Introduction of ICT testing technology in PCBA testing
The ICT test mainly USES the test probe to contact the test point on the PCBA board, which can detect the fault problems such as short circuit, open circuit and component welding.Can quantitatively on the resistor, capacitor, inductor, crystal and other device to measure, the diode, triode, light lotus root, transformers, relays, operational amplifier, power supply module function test, for small and medium scale integrated circuit function test, such as all 74 series, the Memory type, commonly used driver IC, exchange, etc.
Some methods of ICT testing are;
1. Simulator test
Use operational amplifiers for testing.The concept of “virtual land” from point “A” is as follows:
∵ Ix = Iref
∴ Rx = v/where V0 * Rref
Vs and Rref are respectively excitation signal source and instrument calculation resistance.If V0 is measured, then Rx can be calculated.If the Rx to be measured is capacitance and inductance, then Vs ac signal source, and Rx is impedance form, C or L can also be obtained.
2. Vector test
Vector (Vector) was used to test the digital IC.The vector test is similar to the truth table measurement, the input vector is excited, and the output vector is measured.For example: testing with non-gate
For the test of the analog IC, the voltage and current can be excited according to the actual function of IC, the corresponding output can be measured and tested as a function block.
3. Non-vector test
With the development of modern manufacturing technology and the use of vlsi, it often takes a lot of time to write the vector test program of the device. For example, the test program of 80386 takes nearly half a year for a skilled programmer.A large number of SMT devices make the failure of pin opening become more prominent.For this purpose, Teradyne launched MultiScan;The non-vector test technique of Xpress by GenRad.
ICT test is at the back end of the production link, and the first process of PCBA test can timely discover problems in the production process of PCBA board, which is conducive to improving the process and improving the efficiency of production.PCBA testing
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