From boom box to iPod

As I sat enjoying a cup of coffee in a small park between Water Tower Place and the American Dental Association headquarters in Chicago one summer day in 1990, up the cobblestone-style park sidewalk came a 55ish gentleman wearing blue running shorts, a yellow tank top and a headband to keep the sweat from beading down his bald head.

And sweating he was because this courageous character came careening through the park on a pair of inline skates, holding a boom box on his right shoulder that was blaring some loud, pounding hip-hop music, which, if memory serves, was MC Hammer’s “U Can’t Touch This.” This guy proceeded to skate-dance—zigging and zagging, spinning in circles—to the beat of the music for a full minute or so before, just as quickly, skating away.

That impromptu park performance is a far cry from the ads showing young, hip-looking people dancing in silhouette while listening to music on their Apple iPods. There is no doubt portable music players have come a long way—even farther than boom boxes if you want to include battery-powered transistor radios in the discussion.

A 1980s style boom box often carried around like a lunchbox or on the shoulder.

Pocket-size transistor radio circa 1960.

Among the later models of the Sony Walkman stereo cassette player.

The sixth generation of the iPod nano is flanked by the fourth generation of the shuffle (right) and the latest touch. Image courtesy Apple Inc.

When Chipworks cracked open the latest iPod nano, the company found a 2mm x 2mm 3-axis accelerometer from STMicrolectronics inside (seen in the center of the image at left). Image courtesy Chipworks.

Interestingly, the rise of transistor radios as the social media revolution of the ’50s and ’60s has a lot in common with the current proliferation of MP3 players. The invention of the transistor in November 1947 at Bell Laboratories in Murray Hill, N.J., set in motion a new technology that would enable manufacturers to do away with tube-based radios. Early progress was slow due to a difficult-to-control manufacturing process that resulted in few properly functioning transistors. Not until R&D efforts turned to silicon-based transistors did real progress begin. By the end of 1954, the first transistor radio hit the market. Then the march was on to miniaturize, while simultaneously improving the manufacturing process. By the ’60s, we had pocket-sized transistor radios, and Sony was already pushing the one-person, one-radio concept.

In the late ’70s, silicon scientists gave us boom boxes—portable music in stereo. Even as their popularity took off in the late ’70s and early ’80s, however, Sony took portable music players to a whole new level in 1979 when it launched the stereo cassette Walkman. Now the music wasn’t just portable, it was personal, thanks to the use of stereo headphones. The Walkman and other players took over the portable music player market and pretty much owned it until the introduction of compact disc players.

Despite the CD era, though, cassette players remained popular. In fact, Sony only this year announced it would no longer make the cassette Walkman in Japan, a begrudging nod to the dominance of digital music players.

And that brings us back to the proliferation of digital MP3 players—iPods in particular—and how MEMS technology continues to drive the miniaturization of these devices, while allowing for more functionality.

Like the early transistors, figuring how to reliably ramp up production of MEMS devices such as accelerometers is something the industry is only now beginning to resolve. And, like transistor technology, MEMS production is a work in progress.

The sixth generation of Apple’s iPod nano, for instance, features an even smaller accelerometer, according to Chipworks Inc., a technology and design analysis firm in Ottawa, Ontario. The Canadian firm performs teardowns of new products as part of the reverse-engineering and patent-infringement services it offers customers.

When Chipworks cracked open the new iPod nano, it found the first 3-axis accelerometer in a 2mm × 2mm package used in a commercial product, reported Dr. St. John (Sinjin) Dixon-Warren, the company’s manager of process engineering. The accelerometer is the A2L from STMicroelectronics, Geneva, Switzerland.

The Chipworks analysis found that the A2L contained stacked MEMS and an application-specific integrated circuit die. “Remarkably,” Dixon-Warren noted in his analysis of the sensor, “ST was able to keep the sensor area almost unchanged—at 0.75mm2—from that seen in the LIS331DL,” which is ST’s 3mm × 3mm predecessor to the A2L.

“The main strategy for achieving this was the use of a hermetic gold seal for the MEMS cap instead of the conventional frit glass seal,” Dixon-Warren said. “We would suspect [that] the specifications for the A2L to be at least as good as those for the larger LIS331DL since the sensor area is similar.”

Based on the constant march toward miniaturization and a few rumblings from within the industry, Chipworks expects to see a 1mm × 1mm 3-axis accelerometer within the next 2 years.

What does this mean for MP3 players? Well, they could make room for more functionality, say, for instance, a MEMS-based pico projector. Then your iPod nano or touch could project your favorite music videos.

But these shrinking MEMS sensors don’t necessarily mean smaller devices. The iPod shuffle is proof enough of this. In case you missed it, the iPod shuffle went from having a round dial control on its first and second generations to no control for its third generation, and then back to a round dial control on its current iteration because the iPod shuffle is easier to use that way.

Then again, you never know. Some current MP3 players are small enough to stick in your ear—literally. So, in another 5 years we all might be dancing to the tunes from an Apple iCloud. No controls, no device even—just sheer, unfettered dancing in public.

As for finding the courage to do that sort of thing, ask the gentleman skating around with his boom box. µ

About the author: Dennis Spaeth is electronic media editor for MICROmanufacturing and Cutting Tool Engineering. Phone: (847) 714-0176. E-mail: dspaeth@jwr.com.