🛠️ SMT PCBA Repair & Rework Process – Step by Step

🔍 Step 1: Defect Detection

Sources:

• AOI (Automated Optical Inspection) – Solder bridges, missing components, polarity issues

• X-Ray Inspection – BGA, LGA, or QFN solder voids or bridging

• ICT (In-Circuit Test) – Open/short circuits, bad components

• FCT (Functional Test) – Functional failures

• Visual/Manual Inspection – Cosmetic issues, mechanical damage

Common Defect Types:

📝 Step 2: Defect Documentation & Logging

• Use MES (Manufacturing Execution System) or manual defect log sheets.

• Information recorded:

  • Board serial number

  • Operator/station ID

  • Defect type and location (with image if possible)

  • Inspection/test data

• Barcode or QR code scanned for traceability

🧠 Step 3: Root Cause Analysis (RCA)

• Performed by Process Engineer or Quality Team

• Methods:

  • Visual magnification (up to 30x)

  • X-ray for internal joints (e.g., BGA)

  • Microscope or endoscope

  • Electrical probing for circuit-level diagnosis

• Identify cause: process issue, material defect, operator error, design issue

🔧 Step 4: Rework Authorization and Approval

• Engineer issues Rework Instruction Sheet (RIS) or Job Traveler

• Only trained IPC-certified technicians (IPC-7711/7721) perform rework

• Ensure rework count is tracked (e.g., max 2 times allowed per pad)

🧰 Step 5: Rework Execution

Based on Defect Type:

🪛 1. Component Replacement

Steps:

• Apply preheating if multilayer PCB

• Use hot air rework station or IR heater

• Desolder the component (tweezer, soldering iron)

• Clean pads with flux and solder wick

• Reapply solder paste (if needed)

• Place new component with tweezers

• Reflow using hot air tool

• Inspect under microscope

🧽 2. Solder Bridge Removal

Steps:

• Use solder wick and flux to remove excess solder

• Clean area with IPA (Isopropyl Alcohol)

• Visual/microscopic inspection

🔄 3. Cold/Insufficient Solder Joint Repair

Steps:

• Apply flux to the joint

• Reheat with soldering iron or hot air

• Add fresh solder

• Cool naturally and inspect

⚡ 4. Open Circuit or Broken Trace Repair

Steps:

• Locate broken trace using continuity test

• Use jumper wire or trace repair kit

• Apply UV curable coating for protection

• Label the modification (for traceability)

📐 5. Lifted Pad or Damaged Pad Repair

Steps:

• Use copper pad repair kits

• Attach replacement pad with epoxy

• Reconnect trace via wire or conductive ink

• Cure and test continuity

• Apply conformal coating if required

🔁 Step 6: Retesting and Verification

• Reworked PCB is re-tested at:

  • AOI or Visual Inspection

  • ICT (if electrical change was made)

  • FCT (if function was impacted)

• Must pass all test parameters

• High-risk reworks may undergo X-ray or Thermal Cycling

📄 Step 7: Documentation & Traceability

• Update rework database with:

  • Rework action taken

  • Technician name & time stamp

  • Result of re-inspection or testing

  • Notes for future preventive action

• Update labels or traceability barcodes if necessary

✅ Step 8: Final QC Sign-Off

• Quality Engineer or Supervisor validates:

  • Repair completeness

  • Test pass

  • Cosmetic condition

• PCB moves to packing or shipment

📋 Tools and Equipment Used in Rework

🔐 Standards Followed

• IPC-7711: Rework of Electronic Assemblies

• IPC-7721: Repair of Printed Circuit Boards

• IPC-A-610: Acceptability of Electronic Assemblies