How to test the reliability of diodes in communication systems?

1, Testing standards and specification system
The reliability testing of diodes in the communication industry must comply with international authoritative standards, among which Telcordia GR-468 "General Requirements for Reliability of Optoelectronic Devices for Communication Equipment" is the core specification. This standard establishes a detailed reliability verification process for optoelectronic devices (including laser diodes, photodiodes, etc.) used in communication equipment, covering three major modules: device performance testing, stress testing, and accelerated aging testing. For example, GR-468 requires laser diodes to pass a 1000 hour high-temperature and high humidity storage test (85 ℃/85% RH) and meet the criteria of center wavelength drift ≤ 0.5nm and output power attenuation ≤ 5%. In addition, although the AEC-Q102 standard (published by the Automotive Electronics Council) is aimed at automotive optoelectronic devices, its high-temperature reverse bias (HTRB), temperature cycling, and other testing methods are widely used in the communication industry to evaluate the reliability of diodes in extreme environments.
2, Core testing projects and implementation methods
(1) Environmental adaptability testing
Temperature cycling test
Simulate the thermal stress of communication equipment in extreme outdoor environments through rapid temperature changes from -40 ℃ to 125 ℃ (such as switching within 10 minutes). The test needs to last for 1000 cycles, with a focus on issues such as cracked diode packaging and decreased wire bonding strength. For example, the Schottky diode used in a certain communication base station needs to complete 500 cycles within the range of -40 ℃ to 100 ℃, with a forward voltage drop change rate of ≤ 3%.
damp heat
Evaluate the insulation performance of the diode under high temperature and high humidity conditions using 85 ℃/85% RH conditions for 168 hours. After testing, the leakage current (IR) needs to be measured, with a requirement of ≤ 1 μ A (at rated voltage). If the leakage current exceeds the standard, it may indicate a decrease in insulation performance due to moisture absorption of the packaging material.
(2) Electrical performance testing
Positive characteristic test
Measure the forward voltage drop (Vf) using a digital multimeter or diode tester. Communication diodes typically require Vf ≤ 0.4V (such as the SS14 series). Meanwhile, it is necessary to observe the forward recovery time (Tfr) through an oscilloscope to ensure that it meets signal integrity requirements in high-frequency applications.
Reverse characteristic testing
Apply reverse voltage to 80% of the rated breakdown voltage (Vr) and measure the reverse leakage current (Ir). Communication diodes must meet Ir ≤ 10nA (such as BAS70 series) to avoid signal interference. In addition, the transient protection capability of the diode needs to be verified through surge current testing (such as applying 10 times the rated current for 10 μ s).
(3) Accelerated Life Test
High temperature reverse bias (HTRB) test
Apply reverse voltage (such as 80% of rated voltage) at 125 ℃ for 1000 hours. Predicting failure rate through Weibull distribution model requires failure rate ≤ 100FIT (million hours of failure). For example, the TVS diode in a certain communication module needs to pass the HTRB test and meet the ESD protection capability of ± 8kV (HBM model).
Temperature cycling accelerates aging
Combined with temperature cycling from -55 ℃ to 150 ℃ and electrical stress, accelerate the exposure of potential failure modes. After testing, failure analysis (FA) is required, such as scanning electron microscopy (SEM) observation of metalization layer migration, X-ray detection of wire bonding voids, etc.
3, Testing methods and tool selection
(1) Automated testing system
The communication industry generally uses ATE (Automatic Test Equipment) to achieve batch testing. For example, the Keysight B1500A semiconductor parameter analyzer can integrate functions such as IV curve scanning and C-V characteristic testing. A single device can simultaneously test 200 diode samples, increasing testing efficiency by more than 5 times.
(2) Failure analysis techniques
Physical Failure Analysis (PFA)
Locate the failure point through methods such as opening, removing layers, staining and infiltration. For example, a 5G base station diode experienced an increase in leakage current after HTRB testing, and PFA revealed the presence of voids at the interface between the metallization layer and the silicon substrate, leading to local breakdown.
Electrical Failure Analysis (EFA)
Use emission microscopy (EMMI) to locate hot spots, or detect current leakage paths through beam induced resistance change (OBIRCH) technology. For example, the sensitivity of the PIN diode in a high-speed optical communication module decreased, and microcracks were found at the edge of the PN junction through EFA.
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