[Music] Reflow soldering is the modern mechanism for assembling most printed circuit boards today um Reflow soldering enables mass production at a very rapid rate by allowing placement of the components to be separated from the actual soldering process in Reflow soldering the pads of the device of the printed circuit board are first covered with solder paste which is a mixture of tiny beads of of pure solder little spheres and solder flux this mixture is called solder paste solder paste is applied in a pattern using a stencil so that it leaves solder paste only where it's necessary to solder the terminal of a device now solder paste is sticky so that devices can be placed onto the paste and remain held there simply by sticking a little bit of viscosity with all the devices in place on the printed circuit board the board is placed in an oven where it's raised to a temperature above the melting point of the solder the solder then reflows onto the the terminals of the device and the board is then allowed to cool at that point all the devices have been attached simultaneously and the board is fully assembled now this makes it this process is somewhat different from how somebody would solder by hand when you're hand soldering you're treating one component individually and applying heat to each component at a time so the technique has to be a little bit different and since our soldering iron is a a very different tool from the Reflow oven we have to come up with an alternative technique a special technique that I've come up with now the stencils are available in kits uh available to amateurs who would want to do Reflow soldering um if you get a a specialized kit for your printed circuit board so that you can apply this solder paste in the proper pattern and then by using tweezers placing individual components onto the board now the board can be placed into an oven such as a toaster oven and raiseed to the proper temperature to melt the solder and in doing so you can get the same kind of professional quality that you'd get with a machine manufacturer board since the solder fumes can be uh costic and may release lead oxide uh it's probably not a good idea to use this in a toaster oven that you'd use for cooking so use a special oven dedicated for soldering