Practical: Changing Phone Screen – JSS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

Changing a phone screen is the repair in which a technician removes a cracked display and fits a new one.

Behavioural objectives

1. Name the main tools used to change a phone screen and state the use of each.
2. List the steps of a screen replacement in the correct order.
3. State why the phone must be switched off and the battery disconnected before work starts.
4. Explain why the new screen is tested before it is glued down.
5. Describe the common mistakes that damage a phone during screen repair.

What is a phone screen and why does it break?

The screen is the display part of a GSM phone, and it is the most fragile part.

• Thin glass: the top layer is thin glass, so a hard fall usually cracks or shatters it.
• Display layers: under the glass are tiny parts that make the picture, and they also break easily.
• Touch layer: the glass also senses your finger, so a damaged screen may show lines or stop responding.
• Delicate work: replacing a screen is like a small “surgery” and needs patience and a steady hand.

What are the types of phone screen?

There are two common types of phone screen: LCD and OLED.

• LCD (Liquid Crystal Display): uses a light at the back (backlight) that shines through tiny crystals to form the picture.
• OLED (Organic Light-Emitting Diode): each tiny dot of the screen makes its own light, so no backlight is needed.

What tools are needed to change a phone screen?

A technician needs a precision toolkit, because a kitchen knife or a big screwdriver will damage the phone.

• Small screwdrivers: very tiny Pentalobe (five-lobed) or Phillips (cross-shaped) heads to match the phone’s screws.
• Plastic spudger (pry tool): a flat plastic tool used to pop the phone open without scratching it.
• Suction cup: sticks to the glass so the screen can be lifted safely.
• Heat gun (or hairdryer): warms the strong glue that holds the screen to the frame.
• Tweezers: pick up tiny screws that are too small for the fingers.
• Pin or SIM ejector: opens the SIM tray.
• New screen and phone glue: the replacement part and an adhesive such as B-7000.

What safety rules must be followed?

Safety rules protect both the technician and the phone.

• Switch off first: never work on a phone while it is on.
• Mind the heat: if the phone is too hot to touch, too much heat is being used.
• Beware of glass: broken glass can cut the fingers, so work slowly and keep small pieces off the table.
• Keep hands clean: oily hands can leave marks on parts, and static electricity can damage chips.
• Keep screws in order: place them on a tray in the order removed.

What are the steps for changing a phone screen?

A screen replacement has seven steps, done in the order below.

1. Power off and prepare.
   • Turn the phone off completely.
   • Remove the SIM tray with a pin.
   • If the tray is left inside, it can snap while the phone is being opened.
2. Heat the glue.
   • Most modern phones are glued shut to keep out dust and water.
   • Move the heat gun gently around the edges of the screen.
   • This softens the adhesive (glue).
3. Open the case.
   • Stick the suction cup to the screen and pull up gently.
   • Slide the plastic pry tool into the gap.
   • Move the tool around the edges, like opening a tin of biscuits.
4. Disconnect the battery.
   • Unscrew the metal plate that covers the battery connector.
   • Pop the battery connector off gently with the plastic tool.
   • This stops electrical sparks and protects the motherboard.
5. Disconnect the screen cable.
   • Do not pull the screen away yet.
   • A thin ribbon cable (the flex cable) joins the screen to the motherboard.
   • Unscrew the metal plate over its connector, then pop the cable off gently with the plastic tool.
6. Test the new screen.
   • Plug the new screen’s cable into the motherboard and reconnect the battery.
   • Turn the phone on and check that touch works everywhere on the screen.
   • Check that the colours are bright and there are no lines.
   • If it works, turn the phone off and disconnect the battery again before sealing.
7. Clean and seal.
   • Clean the old glue and glass bits from the phone’s frame.
   • Reconnect the battery and the screen cable, then replace the metal plates and screws.
   • Apply new phone glue (such as B-7000) around the edges.
   • Press the new screen down and hold it with small rubber bands until the glue dries, about an hour.

What are the common mistakes in screen repair?

Common mistakes are errors that can ruin the phone or the new screen.

• Tearing the ribbon cable: these cables are as thin as paper and snap if pulled too hard, which ruins the screen.
• Mixing up screws: phone screws come in different sizes, and a long screw in a short hole can press on and damage the motherboard.
• Losing screws: tiny screws roll away easily, so keep them on a tray.
• Static and oily fingers: touching the internal chips can damage them, so handle parts by the edges.
• Too much heat: it can harm the screen and the parts under it.
• Gluing before testing: a faulty new screen then has to be pulled off again.

What is the repair checklist?

The checklist below gives each step, the action and the reason for it.

Class activity

1. Tool identification: the teacher holds up the spudger, a Pentalobe driver and tweezers. Students name each tool and describe its use.
2. Observation: watch a video or live demonstration of a screen teardown. Pay close attention to how thin the connector cables are.

Teacher’s note

• Warranty: opening a phone usually voids the warranty (the manufacturer’s promise to fix it for free).
• Practice phones: students should not practise on their parents’ working phones.

Evaluation

1. Why do we use heat before opening a modern smartphone?
2. What is the name of the thin cable that connects the screen to the motherboard?
3. Why is it important to test the new screen before gluing it down?
4. What could happen if you use a long screw in a hole meant for a short screw?
5. Why must the battery be disconnected before the screen cable is removed?

Assignment

Write the seven steps of changing a phone screen in order, and give one reason for each step.