
Hand solderable 1GHz ARM Cortex A8 in TQFP package - nabilt
http://olimex.wordpress.com/2012/04/24/cortex-a8-in-tqfp-sure-allwinner-a13/
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Gussy
As someone pointed out in the comments these processors require DDR3 memory,
which is only available (currently) in BGA packages. This means you can't
quite use a soldering iron to build your own small computer, yet.

The real advantage here is not the savings in the soldering soldering but the
savings in PCB complexity and cost. A small BGA with a few hundred pins will
need at least 6 or more layers to be able to "break-out" all the pins from
underneath the chip. With the TQFP package, all the pins are already at the
edge of the chip, so it's possible to use a 4 layer PCB.

It's an exciting time when more people can have access build thing using this
level of hardware. Now the next thing we need is decent documentation to go
with these chips.

~~~
mbell
Honestly the price differential is very small between 4 and 6 layers now-a-
days. In mass pro that is, they will still charge a solid premium for 6 layer
at many quick turn / small batch PCB manufacturers.

The biggest savings comes from avoiding blind and buried vias which are still
expensive to use but often required for dense BGAs. You can also usually get
away with a larger minimum feature size (trace width) with a QFP which can
also be a nice cost savings in the PCB construction.

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robomartin
Soldering BGA packages "by hand" isn't really that hard. I've done lots of
that. I placed it in quotes because, well, it really isn't done by hand ball-
by-ball of course. All you need is suitable magnifier or inspection
microscope, a stencil, solder paste, a temperature probe and a hot plate or
toaster over.

    
    
      - Apply the paste to the PCB using the stencil
      - Carefully place all the components using the magnifier 
        and appropriate tweezers or vacuum pickup pencils
      - Place in the oven or hot plate
      - Carefully ramp up and down the temperature as required
    

I've built many high-speed (200MHz to 1.6GHz logic) prototype boards this way.
Not the most fun and time-consuming but definitely do-able.

~~~
__alexs
"It's not hard, you just need hundreds of dollars in equipment and some
practice!" Sounds like "hard" to me.

TQFP can be done with common and cheap items like a cheap soldering iron, a
flux pen, some copper wick and a pair of tweezers.

~~~
Symmetry
Yup, flux is great, under appreciated stuff. First you apply the flux to the
area you'll be soldering, then you put just enough solder onto your iron and
drag it along the pins. The evaporating flux will pull the solder onto the
pads. The hard part is in judging the right amount of solder to use.

~~~
robomartin
There's another technique I've used in the past for fine pitch TQFP's. I call
it "impact soldering".

It goes something like this:

    
    
      - Mask everything around the component to be soldered with masking tape
      - Flux as usual
      - Place component down and align it
      - Tack on the corners in order to ensure alignment
      - Don't worry about solder bridging
      - Now, apply solder to the pins
      - Use a healthy dose
      - You actually want an entire row to be brideged
      - You should see a solid strip of solder across all pins
      - Get all four sides done the same way
      - Now, take the iron and heat up one of the beads of solder to the melting point
      - Without any delay, hit the board edge-wise on the table
      - The molten solder will come flying out
      - A small amount of solder (just enough) will remain on the pins
      - With practice you can get perfect factory-looking joints with no bridging whatsoever
    

It takes a little practice, but I have found that if you need to do a lot of
TQFP's this technique, once mastered, works far better than trying to apply
solder precisely. It's messy at first and you might even ruin some parts. Once
the technique is perfected it works amazingly well and it is very fast.

Obviously, if you have a lot of parts on a single board you are entering
territory where reflow soldering in an oven is a far better idea.

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aortega
You can solder this by hand with a solder gun and solder paste, hardly
specialised equipment. Thanks to the chinese guys that did this you can now
hand-solder a computer that runs a modern OS like Ubuntu 12, you couldn't do
that since the 70s.

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sp332
Wait, so A10 is a Cortex A8 plus other hardware? And the A13 is a stripped-
down A10? Who names these things?

~~~
__alexs
And the (Apple) A5 is an A9. I think we need a chart :(

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obtino
I don't know what kind of person would try to solder this by hand! It's a
surface mount package. I wouldn't go near one without specialised equipment!

~~~
Palomides
way easier and quite cheap: just use a hotplate and solder paste ($30
hotplate, $5 solder paste)

~~~
officialchicken
Yes! And toaster ovens work well. Get some high-temp red spray paint too, so
that the hotplate/toaster oven is clearly marked and never ends up in a
kitchen.

