The Microspheres Hiding in your Phone's Screen

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: https://www.youtube.com/watch?v=ks-lS11TIaY 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!

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.

The old school larger scale version of this is called "zebra strips", used for connecting lcds to rigid PCBs.

I learn so much from your videos, as a practicing engineer I always go "Oh, that's how it works."

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

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.

holy! This visualization with the gel and the bearing balls was so simple yet amazing. Really enjoying your videos!

That sponser integration was smooth like a silka.

I'm an EE and I've used ACF hot-bar bonding many times, but I've never seen images like these - great stuff.

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 <3

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!

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!

The demo you did alone was worth watching this video for. It explained everything perfectly. Crushed it dude.

everytime you post, whether its the main topic or not, i learn something i previous thought impossible has already been solved

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.

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.

The work you do is just incredible man! Thank you so much!

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.

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