Just as PCB assemblies are complex, the NPI process, involving several stages, is also demanding. Read this article to learn more about them.
The NPI Workflow in PCB Assembly
Experienced contract manufacturers like Poland-based Assel implement the NPI practice involving several crucial points:
- Assigning a unique NPI number to a product to facilitate its tracking and documentation;
- Verifying data in the documentation provided by an original equipment manufacturer (OEM), ensuring that all necessary design files, such as Gerber files, Bill of Materials (BOM), Pick-and-Place files, and assembly drawings, are complete, accurate, and consistent;
- Validating product feasibility with pilot production of a small batch, usually of ten panels, to test the design, assess the workflow, identify faults, gather feedback, and refine the process before full-scale manufacturing;
- Overseeing assembly with active supervision by an NPI or manufacturing engineer, who monitors machine performance, identifies anomalies, inspects soldering and placement, gathers operator feedback, and documents observations to ensure quality.
- A formal review phase, where pilot run results are evaluated to decide whether all quality standards are met and unresolved issues are addressed, and the product is ready for mass production;
- Final reporting, which requires compiling a record of the NPI process, mentioning test results, resolved issues, and improvements to support traceability, quality assurance, and future improvements.
The Role of Documentation in NPI
Thorough documentation at every stage of the NPI process is essential for tracking progress and ensuring consistent product quality. Manufacturers can establish a clear framework based on the consistent records of insights, decisions, and deviations captured during the pilot production. This helps maintain quality across future production runs and facilitates troubleshooting and smoother onboarding for similar projects.
PCB Assembly Testing in NPI
PCB assembly testing in NPI includes key steps like Solder Paste Inspection (SPI), X-Ray analysis, RLCD checks, visual inspection, and documentation verification. These tests ensure the assembly meets design and performance standards, helping to spot potential manufacturing issues early and ensuring the final product meets the OEM’s requirements.
SPI
SPI is carried out immediately after the application of solder paste. It is essential to ensure accurate placement, volume, height, and alignment. Experienced contract manufacturers like Assel never overlook this step, as soldering defects can be rather hard to fix later in the process.
The inspection is often performed using automated systems based on high-resolution 3D imaging, typically via structured light or laser triangulation, which can scan each board and create a precise 3D map of the solder paste. This allows for accurate measurement and quick identification of issues such as insufficient paste, excess material, or misalignment.
X-Ray Inspection
X-ray inspection is effective, yet time-consuming and costly. For that reason, it is typically used for complex or high-density assemblies, especially those with hidden or bottom-terminated components such as Ball Grid Arrays (BGAs), Chip-Scale Packages (CSPs), or Quad Flat No-Leads (QFNs), where traditional optical inspection cannot access. It is crucial in high-reliability sectors like aerospace, medical devices, and automotive electronics.
X-ray analysis provides a view inside the assembly, revealing hidden defects such as insufficient or cracked solder joints, solder voids, bridging, and misaligned components. This is especially important for checking lead-free soldering, which can be more easily affected by changes in the manufacturing process.
RLCD Checks
RLCD testing, which focuses on Resistance, Leakage, Capacitance, and Diode behaviour, is used to confirm the electrical integrity of a PCB after assembly. It helps catch issues like short circuits, open connections, incorrect component placements, or faulty parts that could stop the board from working properly.
These checks are usually carried out with dedicated test equipment, such as an LCR (Inductance, Capacitance, Resistance) meter or automated systems built into the production line.
Functional Testing
Functional testing is used to assess whether a finished PCB assembly works as intended in real-world conditions. It is often one of the most important steps in the NPI process.
During the test, power is applied to the board, and signals are sent to simulate how the product will be used. The system then checks the outputs to confirm that everything responds correctly. This can involve tools like boundary scan systems, dedicated functional test fixtures, or Automated Test Equipment (ATE), depending on the complexity of the product.
The goal is to validate that the full circuit, including components, connections, and embedded software, if present, works together as intended.
Final Thoughts
NPI in PCB assembly cannot be omitted as it guarantees the product is ready for mass production. All of the steps, such as thorough documentation, early testing, and proactive issue resolution, are crucial for NPI, too. If you are looking for a contract manufacturer with significant expertise in NPI, visit asselems.com.
