Step 1: Pre-Assembly Preparation and Verification
PCB bare board incoming inspection including appearance, dimension, and electrical performance verification
Component incoming inspection including model, package, quantity, and quality check according to BOM file
Component pre-processing including baking for moisture-sensitive components, tape and reel preparation
BOM file and centroid file verification and optimization
Stencil design and fabrication according to PCB pad and component package
Assembly program creation and calibration for pick and place machines
Production work order creation and process parameter locking
Step 2: Solder Paste Printing
Stencil installation and alignment on automatic screen printer
Solder paste printing parameter setting including scraper speed, pressure, and printing angle
Solder paste printing on PCB pads according to stencil design
100% 3D Solder Paste Inspection (SPI) after printing
Defect panel rework and parameter adjustment according to SPI results
Qualified panels transfer to component placement process
Step 3: Component Placement
Component loading on high-speed and high-precision pick and place machines
Machine vision calibration for component alignment accuracy
Automatic component placement on PCB pads according to centroid file
First Article Inspection (FAI) after first panel placement
Placement accuracy verification and program adjustment according to FAI results
Mid-production random inspection for placement quality
Placed panels transfer to reflow soldering process
Step 4: Reflow Soldering
Reflow oven temperature curve setting according to solder paste specification and component type
Panel loading into reflow oven with conveyor system
Soldering process through preheat zone, soak zone, reflow zone, and cooling zone
Real-time temperature monitoring and recording during reflow process
100% Automated Optical Inspection (AOI) after reflow soldering
Defect panel rework and temperature curve adjustment according to AOI results
Step 5: Through-Hole Component Assembly
Through-hole component lead forming according to hole pitch and board thickness
Manual or automatic component insertion into PCB holes
Wave soldering process for through-hole components
Selective soldering for complex through-hole components
Post-soldering cleaning to remove flux residue
Visual inspection for through-hole solder joint quality
Defect rework for cold solder, insufficient solder, and solder bridge
Step 6: Post-Assembly Testing and Inspection
In-Circuit Testing (ICT) for assembled boards according to test fixture
X-Ray Inspection for BGA, QFN, and other hidden solder joint components
Functional Testing (FCT) according to product functional specifications
Embedded System Testing for boards with firmware and programmable chips
Optional Aging Testing for high-reliability application orders
Final visual inspection for assembly quality, appearance, and board cleanliness
Step 7: Final Finishing and Packaging
Board cleaning to remove flux, residue, and foreign matter
Conformal coating application according to customer requirements
Labeling and serial number marking for traceability
ESD packaging with anti-static bags and desiccant
Packaging according to customer transportation requirements
Final quality audit before shipment
Delivery and tracking information notification to customer
