Making The $35 Raspberry Pi Mini Computer: Quickly And Carefully Does It
What's the secret to making a $35 mini computer? The basic recipe is having some extremely skilful cooks who can craft batch after batch of Raspberry Pis as quickly and with as few duds as possible. Sony's U.K. factory makes an average of 4,000 Model B Raspberry Pi's every day -- or one every 7.5 seconds -- and it needs to to keep up with demand for Pi which continues to sell like hot cakes.
raspberry pi

It’s a safe bet that a fair few children of geeky moms and dads will be finding a rectangular-shaped parcel under their holiday tree tomorrow. And when they rip off the shiny wrapping those lucky kids will find an oh-so-tasty Raspberry Pi inside: a $35 mini computer that can play Blueray-quality video and has more graphical power than a Nintendo Wii — although none of that will be immediately obvious. The Pi is a learning tool not a plug-and-play toy.

The first thing the kids are likely to notice after they winkle their Pi out of its antistatic packet is that it looks a bit weird. If they’ve grown up surrounded by slick, shiny consumer gadgets like iPhones and iPads they may never have handled an uncovered circuit board before. Reclaiming electronics from the sealed box approach is all part of the Raspberry Pi Foundation’s plan to get kids learning to code – curiosity being an essential component of learning and creativity.

So in the spirit of stripping away a few more layers, I’ve been asking the Foundation what the secret is to making a $35 mini computer. The basic receipt is this: having extremely skilful cooks who can craft batch after batch of Raspberry Pis as quickly as possible, and with as few duds as possible.

Many Raspberry Pis are made in the UK, in Sony’s Pencoed factory in Wales which landed a multi-million pound contract to manufacture Pis for one of the Foundation’s Pi licensees, Premier Farnell, back in the fall. Premier Farnell also has two locations in China which produce Pi but the majority of its production (70 percent) is in Pencoed, and in January the factory will account for its entire Pi output. (The Foundation can’t disclose exactly how much of the Pi pie each of its licensees accounts for.)

Sony’s Pencoed factory makes an average of 4,000 Model B Pi‘s every day — or one every 7.5 seconds. Which is hard to imagine when you consider the intricacies involved in churning out thousands of double sided PCBs (printed component boards) with surface mount components on both sides and plated through hole components on the top — with blobs of molten solder being laid down in just the right spots, and the correct components stamped on them at a rate of 5.5 parts per second. And doing it all on a very tight budget.

Boards are made in panels of six Pis which go through four “key processes”: mounting the bottom surface components, mounting the top surface components, mounting the plated through hole components; and then testing and packing.

Pi on a budget

Of course, making a Pi is nowhere near as complex as making a modern smartphone, but the balancing act here is keeping the price down without eroding the distributor’s business model. The most costly components in the Pi are the Processor and Memory core silicon, closely followed by the connectors.

With a $35 price tag (and just $25 for the forthcoming Model A Pi) components have to be bought at the right price but also the right quality — since manufacturing defects also have to be minimised and squeezed out of the production process till they’re barely ever there. It’s no good slowing production either: demand for Pi is so high they have to be able to make thousands per day.

“To achieve the low price whilst still yielding a sustainable business model requires skillful manufacturing optimisation and parts procurement,” says Pi hardware designer and Foundation trustee Pete Lomas (no relation!). “The production line has to run efficiently and deliver a very low failure rate. Component vendors must be selected for both quality and price and any potential changes passed through a detailed selection procedure. It is little use saving 40 cents on the components if the failure rate of finished Raspberry Pi rises. Equally every defect is aggressively pursued to understand it’s root cause and eliminate it.”

“Test failures” do still exist of course, but Lomas says that “to our knowledge” fewer than 100 boards have been returned by users as defective — meaning less than 0.1 percent of boards have slipped through the quality-control net. “Of these, some had physical (transit) damage and others had no fault found, so the actual figure is somewhat lower again,” he adds.

Selling like hot cakes

In terms of keeping up with demand, Lomas admits the Foundation was initially caught on the hop — having drastically underestimated people’s appetite for Pi — which resulted in shipping delays in the early months. “We were caught out by a massive increase in interest in the Pi in the very early days,” he says. “Whilst we were setting up for a modest production run of 20,000 units the expressions of interest overtook us by a factor of 10. At that point we decided to engage with our partners Premier Farnell and RS.

“Even with their significant resources, the logistics of getting components for a hundred thousands of Pis and getting them built was a challenge.”

Unlike an electronics giant like Apple or Samsung, the not-for-profit Raspberry Pi Foundation and its suppliers were not in a position to stockpile components prior to launch to scale up for the unexpected surge in demand. (And let’s face it, even Apple can’t always keep up with demand.) Another delaying factor is long lead-times on some of the Pi components, says Lomas.

“[Our partners] didn’t have the opportunity to stockpile before launch (unlike, say, Apple), so things were always going to be tricky. Scalability also depends on the components and the lead-time on some parts, especially the processors, is significant and still can present issues a year in to manufacture.”

The Foundation is expecting to sell about a million Pis in its first year of operation — a far cry from the original 20,000 production run it budgeted for.

Baked in the U.K.

The Raspberry Pi was born in the U.K., so it’s only natural the Foundation wanted Pi to be made in the UK too. Sony’s Pencoed factory was chosen because it ticked a variety of boxes, says Lomas — not least, being open to visits from children to see Pi making in progress.

“Making Raspberry Pi in the UK is a desire that we had on day one. The Foundation’s aim is to encourage children to develop an interest in programming, electronics and related engineering subjects. Having the manufacturing of Pi in a place that we could provide opportunities for ‘show and tell’ was also important and the overall philosophy of the Sony management and staff has been a significant enabler for this,” he tells TechCrunch.

“Sony Pencoed was chosen because both their world-class technical capability and their enthusiasm for the Raspberry Pi project overall. We also should not forget that they offered our licensees a viable cost model on a par with the ‘all in cost’ of Far East manufacture. Equally from a technical point of view, the management and resolution of any design related production issues or optimisations is much easier when they are only a few hours away.”

The factory now has more than 22 staff dedicated to Pi production. The overall lead time from first contact with the factory to hitting “volume production” was around 14 weeks — giving an indication of how long it took Sony to devise the Pi production line. Now there’s a “rolling production forecast” between Premier Farnell and Sony which allows for “a degree of production flexibility” with around a month’s notice, says Lomas.

“The only process that Sony did not already have in their production process was Package on Package. Within the introduction programme they researched the process in depth, selected and installed the equipment and ran trials to validate the process before introducing it to the Pi line,” he adds. 

Another helping of Pi

Asked whether Sony’s factory could scale up to greater production capacity in the future, Lomas says there is “significant extra capacity” that could be brought on stream. “Ultimately it is the licensee’s decision where to place additional capacity, but overall the Sony experience has been excellent,” he adds.

There has been no let up in demand for Pi, according to Lomas, but the Foundation believes its existing Pi factories have enough capacity to keep up with demand. “We hope that in the next few months we will reach equilibrium where manufacturing is balanced (as much as it ever can be) with demand. We have options to increase capacity with our existing manufacturers and so additional factories would in all probability not be required.”

For more on Pi production, Lomas has written an excellent, blow by blow account of the various stages and processes of Sony’s Pencoed Pi production line — such as the reels of surface mount components used to keep production ticking along, how Pi boards are baked (yes really) in giant ovens to make sure all the components are properly adhered, and the perils of “lava accidents.”

The Foundation has also put together a video montage showing some of the Pi production stages:


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