Chip detection knowledge

Common sense

1. Before testing, you should understand the working principles of integrated circuits and its related circuits. Before repairing and repairing integrated circuits, you must first be familiar with the functions of the integrated circuit used, internal circuits, main electrical parameters, the role of each pin, and the normal voltage, waveform of the pin, waveform, waveform, waveform, waveform,The working principle of a circuit with peripheral components.If you have the above conditions, analysis and inspection will be much easier.

2. Do not cause a short -circuit voltage measurement between the pins or test the waveform with a oscilloscope probe, the table pen or probe should not be short -circuited between the integrated circuit pins due to sliding. It is best to measure on the peripheral printing circuit directly connected to the pin.Any short circuit at any moment is easy to damage the integrated circuit. When testing the CMOS integrated circuit that is packaged flat -type packaging, be more careful.

3. It is strictly forbidden to use the ground -to -ground testing equipment without an isolated transformer to contact the TV, audio, video and other equipment that is charged with the bottom plate.equipment.Although the general conclusion machine has a power transformer, when it comes to contact with a special TV or audio equipment that is more special, especially the larger output power or the nature of the power supply.Television, audio and other equipment with the bottom plate causes short circuits of power supply, which affects integrated circuits, and further expands the fault.

4. Pay attention to the insulation performance of the electric soldering iron. It is not allowed to use the soldering iron welding with electricity. It is necessary to confirm that the soldering iron is not charged. It is best to ground the shell of the soldering iron. It should be more careful about the MOS circuit. It can be safer to use 6 ~ 8V low -voltage circuit iron.

5. It is necessary to ensure that the welding quality is really welded, and the accumulation and pores of the weld are easily welded.The welding time generally does not exceed 3 seconds, and the power of the soldering iron is about 25W.The welded integrated circuit should be checked carefully. It is best to use the Ohm table to measure whether the pins are short circuit to confirm that there is no welding adhesion and then connect the power.

6. Don't easily determine the damage of the integrated circuit. Don't easily judge that the integrated circuit is damaged.Because the vast majority of integrated circuits are directly coupling, once a certain circuit is abnormal, it may cause multiple voltage changes, and these changes are not necessarily caused by damage to the integrated circuit. In addition, in some casesWhen the value is consistent or close, it may not necessarily indicate that the integrated circuit is good.Because some soft faults do not cause changes in DC voltage.

7. When the test instrument is internal resistance to large measurement of the integrated circuit pins, the universal meter with an internal resistance of the surface should be used, otherwise there will be a large measurement error on certain pins voltage.

8. Pay attention to the heat dissipation power integrated circuit of the power integrated circuit should be well dissipated, and it is not allowed to work in a high power state without a heat sink.

9. If the lead is reasonable, if you need to add peripheral components instead of the damaged part inside the integrated circuit, a small component should be selected, and the wiring should be reasonable to avoid unnecessary parasitic coupling, especially to handle the audio workplace integrated circuit and front amplificationThe ground end between circuits.

Method of identification