<p>Lasers to make one layer deep micro vias is a standard technique. I have used it in board designs at least ten years ago, though it has gotten much cheaper since then.</p>
<p>--Drew</p>
<div class="gmail_quote">On Oct 6, 2012 1:34 PM, "Tom Metro" <<a href="mailto:tmetro%2Bhhacking@gmail.com">tmetro+hhacking@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Thanks to Stephen Adler for filming and posting his Raspberry Pi<br>
Video/Tutorial:<br>
<a href="http://www.mail-archive.com/hardwarehacking@blu.org/msg00487.html" target="_blank">http://www.mail-archive.com/hardwarehacking@blu.org/msg00487.html</a><br>
<br>
(I haven't viewed it, but will take a look when/if I get a Raspberry Pi.)<br>
<br>
<br>
Here's a fairly introductory Raspberry Pi tutorial that end with how to<br>
use a Raspberry Pi as a NAS:<br>
<a href="http://www.techradar.com/news/computing/pc/raspberry-pi-tutorial-how-to-do-more-1095946" target="_blank">http://www.techradar.com/news/computing/pc/raspberry-pi-tutorial-how-to-do-more-1095946</a><br>
<br>
<br>
adafruit is promoting a colorful new Pi enclosure that is made of a<br>
rainbow assortment of laser cut acrylic that stacks up and is sandwiched<br>
between a top and bottom layer of clear acrylic:<br>
<a href="http://www.adafruit.com/blog/2012/09/20/in-stock-pibow-enclosure-for-raspberry-pi-computers/" target="_blank">http://www.adafruit.com/blog/2012/09/20/in-stock-pibow-enclosure-for-raspberry-pi-computers/</a><br>
<br>
<br>
Why One Person Thinks Raspberry Pi Is Unsuitable For Education<br>
<a href="http://hardware.slashdot.org/story/12/09/25/2056240/why-one-person-thinks-raspberry-pi-is-unsuitable-for-education?utm_source=rss1.0mainlinkanon&utm_medium=feed" target="_blank">http://hardware.slashdot.org/story/12/09/25/2056240/why-one-person-thinks-raspberry-pi-is-unsuitable-for-education?utm_source=rss1.0mainlinkanon&utm_medium=feed</a><br>
<br>
(Quoting Slashdot, which quotes the original article,<br>
<a href="http://whitequark.org/blog/2012/09/25/why-raspberry-pi-is-unsuitable-for-education/" target="_blank">http://whitequark.org/blog/2012/09/25/why-raspberry-pi-is-unsuitable-for-education/</a>)<br>
<br>
"Raspberry Pi was designed for education. As any popular product is<br>
bound to, Raspberry Pi has been criticized a lot for things like lack<br>
of a box, absence of supplied charger or even WiFi. Raspberry Pi has a<br>
much more fundamental flaw, which directly conflicts with its original<br>
goal: it is a black box tightly sealed with patents and protected by<br>
corporations. It isn't even remotely an open platform."<br>
<br>
The "proprietary GPU blob needed to boot" is mentioned, which has<br>
been discussed here before. The article also touches on the ARM being<br>
patented, which I don't have a problem with. But it also says that<br>
documentation on the ARM architecture is not freely available, and that<br>
indeed could be a problem.<br>
<br>
It goes on to list some completely open source CPU cores, as well as<br>
pointing out other proprietary vendors, like Atmel, have freely shared<br>
their documentation without onerous licensing restrictions.<br>
<br>
The author recommends the more open Beagle Board or Samsung ODROID-X as<br>
a Raspberry Pi alternative. He also recommends the fully open hardware<br>
Milkymist One, but it costs $800 and thus isn't a practical alternative.<br>
I guess he wasn't aware of some of the other open hardware boards that<br>
are in the same league as the Pi and still fairly cheap.<br>
<br>
Rhombus Tech (<a href="http://rhombus-tech.net/" target="_blank">http://rhombus-tech.net/</a>), a company creating an open<br>
hardware platform, was mentioned in the Slashdot comments. (Not terribly<br>
unique. I posted about another Raspberry Pi-class device recently<br>
(OLinuXino-Micro) that was open.) The Rhombus Tech products will use a<br>
PCMCIA-like metal-enclosed card design, and their first model will use<br>
an Allwinner A10 CPU.<br>
<br>
The full article is worth a read.<br>
<br>
The Slashdot blurb also references:<br>
<br>
Raspberry Pi's Secret: 'Sell Out a Little to Sell a Lot'<br>
<a href="http://www.wired.com/opinion/2012/09/raspberry-pi-insider-exclusive-sellout-to-sell-out" target="_blank">http://www.wired.com/opinion/2012/09/raspberry-pi-insider-exclusive-sellout-to-sell-out</a><br>
<br>
...if other manufacturers copied the design, our partners would lose<br>
their investment, which was approaching several million dollars.<br>
<br>
How could we enable hacking while preventing cloning? Holding back the<br>
schematics altogether troubled us. Not being open would impede<br>
people's ability to interface and hack the hardware - defeating the<br>
very goals we had set out to accomplish with Raspberry Pi in the first<br>
place.<br>
<br>
So we decided to publish the schematics, but hold back the detailed<br>
Bill of Materials (BOM) and physical PCB design or "Gerbers" for a<br>
limited amount of time. After all, hardware is just one part of our<br>
overall plans. The schematics alone don't provide enough information<br>
to clone the Pi without expending considerable effort re-laying the<br>
PCB and figuring out the exact part used in each location.<br>
<br>
Ummm...if Broadcom is one of the partners, and the product depends on<br>
the Broadcom SoC that in turn requires a proprietary software blob, it<br>
would seem they already had two hard to bypass barriers to cloning:<br>
Broadcom could refuse to sell the SoC, or it could shut down the clones<br>
for copyright violation. Was Broadcom not cooperative?<br>
<br>
Here's an interesting bit on the board fabrication:<br>
<br>
...we had 253 connections to bring out (the BGA escape) in an area<br>
much smaller than the size of a dime. And while there are special<br>
high-density interconnect (HDI) techniques for densely layered PCBs,<br>
those would just reduce yield and increase processing steps not to<br>
mention the costs. ... What if we could steal the idea of "blind micro<br>
vias" from high-density interconnects, but apply it cheaply enough for<br>
the Pi design?<br>
<br>
Instead of going through all the PCB layers, we made human-hair sized<br>
holes (micro vias) that go through only the first couple of layers<br>
(blind) - saving just enough space on the other layers for wiring up<br>
the other PCB components. At high volumes, these holes could be made<br>
quickly and efficiently with a laser. And it only cost a few cents<br>
extra. Making these tradeoffs resulted in a relatively simple<br>
six-layer board that didn't compromise power distribution. And it<br>
enabled manufacturing at scale.<br>
<br>
Seems like another good way to ward off clones, unless this technique is<br>
widely known.<br>
<br>
-Tom<br>
<br>
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</blockquote></div>