Thermal cycling reliability of lead free solders for automotive applications

Abstract

The solder joint reliability of ceramic chip resistors assembled to laminate substrates has been a long time concern for systems exposed to hush environments such as those found in automotive and aerospace applications. This is due to a combination of the extreme t e m p e r a m excursions experienced by the assemblies along with the large coefficient of thermal expansion mismatches between the alumina bodies of the chip resistors and the glass-epoxy composites of the printed circuit boards (PCBs). These reliability challenges are exacerbated for components with larger physical size (distance to neutral point) such as the 2512 resistors used in situations where higher voltages and/or currents lead to power dissipations up to 1 Wan. In this work the thermal cycling reliability of several 2512 chip resistor lead free solder joint configurations has been investigated. In an initial study, a comparison has been made between the solder joint reliabilities obtained with components fabricated with both tin-lead and pure tin solder terminations. In the main portion of the reliability testing, two temperature ranges (-40 to 125 "C and -40 to 150 "C) and five different solder alloys have been examined. The investigated solders include the normal eutectic SnAgCu (SAC) alloy recommended by earlier studies (95.5Sn-3.8Ag-O.7Cu), and three variations of the lead free ternary SAC alloy that include small quaternary additions of bismuth and indium to enhance fatigue resistance. For each configuration, thermal cycling failure data has been gathered and analysed using two-parameter Weibull models to rank the relative material performances. The obtained lead free results have been compared lo data for standard 63Sn-37Pb joints. In addition, a second set of thermally cycled samples was used for microscopy studies to examine crack propagation, changes in the microstructure of the solders, and intermetallic growth at the solder to PCB pad interfaces.

Reliability Comparison of Aged SAC Fine-Pitch Ball Grid Array Packages Versus Surface Finishes

“…The resistors used in this research will be referred to as 2512. Suhling et al [11] reported that chip resistors fabricated with 90Sn-10Pb solder terminations match the S63n-37Pb solder paste better and avoid fillet lifting. Pure Sn terminations had been recommended as a part of the overall Pb-free initiative.…”

Lifetime Prediction of Boost, Z-source and Y-source Converters in a Fuel Cell Hybrid Electric Vehicle Application

“…The different sources are discussed in [1] in details. The sources of failure, which have been identified are vibration [39], humidity, thermal cycles [40], [41], and [20], power cycles [42], voltage and current stresses. 11 Part 1.…”

“…As shown in Fig.1.7, where the red squares refer to the failed components, and the green squares refer to different stressors. It is concluded that the IGBT and chip resistors are critical components according to these specific different research activity in the literature [45], [46], [47], [48], [49], [20], [50], [42], [51], [40], [52], [53], [26], [54], [55], [56], [57], [39], [58], [59], [60], [61], [62], [63] and [64]. It can be concluded from this figure that the thermal cycles are a very common source of failure in the power electronics of the electro-mobile applications.…”

Comparing and Benchmarking Fatigue Behaviours of Various SAC Solders under Thermo-Mechanical Loading

“…FEM has become the common tool used in the analyses of solder joint fatigue failure and reliability in the electronics industries [23]- [26]. During exposure to thermal cycling, fatigue is mainly due to the thermomechanical stresses in the solder joints arising from the differences in the CTE between PCB and components [27], [28]. Awareness and knowledge of the failure mechanisms of these systems are necessary for preventing accidents [29] and the cyclical variation of thermal stress effects solders joint thermal fatigue failure.…”