Haiyu Qi

No-fault-found and intermittent failures in electronic products

This paper reviews the possible causes and effects for no-fault-found observations and intermittent failures in electronic products and summarizes them into cause and effect diagrams. Several types of intermittent hardware failures of electronic assemblies are investigated, and their characteristics and mechanisms are explored. One solder joint intermittent failure case study is presented. The paper then discusses when no-fault-found observations should be considered as failures. Guidelines for assessment of intermittent failures are then provided in the discussion and conclusions.

Modeling of Combined Temperature Cycling and Vibration Loading on PBGA Solder Joints Using an Incremental Damage Superposition Approach

Concurrent vibration and temperature cycle environments are commonly encountered in the service life of many electronic products, particularly those used in automotive, avionic, and military applications. However, the ability to predict life expectancy under these types of environments remains a technical challenge. In this paper, a traditional linear damage superposition modeling approach and a damage superposition approach that considers the temperature imposed load state on vibration damage are compared with experimental test results for plastic ball grid array (PBGA) assemblies subjected to temperature cycling, vibration loading, and combined temperature cycling and vibration loading conditions. The results showed much earlier PBGA solder-joint failure under combined loading than with either separate temperature cycling or room temperature vibration loading. Traditional linear superposition was found to over-predict the solder-joint fatigue life, since it neglects the interaction effects of two different loadings. The damage superposition approach that considers the temperature imposed load state on vibration damage is found to be more representative of test data.

A Rapid Life-Prediction Approach for PBGA Solder Joints Under Combined Thermal Cycling and Vibration Loading Conditions

While some electronic products are routinely subjected to concurrent vibration and temperature cycle loading, the ability to accurately model and estimate life expectancy of hardware under such conditions still presents a unique challenge. For combined vibration and temperature cycling, one of the most likely causes of failure is the fatigue of solder interconnects. This paper presents an approach to predict solder joint life under combined thermal cycling and vibration loading conditions, by taking into account temperature effects and loading interactions. Combined loading experiment on a test vehicle populated with PBGA packages was used to demonstrate this approach.

Analysis of Solder Joint Failure Criteria and Measurement Techniques in the Qualification of Electronic Products

The specification of a failure criterion for solder joints is an important element in the qualification of an electronic product. A common approach to reliability testing is to monitor electrical resistance during the testing. The techniques employed for resistance monitoring and data acquisition will determine whether information regarding transients or long-term drift is captured by the measurement. This paper reviews and assesses the failure criteria used in industry and academia, focusing on three key attributes: resistance threshold, duration of resistance change, and frequency of changes. An experimental study on thermomechanical fatigue of ball grid array package solder joints was performed to compare measurement techniques and failure criteria.

Design of Experiments for Board-Level Solder Joint Reliability of PBGA Package Under Various Manufacturing and Multiple Environmental Loading Conditions

A design of experiments was conducted to determine the reliability of plastic ball grid array packages under various manufacturing and multiple environmental loading conditions. Parameters included conformal coating methods, underfill, solder mask defined, and non-solder mask defined pads. Board-level temperature cycling, vibration, and combined temperature cycling and vibration testing were performed to quantify the reliability and identify preferred design parameters. Through the main effects and interaction analysis, test results show underfill is the key parameter related to the solder joint reliability improvement. Conformal coat method and printed circuit board pad design are not main effects on solder joint reliability. No interactive relationship exists among these three factors under temperature cycling loading, but some interactive relationship between printed circuit board pad type and the conformal coating method exists under vibration and combined loading conditions.

Effects of Printed Circuit Board Materials on Lead-free Interconnect Durability

This study investigates the effects of printed circuit board (PCB) material on interconnect durability of lead free assemblies. The assemblies involve soldering various packages (array and peripheral) on to FR4, high glass transition temperature (Tg) FR4 and Polyimide (PI) printed circuit boards using Sn3Ag0.5Cu solder alloy. The glass transition temperature of these materials ranges from 130°C to 230°C. Thermomechanical properties, such as elastic modulus and thermal expansion coefficients, of the board materials vary considerably. These properties have a direct impact on the interconnect durability. In this paper, thermomechanical properties are experimentally determined and used for solder joint durability simulation. Two kinds of environmental loadings are simulated: temperature cycling and random vibration loading. The results show that PI board provides a better solder joint durability than FR4 and high TgFR4 under temperature cycling conditions. PI assembly has better durability than FR4 assembly under random vibration. The paper also presents the effect of temperature on the vibration response of the FR4 printed circuit board assemblies. The understanding of these changes can contribute to the study on interconnect durability under combined temperature cycling and vibration loading conditions.

Plastic Ball Grid Array Solder Joint Reliability for Avionics Applications

The solder-joint reliability of plastic ball grid array (PBGA) packages for an avionics application was assessed. The fatigue life under combined temperature cycling and random vibration conditions was initially simulated using analytical models. Further simulation was used to plan an accelerated test and to estimate an acceleration factor between field conditions and test conditions, and experimentally verified. The combination of simulation and experimental results was then used to reassess the solder-joint reliability under field conditions. Based on the simulation and test results, it was estimated that PBGA packages without underfill would not satisfy the long-term life expectation for the avionics application under study. In addition, the experimental results also show that the simple application of linear damage superposition (Miners rule), which neglects the interactions between loads, will underestimate the damage and overpredict the product life. Therefore, calculating the acceleration factor is necessary and cost-efficient for providing the basis of product field reliability assessment

High Cycle Cyclic Torsion Fatigue of PBGA Pb-Free Solder Joints

In this study, a comprehensive experimental and numerical approach was used to investigate high cycle cyclic torsion fatigue behavior of lead-free solder joints in a plastic ball grid array (PBGA) package. The test vehicle was a commercial laptop motherboard. The motherboard was subjected to torsional loading and life tests were conducted. Using finite element analysis (FEA), the test assembly was simulated as a global model and the BGA component was simulated as a local model. Strains measured on the motherboard surface near by the BGA were used to calibrate the FEA models. By combining the life test results and FEA simulations, a high cycle fatigue model for the lead-free solder joints was generated based on the Coffin-Manson strain-range fatigue damage model. This model can now be used to predict the cycles to failure of BGA interconnects for new electronic product design under cyclic torsion loading.

Failure analysis and virtual qualification of PBGA under multiple environmental loadings

To investigate the long term reliability of plastic ball grid array packages in aerospace applications, a design of experiments was conducted to address the assembly process, printed circuit board pad type, underfill, and multiple environmental loadings. This paper discusses the design of experiments and the test results, including the failure analysis. Virtual qualification was also performed to simulate the solder joint reliability under thermal cycling and vibration loadings.

Accelerated testing and finite element analysis of PBGA under multiple environmental loadings

To investigate the long term reliability of plastic ball grid array (PBGA) packages in aerospace applications, accelerated tests were conducted to non-underfilled and underfilled packages under multiple environmental loadings at board level. This paper discusses the test results and the underfill effect on solder joint reliability. Failure modes and sites were identified through failure analysis on test samples. To better understand the thermomechanical behavior of PBGAs under cyclic thermal loading environments, three dimensional FEA models for non-underfilled and underfilled packages were also developed and used to predict the time to failure.