SMT Rework Guide: 5-Step PCBA Fault Diagnosis Process by Sinmicro Experts
Why 78% of PCBA Failures Can Be Repaired (Not Replaced)
In SMT assembly and PCBA usage, common issues like soldering defects (23% of failures), component aging (18%), and testing errors (12%) often lead to malfunctions. At Sinmicro, our ISO 9001-certified rework process has successfully repaired 92% of defective boards, saving clients an average of $15,000/month in replacement costs.
5-Step PCBA Fault Diagnosis Protocol
Step 1: Visual Component Inspection
Checklist:
✅ Missing components (QFN/BGA packages most vulnerable)
✅ Polarity errors (Diodes, electrolytic capacitors)
✅ Physical damage (Burnt marks, cracked ICs)
✅ Solder bridges (0.5mm pitch components)
Pro Tip: Use 10X magnification for 0402/0201 components
Step 2: Component Orientation Verification
High-Risk Components:
Tantalum Capacitors: Reverse polarity causes explosions
LED Arrays: Incorrect placement kills entire strings
Connectors: Misaligned pins create intermittent faults
Sinmicro Solution: Automated optical inspection (AOI) with 99.98% accuracy
Step 3: Solder Joint Analysis
Common Defects We Fix:
Defect Type Detection Method IPC-610 Standard
Cold Solder X-Ray inspection Class 3 requirement
Tombstoning 3D AOI scanning ≤0.1% tolerance
Insufficient Solder Cross-sectional analysis >75% pad coverage
Critical Tools:
Thermal imaging cameras (Find cold joints)
Solder paste inspection (SPI) machines
Step 4: Electrical Testing
Essential Tests:
In-circuit testing (ICT)
Flying probe for open/short circuits
Functional testing under load
Step 5: Power-On Validation
Safety Protocol:
Use current-limited power supply
Monitor temperature with IR sensors
Gradual voltage ramp-up (0→5V in 10s)
Pass Criteria:
No smoke/sparks during activation
≤2% deviation from expected current draw
Why Choose Sinmicro for PCBA Rework?
✅ Certified Expertise: IPC-7711/7721 certified technicians
✅ Advanced Equipment:
CyberOptics SE300 Ultra AOI
Nordson DAGE XD7500 X-Ray
✅ Traceable Process: Full repair reports with before/after images
✅ Fast Turnaround: 48-hour standard service (Urgent 24-hour available)
Case Study: Automotive ECU Repair
Issue: Intermittent CAN bus failures
Diagnosis:
Found 2 cold solder joints on CAN controller
Detected reversed TVS diode
Repair:
Reflowed affected areas
Replaced diode with correct orientation
Result: 100% functional recovery, saving $8,200 vs replacement
FAQ: SMT Rework Essentials
Q: How long does typical PCBA repair take?
A: 90% of repairs completed within 72 hours (expedited 24-hour service available).
Q: Do you provide warranty on repaired boards?
A: Yes! 180-day warranty on all rework services.
Q: Can you handle BGAs with 0.3mm pitch?
A: Our X-Ray rework stations support down to 0.25mm pitch components.
Q: What file formats do you need for repair?
A: BOM, schematic, and Gerber files (Altium/PADS/KiCad accepted).
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