Author Topic: Decapping and Chip-Documentation - Howto  (Read 4945 times)

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Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #50 on: January 20, 2020, 10:43:54 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

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

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.
The further a society drifts from truth, the more it will hate those who speak it.
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #51 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...

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #52 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.
 
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #53 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

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #54 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 ;)
 

Online imo

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Re: Decapping and Chip-Documentation - Howto
« Reply #55 on: January 29, 2020, 08:49:37 pm »
You would need a pretty strong acid for your cooking :)



« Last Edit: January 29, 2020, 08:52:14 pm by imo »
 

Offline 3roomlab

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Re: Decapping and Chip-Documentation - Howto
« Reply #56 on: January 29, 2020, 09:00:21 pm »

I've found this:

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?
to aleph null and beyond?
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #57 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...

Offline cncjerry

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Re: Decapping and Chip-Documentation - Howto
« Reply #58 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







 

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #59 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.
 

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #60 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 :)
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #61 on: February 17, 2020, 10:22:13 pm »
Another silly experiment: synthetic candle wax
...

Well an attempt doesn't hurt!  :-+

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #62 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.
« Last Edit: February 25, 2020, 11:07:45 am by magic »
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #63 on: February 25, 2020, 03:14:42 pm »
Looks good to me!  :-+

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #64 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
« Last Edit: March 23, 2020, 08:26:56 pm by magic »
 

Offline Mortymore

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Re: Decapping and Chip-Documentation - Howto
« Reply #65 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/ (watch the video) ;)
« Last Edit: March 23, 2020, 08:26:33 pm by Mortymore »
 
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Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #66 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/ (watch the video) ;)

WOW !  :-+

The further a society drifts from truth, the more it will hate those who speak it.
 
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Offline Mortymore

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Re: Decapping and Chip-Documentation - Howto
« Reply #67 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.html
 
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Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #68 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.
 
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #69 on: March 28, 2020, 08:29:30 pm »
Interesting. Thanks for sharing.  :-+

For me that´s too messy and dangerous.  :scared:

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #70 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.



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 ;)
 
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Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #71 on: August 13, 2020, 08:28:18 pm »
And again: Very interesting!  :-+

Offline magic

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Re: Decapping and Chip-Documentation - Howto
« Reply #72 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.



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.
 

Offline GeorgeOfTheJungle

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Re: Decapping and Chip-Documentation - Howto
« Reply #73 on: August 16, 2020, 12:06:42 pm »
Nice!
The further a society drifts from truth, the more it will hate those who speak it.
 

Offline Noopy

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Re: Decapping and Chip-Documentation - Howto
« Reply #74 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.


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