LCD evaluation and other preparations for FC handset

[Mychaela Falconia]

Hi Arsenijs!

> A common practice is also putting the connector on the other side of
> the PCB, then making a slot which the cable is supposed to go through.
> This way, you don't have to worry about LCD and the connector
> occupying the same space.

Startek folks (one of the two LCD vendors I am working with) suggested
the same idea to me.  I suppose this idea might work if there is a
great scarcity of electronics on the board: if the entire logic of the
phone is in one chip (no wide external memory buses, no chipset
internal interconnections) and the LCD is used in the SPI interface
mode, connected to the all-in-one chip with just a few wires, then
there would be plenty of room on the back side of the board, and the
slot can probably be made in the middle of the PCB without totally
crippling the signal routing ability.  I suppose this idea could work
for those 100% closed and proprietary "modern" dumbphones based on MTK
or Spreadtrum chips.

But this idea will NOT work for our FreeCalypso handset.  Our PCB will
have 8 layers with lots of traces on every layer (intricate 2+4+2 HDI
structure with inner buried vias and two levels of staggered microvias
on each side), and the width of the PCB will extend only slightly past
the width of the LCD module.  If we had to cut a slot the width of the
LCD's FPC tail in the middle of our PCB, it would cut through all of
our layers and present an obstacle for signal routing, completely
crippling our PCB layout.  In short, just no - totally not suitable
for a PCB of our complexity.

I already know what I want, and I will not settle for anything less: I
want an LCD whose FPC tail is meant to be soldered rather than
connectorized.  Both Startek and HaoRan said they can make such, but
with an MOQ of 1000 pcs, which would be about $3200 at HaoRan's prices
or about $5600 at Startek's prices.  It is more than I can afford
right now, so for the first prototype I will have to use a dirty hack
(lift the existing connectorized LCD above the PCB with double-sticky
tape to make room for the connector), but at a much later stage of the
project (after the first prototype has been built and the software has
been brought into shape) I will probably have to just bite the bullet
and pay the 1000 pcs price to get the LCDs I really want.

For the first prototype I am thinking of my particular hack with the
double-sticky tape to lift the LCD as opposed to some other dirty hack
in order to make our PCB design as close as possible to what I
ultimately desire with a solder-down LCD: this way when we do get the
good LCDs, the layout change will be absolutely minimal.

But meanwhile I need to build some kind of test rig for HaoRan's LCD
(it's a one-off hack, so it doesn't matter how hacky or dirty or ugly
it is) so I can visually compare the picture quality between HaoRan
and Startek LCDs.  I seek an LCD of the very highest picture quality,
hence the decision between HaoRan and Startek will need to be based on
whichever LCD produces the best picture quality.  I already know from
having tested it that Startek's LCD is very good, but I have yet to
see HaoRan's.  Thus I need a test rig for HaoRan's LCD so I can do the
comparison.

I expect to be picking up these HaoRan LCDs from the mailbox service
later today, and then I will need to start the dialogue with Hirose
(the FPC connector manufacturer) about the straight vs. tapered FPC
end strangeness.  If Hirose folks say that a straight FPC end cannot
be reliably inserted into an FH33 series connector and that it is some
kind of inexplicable accident that Foxconn somehow got it to work in
the Pirelli DP-L10, then I'll just use the taller FH12 series connector
for the HaoRan LCD evaluation board - but if there is some way to use
FH33, I would like to use that as it would be very helpful for the
handset prototype: it's bad enough already that we'll have to use
double-sticky tape to lift the LCD, and having to use an even taller
connector than the one in the Pirelli phone would be even worse.

M~