Four Testing Methods of PCB Bare Board

PCB board AKA printed circuit board is an important electronic component. The quality of PCB determines the quality of electronic products to a large extent. Therefore, in the process of producing PCB boards, inspection is a very important part. Through inspection, it is usually possible to find open circuit, short circuit and other defects that affect the function that are not easy to find visually.
For any designed product to be ultimately successful, it must be tested many times. PCB circuit board testing can minimize major problems, find smaller errors, save time and reduce overall costs.
PCB testing is primarily used to mitigate issues throughout the manufacturing process as well as the final production process. These types of tests can also be used on prototypes or small-scale assemblies, which can help identify potential problems that may exist in the final product.

Four testing methods of PCB bare board

01 AOI test:

AOI automatic optical inspection equipment has been widely used in various industries. In the process of PCB manufacturing, as important inspection equipment, AOI test are also widely used.
AOI is also called mid-test in the PCB production process. It tests the circuit pattern after etching the copper foil on the PCB. The equipment scans the graphics on the board and compares it with the design documents, distinguishes the PCB surface graphics status, and then compares it with the PCB surface graphics data registered by the AOI itself. If there is a difference, the defect will be reported, and finally confirmed by the inspector.

02 Flying probe test:

Flying probe testing is a well-recognized and effective form of testing for finding production quality issues, and flying probe testing has been proven by the industry to be a particularly cost-effective test method for circuit boards.
Flying probe tests use two or more independent probes and are run without fixed test points. These probes are electromechanically controlled and move according to specific software instructions. Therefore, the initial cost of the flying probe test is lower, and the test efficiency is not high compared with the fixture test. After all, the flying probe test is a point-by-point test of moving the probe, so it is practical for the test for small batch PCB orders. 

03 Fixture test:

The Fixture is a special jig designed for a particular PCB board for electrical performance on-off testing. There are single-sided jigs and double-sided jigs.
PCB electrical test first needs to make a set of test fixtures, connect the pads or test points on the PCB board through the metal probes of the fixture, and obtain the voltage value, current value and other typical values of the test circuit when the PCB board is powered on. So as to observe whetherthe tested circuit is connected normally. The advantage of using electrical testing is that the testing efficiency is high, and the disadvantage is that the cost is also high. Each PCB requires a different test fixture. Therefore, the fixture test is suitable for large-scale orders.

04 Manual visual inspection:

Visual inspection is the most traditional inspection method, with the advantages of low initial cost and no test fixtures. Judge whether the pcb board is qualified by visual inspection using a magnifying glass or a calibrated microscope and determine when corrective action is required.

Visual inspection are only for boards with simple circuits, and the disadvantages are subjective human error, high long-term cost, discontinuous defect detection, and difficulty in data collection. As PCB production increases and shrinking of wire spacing and component volumes on PCBs, visual inspection methods are becoming less and less feasible.

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