streaming off the epoxy package penetrating the glass passivation layer, when put into torch (the epoxy package contains up to 8% of water and 17% of epoxy resin).
Nice pictures!

Sounds possible...

Thanks!  :-+


I think the idea is not to go further than 600˚C or so maximum (aluminium melts at 660). 400˚C in noopy's oven seems to work fine: https://www.richis-lab.de/decap-ofen.htm

That´s the idea. Don´t risk more than neccesary.  :)


What's a MEMS-Sensor, a solid state microphone?

"Small, Low Power, 2-Axis ±3 g i MEMS® Accelerometer"
https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL323.pdf
And it looks really nice!  8)

Offline imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #37 on: January 17, 2020, 09:12:29 pm »
I think the idea is not to go further than 600˚C or so maximum (aluminium melts at 660). 400˚C in noopy's oven seems to work fine: https://www.richis-lab.de/decap-ofen.htm
Yea, I got the package in the same shape as on the last picture in the link :)
The biggest issue was to find the chip in the dirty mess :)
Sure, the gas oven or torch is not easy to regulate.
« Last Edit: January 17, 2020, 09:14:24 pm by imo »
 
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Online magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #38 on: January 17, 2020, 09:39:13 pm »
But it's been designed to be used like that, as the die of a CCD or a COG that can also be seen, which is not, I think, the same thing as if by removing the epoxy package it's been designed to be in and protected by, you had left it naked and exposed. Humidity and IIRC sodium are chip killers, and both can be in the air.
Epoxy package doesn't protect from humidity. Quite the contrary, it soaks up like a sponge. Sensitivity to humidity is a well known problem with plastic-encapsulated voltage references, for example.

I'm pretty sure that oxygen diffuses right through it as well for that matter, and sodium hydroxide (the thing that sodium ultimately turns into in contact with humidity) probably too. Though I'm not sure if Na/Na₂O/NaOH seriously exists in the air in any serious quantities? :-//

NaOH is a chip killer. It can dissolve every part except epoxy and copper. You could actually drop a chip in NaOH solution for a few years and see if epoxy will protect it ;)

It could be the metallization layers get ruined by the gases streaming off the epoxy package penetrating the glass passivation layer, when put into torch (the epoxy package contains up to 8% of water and 17% of epoxy resin).
Nice pictures!
I have a simpler theory: the melting point of aluminium is only 660°C ;)
I suppose it just melts, gathers in blobs and then solidifies again, displaced.

At any rate, as I said, 10 minutes at 450°C and the opamp I tested was totally dead and unreactive to anything.
 

Offline imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #39 on: January 17, 2020, 09:45:26 pm »
Though I'm not sure if Na/Na₂O/NaOH seriously exists in the air in any serious quantities? :-//
I was reading (or it was youtube?) some interesting stuff on history of chip making in Japan. They were coping with Na in air as they were located near the sea shore.
« Last Edit: January 17, 2020, 10:01:50 pm by imo »
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #40 on: January 17, 2020, 09:56:24 pm »
Yep, it's salt, chlorine and sodium ions, both things are bad for the chips, near the sea there's lots of that in the moist air.
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Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #41 on: January 17, 2020, 09:58:46 pm »
Epoxy package doesn't protect from humidity. Quite the contrary, it soaks up like a sponge.

"Like a sponge"? Hyperbole for the win :)
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Offline blueskull

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Re: Decapping and Chip-Documentation - Howto
« Reply #42 on: January 18, 2020, 03:01:35 am »
But are then put in a package of some sort before use, right? Even the cheapest COBs are.

Underfill is recommended, not mandatory.
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #43 on: January 19, 2020, 11:59:11 pm »
What's a MEMS-Sensor, a solid state microphone?

"Small, Low Power, 2-Axis ±3 g i MEMS® Accelerometer"
https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL323.pdf
And it looks really nice!  8)

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Offline TheUnnamedNewbie

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Re: Decapping and Chip-Documentation - Howto
« Reply #44 on: January 20, 2020, 03:28:01 pm »
The chip itself is produced at pretty high temperatures. The wafers are yellow/white hot during various diffusion processes (around 1000 degC). Thus to put a chip die into a kitchen stovetop flame is for the die the same fun as when you sit yourself into a steam sauna. The aluminum or copper metalisation layers will not desintegrate as they are hold together by the glass passivation layer. Of course, nobody would guarantee you the chip may work after such an exercise.

All those high temperatures are done in the FEOL. Once you do metalization in the BEOL I don't think you see those temperatures anymore.

I believe that more modern technologies don't use glass passivation anymore but some polymers? I know colleagues at the lab complain about it a lot since it is a lot less robust and easy to accidentally probe through.
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Re: Decapping and Chip-Documentation - Howto
« Reply #45 on: January 20, 2020, 04:50:51 pm »
Why would they do that? Isn't SiO₂ still the basic insulator used all over the die anyway? Something to do with high-k CMOS?
 

Offline blueskull

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Re: Decapping and Chip-Documentation - Howto
« Reply #46 on: January 20, 2020, 04:53:41 pm »
Why would they do that? Isn't SiO₂ still the basic insulator used all over the die anyway? Something to do with high-k CMOS?

Something with CTE mismatch. Having a low modulus layer like polyimide helps mitigate the stress. Even some power devices do this. Cree SiC MOSFETs all have this.
 
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #47 on: January 20, 2020, 07:11:31 pm »


Thanks for the link, looks very interesting!  :popcorn:


Why would they do that? Isn't SiO₂ still the basic insulator used all over the die anyway? Something to do with high-k CMOS?

Something with CTE mismatch. Having a low modulus layer like polyimide helps mitigate the stress. Even some power devices do this. Cree SiC MOSFETs all have this.

I know only one use of polyimide: It is used considerable time for memory as a additional layer. The reason is that in the mold compound there are always some radioactive particels which can change the logic level of small memory cells.
Interesting that it´s also used for SiC MOSFETs.

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #48 on: January 20, 2020, 07:35:48 pm »
Epoxy package doesn't protect from humidity. Quite the contrary, it soaks up like a sponge.
"Like a sponge"? Hyperbole for the win :)

"Microchip Fabrication, 3rd edition, p559"

Quote
Hermetic sealing results in a package that is impervious to the penetration of moisture and other gases. Hermetic seals are required for chips operating in harsh and demanding environments such as rockets or space satellites [..]
Nonhermetically sealed packages are adequate for most consumer applications [..] This sealing system provides good and adequate environmental protection of the chip, except in the most demanding situations. A better term for this type of enclosure sealing method would be "less hermetic". These packages are composed of epoxy resins or polymide materials and are generally referred to as "plastic packages".
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Online magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #49 on: January 20, 2020, 08:53:55 pm »
https://www.analog.com/en/analog-dialogue/articles/does-my-voltage-reference-design-hold-water.html
Quote
Does My Voltage Reference Design Hold Water? Methods of Managing Humidity and Performance in Precision Analog Systems
:-DD

Seriously though, the question was if the plastic is critical for protecting the IC from "ambient" chemicals. To my limited knowledge, it's not.
Go ask blueskull how long his decapped transistors survived outside the package. I think his bewilderment suggests that it wasn't really a problem :P

 
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