When working with or building printed circuit boards, there is a lot of room for errors to be made. Whether you're relying on machines to do the building for you or building by hand, solder can often have a mind of its own. Sometimes the person doing the building (or the person programming the machine that does the building) can make a mistake. Other times, during reflow, the solder or components on the PCB can react in ways that are not desirable. Have no fear though, there are ways to remedy this! The SparkFun Hot-air rework station is one such solution. Hot-air stations or guns are very useful tools and are essential for any electronics workbench.
What's it Good For
Hot-air rework stations can be very handy. As mentioned above, they are a crucial tool when it comes to reworking a board. The term rework just means you are refinishing or repairing an already reflowed board, and it is a term commonly used in the electronics world. Just think of it as doing any work to the board that wasn't involved in the actual production process. Here are some common rework scenarios:
Polarized parts that have been placed incorrectly (backwards, shifted x degrees off). These include ICs, diodes, some capacitors, connectors, etc.
Tombstone parts. This is when a part (usually a resistor or capacitor) reflows only on one side. The part usually sticks strait up resembling a tombstone.
Cold joints. This is similar to a tombstone except the parts might not be sticking strait up, making it harder to see the connection that is not being made.
Removing defective parts. Sometimes, during the IC manufacturing process, errors can arise and go unnoticed. These ICs are then placed on perfectly good PCBs. Hot-air is great for replacing these bad parts.
Missing components. The smaller the component, the easier it is for it to disappear. This can happen before or during reflow, resulting in a spot where something should be, but isn't. Hot-airing a new part in its place is a snap with this rework station.
Solder jumpers. If too much solder or solder paste is used, the result can be jumpers on one or more of your IC's legs. Hot-air can sometimes be used in conjunction with a flux pen to remove these pesky buggers.
Rework isn't the only thing a hot-air rework station is good for. Other uses include:
Salvaging electronic components from old PCBs.
Shrinking heat-shrink onto wires.
With the correct settings, hot-air can be used to heat up and bend certain plastics.
They can also be used to heat up hot glue to remove or reposition items that were glued incorrectly.
How to Use it
We're going to let our pal Dave Stillman show us how to use our Sparkfun Hot-air Rework Station properly.
Follow the simple rules Dave laid out in the video, and you'll have no trouble reworking the toughest of goof-ups.
Choose the appropriate tip for the job.
Set the temp and air-flow to the appropriate settings (slightly higher than the melting point of the solder, and not too much air to blow your parts away).
Wait for the hot-air station to warm up before using it.
Do not hot air on surfaces you don't want to get ruined. Having a piece of scrap wood or something similar to hot-air on is highly recommended.
Third hands or other vice grips help tremendously. Remember, heat dissipation can make rework take a lot longer.
If you see smoke, warping or black goo coming from your board, turn your heat setting down.
Use tweezers to move or nudge parts while reworking. Hot-air is, well, hot.
Wash your board with alcohol when you're finished to remove flux, which can cause corrosion over time.
Allow the station to cool down when finished.
If you have any questions or comments, please feel free to drop them in the comments box below. Happy reworking! And, remember, don't do what Donny Don't does.