Electronics > Projects, Designs, and Technical Stuff

Decapping and Chip-Documentation - Howto

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Noopy:

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





I´ve structured the topic in different articles:

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

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

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

4. Picture tuning
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

magic:

--- Quote from: Noopy on September 03, 2019, 10:09:03 pm ---1. Decapping
https://www.richis-lab.de/Howto_Decap.htm
--- End quote ---
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.


--- Quote from: Noopy on September 03, 2019, 10:09:03 pm ---2. Optics
https://www.richis-lab.de/Howto_Optik.htm

3. Positioning and ligths
https://www.richis-lab.de/Howto_Licht.htm
--- End quote ---
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/

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.

Noopy:
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:

Noopy:
Hi all!


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


I have built an ofen for the decapping:




Works quite fine and reproducible!  :-+




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


 :popcorn:

magic:
That's seriously cool and much better than anything I have ever done :-+

BTW, I actually like that smell ;D

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