This paper presents a case study of interconnection reliability assessment of a SMT assembly. A predicted usage life distribution of the SMT interconnects of the assembly under investigation is obtained using a simulation and model based approach. The analysis involves 20 BGA and 6 leaded QFP/SOP packages on board. Both types of solder joints in the total number of over 8,000, including the solder ball interconnections of the BGA packages and the gull-wing type SMT solder interconnections of the leaded packages, are modeled and analyzed in this study. With a computer aided approach, an efficient process of design data conversion and FEA modeling is achieved making the approach suitable for implementation in a typical industrial design & development environment. Both temperature variation induced thermal fatigue and random vibration induced high-cycle fatigue are considered in the assessment. Solder interconnects subject to potential failures in field are identified based on fatigue life prediction results obtained from the analysis. Despite the fact that testing environmental conditions are used in the analysis instead of actual usage profiles, this study indicates a potential risk of the current design of the assembly under investigation in failing to meet the targeted product life requirement of 15 years in field.

The third International Symposium on Angiostrongylus and Angiostrongyliasis was held April 8–9, 2010, at the Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. Twenty-nine researchers from 7 countries attended the symposium. The symposium’s theme was “Advances in the disease, control, diagnosis and molecular genetics of the genus Angiostrongylus and angiostrongyliasis.” In discussing the epidemiology of the disease, it was noted the first reported case of human angiostrongyliasis came from Taiwan in 1945. Since then, several outbreaks and >2,800 cases of this disease have been reported worldwide. However, the number of cases is probably underestimated given that many physicians might be unaware of angiostrongyliasis because of its rarity; thus, numerous cases might have gone unreported or unrecognized. Although angiostrongyliasis was mainly prevalent in the Pacific islands and Southeast Asia, increasing numbers of natural foci of the disease have been reported because of increased global trade and travel. Pilar Foronda Rodriguez, University of La Laguna, Spain, reported Angiostrongylus cantonensis in Rattus rattus in Tenerife, Canary Islands, and confirmed the island as a natural focus of this disease (1). Lv Shan, Chinese Center for Disease Control and Prevention, reported natural infection by A. cantonensis in 7 provinces in China, including Fujian, Zhejiang, Hunan, Guangdong, Guangxi, and Hainan, and confirmed these provinces as natural foci. Diagnosis of the infection can be difficult. Recovery of the nematode from an infected patient confirms human angiostrongyliasis. However, the frequency of detecting these nematodes is low. Presumptive diagnosis can be based on clinical symptoms, medical history, and laboratory findings in blood and cerebrospinal fluid. A history of eating intermediate hosts is also crucial for diagnosis of angiostrongyliasis. In 2006, a total of 160 persons, 100 of whom were hospitalized, were associated with an angiostrongyliasis outbreak in Beijing, China. This finding is comparable with the total number of infections recorded in China over the past decade. Chenghong Yin of Beijing Friendship Hospital, Capital Medical University, China, reported the diagnosis criteria of angiostrongyliasis used during the outbreak. The criteria included the following indices: 1) epidemiology, 2) clinical symptoms, 3) complete blood count, 4) cerebrospinal fluid investigation, 5) immunologic examination, 6) imaging examination, and 7) etiologic examination. Etiologically and clinically positive patients were further defined. Any patient showing larvae was definitively etiologically positive, and displaying indices 1–4 were considered clinically positive, and those with indices 5 and/or 6 were considered to be displaying auxiliary signs consistent with angiostrongyliasis. In recent years, immunologic detection of this infection has been rapidly developed. Xiaoguang Chen, Southern Medical University, China, purified the major antigenic protein AC32 from adult A. cantonensis, and constructed an AC32-ELISA kit to detect specific immunoglobulin (Ig) G in serum samples of patients. AC32 of A. cantonensis was subsequently found to be a valuable candidate antigen with high sensitivity and specificity for immunodiagnosis of angiostrongyliasis. Xiaoxian Gan, Zhejiang Academy of Medical Sciences, China, and Praphathip Eamsobhan, Mahidol University, Thailand reported a simple and rapid dot-immunogold filtration assay to detect a specific IgG against A. cantonensis that uses crude extracts from adult A. cantonensis as the antigen and protein A conjugated with colloid gold as the detection marker. This immunoassay was highly sensitive (90.5%, 19/21) and specific (98.0%, 98/100). However, some cross-reactivity against serum samples from patients with Trichinella spiralis infection and schistosomiasis was observed. No cross-reactivity against serum samples from patients with other infections of helminthiasis (e.g., cysticercosis, clonorchiasis, and fasciolopsiasis) or tuberculosis was reported. Therefore, this assay is not only rapid and simple without requiring special instrumentation, but also rather sensitive and specific for the detection of IgG against A. cantonensis infection. There is no specific treatment for angiostrongyliasis. Treatment predominantly relies on symptomatic relief, such as antiinflammatory corticosteroid therapy. Kittisak Sawanyawisuth, Khon Kaen University, Thailand reported a series of studies on the treatment of this disease. In 2000, Sawanyawisuth et al. conducted a prospective, placebo-controlled and double-blind study to assess prednisolone treatment of angiostrongyliasis. Patients in the treatment group were given a 2-week course of prednisolone (60 mg/day), and patients in the control group were given placebo. Results suggested that a 2-week course of prednisolone was beneficial in relieving headache in patients with eosinophilic meningitis. In 2007, a prospective, randomized, double-blind and placebo-controlled study indicated that a 2-week course of albendazole appeared to reduce the duration of headache in angiostrongyliasis. In 2009, they conducted a prospective, randomized and controlled study to compare the efficacy of combined prednisolone/albendazole and prednisolone alone therapies for the treatment of angiostrongyliasis. One hundred four patients were divided into combined treatment and prednisolone alone groups, 53 and 51 patients, respectively. The dosages of prednisolone and albendazole were 60 mg/day taken orally in 3 divided doses and 15 mg/kg/day taken as 2 divided doses after meals for 2 weeks, respectively. However, the results indicated that combined prednisolone/albendazole treatment of patients with angiostrongyliasis was no better than prednisolone alone (2). In conclusion, the corticosteroid treatment was beneficial for the patients, although the role of anthelmintic agents remains inconclusive. Therefore, it was not recommended that albendazole alone should be used for the treatment of angiostrongyliasis. In addition to discussing these recent findings, a cooperative network among researchers and clinicians was established to share data from current and future research projects for the prevention, control and treatment of human angiostrongyliasis. We look forward to the 2012 International Symposium on Angiostrongylus and Angiostrongyliasis, which will be held in Guangzhou, China.

As the information available on the treatment of angiostrongyliasis with a combination of albendazole and dexamethasone is limited, the efficacy of such therapy was assessed using data collected during the 2006 outbreak of angiostrongyliasis in Beijing. In a retrospective and controlled study, 35 patients treated with albendazole-dexamethasone (given 20 mg albendazole/kg and 3 mg dexamethasone daily for 7 days) were compared with 34 controls who were treated only symptomatically (with acetaminophen or other drugs). Compared with the controls, the patients given the combination were less likely to have headaches after 7 days (P = 0·038), tended to have headaches that cleared quicker (P = 0·010), and received fewer doses of acetaminophen (P = 0·036). Since no serious adverse effects were observed, a 1-week treatment with a combination of albendazole and dexamethasone appears both safe and beneficial in the treatment of angiostrongyliasis.

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.

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.

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.

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.

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.

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.

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 (Miner's 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

This paper presents the reliability design-of-experiment and results for an insertion-mount assembly under random vibration loading conditions. The natural frequency and overstress limits were first identified for the test vehicle. The durability of assemblies with Sn37Pb (SnPb) and Sn3.0Ag0.5Cu (SAC) solder joints was compared under aging conditions that vary on temperature and duration: 125degC for 100 hours, 125degC for 350 hours, -55degC for 1000 hours. The effects of aging and printed circuit board pad finishes on solder joint reliability were also investigated. The results show that SnPb solder joints have better performance than SAC solder joints, especially under high-vibration loading conditions and with thermal aging treatment. Pad finishes were also found to contribute to diffusion in assembly reliability but with different trends for differently aged products.

This chapter contains sections titled: Introduction Thermal Fatigue and Thermal Cycling Durability Cyclic Mechanical Stress and Vibration-Induced Solder Joint Fatigue and Solder Joint Durability Lead-free Solder Degradation due to Temperature Ageing and Intermetalllic Compound Formation Electromigration and Tests with Elevated Temperature and Humidity Conditions Low-temperature Effect on Solder Joint Reliability and Tin Pest of Lead-free Solders Long-term Reliability of Lead-free Solders and Tests with Combined Loading Conditions Constitutive Characteristics Appendix A References

Thisstudy investigates theeffects ofprinted circuit board (PCB)material oninterconnect durability oflead free assemblies. Theassemblies involve soldering various packages (array andperipheral) ontoFR4,highglass transition temperature (To) FR4andPolyimide (PI) printed circuit boards using Sn3AgO.5Cu solder alloy. Theglass transition temperature ofthese materials ranges from130°C to230°C. Thermomechanical properties, such aselastic modulus andthermal expansion coefficients, of theboard materials varyconsiderably. Theseproperties haveadirect impact ontheinterconnect durability. Inthis paper, thermomechanical properties areexperimentally determined andusedforsolder jointdurability simulation. Two kinds ofenvironmental loadings are simulated: temperature cycling andrandomvibration loading. Theresults showthat PIboard provides abetter solder joint durability than FR4andhigh TgFR4under temperature cycling conditions. PIassembly hasbetter durability thanFR4assembly under randomvibration. Thepaper also presents theeffect oftemperature onthe vibration response oftheFR4printed circuit board assemblies. Theunderstanding ofthese changes can contribute tothestudy oninterconnect durability under combined temperature cycling andvibration loading conditions.

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.

Reliability of electronic devices is a crucial scope of interest of the electronic manufacturing industry. The reliability is connected with electrical, thermal and mechanical properties of investigated products. Electrical and thermal properties are investigated during the specified tests such as thermal shocks, temperature, and humidity cycles, dry oven storage. Mechanical properties are concerned of mounted components are mainly problem of the assembly industry. At the present electronic components are mounted to the PCB mostly by surface mount technology (SMT) or flip chip processes. The lead-solders are being presently replaced with lead-free solders or electrically conductive adhesives. It is caused by the European and Japanese restrictions. The restrictions forbid using lead in consumer electronic products because of its harmful influence on beings. The new solders and assembly technology force to the following investigations of reliability of joints. This paper contains information about information tests as accelerated tests commonly used to evaluate fatigue life of interconnections in electronic assembly. In the first part of the paper short review of accelerated tests is presented. Anand's model of the solder joint used in finite elements analysis (FEA) and Darveaux's crack initiation and growth model are also mentioned, The bases of FEA and DOE are beyond the scope of this paper. In the second part of the paper harmonic as well as random variation and two different constructions of shakers, their advantages, limitations and requirements are presented. Characterization of specimen and vibration setup is considered. At the end of the paper vibration test is proposed

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.

New construction of fine pitch plastic ball grid array (FBGA) has been investigated through experimentation and physics of failure (PoF) analysis based on the reliability point of view. In this study, a three dimensional FEA model was developed to understand the thermomechanical behavior of FBGA under cyclic thermal loading environments. Experimental measurement was also carried out and the package warpage information was recorded by high-resolution digital CCD cameras with a 3-D image correlation method to validate this FEA model. The validated FEA model was used to calculate the inelastic strain of FBGA package that is related to the fatigue life of solder joint.

Original Equipment Manufacturers (OEM) who supply high reliability products to markets such as military, aerospace, and automotive are continually investigating methods to enhance the reliability of their products utilizing “off the shelf” components and materials. An extensive DOE is underway to determine how assembly processes such as conformal coat and PBGA underfill can interact with PCB design parameters such as SMD vs. NSMD solder pads to provide enhanced solder joint reliability for products that require the greatest reliability achievable. Board level temperature cycling and vibration testing will be performed to quantify the reliability improvements that can occur by implementing a BGA underfill process.