Beginners’ Guide To Surface Mount Soldering

Surface Mount Soldering is a commonly used technique in the Surface Mount Technology (SMT) assembly process.  Instead of components with leads inserted into holes as with “Through Hole” soldering, in this technique, components are attached to the pads on the board surface.

Among all the SMT processes, soldering requires the most extreme focus when being performed, which is why it is a vital technique that beginners should learn in soldering 101.

On that note, here are four steps to surface mount soldering for beginners:  

1. Prepare Workspace

First, make sure to have your essential equipment with you like the following:

• Soldering iron with a fine tip
• Brass or damp sponge
• Flux-cored solder wire preferably 0.4 to 0.6 mm
• Tweezers
• Desoldering braid (Also called Desoldering Wick)
• Desk lamp
• Helping hands/vice with a magnifier

2. Prep Soldering Iron

Tinning the soldering iron before use makes soldering easier and improves thermal conductivity.  Most important of all, it protects the soldering tip from corrosion.  To begin tinning your soldering iron, you need to turn it on and let it heat up to approximately 350°C or 655°F.  Afterward, add solder to the tip of your soldering iron until a small blob forms around it.  Then, rub the tip against the sponge (brass or wet) to remove the blob of solder.  Repeat several times until you have a shiny soldering tip.

3. Start Soldering

Clip the board with helping hands/vice.  Then, adjust the magnifier until the solder pads are clear.  With your soldering iron, heat the pads for the component you want to attach.  Then, apply a small amount of solder onto one or two opposing corner pads of your component.  Then, grab the component with tweezers and carefully align its pins with the soldered pads.

While keeping the pins correctly aligned, use the soldering iron with your other hand to heat one of the pins, and reflow the solder onto the pad to tack the component into place.  Repeat the process if you added solder to the opposite corner pad of the component.   Then, solder a pin by heating the pin and pad with the soldering iron and feeding solder wire directly to the pin and pad.  Repeat the process on the remaining pins, making sure not to bridge them with excess solder.

4. Desolder Bridged Pins

If you accidentally apply too much solder, this will cause adjacent pins to bridge, which may lead to some very nasty results like a short circuit or a component burning up.  This is why if you accidentally bridge some pins together, you need to desolder, then solder them again.

The first thing you need to do is to take a small piece of desoldering braid.  Then with a tweezer, hold the braid against the joint that needs desoldering.  Afterward, take your soldering iron with your other hand, then touch its tip to the braid.  As the solder melts, the desoldering braid will absorb the solder and draw it away from the joint.  After making sure that the bridging has been totally removed, you can now try resoldering the pins.

Conclusion

Surface Mount Technology is an excellent skill for building electronic devices, especially as SMT equipment’s market is projected to grow over 2.7 Billion USD by the year 2025.

Though it is not that difficult to learn, it requires the right tools and great patience to master it.  EMS companies with inexperienced or new soldering operators must maximize their training investment by having their key manufacturing staff learn and apply the technical aspects of soldering 101.

Take your assembly staff’s soldering workmanship to the next level.  Enroll them in soldering for beginners courses to hone their skills as they focus on lessons that will directly affect product quality.

Contact us for more information at sharonm@blackfox.com.