MBP Keyboard Assembly: Backlight illumination with FTIR

Today I have made an interesting discovery: my 2008 2.4 GHz MacBook Pro is using frustrated total internal reflection (FTIR) for the illumination of its keyboard.

The background to this discovery is that I spilled a bit of salad dressing into my keyboard (pro tip: do never try to show someone the salad you are currently eating via skype) and since then some of my keys are not working reliable anymore. To be more precise: Some keys I must push two or three times until they produce the letter. Thus, I wanted to look if I could clean the keyboard and what kind of keyboard I would need if I wanted to replace it. I used the MBP iFixit guide to achieve the disassembly (and as I have been a lucky guy also the reassembly).

Anyway, when I removed the keyboard compartment from the MBP’s body I discovered that it consisted of four parts:

MacBook Pro Keyboard Parts

MacBook Pro Keyboard Parts


It consists of these four parts:

  1. The actual keyboard
  2. Keyboard Scheme Foil
  3. Dotted Transparent Plastic Sheet
  4. White Plastic Foil with a small PCB and four white LEDs

The four parts were held together by eight little bent wires.

The white Plastic Foil contains a PCB with four white LEDs that emit light into a transparent plastic sheet through the sides of four holes in that sheet:

MacBook Pro Keyboard Backlight Sheet and Leds

MacBook Pro Keyboard Backlight Sheet and Leds

As this sheet is transparent, light that is being emitted into it from the sides will be reflected internally endlessly because of the optical effect of total internal reflection. Anyway, if there is something printed on the transparent sheet this will cause the light to emit in that area:

MacBook Pro Keyboard Backlight Sheet

MacBook Pro Keyboard Backlight Sheet

These spots are lying underneath the actual keys of the keyboard. Thus, only the keys are being evenly illuminated. As the light gets weaker in the outer areas of the transparent plastic sheet more points are printed on the transparent plastic sheet in the outer regions than in the inner regions. This technique is terribly simple, very effective and dirt cheap. Brilliant, Apple!

Why do I care for this? Because FTIR is the technique with which Jeff Han brought up the hype for cheap, large multi-touch surfaces. Jeff Han is better known for his performance at the TED.

Update: When I wrote this blog entry, I was just intrigued by the nice technical solution Apple came up with this backlit keyboard. However, there are some people that can creatively apply my bit of superfluous information: Colorized MacBook Pro Keyboard Backlight by Greg Parker.

Red Backlit MBP Keyboard

Update 2: If you are interested to see how FTIR works for illumination, you can check out this nice video explaining how LCDs work. LCDs combine FTIR with white paper sheets to rear-illuminate the TFT:

Posted in apple, Mac, Multi-Touch Tagged with: apple, ftir, LED, Mac, MacBook Pro, Multi-Touch
  • nic english

    nice knockdown and the links – Jeff Han – were v. interesting but … did you get the keyboard to work again properly as in pre ‘salad dressing’ rather than just reassembled?

    and yes it take me awhile to get here …
    cheers

  • reassembling went nice. but… some of the key switches were corroded by the vinegar. nevermind i bought a new internal keyboard via ebay. cost 45$.

    cheers
    johannes

  • Jake

    I was wondering if its possible to buy the keyboard layers anywhere.

  • hi jake,
    no, as far as i know, you cannot.

    i looked up for my disassembled pieces but i have not found them yet. i do not know if i threw them away. but they are really simple so maybe you can build them yourselves.

    cheers,
    johannes

  • Jake

    Another question. My whole experiment here is to make my macbook unibody 2.0 non backlit, backlit. I know this is possibe. So i bought a keyboard off ebay but it didnt have the layers. So i need the layers. Another question is, can i take the layers off a macbook pro backlit keyboard. Are the macook pro layers the same? I found one on ebay that is a macbook pro. It has the layers, but it said its non working because there was wine spilled on it. Will that ruin the layers. And how does the cable for the backlit keys work. How does it attach to the keys and board. Sorry if its confusing.
    Hope you can help, thanks Jake

  • hi jake,
    there should be (at least) 2 problems connected with your approach:
    1: the plug with which your macbook’s keyboard is connected to the macbook’s mainboard is missing the necessary cables for the power of the background illumination led’s.
    2: the keyboard sits snugly inside of the macbook. there should not be any space for additional sheets.

    however, maybe you can make the necessary changes, anywaz.

  • Oliver

    Hi Johannes

    I’ve got a problem with the backlit keyboard of my MacBook Pro 15″ (european keyboard), pre unibody generation: It is not illuminated equally. The right side is much darker then the rest of the keyboard. I spilled some liquid of over the keyboard. All keys are working perfectly.

    Any idea?

    Thanks’ for your answer in advance.

    Regards, Oliver

  • hi oliver,
    i had the same problems with my mbp keyboard on which i spilt salad dressing.in my case the oil of the dressing was still present on top of the dotted transparent plastic sheet. if there is fluid on this sheet, the refraction index of the sheet will be minimized and most of the light will be emitted in the middle of the keyboard next to the leds and you will get an uneven illumination. but it’s only an optical problem NOT an electrical.

    i don’t know if in your case the different sheets stick together in a way that the refraction index of the dotted sheet is minimized or whatever. however, what you could do is to disassemble your keyboard (i.e. disassemble your whole mbp) and clean everything nice and neatly.

    cheers

  • This is essentially the same keyboard as the mid-2009 MacBook Pro has, right? I had a beer spill incident not two weeks after getting my 15″ MBP in June and ever since then the keyboard just has not illuminated like it did pre-spill, particularly at the outer edges.

    Regards,
    Tom

  • Pedro

    THANK YOU FOR THIS IV BEEN LOOKING ALL OVER GOOGLE!!! this should be like the first search result. you are awsome!

  • damn, my son spilt coffee over my keyboard. i’ve got to exchange it again. however, the brown illumination of my keyboard’s backlight looks very … interesting.

  • @Tom sorry for answering that late: no, i don’t think that this keyboard is the same than the mid 2009 MBPs.

    however, the backlight functionality is the same. thus, greg parker’s keyboard (as you can see in the image above) uses a red backlight foil.

  • Ben

    Many thanks for this strip down and explanation! I am not particularly technical however yesterday I managed to replace the broken backlit keyboard in my late-’08 Aluminium Macbook with a non-backlit one (the only keyboard I could find after months of looking!), yet retained the backlight functionality by keeping hold of the backlight sheet.

    It seems to have worked great (even the keys on the non-backlit keyboard are the same as those on the backlit one so did not need to be replaced!), however the backlight suffers from significant dimming at the edges. Do you think that this is due to the seal of the black plastic sheet being broken (necessary to remove the old keyboard), or is it simply due to a slightly dirty plastic reflector sheet (the one with the white dots)? My reflector sheet wasn’t spotlessly clean when I put it back in as I wasn’t aware of its functionality, and I was wary of separating it from the black sheet separating it from the actual keyboard.

    Essentially what i’m trying to get at is whether or not it’s worth going back into the laptop to have a clean – or if the broken seal on the black plastic sheet would render any cleaning useless anyway. I’m hesitant to do this as, as I’ve said, I’m not particularly technical and I’m scared I’ll damage the logic board or any connectors in the process.

    Many thanks 🙂
    Ben

  • hi ben
    judging from what you have written i think that the problem lies within the dirty dotted plastic sheet. in my opinion the black foil does only prevent that light comes out of the keyboard/foil bundle and is being reflected by the aluminum of the keyboard pit of the macbook’s body. this would result in an uneven illumination of the keyboard.

    all the magic of the even (and thus also uneven) illumination of the keyboard is caused by the dotted platic sheet. light of the LEDs in the middle of the keyboard bundle is dispersed and reflected endlessly within the transparent plastic sheet (this is what is called FTIR). only if this reflection is disturbed by a different surface (the dots) of the transparent plastic sheet the reflection is disturbed and the light is being refracted. as those dots are under the keys, the keys will be illuminated.

    to conclude, i think you could open up your mb again and clean the dotted plastic sheet. it should not come from the black plastic sheet.

    cheers
    johannes

  • pr1

    Hey!

    just wandering, if i wash my keyboard*in water) and let it dry for couple of days, will it still work
    ????

    i’m afraid to do that, cause i have no spare keyboard :>

  • i definitely wouldn’t wash the keyboard because there are metallic parts in there that will corrode if they get wet!!!

  • crag

    Hi John, I have a late 08 MB unibody (uk) with no backlit keyboard so I have fitted 1 myself, wasn’t hard to do. But….OSX still doesn’t give me the option to illuminate the keyboard. F5 and F6 still do nothing. In bootcamp tho running win7, it shows on the screen that the brightness is being adjusted with F5 F6 but the backlight is still out??? eather I have a duff BL or is there something missing in OSX if the MB doesn’t come with a BL as standard?

  • Niloc

    Hey, I wonder is the progress of replacing keyboard backlight color is same for 09′ MBP with older verison?

  • Max

    what is the best colorizer for red? where to get it? thanks

  • take a red pen and paint the leds red? i don’t know…

  • shayan

    many thanks to you Johannes for your guide ! it was very useful and i’m looking for this(changing backlit color)for so long time !

    peace…
    shayan

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  • Tony

    Hey Johannes… Someone spilled cola in my MBP. Center lights are only strong ones. Looks like you’ve answered where it is, what causes it, etc, etc. I was wondering what you used or recommend to clean off the dirty layers?

    **Also, youtube is DYING for video tutorial of someone doing this FYI.

  • hi tony,
    as i initially did not plan to make a tutorial out of the whole disassembly, cleaning, assembly thing, i have not shot any video footage of it. anyway, now it is too late for it, sorry.

    as to your question regarding the cleaning: as you can see in the picture above, the keyboard consists of four layers. except from the top layer, which is the actual keyboard, the other three layers mainly consist of plastic. only the bottom layer contains four LEDs. basically, you could actually rinse the two center layers and clean it with a soft cloth (do not scratch the layers!). i cleaned the bottom layer using a damped, soft cloth. the top layer (keyboard) is only indirectly involved in the illumination thing. so it is not important for illumination purposes to clean it. if, however, you want to clean it as well (at least from the bottom), i would also use a damped, soft cloth.

    do not forget to let everything dry completely before reassembly.

    hope that works for you.

  • Randy Hagerman

    Thank you for a very interesting discussion of MBP keyboard components. I have some info to share on this topic;
    If fully diassembled, all keyboard components can be completely immersed and cleaned in fresh water. Distilled water is preferable. I know this because I inherited a mid 2009 MBP [backlit] that had suffered a projectile vomit stream pooling on the keyboard and drying for 4-6 hrs. College parties! Aren’t they fun?
    Anyway, I removed every key cap from the keyboard, separated all keyboard components, and washed them thoroughly under running water. The underside of the key caps was hardest to clean, as the vomit had hardened fully. I positioned them on a foil tray and sprayed them w/ a foaming germicidal cleanser, which I let stand. Next, I scrubbed all with a toothbrush, then rinsed them under hot tap water. [Hot tap water imparts a bit of heat to any object which helps it dry more quickly and thoroughly.] I continued rinsing all components in hot water after cleaning, then blotted them dry as quickly as possible w/ a Bounty paper towel to take advantage of the heat. I then let everything air dry overnight before reassembly.
    The outcome? Alas, the logic board could not survive human gastric juices mixed heavily w/ alcohol, while running iTunes, and dripping on it for hours. [It may have- IF immediate action was taken. You have but one chance to save a laptop from a liquid spill. You must act FAST! Invert it and power it down. Then you must clean and dry all affected components.]
    I replaced the logic board and the cleansed keyboard worked well.The backlight also worked.
    I hope this may help someone now and maybe help others in the future. Much time and money can be saved IF you know what to do BEFORE a liquid spill.

    I hope you get a laugh from it too. God help me, it’s all true.

  • thanks for that insightful comment! i had a good laugh.

  • Randy Hagerman

    I’m glad you enjoyed it.

    So, now that I’ve got 2 extra MBP backlit keyboards [and I like to learn], I’ve decided to venture much deeper into their workings. If I don’t know what’s broken I cannot begin to repair it. It’s best to understand it from the bottom up, in my opinion.

    I’m currently waiting for some conductive ink to arrive. If all goes as planned, I’ll share my ideas, pix, and techniques with you. Even if it doesn’t work out, I’ve gained some valuable insights into keyboard construction [particularly MBP] that I’ll be happy to share w/ anyone.

    My next reply depends upon interest. If you wanna let this thread die, I understand. I should be finished w/ my experiment by 12/14/12.

    Please let me know your feelings on the subject. I don’t want to overstep my bounds or bore anyone to death!

  • actually, i really enjoy ‘digging’ into such things. there is enough shallow stuff in the internet. so why not discuss some real contents here? go ahead!

  • Randy Hagerman

    I apologize for not posting some deeper info on MB Pro keyboards by 12/14/12 as expected. I still have not received my shipment of conductive ink which would allow me to complete my full investigation of them.
    I prefer to send my complete thoughts and photos out. I don’t wanna post something that i consider ‘half way done’.
    I hope you understand and I’ll prepare my results ASAP. I gotta find out what became of my ink order first

  • Randy Hagerman

    I’m certain this information will never be used for the practical repair of MBP keyboards, as it is extremely labor intensive to get to the damaged PCB level. I invested the time to understand how their keyboard circuitry works, so I might understand why a specific item [or items] fail.

    Since I have 30+ pix to accompany this post, I elected to upload them to Picasa and supply this link for anyone interested;

    https://picasaweb.google.com/113412570197005006452/MBProKeyboardComponents

    Please click individual photos to view comments which describe specific details. [The slideshow option will not display my comments on any pic.]

    Component List: Top > Down

    1. Key Caps
    2. Key Scissors
    3. Black-Out/ Key Return Sheet
    4. Triple Lamination PCB Assembly
    a. Top [PCB] Sheet
    b. Middle [Spacer] Sheet
    c. Bottom [PCB] Sheet
    5. Structural [Metal] Sheet
    6 .Light Dispersion Sheet
    7. Double Lamination LED Assembly
    a. LED Reflector Sheet
    b. [6] LED /LED Power Supply PCB Sheet

    I’ve tried to explain my understanding of each component’s workings in my photo comments. I welcome any questions/ comments/ corrections to my conclusions. If anyone has specific Q’s on component disassembly, I’ll be happy to assist them.

    I’m currently awaiting the conductive ink, which I used to repair the damaged PCB circuits, to dry before I reassemble and test this keyboard. I’ll post those final results ASAP.

  • Emily

    Is it possible to make the keyboard color rainbow? If so, how?

  • well you could take the transparent piece of plastic and attach a rainbow foil to it. however, i suppose that you have to make that rainbow foil yourself. for instance, just take translucent pieces of differently colored plastic foil and put them on the transparent piece of plastic. alternatively you could take a rainbow gradient from google images, print it on a self-adhesive foil (like this) on an ink jet printer and attach the foil to the transparent plastic.

    as i have not tested any of these approaches myself, i do not know if they really work.

  • Olive

    hey! should I be concerned if a couple of keys on my macbook pro are brighter than the others? (7, 8, and rewind/backward keys) the brightness difference is just slighlty noticeable.

    my 13″ MBP is new and I just bought it a few days ago. I have not spilled any liquids on the keyboard.

  • actually, i had the same issue on my old MBP on which some keys were lit brighter than others. i attributed this to dirt in the keyboard and to LEDs wearing off when they grew older.

    if i however had the same problem on a new MBP I would find this annoying as none can be the case: it is neither dirty nor is it old. i guess that either the leds or the plasticboard are faulty or the MBP does not control the LEDs correctly. maybe you could reset the parameter ram when rebooting the MBP and check whether this resolves your problem. or maybe this is a firmware problem of your mac series. if you have not done so, you should check google if other owners complain about the same problem. or you could just walk to an Apple store ‘genius’.

    cheers

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  • Sir Potato

    excuse me just asking is there a software for switching on keyboard light without dismentaling it

  • uuuh, i am not sure if i understood what you mean. anyway, i do not know any software allowing to switch the keyboard light on or off manually.

  • Any idea to implement this concept on apple wireless keyboard G6? all the parts are fit for G6?

  • uhm, as far as i know, there is no way to remove the aluminum cover from the top of apple’s wireless (and non wireless) keyboard without irreversibly destroying it (see, e.g., here).

    if you were willing to live without the aluminum cover (or 3D print your own cover) in order to get a backlit keyboard, you would have to add a light source inside the keyboard and you would need to somehow retrieve power for the light source in the keyboard. and then you would have to find a mechanism to switch the light source on and off. oh, and the keys seem to made of solid plastics, so they are rather not translucent. so you would need new keys, too.

    so i guess, i have no idea how to implement this on an apple wireless keyboard.

  • omar espinoza

    I have a question, instead of replacing the led lights on the keyboard, can i just get a colored sheet or layer of some sort? i wanna try it out, as much as i don’t know, i was wondering if that would work and or be easier?

  • sure, you can just put a translucent sheet of colored plastic directly above the layer with the LEDs.

  • Hey Johannes, you mentioned that adding the color filter will make the macbook a bit hotter because it restricts airflow, is it really a concern that big and if so is there a way to avoid over heating? also would like to ask if you know if the actual keyboard has any leds, or is it just those 4 in the paper.. my main concern is over heating, thanks in advanced.

  • i am not 100% sure if an (additional) color really inhibits airflow. actually, if it is shaped like the other layers, there should be no problem. but, as i said, i am not sure about it.

    regarding the LEDs, in my model (back in 2009) they were integrated into the white plastic foil in the bottom layer. there were no LEDs in the actual keyboard. i do do not know whether apple has changed this approach since then, but the build-up of this background illumination approach was quite sophisticated. so, i guess that apple did not change the approach.

  • Allan

    Hey bro!

    I’ve just finished replacing the top case of my macbook pro 15″, mid 2012, and I noticed the keyboard backlight is not even. Left side is a bit brighter, not by much but noticeable.

    The ribbon cable that controls the backlight did snap when I forgot to disconnect it before lifting the logicboard….I put it back in place though and got backlight on. Would something like that affect the intensity of the backlight on either side? Or it’s those sorts of cables that it’s either working 100% or dead?

    Also, the left side is where the logic board is, so maybe I could’ve over tightened it so that it makes more pressure towards the keyboard?

    Finally, continuing with the “pressure on the back of the keyboard idea”, I have a OWC data doubler, which might not do as much pressure as the default optical drive bay in the right side of the topcase…

    Any ideas of what might be going on?

  • well, i think you narrowed it down pretty precisely.

    on the one hand, it could be caused by the ribbon cable, if the ribbon cable would not work in a 100% or dead manner. in the image above you see four leds that emit light into the transparent foil. what if one of these leds didn’t work because one wire inside the ribbon cable would be broken? maybe it would cause uneven lighting as one led wouldn’t work and the other leds would even shine brighter because they get more power.

    on the other hand, the uneven lighting could also be caused by pressure on the different layers. however, bending on the transparent plastic sheet does not have any effect on the reflectance behaviour of the transparent sheet (if it had such an effect optical fibre cables would not work 😉) alternatively, maybe the sheet with the dotted print pattern on top does not touch the transparent sheet in all areas because it is bent? then the light would not emit where no contact is established what could be causing the light to spread unevenly.

    as you can see, i only do guesswork…