Principle of SMT chip function tester
Although a variety of new detection technologies emerge endlessly, such as AOI, X-ray inspection, and online testing of electrICal efficiency based on flight probes or needle beds, They can effectively find all kinds of defects and faults during the test process, but cannot evaluate them Whether the system composed of the whole circuit board can work normally Function test can test whether the whole system can achieve the design goal It takes the unit under test on the circuit board as a functional body, provides input signals to it, and detects output signals according to the design requirements of the functional body This test is to ensure that the circuit board can work properly according to the design requirements Therefore, with the development of various advanced testing technologies, functional testing is still the main method to detect and ensure the final functional quality of products The functional tester usually consists of three units: adding stimulus, collecting response and evaluating the response of the test component according to the response of the standard component Most functional tests have diagnostic procedures that can identify and determine faults Function tester is relatively expensive The SIMplest function test is to connect the surface mounted circuit board to the corresponding circuit of the equipment and observe the working state of the equipment after power on The method is simple and less investment, but it can not automatically diagnose faults

1. Functional test principles
The function test usually tests the board under test through its external interface. The test principle is that the test equipment itself provides various excitation signal sources to stimulate the board under test through the interface, and the test equipment receives and responds to the response signal of the board under test. Compare the signal with the expected result, and finally judge the function. UUT is the test object, which can be a single board or a motherboard; The input is the input signal of the board under test; The output is the output signal of the board under test; The stimulator is an analog part, which provides power supply, slot signal, clock, control signal and status for UUT signal. The controller is the control part, which can be a serial port, an expansion bus, etc., used to control the UUT; The detector is the detection part, which is used to test the output signal of the unit under test; The fixture is a flexible fixture used to secure the UUT.
SMT patch processing 010
Circuit board
2. Features of functional test
Function test is mainly used for batch production. Its purpose is to test the hardware functions from the external interface of the board, not to test the right and wrong, good and bad, all branches of software and boards of the Board Design. Overall effectiveness. The prEMIse of the function test is that the default board design is successful, but some boards are damaged in the production process for various reasons, resulting in failure to work properly. The function test can eliminate these defective boards. The functional tester usually only needs to make the connector or fixture correspond to the test object. As long as the external interface remains unchanged, the original tester can be used for a new test board and only needs to upgrade the software. This functional tester has a strong ability to adapt to changes in the test board. The function tester is generally similar to the whole machine environment. After the single board is allowed to work normally, it tests its input and output signals, comprehensively detects its hardware quality, and has high test reliability. However, since the test is carried out on the interface, the fault location is ambiguous, and the quality of some functions of the circuit board can only be judged. If you want to find a specifIC chip, further analysis is required.
About SMT patch function tester
3. Differences between functional testing and online testing
Test system usually includes online test system and functional test system. Online testing is generally used to find out the failure of components and connections of the board under test. The purpose of functional testing is to test whether the whole machine or the board can work normally and whether the number of functions meets the requirements. The online testing system and the functional testing system complement each other and jointly complete the product testing task. In the production system, the finished board must be tested online. Finished boards are aged at high temperature, and then put into storage after functional test. Before shipment, each single board must pass the overall environmental test. In general, it is necessary to determine whether to use online testing or functional testing according to the complexity, output, output and maturity of the product. For some circuit boards with very simple functions, you can usually consider using only functional tests. If the product is more complex, high-yield, high-yield and mature, online test equipment and functional test equipment are required. No matter whether the product has passed the online test and functional test, it must be debugged by the whole machine before shipment to ensure the efficiency of the whole machine.

The above is the explanation given by the editor of PCB circuit board company.
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