[Arm-netbook] Fwd: [eoma68 update] report back from factory on HDMI

Luke Kenneth Casson Leighton lkcl at lkcl.net
Wed Jul 3 09:03:44 BST 2019

---------- Forwarded message ---------
From: Luke Kenneth Casson Leighton <lkcl at lkcl.net>
Date: Wed, Jul 3, 2019 at 8:16 AM
Subject: [eoma68 update] report back from factory on HDMI

Mike's staff began the PCB assembly of the run of 100, and had to stop
at 36.  20 were ok: 16 of them, the HDMI connector refused to fit.
The reason: the CNC machining on the edge of the PCB has not been done
accurately enough: it's simply too ragged.  The staff did some
experimentation, cleaning up some of the edges in the cut-out with an
xacto-knife: this did the trick, even though it is shaving something
like 0.01mm off the ragged edge of the PCB.

The left and right edges do not matter too much, however where the
HDMI connector comes in close, it definitely does.  Mike is going to
talk to the PCB factory to see if there is anything that they can do
in future, however with 1,000 PCBs already manufactured, the safest
thing to do is probably to *hand-trim* that PCB edge, removing the
burrs, on all 1,000 PCBs.

Again, to reiterate, because I am still seeing evidence of
"complaints" out there, from people who believe this should be easy:
these are absolutely ridiculously tiny components and tolerances, and
the budget on which it's being done is equally as frugal.  0.05mm on
the edge of a PCB.  0.2 mm wide pins, with 0.2mm clearance between
them.  A "normal" Single-Board Computer product from any other
well-funded Corporation would use large (Type A) HDMI, top-mounted,
with plenty of tolerances and no need for the PCB edge to be
accurately milled.

Again, to reiterate: we do not know what will need to be solved next.
Therefore, a production date simply cannot be provided, and that
really is the end of the matter.  Or, the answer is: the production
date is "the production time plus the unknown time to solve unknown
and unknowable future issues".

Mike is sending me the 20 "good" PCBs so that I can test them here, to
see if they are okay.  The staff will continue with the rest by
shaving the burrs on the PCB on every single one of the remaining 80
with an xacto-knife, before putting them through the production line.
 It is looking like I will need to do the testing of all 100 of this
preliminary production run, here, at my home, in Taiwan.
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