Before discussing desoldering SMDs, it is important to define the term. What is SMD? SMDs are surface-mounted devices. A typical SMD is mounted on a circuit board and soldered in place. To remove SMDs, they must be de-soldered.
How to Desolder SMD
Step 1: Collect the Right Equipment/Tools/Supplies
There are several ways of removing surface-mounted devices from a circuit board. However, the process is focused on safety. To desolder SMD safely, you need several tools/equipment. These include, but aren’t limited to a desoldering gun/solder wick/soldering iron, soldering flux, some low melt solder, and tweezers.
Step 2: Begin by Selecting the Appropriate Kit
Different projects will have different desoldering needs. For instance, small desoldering projects need a kit with flux and low melt solder. A fast chip (kit with lead-free or leaded solder) will work for a small desoldering project. The small amount of solder and flux will be adequate to complete a small project. However, larger packages will be needed to remove any flux and alloy if present and done regularly.
Step 3: Heat your Soldering Iron and Start Desoldering the SMD
Proceed by moving your soldering iron across the SMD leads until all solder is molten. Finish by removing your SMD chip using tweezers. The SMD should be lifted up carefully. If you follow the above steps to the letter and have the right supplies/tools, how to desolder SMD is as easy as it sounds.
Important Tips When Desoldering SMD
Besides having the right supplies and following the above steps, it helps to have a good soldering iron that you can work with comfortably. Ideally, it should be one that you are familiar with or have used many times before.
Desoldering SMDs doesn’t require advanced soldering techniques. If you are a beginner in soldering, you can try some quick soldering before attempting to desolder. It also helps to know the do’s and don’ts of desoldering. For instance, to avoid damaging neighboring components on your circuit board, you should handle your hot soldering iron with care.
FAQs on How to Desolder SMD and Related Desoldering Tasks
Why Should I Desolder SMD?
Desoldering is important when repairing or replacing soldered components on circuit boards. If something in your electrical circuit isn’t working properly, desoldering components can help as part of repair work (removing bad components and installing new ones). Desoldering is also common when salvaging components in a circuit board.
Why Do I Need Flux to Desolder SMD?
Flux helps to keep the solder flowing to wherever you need it to go. Flux also removes metal oxides that form on solder joints. What’s more, flux is critical for aiding heat transfer.
Which Flux Should I Use to Desolder?
No-clean flux and rosin flux are great desoldering fluxes. These fluxes stand out since they are great wetting agents. They also boost solder flow which is critical when desoldering.
What Type of Soldering Iron Should be Used to Desolder?
A typical simple 15-30 watt soldering iron can desolder perfectly. Non-adjustable soldering irons can also get the job done. However, you risk damaging components. Temperature adjustable irons are best placed for a safe desoldering job for obvious reasons.
What is the Perfect Temperature to Desolder SMD?
It depends! However, a temperature of 330-360 degrees Celsius or (630-680 degrees Fahrenheit) is ideal to desolder most SMDs. The right temperature is important to preserve the components (avoid overheating). When desoldering, the goal is using the lowest amount of heat required. Desoldering quickly is also important to prevent overheating.
Generally, several factors will dictate the perfect temperature to desolder. The most notable include the size of the SMD being desoldered and type of solder used to fix the component in place. Lead solder requires lower temperature than lead-free solder. A larger component may require a higher temperature to heat up properly.
If there are ground/power or thermal planes in place, they will increase heat demands. The no. Of PCB layers will also increase temperature needs. For a typical desoldering task, general temperature recommendations will work. However, you should research how to desolder SMD safely based on the component in question.