This video details the extensive setup and utilization of a high-end Mitutoyo FS70L metallurgical microscope for semiconductor photography and micro-machining. The presenter addresses several challenges in making the microscope fully operational, including building a stable stand, configuring illumination (replacing a faulty halogen unit with a custom LED source), and aligning the camera and eyepieces. A significant portion of the video is dedicated to motorizing the XY stage and Z-axis for automated scanning and focus stacking using a Raspberry Pi Pico W, showcasing the custom software and hardware integration. Various integrated circuits are then decapped using mechanical, acid, and rosin methods, followed by high-resolution imaging and stitching to reveal their intricate internal structures. Finally, the unique laser micro-machining capability of the FS70L model is demonstrated for precision material modification, like resistor trimming.
Setting Up a High-Precision Metallurgical Microscope for IC Photography and Laser Micro-Machining
0:00 Introduction to the Mitutoyo FS70L Microscope: The video introduces a specialized metallurgical microscope, designed for viewing metals and integrated circuits using epi-illumination (light delivered through the objective). The goal is to perform semiconductor photography and understand IC failures.
2:01 Initial Setup Challenges: The microscope, acquired as a "decapitated head," requires a custom stand, a dedicated light source, alignment of binocular eyepieces and camera, and motorization for X, Y, and Z axes. Image contrast issues with high-intensity illumination are also noted.
3:36 Microscope Stand and Vibration Isolation: A 400kg vibration-isolating optical breadboard is used as a foundation, with a Unistrut-style vertical mounting plate fabricated to hold the microscope head.
5:53 Long Working Distance Objectives: The Mitutoyo objectives, designed for the semiconductor industry, feature exceptionally long working distances (e.g., 17mm for a 50x objective), allowing for the integration of XY motion stages and wafer probes.
7:04 Binocular and Camera Alignment: The presenter addresses misalignments in the binocular eyepieces (caused by thread locker residue) and a Basler ACA2500-20GC C-mount camera. Achieving perfect focus and field-of-view alignment between the camera and eyepieces proves challenging and objective-dependent due to optical path differences.
10:48 Camera Heat Sinking and Compromises: The Power-over-Ethernet camera generates significant heat, relying on its C-mount threads for heat sinking. A 3D-printed plastic adapter, while allowing for better alignment, risks overheating, prompting a need for metal mounting.
13:22 Objective Dependence: It's discovered that perfect alignment and focus are achieved for only one objective (50x M Plan NIR); other objectives (e.g., 10x M Plan Apochromatic) exhibit different characteristics, possibly due to the microscope's infinity-corrected system and how objectives influence upstream focal lengths.
14:35 Motorization for Automated Scanning: The video moves to motorizing the XY stage using a donated Carl Zeiss Microte PH1-150 wafer probe head (later swapped for a Meritzo Vetsler EK14 auto stage with stepper motors) and the Z-axis (friction-grip stepper motor) for focus stacking and panorama stitching.
17:16 PCB Design and Microcontroller: A custom PCB, reused from a previous project, features multiple stepper drivers connected to a Raspberry Pi Pico W, enabling Wi-Fi control via a MicroPython-based web server for motion control.
20:15 Z-axis Precision: The Z-axis motor setup achieves a resolution of 8-9 micrometers per micro-step, though some backlash is observed when changing direction.
21:25 Custom LED Illumination Source: The faulty original halogen light source is replaced with a custom LED solution using "laser LEDs" (small spot size, flat front) for efficient coupling to the fiber bundle. A constant current driver ensures stable, PWM-free illumination.
26:26 Solving Image Contrast Issues: High-intensity illumination leads to washed-out images due to internal reflections. This is resolved by applying a sample of "Vantablack"-like anti-reflective material to the sidewall of the optical path.
28:05 IC Decapping Techniques: The presenter demonstrates multiple methods for removing the epoxy molding from ICs:
Heat and Mechanical Breakage (29:08): Overheating the part (e.g., 400°C hot air) makes the epoxy rubbery, allowing it to be broken off.
Nitric Acid (31:49): Using 68% nitric acid at high temperatures (150°C) to dissolve the epoxy, though it's slow and requires controlled conditions.
Colophony Rosin (32:53): Slow cooking the part in molten soldering flux to interact with polymer links in the epoxy.
34:34 Automated Image Acquisition and Stitching: A Python script controls the X, Y, Z movements of the motorized stage, performs autofocus (using the Laplacian function for sharpness), and captures images with overlap. Gigabytes of images are then stitched together using Fiji (a version of ImageJ) to create high-resolution panoramas of IC dies.
36:27 Examples of Semiconductor Dies: The video showcases detailed images of various decapped ICs, including:
An 80s ICL7650 chopper-stabilized op-amp.
A modern Analog Devices ADA4523 autozero op-amp, highlighting its complexity.
An Analog Devices ADXL 193 MEMS accelerometer with moving parts (found to be photosensitive).
An Analog Devices AD71772 32-bit sigma-delta ADC (the largest image handled).
A Texas Instruments JFE 2140 ultra-low-noise matched JFET pair.
A Texas Instruments OPA 2192 CMOS op-amp with eTrim technology.
A $900 Analog Devices ADIS 16480 IMU, revealed to contain more common components ($100 worth) when disassembled.
Analog Devices ADXRS 295 gyroscopes.
48:06 FS70L Laser Micro-Machining Capability: The "L" in FS70L stands for its unique ability to deliver "angry photons" – a laser source – through its internal optics for micro-machining. This allows for precision material removal.
51:00 Practical Application: Laser Trimming Resistors: The laser is demonstrated for fine-tuning resistance values on a decapped NOMC63 thin-film resistor array by carving into narrow or wide sections of the resistors for coarse or fine adjustments.