If your phone's screen stops responding, the common fix is to replace it. But screens are pretty pricey these days. In this guide, we'll show you an alternative way to solve the problem without replacing the whole screen assembly. Specifically, we'll focus on fixing touch - related problems on the iPhone 12 Pro Max. Before we start any repairs, we've already ruled out other possible causes and made sure that the touch - related parts and circuits are in good shape.
1. Disconnect the Flex Cable and Remove the Screen
To avoid ESD (Electrostatic Discharge) damage, use a plastic spudger to carefully disconnect the flex cable. This step helps in safely removing the screen from the phone's body.
2. Separate the Glass
Set the Separator Temperature
First, set the separator's temperature to 100℃. Once it reaches 100℃, place the screen on the separator and carefully detach the earpiece speaker module. This module is usually located at the top of the screen.
Remove the Bezel Frame
Before separating the glass, we need to get rid of the bezel frame. Apply some alcohol along the bezel's edge. This helps in softening the adhesive. Then, use a tool to slice through the adhesive that seals the top edge of the bezel. After that, use cutting nippers to carefully cut open the top bezel.
Slowly Separate the Bezel
Gradually separate the bezel frame from the screen. While doing this, keep the screen heated at 100℃. This makes the separation process easier as the heat softens the remaining adhesive.
Start Separating the OLED
Find an entry point at the bottom corner of the screen. Use a cutting wire to start separating the OLED layer from the bottom layer of the glass. Go slowly and steadily to avoid damaging the screen.
Remove the Glass Cover
Continue using the cutting wire to completely remove the glass cover from the OLED layer.
3. Clean the OCA Adhesive
Apply and Remove the OCA Tape
Apply specialized OCA removing tape to the OLED surface. Then, apply a bit of heat. This heat makes the tape stick firmly to the OCA adhesive. Peel off the tape, and it will take a large part of the OCA adhesive with it.
Clean Residual Adhesive
For any remaining OCA adhesive, use an electric glue removing tool along with N - hexane. Be careful when using N - hexane as it's a chemical solvent. Make sure you're in a well - ventilated area.
4. Install a Tag - on Touch Screen Digitizer
Since the iPhone 12 Pro Max has an on - cell design where the touch and OLED are integrated, we can't replace the touch screen digitizer separately. So, we need to install a tag - on touch screen digitizer.
Apply OCA to the Digitizer
Get a suitable iPhone 12 Pro Max touch screen digitizer. Attach the OCA adhesive to the back of the digitizer. After that, place the digitizer into a bubble - removing machine. This machine helps in getting rid of any air bubbles between the OCA and the digitizer.
5. Touch Screen Lamination
Clean the OLED Again
Before laminating the screen, clean the OLED surface one more time to ensure there's no dust or residue.
Align the Glass and OLED
Use an aligning mold to precisely align the glass with the OLED. This step is crucial for proper screen functionality.
Lamination and Debubbling
Stick the screen to the Refox FM - 50 laminator. After the lamination process is complete, the screen needs to be debubbled. Leave the screen in the debubbling setup for about 15 minutes. You'll notice that the laminating and debubbling processes are successful.
6. Transplant the IC
Protect the Screen and Desolder the IC
To safeguard the screen from damage, apply high - temperature tape around the IC on the original touch flex cable before starting the operation. Then, use a vertical hot air gun set at 320℃ with an airflow of 2 to desolder the IC.
Prepare the Bonding Pads
Apply some solder paste flux and low - temperature solder paste to the bonding pads. Use a soldering iron at 380℃ to remove the old tin. Clean the pads with a PCB cleaner.
Form Solder Balls and Solder the IC
Once the bonding pads are clean, evenly apply a layer of solder paste to them. Use a hot air gun at 260℃ to form solder balls. Next, clean the bonding pads on the tag - on touch flex cable. Use a soldering iron at 380℃ with desoldering braid to remove any excess tin. Then, solder the IC to the new flex cable using a hot air gun at 280℃ with an airflow of 2.
7. Install the Screen Tag - on Flex Cable
Prepare the Bonding Pads and Solder
Remove the underfill adhesive on the bonding pads. Before soldering, carefully align the three pins. Then, use a hot air gun at 320℃ to solder them. Solder the other end of the flex cable with a soldering iron at 380℃. Soldering is the most challenging part of this whole process, and it's key to ensuring the touch function works well. After soldering, clean the residue flux with a PCB cleaner.
8. Reassemble and Test
Install the Bezel Frame
Apply the bezel adhesive and align the bezel with the display. Place the screen assembly into a press clamp and press the bezel firmly. Then, install the display back into the phone.
Finally, test the phone. Check if the touch screen is fully responsive and if the True Tone feature is working. If everything is working as it should, you've successfully fixed your iPhone 12 Pro Max's touch issue!
