Repair of my Onyx Boox M92 e-ink display

I apologise, but I just have to brag a bit (a lot actually).

My old faithful Onyx Boox M92 9.7″ e-ink reader stopped working a month ago. I was quite upset, because I used it frequently to read data sheets and engineering books at night. It would start up and display faint grey pixels that gradually got darker over a period of a minute. When I navigated the application icons a ghostly rectangle would move where the application icons are supposed to be. This led me to believe that the processor was OK, but the display was not.

I examined the flat flexible cable of the e-ink display using a high-end Olympus SZ51 microscope and could not find any hair-width cracks in the tracks, until I lifted up the Kaptan tape and saw the tight Z-bend:

e-ink-display-z-bend-in-flexible-flat-cable

The person assembling the unit pressed down so hard on the Z-bend on the right-hand side that the ribbon cracked at the fold. It worked for years (the tracks just touching) until one day it yielded. I could barely see the faint crack lines of the tracks on the outside of the fold at 40 x magnification, but unfolding it finally revealed the problem.

I carefully scraped away the insulation, tinned the tracks and attached wires (0.2mm in diameter) using my Metcal MX-5000 rework station. The tracks were as thin and brittle as gold leaf and would be prone to flaking away during the scraping. This was the final result:

e-ink-display-flexible-fat-cable-repaired

When the unit magically worked again… wow what a feeling!! In total that was 4 hours well spent 🙂

Lessons:

  1. Don’t skimp… buy quality tools (within limits)
  2. Patience (a steady hand)
  3. Perseverance (in truth pigheadedness)
  4. If I did not blow my budget on quality tools, I could afford a new 13.3″ Onyx Boox MAX… ha ha!

Happy holidays!

UPDATE! 2018-09-14

Well my repairs lasted nearly two years, but the honeymoon’s over. It stopped working again and I tried to repair more broken tracks. I used double-sided tape to keep the FPC cable down… bad mistake! Second time I tried separating the cable from the tape, it tore the tracks right off the cable 🙁

I think the apt term is BER (Beyond Economic Repair).

 

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