Integrated Circuit Technology Summary (I): Methods for Distinguishing Good from Bad

　　Integrated Circuit (IC) refers to an advanced microelectronic device that integrates many microelectronic devices on a chip. Silicon is usually used as the basic material, and N-type and P-type semiconductors and PN junctions are formed on it through diffusion or penetration technology. There are also chips based on gallium arsenide (GaAs) in the laboratory, which have far better performance than silicon chips, but are difficult to mass produce and are too expensive.

　　An integrated circuit is a semiconductor integrated circuit, that is, an intermediate product or final product that uses semiconductor material as a substrate, integrates two or more components, at least one of which is an active component, and some or all of the interconnection circuits in or on the substrate to perform a certain electronic function;

　　The types of integrated circuits are generally classified by the number of electronic components such as transistors they contain.

　　SSI (Small Small Integrated Circuit), transistor count 10~100

　　MSI (Medium-Scale Integrated Circuit), 100~1,000 transistors

　　LSI (Large Scale Integrated Circuit), number of transistors 1,000~10,0000

　　VLSI (very large scale integrated circuit), transistor count 100,000~

　　An integrated circuit layout design refers to a three-dimensional configuration of two or more active components and part or all of the interconnection lines in an integrated circuit, or a three-dimensional configuration prepared for the manufacture of an integrated circuit.

　　Methods for judging whether an integrated circuit is good or bad.

　　1. Off-Road Detection

　　This method is performed when the IC is not soldered into the circuit. In general, a multimeter can be used to measure the forward and reverse resistance values ​​between each pin corresponding to the ground pin, and compared with the intact IC.

　　2. On-road detection

　　This is a method of testing the DC resistance of each IC pin in the circuit (IC in the circuit), the AC and DC voltage to ground, and the total working current through a multimeter. This method overcomes the limitation of the substitution test method that requires a replaceable IC and the trouble of disassembling the IC, and is the most commonly used and practical method for testing ICs.

　　1. DC working voltage measurement

　　This is a method of measuring the DC supply voltage and the working voltage of peripheral components with the DC voltage block of a multimeter under power-on conditions; detecting the DC voltage value of each IC pin to ground and comparing it with the normal value, thereby narrowing the fault range and identifying damaged components. Pay attention to the following eight points when measuring:

　　(1) The multimeter should have a sufficiently large internal resistance, at least 10 times greater than the resistance of the circuit being measured, to avoid large measurement errors.

　　(2) Normally, turn each potentiometer to the middle position. If it is a TV, the signal source should use a standard color bar signal generator.

　　(3) Anti-slip measures should be taken for the test leads or probes. Any instantaneous short circuit can easily damage the IC. The following method can be used to prevent the test leads from slipping: Take a section of bicycle valve core and put it on the tip of the test lead, and extend it about 0.5mm beyond the tip of the test lead. This can not only make the tip of the test lead contact well with the tested point, but also effectively prevent slipping, and there will be no short circuit even if it touches the adjacent point.

　　(4) When the measured voltage of a certain pin is inconsistent with the normal value, it is necessary to analyze whether the pin voltage has a significant impact on the normal operation of the IC and the corresponding changes in other pin voltages to determine the quality of the IC.

　　(5) The IC pin voltage will be affected by peripheral components. When the peripheral components leak, short-circuit, open-circuit or change value, or the peripheral circuit is connected to a variable resistance potentiometer, the position of the potentiometer sliding arm will change, which will cause the pin voltage to change.

　　(6) If the voltage of each pin of the IC is normal, it is generally considered that the IC is normal; if the voltage of some pins of the IC is abnormal, you should start from the point where the voltage deviates most from the normal value and check whether there is any fault in the peripheral components. If there is no fault, the IC is likely to be damaged.

　　(7) For dynamic receiving devices, such as televisions, the voltages of the IC pins are different when there is a signal or not. If the voltage of the pins that should not change changes greatly, and the voltage of the pins that should change with the signal size and the position of the adjustable components does not change, it can be determined that the IC is damaged.

　　(8) For devices with multiple working modes, such as video recorders, the voltages of each IC pin are different in different working modes.

　　2. AC working voltage measurement method

　　In order to understand the changes of IC AC signals, you can use a multimeter with a DB jack to approximate the AC working voltage of the IC. When testing, the multimeter is set to the AC voltage block and the positive probe is inserted into the DB jack; for multimeters without DB jacks, a 0.1-0.5μF DC blocking capacitor needs to be connected in series with the positive probe. This method is suitable for ICs with lower operating frequencies, such as the video amplifier stage and field scanning circuit of a TV. Since these circuits have different inherent frequencies and waveforms, the measured data are approximate values ​​and can only be used for reference.

　　3. Total current measurement method

　　This method is to judge the quality of IC by detecting the total current of IC power supply line. Since most of the internal IC is directly coupled, when IC is damaged (such as a pn junction breakdown or open circuit), it will cause the subsequent stage saturation and cutoff, causing the total current to change. Therefore, the quality of IC can be judged by measuring the total current. It is also possible to measure the voltage drop of the resistor in the power supply path and calculate the total current value using Ohm's law.