There are a large number of tools that are used when repairing electronic devices such as:
Microscope helps to take a closer look at the phone's small components and welds for precise repairs.
Multimeter: A multimeter is a tool for measuring voltage, current, and resistance. It can be useful for diagnosing cell phone electrical problems.
Soldering iron or heat gun: If soldering repairs are required, a soldering iron, tin and flux will be needed to make the electrical connections.
Multicharger: it is a device that allows consumption tests and verify that the energy administered is correct and charge multiple cell phones or electronic devices at the same time.