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Reason I ask is, I've noticed with water damaged iPhone 6 screens if the pins on the connectors of the screen itself have corroded and you fix them with cleaning and fresh solder or jumper wires 8 out of 10 times the screen will function fine.

However, the 6s screens seem to be SUPER sensitive. Any water damage to the phone even if it has no impact on the connectors of the screen itself or logic board around the connectors then only 1 every 10 will work again. The rest simply don't display an image ever again.

Only difference from the 6 and 6s screens is the 6s has touch ic/circuit part of the screen assembly itself where as the 6 has it on the logic board.

Both get the LCD controls and voltages from the logic boards. The 6s has a line called "LCM_Panic" on the logic board that the 6 does not (unless it was renamed something else that's not easily discernible) however not sure if this line has anything to do with the issue I've been seeing.

I'm trying to figure out why that is but of course there isn't any reference/schematics anywhere on the screens themselves.

Curious if anyone might have any insight and any clues to a work around.

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2 Answers 2

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Sorry, this is a late reply. Hopefully I'm not breaking any conventions but I thought this answer might be helpful for anyone searching for this problem. Be gentle, this is my first answer on StackExchange:>)

The iPhone 6S has a very sensitive backlight circuit. It doesn't take much more than a misaligned connector while the battery is connected to blow the backlight filter (ferrite bead). If a phone was water damaged, all it takes is a tiny amount to short the adjacent contacts on the LCD connector (PP_LCM_BL_ANODE_CONN & GND) to cause the same effect. You might not even see any after effects of the water other than the red LDI.

The Touch IC on the iPhone 6S, now embedded on the screen assembly, replaces the CUMULUS & MESON IC's from the iPhone 6/6P and include the added Force Touch functionality.They wouldn't normally have anything to do with a screen not producing an image.

As for the LCM_Panic line, it appears to be the same thing as the PMU_TO_PHOTON_ALIVE line from the iPhone 6. They both originate from the PMU and are part of the Display Control Signals going to the screen.

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  • \$\begingroup\$ Thanks for your reply. Could you explain why the 6s has two different backlight circuits? One uses a bigger coil than the other. The previous models only used the big coil for backlight. Wondering if it has any affect on LCD damage \$\endgroup\$
    – user140123
    Commented Sep 14, 2017 at 15:03
  • \$\begingroup\$ Only an Apple EE can answer for certain. The new configuration allows much more current draw and the design decision is probably driven by limited vertical real estate. \$\endgroup\$
    – Minho
    Commented Sep 14, 2017 at 15:19
  • \$\begingroup\$ What do you mean exactly about limited vertical real estate? Also do you know if both those circuits are operating at the same time or individually? \$\endgroup\$
    – user140123
    Commented Sep 14, 2017 at 15:21
  • \$\begingroup\$ The component density is very high on the iPhone logic board and the there is very little space for big and tall components. That is why you will see identical bypass caps in parallel instead of one large one. \$\endgroup\$
    – Minho
    Commented Sep 14, 2017 at 16:22
  • \$\begingroup\$ Is there a way to contact you through private message? \$\endgroup\$
    – user140123
    Commented Sep 14, 2017 at 19:31
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Apple is notorious for using "no-clean" flux in their contract manufacturing specs. Thus moisture + corrosive flux residue= rust. Consider it "toast" unless you can remove all the residue under Chips with solvent, vacuum and scrubbing. ( not easy) THey also use chemical moisture dots that turn blue for internal warranty void detection.

Better phones now have copper plating methods include moisture resistance. such as I believe, Immersion gold over immersion nickel over copper and as such considered water proof to 1m depth with better flux cleaning bethods.

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  • \$\begingroup\$ But I'm referring to the actual LCD assembly itself not the logic boards. Are you saying the 6s LCD could be manufactured poorer than the previous model 6? \$\endgroup\$
    – user140123
    Commented Jun 19, 2017 at 17:01
  • \$\begingroup\$ I'm not sure of the construction does it use a carbon contact zebra connector? If so, dielectric contamination is crucial to be removed for high impedance fast slew rate signals. lcm_panic("Incorrect format: value is not a string."); is an indication of data errors. So if it is a high speed serial conection, then impedance at that speed is important, thus stray capacitance and corrosion. \$\endgroup\$
    – D.A.S.
    Commented Jun 19, 2017 at 17:45

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