Online needle bed test method ICT. In the actual pcb assembly and manufacturing, in addition to the solder joint quality is not qualified, which will lead to welding defects, component polarity is wrong, component types are mislabeled, and the value exceeds the nominal allowable range, which may lead to SMA defects. ICT is a contact test method. Therefore, it can directly pass the on-line test ICT for performance test in production, and at the same time check related defects affecting its performance, including bridging, virtual soldering, open circuit, component polarity misplacement, and numerical tolerance. Etc., and adjust the production process in time according to the exposed problems.
In ICT, the needle bed fixture manufacturing and program development cycle is long, and the price is relatively high. At the same time, due to the limitation of the CNC machine tool of the machining equipment when processing the needle bed clamp, the test probe must be designed on the 2.54mm or 1.27mm grid. The minimum pitch of the probe is 1.27mm, so ICT is suitable for general assembly density, mass production products. The ICT test process is as follows:
(1) ICT test preparation for the circuit board: the test personnel, the board to be inspected, the test equipment, and the test documents should be prepared.
(2) Programming: 1 Under T [Test], set p “test parameters”. The test parameters include the name of the test board, the first test pin number on the fixture, and the number of retests reapear when the open circuit/part is poor; 2 In the E  state, write the program; 3 enter L [learning], do short group learning, if you have IC, you need to do IC Clamping Diode learning
(3) Test procedure: test program under the main screen
(4) Test: test under the main screen
(5) Debugging: When the program is written, due to the selection of the test signal or the influence of the component layout under test, some steps will be judged as invalid, that is, the measured value exceeds the deviation limit and must be debugged.
Flying needle test method. The flying probe test belongs to the contact detection technology and is also one of the test methods in production. The flying probe test uses 4 to 8 independently controlled probes, and the Unit Under Test (UUT) is transported into the test machine through a belt or other UUT transfer system, and then fixed, the probe of the test machine contacts the test pad and A via hole to test a single component of the UUT. The test probe is connected to the driver and sensor through a multiplex system to test the components on the UUT. When a component is being tested, other components on the UUT are electrically shielded by the probe to prevent reading interference.
The flying probe test is the same as the needle bed test. It can also perform electrical performance testing, and can detect defects such as bridging, virtual soldering, open circuit, component polarity misregistration, and component failure. According to the test probe can carry out omnidirectional angle test, the minimum test gap can reach 0.2mm, but the test speed is slow. The flying probe test is mainly suitable for SMA which is not suitable for ICT, such as high assembly density and small lead pitch.
Functional test method. Although various new detection technologies emerge in an endless stream, such as AOI, X-ray inspection, on-line testing of electrical properties based on flying probes or needle beds, these technologies can effectively find various defects and failures that occur during the pcb assembly process, but It is not possible to evaluate whether the system consisting of the entire circuit board is functioning properly, and the functional test can test whether the entire system can achieve the design goal. It uses the unit under test on the surface mount board as a function body, inputs electrical signals, and then detects the output signal according to the design requirements of the functional body. This kind of test is to ensure that the circuit board can be tested according to the design requirements. The main method is to detect and guarantee the final functional quality of the product.
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