PCBA FAQ & Troubleshooting Handbook

Answer: PCB (Printed Circuit Board) is a bare board with copper traces and pads, without electronic components. PCBA (Printed Circuit Board Assembly) is a finished board with all components mounted and soldered, ready for use in electronic devices. Simply put: PCB = bare board; PCBA = assembled and functional board.

Answer: Common materials include FR-4, FR-1, CEM-1, and metal-core substrates. Key differences:

• FR-4: Epoxy glass laminate, high Tg (≥130°C), strong insulation and mechanical strength. Most widely used for consumer electronics, industrial control, communications;
• FR-1: Phenolic paper laminate, low cost, lower heat resistance (Tg ≤100°C). Used in low-cost devices such as toys and chargers;
• CEM-1: Composite epoxy material, performance between FR-1 and FR-4. Balances cost and performance;
• Aluminum PCB: Excellent thermal conductivity. Used for high-power, high-heat applications such as LED drivers and power boards.

Answer: Primary processes are Reflow Soldering, Wave Soldering, and Manual Soldering:

• Reflow Soldering: For SMD components. Solder paste is printed, components placed, then heated in a reflow oven. High efficiency, consistent joints; high equipment cost, not for through-hole;
• Wave Soldering: For through-hole and mixed technology. Board passes over molten solder wave. Good for through-hole; lower consistency, risk of bridging;
• Manual Soldering: For prototypes, small batches, rework. Flexible, no large equipment; low efficiency, quality depends on operator skill.

Answer: Main causes and prevention:

• Cause 1: Poor solder paste (expired, oxidized, uneven printing). Use qualified paste, follow shelf life, control printing parameters;
• Cause 2: Oxidation or contamination on leads or pads. Clean components, use anti-oxidation finishes (HASL, ENIG), wear ESD gloves;
• Cause 3: Incorrect temperature or time. Set proper reflow/wave profile; manual soldering: 260±20°C, ≤3 seconds per joint;
• Cause 4: Misalignment. Ensure component pins align accurately with pads.

Answer: Static electricity damages ICs, MOSFETs, and sensitive components. Strict ESD protection is required:

• Environment: ESD floor, mat, ion fan; humidity 40%–60%;
• Personnel: ESD wrist strap (grounded), gloves, garments; no bare-hand contact;
• Storage: Use anti-static bags and bins;
• Grounding: All equipment grounded; resistance ≤4Ω.

Answer: Tests ensure quality and function:

• General: Visual inspection, continuity/open/short test, solder joint strength;
• Special: Insulation resistance, Hi-Pot, functional test, temperature/humidity aging.

Answer: Visual inspection + instrument test:

• Visual: Swelling (capacitors), burning, cracking, broken leads, lifted pads;
• Instrument: Multimeter for resistance, capacitance, diode values; oscilloscope for signals; functional test fixture for complex issues.

Answer: Proper preparation prevents damage:

• Environment: Clean, dust-free, ESD-safe;
• Material: Verify model, version, accessories;
• Tools: Proper ESD screwdrivers, tweezers;
• Personnel: ESD protection, familiar with procedure.

Answer: Improper mounting causes bending, pad lift, or short circuit:

• Screw size: Match hole and length; avoid too long/short;
• Torque: Tighten evenly; 0.5–1.5N·m recommended;
• Insulation: Use washers near circuits if needed;
• Sequence: Tighten diagonally to avoid warping.

Answer:

• Avoid pressing or touching components directly;
• Use proper tools; do not pull wires or pins;
• Install in correct orientation;
• Maintain full ESD protection.

Answer:

• Cables: Match connectors, insert fully; pull by housing, not wire;
• Housing: Avoid sharp edges; allow heat dissipation;
• Environment: Use seals/gaskets for dust and moisture protection.

Answer:

• Use positioning holes and pins for alignment;
• Ensure connectors and cables are secure;
• Distribute stress evenly to avoid bending.

Answer:

• Visual: No damage, loose parts, proper connections;
• Continuity: Check for short/open circuits;
• Voltage: Match rated power;
• Ground: Good chassis ground, resistance ≤4Ω.

Answer: Troubleshoot in order (disconnect power first):

• Check input power, adapter, cables, and connectors;
• Check power input, switch, fuse, and power paths;
• Inspect power ICs, capacitors, MOSFETs for damage;
• Verify ground connection.

Answer:

• Check power stability;
• Check heat dissipation; clean or upgrade heatsinks;
• Check loose connectors and mounting;
• Check aged components (especially capacitors).

Answer: Disconnect power immediately.

• Visual inspection for burning or charring;
• Multimeter in beep mode; isolate components one by one;
• Use test fixture for batch issues;
• DO NOT power on until short is fixed.

Answer:

• Component fallen: Clean pad, re-solder or replace component;
• Pad lifted: Repair by wire-jump to inner trace; replace board if badly damaged.

Answer:

• Component aging (caps, resistors); replace worn parts;
• Moisture, dust, corrosion; clean with alcohol, improve sealing;
• Dust buildup; clean regularly to restore cooling.

Answer:

• Warranty: 1–2 years consumer; 2–3 years industrial (per contract);
• Covered: Manufacturing defects, component quality issues;
• Not covered: Misuse, improper installation, ESD damage, unauthorized modification, environmental damage.

Answer:

• Required info: PCBA model, version, batch; equipment model; failure details; operating conditions;
• Process: Contact support → initial diagnosis → return → repair → test → return to customer.

Answer:

• Environment: Dry, clean, ventilated; -20°C to 60°C, humidity 40–60%;
• Operation: Follow procedures; avoid stress/vibration;
• Maintenance: Regular cleaning, inspection, replacement of worn parts;
• ESD: Always protect against static damage.