Not a Fan of Bonded Touch Screens

After replacing the touchscreen module of a Pixel 3a phone, I’ve decided I’m not a fan of a modern evolution in their design. A touchscreen module has two major components: an output module to show information to the user (display) and input module to detect location of user’s fingers (digitizer). While they are both advanced glass technologies, they are made with very different manufacturing processes. Thus they are built on two separate pieces of glass, and assembled together into a touchscreen module. The straightforward way to do this is to place one on top of the other, like this Amazon Fire tablet I took apart. In that case, I found the display was intact and it was only the digitizer glass that had cracked.

There were some downsides to this approach. Aesthetically, it means it’s possible for dust and dirt to get between the layers, where it is very difficult to clean. These surfaces also mean there’s more chance for reflections, and two separate pieces of glass meant the user’s finger is a few millimeters away from the visual interface they are interacting with. Mechanically, as separate pieces they are each on their own resisting mechanical stresses.

To address these problems, many newer touchscreen devices use an optically clear adhesive (usually a resin formulated for the task) to bond the touch digitizer to the display. Once bonded, there’s no way for dust and dirt to get in between those layers. The resin eliminates reflections between the two layers and visually connect the two layers. This help build the illusion that the user is directly manipulating onscreen objects with their finger by putting the display closer to the fingertip. And finally, bonding them together makes the module mechanically stronger as both layers work together to resist mechanical stresses. This is especially useful for phones using OLED displays, which are thinner (and more fragile) than backlit LCD displays.

But stronger touchscreens still have a limit and once exceeded, we’re back to the problem of a cracked screen. In the case of the Pixel 3a I just worked on, only the digitizer layer is cracked. The display layer is still intact and functioning. Unfortunately, due to the fact they are bonded, there’s no practical way to replace just the digitizer portion. So, the entire module has to be replaced. Trying to pull the digitizer glass away from the display glass stretches the resin and once released, we see bubbles between the two layers ruining optical clarity.

As expensive and wasteful as it is, the perfectly functional OLED display can only be thrown away. In comparison, cracked digitizer on a device without a bonded screen could be replaced independent of the display unit. One such high-volume repair is replacing Apple iPad touch digitizers. Amazon vendors sell digitizers for $20-$50 USD, depending on iPad generation. In comparison, as of this writing replacement Pixel 3a modules start at double that cost. This difference is even more stark when considering the fact an iPad has a much larger screen.

The bonded touchscreen module of a Pixel 3a is so expensive that, as of this writing, it actually isn’t economically sensible to replace the screen even at the lowest bidder unknown vendor option of $85. Because if we browse eBay we can find secondhand Pixel 3a for sale for as low as $50. If this keeps up, there’s a business opportunity for a phone chop shop: buy these secondhand Pixel 3a, disassemble them, and sell the components piecemeal. I don’t see any used/salvaged Pixel 3a touchscreen modules for sale at the moment, but maybe it’s a matter of time before they start popping up. But still, I hated throwing away this OLED screen

I understand the reasons why bonded touchscreen modules exist, but since they make repairs difficult, wasteful, and less economical, I am not a fan of this feature.

Pixel 3a Screen Replacement

I was very impressed by iFixit’s Pixel 3a Screen Replacement kit, but naturally I bought it for a reason. I have a Pixel 3a with a shattered screen I wanted to fix by following their instructions.

Well, “shattered” might be going a bit too far but it was definitely broken well beyond just “cracked”. Amazingly enough, the phone still ran in this state. As we can see here, the display works just fine. However, touch responsiveness isn’t great on account of all the cracks running throughout the screen. There are several scattered dead spots. Inconveniently, a few dead spots were where the keyboard would live which makes it a challenge to put in WiFi passwords and such. (* one workaround below)

I turned the screen off and chose a camera angle so my workbench light could highlight the damage.

Near the bottom of the screen, small bits are missing allowing us to see the phone internals within. Given this damage, I was amazed touch input still worked at all. My first order of business was to remove this impressively damaged screen. A suction cup was included in the iFixit kit to grab onto glass, but it could not get a good seal on this screen: too many cracks let in air and ruin the suction.

Backup plan: use tweezers to pick at little pieces of glass.

That was enough to open up an entry point for the Wankel rotor-shaped pick.

At certain locations, putting too much stress would damage the optically clear resin bonding the touch digitizer glass to the OLED screen. Bubbles would form, and the bonding is no longer optically clear. This would be a concern if I wanted to reuse this screen, but due to that same resin I could not.

It took me roughly half an hour of painstaking work to free the old screen from the adhesive holding it down all around the phone. Occasionally the “pain” is literal as small shards of glass stabbed into my hand. Fortunately, no blood was drawn.

Once removed and laid down as per iFixit guide, I could compare the original module with the new replacement. This is necessary because there may be small components that need transferring, and the list is not definitive because little accessories vary depending on supplier whim. In similar repairs, we frequently need to replace the speaker mesh. Fortunately my replacement module already has a mesh in place so I was spared that task. However, there’s a light gray piece of plastic surrounding the front-facing camera that I would have to transfer over.

After doing that comparison, I unplugged the old screen and plugged in the new one. I wanted to be sure the new screen will work before I roll up my sleeve for the tedious work of cleaning up.

If the new screen didn’t work, I didn’t want to waste my time on annoying tasks. Cleaning up remaining shards of glass, wipe up dirt, and my least favorite part of working with modern electronics: scraping off gummy bits of adhesive.

Once most of the adhesive was cleaned up (as much as I had patience for) I transferred this light gray piece of plastic camera surround. Then I followed the iFixit guide for applying custom-cut piece of new adhesive and installed the new screen in its home.

Left: a stack of plastic backings to protect adhesives and glass surfaces. Center: the old screen in one large and many small pieces. Right: the repaired phone with its shiny new intact screen!

I shall celebrate with a sticker from the iFixit repair kit. As much as I loved this success, I wished it didn’t have to be expensive as it was. I blame the design decision to bond touch digitizer and OLED display.


(*) One way to get an Android phone on WiFi when the touchscreen is too erratic to let us enter a WiFi password:

  1. Take another Android phone on the same WiFi network we want to get on.
  2. Tap its WiFi connection to reach “Network Details” screen.
  3. Tap “Share” to generate a QR code.
  4. Scan QR code from erratic phone.

iFixit Pixel 3a Screen Replacement Kit

Today’s post is an iFixit fan post. It is not paid or sponsored by iFixit, I’m just really really impressed by my latest purchase: the iFixit Pixel 3a screen replacement kit. I’ve been given a Google Pixel 3a cell phone with a shattered screen, and I thought I would try my hand at replacing its screen. iFixit’s replacement kit should mesh well with their screen replacement guide, which I will be using.

This is not my first phone repair. I’ve bought replacement parts from several Amazon & eBay vendors. I decided to upgrade for this project and I’m glad I did. None of those prior repair kits come anywhere close to the iFixit kit in quality and completeness.

My positive impressions started with the shipping box.

As soon as we open the box, we get an encouraging “You got this” on the first flap we see. I love it.

Inside the box are several smaller boxes. Two labeled “Repair Tools” and one “Repair Part”.

Inside these boxes are the replacement screen plus all the tools we’d need to replace it. Starting from the sticker pack on the left, we have:

And finally, the replacement screen module itself along with a custom cut sheet of adhesive. The latter is a premium luxury not always found in other products. Many Amazon/eBay vendors sell replacement screen modules with generic rectangular strips of adhesive we would have to cut to shape ourselves. Some didn’t include the adhesive at all! (If that should happen to you, iFixit can still help as they sell the custom-cut adhesive separately.)

At the time of this writing, iFixit charges a $7 premium for the full kit over just the screen module by itself., which is in turn only a few dollars more expensive than lowest bidder of the day. I decided to go for the full kit and I’m glad I did, these tools are well worth the price difference and gave me confidence I have everything I needed to tackle my screen replacement project.