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iPod Evolution

May 2022

The iPod was a groundbreaking piece of consumer electronics. With new generations introduced every year after its launch in 2001, the iPod product family reflected a period of rapid development in processing, storage, displays, and user interfaces, anticipating the iPhone’s blockbuster release in 2007.

This month we explore the evolution of the iPod from the inside out with our Lumafield Neptune CT scanner, guided by none other than Tony Fadell, the inventor of the iPod and the founder of Nest.

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Intro image for the scan.

iPod Classic (1st Generation)

October 2001

The iPod is almost old enough to buy a beer. Just over 20 years ago, Apple was a much smaller computer company taking a bold step into the established but fragmented market for MP3 players. Incumbent music players had awkward user interfaces, limited capacities, and low-quality construction. Let’s see what made Apple’s product special.

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MP3 players in the late 1990s tended to look like TV remotes–dotted with single-function buttons and switches. Apple’s entry stood out for its clean, reserved design and its spinning wheel that made it easy to navigate through thousands of songs with just a thumb. The high-quality feel of the wheel comes down to the substantial bearing at its center; in addition to giving the wheel an addictively smooth spin, it also prevents it from rocking side-to-side.

Most late-1990s MP3 players used low-capacity flash memory or large 2.5” hard disk drives (HDD). Apple worked with Toshiba to get an HDD in a pocketable form factor. The first-generation iPod offered 5GB of memory and carried the tagline “1,000 songs in your pocket,” in contrast to the 4MB MobilePlayer released by Audible (now owned by Amazon) a few years earlier.

Apple wanted to give the iPod a premium metal rear housing and a screwless design. So it spot-welded tabs to the metal chassis, which enabled a snap-fit assembly with the front face. Manufacturing had to be clean and precise to ensure that the spot-welded, polished metal surface would fit smoothly.

Because the iPod engineering team had only eight months to pull the design together, the early prototypes left lots of room for optimization. Our CT scan shows just how much empty space is left inside its enclosure. Steve Jobs famously dunked one in an aquarium, pointing to the air bubbles rising from the device to show that it could get smaller.

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Intro image for the scan.

iPod Classic (6th Gen)

September 5, 2007

To paraphrase Tony, this was the end of the line for the original iPod. With the launch of the 6th generation device, Apple also began calling it the iPod Classic, anticipating its cannibalization by the iPod Nano and iPod Shuffle–and, of course, the iPhone, which was introduced eight months earlier. This was the pinnacle of the form factor. Let's see the refinements that the iPod team was able to implement over six years.

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A defining feature of the iPod since 2003 was the 30-pin connector, which was designed to make it easy to dock the iPod in an external speaker. It offered a thinner form factor than the original FireWire jack, and it unlocked a massive ecosystem of accessories.

HDDs are very sensitive; their read-arms must move with nanometer-level control, and they don’t tolerate bumps. The final iPod Classic still sported an HDD, albeit with improvements in size and integration. The original device required shock-absorbing bumpers in the enclosure; in this generation they’re integrated into the drive itself. 

The first-generation iPod’s mechanical spinning wheel was a revolutionary interface, but it caused manufacturing and reliability problems. Apple replaced it In the second-generation iPod with a solid-state, touch-sensitive wheel and separate buttons for playing, pausing, and changing tracks. With the fourth-generation iPod, Apple managed to get the control buttons into the surface of the wheel, creating the complex assembly of touch-sensitive and pressure-sensitive circuitry here.

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Intro image for the scan.

iPod Nano (1st Generation)

September 2005

Let’s step back two years to look at the full expression of Apple’s miniaturization efforts. The iPod Nano was the first flash-memory iPod, and as these CT scans show, it’s notably denser than the first iPod Classic. The move to flash meant smaller storage capacity, but the device became much more robust, emerging as a popular accessory for athletes.

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All of the iPod Nano’s connectors are on the bottom edge of the player–a slightly awkward arrangement, but one which allowed the device to be much thinner, since these space-eating jacks don’t need to fit below the display. Seeing the amount of internal space these connectors occupy, it’s easy to understand why Apple would want to get rid of them. The company replaced the 30-pin connector with the much more compact Lightning connector in 2012, and eliminated the headphone jack entirely on the iPhone 7 in 2017.

Here we can see inside the lithium-ion battery pack, where sheets of electrode material shown in red float in a blue electrolytic bath. To the left is the flash memory chip, and in front of it are empty pads for additional memory, revealing that we scanned the low-storage model.

The miniaturized electronics in the iPod Nano are densely packed. Here our CT scan highlights the solder on multiple ball grid arrays and quad flat packages. Our measurements using Lumafield Voyager suggest that the solder joints run at a 500-micron pitch. As Tony relates in our video, these solder joints were the root of some reliability issues: slipping the iPod Nano into a back pocket would bend the thin enclosure slightly, breaking a handful of solder connections. The iPod team had to develop “the butt test” to validate designs for later models. In the meantime, Apple added glue to help absorb strain.

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