Everything About In-Circuit Testing
The Importance Of ICT Testing
In the electronic products in the factory before production, a formal and professional SMT manufacturer will have multiple rounds of product testing. The more critical tests are AOI visual test, In Circuit testing, FT functional test, laboratory limit test, etc.
ICT in-circuit testing, the first test after SMT component placement, is a standard method to check manufacturing defects and component defects, mainly by testing in-circuit components’ electrical properties and connections. It detects individual elements online and the open and short circuits of the circuit network. Simple operation, fast and quick, and fault location characterize it.
Difference Between Flying Probe Test And Bed Of Nails Fixture ICT Test
* Flying Probe
A flying probe is a machine applied for the flying probe testing method. This method can check the signals one by one, and the total testing time is around 1 to 3 minutes.
The advantage of flying probe testing is that there is no need for fixed testing tools, which means a low cost. The delivery time is short, so this test method is suitable for PCB prototyping.
* Bed Of Nails Fixture
A bed of nails is a tool for fixture tests. This testing method usually requires 5 to 10 seconds for each PCB. It is necessary to make a test fixture for each type of PCB, so it is not a good choice for PCB prototypes. The advantage of the fixture test is that the process is fast and accurate. What’s more, the bed of nails is reusable, so it is suitable for batch production.
Steps Of In-Circuit Testing
The first step is to carry out the open circuit and short circuit test on top of the circuit board.
If the circuit board is not a problem, the components test; the test system will test the resistors, capacitors, inductors, diodes, transistors, and other independent components. Diodes and transistors in this step are mainly carried out in positive and negative conductivity tests to determine whether the diode and transistor paste reverse or paste the wrong.
Due to the board test pinpoint distribution and board size restrictions, You can’t test all discrete components, so the need for modular testing, that is, a local circuit test, to verify the goodness or badness of this part.
Technicians complete the above three parts of the test if the product is not powered, called the Unpowered test. In the unpowered test passed, the product will be powered on the test, that is, the test system in the product power supply port to the product power, so that the product into the charged state, the power process is controlled by the software.
After power is on, technicians will test the product for voltage at important voltage points, do transistor switching characteristics test, chip input and output port high and low-level test.
If the first five parts of the test are okay, the system will start writing the program to the central control chip of the product. This process is called programming. Depending on the product function, programming steps are not required for all products.
After the programming is completed, the main control chip of the product will start to work and drive the whole outcome to work at the same time.
After the product works up, some devices will be tested, such as an extensive capacitance-voltage test, angle sensor test, etc. Technicians can only test these periods as long as the product is running.
If there is no problem with the power-up test process, the system will start to power down the product. Then discharge the energy stored inside the large capacitor on the product, and finally prompt the test to pass.
After the ICT online test will also be functional testing, which will focus on the product function, multiple testing of qualified products will flow into the market. So customers use regular manufacturers of electronic products. There is no need to worry about whether they will buy products that technicians have not tested.