Low melt solder is not commonly used in the soldering world. Many solder users tend to go with the typical SAC 305, 60/40 or 63/37 composition for strong joints and medium temperature. But, for those pesky electronic components that are smaller and harder to heat up low melt solder can in handy. It is available in two forms, a wire or a paste. Remember that low melt solder will not have the same strength in it as the SAC305, 60/40 or 63/37 solder. This is why larger components are better off not being soldered this way. Now, depending on what needs to be soldered the technique is very different. Let’s take a quick look shall we?
Low temp alloy can be made as leaded or lead free. Many people think of it as a removal tool which is correct, but it also has other uses. Low melt solder can be used for reworking on PCB and similar boards with pre-soldered components.
When reworking a board remember the new component needs to be heated without heating up the components in place. This also reduces the risk of nudging them out of place. Using a low melt solder in these situations will prevent damage. It also keeps the temperature of the board and the solder from heating up too much. Doing this ensures the new component is attached properly. Temperature sensitive devices benefit from this the most. There are other parts that can be damaged at high temperatures as well.
Another use for low melt solder is for sensitive components. These components cannot handle the regular heat from a soldering iron. In this case the paste would be a better application method than the typical wire. This would be because it allows for hot air to be used to melt the paste. For ribbon cables that need to be soldered, the low melt solder paste becomes a lifesaver. It doesn’t require a super strong joint and too much heat can prevent the ribbon from working properly. The low melt solder paste makes it simple to create a bond between the sensitive ribbon and the board.
I hope that this was able to help you decide how you want to use low melt solder. Especially in times that you’re not sure if stronger joints are needed.