PCB testing
PCB testing and inspection are essential to ensure top-quality products and minimize product defects. These tests are conducted during every stage of the manufacturing process, from board bring-up to functional test, to identify any issues that may have occurred. This can help you catch flaws and errors quickly, saving time and money in the long run.
The primary methods of PCB testing and inspection are In-Circuit Testing (ICT), Flying Probe Test, and Functional Test. These tests simulate the environment in which a PCB will operate by applying signals to it and measuring the resulting responses. They can also be used to diagnose any problems detected in the circuit board and determine their root cause. ICT is the most commonly used method of PCB testing and inspection. It involves powering up the circuit board and applying signals to it. ICT can also be used to program nonvolatile memory components on the PCB and to exercise boundary scan test features.
Another common method of pcb testing and inspection is optical inspection. Optical inspection uses multiple 2D or 3D cameras to optically analyse the board and compare images of it against a detailed schematic. This can be used to spot defects such as missing or misplaced devices, incorrect connections between traces, and incomplete soldering. Optical inspection is usually only possible when the board is not powered and can only detect surface mount devices, not through-hole components.
What are the primary methods for PCB testing and inspection?
For PCBs with a large number of through-hole components, a special type of inspection called burn-in testing can be useful. This test is designed to simulate a typical operating environment by subjecting the board to extreme conditions such as high temperatures and voltages, mechanical stress, and environmental factors such as humidity and vibration. This test helps to identify any problems that would otherwise be difficult to detect, and it can also help predict a component’s life cycle.
Other types of PCB testing and inspection include X-ray inspection, automated optical inspection, and functional test. X-ray inspection can be used to check for internal layers of the PCB and to locate defects such as an annular ring (a ring of copper around a plated through hole), a v-score (a partial cut through the board) or untented vias (holes that are not covered with solder mask). AOI is similar to X-ray inspection, except it is automated and can detect bare copper areas, not just plated parts.
In addition to these physical tests, a thorough PCB inspection can also detect errors in the design software. This includes DRC – design rule checking, which runs a computerised check on the design to ensure that it meets JEDEC guidelines for component placement, soldering, and orientation. It can also detect issues such as traces that touch each other, a drill hole that is too small, and inaccurate drill hits. Using DRC can also help prevent problems from occurring during fabrication, which can save time and money. This is because it can help avoid the need to re-make a part or a whole batch of boards.