EPA Lab Audit Checklist for PCBs Electrical Inspection

EPA has developed audit protocols to assist and encourage regulated entities in conducting environmental audits in accordance with EPA audit and small business policies. Furthermore, these protocols foster consistency among regulated entities when conducting environmental audits as well as identify violations against those provisions that require disclosure according to EPA audit and small business provisions. Regulatory checklists are included as part of these protocols.

1. Conduct a visual inspection of the PCBs

Visual inspection of PCBs is a crucial part of manufacturing process, ensuring all the components on the circuit board are correctly placed, solder joints free from defects and any stains or scratches on PCBs are identified during inspection.

Visual inspectors use an inspection checklist to detect defects on PCBs and to ensure their dimensions match specifications, which includes verifying electric connector placement in their correct positions and checking conductive patterns for integrity, clarity, burrs or voids; additionally they verify vias are in their proper places with diameter matching design specification.

Visual inspection is an effective means of inspecting circuit boards with low density packages; however, it should not be used on J-lead devices containing multiple high density packages, surface array flip chip devices or BGA solder joints.

2. Conduct a physical inspection of the PCBs

Physical inspection of PCBs is an integral step of production. This involves visually inspecting each board with either magnification or naked eyes and comparing its specifications against its design documents to ensure all specifications have been met. A physical inspection can identify various defects such as solder bridges, cold solder, open solder as well as verifying dimensions and ensure components are seated appropriately on their boards.

Physical inspection may be enhanced by other techniques, such as elemental analysis (EDS or XRF), to verify that the correct material was chosen for a component and meets all specified tolerances. Furthermore, destructive physical tests like dye penetrant testing or cross-sectioning may provide further assurances of conformance.

Mechanical testing should also be performed on the bare board to ensure it can withstand shocks and vibrations encountered in the field. This test typically examines holes on a PCB, measuring their thickness, length and polarity to make an assessment.

3. Conduct a chemical analysis of the PCBs

PCBs are highly persistent chemicals found throughout the environment. Accumulating in sediment and tissue, they become more concentrated at higher levels of the food chain, becoming toxic to fish and invertebrates as well as human exposure causing liver dysfunction, dermatitis, and dizziness at higher concentrations.

Old transformers are widely considered the primary source of PCB contamination in water and soil, though any transformer could potentially contain them, as oil leakage does not remain enclosed within an enclosed system and even units which were never intended to contain PCBs may still contain them.

At Pace Laboratory Network, our PCB analysis methods involve the extraction and cleanup of samples prior to gas chromatography for PCB analysis. Gas chromatography allows us to isolate individual chemical compounds (known as congeners) based on physical characteristics such as volatility or polarity, while recent advances in gas chromatography allow the use of open tubular capillary columns with improved resolution and selectivity over packed columns; we offer all instruments necessary for conducting a comprehensive PCB examination.

4. Conduct a moisture analysis of the PCBs

Due to PCBs being highly moisture sensitive, it is vitally important that they are stored and handled in a dry environment. Moisture exposure can cause delamination and conductive anodic filamentation (CAF), two common failure mechanisms in electronic circuit assembly. To limit moisture exposure as much as possible, all bare-board materials should be tested for moisture content before assembly and soldering begins; various methods including ion chromatography or vapor pressure desorption testing can be employed here.

Vapor pressure desorption methods can accurately ascertain the moisture content of PCB samples by measuring water vapor tension within their samples, which provides their relative humidity value, which can then be compared to an industry reference standard. Furthermore, this technique allows users to detect impurities on surface samples that might interfere with solderability; this information helps identify contaminants and devise suitable remediation solutions.