What is a heat gun?

What exactly is a heat gun? Hot air rework? It’s easy. You merely heat all the pins of an integrated
circuit at the same time to remove or reposition them. A traditional welding iron can’t do this, but
a hot air station can.

The design of a rework station is simple. Its function is to deliver air to the spray gun. Inside the
spray gun is a coil that reaches a very high temperature during operation and heats the air as it passes
through.

Most heat guns come with a relatively large nozzle, about 1 cm in diameter. This nozzle is attached to
the end of the heat gun to restrict the path that the air enters. By reducing the size of the nozzle,
the airflow can be accelerated.

This way, you have a sharp and extremely hot airflow source. This airflow source can heat a specific
area on the board, causing the pins to melt, and allowing you to melt multiple pin connections at once.

Now, let’s take a multi-pin SMD component as an example (such as the LM1117 variable voltage
regulator in a SOT-223 package). Suppose the component is damaged by reverse voltage or other reasons
and needs to be replaced with a new regulator.

First, the IC must be completely removed from the PCB. Many people believe that different-sized
components require different-sized nozzles. However, in reality, we usually install a basic round nozzle
on the device and do not change it during use. This way, the air will heat a larger area on the PCB.

https://highqualitypcb.com/blog/how-do-you-safely-use-a-heat-gun-for-rework/