Issue 544: Enlarge the UPPER PCB?

Reported by Nikolaus Schaller, Jan 6, 2014

(extracted from Issue #518 because it is a new topic)

should we change shape of UPPEr PCB to be flush with 
*outside* of case? It seems feasible to simply have a nice finisch 
on the PCB edge and make that (part of) our "spacer 
frame". The "hight" above LOWER seems to fit to the 
micron. Would also better support the kbd area to avoid bending of 
PCB (and thus not causing mech pressure/force to high comonents on 
LOWER: modem) when pushing a kbd switch/key. Otherwise we might need 

mech support posts soldered to UPPER and protruding through holes in 

LOWER to the battery bay steel, since modem and other large BGA 
components MUST NOT get mech force bending/pushing them down.

just a further maybe not so spleeny idea: when UPPER creates part of 

our spacer frame outer surface, we should of course have it plated 
by gold. And when we already have gold there, why not make this a 
few cotact pads for e.g. charger-cradle pogopins to contact there. 
The CRTouch chip's 4 capacitive sensor "buttons" are 
another thing that comes to mind. I suggest to have equaly spaced 
and sized separate gold-pated contacts of maybe 5mm length all 
around the perimeter/edge of UPPER, and use some of them for 
predefined assigned functions like charging, leaving the others for 
our hw-hacker customers by routing them to solderpads nearby and 
maybe even some of them via B2B to LOWER and there to expansion 
connectors.

now it takes me away I guess: how about separating above mentioned 
5mm gold pads by LEDs embedded flush into PCB edge? LEDs with 0.8mm 
height and some 1.2mm length would nicely separate the 0.8mm high 
gold pads by 1.3..1.4mm

>>The "hight" above LOWER seems to fit to the 
micron.

Actually not correct. It's even better, we seem to have enough 
distance between LOWER and UPPER to glue a rubber seal with one side 
coated with stickyfilm to the bottom side of UPPER. A 2mm wide, 
maybe 0.2mm thick stripe all around the circumference, to sit 
between UPPER and case plastic

Comment 1 by Nikolaus Schaller, Jan 6, 2014

It seems feasible to simply have a nice finisch 
on the PCB edge and make that (part of) our "spacer 
frame".

Unfortunately no - unless we want to pay a lot of $$$ upside for the 
PCBs.

1. PCBs are milled in the last production step
2. adding gold plates to the edges is not a standard production 
process (except for some rarely used edge connectors)
3. the most problematic step is that for Pick&Place the PCBs are 
still on a single panel. After Pick&Place and reflow soldering, 
they are cut from that. This cutting step isn't as precise as the 
milling and of course comes weeks after PCB production.

So we have a loop in the production process if we want gold plated 
PCB edges. Or even unplated but nicely finished edges. I.e. this 
idea breaks the production process and introduces a lot of 
additional cost I am not sure if we should spend it (especially for 
the 250 units level).

The standard is to hide the PCB (and therefore production 
imprecisions) inside the case.

But for hw-hacking extensions we can add additional connectors to 
the lower side of the UPPER board so that they stick out between the 
LOWER and UPPER board.

Connectors are much more reliable than gold plates which get easily 
scratched off and may get short circuits by some coins or keys in 
the same pocket as the Neo900. So from a reliability and durability 
point of view, a good connector is better - and can even be replaced 
if worn out.

Finally we have to take care about CE (safety) and ESD aspects when 
adding gold contact to the PCB edge.

Comment 2 by Nikolaus Schaller, Dec 14, 2020

Status: WontFix

GTA04b7/Neo900