Accelerated Temperature Cycling Conditions Research Articles

Probabilistic methodology for reliability assessment of electronic packages

In the mechatronic devices, the finite element analyses are the most used method to determine time-dependent solder joint fatigue response under accelerated temperature cycling conditions, the deterministic analyses are the most used methods. However, the design variables show variability and randomness which will affect the lifetime prediction quality. This paper focuses on solder joint reliability in tape-based chip-scale packages(CSP) with the consideration of uncertainties in material parameters.

BGA Board Level Reliability Analysis & Optimization

The solder joint reliability of semiconductor package interconnects to printed circuit boards is critical for product durability. A dominant failure mode is solder fatigue due to the CTE mismatch between the BGA component and PCB at thermal cycling. However, it is well known that other factors can impact fatigue behavior and time to failure such as solder joint geometry, die geometry, solder system, etc. Finite element modeling (FEM) and simulation can play an integral role in providing deeper insight into the impact of these package parameters on the overall assembly. However, a major challenge of accurately modeling these systems includes simulation of multiple length scales from the package, substrate, and solder joints. The FEM approach addressing these can lead to reduced cycle time, accurate simulation, and improved package performance. In this work, the finite element modeling and simulation procedure is demonstrated for a BGA package at accelerated temperature cycling conditions. At the component level, key details regarding the properties and constituents of the BGA package mold compound and substrate are established by coupling measured experimental warpage data and finite element modeling. Comparison of simulated & Thermoire measurements shows excellent agreement at the package level, with warpage correlation achieved over the entire temperature range. At the assembly level, the truncated sphere model is used to arrive at precise solder joint profiles for accurate representation to tie the package to the board. The combined validated package-level results and solder joint profiles are employed towards a subsequent thermo-mechanical analysis of the full BGA assembly. The entire simulation procedure is demonstrated for a BGA design, where inelastic creep and reliability test data are compared. High strain regions in the solder joint array are shown to compare closely with regions of failure from experimental reliability test data. The validated FEM model allows for extrapolating to similar package conditions allowing faster design cycle time and less time consuming experimental work.

Thermal Cycling Analysis of BGA Solder Joint Reliability

The solder joint reliability of semiconductor package interconnects is critical to product durability. A dominant failure mode is solder fatigue due to the CTE mismatch between BGA component and PCB at thermal cycling. It is well known that besides thermal expansion mismatch of component and board, the solder joint geometry has a great impact on fatigue behavior and time to failure. In this study, a combination of Surface Evolver and finite element analysis are use to predict the solder joint shapes for the assembly of medium pin count BGA's and to estimate the reliability at accelerated temperature cycling conditions. Results of Surface Evolver are compared with the assumption of a truncated sphere. The solder shape predictions are applied for a subsequent thermo-mechanical analysis of the BGA assembly. Inelastic creep deformation is evaluated for critical solder balls, and the Coffin-Manson relation is used to estimate the solder joint lifetime. The entire simulation procedure will be demonstrated for a product design study for high reliability automotive BGA's. A fractional factorial design is defined that considers solder sphere diameter and solder pad sizes on BGA substrate and on PCB side. Resulting creep values and lifetime estimates will be compared.

Effects of package geometry on thermal fatigue life and microstructure of Sn–Ag–Cu solder joint

Soldering experiments of chip scale package devices were carried out by means of diode laser soldering system with Sn–Ag–Cu solders. In addition, pull tests and a scanning electron microscope were used to analyse the effect of processing parameters on mechanical strength of solder joints. Viscoplastic finite element simulation was utilised to predict solder joint reliability for different package geometry under accelerated temperature cycling conditions. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed soldering time, an optimal power and package geometry exists, while the optimal mechanical properties of microjoints are gained.

Thermomechanical reliability characterization of a handheld product in accelerated tests and use environment

Thermomechanical reliability of electronics has commonly been studied by employing accelerated temperature cycling (ATC) tests. However, due to the localized heat dissipation in modern electronic devices, operational power cycling (OPC) is considered a more realistic testing alternative. In order to characterize the thermomechanical reliability of modern high-density electronics, the failure modes, mechanisms and lifetimes of a contemporary commercial handheld device were studied under the ATC and OPC conditions. The experimental measurements and finite element analysis (FEA) showed distinct differences in the thermomechanical response of the device component boards under the OPC and ATC conditions. The results from FEA showed that the interconnection deformations during the OPC test were mostly in the elastic region of the solder, whereas those during the ATC tests reached well into the plastic region. The inclusion of the product enclosure further emphasized this difference, as the enclosure restricted the thermal expansion of the component board during OPC testing. The experimental test results were consistent with the FEA results, as the device failed due to solder interconnection cracking under the ATC conditions within 18 days of testing, but those under the OPC conditions remained operational even after 460 days. Finally, FEA estimations suggest that even three times higher power dissipation levels compared to those found in contemporary handheld devices would result in many years of lifetime in OPC testing.

Cycle Life Prediction for SMT Solder Joints on TCE‐Mismatched Substrates

A method for the prediction of solder joint cycle life in surface‐mount assemblies is presented, based on the conversion of plastic solder shear strain into cycle life by means of an equation derived by Engelmaier. The paper introduces a different analytical procedure for the determination of solder joint shear strain. Shear strain is normally calculated from temperature and TCE differentials between package and interconnect board without consideration of elastic deformations. The suggested method derives average plastic shear strain of the solder joint at maximum temperature excursion from finite‐element analysis of a simple model consisting of an interconnect board, a solder joint and a package. All materials in the model have linear (elastic) properties, except solder which has non‐linear (elastic/plastic) characteristics. The solder stress/strain curve is described to the finite‐element programme with temperature‐dependent bilinear approximations. The solder joint is modelled as a single finite element so that only one value is computed for the plastic shear strain in the solder joint. This value represents the average shear strain which is converted into solder joint cycle life. The cycle life predictions with the finite‐element method are confirmed by cycling results obtained on actual hardware. The described method can serve as a design tool in the optimisation of surface‐mount assemblies. The procedure can help to define accelerated temperature cycling conditions.