ShenZhen Leap Electronic Co.,Ltd


Mounting basics on FPC

Author: Date:8/13/2018 7:04:55 AM
 Mounting basics on FPC

The process of mounting SMD on a flexible printed circuit board (FPC) requires a considerable portion of the surface mount of consumer products at the time of the miniaturization of electronic products. Due to the assembly space, the SMDs are mounted on the FPC. Finishing the assembly of the whole machine. The surface mounting of SMD on the FPC has become one of the development trends of SMT technology. The following are the technical requirements and points for surface mounting.
I. Regular SMD placement

Features: Mounting accuracy is not high, the number of components is small, the components are mainly resistors and capacitors, or there are individual shaped components.

The key process: 1. Solder paste printing: FPC is positioned on the printing special pallet by external shape, generally printed by small semi-automatic printing machine, or manual printing, but the quality of manual printing is worse than semi-automatic printing.

2. Mounting: Generally, manual placement can be used, and individual components with higher positional accuracy can also be mounted by manual placement machine.

3. Welding: Reflow soldering process is generally used, and spot welding can also be used in special cases.

2. High-precision placement

Features: FPC should have MARK mark for substrate positioning, FPC itself should be flat. FPC is difficult to fix, consistency is difficult to ensure during mass production, and equipment requirements are high. In addition, printing solder paste and placement process control is more difficult.

Key process: 1.FPC fixing: from printing patch to reflow soldering, it is fixed on the pallet. The pallet used requires small thermal expansion coefficient. There are two fixing methods, and the mounting accuracy is QFP lead spacing 0.65MM or more. A; Mounting accuracy is Q. When the QFP lead pitch is 0.65MM or less, use method B.

Method A: The support plate is placed on the positioning template. The FPC is fixed on the pallet with a thin high temperature resistant tape, and then the pallet is separated from the positioning template for printing. The high temperature resistant tape should have a moderate viscosity and must be easily peeled off after reflow soldering, and No residual glue on FPC.

Method B: The pallet is customized, and its process requirements must be deformed after multiple thermal shocks. The pallet is provided with a T-shaped locating pin, and the height of the pin is slightly higher than FPC.

2. Solder paste printing: Because FPC is loaded on the pallet, the FPC has high temperature resistant tape for positioning, so the height is inconsistent with the plane of the pallet. Therefore, the elastic scraper must be used for printing. The solder paste composition has a great influence on the printing effect. Use a suitable solder paste. In addition, the printing template using the B method needs special treatment.

3. Mounting equipment: First, the solder paste printing machine, the printing machine preferably has an optical positioning system, otherwise the welding quality will have a greater impact. Secondly, the FPC is fixed on the pallet, but the total between the FPC and the pallet There will be some tiny gaps, which is the biggest difference from the PCB substrate. Therefore, the setting of the device parameters will have a great impact on the printing effect, placement accuracy, and soldering effect. Therefore, the FPC placement requires strict process control.

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