How do you safely use a heat gun for rework?

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.

It takes 5-10 seconds to heat the component.

If you are working with an area smaller than 1 square inch, you can move the nozzle over the PCB until
the integrated circuit (IC) and PCB reach melting temperature (i.e. 425 degrees Fahrenheit). 

Use tweezers to nudge the component to see if it has come loose. If not, continue heating. Be sure to
keep the poking tool out of the way so it does not block airflow to the PCB. After about 5 to 10
seconds, the IC will come loose and you can pick it up with the tweezers and quickly move it to a very
hot PCB.

After removing the IC, the PCB should be allowed to cool down appropriately, then the pads should be
carefully cleaned with new welding, followed by a dewelding tool to remove the domed welding joints.

Dome one pad. Check all of the scratches from the whole of the knife technique.

Highqualitypcb SMT: Weld well and clean the pins, and you are done!