Ben NanoNote Hardware Quality

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"Any usual figures for component lifetime, number of connector mating cycles, switch switching cycles, button presses, etc. should be designed for at least five times the usual limits of regular consumer electronics."
- Harald Welte about Openmoko GTA04, May 8, 2008 -

On this page we are documenting all aspects of Ben NanoNote hardware quality, what will pass or fail during production, what happens to the products over time, etc. If you have interesting pictures of your Ben NanoNote highlighting quality issues, especially after long periods of time or unusual usage scenarios, please contribute here. It will help us improve the longevity of our devices.

Contents

[edit] Manual

FAIL: Note the little dots especially in 'specifications'.



[edit] Casing

FAIL: Metal sheet bent up, will be replaced and returned to vendor.
FAIL: Bezel will be replaced and returned to vendor.
FAIL: Note how the top cover of the right device (at the bottom on the picture) doesn't form a clean circle (compare to much cleaner circle on left device). Top cover of right device will be replaced and returned to vendor.
FAIL: Bezel will be replaced and returned to vendor.
FAIL: The size of the gap will be measured with a tool [TBD: picture of tool, pass/fail criteria]. If the gap is too big, the plastic component will either be returned to the case vendor, or the gap will be glued together [TBD: exact criteria? take picture of glued case]. The root cause of this problem is a worn out steel tool, so the longer the tool produces plastic parts, the bigger such gaps may become. At some point production will be cut over to a new steel tool and the plastic pieces fit perfectly again. In general we don't like gluing so we need to dig deeper to find out how many devices are affected, how many are glued, and what we can do to improve the situation. Also the position of one screw could be moved upwards on the left side of the screen to reduce this problem in the top left corner of the screen, but that would require a bigger mechanical change.



[edit] Keyboard

FAIL: The divider between function keys and rest of keyboard broke into four pieces, probably due to flexing along the vertical axis during transport.



[edit] Hinge

Loose Hinge.ogv
This is an example of a very worn out hinge, different (older) device but same model and vendor as the hinge used in the Ben NanoNote. We don't know exactly how long this device was used or how it was used, but obviously a hinge this loose is really bad for anybody. We need to watch longevity of the hinge used in the Ben NanoNote, learn more about good and bad hinges, and then see what we can improve. For our current Ben NanoNote production, the hinge test passes if the screen can hold itself in position at 45 degree open (almost closed) and at 135 degree open (wide open). If the test fails, the hinge will be replaced and returned to the vendor.

[edit] Label Under Battery

BOTH PASS: Look at the 'USB Boot' window on the left side, it's still _OK_, but on the right side the label is shifted to the side so that the USB boot pins are only partially accessible. Both units passed our tests but going forward we need to either find a way to position the label more precisely, or remove the label altogether.
PASS: Another problem with the label, the material is either too thick or too thin, and the glue cannot correctly hold it down. Many units have this problem and we are passing them right now because the problem only affects the label under the battery, and is only cosmetic (you can always insert the battery which will push the label down). Going forward we will try to fix the label material or glue, or remove the label altogether.
FAIL: Label too small and shifted to the right. Changed size of label and wrote more precise positioning instructions.
PASS: Same as the one before.



[edit] PC Sheet

PASS: When you look at the active colored pixels, you see a dark gray frame around them on the left and bottom side. Then there is a sharp line and it becomes all black. Where the 'all black' starts is defined by the PC sheet [TBD: picture of PC sheet alone], and the PC sheet and underlying LCD must match perfectly. In this case, the dark gray area on the left and bottom side are roughly equal. All is good.
FAIL: Here however, note that the dark gray zone left of the active pixels is narrower, maybe only half of the dark gray zone at the bottom (below the cursor). What this leads to is that if you look at the NanoNote from the left side, the left-most pixel would be cut off by the PC sheet which is not centered correctly above the LCD for this unit. We improved the production and testing steps such that hopefully all devices will have very good centering of the PC sheet. This device was reworked.



[edit] LCM

FAIL: Caused by an SMT problem with the connector for the LCM cable.
FAIL: The beads we added to pass CE could sometimes cause such color effects. We switched to higher precision beads.
BOTH PASS: The left LCM has a slight red cast. Both devices were photographed in daylight next to each other, but on the picture I don't think you can really see the problem. Bottom line is that right now we are unable to define exact criteria for LCM color correctness, so the IQC (incoming quality control) is a subjective test only. Maybe we can work on a test setup with a camera that can calculate exact values for color correctness? That would make the production process and quality criteria for this step more comprehensible.
PASS: Note the small red and blue artefacts next to pixels. It turns out this is a limitation of how the LCM controller in our Ingenic XBurst Jz4720 CPU talks to the Giantplus LCM. If the CPU would support dot-scan instead of line-scan, it might be possible to prevent these artefacts. This is a design limitation.



[edit] COB

FAIL: Note that some wires in the encircled area are not running along the right path.
FAIL: Since the one on the left already fails, it's clear this one fails as well.



[edit] USB connector

FAIL: One corner inside the USB connector is broken off, which made it impossible to properly insert the USB cable. This unit went to a rework station where it was disassembled and the USB connector replaced within about 5 minutes.

[edit] Battery Connector

FAIL: The left finger is dented in, meaning that the battery will not connect properly or easily disconnect when using the device. The screen will turn white, device turns off, etc. The battery connector of this device was replaced. The particular battery connector used in the Ben NanoNote is from a Chinese manufacturer [TBD: which?] and considered not very high quality in general (see next picture for a better one). Price per connector 1.8-1.9 RMB (26-28 US cents), MOQ 30K, lead time 1 month.
For comparison, this is a higher quality battery connector from a Taiwanese vendor [TBD: which?], maybe for Ya NanoNote? Requires PCB change however. Price per connector 2.9-3.0 RMB (42-44 US cents), MOQ 6K, lead time 6-8 weeks. So it's 16 US cents per device more expensive than our current connector.


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