SMD Soldering – The Lazy Engineers Way
If you ask any hacker about his late night nightmares he would tell you about soldering fine pitch components. This is why most hackers still prefer to use bulky through-hole components over their SMD counterparts. Since most 32-bit micro-controllers (if not all) and all of the FPGAs now come in such packages, the average hacker is left aside scared of even trying to solder such components. His only option is to go and buy a pre-assembled bulky board to use in his project.
This new technique by the Lazy Engineers aims to change that. The best part of this approach is that it does not require any practice nor any special tools. Just head over to your local electronic shop, grab any solder flux you can find, heat up your soldering iron to any degree you usually do and you are set.
The principal behind this procedure is fairly simple. Your PCB comes with a HASL finish. For those not familiar with what that means, it is the silver part that covers the PCB pads before any soldering is done. This silver part is actually called Hot Air Solder Level, this is the predominant surface finish used in PCB manufacturing. I am not going to bore you with details about PCB surface finish but the main point is that your PCB pads are already covered in solder so there is no need to add any extra. In order to make the soldering easier and protect from corrosion, the flux is used. When everything is put together, the heat from the soldering iron will melt the HASL finish on the PCB, the flux will protect and aid in forming the bond between the HASL and the chip pads, the soldering process is done and the component pads are now soldered in place hassle free.
As we can see from the video the method is extremely easy and straight forward. First a tiny bit of flux is applied underneath the component, this will make the component sticky so it will be much easier to align the pins to the corresponding pads. Tweezers are used to help with the alignment. Once you are satisfied with the alignment, take the flux you have and spread it over the pins. There is no fear of putting too much because in its unheated state, the flux is non-corrosive and non-conductive and thus will not affect the circuitry. So be generous on the flux. The final step is to hold the component down with one hand and apply heat using the soldering iron with the other. That is it you are done. It might be important to mention that this method can be used with different types of SMD components. The one we see in the video is a QFP package with 208pin and 0.5mm pitch, but this can very easily be replicated with QFN, SOIC and any other package.
If you are not satisfied with the result, or you think some pins need more soldering you can pass your soldering iron again on those specific pins until satisfied. You can always put a tiny bit of solder on the soldering iron tip and pass it again for ensuring a reliable connectivity.
This technique comes with extensive amount of rosin flux fumes, so what are you waiting for? Go and try it yourself.