How do you test PCBs before and after fabrication?

1 Design verification

Before sending your PCB design to a fabrication service, you should verify that it meets your specifications and requirements, as well as the industry standards and best practices. Design verification can be done using software tools that perform various checks and simulations, such as DRC (design rule check), which verifies the layout follows the rules of the chosen fabrication service; ERC (electrical rule check), which verifies the schematic matches the layout; LVS (layout versus schematic), which compares the layout and schematic; DFM (design for manufacturability), which verifies the design can be manufactured efficiently and cost-effectively; and SPICE (simulation program with integrated circuit emphasis), which simulates the behavior and performance of the circuit under different conditions. Doing so will help ensure your design meets your expectations and avoids common issues that may cause fabrication errors.

2 Fabrication inspection

Once your fabricated PCBs have been received from the service provider, it's important to inspect them for any physical defects or damage that may have occurred during production. Visual or automated tools can be used for fabrication inspection, such as automated optical inspection (AOI), which uses cameras and software to scan the PCB surface and detect any defects. Automated x-ray inspection (AXI) is another option, as it uses x-rays and software to scan the PCB layers and detect any defects that are not visible to the naked eye. In-circuit test (ICT) and functional test (FCT) are also available, as ICT uses probes and test equipment to measure the electrical characteristics of the PCB and its components, while FCT uses a test fixture and software to simulate the actual operation of the PCB and its components.

3 Reliability testing

Verifying that your fabricated PCBs are free of defects and function properly is essential, but it is also important to test them for their reliability and durability under different environmental and operational conditions. To do this, you can use methods such as HALT, HASS, ESS, and burn-in test. HALT exposes the PCB to extreme levels of stress, such as temperature, vibration, humidity, and power cycling. HASS uses a lower level of stress than HALT but still higher than the normal operating conditions. ESS tests the PCB’s ability to withstand environmental conditions like temperature, humidity, shock, and vibration. Finally, the burn-in test operates the PCB at a high temperature and voltage for a prolonged period of time. Testing PCBs before and after fabrication is critical for ensuring the quality and functionality of your electronic devices. By utilizing the right methods and tools for each stage of the design and production process, you can prevent costly rework, reduce failures, and boost customer satisfaction.