I. Pre-production Preparation

1. Material Verification & Inspection
   Verify specifications, quantity and shelf life of PCB boards, ICs, resistors, capacitors, solder paste, stencils and other materials.
2. Solder Paste Tempering & Mixing
   Take solder paste out of the refrigerator and temper for more than 4 hours, then mix evenly manually or automatically.
3. Stencil Fabrication & Installation
   Laser-cut stencils based on PCB files and install them onto the printing machine.
4. Programming
   Import coordinate files into mounters, SPI, AOI and other equipment, and edit production programs.
5. First Article Preparation
   Prepare tooling and fixtures required for first-article production.

II. Solder Paste Printing (Core First Step)

1. Feed PCB boards into the solder paste printer.
2. The squeegee prints solder paste onto PCB pads through the stencil.
3. Key control points: thickness, uniformity, insufficient solder, excessive solder, bridging.

III. SPI Solder Paste Inspection

IV. Component Mounting

1. High-speed mounters mount small components (0402, 0603 resistors, capacitors, etc.).
2. General-purpose mounters mount large / special-shaped components (ICs, BGAs, QFNs, connectors, etc.).
3. Inspect component orientation, offset and missing parts after mounting.

V. Reflow Soldering

1. PCBs enter the reflow oven and go through four zones: preheating → soaking → soldering → cooling.
2. Solder paste melts, forming reliable solder joints between components and pads.
3. Control temperature profile to prevent cold joints, tombstoning and offset.

VI. Appearance & Quality Inspection

1. AOI (Automatic Optical Inspection)
   Detect missing parts, offset, reverse mounting, cold joints, bridging and false soldering.
2. X-Ray Inspection (for BGAs / QFNs only)
   Check voids, insufficient soldering and short circuits under BGA solder joints.
3. Manual visual re-inspection.

VII. Defect Rework

1. Rework defective solder joints / components with a hot-air rework station.
2. Replace wrong components, supplement missing parts and rework defective solder joints.
3. Re-inspect after rework.

VIII. Post-process (According to Product Requirements)

1. DIP Insertion (if through-hole components are required)
2. Wave soldering / manual soldering of through-hole pins.
3. Cleaning, pin cutting, functional testing (FCT / ICT).
4. Depaneling, program burning, appearance cleaning.
5. Packaging & warehousing.

Simplified Process (Quick Reference)