Whither open hardware ?
werner at openmoko.org
Fri Jan 8 22:34:48 CET 2010
Dave Ball wrote:
> What's the yard stick for measuring against here? I.e. are we talking
> about one-off from digikey/farnell, samples direct from the
> manufacturer, or limited-run (couple of hundreds) quantities?
For the full process from R&D to mass production, you need to have
channels for small, medium, and large quantities. First just a few
to figure out if and how the thing works. Then hundreds for the
prototypes, and finally thousands for mass production.
If a part is available from Digi-Key or a similar distributor, this
helps enormously to accelerate R&D and it can also help when in a
pinch in a prototype run.
> > - what are the integration costs ?
> is this things like placement of awkward (small pitch etc.) parts,
> FPC's etc., or ancillary parts such as partner chips?
Depending on the part, it can be all of this and more. Requirements
on the PCB and the SMT process, partner chips, extra voltages,
mechanical and thermal issues, drivers, and so on.
- if a new component reduces the minimum pitch or has a higher pad
density than the rest, your PCB may get more difficult to make,
possibly resulting in higher cost, a smaller choice of companies
that have the technology, higher lead time, and so on.
- some components have an unusual reflow profile, e.g., batteries
(don't like the heat) or complicated BGAs (have to make sure even
the most inaccessible ball reflows correctly).
- CPUs have long lists of requirements on their power supplies and
their sequencing. E.g., it was quite a puzzle to figure out how
to make the 2442 with with the 50633.
- extra voltages: some chips inexplicably want something slightly
different from 3.3 V. There goes another LDO.
- mechanical: need to find suitable space. Electromechanical
components also need to interface mechanically, which may affect
the shape of other elements.
- thermal: don't cook your neighbours and don't be cooked by them.
Also, some special layout may be needed to get the heat away from
- let's not forget the software. If a chip needs a driver, that one
has to be written, debugged, and so on. This also implies what
one needs sufficiently open documentation, which can require a
great deal of negotiation.
> Is the normal route of sourcing via a factory (even for prototypes
> etc.)? From a few searches it seems that getting hold of some parts
> (i.e. screens / touch layers) is incredibly difficult for one-offs.
For the easily obtainable parts, you have many choices. Small
quantities you get from Digi-Key, even if it's expensive per piece.
Perhaps even medium quantities, if you don't already have a better
channel. Large quantities, you get from the official distributor.
If you're willing to take some (small) chances, you can also use
other channels, e.g., to bring down lead time.
Parts that are hard to get require contacts, muscle, illusions, or
someone who can lend you some of these. You normally negotiate the
whole package, so you don't only get samples but you also at least
talk about the larger quantities you'll need in the future.
For prototypes you want fast turn-around times, so involving a
mass-production factory may not be such a good idea. They can do
sourcing, but their mode of operation may not include quick changes
and such. (E.g., GTA01 was prototyped in Taipei, GTA02 had many
prototype runs at the MP factory, a process that was agonizingly
slow and had a huge overhead, GTA03 was prototyped again in Taipei.)
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