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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Noopy on September 03, 2019, 10:09:03 pm

Title: Decapping and Chip-Documentation - Howto
Post by: Noopy on September 03, 2019, 10:09:03 pm

Hi all,


today I can show you a Howto regarding an easy way of decapping and documentating Chips:

https://www.richis-lab.de/Howto.htm (https://www.richis-lab.de/Howto.htm)


(https://www.richis-lab.de/images/howto/O_03.jpg)


I´ve structured the topic in different articles:

1. Decapping
https://www.richis-lab.de/Howto_Decap.htm (https://www.richis-lab.de/Howto_Decap.htm)

2. Optics
https://www.richis-lab.de/Howto_Optik.htm (https://www.richis-lab.de/Howto_Optik.htm)

3. Positioning and ligths
https://www.richis-lab.de/Howto_Licht.htm (https://www.richis-lab.de/Howto_Licht.htm)

4. Picture tuning
https://www.richis-lab.de/Howto_Tuning.htm (https://www.richis-lab.de/Howto_Tuning.htm)


As usual text on my homepage is german but I will answer every question you have regarding the topic.


Have fun!  :popcorn:



Best regards,


Richard

Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on September 04, 2019, 08:21:18 am
1. Decapping
https://www.richis-lab.de/Howto_Decap.htm (https://www.richis-lab.de/Howto_Decap.htm)
It seems that you got fire to work. I had problems with it and ruined many dies by overheating so I switched to a Chinese 936 iron :)
[attachimg=1]
Normal soldering temperatures aren't sufficient, I drive the heater manually from 24V DC. Temperature is monitored by connecting the thermocouple sense pins to a TM-902C type thermometer.
About 600~650°C at the heater is sufficient. Aluminum melts at 660°C and the die is cooler than the heater so it should be safe; I have opened a dozen chips that way and never overheated a single one.
Plenty of magic smoke is emitted but there are no flames. Do it outside or under ventilation.

Alternatively, 65% nitric acid at boiling temperature (130°C or so IIRC) does a great job in a few minutes with zero risk to the die except for eating aluminum bonding pads. Disadvantages are fumes (do it outside) and lack of general availability in this EU shithole (find somebody who has access to it professionally).

I'm planning to try 95% or 98% sulfuric next time because I've seen reports that it doesn't attack aluminum. OTOH, sulfuric is said to require higher temperature, something like 200°C or more.

It is beneficial to "preprocess" the chip by cutting excess epoxy with tin snips, particularly for chemical methods.

2. Optics
https://www.richis-lab.de/Howto_Optik.htm (https://www.richis-lab.de/Howto_Optik.htm)

3. Positioning and ligths
https://www.richis-lab.de/Howto_Licht.htm (https://www.richis-lab.de/Howto_Licht.htm)
I haven't done any imaging yet myself.

I found this interesting blog, they show some decent pictures and talk a bit about their methodology. They used microscope lenses, though.
https://resnicklab.wordpress.com/2012/09/26/microscopes-and-imaging/ (https://resnicklab.wordpress.com/2012/09/26/microscopes-and-imaging/)

The general conclusion appears to be that best results are obtained with long focal length and long distance. Of course diffraction and aberrations still set a limit on practical magnification.
They also say that silicon is partly transparent and that this is the reason why you get nice colorful images with back illumination. I'm not sure if it's true.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on September 05, 2019, 03:43:21 am
I didn´t have much problems with die damage due to the heating. Sometimes there was some kind of blistering but not bad.
I try to heat the package very quickly with a hot blue flame and only as long as necessary.
With my proceeding real damage comes only when you use the hot flame directly on last package parts on the die.

Interesting you use only "electric heat" to open the packages. Perhaps some time I´ll try that too.

Surely acids are the best way to get nice clean dies but I didn´t want to work with such dangerous chemicals.


Regarding the imaging I was proud having found a cheap method of taking photos with good magnification factors (as long as you already have a DSLR).
Surely there are special microscopes with special optics but you have to spend a lot of money for such a tool.

On the page you linked I couldn´t find a clue which resolution they really acchieve and how the final setup looks like.  :-//
I think I have to study the page in more detail...  :popcorn:
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 09, 2020, 10:48:06 pm
Hi all!


News on my page (yes, german...  ::)):
https://richis-lab.de/decap-ofen.htm (https://richis-lab.de/decap-ofen.htm)


I have built an ofen for the decapping:

(https://richis-lab.de/images/decap-ofen/11.jpg)


Works quite fine and reproducible!  :-+


(https://richis-lab.de/images/decap-ofen/15.jpg)

Something around 400°C for 2-5 minutes and you are inside the package.  :-+


 :popcorn:

Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 09, 2020, 11:10:39 pm
That's seriously cool and much better than anything I have ever done :-+

BTW, I actually like that smell ;D
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 09, 2020, 11:14:29 pm
That's seriously cool and much better than anything I have ever done :-+

BTW, I actually like that smell ;D

Thanks!  8)

Well, the smell reminds somehow of the youth but with time (and chips) it becomes too much...  >:D
Thank god I have a porch!  8)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 12:37:30 pm
:clap:  :-+ => :popcorn:
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 01:11:23 pm
Been there, done that. But I did the acid solution method and IT WAS NASTY!
I decapped a few packaged MOSFETs and extracted the dies to use in a project (good luck buying bare dies in small quantity). It's challenging to decap those, harder to keep them intact.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 17, 2020, 01:32:55 pm
98% sulfuric, oleum or fuming nitric? ;)

I tried  less concentrated acid once and bonding pads went away with the package ;D
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 01:56:56 pm
That's seriously cool and much better than anything I have ever done :-+

BTW, I actually like that smell ;D

Thanks!  8)

Well, the smell reminds somehow of the youth but with time (and chips) it becomes too much...  >:D
Thank god I have a porch!  8)

İt's the smell of magic smoke, isn't it?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 02:20:10 pm
98% sulfuric, oleum or fuming nitric? ;)

I tried  less concentrated acid once and bonding pads went away with the package ;D

I used saturated sodium nitrate dissolved in 98% hot (~100C) sulfuric acid. Don't use near boiling (337C) acid. It's gonna end up very bad if something happens.
Boiling H2SO4 burns basically anything organic instantly, while 100C ones give you a sec or two to wipe things off.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 17, 2020, 02:32:03 pm
That's seriously cool and much better than anything I have ever done :-+

BTW, I actually like that smell ;D

Thanks!  8)

Well, the smell reminds somehow of the youth but with time (and chips) it becomes too much...  >:D
Thank god I have a porch!  8)

İt's the smell of magic smoke, isn't it?

Quite right!
Thought about filling the smoke in tubes to refill the next failed IC.  ;D
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 17, 2020, 03:25:17 pm
I used saturated sodium nitrate dissolved in 98% hot (~100C) sulfuric acid. Don't use near boiling (337C) acid. It's gonna end up very bad if something happens.
Boiling H2SO4 burns basically anything organic instantly, while 100C ones give you a sec or two to wipe things off.
Did you try without the nitrate? I have heard of somebody using pure sulfuric acid to decap commercial parts for use in hybrid circuit prototypes, but I don't know if 98% is pure enough. And I think his temperature was higher.

There is certainly no point heating beyond 100~150°C if you add nitrate because all the nitric acid created in the reaction will evaporate or decompose. And yes, that's basically the nitrating mixture, except much hotter than usual, so it will burn/explode everything :)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 03:37:33 pm
Did you try without the nitrate?

Yes, but my hot plate doesn't go nearly to the temp needed for it to work, and I'm not nearly willing to risk losing a piece of skin.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 03:38:19 pm
Silicon melts at 1414 ° C, gold at 1064, aluminium at 660, (what else can melt inside the chip?) if you can get the magic smoke at temps below that, why use nasty chemicals?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 03:48:15 pm
Silicon melts at 1414 ° C, gold at 1064, aluminium at 660, (what else can melt inside the chip?) if you can get the magic smoke at temps below that, why use nasty chemicals?

CTE mismatch can cause failures within the die, also plastic can pop if being heated too quickly, plus dopant diffusion can happen if you heat silicon too much.
Also, chips may have organic kapton passivation, which can be damaged by heat. Acid can attack epoxy much faster than kapton, but heat attacks kapton faster than epoxy.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 03:55:30 pm
But, do you expect the chip to work after decapping? What for? I mean, once decapped, the chip exposed to the air won't work for much longer, right?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 04:03:45 pm
I mean, once decapped, the chip exposed to the air won't work for much longer, right?

Who told you that?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 04:22:56 pm
I've read it in the book "Microchip Fabrication" (Peter Van Zant)  :-//
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 04:27:28 pm
I've read it in the book "Microchip Fabrication" (Peter Van Zant)  :-//

I've read the same in old soviet books. It doesn't hold anymore today.

Many modern chips are sold in solderable die form, called wlcsp or dsbga.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 17, 2020, 04:36:01 pm
I did an experiment once and heated a DIP8 opamp on the tip of soldering iron set to 450°C for ten minutes. It didn't work afterwards and the epoxy got a bit smelly but still too hard to break. So it seems you can't get working parts that way.

Plastics are permeable to air and moisture. If it's sold in plastic package it has to be chemically resistant. Chips are "passivated" with a layer of glass on top.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: MagicSmoker on January 17, 2020, 04:57:42 pm
I used saturated sodium nitrate dissolved in 98% hot (~100C) sulfuric acid. Don't use near boiling (337C) acid. It's gonna end up very bad if something happens.
Boiling H2SO4 burns basically anything organic instantly, while 100C ones give you a sec or two to wipe things off.

Sounds like heaps of fun... and if I remember my inorganic chemistry correctly, this makes anhydrous nitric acid in situ, which is such a strong oxidizer it rapidly passivates most metals rather than dissolve them (I don't think aluminum bond wires will survive, however).

Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 17, 2020, 05:05:01 pm
Good enough that bare aluminum bonding pads survive :)

Pure nitric is the standard chemical in failure analysis labs. But it's expensive and rarely available to individuals.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull on January 17, 2020, 05:08:04 pm
Pure nitric is the standard chemical in failure analysis labs. But it's expensive and rarely available to individuals.

Adding to that, commonly available 68% is not good enough (will still work, but will damage aluminum bonding pads). You need at least RFNA or even WFNA to decap safely, but due to their potential of making explosives and narcotics, they are banned in many countries to individuals.

H2SO4 can be had in forms of drain cleaner or toilet tile cleaner, and the additives won't change its property decapping chips.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 05:35:27 pm
I've read it in the book "Microchip Fabrication" (Peter Van Zant)  :-//

I've read the same in old soviet books. It doesn't hold anymore today.

Many modern chips are sold in solderable die form, called wlcsp or dsbga.

But are then put in a package of some sort before use, right? Even the cheapest COBs are.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic 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/ (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 ;)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 08:41:58 pm
Wow, this is a beautiful photo!

(https://www.richis-lab.de/images/mouse/l14.jpg)
https://www.richis-lab.de/Howto_Licht.htm (https://www.richis-lab.de/Howto_Licht.htm)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 17, 2020, 08:46:43 pm
Thanks!  :-+

One of my favourites:

(https://www.richis-lab.de/images/486SX/16.JPG)

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
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy 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:

(https://www.richis-lab.de/images/555/26_04.jpg)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo 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!
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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 (https://www.richis-lab.de/decap-ofen.htm)

Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 17, 2020, 09:06:54 pm
Thanks!  :-+

One of my favourites:

(https://www.richis-lab.de/images/486SX/16.JPG)

Yep, that's even better!  :-+

What's a MEMS-Sensor, a solid state microphone?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy 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 (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 (https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL323.pdf)
And it looks really nice!  8)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo 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 (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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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 :)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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 (https://www.analog.com/media/en/technical-documentation/data-sheets/ADXL323.pdf)
And it looks really nice!  8)

https://www.youtube.com/watch?v=EALXTht-stg (https://www.youtube.com/watch?v=EALXTht-stg)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: TheUnnamedNewbie 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic 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?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: blueskull 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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 20, 2020, 07:11:31 pm
https://www.youtube.com/watch?v=EALXTht-stg (https://www.youtube.com/watch?v=EALXTht-stg)

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.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle 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".
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 20, 2020, 08:53:55 pm
https://www.analog.com/en/analog-dialogue/articles/does-my-voltage-reference-design-hold-water.html (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

Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on January 20, 2020, 10:43:54 pm
https://www.analog.com/en/analog-dialogue/articles/does-my-voltage-reference-design-hold-water.html (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

Meh, clickbait is everywhere these days  :)

Seriously though, the question was if the plastic is critical for protecting the IC from "ambient" chemicals. To my limited knowledge, it's not.

I've found this:

https://www.ti.com/lit/an/snoa300a/snoa300a.pdf (https://www.ti.com/lit/an/snoa300a/snoa300a.pdf)

Quote
Current plastic packages use various molding compound formulations consisting of epoxy resin, silica
fillers, and other minor constituents. The epoxy resin is non-hermetic and absorbs a small percentage of
moisture through diffusion. Eventually, an equilibrium develops between the moisture content inside the
package and the ambient moisture and temperature conditions. If enough moisture is present in the
package during surface mounting, the intense reflow heat turns the moisture into saturated steam (1). This
extreme pressure, accompanied by a drop in flexural strength of the molding compound at temperatures
reaching up to 240°C, may cause the package to fracture allowing the steam to escape (2). Once the
fracture occurs and the steam has escaped, a greater threat now exists to the device. The fracture allows
moisture and ionic contaminants such as sodium, potassium, or chlorine to infiltrate the plastic package,
potentially causing corrosion, and eventually failure of the device
. Therefore, moisture-induced cracking
must be prevented in order to maintain the long-term reliability of surface mount plastic packages.

Maybe Dave would like to investigate, sounds to me like a good theme for a cool for-nerds-only EEVBlog vidjeo: take some AVRs or something with the blinky sketch, decap them (cool die photos!) with noopy's oven system (Magic smoke!), let them run on a shelf 24/7 (boring), and see what happens: updates every Mailbag Monday.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 21, 2020, 09:09:28 pm
Maybe Dave would like to investigate, sounds to me like a good theme for a cool for-nerds-only EEVBlog vidjeo: take some AVRs or something with the blinky sketch, decap them (cool die photos!) with noopy's oven system (Magic smoke!), let them run on a shelf 24/7 (boring), and see what happens: updates every Mailbag Monday.

It would be a honor for me being mentioned in a Dave-Video!  8) :D
But I would have to bond new wires to a decapped die. That´s not possible for me...  :'(
Opening a metal-can-package and let it run with high humidity would be possibility...
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 29, 2020, 06:43:28 pm
Some people say that boiling chips in rosin gets the job done. Tried it today, here's the outcome:
[attach=1]
[attach=2]

There is some loss of volume, so it seems to work, but it certainly isn't fast. I boiled it for a good few minutes with no obvious effect so I cranked up temperature until it started to smoke. That was probably not a good idea |O

Or maybe it was? I don't even know if the attack occurred during those few minutes of slow boiling or due to the high heat at the end. Not sure if I want to do it again to find out.

I think I would rather simply drop the chip into an empty test tube and cook until it gives out the magic smoke.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 29, 2020, 07:10:39 pm
I have also heard from people trying rosin to decap chips.
In my view rosin doesn´t  really do the job. When people go to around 400°C they can destroy the epoxy but with this temperature you don´t Need rosin.  ;D
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 29, 2020, 08:25:33 pm
I actually wouldn't mind cooking it in some solvent which would cleanly strip all the decomposed epoxy in real time so that I don't need to do it manually. But it turns out that burning rosin is anything but clean ;)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: imo on January 29, 2020, 08:49:37 pm
You would need a pretty strong acid for your cooking :)

https://www.youtube.com/watch?v=mT1FStxAVz4 (https://www.youtube.com/watch?v=mT1FStxAVz4)

Title: Re: Decapping and Chip-Documentation - Howto
Post by: 3roomlab on January 29, 2020, 09:00:21 pm

I've found this:

https://www.ti.com/lit/an/snoa300a/snoa300a.pdf (https://www.ti.com/lit/an/snoa300a/snoa300a.pdf)



i dont have a steam pressure cooker
if i steam pressure cook a package to force water inside
after that, 400C roast the thing ... it should implode ? decap-lode? deplode ?
i wonder which is faster? roast only? or steamed roast?
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on January 30, 2020, 04:26:37 am
Heating a "wet" package sounds like a easy way to crack it. But my read is that there will only be one or more cracks. I´m afraid the epoxy will still be very hard to remove...
Title: Re: Decapping and Chip-Documentation - Howto
Post by: cncjerry on January 30, 2020, 08:32:37 am
Imo,  loved your video.  That was something new for me.  Wondering what to do with them, maybe earrings if you have enough of them. ,pretty darn cool.

As far as  probing,  if you use your cnc mill with a probe in the chuck, it would make it much easier..

Thanks  for posting,

Jerry







Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on January 30, 2020, 01:55:06 pm
You would need a pretty strong acid for your cooking :)
I wouldn't; rosin is good enough, as I said. But it's slow as molasses and easily turns into a dirty mess.

Maybe there are other organic acids that could work. So far I found two possible candidates: benzoic and adipic. Both have high boiling points and are safe at room temperature. Their structure is also simpler than rosin acids, so hopefully pyrolysis products would be cleaner.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on February 17, 2020, 04:52:43 pm
Another silly experiment: synthetic candle wax

1 hour at 280°C: no effect whatsoever
5 minutes at 350°C: no effect whatsoever

Conclusions:
Chemically, synthetic wax does nothing to epoxy.
280°C isn't sufficient to cause thermal decomposition.
350°C isn't sufficient to cause quick thermal decomposition.

Now I wonder how hot I got that rosin the last time when it partly etched the surface of the package. I didn't monitor temperature :palm:

On the upside, wax doesn't stain the glassware :)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on February 17, 2020, 10:22:13 pm
Another silly experiment: synthetic candle wax
...

Well an attempt doesn't hurt!  :-+
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on February 25, 2020, 10:52:33 am
A small update about my standard thermal decomposition process.

Shortly after my first post in this thread I bought a dedicated soldering iron heater for this duty. I chose the cheap and ubiquitous A1323 heater for Chinese 936 clones, which is similar to my iron's A1321 but with steel body and higher power.

[attachimg=1]

Manually PWM-ing a 24V power supply gets boring pretty fast and I wanted better temperature repeatability too. With a bit of experimentation I found that constant 12V supply produces just about perfect temperature, which smokes the chips nicely but doesn't cause the metal layer to melt. The temperature reported by the thermocouple inside the heater is some 600~700°C, depending on ambient temperature, airflow etc.

So the complete setup is: a 12V / 1A power brick driving a cheapass auction site soldering iron heater 8)

For DIP packages I use a two step process. First, the DIP is placed on the heater and tied with its leads to thoroughly bake the bottom. Then the bottom is crushed and the leads yanked out, leaving me with the upper half which contains the die. This is trimmed a bit and baked again, such that the die lies directly on the heater and all epoxy in contact with it gets roasted well. A few minutes suffices for each cycle. A bowl with water is placed below to catch anything falling from the heater and cool it down to safe temperature. A bit of thermal shock comes for free. Sometimes it causes spontaneous separation of the die after step 2.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on February 25, 2020, 03:14:42 pm
Looks good to me!  :-+
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on March 23, 2020, 07:47:01 pm
Another silly experiment: synthetic candle wax

1 hour at 280°C: no effect whatsoever
5 minutes at 350°C: no effect whatsoever
Funnily enough, this transistor still works. It has about 300 beta and over 100V Vceo (that's maximum I can test). Not bad for what the markings suggest should be a BC857.

I also performed additional testing with rosin. I boiled this no-name 78L05 for over two hours at about 270°C. To avoid messing up test tubes I used a thimble tied to my soldering iron heater with wires.

Nothing happened to the chip, only the surface got slightly matte. This chip also appeared to work afterwards, but I only tested quiescent current and output voltage under no load. Then I cracked it manually to see if it got any softer - nope, it didn't.
[attachimg=1]

Conclusion: rosin really requires crazy high temperature to work and absolute maximum ratings for storage temperature are only advisory ;D
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Mortymore on March 23, 2020, 08:23:24 pm
Christopher Tarnovsky's, Flylogic Engineering website used to have the best chip photos, but they are no more.  :'(
They were taken by IOActive

EDIT: Some info on the man: https://www.wired.com/2008/05/tarnovsky/ (https://www.wired.com/2008/05/tarnovsky/) (watch the video) ;)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on March 25, 2020, 05:23:09 am
Christopher Tarnovsky's, Flylogic Engineering website used to have the best chip photos, but they are no more.  :'(
They were taken by IOActive

EDIT: Some info on the man: https://www.wired.com/2008/05/tarnovsky/ (https://www.wired.com/2008/05/tarnovsky/) (watch the video) ;)

WOW !  :-+

https://www.youtube.com/watch?v=tnY7UVyaFiQ (https://www.youtube.com/watch?v=tnY7UVyaFiQ)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Mortymore on March 25, 2020, 08:13:01 am
I was once interested in the subject, so I'll leave some literature that I read at the time, in case someone is interested also.

From Cambridge University, Technical report 630: Semi-invasive attacks – A new approach to hardware security analysis (https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.pdf)

https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.html (https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-630.html)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on March 27, 2020, 03:04:45 pm
Some fun with 98% sulphuric acid.

I started safe, boiling only one drop of acid at a time ;) An idea based on the well known nitric acid process for live analysis. However, sulphuric acid appears less suitable for that. In addition to needing higher temperature, it tends to create a dry and brittle crust on the attacked surface. This crust is still strong enough that it can't simply be washed away, but rotten enough that on the next round the acid sinks into it and creeps all over the place instead of staying where it was put and doing the work. Everything turns messy and etching rate slows down so I cheated by scratching the crust away. This of course damaged the bonding wires, but at least I got a clean die after some hour of work ::)

The above process is a PITA and kinda pointless given the destruction of bonding wires, so I did the next chip the Zeptobars way: just dropped it in acid and boiled until everything turned into black sticky goo. This was a TO92 package and it only took a few minutes of cooking and tittle acid. I used the same thimble and soldering iron heater setup as in my previous experiments and heater power was also the same, which should yield about 270°C. I didn't measure exact temperature for lack of suitable sensor. One may think that a metal vessel would be destroyed by acid, but in practice corrosion is very low. I will see how long it lasts. At least it isn't going to crack and shatter from heat like glass could do. I placed a steel bowl below to catch spills and overflows. Overflows are possible because the reaction produces plenty of foam and bubbles.

One of the gold bonding wires survived the whole journey and somehow remained attached, but on the photo it looks like bonding pads may have been etched away by acid. I will never know for sure because I crushed the die trying to remove it from the metal carrier :palm: Admittedly I was being sloppy and used water instead of acetone for cleaning, but I'm not sure if the pads made it even to that point.

Acid also proved effective against stubborn epoxy residue on dice extracted by heating. I managed to clean up a few of those.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on March 28, 2020, 08:29:30 pm
Interesting. Thanks for sharing.  :-+

For me that´s too messy and dangerous.  :scared:
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on August 13, 2020, 08:23:34 pm
On the imaging front, I built a simple beam splitter to experiment with illumination through the lens. It's a small cardboard box painted black to absorb reflections with a 45° angled half-mirror inside and a hole in one wall.

The half-mirror is a piece of a "mirror" protection foil for smartphone displays. These foils are supposed to make the screen reflective when the LCD is blank but still be transparent enough for normal use. It probably isn't exactly 50% reflective and 50% transmissive, but whatever, good enough for us.

(https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/?action=dlattach;attach=1046672;image)

The box goes on top of the lens. Light is supplied through the hole in the side, bounces off the mirror downwards, passes through the lens back and forth and passes through the mirror to be observed from above. Half of the entering light passes through the mirror and is dumped on the wall and half of the light from the lens is reflected back towards the illumination source, but 25% efficiency is not the end of the world.

I tried it in combination with my favorite HD webcam lens, a lousy VGA webcam lens and a 10x biological microscope objective. A few sample images follow.

The webcam lenses have enough magnification that one can simply use them as a loupe and look directly into the lens. Magnification is good enough for low density analog ICs and with the HD lens and with some squinting I can even follow the super-die-shrunk Chinese LM358 chips. The first two images show how the two lenses perform on a TI NE5532 die. My camera couldn't capture the full field of view visible with naked eye and the image turned out a bit dark, but it gives a glimpse of the resolution available with the HD lens.

The third image is the same but with the 10x microscope objective. Magnification is very low. This lens could only possibly be usable for photography, i.e. projection onto a camera sensor at a sufficiently far distance, or as part of a compound microscope with an additional eyepiece lens. Go figure ;)
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on August 13, 2020, 08:28:18 pm
And again: Very interesting!  :-+
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on August 16, 2020, 11:53:53 am
New version. This time with a larger box that holds a webcam sensor board to enable viewing on a computer and taking pictures.

(https://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/?action=dlattach;attach=1048106;image)

An improvement was necessary in the way that the part of illumination stream which fails to reflect from the mirror is "wasted". The light is still projected on the rear wall, but the larger box allows this wall to be farther away and hidden from the sensor's view. The camera PCB has its original lens tube attached and the tube blocks the light scattered by the "waste wall" from reaching the sensor, except for the part which reflects back exactly towards the mirror.

Another improvement is the addition of Köhler illumination. I hoped it wouldn't be necessary but it does improve contrast considerably by reducing stray light. The lens on the illumination entrance is so-called collector lens, because it collects light from the illuminator, refracts it and projects a focused image of the illuminator straight into the aperture of the main lens. This way all of the light which reaches the entrance hole ends up where it belongs instead of bouncing around inside the box. The collector lens should be at the same distance from the mirror as the sensor, slightly larger than the sensor and its focal length must be shorter than the distance to the main lens (or it wouldn't focus properly). At least that's the theory, in practice the distance is only approximate and I adjust LED lamp position empirically for best contrast.

This setup takes some decent quality images already and is relatively reliable, main problems at this point being precision alignment of everything for uniformity of focus and illumination across the field.

By reducing the size of the light source (a 3mm LED) I got this image of the Chinese RC4558 which appears even a bit more colorful than normally. Not sure what happens here.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: GeorgeOfTheJungle on August 16, 2020, 12:06:42 pm
Nice!
Title: Re: Decapping and Chip-Documentation - Howto
Post by: Noopy on August 16, 2020, 01:35:15 pm
That's a nice construction. I like getting good results out of low cost designs!
I think some 3D printed casing would improve the quality a lot.
Title: Re: Decapping and Chip-Documentation - Howto
Post by: magic on August 17, 2020, 12:37:00 pm
I think some 3D printed casing would improve the quality a lot.

For real photography time is probably better spent figuring out how to put this (or a better?) beamsplitter between a real microscope lens and a real camera.

Better construction would improve flatness of focus (I think the bottom right corner of my 5532 image is a bit soft, for example), hopefully uniformity of brightness, and maybe contrast a bit. But you are still left with a high crop, low resolution and noisy sensor, questionable demosaicing (regular dot artifacts appear in a few places on my shots) and auto white balance and sharpening that cannot be controlled. My webcam also lacks manual exposure mode so it can't even be used for panorama stitching.

I made this webcam mod to test the beamsplitter concept and for direct inspection and reverse engineering. If some corner is a bit out of focus, I will simply move the camera or tap my finger on the PCB to realign it. BTW, a big nuisance is the USB cable which pulls on the board. I tried stripping the last 10cm of external jacket and shield or using a piece of ribbon cable for the last 10cm but this breaks high speed USB.

The lens is close to its limits too. I estimate my resolution at about 0.5µm/px and an f/2 lens resolves maybe a line pair per 1.5µm so I'm already sampling at 150% Nyquist density. Maybe some minimal improvement could be gained by doubling the pixel density, but beyond that there is no hope without a better lens.