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Electronic systems may be subjected to prolonged and intermittent periods of storage prior to deployment or usage. Prior studies have shown that leadfree solder interconnects show measurable degradation in the mechanical properties even after brief exposures to high temperature. In this paper, a method has been developed for the determining equivalent storage time to produce identical damage at a...
The mechanical properties of a lead free solder are strongly influenced by its microstructure, which is controlled by its thermal history including solidification rate and thermal aging after solidification. Due to aging phenomena, the microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal and/or...
Package-on-Package (PoP) assemblies may experience warpage during package fabrication and later during surface mount assembly. Excessive warpage may result in loss-of-coplanarity, open connections, mis-shaped joints, and reduction in package board-level reliability (BLR) under environmental stresses of thermal cycling, shock and vibration. Previous researchers have shown that warpage may be influenced...
Solid-state lighting (SSL) luminaires containing light emitting diodes (LEDs) have the potential of seeing excessive temperatures when being transported across country or being stored in non-climate controlled warehouses. They are also being used in outdoor applications in desert environments that see little or no humidity but will experience extremely high temperatures during the day. This makes...
The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model)...
Electronics subjected to shock and vibration may experience strain rates of 1–100 sec−1. High strain rate data is scarce for leadfree solders at strain rates in the range of 1–100 sec−1, typical of drop-impact, shock and vibration. A new experimental method has been developed to achieve constant strain rate in the neighborhood of 1 to 100 sec−1 during the entire deformation history. SAC105 and SAC305,...
Field deployed electronics us often subjected to a combination of thermal aging and thermal cycling. The thermal cycle magnitudes may vary over the lifetime of the product. Long-life systems may be re-deployed several times over the use life of the product. Aging has been previously shown to effect the reliability and constitutive behaviour of second-level leadfree interconnects. Often the equipment...
Electronics in harsh environments may be subjected to extended periods of simultaneous high temperature and vibration and stored for prolonged periods of time prior to and during deployment. Damage accrued during the storage and prior usage may reduce the remaining useful life of the electronic system during deployment. Methods for assessment of accrued dam age under simultaneous stresses are scarce...
Miniaturization of electronic products has resulted in proliferation of package-on-package (PoP) architectures in por table electronics. In this study, daisy-chained double-stack PoP components have been used for early-identification of drop-shock impact damage. Time-spectral feature vector based damage pre-cursors have been identified and measured under app lied shock stimulus. Experimental strain...
Electronic interconnects may encounter damage under exposure to vibration and mechanical shock. The damage may manifest itself as an open circuit after a finite period of operation. The traditional methods for damage detection such as microscopy and x-ray are destructive in nature and provide limited information offline. In this paper, resistance spectroscopy and phase-sensitive detection based state...
In this work, we have used test chips containing piezoresistive sensors to characterize the in-situ die surface stress evolution during thermal cycling of flip chip ceramic ball grid array (FC-CBGA) components suitable for microprocessor packaging. The utilized (111) silicon test chips were able to measure the complete three-dimensional stress state (all 6 stress components) at each sensor site being...
The effect of temperature exposure encountered both during assembly and in fielded products, has a known influence on glass transition temperature of printed-circuit board (PCB) laminate materials. Printed circuit board laminates such as FR4 are composites of epoxy resin with woven fiberglass reinforcement. Interaction between manufacturing process variables that impact the changes in glass transition...
In this work, the viscoelastic mechanical response of a typical underfill encapsulant has been characterized via rate dependent stress-strain testing over a wide temperature range, and via creep testing for a large range of applied stress levels and temperatures. The 60 × 3 × 0.5 mm test specimens were dispensed and cured with production equipment using the same conditions as those used in actual...
Electronics installed in automotive systems are subjected simultaneously to mechanical vibrations and thermal loads in underhood applications. Typical failure modes include solder joint failure, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The solder interconnects accrue damage much faster when vibrated at elevated temperatures. Industry migration to leadfree...
In this paper, an anomaly method has been developed for the prognostication and health monitoring of Electronic assemblies under shock and vibration. Previously, damage initiation, damage progression in electronic assemblies have been monitored using state-space vector from resistance spectroscopy and then be analyzed with particle filter (PF) and the theory of Bayesian. Precise resistance measurement...
Field deployed electronics may accrue damage due to environmental exposure and usage after finite period of service but may not often have any macro-indicators of failure such as cracks or delamination. A method to interrogate the damage state of field deployed electronics in the pre-failure space may allow insight into the damage initiation, progression, and remaining useful life of the deployed...
The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work, we have demonstrated that the observed material behavior variations of Sn-Ag-Cu (SAC) lead free solders during elevated temperature aging were unexpectedly large and universally...
Electronics in aerospace applications may be subjected to very high g-levels during normal operation. A column array interconnect has been studied for reliability during extended duration aerospace missions in presence of high-g levels. Ceramic area-array components have been populated with column interconnects. The wire column interconnects are fabricated using a two piece fixture that holds a ceramic...
Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted...
The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work on aging effects, we have demonstrated that large degradations occur in the material properties (stiffness and strength) and creep behavior of Sn-Ag-Cu (SAC) lead free solders...
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