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