Components need to be assembled on the FPC flexible circuit board. With the increasing popularity of the smart wearable industry, surface mount SMD on FPC has become one of the development trends of SMT technology due to the limitation of assembly space. However, FPCS is more difficult to assemble than PCBS because of its lower assembly strength. Today, let's learn about the difference between assembling flexible boards and rigid boards.

1. Welding process

Similar to the PCB process, solder paste is applied to FPC and hard/soft junction boards through the operation of steel mesh and solder paste printing machines. But the surface of FPC is not flat, so we need to use some fixtures or reinforcements to fix it. Usually, we stick reinforcement in the component area of FPC.

2. Place SMT components

In the current trend of miniaturization of SMT components, small components may encounter some problems during reflow soldering. If the FPC is small, elongation and wrinkles will not be a serious issue, you can shrink the SMT frame or add label points. If you do not want to stick the reinforcing ribs to the bottom of the component, flexibility may be required after assembly. Therefore, SMT fixtures will be a good choice.

3. Reflow soldering process

FPC must be dried before reflow soldering. This is an important difference in the assembly process between FPC and PCB components. In addition to the dimensional instability of flexible materials, they also have relative hygroscopicity. They absorb water like sponges. After FPC absorbs water, reflow soldering must be stopped. PCBS also has the same problem, but with a higher tolerance. FPC needs to be at 225 ° C- 250° Preheat and bake at the specified temperature. This preheating and baking must be completed quickly within 1 hour. If not baked in time, it should be stored in a dry or nitrogen filled storage room.