iPhone 4 Gyroscope Teardown

To grasp the subsequent procedures, it's essential to first comprehend the function of the gyroscope.
An iPhone 4 incorporates a gyroscope, a component defined by Wikipedia as a device that utilizes the principle of angular momentum conservation to either determine or stabilize an object's orientation.
The device pictured on the left, a mechanical gyroscope, employs a central rotating rotor to sense alterations in its angular position.
The iPhone 4 incorporates a MEMS gyroscope, which is a miniaturized, electronically controlled gyroscope that functions through vibration.

These miniature systems combine electronic and mechanical elements within a single, highly compact device.
The fundamental architecture of a MEMS device incorporates an application-specific integrated circuit alongside a sensor fabricated from micro-machined silicon.
The iPhone 4 incorporates an STMicroelectronics-designed MEMS gyroscope, identified as the AGD1 2022 FP6AQ chip.

According to Chipworks' analysis, the iPhone 4's internal MEMS gyroscope closely matches the specifications of a readily available STMicroelectronics L3G4200D gyroscope.
The MEMS die, designated GK10A, which is present within the L3G4200D, is depicted in the image on the left.
Application of a drive signal causes the proof mass plate to vibrate, or oscillate.
Coriolis forces cause the proof mass to shift along the X, Y, and Z axes when the phone's orientation changes; this movement is detected by an ASIC processor utilizing capacitor plates positioned beneath the proof mass and finger capacitors situated around the package's perimeter.

The GK10A MEMS die’s minuscule capacitive outputs are transformed into a digital signal by the V654A ASIC die, located on the left, before being transmitted to the iPhone 4.
The information generated serves purposes such as controlling a vehicle’s steering or directing targeting systems within iPhone 4 video games.
To calculate the applied angular rate in degrees per second, mechanical engineers should divide the oscillator's output voltage, measured in millivolts, by the gyroscope's sensitivity, which is typically expressed as millivolts per degree per second.

Although these integrated circuits are not components of the iPhone 4 itself, they are presented to demonstrate the complex architecture found within MEMS gyroscopes.
Microscopic imaging using a scanning electron microscope (SEM) reveals the ST LYPR540AH Tri-axis MEMS gyroscope's structure, as depicted in the accompanying photographs.
Achieving the precision essential for dependable sensor functionality necessitates highly intricate and delicate fabrication processes when manufacturing MEMS devices.
To fabricate most MEMS devices, a film is first applied, then selectively masked and etched, eliminating unwanted material and leaving the desired structure.

The intricate oscillator designs found in MEMS gyroscopes, exemplified by the Kionix gyroscope, are microscopic and concealed under a black protective layer.
Refer to the images to appreciate the incredibly small size of these components; for example, the oscillator in the second image measures roughly one-quarter the width of a typical human hair, equivalent to the combined width of three stacked red blood cells.

The SiTime SI8002AC integrated circuit's external housing has been detached in this illustration.
The oscillator's raw signals are processed by an ASIC, which is mounted directly above the oscillator and secured with wire bonds to facilitate signal transmission. This combined assembly is then hermetically enclosed within the plastic housing.
An X-ray image reveals the stacked die arrangement within a Bosch BMA 220, illustrating how wire bonds establish electrical connections between the dies and extend to the ball grid array.
To increase the density of components and functionality within a limited area, chip producers utilize die stacking techniques, a critical design element particularly relevant in compact devices like the iPhone 4, where available space is severely restricted.

Microscopic images, obtained using scanning electron microscopy, depict the internal oscillator of the SiTime SI8002AC.
The creation of Micro-Electro-Mechanical Systems (MEMS) demands expertise across numerous disciplines, encompassing industrial, materials, mechanical, electrical, chemical, computer, and software engineering, as their construction and deployment represent a convergence of electrical and mechanical principles.
We gratefully acknowledge Chipworks for supplying the detailed photographs essential for this disassembly analysis.