Tools for Removing an IC With a Hot Air Rework Station
Solder rework requires a few tools above and beyond a basic soldering setup. For larger chips, you might need the following electronics equipment:
A hot air solder rework station (adjustable temperature and airflow controls are essential) Solder wick Solder paste (for resoldering) Solder flux A soldering iron (with an adjustable temperature control) Tweezers
The following tools aren’t necessary, but these can make solder rework easier:
Hot air rework nozzle attachments (specific to the chips that will be removed) Chip-Quik A hot plate A stereomicroscope
Prepping for Resoldering
For a component to be soldered onto the same pads as a previous component, you must carefully prepare the site for soldering. Often, a sizable amount of solder remains on the PCB pads, which keeps the IC raised and prevents the pins from properly connecting. If the IC has a bottom pad in the center, the solder there can raise the IC or create hard-to-fix solder bridges if it gets pushed out when the IC is pressed to the surface. The pads can be cleaned up and leveled quickly by passing a solder-free soldering iron over the pads and removing the excess solder.
How to Use a Rework Station for PCB Repair
There are a couple of ways to remove an IC quickly using a hot air rework station. The basic technique is to apply hot air to the component using a circular motion so that the solder on the components melts at about the same time. Once the solder is melted, remove the component with a pair of tweezers. Another technique, which is especially useful for larger ICs, is to use Chip-Quik. This very-low-temperature solder melts at a lower temperature than standard solder. When melted with standard solder, it stays liquid for several seconds, which provides plenty of time to remove the IC. Another technique to remove an IC begins with physically clipping any pins the component has that are sticking out of it. Clipping all the pins allows the IC to be removed. You can use either a soldering iron or hot air to remove the remains of the pins.
Dangers of Solder Rework
When the hot air nozzle is held stationary for a long time to heat up a larger pin or pad, the PCB may heat up too much and start to delaminate. The best way to avoid this is to heat up components slowly so that the board around it has more time to adjust to the temperature change (or heat up a larger area of the board with a circular motion). Heating a PCB rapidly is like dropping an ice cube into a warm glass of water, so avoid rapid thermal stresses when possible.
