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Electric Soldering Iron: The "Circuit Welding Tool" in Mobile Phone Repair

Created on 07.10

Electric Soldering Iron: The "Circuit Welding Tool" in Mobile Phone Repair

In the precision operations of mobile phone repair, the electric soldering iron is a core tool for handling motherboard component welding and circuit repair. It is like a "miniature welding torch" in the hands of repair technicians, capable of melting solder through controllable high temperatures to achieve precise connections between electronic components and circuit boards. Whether replacing damaged resistors, capacitors, or repairing broken solder joints, the electric soldering iron is indispensable.

I. Basic Understanding of Electric Soldering Irons

An electric soldering iron is a tool that uses electric current to heat a metal tip, melting solder for welding. In mobile phone repair scenarios, due to the small and precise components on mobile phone motherboards (such as chip pins with spacing measured in millimeters or even microns), the electric soldering iron requires extremely high temperature control and tip precision, and must be used with specialized accessories for fine operations.

Structurally, an electric soldering iron mainly consists of a soldering tip (the metal part that directly contacts the solder joint, conducting heat), a heating core (the core component that generates heat through electric current), a handle (heat-insulating and non-slip for easy gripping), and a power cord/temperature control device (components for adjusting temperature). Among these, the shape and material of the soldering tip directly affect the welding effect, making it the "soul component" of the electric soldering iron.

II. Common Types of Electric Soldering Irons for Mobile Phone Repair

Based on temperature control methods and applicable scenarios, electric soldering irons commonly used in mobile phone repair can be divided into the following categories:

(1) Constant Temperature Electric Soldering Iron

This is the mainstream choice for mobile phone repair. It uses a built-in temperature control chip to stabilize the temperature at a set value (usually adjustable from 200-450°C), avoiding damage to plastic components or precision chips on the motherboard due to excessive temperature. Its advantage lies in small temperature fluctuations, making it suitable for soldering small surface-mounted components such as resistors, capacitors, and diodes, especially for novice operators.

(2) Adjustable Temperature Electric Soldering Iron

Temperature is adjusted via a manual knob. Although its temperature control accuracy is slightly lower than that of constant temperature models, it is cheaper, making it suitable for cost-sensitive or occasional repair scenarios. When in use, experience is needed to judge whether the temperature is appropriate (e.g., by observing the melting speed of the solder) to avoid damaging components due to excessive temperature.

(3) Hot Air Gun + Electric Soldering Iron Combination Set

The hot air gun heats large-area solder joints (such as BGA packaged chips) with hot air, while the electric soldering iron handles detailed welding. This combination is suitable for removing and installing large chips on the motherboard. In mobile phone repair, when faced with complex operations such as replacing the CPU or baseband chip, such combined tools can significantly improve efficiency.

III. Core Roles of Electric Soldering Irons in Mobile Phone Repair

(1) Component Replacement: Repairing Damaged Parts

If small components on the mobile phone motherboard, such as resistors, capacitors, and inductors, are damaged due to short circuits or aging, the electric soldering iron is needed to remove them from the circuit board and solder new components. For example, when the protective resistor in the charging circuit burns out, the soldering iron is used to melt the solder joints to remove the damaged part, and then the new resistor is aligned with the pads and soldered in place to ensure the circuit is conducting.

(2) Solder Joint Repair: Solving Poor Contact

After long-term use of a mobile phone, solder joints may develop cold solder (solder joints that appear connected but are actually poorly contacted) due to oxidation or vibration, leading to functional failures (such as screen flickering or signal interruption). In such cases, the electric soldering iron is used to reheat the solder joints, allowing the solder to melt and form a firm connection, restoring smooth circuit operation.

(3) Wire Jumping: Repairing Broken Circuits

If the printed circuit on the motherboard is broken due to dropping or corrosion (such as broken circuits near the cable interface), the electric soldering iron can be used with fine wires for "wire jumping" repair—soldering the two ends of the wire to the two ends of the broken circuit respectively, bypassing the damaged part, and rebuilding the circuit path.