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Flexible pcb manufacturing process

 

Here we use the ordinary carrier board as an example to detail the SMT points of the flexible pcb. When using the silica gel board or the magnetic fixture, the fixing of the flexible pcb is much more convenient, no need to use the tape, and the technics points of the printing, SMT, welding and other processes are the same.

Flexible pcb manufacturing process

Fixed pcb:

Before performing SMT, it is first necessary to accurately fix the flexible pcb on the carrier board. It is important to note that the shorter the storage time between printing, smt and soldering after the flexible pcb is attached to the carrier, the better. The carrier board has two types: positioning pins and no positioning pins. The carrier board without the positioning pin should be used together with the positioning template with the positioning pin. First, the carrier board is placed on the positioning pin of the template, so that the positioning pin is exposed through the positioning hole on the carrier board, and the flexible pcb is placed one by one. The exposed locating pins are then taped and the carrier is separated from the flexible pcb positioning template for printing, SMT and soldering. A number of spring positioning pins with a length of about 1.5 mm have been fixed on the carrier board with the positioning pins. The flexible pcb can be directly placed on the spring positioning pins of the carrier plate and then fixed with tape. In the printing process, the spring positioning pin can be completely pressed into the carrier by the stencil without affecting the printing effect.

 

Method 1 (single-sided tape fixing): Fix the flexible on both sides of the board with a thin high-temperature single-sided tape. Don’t allow the FPC to be offset and warped. The viscosity of the tape should be moderate. It must be easily peeled off after reflow soldering. There is no residual glue on it. If you use the automatic tape machine, you can quickly cut the length of the tape, which can significantly improve efficiency, save costs and avoid waste.

 

Method 2 (double-sided tape fixing): firstly attach the high-temperature double-sided tape to the carrier board, the effect is the same as that of the silica gel board, and then attach the FPC to the carrier board, pay special attention to the viscosity of the tape should not be too high, otherwise peeling after reflow soldering it’s easy to cause the FPC to tear. After repeatedly passing the furnace, the viscosity of the double-sided tape will gradually become lower, and the viscosity is so low that it cannot be reliably fixed when the FPC cannot be reliably fixed. This station is a key station to prevent the FPC from being dirty, and it is necessary to wear a finger sleeve. Before the carrier is reused, it needs to be properly cleaned. It can be scrubbed with a non-woven cloth cleaning agent or an anti-static dust roller to remove foreign matter such as surface dust and tin beads. Do not use excessive force when handling FPC. FPC is fragile and prone to creases and breaks.

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