UPMSP High School Mobile-Phone Repair - Code 980 key terms

A sudden flow of static electricity between a charged body and a sensitive component. It can destroy or weaken chips inside a phone without any visible damage, so repairers use grounding and antistatic packaging.

A band worn on the wrist, connected by a wire through a resistor to a known earth point, that slowly drains static charge from the technician's body so it cannot damage circuit boards.

A conductive or dissipative work surface placed on the bench and earthed, on which boards and components are handled so that static charge is spread away safely instead of passing through the electronics.

The handling rules for lithium-ion cells: never puncture, crush or short them, do not heat them, store at moderate charge, and isolate any cell that swells, because a damaged cell can catch fire or vent hot gas.

A condition where a lithium-ion cell expands because of gas build-up from ageing, overcharging or damage. A swollen battery must be removed carefully and never charged or pressed back into a phone.

An unintended low-resistance path between two points that should be at different voltages. In phones it causes excessive current, heat, drained batteries or a dead rail, and is found by measuring resistance with a multimeter.

A component, such as a resistor, capacitor or IC, that is soldered directly onto pads on the board surface rather than having leads through holes. Almost all modern phone parts are SMD.

A soldering method in which solder paste is applied to pads, parts are placed on it, and controlled heat melts the paste so the joints form without the iron touching each joint individually.

A mixture of fine solder powder and flux. It is stencilled onto pads, holds components in place while sticky, and melts into a joint when heated, making it the standard material for reflow work on phone boards.

A chemical applied during soldering that removes oxide from metal surfaces and helps molten solder flow and wet the joint. Excess flux must be cleaned off because some types are corrosive or conductive.

A dull, grainy, poorly bonded joint caused by too little heat, movement during cooling, or dirty surfaces. It looks rough instead of shiny and causes intermittent faults that often return after the phone warms up.

A tool that blows temperature-controlled air through a nozzle to melt solder on a small area. It is used to lift SMD chips and connectors from phone boards without touching them with an iron.

An instrument that measures voltage, resistance and current, and often continuity and diode drop. In phone repair it is used to check battery voltage, test fuses and rails, and trace short circuits on the board.

A check made with a meter in continuity or low-resistance mode to confirm that two points are electrically joined. It is used to verify tracks, fuses, connectors and switches without applying power.

An adjustable supply that gives a steady, current-limited DC voltage to a phone under test. It replaces the battery during diagnosis, and the current drawn shows whether the phone is dead, shorted or booting.

A diagnostic method where a phone is powered from a current-limited bench supply and the current reading is observed. Very high current suggests a short, zero current suggests an open circuit, and a pulsing reading suggests boot attempts.

A fault in which the phone restarts repeatedly before reaching the home screen, usually because of corrupted firmware, a failing storage chip, or a hardware fault that makes the system crash during startup.

The permanent software stored in the phone's flash memory that controls the hardware and starts the operating system. It includes the bootloader, modem software and system image, and is replaced by flashing.

Writing a firmware image into the phone's flash memory using a computer and service software. It is used to repair software faults, but erases user data and can brick the phone if the wrong file is used.

A small program that runs first when the phone powers on. It checks basic hardware, decides whether to start the main system, and allows a computer to load firmware in download or fastboot mode.

A Google account lock that activates after a factory reset on many Android phones. The phone asks for the previously signed-in account, so a repairer must confirm ownership before resetting a customer's device.

Erasing all user data and settings and returning the phone to its out-of-box state. It is a last step for software faults and must be done only after the customer's data is backed up and consent is recorded.

A single chip that contains the processor, graphics unit, memory controller and other blocks. In a phone it is the main computing device, and faults in it usually mean board-level replacement rather than part swapping.

A chip that converts battery voltage into the several regulated supplies the phone needs and controls charging and power sequencing. A faulty PMIC commonly causes no-boot, no-charge or overheating symptoms.

The chip that regulates current from the charger into the battery, protects against overvoltage and overcurrent, and reports charging status to the processor. Its failure causes slow, absent or false charging.

The non-volatile flash memory that holds the operating system and user data. eMMC and the faster UFS are soldered to the board, so failure means board-level repair and usually loss of the data on it.

A thin, flat cable with printed conductors that links parts such as the screen, camera or charging board to the main board. It is fragile and often fails at creases or connector ends, causing intermittent faults.

A small multi-pin connector that joins two circuit boards or a board and a flex cable. Its fine pins are easily bent or contaminated, so it is checked for alignment and cleaned before blaming other parts.

The combined screen and touch panel, often bonded with a front glass. On most modern phones the whole assembly is replaced as one unit because the layers are glued together.

The socket where the charger cable plugs in. It carries power and data, collects dust and suffers bent pins, and is a common cause of no-charge or no-data faults that is fixed by reballing or replacing it.

Removing old solder from the pads of a BGA chip, placing new solder balls in a stencil, and reflowing them so the chip can be refitted. It is done when a chip is replaced or resoldered to the board.

A chip package whose connections are rows of tiny solder balls underneath instead of pins at the sides. BGAs are common in phones and need hot air or infrared heating plus alignment to remove and refit.

The unique 15-digit identity number of a mobile handset, stored in the phone and reported to the network. Repairers must check it against the device label and never alter it, because changing it is illegal in most countries.

A small smart card supplied by the network operator that identifies the subscriber and stores contacts and operator data. Its contacts and the phone's SIM reader are common causes of no-service faults.

The international mobile subscriber identity held inside the SIM. The network uses it to identify the subscriber, while the handset itself is identified by the IMEI, so the two numbers serve different purposes.

A software restriction that makes a phone accept only SIM cards from one operator. It is removed by the operator or by an official unlock code, and customers should be told the legal route rather than unofficial ones.

A written record made when a device is accepted, listing customer details, the reported fault, the phone's condition and IMEI, accessories received and the agreed estimate. It protects both shop and customer in disputes.

The stated conditions under which a repair or replacement part will be redone free of charge, including the period, what is excluded such as liquid damage or physical breakage, and how the customer must claim.

The sales or repair volume at which total income equals total costs, so the shop makes neither profit nor loss. Knowing it helps an owner set prices and judge whether rent and wages are affordable.

The difference between the selling price of a repair or part and its direct cost, usually expressed as a percentage. It shows how much each job contributes towards rent, wages and profit.

The movement of money into and out of the business over time. A shop can be profitable yet fail if cash is tied up in slow-moving stock or unpaid customer credit, so flow is tracked separately from profit.