Flexible PCB supplier china tells you how is FPCA manufacturing process.

1. Solder paste printing

The solder paste is placed on the stencil with the frame, and the solder paste is leaked onto the FPC plate by the scraper. In SMT processing, 60-70% of the quality problems occur in the solder paste printing process. 

2.  SPI（Solder paste inspection）

To ensure the printing quality of solder paste, solder paste inspection is a necessary step.  

 3．SMT (Surface)

Components are placed on Feeder, and automatic placement machines will accurately install components on the FPC plate by identifying the Pick & Place file set in advance by the engineer.

4．Reflow welding

The main function of reflow welding is to achieve SMT electronic components and FPC board welding, the following is his process principle:
When the FPC enters the heating zone (dry zone), the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste wets the pad, the end of the component and the pins, and the solder paste softens, collapses and covers the pad, the end of the component and the pins and is isolated from oxygen. When the FPC enters the insulation zone, the FPC and the component are fully preheated. To prevent FPC from suddenly entering the welding high-temperature zone and damaging FPC and components → When FPC enters the welding zone, the temperature rises rapidly so that solder paste reaches the melting state, liquid solder to the FPC pad, component end and pin wetting, diffusion, diffuse flow or backflow mixed to form solder contacts →FPC enters the cooling zone and solidifies solder joints.

5. AOI

Automatic Optic Inspection uses optical principle to detect common defects in SMT process.  AOI scans FPC automatically through the camera, collects FPC images, and compares the collected FPC image data with the input parameters in the database. After simple image processing, the welding defects of FPC board are determined, and the defects are marked/displayed through the automatic marking device or equipment display, so that workers can repair in time.

6.Repair

After AOI, it is necessary to repair the circuit board with problems, such as excessive solder, solder insufficient, empty solder, open solder, missing component, floating solder, backward Part and other problems.