by Janne Isotalo - published 2021-03-06
An article about basic SMD soldering methods
SMD soldering can easily seem intimidating if you have only soldered through-hole components. However, the technique for soldering SMDs is pretty similar. With the proper tools, SMD soldering can be even faster than working with the through-hole components.
From the synth DIY prototyping -point of view there are differences in the workflow. EG. for prototype modifications or design mistakes, it's harder to incorporate jumper wires, extra components, etc. On the other hand, for the finished product, you have more benefits than limitations. These include things like smaller components that enable more compact circuits with lower resistance and inductance, better EMC compatibility, more beneficial utilization of multi-layer PCBs, cheaper component prices, just to name a few. Also, the harsh reality for the through-hole fans is that some of the newer components are only available as an SMD version.
In this article, we will show you two common techniques for soldering SMD components.
Let's get to it!
The first presented method for SMD soldering utilizes soldering iron, flux pen, small diameter solder wire, and tweezers. The "no-clean" -type solder and flux in the video are:
The advantage of the leaded solder (Sn63/Pb37) for hobbyists is the lower melting temperature and better flow compared to the lead-free solder. Since lead is poisonous, do remember to take care of proper ventilation for your own health.
When switching from through-hole to SMDs, it's common to make the mistake of heating the pad too much which eventually causes the pad to lift off completely. This is not something you want to experience and fixing the PCB afterward can be troublesome. To make sure this doesn't happen, use temperature around 600-650F or 320-360C for your soldering iron. Also, you are only asking for trouble if you are not using flux. Flux is your new best friend!
The second presented method is the solder paste and hot air -technique. The solder paste needs to be applied to the pads and it will function as both flux and solder. The solder paste used in the video is:
Like many tools, the hot air rework products range from cheap to highly expensive. If you are searching for a super low-cost solution for trying this technique out, check out those ridiculously cheap Chinese 858D clones. With this solder paste, the temperature for the hot air was set to +330C.
For building multiple SMD PCBs simultaneously, there are more advanced methods like using stencils and reflow ovens that you might want to incorporate into your workflow. Also, since the SMDs can be extremely tiny in size, it's an excellent idea to invest in an optical professional-level stereo microscope. It's much more important to see than to have steady hands.
We truly hope that these presentations gave you enough encouragement to try the techniques yourself!