Archive for the ‘chumby’ Category

Where USB Memory Sticks are Born

Tuesday, February 12th, 2013

In January, I had the fortune of being a keynote speaker at LCA2013. One of the tchotchkes I received from the conference organizers was a little USB memory stick.

I thought it was a neat coincidence that I was in a factory that manufactured exactly such memory sticks about a week before the conference. In fact, I managed to score a rare treat: the factory owner gave me a sheet of raw chip-on-flex, prior to bonding and encapsulation, to take home.

The USB sticks start life as bare FLASH memory chips. Prior to mounting on PCBs, the chips are screened for capacity and functionality. Below is a photo of the workstation where this happens:

In the image, you can see stacks of bare-die FLASH chips, awaiting screening with a probe card. I love the analog current meter and the use of rubber bands to hold it all together. The probe card has tiny needles on it that touch down on microscopic (less than 100-micron square) contacts on the chip surfaces. Below is what a probe card looks like.

Below is an image through the microscope on the micro-probing station, showing the needles touching down on the square pads at the edge of the FLASH chip’s surface.

Interestingly, this all happens in an absolutely non-clean-room environment. Workers are pretty much handling chips with tweezers and hand suction vises, and mounting the devices into these jigs by hand.

Once the chips are screened for functionality, they are placed by hand onto a PCB. This is not an unusual practice, pretty much every value-oriented wirebonding facility I’ve visited relies on the manual placement of bare die. The photo below shows a controller IC being placed on a panel of PCBs. The bare die are in the right hand side of the photo, sitting in the beige colored waffle pack.

The lady is using some sort of tool made out of hand-cut bamboo. I still haven’t figured out exactly how they work, but every time I’ve seen this process they are using what looks like a modified chopstick to place the chips on the board. My best guess is that the bamboo sticks have just the right surface energy to adhere to the silicon die, such that silicon will stick to the tip of the bamboo rod. A dot of glue is pre-applied to the bare boards, so when the operator touches the die down onto the glue, the surface tension of the glue pulls the die off of the bamboo stick.

It’s trippy to think that the chips inside my USB stick were handled using modified chopsticks.

The chips are then wirebonded to the board using an automated bonding machine which uses image recognition to find the location of the bond pads (this is part of the reason they can get away with manual die placement).

(view in HD)

The first half of the video above starts out with the operator pulling off and replacing a mis-bonded wire by hand, and re-feeding the wire into the machine. Given that these wires are thinner than a strand of hair, and that the bonding pads are microscopic, this is no mean feat of manual dexterity.

Here’s a scan of the partially-bonded but fully die-mounted PCB that I was given as a memoir from my visit (I had since crushed some of the wire bonds). The panel contains eight USB sticks, each consisting of a FLASH memory chip and a controller IC that handles the bridging between USB and raw FLASH, a non-trivial task that includes managing bad block maps and error-correction, among other things. The controller is probably an 8051-class CPU running at a few dozen MHz.

Once the panels are bonded and tested, they are overmolded with epoxy, and then cut into individual pieces, ready for sale.

Interestingly, the entire assembly prior to encapsulation is flexible. The silicon chips have been thinned down by grinding off their back sides to the point where they can tolerate a small amount of flexing, and the PCB is also so thin, it is flexible.

For those of you interested in this kind of thing, here’s the die marking from the FLASH chip; apparently it is made by Intel:

Here is also a die shot of the controller chip:

And now you know where those tiny USB thumb drives are born.

Thanks to David Cranor for contributing images. Images used with permission.

PS: chopsticks

Updates from the Tour in China

Wednesday, January 9th, 2013

Akiba is providing a running commentary of the MIT Media Lab IAP China immersion experience. If you’re curious about it, check it out. So far he has day 1 and day 2 up.

Above is a photo of Colman Lee, a mechanical designer from AQS, lecturing the students about some of the more subtle aspects of mold and tool design. AQS is my go-to manufacturing services partner / general problem solving crew, and they helped with many of the local arrangements for the trip. Below is a group photo at Colinda, our first stop on the tour where we got to take a look inside the Onyx Geiger counter injection molding tool.

One man’s trash…

Saturday, November 10th, 2012

I was wandering around the Hua Qian Bei district yesterday with xobs trying to buy a couple of power supplies for bringup of an open-source quad-core ARM laptop we’re building, and lo and behold, I came across this:

It’s the first time I’ve ever come across one of my former products in the Shenzhen markets. It’s kind of neat because I have intimate knowledge of how it might have ended up at this reseller’s stall. It also brought back old memories of agonizing over the logo color and placement — I think we tested over a half-dozen shades of gray before we settled on this one, and we had to fight with the printer to get the eyes just right and no smearing despite printing on a curved surface (accessories are in many ways harder than the product itself). Amusingly, this lady is selling the power supply for less than it cost us to originally buy it (you can just see the top of her head in the photo, she ducked behind the counter to find the power supplies we were buying, and I snapped the photo while she wasn’t looking).

Most of the excess inventory for this power supply ended up in the US office to handle exchanges & returns, so I’m pretty sure these are from a batch of power supplies that we had rejected. If I recall correctly, I had discovered an issue where one of the inductors in the power supply was missing the glob of glue required to hold it in place. Shipping the unit subjected the power supply to vibration, which caused the inductor to rub against a neighboring part. The rubbing could wear off the enamel on the inductor, which ultimately leads to the inductor shorting against the neighboring part. The power supply’s internal fuse correctly blows when this happens, so it wasn’t a safety issue; but the defectivity rate was around a few percent after shipping. I think a few thousand power supplies were sent back to the manufacturer over that issue. My guess is that after many years, the manufacturer finally found a sucker^H^H^H^H^H^H reseller who would peddle it in the markets.

Inspires confidence in the other ‘brand-name’ power supplies she was peddling, doesn’t it? On the other hand, I did buy a Lenovo-branded power supply that was perfect for my needs. ‘Brand new’ with plastic over the logos, it set me back only $4 a piece, and I did verify on the spot using a multimeter that the power supply did output the correct voltage. Probably good enough for development use, and at that price you just buy two in case one breaks.

Where Arduinos are Born: Touring a PCB Factory

Tuesday, August 14th, 2012

I recently had the pleasure and privilege of touring the factories that make Arduinos.

Arduinos are made in Scarmagno, Italy, a small town near the Olivetti factories on the outskirts of Torino. All of the circuit board fabrication, board stuffing and distribution is handled out of that small town. I was really excited to see the factories, and I’d like to share some photos of them with you.

The highlight of my tour was “System Electronica”, the PCB factory which makes the Arduino PCBs.

One charming aspect of System Electronica is the owner has the factory painted to match the colors of the Italian flag. In this wide view of the factory floor, you can see some of that in the red and white posts down the length of the facility.

Arduinos start as huge sheets of virgin copper-on-FR4.

The sheets above are 1.6mm thick (the most common thickness for a PCB, which corresponds to 1/16th of an inch), and probably a meter on one side by about a meter and a half.

The first step in processing is to drill the holes: hole drilling is done even before patterning. This is because once the holes are drilled, you can use the holes to align the masks used to pattern the traces later on in the process. Hole drilling is also a dirty and messy process, which can damage circuit patterns.

Above is the CNC drilling head used to drill the boards. The blank copper sheets are actually stacked three-high so a single pass of the drill can produce three substrates.

Above is the drill rack used by the CNC drilling machine. If you’ve ever had to muck around with creating NC-drill files, you’ll probably have seen the term “drill rack” used somewhere. This is what it looks like.

Above is the drill in action. It’s encoded in Ogg Theora; so, sorry if you’re using IE or Safari and you don’t have the codec installed. An HD version of the video is also available here. Flash is dead; long live HTML5! [note: I turned off video pre-loading to save bandwidth by just editing the attribute tags. That would have been a pain in Flash. Yet another benefit of HTML5!]

Every hole in the board is mechanically drilled, which is why via count is such an important parameter in calculating the cost of a PCB. This particular drill is a relatively small one. I’ve seen massive drill decks in China that slave four or six drill heads together in a truck-sized machine, processing dozens of panels at the same time; they drill so fast and hard that the ground shakes, even from several meters away, with every via drilled.

Above is a stack of finished, drilled boards that have been cleaned and deburred, ready for the next step in the process.

The next step is to apply a photoresist to the board and expose a pattern. At System Electronica, this is done using a light box and a high-contrast film. Other technologies I’ve seen include direct laser imaging, where the pattern is put on using a raster-scanning laser. Direct laser scanners are more common in quick-turn prototype houses, and film imaging is more common in mass production houses.

Above is a PCB blank being mounted into a light box for exposure. Note that most photos in this post can be clicked to reveal a much higher resolution version.

Above is what the board looks like before and after exposure.

The boards are then sent into a machine to be developed. In this case, the same machine is capable of developing both the photoresist and the soldermask.

Above is an image of a developed board. It’s one of my favorite photos out of the factory. Also, there is just something cool sounding about “Codice: Leonardo”.

After photo-processing and development, the boards go through a series of chemical baths that etch and plate the copper.

The movement of the boards through the chemical baths is fully automated; this is necessary because between certain steps oxygen can spoil a board in a matter of seconds, so the transfer between the baths needs to be fast. Also, the baths contain caustic and harmful chemicals to humans, so it’s much safer for a robot to do this work.

[HD verison] As you can see, the boards swish gently back and forth in the baths as they are processed. Each bath has a different solution in it.

Once the boards are processed in this series of solutions, a dull, white plating (which I’m guessing is nickel) has developed on all the non-resist covered surfaces of the board, including the previously unplated vias and pads.

At this point the resist and unplated copper is stripped off, leaving just the raw FR-4 and the plated copper.

A final step of processing results in a bright copper finish. Note that the photo above isn’t of an Arduino board, as their boards weren’t going through the machine at the time when I was taking photos of it.

The boards are now ready to have soldermask and silkscreen applied. These are applied using a very similar process to the trace patterns, using a photomask and developer/stripper machine.

Above is photo showing a board with both soldermask and “silkscreen” developed. The silkscreen in this case is actually a second layer of soldermask. A very specific formulation of dry-film white soldermask was procured for team Arduino to create a sharp and good-looking layer that can resolve the intricate artwork found on Arduino boards. Other techniques I’ve seen for producing silkscreen layers include high resolution inkjet printing, which is better suited for quick-turn board houses, and of course the namesake squeegee-and-paint silkscreen process.

Once the boards have finished chemical processing, they receive a protective plating of solder through a hot-air solder leveling machine, and then move on to testing.

[HD version] Every board is 100% tested. This means that every trace has its continuity and resistance measured using a pair of flying probes. That’s a lot of probing, and the video above gives you an idea of how fast the probing is done. An alternative to flying head testing is to use clamshell testers, where a set of pogo pins are put into a fixture that can test the entire board with a single mechanical operation. However, clamshell fixtures are very labor-intensive to assemble and maintain, and require physical rewiring every time the gerbers are updated. So, in many cases flying probe testing can be cost-favorable and more flexible when compared to fixtured testing.

Above is a stack of near-finished PCB panels, ready for a final step of routing.

Before the boards can be shipped, the individual PCBs panels need to be routed so they can fit inside SMT machines. The boards are once again stacked up and batch-processed through a machine that uses a router bit to cut and release the board panels.

Finally, the boards are ready to ship on to the SMT facility. As you can see, the boards are panelized in a 2×6 format to make SMT processing more efficient.

Here’s a veritable stack of about 25,000 bare Arduino PCBs ready to leave the PCB factory, moving on to be stuffed, shipped and sold to Makers the world around!

Many thanks to the Officine Arduino team and Davide Gomba in particular for taking time out of their busy schedules, showing me around, and patiently waiting as I expressed my inner shutterbug and general love for all things hardware…

Interview with MAKE: The End of chumby, New Adventures

Tuesday, May 1st, 2012

Last week, the Internet discovered the end of chumby as you have known it. My exit from the company five months ago was deliberately discreet. It was a good run, but it was also time for me to move on. Upon hearing the news, my good friend Phil Torrone reached out to do an interview, and I was happy to oblige. The interview encapsulates some of my experiences that may be applicable to others excited to get into the hardware business. Here’s some of the questions that I answer for Phil:

  • Can you talk about making a device from start to finish, from idea to factory to retail shelves?
  • What were the challenges with retail sales?
  • Did you get any patents? How do they work within the world of open-source?
  • Do you have any advice for a maker who is considering taking VC funding? Anything different if they’re doing open-source hardware?
  • What are your thoughts on Kickstarter for funding?
  • When you advise companies what do you most often suggest to the founders?
  • If you could do it over, how would you change the hardware of the Chumby? The software? The way Chumby was made?
  • Now that you’ve been part of a full cycle of a VC funded company that makes hardware, what suggestions do you have for company structure, from the people to the location, to the overall organization?
  • What’s next for bunnie, what are most excited about to do next?

    If you’re interested, have a read at the jump!