It’s been interesting to watch the evolution of cell phones in the last few decades. I distinctly remember watching Steve Job’s key note address in 2007 when he introduced the iPhone. At that point there wasn’t a single unified design language for mobile phones - most had physical keyboards, some slid open, others flipped open, and there was a range of styles and designs. The release of the iPhone caused the mobile phone landscape to slowly converge toward a single form - a keyboard-less phone with a glass touch screen and few physical buttons. While smart phones evolved within this form, they haven’t strayed far from the concept presented by the original iPhone.

With the recent release of the iPhone 11, I’ve become acutely aware of just how far smartphones have come in the last decade. I decided to compare an early model iPhone to the more recent models to see how the design has evolved and iterated over time. I managed to purchase an iPhone 3GS that was working and in remarkably good condition for a whole 4£ and decided to use it for my first teardown.

The iPhone 3GS (released 2009) is the third release in the iPhone product line and is an update to the 3G (released 2008). It features a rounded polycarbonate shell which came in both black and white. The shell fits nicely in my palm and is comfortable to use. On the left edge of the phone there is a volume rocker and a mute switch, along the top there is a push button for locking the phone, and on the face below the screen there is a single home button.

The screen is released by removing two screws along the bottom edge of the phone and using a suction cup to pull up on the screen which pops it out of the bezel. Before the assembly can be fully removed, three flex cables connecting it to the main logic board are unclipped.

The screen is held in the iPhone body with two sheet metal brackets that are insert molded into the plastic structure of the screen. These brackets serve two purposes: Firstly, to interface with tabs that are positioned along the inside of the iPhone bezel (circled below in red) that are responsible for holding the screen firmly in place, and secondly, to serve as a mounting interface for the LCD screen. Screws pass through these brackets and into weld nuts on the LCD shielding.

The screen is positioned in the Z-axis on a lip that is machined into the iPhone’s bezel. It is then finally secured in place with two screws that travel through the bottom of the phone’s polycarbonate shell and into two small metallic parts molded into the screen’s plastic structure.

I’m constantly amazed how well these components fit together. Even without the two screws that secure the screen to the phone body, the iPhone feels solid and cohesive without a noticeable gap or seam between the edge of the screen and the bezel.

Having seen the internals of several other iPhones, I can’t hep but notice how different the 3GS looks already. The screen assembly is fairly similar to more recent models, however the main compartment looks remarkably different:

• The logic board sits on top of the battery, which is not visible.

• There are some (crooked) stickers indicating the order of flex cable removal, part numbers, and other information.

• Flex cables are copper coloured and translucent, not black.

• There is not a single Apple logo insight.

• We can see peaks of the main logic board under the EMI shielding which is teal - not black.

As a comparison, here are the iPhone 3GS and the iPhone 11 side by side. It’s clear Apples designers have made efforts to make the internals aesthetic and uniform.

Continuing on, I remove the logic board by unscrewing 7 screws, removing several flex cables, and removing 2 coaxial antenna cables. The board itself is positioned in the cavity by two pins molded into the iPhone’s plastic body, one top right just above a screw and the other bottom left (covered in the image below by connector 4). This is a common technique used to self-fixture (or position) components before screws have been inserted. By using two tight fitting pins, the board is constrained in all nearly all degrees of freedom before any screws are installed. The screws are then used to constrain the remaining DOF by holding the board in place in the phone.

Without the pins, the position of the board in the phone is dictated by the screws and would require more careful attention to the dimensioning, tolerancing, and/or screw installation sequence.

After removing the battery, the haptic feedback motor unscrews from a bracket spot welded to the bezel. This motor generates haptic feedback by rotating an eccentric weight on a shaft which creates vibration. I must admit, the new Taptic Engine that Apple now uses has significantly improved the quality and responsiveness of the feedback produced. Before the teardown, I played with the phone a bit and could feel the slight lag as the motor spun up to create vibration. The new Taptic system uses an electro magnet to move a weight back and forth between two springs which creates a much sharper, livelier vibration due to the lack of spin up time.

Two small tapered coil springs can be seen on the motor assembly. These interface with two contact patches on the bottom of the iPhone logic board and ensure contact remains even during vibration.

Next the camera module comes out with the removal of a single screw which holds a tiny bracket over that keeps the module in place (Below left). This module sits inside a plastic housing which is glued onto to the iPhone body. I pry it off to reveal a tiny bezel under the housing which appears to be plastic with a metallic finish around the visible edge (Below right).

With the camera module removed, I disassemble the power button assembly along the top edge of the phone. The assembly is comprised of a metallic button with a plastic overmold and a wire clip that is free to rotate, this button interacts with a dome switch that is glued onto a plastic bracket. The plastic bracket is screwed directly to the iPhone case and traps the button between the case and the dome switch. When a user pushes the button it then pushes the dome switch, which registers the action and also provides the spring force that returns the button to its original position.

The design of the button is interesting. The wire installed on it can pivot 90 degrees to one side and about 45 degrees to the other (from the vertical position shown below right). When installed, this bent wire is constrained from moving in all directions by the plastic bracket and the iPhone casing, however it can rotate axially. It’s purpose is to reduce button “slop” by forcing the button to remain perpendicular to the direction of travel, even if pressed off center.

Since the wire is constrained in all directions, it cannot tilt, and since it is attached to the button, any off center push of the button will be unable to tilt the wire and therefore, also the button. However, since the wire can rotate, when the button travels downward the wire needs only to rotate in position to allow the travel to occur.

I really love this design, it shows how much effort has gone into even the smallest parts of this phone. While a button with some slop does not necessarily cause any problems, it does show a lack of attention to detail and engineering effort. These details are important as they communicate an overall sense of product quality to the consumer. This button design was carried on through to the iPhone 6S and was modified for water resistance for the iPhone 7 onwards, the new design however still features this rotating wire.

Next I ventured down to the bottom of the phone where I remove the “everything” module. This module contains the 30-pin connecting port, microphone, speaker outputs, and antenna. It’s held in by just three screws and comes out fairly easily - surprisingly modular! This component has since become a series of individual assemblies linked by flex cable, most likely to save space taken up by the redundant module enclosure.

The antenna is actually just stuck onto this module like a sticker and is peeled off fairly easily. It’s positioned using two plastic nubs on the module which align to a hole and a slot on the antenna. Also interesting is there’s a gold tang on the flex cable (Below left) which also interfaces with the bezel for a ground.

The top of the phone has another everything module, however it isn’t contained within a plastic casing, instead a long flex cable links the power button dome switch, 1/8” audio jack (R.I.P.), the mute switch, and the volume rocker dome switches.

In the corner I remove a bracket which serves many different purposes and is quite unique. There’s a really interesting geometry to it that points to die casting and the metal appears quite dull, so I’d reckon this is a cast zinc alloy. These alloys have a low melting point are quick/cheap to mold. They also have high dimensional stability, removing the need for multiple secondary operations.

There is a toggle switch heat staked to the casting that is operated by the mute switch which sits between the iPhone shell and the bracket.

With this multi-part flex cable removed, I’ve pretty much taken everything out of the iPhone and I now set my attention to the bezel. The bezel is a stainless steel part that is glued onto the iPhone casing and took a fair bit of prying and persuading to be removed. Once removed, we see the multitude of features and parts machined into it or welded onto it. There are holes drilled and tapped directly into the steel and also multiple brackets that have been laser spot welded onto it.

Below we see a bracket welded onto the frame that holds the screen assembly in place. The bracket has 5 tabs that are cantilevered off the part which align to the rectangular slots in the screen brackets, providing a spring force that holds the screen in the phone.

We can see a two holes on the bracket which appear to serve no purpose. These are likely fixturing features used to align the bracket in a fixture during the welding process. This increases process reliability and repeatability by ensuring the bracket is aligned perfectly with each weld.

With the last component removed its time for some exploded shots!

With that the phone is now as torn down as far as possible without being completely destructive. I could have gone a few steps further by tearing through the LCD layers and removing EMI shielding from the logic board, but I preferred to reassemble the phone after and keep it for further reference. I was able to put everything back together and turn it on at the end which was a pleasant surprise. All screws back in their correct places and only a single tab broken from the bezel!

After performing this teardown, I watched a video of the first iPhone being torndown. The internal design is night and day different to the 3GS yet the exterior looks identical. It’s amazing how much iteration goes on under the surface of these devices while the external form appears the same.