During PCB fabrication and PCBA assembly, conductive foreign particles such as copper debris, solder residues, and metal shavings may enter the assembly through PCB processing, SMT production, soldering, equipment wear, or manual assembly. Although often microscopic, these particles can create unintended electrical connections between conductors at different potentials, compromising insulation and potentially causing short circuits, component damage, or even system-level failures.
The following are five typical failure scenarios caused by metal particle contamination in PCBA manufacturing.
1. Metal Particles Bridging Adjacent IC Pins
When copper debris, solder particles, or other conductive contaminants enter the gaps between adjacent IC pins, they may contact two or more pins simultaneously, creating an unintended conductive path and causing a short circuit.
2. Short Circuits Between Power and Ground Traces
In power management boards, industrial control boards, and energy management systems, power and ground traces often feature large copper areas, but may have narrow clearances in certain locations.
If a metal particle falls between copper traces, pads, or exposed conductors at different potentials and makes contact with both, it can create a low-impedance conductive path, resulting in a short circuit.
3. Metal Particles Trapped Beneath BGA and QFN Components
BGA and QFN packages share one common characteristic: some solder joints are located underneath the components and cannot be directly inspected through conventional visual inspection.
This makes metal particle contamination in these areas particularly difficult to detect.
If metal particles enter the pad area before component placement or remain trapped beneath a component during assembly, they may come into contact with adjacent solder joints or conductive areas, creating unintended electrical connections.
4. Metal Particles in High-Voltage Circuit Areas
In inverters, energy storage systems, power conversion equipment, and industrial drives, PCBs often contain circuit sections operating at different voltage levels.
To prevent electrical breakdown and leakage, appropriate clearance and creepage distances must be maintained based on operating voltage, material properties, and environmental conditions.
When conductive metal particles enter high-voltage areas, they may reduce the effective clearance between conductors. If a particle bridges two conductors, it can directly cause a short circuit. Even without direct contact, it may increase the risk of localized electric field concentration and insulation failure.
5. Metal Particles in Connector and Terminal Areas
Connectors, terminal blocks, and relays typically contain multiple closely spaced metal contacts.
During assembly, metal particles may become trapped inside connectors, between terminals, or around PCB solder joints. If a particle simultaneously contacts two different terminals, it may create an unintended electrical connection and cause a short circuit.
