What Should be Paid Attention to in SMT Double-sided Placement

With the gradual miniaturization of electronic products, the corresponding PCB size is also slowly decreasing. If you want to mount enough electronic materials in a limited space, sometimes it is not enough to rely on single-sided placement, and it needs to be achieved by double-sided placement.

Double-sided placement, as the name implies, means that both sides of the PCB need to be mounted. This technology requires placement one side of the PCB before placing the other side of the PCB. This placement method can not only utilize the limited space of the PCB, but also ensure the aesthetics and functionality of the PCB. So what do you need to pay attention to when doing double-sided placement?

1. Electronic components with high heat resistance are mounted first. Because some electronic components cannot withstand two high-temperature soldering, the components that are not resistant to high temperature are usually mounted on the second side when re-placement, so that it does not need to be soldered twice.

2. When performing double-sided placement, it is also necessary to follow the principle of light first and then heavy. Because the double-sided placement needs to reverse the position. If the volume and weight of the component after the second reflow soldering are large, it is easy to cause the component to loosen due to its weight during the second soldering, causing the component to shift or even drop. Therefore, in general, when placement on both sides, it is necessary to first mount and weld the integrated surface of electronic components with small volume and light weight, and mount the electronic components with heavy weight and large volume to the other side.

3. When welding, usually the welding temperature of the second side needs to be lower than that of the first side, because the first side needs to be welded twice. If the temperature of the second soldering is the same as that of the first soldering, it will cause the solder paste on one side to melt and cause the components to drop. So, when performing the second welding, the temperature should be lower than that of the first welding, and the temperature difference is about 5°C.

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