Testing techniques for surface mount diodes

In engineering technology, the internal structure of surface mount diodes is basically the same as that of ordinary diodes, both consisting of a PN junction. Therefore, the detection method of surface mount diodes is basically the same as that of ordinary diodes. The detection of surface mount diodes is usually measured using the R × 100 Ω or R × 1 k Ω range of a multimeter.

1. Testing of ordinary surface mount diodes

(1) Positive and negative pole discrimination of ordinary surface mount diodes

The identification of the positive and negative terminals of a surface mount diode is usually done by observing the markings on the diode casing. When encountering severe wear on the casing markings, a multimeter ohm range can be used for identification:

Place the multimeter in the R × 100 Ω or R × 1 k Ω range, first use the red and black probes of the multimeter to measure the resistance between the two pins of the SMD diode, and then swap the probes and measure again. Among the two measurement results, choose the one with the smaller resistance value. The black probe is connected to the positive terminal of the surface mount diode, and the red probe is connected to the negative terminal of the surface mount diode; The measured resistance value is the forward resistance of the surface mount diode (usually several hundred to several thousand ohms), and the other set of resistance values is the reverse resistance of the surface mount diode (usually several tens to hundreds of kiloohms).

(2) Performance evaluation of ordinary surface mount diodes

The detection of the performance of ordinary surface mount diodes is usually carried out in an open circuit state (detached from the circuit board), and the measurement method is as follows:

Measure the forward and reverse resistance of a regular surface mount diode using a multimeter in the R × 100 Ω or R × 1 k Ω range. According to the unidirectional conductivity of a diode, the greater the difference in resistance between its forward and reverse directions, the better its unidirectional conductivity. If the difference in resistance between the forward and reverse directions is not significant, it indicates that the unidirectional conductivity of the surface mount diode has deteriorated; If both the forward and reverse resistances are high, it indicates that the surface mount diode has opened and failed; If both the forward and reverse resistances are small, it indicates that the surface mount diode has broken down and failed. When the above three situations occur in the surface mount diode, the diode must be replaced.