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IC Decapping: The Process

As I’ve been posting some photos of decapped ICs lately, I thought I’d share the process I use personally for those that might want to give it a go 😉

The usual method for removing the epoxy package from the silicon is to use hot, concentrated Nitric Acid. Besides the obvious risks of having hot acids around, the decomposition products of the acid, namely NO² (Nitrogen Dioxide) & NO (Nitrogen Oxide), are toxic and corrosive. So until I can get the required fume hood together to make sure I’m not going to corrode the place away, I’ll leave this process to proper labs ;).

The method I use is heat based, using a Propane torch to destroy the epoxy package, without damaging the Silicon die too much.

TMS57002 Audio DSP
TMS57002 Audio DSP

I start off, obviously, with a desoldered IC, the one above an old audio DSP from TI. I usually desolder en-masse for this with a heat gun, stripping the entire board in one go.

FLAMES!
FLAMES!

Next is to apply the torch to the IC. A bit of practice is required here to get the heat level & time exactly right, overheating will cause the die to oxidize & blacken or residual epoxy to stick to the surface.
I usually apply the torch until the package just about stops emitting it’s own yellow flames, meaning the epoxy is almost completely burned away. I also keep the torch flame away from the centre of the IC, where the die is located.
Breathing the fumes from this process isn’t recommended, no doubt besides the obvious soot, the burning plastic will be emitting many compounds not brilliant for Human health!
Once the IC is roasted to taste, it’s quenched in cold water for a few seconds. Sometimes this causes such a high thermal shock that the leadframe cracks off the epoxy around the die perfectly.

All Your Die Belong To Us
All Your Die Belong To Us

Now that the epoxy has been destroyed, it breaks apart easily, and is picked away until I uncover the die itself. (It’s the silver bit in the middle of the left half). The heat from the torch usually destroys the Silver epoxy holding the die to the leadframe, and can be removed easily from the remaining package.

Decapped
Decapped

BGA packages are usually the easiest to decap, flip-chip packages are a total pain due to the solder balls being on the front side of the die, I haven’t managed to get a good result here yet, I’ll probably need to chemically remove the first layer of the die to get at the interesting bits 😉

Slide
Slide

Once the die has been rinsed in clean water & inspected, it’s mounted on a glass microscope slide with a small spot of Cyanoacrylate glue to make handling easier.

Some dies require some cleaning after decapping, for this I use 99% Isopropanol & 99% Acetone, on the end of a cotton bud. Any residual epoxy flakes or oxide stuck to the die can be relatively easily removed with a fingernail – turns out fingernails are hard enough to remove the contamination, but not hard enough to damage the die features.

Once cleaning is complete, the slide is marked with the die identification, and the photographing can begin.

Microscope Mods

I had bought a cheap eBay USB microscope to get started, as I can’t currently afford a proper metallurgical microscope, but I found the resolution of 640×480 very poor. Some modification was required!

Modified Microscope
Modified Microscope

I’ve removed the original sensor board from the back of the optics assembly & attached a Raspberry Pi camera board. The ring that held the original sensor board has been cut down to a minimum, as the Pi camera PCB is slightly too big to fit inside.
The stock ring of LEDs is run direct from the 3.3v power rail on the camera, through a 4.7Ω resistor, for ~80mA. I also added a 1000µF capacitor across the 3.3v supply to compensate a bit for the long cable – when a frame is captured the power draw of the camera increases & causes a bit of voltage drop.

The stock lens was removed from the Pi camera module by careful use of a razor blade – being too rough here *WILL* damage the sensor die or the gold bond wires, which are very close to the edge of the lens housing, so be gentle!

Mounting Base
Mounting Base

The existing mount for the microscope is pretty poor, so I’ve used a couple of surplus ceramic ring magnets as a better base, this also gives me the option of raising or lowering the base by adding or removing magnets.
To get more length between the Pi & the camera, I bought a 1-meter cable extension kit from Pi-Cables over at eBay, cables this long *definitely* require shielding in my space, which is a pretty aggressive RF environment, or interference appears on the display. Not surprising considering the high data rates the cable carries.
The FFC interface is hot-glued to the back of the microscope mount for stability, for handheld use the FFC is pretty flexible & doesn’t apply any force to the scope.

Die Photography

Since I modified the scope with a Raspberry Pi camera module, everything is done through the Pi itself, and the raspistill command.

Pi LCD
Pi LCD

The command I’m currently using to capture the images is:
raspistill -ex auto -awb auto -mm matrix -br 62 -q 100 -vf -hf -f -t 0 -k -v -o CHIPNAME_%03d.jpg

This command waits between each frame for the ENTER key to be pressed, allowing me to position the scope between shots. Pi control & file transfer is done via SSH, while I use the 7″ touch LCD as a viewfinder.

The direct overhead illumination provided by the stock ring of LEDs isn’t ideal for some die shots, so I’m planning on fitting some off-centre LEDs to improve the resulting images.

Image Processing

Obviously I can’t get an ultra-high resolution image with a single shot, due to the focal length, so I have to take many shots (30-180 per die), and stitch them together into a single image.
For this I use Hugin, an open-source panorama photo stitching package.

Hugin
Hugin

Here’s Hugin with the photos loaded in from the Raspberry Pi. To start with I use Hugin’s built in CPFind to process the images for control points. The trick with getting good control points is making sure the images have a high level of overlap, between 50-80%, this way the software doesn’t get confused & stick the images together incorrectly.

Optimiser
Optimiser

After the control points are generated, which for a large number of high resolution images can take some time, I run the optimiser with only Yaw & Pitch selected for all images.

Optimising
Optimising

If all goes well, the resulting optimisation will get the distance between control points to less than 0.3 pixels.

Panorama Preview
Panorama Preview

After the control points & optimisation is done, the resulting image can be previewed before generation.

Texas Instruments TMS67002
Texas Instruments TMS67002

After all the image processing, the resulting die image should look something like the above, with no noticeable gaps.

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Wearable Raspberry Pi Part 1

Overview
Overview

Here is the project I’m currently working on. A completely wearable computing platform based on the Raspberry Pi & the WiFi Pineapple.

Above can be seen the general overview of the current unit.

On the left:

  • Alfa AWUS036NHA USB High Power WiFi Network Interface
  • 512MB Model B Raspberry Pi, 16GB SD card, running Raspbian & LXDE Desktop. Overclocked to 1GHz.

On the right:

  • WiFi Pineapple router board
  • USB 3G card.

The WiFi, Pineapple & 3G all have external antenna connections for a better signal & the whole unit locks onto the belt with a pair of clips.
The Raspberry Pi is using the composite video output to the 7″ LCD I am using, running at a resolution of 640×480. This gives a decent amount of desktop space while retaining readability of the display.

The case itself is a Pelican 1050 hard case, with it’s rubber lining removed. The belt clips are also a custom addition.

Connections
Connections

Here are the connections to the main unit, on the left is the main power connector, supplying +5v & +12v DC. The plug on the right is an 8-pin connection that carries two channels of video, mono audio & +12v power to the display.
Currently the only antenna fitted is the 3G.

Connectors
Connectors

Closeup of the connections for power, audio & video. The toggle switch is redundant & will soon be replaced with a 3.5mm stereo jack for headphones, as an alternative to the mono audio built into the display.

Test Run
Test Run

Current state of test. Here the unit is running, provided with an internet connection through the Pineapple’s 3G radio, funneled into the Pi via it’s ethernet connection.

Pi Goodness!
Pi Goodness!

Running on a car reversing camera monitor at 640×480 resolution. This works fairly well for the size of the monitor & the text is still large enough to be readable.

 

Stay tuned for Part 2 where I will build the power supply unit.

 

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Motorola V360v

Front
Front

Here is a more modern phone, the Motorola V360v. Features include Dual screens, 640×480 VGA camera, full col

our TFT Main LCD, SD-Micro slot.
Here on the back the grey scale LCD can be seen, with the camera lens to the right of the Motorola logo

Keypad
Keypad

Here the phone is opened showing the keypad & the full colour TFT LCD display.

Battery Compartment
Battery Compartment

Here the battery is removed from the unit, showing the SIM connector. The antenna cover is still on at the bottom.

Antenna
Antenna

The antenna cover has been removed in this shot, the antenna is the white section at the bottom, With the loudspeaker & the external antenna connector hidden at the right.

PCB
PCB

Here is the main PCB. Parts from left are the Bluetooth module at the top, supplied by Broadcom, the SD Card socket at the bottom. Main CPU next to that is the Freescale SC29343VKP. Above right of the CPU is the Freescale SC13890P23A Charger, Power & Audio IC. Below is the SIM card socket. Under the main CPU is the Intel Flash memory IC. ICs inside the shields are the RF sections for transmit & receive.

Cover Removed
Cover Removed

Rear of the display unit showing the monochrome LCD. The camera module on the bottom left. Ear speaker on the far right of the unit.

Main LCD
Main LCD

Main colour TFT LCD.

Camera
Camera

Camera module removed from the LCD unit.

Vibra-Motor
Vibra-Motor

The vibration motor attached to one of the LCD looms.