How to check the PCB quality?
Updated: Sep 4, 2020
A Printed Circuit Board, often referred to as #PCB is a thin board made of fiberglass and laminate material to connect electronic components such as resistors, transistors, ICs, etc. They are extensively used in computers, video cards, net, expansion cards, etc and connected to a motherboard, which is also a PCB.
So in conclusion, PCB can be considered as the heart of electronic devices and miniaturization leading to shrinking size and complex structures.
Despite the extensive use of a PCB and proper designing, it is important to ensure quality control which mainly includes administration, monitoring, and measurement, manufacturing, and inspection.
It all comes down to two major aspects.
PCB Quality Control - Fabrication
This is the stage where the quality is tested before the components and elements are placed on the board and the material quality is of peak importance here. There are multiple tests that can be performed to check the board edge clearance, spacing, etc so that the layout remains true to its design.
Manual Inspection: This is the process where trained engineers manually look into the boards for errors or unnecessary debris found on the surface.
Design for Manufacturing - This method is often referred to as DFM and is checked against the contract manufacturer's (CM) constraint. The tests used are as follows:
Bed of Nails Test: This method involves an electronic fixture that has many pins to contact test points on the PCB.
Flying Probe E Test: This non-invasive test is used to check the continuity and is used for prototype runs.
Sawing: In this destructive test where the board is cut into pieces, stacked on top of each of the other for visual inspection.
Automated Optical Inspection (AOI): This is a much effective method than manual inspection and can detect problems such as line width violations, spacing violations, cut traces or pads, shorts circuits, and drill hole breakages.
How to ensure quality in Component Placement?
Once the manufacturing process is complete, we move onto the next stage, PCB Manufacturing. the quality control measures to be taken to avoid potential errors.
Kit Accuracy and reliable suppliers: Ensure that all the components are purchased from reliable sources for accurate results, else it will lead to unwanted expenses and extensive delay. the tolerance check can be conducted to the components to make sure that the components meet the datasheet values.
MPN - Footprint Match - This footprint matching method lets you avoid errors that may violate solder relief and component spacing requirements.
Solderability Testing - This accelerated "aging" process is for samples to ascertain solderability.
But it all comes down to this.
BOM Validation is conducted to ensure that he components in the BOM match the PCB design.
MPN verification - Manufacturer Part Numbers can be wrong thereby resulting in the acquisition of incorrect components (can be caused by the fault even in a single number). Such an error only results is the loss of cost and time.
Component Reference Designator verification - This is a unique identifier and ensures error-free components.
Component Manufacture Status checking - This is mainly used to keep track that the product is available for future production.
Quality Control for Assembly
This is the final stage of PCB manufacturing and thereby involves stages that are more intensive than during fabrication. A few common techniques done before quality control are as follows.
Visual Inspection: This process is mainly done to check excess solder, component connection issues, and other rework issues. Cameras and microscopes are used to take photos to improve visual inspections.
Electrical testing: Flying Probe E Test and Bed of Nails test are commonly used to examine levels parameter levels and conductivity can be checked.
X-Ray Inspection: As the name implies, it is used to check the inner parts of the PCB's inner quality mostly followed by sawing to inspect vias.
During each stage of the PCB manufacturing process, the quality must be checked and researched to make sure that the boards are perfectly built and that they are precise, fast, and preferably transparent.