EEVblog #465 - LED LCD Panel Teardown

hi welcome to teardown Tuesday I thought we'd have a look at what's inside one of these LED LCD monitor panels this is the one I got from the dumpster dive 27 inches absolutely massive it was our cracked as you saw in the previous dumpster-diving video but what's inside this thing well we'll find out and yes look it is kind of warped there something yeah seriously happened to this thing when that photocopier was all that laser printer was dumped on it during in inside the dumpster what a bummer but anyway I've never actually taken apart one of these um LCD panels before really and this is a lead one it hasn't got the cold cathode fluorescent lamp in it so it's going to have some pretty good LED strips and maybe you know a diffuser plate something like that some sort of diffusion technology to get a nice even backlight on the thing so I expect probably you know - I'm not sure if they have it on all sides but maybe on two sides like this they'll have some LED strips or something like that and diffuser plates and all sorts of stuff so let's see crack this thing open or before we do let's have a look at the PCB here and there's the main chipset on this thing it's a CMO CM 20716 a not going to bother looking it up but there's some serious termination resistors there and that comes from the main connector which comes from the control board so then you know that's the input and then this must fan out to all the other driver chips which are then go into these flat flex cables down here and there there are soldered on with a hot bar our techniques so they come across with a hot bar down there and actually press down on these and they sold as these flat flex strips down onto the board they're very common technique for this sort of thing so uh let's whatever there's nothing much else on the board there's a little low dropout reg there something there's something else here that's a CMO cm5 a - I'm not even going to bother to look these up not too fussy um oh look at that that looks interesting looks like that's been ah look has that Freud has that been fried or has it been reworked I don't know something's gone wrong there maybe that it's what that's all that was wrong with this thing I mean it is actually I shattered the panel but that's maybe why it was originally dumpster dived or dumpster a toast to begin with it's almost as this something's gone horribly wrong with that chip there I think maybe that's uh died a very sad death I think so maybe yep that's what the reason that this thing's been tossed out perhaps who knows anyway let's not speculate about that somewhat dc-to-dc converter stuff big inductor here lots of parallel caps here tons of them really getting the inductance down there and there's not much else on the board so let's take it out and flip it over one of the interesting things is this is a pretty darn long board it's like 55 centimeters long so you know they they've really gone to town there of course some you'd have no problems having this some assembled through the assembly machine usually because length usually isn't a problem it's usually height in sight you know certain width inside the pick-and-place assembly machine but usually they can do any size a length like this but sometimes you will not there's some bare board manufacturers won't be able to make a panel that big and ER they interestingly I can't see any breakout tabs V grooving or anything like that that board looks fully routed on all edges so it looks like that just that individual board has gone through the pick-and-place assembly process or more likely they would have done like eight well it's a fully routed board and then they've done like a custom jig like they would have had lucky they would have you know it made a custom plastic jig or something like that to hold the board in place and they would have had multiple channels like this so you know maybe they had five boards stacked up like that in five boards then moves their way through the pick-and-place our assembly machine but let's say flip the sucker over and let's see what's on the bottom side well that's surprising folks look at that absolutely nothing on the back there no extra drivers or anything like that just a whole bunch of a parallel traces running the full length of this thing so there's got to be some more circuitry on the back of this panel that ship ain't going to handle everything folks you're not actually sure which order to get this out there were a couple of screws along the bottom here but that's it there's no other screws like along this side down here it says be hone in place buy some more clips so sort of get in there and sort of lever it out and it looks like should just pop out well that's the that's the plan anyway here we go folks tada ah pop back in bummer there it is ah got it finally aha there's our white reflective back in I would say or is that here nope I would do well yeah white reflective I guess they're not going to make it silver so that's so that the light reflects back evenly off the back of that that's it there we go yeah why don't I say I'm not sure what that is not sure what a material that is probably has a high reflectivity be great for my white balance I can sit actually yeah I might keep that I'm assuming it's a pure white it looks pure white to me could use that as a nice white balance card for my camera how do we need so we have that and now we have ah and this has a nice I'll get the macro lens out out in a minute you won't be able to see this but that this has a nice back in on and this has an etched pattern on the back of it here I can feel the etched pattern on it like little little dots they are tiny little dots and these are so I still can't see the LEDs in here which is really kind of unusual there they are don't there we go there's our LED strip all the way along the bottom should have known that there's our connector there we go as our lead connector and there's the lead strip all the way so it's only one side ultra I was wrong I thought it'd be on both edges but it's all it's coming from there's at the top of the bottom I'm not sure now anyway umm it's just coming from the top or bottom that's a really neat LED strip though um presumably I'm going to I'm going to take that out they're obviously not going to be in well are they in serious how many is on there if you wake up in series and you were you know three volts per lead that's going to be an awfully high voltage ah array otherwise if they're parallel they have to have a current share in resistor and I oh yeah yes I know no that's silkscreen are getting off the macro I thought I saw I can't share and resistor for each one but there's not I don't think it's on the bottom so I'm going to assume that they're all in series well we can measure that later that's going to be fun if it is we'll get out the high voltage power supply and power this sucker up by the way I didn't get the part number on this one made in China it's a chi me opto electronics brand panel whether or not it's a you know just a rebadged art from one of the major manufacturers I've got no idea if you've got any details on that I guess I could google it but I won't bother at the moment if you do have any details on exactly who manufactured this and what planter please leave it in the comments so this is our light Gide and these are you know fairly simple in terms of their construction I'm not sure the exact material some sort of you know polycarbonate or something like that nicely machined edge here which goes along the leads at the bottom here and at the top they've got a white strip on there which is the same as the reflective strip which just sits on the back here which you saw before this one here so here's our reflective strip sits on the back like that and then of course the light shines in here and then it bounces off well due to total internal reflection it it acts as a light guide and it's reflecting in and out in and out all the way it will bounce in off the top and bottom edges until it hits all these little dots on the top which we'll take a look at and there the thing that actually reflects the light then out the front like this and we can see that on this Dave CAD drawing here we've got our LEDs at the side here this LED strip this is our reflective film that white reflective film on the back these are little dots I presume they're like a chemical edge store something on the back of there I'm not sure how they actually manufacture the tiny little dots on the back but anyway um yeah this effectively works as a light guide so the light shows into here it'll be the correct thickness and they choose the correct angle lead blah blah blah to get the total internal reflection in there as best they can set a light bounces all the way around in here and sometimes they'll hit these little dots here well a lot of the time they'll hit these little dots here and then the light goes out the front like that at various angles of course it doesn't just all magically go straight out like that and that's what produces the light coming out so this is how they can get a an even light coming out across the whole panel from just an edge lit down here and there's multiple ways to do it with you know Evo have ones on multiple sides or you have like all four sides but I think most these days only use the one side like this so that's effectively how these things work very simple but then you need some extra stuff on top of here to really like you need an extra diffuser plate and extra stuff on here as will no doubt see - then get a nice even diffused light out because otherwise if you just had this you'd actually see little bright you know spot should see all the dots if you don't have the diffuser plate and other technology which will be on the top of here there you go you can see the little individual dots they're absolutely tiny and yeah as I said I'm not sure how they're actually manufactured whether they're you know chemical edge later retched or you know something else i don't know if you're getting got any info on how they actually manufacture those dots on there please leave it in the comments and then below that we have a nice diffusion layer look at that so actually this is where a lot of the technology could be in this diffusion film here you can see it you know it is quite a diffuse so there could be more technology in this thin diffusion layer here then in this polycarbonate bit here so I don't know if anyone has any exact details and stuff like that please let us know oh look there's another look at that is another very you can just see my fingers well it actually turns up much better on camera looks like it has lots of magic in there tie me kangaroo down sport time kangaroo this film is very interesting folks look at this at a really shallow angle like this it is that quite transparent you can see my watch and my screwdriver through there but if I move it up to be directly vertical to it it absolutely vanishes and as I bring it down the angle again very shallow angle again you can see it's transparent again but you bring it up that's like 90 degrees to it completely opaque look at that and that only works in the what I'll call the the y-direction here like this if I actually spin it around on the x-direction like that it actually vanishes no that's not just a trick of the camera or the light reflection I can't see that either so you go over the top and yeah so in the X direction it is only transparent at shallow Y angles like that interesting so it's no surprise that the LED strips are along this bottom edge like this so that is really quite fascinating and no it's not our polarized if I you know move you know watch around like that or anything like that I did a quick little a bit of research on this film stuff and it turns out it's called a prison film or lens film or if you get it from at 3m who's the main patent holder on this stuff it's called brightness enhancement film or BEF and it's 3m micro replication technology and it basically are well it's as it recycles the off-axis light so as I said before all this light the light source these are the individual dots down here that are you know shooting all this light out in multiple directions it just helps channel that and improve in boosts the brightness if you only got one piece up to 60% two pieces up to 120 percent so it increases the brightness as well as you know channeling a little directly outwards as you can see it improves brightness contrast uniformity and energy efficiency very vital part of these LCD displays and that's exactly how they work some of it gets recycled back to pending oh you're a bad angle sorry you're coming back in and some of it might even bounce outside the little prisms and that explains why by the way that we could actually see through it at a shallow angle in this direction and this direction like this and of course and we couldn't see anything in this direction because they're only manufactured in you know a long sheet like that so the direction you and we actually have some data as well here's the gain of it and you can see at the larger angles it just completely drops off like this either side of that so there you go those into all your art light and optics are physics stuff you can have a field day with this cinder as I said 3m hold like a lot of the patents are on this stuff but it seems that some of those are expiring so there's other manufacturers are coming into the play as well using their own technology and you can get different types have got standard on here's round tip wave you know and they all have various properties I have no idea which this one is but it is definitely one of these are prison films alright BEF and what's our final layer on here tada so we're not done yet there we go we have three layers of material I'm not sure that's so that doesn't look to be that doesn't look like it does anything at all just maybe a little extra diffusion layer or something like that doesn't seem to be doing anything special anyway so we've got three layers of diffusion you know a slasher you know reflective reactive type art material plus our LED panel as well plus our light guide panel as well so absolutely fascinating construction are pretty much what I expected I expected there to be a lot of technology in the in the led diffusion of this snare here we go here's where we can see our cracked panel folks I could see myself man it's very reflective yeah there you go and not sure if you can see those cracks but yeah probably getting some of it in there but yeah it's cracked all up here all the glasses cracked everything I shouldn't run my finger over that sorry yeah all you Apple fanboys getting excited sorry I'm not an Apple fan this was given to me by a fan who where I came to visit the lab who works at Apple so that's why I'm wearing it and it's kind of bit it's alright I like it even though it is Apple but yeah now we can see all our little individual pixels in there but we've got our cracked well and surely cracked the last panel so here we go I can take out the plastic surround on that came out very nicely but you can see how tall you probably see how it's all cracked yeah you can see all the crack marks up there and we saw that in the previous video but yep there's all our there are tiny little driver chips well they're actually huge driver chips but tiny in size the trace spacing down in there is incredibly small but yeah so we've got one two three four five six seven eight for the X direction and one two three over there for the Y and it is interesting to note that there was no extra rut layer in there that's it that's the front that's the front panel of things so the actual panel itself is oh yeah I can see the cracks in it now if I look at this panel at the right angle there we go you can see them all the way down there so this is a so the actual were LCD panel itself is the entire front surface there's no III expected there to be an extra protective film on there but it's not it's all it's all embedded and integrated although this film doesn't seem to be an extra layer stuck on there so maybe I can attempt to peel that off perhaps I don't know but there's a lot of layers they go into the construction of these panels let me tell you yeah yeah yeah yeah this could take a while all right here we go I got it I got it there we go protective films some sort of polycarbonate and yes that is the top polarizing film check out my flick 87 as they turn it around tada it vanishes so that's the top polarizing film they will also be a polarizing film on the bottom of the LCD as well so yeah that extra layer on the top here that'll also be the second polarizing filter on the back and then we go in we can start seeing all of our pixels fantastic look at that ah beautiful that's actually rather fascinating folks this is with my times 10 macro lens and you can start to see the individual red green and blue pixels in there and they would of course say this as a TFT screen that all had their individual art driver transistors and then all of this what looks like our purple stuff here these are all the actual wire traces leading up to there so there's like you know a hundred little traces in there going up to your individual arm columns there there you go that's one of the driver chips take a look at the tray spacing I'll zoom in on that in a second but this yeah there's they're all traces in there folks they are all traces look at them all the traces coming out here wrapping around going up there now to here driving each individual column in this case because these are the X drivers so and go Nova Tech and there's a part number on that sucker and look at the traces in my times 10 macro lens is not good enough to get down there and look at those traces I can see some of them and see some of them in here this is where the data's coming in probably but all the output drivers for the individual pixels not can't see a damn thing and it's not surprising really because if you do the math there's eight of these chips drive in all the columns and of course this is I've this is a full HD 1920 by 1080 panel so we're talking 240 traces each one of those chips has to drive count and folks oh I can just see them just if you watch this thing in HD you can probably just see the individual traces in there that's insane so there you go if I bring that in and out of focus can just see the individual traces absolutely tiny whoa you can see how these flat flexors are all sandwiched inside the polycarbonate I presume that polycarbonate are layers or somesuch in there you can see the tracers going around there and then right up there to the row driver a thing let's see friend zoom in on that so you can really see those traces on the inside of the panel down in there and then it comes up and there's our there's a row driver chip and just see the number down in there I don't know if you can find info on that I'd be very surprised but you never know never know what Google oh one anyway I wonder who were Nova Tech is whether or not they're just mill you know manufacturing the flat flex assembly or whatever or they have more to do with it I don't know and you might ask well what does that pattern up there doing absolutely nothing folks I don't know maybe they're just doing some equalization to put some extra copper in there so I don't know it doesn't curl or do something else funny I don't know they've taken a few liberties there that's for sure and my first guess would have been that they are test pads of course but you can't access them because they've got the film on top so I don't know maybe during the manufacturing phase before the final film is put on the top perhaps that's all I can think of and if we have a look down in the bottom corner down here check it out you can see the individual tracers going in or it's actually it's really hard but you can you can see the individual my screwdriver is massive here see the individual tracers running up and we should be able to see the red green and blue individual TFT transistors and there you go folks looking through my microscope really difficult because I've got my camera with the macro lens right up to the eyepiece of my microscope I'm not fully equipped for this sort of stuff but you can see the individual red green and blue pixels in there not a problem at all beautiful there's more of them down in there I've got who were shine my torch right across this thing at a very shallow angle there to get this shot but that's amazing look at that there you go that is the bottom corner of the panel you can really see that quite clearly now individual red green blue filters and the driving transistors are all integrated so you go into all the theory of how these TFT is actually work and there's you know slightly different manufacturing processes and things between manufacturers they all they're all going to have their own bit of secret sauce in there somehow but you can see those traces coming in from the bottom there and then drive in the the rows on the bottom there it's on an angle it's on a 45 degree angle here of course and but it is rather is rather fascinating up I've moved it let's just move across and there you go sorry about the movement here I'm just trying to hold my camera and tripod in place while focusing this microscope but that is incredibly interesting folks and on the front side of this you can see that they've got some sort of blue gunk around the outside whether or not that subtle part of the bonding process for all the various ah layers I'm not entirely sure in a one corner of the panel here look at that looks like we have some sort of test connector now I won't actually go into detail on how the liquid crystal TFT panel itself actually works as plenty of our tutorials and with great graphics and everything out there to explain the operation of these things but and in terms of how that liquid crystals work and all that sort of thing but basically what we've got is the diffusion plate at the back the white light as we've seen it generates like an even white light at the back of this panel and then as we saw on the underside here we have a polarization layer so that actually creates polarized light light which then enters the TFT panel itself and then the TFT panel the individual R pixels in there red green and blue they have red green and blue filters well they're not the pixels three of those red green and blue elements make up one pixel or one picture element and then when you apply an electric field across each pixel element of red green or blue one of those then you can individually turn on or off the polarization of the light passing through the individual red green and blue elements and so you can actually block or allow the light to come through those red green and blue filters and then we've got a final polarization filter on the top here and then that's the light that ultimately comes out you can turn on each of those things so all it is is that either allowing the light to come through from the backlight or not for each one of those are 1920 by a thousand and 80 for a full HD screen red green and blue picture elements and it's you know it's remarkable just the density in the technology in these panels absolutely phenomenal as you are saw in terms of the trace spacing and things like that well I tell you what these LEDs seem to be very very efficient folks they're incredibly bright that's not just my multimeter do tester doing that you really see the pattern emerging now that two three just lit but that's absolutely incredible from my multimeter and that LED board was quite a mongrel to get out to it was all stuck down with the double-sided adhesive tape on there and but this is a very very long board folks just keeps going and going and going and going and going that's one hell of a strip and for those playing along at home 61 centimeters long and you can see the traces on the back of that they've got a patent on there assaulted a couple of wires on here just so that we can have a go there's basically two ground pins in there basically plus four signal pins and there we have it folks I've got one strip fully lit up that's at 10 milliamps using my Keithley a two to five current source let me put constant exposure on that and let me change the wick a bit let's go down to that's eight seven six that's 1 million oh sorry that's a there we go we're one milliamp there folks that's not much at all I mean let's even go down at less than one milliamp that is naught point one milli amps should still be able to see that and of course if I turn my lab lights off that might help a bit but you can still see hopefully those lit up on camera there and that's at naught point one milli amps unbelievable so let's turn it all the way back up to nine point nine nine milliamps and that is SuperDuper bright I like it and of course it takes a reasonable amount of voltage to do that and but I can do that because I've got my I've got my Keithley currant sauce over here which I'll show you so of course it's really handy having this side Keithley current so it's not only can you dial in the constant current you want but you can dial in the maximum voltage there as well so I don't know what the maximum current is I mean that is 10 milliamps and that's quite bright but obviously not bright enough to do the panel if I had the datasheet for these things I'd know I mean I can go up to that's 19 milliamps that's pretty much our maximum that my Keithley current source can go up to that's incredibly bright all right so what happens if I put 20 milliamps through this thing and then put on the light guide with the diffusion layer on there obviously I haven't got everything lined up it's not perfect I'd have to put it all back in there and doesn't do much at all that's pretty boring actually there's the backside of the diffusion layer down there but yeah anyway I have to do some better experiments with this thing I could like take out individual layers so if you want me said do it like a separate video on that I I probably can because I have now got all the stuff to experiment with that and it could be rather interesting taking out the individual layers and seeing what effect they actually have on the on the total diffusion of this thing so anyway that's a quick look inside one of these modern LCD monitors of one of these are LED backlight one so lots of technology in the diffusion layers and all that sort of stuff that and that technology has advanced a lot if you remember sort of that notebook LCD screens from you know many years ago or not that many years ago only ten years ago or something you know you get the bright spots where you could see the well they didn't have lead technology back then of course they would have the cold cathode stuff but you know I mean you would see the hot spots and everything on the side and it wasn't really nice and even and diffused like these are you know you take for granted that you just get these nice diffuse things these days well spare a thought for the technology that goes into all is that leis and stuff and if you do have data sheets on other side layer material and everything please post it because that would be fascinating and there's tons of technology which of course you know thirty years of progress or something has gone into LCD technology like this just absolutely incredible the tolerances and you know Full HD and it's just absolutely amazing stuff but anyway I hope you like that and if you want me to play around with it some more please let me know all this site diffusion stuff and if you want to discuss it jump on over to the eevblog form if you like tear down Tuesday you know what to do catch you next time you you

Channel: EEVblog

Views: 118,902

Rating: 4.9236588 out of 5

Keywords: led lcd panel, lcd panel, led lcd tv, teardown, led backlight, led lcd monitor, lcd monitor, computer monitor, lcd tv, tutorial, full hd, hd lcd monitor, 3m, prism film, lens film, diffuser, lcd diffuser, backlight diffuser, display, display technology, lcd display, led lcd display, rgb, filter, tft lcd, tft display, tft monitor, liquid crystal display, how it works, inside, technology

Id: kdtyxt9OLlU

Length: 34min 13sec (2053 seconds)

Published: Tue Apr 30 2013