I’ve recently gotten into SMD soldering and have been thrilled at how much easier it is than I imagined. However, there are some parts that are very difficult to solder because the solder pads are under the part. The obvious answer is reflow soldering, but I have no experience with it and it can be expensive and difficult to do. So this is my experiment in finding a cheap and easy way to do reflow soldering.
The normal reflow process is to create a stencil and then use it to spread solder paste onto the pads of the board. This requires an arduous process of creating the stencil and lining it up correctly with the board as well as buying expensive solder paste. So I wanted to see if I could do it without the paste, using regular solder. I used a soldering iron to put a small amount of solder on the pads I wanted to solder. The key here is a small amount. If you put a big bubble of solder on the pad, you won’t be able to set the part to solder flat and it will shift when the solder melts. If you get too much solder on the pads, use a desoldering braid to remove some of it. The picture below shows my board. I used several different amounts of solder on various pads to see the effect it would have. Even the ones with barely any solder secured the parts just fine so I’d recommend using as little as possible. 
The next step is to place your components. If any of them aren’t sitting flat then remove the extra solder and try again. 
Now comes the reflow part where you heat the board up. There are several different methods to do this including reflow ovens ranging from cheap toaster ovens to multi-thousand dollar machines. But since I don’t have any of these, I just used a hot plate with the board on top. Instead of immediately heating the board to a high temperature, I first heated it to an intermediate temperature and then increased it. I did this to prevent any thermal shock that might damage the board. I found the solder melted at around 560 degrees Fahrenheit.
Remove the board from heat carefully so that you don’t move any of the components and let it cool down. And there you go, a cheap and easy method of solder reflow using things you already have laying around.
The Wandering Engineer 