The Microspheres Hiding in your Phone's Screen
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- เผยแพร่เมื่อ 30 ก.ค. 2023
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Today we're looking at Anisotropic Conductive Film (ACF) or tape. This is a special tape that's used widely in LCD/OLED products to bond the electrical connectors to the glass display.
It uses small plastic microspheres coated in metal to create the electrical connection, and the arrangement allows a single piece of tape to establish connections in only the "Z axis" of the tape (through the thickness), without connecting adjacent pads
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I forgot to mention: application is done with a hot bar and mild pressure. My tape for example (AC-7106U) needs 180C and 2MPa pressure for 10-15 seconds. Strange Parts shows how it's applied to an FPC about two minutes into this video if you want to see it in action: th-cam.com/video/ks-lS11TIaY/w-d-xo.html
The adhesive ends up being closer to a permanent heat-set epoxy than a removable tape adhesive. I'm trying to debond the microchip right now to take a closer look, but it's proving very tenacious!
Good work!! I forget what it's called but the old LCD displays used a flexible rubber "Z" strip with thin metal sheets with flexible rubber. Worked really well!
Thanks for that additional info. That was the biggest question I had after watching this. Trying to work out how hard they need to push the component down on the tape to crush the balls, and how it doesn't just spring back off, In other words, what keeps the pieces clamped together? Also the example where the traces were contacting the pads without the aide of the balls, I was trying to work out how that happens when there should be some thickness of tape between them. Heating it must liquefy the carrier compound to an extent that it pushes out of the way, and cooling it would set everything and hold it in place.
good craft
@@fjs1111 zebra strip and it failed pretty regularly lol
The element detection feature is so cool to see!
The old school larger scale version of this is called "zebra strips", used for connecting lcds to rigid PCBs.
Fixed many a Nokia and I think Gameboy? With a bit of paper to apply a bit more pressure to those zebra tapes back in the day. I didn't even know this new one existed, that's pretty cool.
Yup. Used those in the ‘70’s
Long ago I used the Tattletale 8 SBC which used the similar 'Squishy Bus' to mate to a carrier board. It was always a little concerning due to board flex but it seemed to do the job ok.
Gonna see if I can find some in my pile of old electronics! Thanks for the tip, I hadn't see that before!
Aye! That's what I've known it by. Still being fairly new to circuitry and building electronics, I only learned of it a few years ago. Real neat!
It's mind-blowing that this works as well as it does. It sounds like one of those concepts which works in theory, but would be wildly unreliable in practice.
I learn so much from your videos, as a practicing engineer I always go "Oh, that's how it works."
IM gay
@@nilstrobaggia735👍
Comments like yours help me know when I found a good channel 😃
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You mention the diffusion barrier. To me, it's amazing that it's possible to power large electronics from 100 years ago, or microchips from 30 years back, and not have them be completely diffused away. For older RAM, cache and EEPROM chips the bit rot is starting to set in after about 40 years, but that's nothing. If it were up to me, I'd be freezing retro items, so they'd stay in a running condition longer. Diffusion is a silent killer.
And at that, it's not so much the metallurgy (which takes place more up in the 300-600°C range) as the packaging. It feels like... a lot of the early plastic encapsulations suffered from poor dimensional stability, resistance to moisture, and adhesion to the lead frame, perhaps? And I say "suffered", but they were certainly reliable enough for their time (lifetime of a couple decades is well more than any commercial product should expect!). That they often do so much better than this, bears some testament to their success, to the delight (as well as eventual consternation) of vintage enthusiasts.
These corrosion processes depend on environmental conditions like oxygen, moisture, and trace corrosive gasses; just keeping things dry and reasonably clean (stored in boxes, away from dust) goes a long way, and keeping things completely dry and free of contamination (silica gel + activated charcoal adsorbent, say?) and cool (sure, they could be frozen, or even less), should jack up the lifetime.
The alternative of course is choosing wholly metallurgical components -- i.e. replace those fragile plastic parts with CERDIPs and whatnot. Not always feasible of course, for many of the same reasons they weren't chosen in the first place, for that matter (availability, cost, performance, size/shape even).
@@T3sl4 I think he is referring to the physical process of diffusion, without an outside influence. At room temperature, the statistical chance of a particle of metal acquiring enough energy to move around the surrounding structure is almost 0%, but not quite 0. And there being billions of atoms, from time to time some of them will indeed acquire enough energy to move. Over the years this will degrade performance, until the device stops working. The higher the operating temperature, that much faster will diffusion occur (it's exponential).
@@WetPig Right, but long exponential tails aren't meaningful even over historical time scales. Most semiconductor, metal and ceramic materials have activation energies far above room temp; but the other mechanisms I listed do have lower activation energies, so will tend to dominate.
Maybe wacuum packeting those? Totally remove air. It removes even moisture, if there's some. Maybe after that whole thing could be left under liqud nitrogen to for storage.
@@T3sl4 Actually, a large area of defect reduction in semiconductor manufacturing is preventing copper from vias from diffusing into high-K dielectrics at the normal semiconductor's operating temperature and conditions through the use of diffusion barriers. Temperature is not the only factor that influences diffusion in semiconductors.
I spend countless of hours asking my dad how stuff works as a kid. I never stopped wondering and I will never get tired of understanding how more things work. Your videos are on a higher level of what I could learn in physics from school and better than "how its made" and "whats inside". it's really high level stuff. I appreciate your work 100% - I hope you will keep making these videos
Try finding out how they make acupuncture needles and the micro needle they inject cells with
holy! This visualization with the gel and the bearing balls was so simple yet amazing. Really enjoying your videos!
I'm an EE and I've used ACF hot-bar bonding many times, but I've never seen images like these - great stuff.
Which companies do EEs get jobs easily at? I am a software developer but I have always been interested in electronics. I wanted to setup a home automation company when I was young lol but the country I am from, it's more likely to not happen. In my country there's no job security for EEs you see. If there was, I probably would be in that field.
everytime you post, whether its the main topic or not, i learn something i previous thought impossible has already been solved
Nothing is really impossible for everything a human can imagine or conceptualise has it's bases on what we have observed or known
It's just finding a way of materialising
@@a.r.h9919 Yup, another way of seeing it is:
Nothing is impossible but most things are economically unfeasable.
That sponser integration was smooth like a silka.
First learnt about Z-tape in Applied Science's video about building the replica DSKY display, where the adhesive ended up pulling the electroluminescent phosphor/dielectric/ink stack-up off the glass. Very cool to see a deep dive on how it works!
Oh neat, I didnt remember that he used ACF for that project! Will have to go give it a re-watch
Me too!!!
The demo you did alone was worth watching this video for. It explained everything perfectly. Crushed it dude.
absolutely blown away by the video quality in this one. can only imagine how beautiful these shots are in 4k because 2k is already stunning. great work
Man I’m so happy that I randomly clicked on this video. I absolutely LOVE being educated about super cool things that I’ve never thought of before, and then walking away understanding how they work, and why they were designed that way. What an incredible video. Thank you! You earned my like and subscribe fair and square!
If you have a green (best color for visibility) laser pointer, you can reflect it off if the surface of a TV or other screen and see the individual pixels in the reflection. You can also do this with a CD or DVD to see the track made of pits and lands.
I've been fascinated with this effect of using laser light to view microscopic structures as a reflection. With no lenses. I'm wondering if this method is used in actual scientific applications to visualize microscopic structures.
I always find my best ideas have already been thought of, so I expect that somebody would have discovered and exploited this in the last 50nor so years.
Laser microscopes are a thing
Have you seen how holograms are made?
Also, obligatory cheap green lasers can punch your eye out with invisible and undetectable 808nm and 1064nm infrared light. Any DPSS laser like the common 532nm is packing a pump diode that puts out much more than the "safe" 5mW legal limit. Some have IR filters, most cheapos don't.
Most any other diode laser, including the new green ones (~500-520nm) is probably grossly underrated on output power due to marketplace regulations. Before those regs, they used to sell them as toys to light stuff on fire. Now they have to be below the legal limit to sell but of course nobody setting these rules ever checks anything.
Be careful with those reflections!
Really enjoy the fact that you are so clear and concise with your words, that I was able to watch your video at 4x speed and understand 99% of what you said.
Well done.
Most folks only get 3x.
My guy what’re you even training for that has you watching casual TH-cam videos on 4x speed. I just tried 2x which is the max and it was understandable just annoying as hell. Like genuine question what possible reason could you have to watch this that quickly, it’s not like you’re studying for a test
Speaking of LCDs, Ive heard they use tiny glass balls to separate the layers of glass. A cross section would be cool to see. Perhaps if you're careful enough we could see what happens when the layers are to close or to far apart.
You're correct about the corrosion resistance for that nickel coating on the pads. We do the same thing for the copper IHS on CPUs. The nickel doesn't corrode away nearly as badly as copper will when just exposed to the atmosphere, let alone any moisture. You wouldn't want to have your traces going green on you, or the surface of your CPU becoming pitted over time.
Chips won't go pitted, because there's generally a layer between them and the IHS, such as thermal paste or pads. So even copper in contact with an IHS doesn't really corrode in its usable life, because it's protected from air at the contact point. Of course everything else would corrode, and that's mainly for aesthetics rather than functionality.
@@peoplez129 It's not the inside we're concerned with. That is sealed from the outside world. The silicon itself won't corrode, since it already has a layer of oxide on it. The greater concern is the outer surface, which is exposed to the atmosphere for extended periods of time. Pitting takes a long time and is the extreme example, but even tiny copper oxide spots ruin the thermal properties of that area of the IHS and create hotspots.
I suspect one of the reasons they used electroless nickel phosphorous plating on the pins, aside from corrosion resistance, is that it promotes surface uniformity and reduces surface porosity. Ensuring that there are no surface voids or pits is likely a fairly major reliability factor for applying the tape. Since bare metal is fairly porous, there's a tendency for hydrogen absorption (and adsorption), which might lead to bubbling and delamination of the tape as a result of degassing. A medium-phosphorous EN plating is a pretty simple and relatively cheap way to solve all of those problems simultaneously, and the tooling for it is pretty ubiquitous given that we do it all the time on ENIG / ENEPIG surface finished PCBs.
I love the physical model you made. It shows the principle working so well!
If enough conductive microspheres did manage to bridge two adjacent traces, would the magnetic flux of the sudden current flow cause them to separate? It feels like the sort of system that would tend towards un-shorting itself, which is cool
They probably still wouldn't meaningfully conduct, since there isn't any compression giving them proper contact with each other.
I'm mostly surprised that there aren't too many issues with some unlucky contacts not having any spheres.
Great work!
Have you tried to measure the resistance of such connections?
I was going to... and totally forgot 😅 The spec sheet for mine claimes 1ohm resistance so it's just "ok". Also limited to
@@BreakingTaps Is that all it says or does it give it as a per area? I'd expect larger or smaller pads would affect the resistance and current capacity.
@@LanceThumping Datasheet just says "ITO electrodes all over / TCP; bonding width, 1.5mm", so not entirely clear to me what the actual dimensions were. 😔 Spec sheet is here if you'd like to take a look! www.fsrkj.com/upfiles/201712/22/af0aa1f1cb2886b6f.pdf
Very cool👍. It’s un-freaking-real how much science, engineering, math, manufacturing, ingenuity, creativity… has gone into making every bit of a phone. I’m sure I know only a tiny fraction of it, and still it’s unreal.
right? I've heard that they use psychedelics to reach this level of visualization and creativity 🙂
these advances are beyond reason, the tech is almost other worldly
Alien tech
There's nothing complicated about connecting two conductive surfaces with a metal ball. They envisioned how they could make it happen, and this was how it was made to happen. You just 'aren't that guy' if you cannot come up with solutions like this.
@@BuzzingGoober No it’s not complicated. Most technologies are simple in theory, but producing “plastic” micro spheres, coated with conductive material, takes some doing. Are you a bot thinking your talking to a noob?
Man this was an absolutely excellent video
The work you do is just incredible man! Thank you so much!
Wow, that was really impressive to see. You post some of the best videos out there, I'd happily watch longer form content.
Agreed. This video was over way too soon.
Well heat bonding is the solution the tape is a newer invention that doesnt last as long as it peels with heat and age.
One of the best interviewers on YT is Brady Haran who has several science channels. Numberphile, Nottinghamscience, SixtySymbols and Periodic Videos and others. His genuine curiosity and really good questions (research) get people excited to talk about the thing they love.
Love these close up dissections of common items where the SEM reveals details that I never knew existed
I like how you make your videos so interesting, like you're telling a story
Thanks! Really appreciate that!
The element detector looks absolutely sick
I've never seen a guy so dedicated to reading his comments. Almost every comment I see is liked by this guy or even commented on. Loving these videos so far, the explanations are easy to understand but still don't simplify it too much. Best informational channel I've seen yet.
Seeing the metal levels and the vias between them was fascinating! It really shows the thickness difference between the silicon piece and the metal layerers that were deposited on it.
In old electronic watches kind of sponge was used, it has repeating layers of ruber and graphite(?) thinner than space between contacts and it was put (not even bonded) between glass and circut board contacts.
Someone just mentioned that to me: Zebra connections! I hadn't seen it before, but going to go dig through my old electronics pile and see if I have any laying around. TBH that's a lot more like what I was expecting from the ACF, some kind of pillar structure, not just random particles :)
an elegant solution to a complex problem!
The probability of the spheres forming chains reminds me very strongly of concepts like percolation and clustering in random graphs.
Thanks for sharing, great video! I especially liked how you visualized the different elements. Really interesting!
The presentation of this video is simply incredible.
Excellent explanation and demonstration! Quite impressive how you prepared all this for a general audience!
This is the best video about acf on the entire internet so far.
Perfect analogy.
Well done.
This is awesome, thank you, I never knew that. I remember the rubber/carbon impregnated striped rubber strips they used to use to bridge the connections between the glass and PCB. How things have changed, but somehow also stayed the same.
Your videos make my week. I really appreciate your videos !
I absolutely loooove simple, yet brilliant in its simplicity solutions to a problem! Never even known about this, so thanks for that!
Such a simple and clever solution to the problem! I assumed it would be some kind of complicated honeycomb/pillar structure when I first heard about it. But nope, just little spheres :)
I agree. The term I like to use is elegant. Simple, easy, cheap, reliable, fast.
This is such a great explanation. Incredible visuals and editing.
Cocktail nuts!
That also shows why these connecting bits are so fragile: the conducting parts are absolutely microscopic, so any damage will mean a point of failure very quickly.
Just found your channel. Will definitely recommend! This is so interesting and well put together, thanks!
Learning so much.
This is amazing! Thank you for sharing this in a way that a non-technical person could understand!
Great video. Thanks for making/sharing. Stay safe out there.
This is the first time I have ever seen any of your content and I am extremely impressed! This is the exact kind of thing that makes my brain so happy! Liked and subscribed, for sure.
As soon as you did the ball bearing thing, everything just clicked! Well done!
Your a beast dude. I just found this channel but I am really enjoying all tye in depth information on a small scale thank you for the work you put in !!
awsome video, very informative and interesting, I was and still am astounded by the in depth and detailed micro scope work and description you gave so that even a lamen like myself could understand it. I have learned a lot just by watching this, you have enlightened me, Great work.
thanks for sharing this awsome content, glad the feed showed me this video.
I read the title and immediately thought: "They must be using some fancy crystal structure that's conductive in one direction". But instead I got tape and conductive balls. Love it. You never fail to amaze me.
Honestly that was my assumption too! I figured it had some kind of pillar structure :)
@@BreakingTaps Crazy how simple some solutions to complete problems can be.
Thank you so much for making this video. I was curious about how this process worked when I tried to repair a LCD TV years ago.😀
You somehow always pick a subject that is of great interest to me and I feel like I actually learn something, not just some trivial minutia.
Wow! That is a much "messier" process of establishing a conductive pathway than I would have thought. Very cool and extremely well demonstrated and explained. Thank you!
Was involved once in bonding ICs to glass. This video sums it up nicely!
I just want to appreciate the effort you put into making this video. Thank you!
Thanks again for tremendous - as usual -video! I love to learn about this kind of thing. All the work you do to make these programs is top quality. Subscribed today and looking forward to seeing more from you. Good fortune with your Magazine, keep us posted!
Man, this solution is genius. And the way you showed it to us and explained is even better! You've just earned a new subscriber. Best regards from Brazil
This is such a cool video! I didn't know this even existed, and this is a great way of showing it off.
Polymath channels are probably my favorite.
You're doing a good thing.
Thank you for the content and effort for creating it. As always magnificent.
The Levels of Precision required is just so fascinating. I've spent a couple years wandering. Thanks. 😎
Amazing and informative video. Amazed that you discovered that information about how those screens work and then clearly explained how it works. Subscribed!
This is remarkably simple and genius, i would never have known this otherwise and I thank you for sharing this!!!
I appreciate your videos a lot, I know it's a lot of work. You have some fascinating insights to share with that amazing inspection equipment you have. I just love that element analysis feature, so useful.
This episode was a rollercoaster to me! Brilliant work as usual.
I love how you casually said "if we turn on the element detector under the microscope". Then show the wonderful elements images effortlessly.
I disassembled a lot of devices with lcd screens and always asked myself, how works the electric connection. Thank you very much for the details and well presented information which is also valid for a lot of your other videos.
Pretty cool and interesting video, love the sections... You put a lot of work into this and it shows pretty clearly. Thanks.
This is fascinating. Thank you!
Such a geniusly solution to a very complex problem
Really cool! thanks for this and all the videos you upload!
thank you, few people explain subjects in a interesting way never knew adhesive tech was so interesting.
I havent subbed on a yt channel in probably over a year. i just watch videos and let the algo do the rest but your channel is really worth it. Good job man
Damn, there are a lot of things we just take for granted. Thanks for this awesome visualization
Your videos always blow me away. I always learn so much!!! I'm super interested in this magazine!
very informative. It's so impressive all that is done to enable these screens to work
that is such a simple clever solution to a complex problem, wow
You delivered another 100/10 video.
the best demonstration of the principle i have ever seen.
the Quality of these Videos is incredible!
I was having a bad day until I found your channel and now I'm learning something new and I'm blown away.
I have yet to watch a video of your's where I don't learn something new. Keep up the great work dude, had no idea about this tape!
🥰
Finally I've got an explanation why you can repair an LCD display that has missing or glowing row of pixels by disassembling it and pressing the contact zone with a pencil. Until now it was like a woodoo trick that has weak hope on success. Now I see that it is actually a very straightforward solution and the issue itself understandable.
It seems like the crushing of the balls not only allows a larger contact area, but also makes it possible to have smaller balls that reduce the probability of the hollow spheres bridging to each other
Only just discovered your channel and subbed of course, what to say... Well , quality work I'm loving it keep up the great work
That small microchip is driver IC and connection points we call it Au bump.
Usually made by sputter TiW and Au layer on IC’s Al pad (UBM layer) then plating Gold on it, also we have Cu Ni Au bump and Cu bump processing.
In this video cross section is Au bump definitely.
I've wondered how this was done many times...thanks for explaining the tape that does the trick!
This stuff is really brilliant.
Simple yet smart design.
Fantastic, always wondered how the tape works.
damn, this is so phenomenal! thank you thank you thank you for producing such high quality content.
Brilliant. Well explained.
Amazing work on explaining this. I’d wondered how this was done.
Beautiful imagery as always!
this channel is my favourite channel, not because of the great informative knowledge, but because whenever i get interested in any topic their new video comes with same topic a few days later..
Yes that is amazing engineering!
Subscribed. Marvelous work. I've been interested in electronics and science since a child. Have been in radio repair in the military and electronics as a hobby all my life. This was a great visualization and explanation of the bonding process. Thank you very much