In the development of electronic products miniaturization, a considerable part of the consumer products surface mount, due to the relationship between the assembling space, the SMD are mounted on the FPC completed. FPC assembly machine on SMD surface mount SMT technology development trend has become one of. For surface mount technology requirements and pay attention to the following points.
1. Conventional SMD mount
Features: the requirement is not high, the device is not high, the number of components is small, and the components are mainly based on the resistance capacitance, or there are some special shaped components.
Key: 1. Solder paste printing FPC positioning by appearance on a special pallet for printing. In general, the small semi automatic printing machine printing, can also be used for manual printing, but manual printing quality than the semi automatic printing worse.
2 paste: generally available by hand, the location of some of the higher precision of individual components can also be used manual placement machine.
3 welding: generally use reflow soldering process, special circumstances can also be used in spot welding.
Two. High precision mounting
Features: FPC to position the substrate was labeled with the mark, the FPC to temper. FPC is hard to fix, batch production consistency is difficult to assurance, high requirements for equipment. In addition to the solder paste printing and mount process is difficult to control.
Key process: 1.FPC fixed: from printed patch to reflow soldering full fixed on the supporting plate. Pallet requirements for thermal expansion coefficient smaller. Fixed method has two, attached to fit accuracy of QFP lead spacing 0.65MM above using a method; post fit accuracy is below QFP lead spacing 0.65MM B. method
Method a: plate set on the positioning template. FPC thin resistant high temperature adhesive tape fixed on the supporting plate, and then let supporting plate and the positioning template separation, printing. High temperature resistant adhesive tape should be moderate viscosity, after reflow must be easy to peel, and the FPC residue free adhesive agent.
Method B: pallet is customized and the process requirements must be after repeated thermal shock deformation minimum. Support plate is provided with a T type positioning pin, pin height than the FPC slightly higher point.
2. Solder paste printing: because pallet loading FPC, FPC is used for positioning resistant high temperature tape, height and flat pallet inconsistent, so printing must use elastic blade. Solder paste composition has a greater impact on printing effect, must choose suitable paste. Also the selection method B printing template need to go through special treatment.
3. Mount equipment: first, the solder paste printing machine, printing machine preferably with optical positioning system. Otherwise, the welding quality will have a greater impact. Secondly, FPC fixing on the supporting plate, but between FPC and the supporting plate are always produced some very small gaps. This is the biggest difference with the PCB substrate. Because the equipment parameter setting on the printing effect and placement accuracy, welding effect will have a greater impact. Therefore FPC mount for the process control in the strict requirements.
Three. Other: in order to ensure the quality of assembly, in front of the FPC on the best after the drying process.