Image by Guillaume Boivin
DIY

Wreck-it Wednesday: LCD Teardown

A Mindtribe tradition was recently resurrected. Teardown Thursdays was sadly forgotten, lost in the hustle and bustle of growing our team. Luckily a voice spoke up, and now it has been replaced with Wreck-it Wednesdays.

Before you get hung up on our awkward attempt at alliteration, I think teardowns can be a fun and engaging way of sparking a young, inquisitive mind. If you know a kid who shows some interest in engineering or technology, what better way to foster that interest than to explore the design and construction of household objects. Before broken toys are sent to the landfill, or before dead electronics are tossed into the ever-growing pile of e-waste, take a screwdriver to them. Open them up and learn about how they operate, or even why they are broken. It’s the perfect opportunity to ensure the next generation of engineers gets an early start. Of course, it should always be done under the careful supervision of an adult, which is why we have senior engineers to watch over our associate engineers.

Getting back to Wreck-it Wednesdays, our first dissection involved a dead LCD display donated by Sami. We all spend hours each day staring at monitors, but very few of us had ever seen the inside of one. As the room filled with engineers from all the disciplines, we were all intrigued by different parts of the LCD. The EE team looked at the power supply board, and the tiny display driving components around the LCD. The ME team looked at the plastic housing and guessed as to how the markings related to the injection molding process. IMG_9690 Although we mostly knew the general way in which LCD monitors work, tearing one open made us realize that none of us knew the detailed specifics of how the 1s and 0s of our computer generated images actually get turned into colors on the display. Luckily the internet is also filled with smart people. A great Youtube channel that I recommend checking out belongs to the Engineer Guy. He has a great video of an LCD teardown that taught us a few things (https://www.youtube.com/watch?v=jiejNAUwcQ8). Part of our exploration led us to the microscopes in the EE Lab. Looking at the different filters and sheets from the display under magnification made for some cool discoveries and some even cooler pictures. Looking at everything close up made it more clear how the RGB filtering occurs in an LCD. RGB_scope The matrix of white dots on the light pipe that creates even illumination was also interesting. It was great to see how the dot spacing on the light pipe stays the same, but the sizes of the dots increase as they get further from the edges, accounting for the distance from the light source and create the even light. LightPipe_scope But perhaps the most confusing part of the teardown led us to a question that even the Engineer Guy didn’t address. What were these zigzag traces that led from the mux to the pixels? They are only obvious under the microscope, and although they were different thicknesses at times, they weren’t different lengths. ZigZag_scope Curiosity led me back to the internet, but this time, Google was less helpful. I did find out that some IPS type LCDs have zigzag electrodes. The reason for that wasn’t immediately clear, but it might have to do with improving motion blur, reducing color shift, or for ease of manufacture. I found a patent that had an informative graphic, but I couldn’t find a satisfying answer for why these traces were zigzags. LCD stuff

This will have to be one of those questions that lingers in the back of my mind until I get a chance to ask an LCD expert. Hopefully that day will be soon, but until then, there are more things to wreck and teardown.