Thermal fatigue and failure of electronic power device substrates

Abstract

Electronic power devices used for transportation applications (automotive and avionics) experience severe temperature variations, which promote their thermal fatigue and failure.For example, for power modules mounted on the engine of an aircraft, temperature variations range from -55°C (in the worst case of storage before takeoff) to +200°C (flight). Direct bonded copper (DBC) substrates are used to isolate chips (silicon dies) from their base plates. For large thermal amplitudes, the failure occurs in DBC substrates, which are copper/ceramic/copper sandwiches.The Weibull approach was used to model the brittle fracture of the ceramic layer from a natural defect. Furthermore, geometric singularities in the upper ceramic/copper interface are at the origin of cracks that grow by fatigue along the interface and finally bifurcate and break the ceramic layer.It is discussed how the framework of linear elastic fracture mechanics (LEFM) can be used to characterize the stress field around singularities and the associated risk of failure. These two criteria and the finite element method, allow analysing how a thermal loading history may modify the risk of failure of DBC substrates. It was shown, in particular, that three overcooling cycles should produce an "overload retardation effect". Experimentally, applying 3 "overload cycles" (-70°C,+180°C), prior to thermal fatigue cycles (-30°C, +180°C), increased very significantly the fatigue life of DBC substrates. This result shows that the fatigue life and the reliability of power electronic devices could be optimized using a thermo-mechanical approach of the problem and suitable failure criteria.

Characterisation of power modules ceramic substrates for reliability aspects

“…In those cases, it was shown that the stress field can be represented by the product of a shape function r k f ðhÞ and of a generalized stress intensity factor K. Various authors [7] have employed generalized stress intensity factors successfully to characterize stress fields in the vicinity of singularities that are not cracks. It has been already shown in a precedent paper that the singularity k of the stress field in the studied problem can be considered as equal to that of an ideal crack in an homogeneous media (k = 0.5) [8]. With that hypothesis, it becomes possible to extract the mode I and mode II stress intensity factors by correlating the displacement fields in the ceramic layer using the Westergaard displacement functions.…”

Processamento, propriedades e aplicações das cerâmicas de nitreto de alumínio

“…Os módulos de potência, principalmente os fabricados pela tecnologia DBC, trabalham em uma extensa faixa de temperatura de -55 a +200 ºC [86]. Estes dispositivos eletrônicos são susceptíveis à falha por fadiga térmica porque utilizam materiais (por ex., Cu, AlN e Si) com diferentes coeficientes de expansão térmica [38,86,87].…”

“…Estes dispositivos eletrônicos são susceptíveis à falha por fadiga térmica porque utilizam materiais (por ex., Cu, AlN e Si) com diferentes coeficientes de expansão térmica [38,86,87]. Outros dispositivos eletrônicos, como os lasers de alta energia, são susceptíveis à falha por choque térmico porque apresentam problemas de gerenciamento térmico, sendo esta falha minimizada pela utilização de materiais com boas propriedades mecânicas e térmicas [88].…”

Application of Kriging and radial basis function in power electronic module wire bond structure reliability under various amplitude loading

“…Polynomial P is usually a lower order polynomial, in this paper we uses a linear form The radial basis reduced order model for the accumulated plastic strain on aluminium wire bond slice attached to the silicon chip R ep is R ep ðT delta ; T mean Þ ¼ À32:0322 þ 93:0576T delta þ 6:5957T mean þ X n i¼1 r ep i e À0:01h 2 i ð10Þ where i = 1, ..., n (n = 12 DoE as in the Table 4), h i is as in Eq. (8) and the values of the coefficients are listed in Table 5.…”

“…This conchodal fracture failure has been modelled using FEA by Lu et al [7]. Another approach using probability calculation with FEA to predict the failure of conchodal fracture is reported in [8]. In [9] FEA simulation is used to study thermal fatigue effect of combination of various substrates with various solder materials in a power module.…”