How to detect integrated IC chip? To judge good or bad, please remember these points

Date：2021-12-24 11:50:58 Views：3793

The chip is generally not broken. If it is broken, the most common is breakdown damage. You can use a multimeter to measure the resistance or voltage of the power supply end of the chip to the ground. Generally, if it is within tens of ohms or the power supply voltage is lower than the normal value, most of it can be regarded as breakdown damage. You can disconnect the power supply end and measure whether the power supply is normal. If the measured resistance is large, it is likely that other ports are damaged. You can also measure other ports one by one. See if there is a port shorted to ground.

First of all, because IC is the integration of basic electronic components, it can not simply judge its quality like testing transistors. If you are not familiar with the functions and pin definitions of IC, you should use the IC manual; Otherwise, only according to the application of IC in the circuit, test whether other pins except the power supply pin are open circuit or breakdown to the power supply, and whether the pins are mutually breakdown, so as to roughly judge whether the IC is damaged;Secondly, when testing integrated circuits with a multimeter, it can only be packaged with small ICs, such as thick film, dip, pcdip, SOP, etc. if it is packaged with large-scale digital integrated circuits, such as PGA, BGA, etc., it is incompetent to use a multimeter;Thirdly, if it is an IC sensitive to static electricity, it is best not to simply test with a multimeter without static protection measures to prevent damage to the circuit.

If it is powered on, it can be inferred whether it is input or output according to external components or lines. Generally, the DC resistance method can be used to measure the forward and reverse resistance between each pin corresponding to the grounding pin, and compare it with the intact integrated circuit. The replacement method can also be used to insert the suspicious integrated circuit into the position of the integrated circuit of the same model of normal equipment to determine its quality.

When detecting the integrated circuit in the circuit, you need to pay attention to the following problems.

1. Understand the working principle of integrated circuits and related circuits before testing

Before checking and repairing the integrated circuit, first be familiar with the function, internal circuit, main electrical parameters, the function of each pin, the normal voltage and waveform of the pin and the working principle of the circuit composed of peripheral components. If the above conditions are met, the analysis and inspection will be much easier.

2. The test shall not cause short circuit between pins

When measuring the voltage or testing the waveform with an oscilloscope probe, the lead or probe shall not cause a short circuit between the pins of the integrated circuit due to sliding, and it is best to measure on the peripheral printed circuit directly connected with the pins. Any instantaneous short circuit is easy to damage the integrated circuit. Be more careful when testing CMOS integrated circuits in flat package.

3. It is strictly prohibited to use grounded test equipment to contact live TV, audio, video and other equipment on the base plate without isolation transformer

It is forbidden to directly test TV, audio, video and other equipment without power isolation transformer with instruments and equipment with grounded shell. Although general tape recorders have power transformers, when contacting special TV or audio equipment with large output power or little understanding of the nature of the power supply used, first make sure whether the chassis of the recorder is charged, otherwise it is very easy to cause power short circuit with TV, audio and other equipment charged on the bottom plate, affect the integrated circuit, and further expand the fault.

4. Pay attention to the insulation performance of electric soldering iron

It is not allowed to use soldering iron for welding with electricity. To confirm that the soldering iron is not charged, it is best to ground the shell of the soldering iron. Be more careful with MOS circuit. It is safer to use 6 ~ 8V low-voltage soldering iron.