Condition monitoring (CM) has already been proven to be a cost effective means of enhancing reliability and improving customer service in power equipment, such as transformers and rotating electrical machinery. CM for power semiconductor devices in power electronic converters is at a more embryonic stage; however, as progress is made in understanding semiconductor device failure modes, appropriate sensor technologies, and signal processing techniques, this situation will rapidly improve. This technical review is carried out with the aim of describing the current state of the art in CM research for power electronics. Reliability models for power electronics, including dominant failure mechanisms of devices are described first. This is followed by a description of recently proposed CM techniques. The benefits and limitations of these techniques are then discussed. It is intended that this review will provide the basis for future developments in power electronics CM.

Condition Monitoring for Device Reliability in Power Electronic Converters: A Review

The present study contains a critical review of work on the formation of precipitates and intermetallic phases in dilute precipitation hardening Al–Cu–Mg based alloys with and without Li additions. Although many suggestions for the existence of pre-precipitates in Al–Cu–Mg alloys with a Cu/Mg atomic ratio close to 1 have been made, a critical review reveals that evidence exists for only two truly distinct ones. The precipitation sequence is best represented as: supersaturated solid solution→co-clusters→GPB2/S"→S where clusters are predominantly Cu–Mg co-clusters (also termed GPB or GPB I zones), GPB2/S" is an orthorhombic phase that is coherent with the matrix (probable composition Al10Cu3Mg3) for which both the term GPB2 and S" have been used, and S phase is the equilibrium Al2CuMg phase. GPB2/S" can co-exist with S phase before the completion of the formation of S phase. It is further mostly accepted that the crystal structure of S' (Al2CuMg) is identical to the equilibrium S phase (Al2CuMg). Th...

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Precipitates and intermetallic phases in precipitation hardening Al–Cu–Mg–(Li) based alloys

High-temperature structural intermetallics

Pre-precipitate clusters and precipitation processes in Al-Mg-Si alloys

One-step solution-immersion process for the fabrication of stable bionic superhydrophobic surfaces

Precipitation hardening of anAl–4.2 wt% Mg–0.6 wt% Cu alloy

Thermal cycling reliability of SnAgCu and SnPb solder joints: A comparison for several IC-packages.

Mechanical reliability of Au and Cu wire bonds to Al, Ni/Au and Ni/Pd/Au capped Cu bond pads

The precipitation of the (Mn,Fe)Al6 phase during preheating of a commercial AA 5182 Al Mg alloy was studied by means of scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The existence of two different morphologies with low and high aspect ratio (called here rhomboidal and platelike) was confirmed. The influence of preheating parameters on the precipitation was found to be close to the one known for Al-Mn alloys. It was found that the platelike dispersoids bear orientation relationships with the matrix of type [100]m||[2¯10]pp and (0¯11)m||(001)pp, which are not yet reported in the literature. On the other hand it was shown that rhomboidal precipitates do not follow any orientation relationship with the matrix. The more harmful influence on recrystallization and hot ductility of the rhomboidal precipitates compared to the platelike ones is discussed.

Effect of preheat temperature on the orientation relationship of (Mn,Fe)Al6 precipitates in an AA 5182 Aluminium—Magnesium alloy

The reliability and failure modes of eutectic Sn-Ag-Cu solder joints were studied and compared to eutectic Sn-Pb-Ag ones. Two different failure modes occur: brittle fracture and fatigue. The results show that with a Ni/Au surface finish the reliability of Sn-Ag-Cu solder is much better than that of Sn-Pb-Ag solder. First, when the joint is deformed at high thermomechanical strain, the chance of brittle fracture at the Ni-Au interface is significantly reduced when using Sn-Ag-Cu solder. The reason is a reduced formation of the brittle (Au, Ni)Sn/sub 4/ intermetallic at the UBM interface, responsible for the brittle fracture mode. Second, after deformation at low thermomechanical strain, both solders fail due to solder fatigue, but the Sn-Ag-Cu shows a better lifetime. This better reliability of the Sn-Ag-Cu solder is attributed to a new solder fatigue mechanism: the crack propagates through the bulk of the solder in a web-fashion way, linking the Au-containing particles formed in the volume. This is beneficial for the joint reliability as it hinders the crack propagation.

Petar Ratchev

Papers

Precipitation hardening of anAl–4.2 wt% Mg–0.6 wt% Cu alloy

Thermal cycling reliability of SnAgCu and SnPb solder joints: A comparison for several IC-packages.

Mechanical reliability of Au and Cu wire bonds to Al, Ni/Au and Ni/Pd/Au capped Cu bond pads

Effect of preheat temperature on the orientation relationship of (Mn,Fe)Al6 precipitates in an AA 5182 Aluminium—Magnesium alloy

Reliability and failure analysis of Sn-Ag-Cu solder interconnections for PSGA packages on Ni/Au surface finish