SMT ASSEMBLY COST ESTIMATOR
FLEX PCB ASSEMBLY COST ESTIMATOR
DESIGN FOR MANUFACTURING GUIDELINES
Component Placement
Maintain Adequate Component Spacing
Ensure minimum spacing between components to allow for proper solder paste application and prevent bridging. This also facilitates rework and inspection access.
0402: ≥0.15mm
0603: ≥0.2mm
0805: ≥0.25mm
QFP: ≥0.5mm
Pad Design
Optimize Pad Dimensions for Reflow
Pad size affects solder joint quality. Follow IPC-7351 standards for land pattern design. Consider thermal relief for large ground pads to prevent tombstoning.
Pad Extension: 0.1-0.3mm
Aspect Ratio: 1:1 to 1.5:1
Thermal Via: ≥0.3mm dia
Fiducial Marks
Include Global and Local Fiducials
Fiducial marks enable accurate pick-and-place alignment. Place global fiducials at diagonal corners, and local fiducials near fine-pitch components (≤0.5mm pitch).
Size: 1-3mm diameter
Clearance: 3mm minimum
Copper with solder mask opening
Panelization
Design for Efficient Panel Utilization
Consider panel design early. Include tooling holes, breakaway tabs, and V-score lines. Proper panelization reduces cost and improves handling during assembly.
Rail Width: 5-10mm
Tooling Hole: 2-3mm
Tab Width: 2-3mm
BGA Design
BGA Pad and Via Guidelines
BGA packages require careful via placement. Use via-in-pad with filled and capped vias for fine-pitch BGAs. NSMD pads are preferred for better solder joint reliability.
Via Size: 0.25-0.3mm
NSMD Pad: Ball dia - 20%
Dog-bone escape: 0.8mm+ pitch
Solder Paste
Stencil Aperture Design
Proper stencil design ensures correct solder volume. Area ratio should be >0.66 for reliable paste release. Consider step-down stencils for mixed component heights.
Area Ratio: >0.66
Thickness: 100-150μm
Aperture Reduction: 10-20%
PCB ASSEMBLY TESTING METHODS
Automated Optical Inspection (AOI)
High-speed camera systems inspect PCBs for placement accuracy, solder quality, polarity errors, and missing components. Ideal for high-volume production with 99%+ defect detection rate.
Speed: 20-60 cm²/s
Resolution: 10-20μm
Cost: $0.02-0.10/board
Best For: SMT lines
X-Ray Inspection (AXI)
Essential for inspecting hidden solder joints under BGAs, QFNs, and other leadless packages. Detects voids, bridges, and insufficient solder that optical inspection cannot see.
Resolution: 1-5μm
Void Detection: >25% area
Cost: $0.50-2.00/board
Best For: BGA, QFN, PoP
In-Circuit Test (ICT)
Uses bed-of-nails fixture to test individual components on populated boards. Verifies correct values, shorts, opens, and basic IC functionality. Requires test point access.
Coverage: 80-98%
Fixture Cost: $2K-15K
Test Time: 10-30 seconds
Best For: High volume
Functional Test (FCT)
Tests the assembled board under operating conditions to verify it performs as designed. Can include boundary scan, firmware loading, and application-specific testing.
Coverage: Application-specific
Fixture Cost: $1K-10K
Test Time: 30s-5min
Best For: Final validation
Flying Probe Test
Fixtureless testing using moving probes for low-to-medium volume production. Lower setup cost than ICT but slower. Ideal for prototypes and boards with limited test access.
Setup Cost: $100-500
Test Time: 1-10 minutes
Min. Pad Size: 0.2mm
Best For: Prototypes, NPI
Boundary Scan (JTAG)
IEEE 1149.1 standard test method using built-in test logic in ICs. Tests interconnects between JTAG-compliant devices, programs flash memory, and enables system diagnostics.
Coverage: JTAG devices + interconnects
Setup Cost: $500-2K
Test Time: 1-60 seconds
Best For: Complex digital
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