Davide Di Maio - Academia.edu (original) (raw)
Papers by Davide Di Maio
Lead-free selective soldering can result in extended times at high temperatures, which in turn ca... more Lead-free selective soldering can result in extended times at high temperatures, which in turn can result in excessive dissolution of exposed copper, such as plated through holes. This phenomenon is more severe with lead-free, since the alloys have higher melting points, hence requiring longer times for the PTH to reach the higher temperatures, and the alloys typically have a greater capacity to dissolve copper. This paper discusses a test method that characterises the dissolution rate of copper from PWBs. A PWB design was created that allowed the time for the dissolution of a copper pad to be measured. With this quantitative method a soldering process or an alloy can be characterised in terms of dissolution rates at specific conditions of temperature and flow rate. This methodology provided repeatable measurements that allowed the various experimental parameters to be isolated. Particular attention was paid at the flow rate of the molten solder. In fact, different alloys at the sam...
Microelectronics Reliability, 2010
Vibration loading can have a significant impact on the reliability of electronic components. Due ... more Vibration loading can have a significant impact on the reliability of electronic components. Due to the cyclic strain and stress in the materials making up the component these can cause damage and hence wear out failures. The recent move from lead to lead-free soldering by the electronics industry has necessitated the generation of material properties data that will allow accurate prediction of the lead-free solder's performance under vibration conditions. To assess the reliability of lead-free solders under vibration loading, test equipment has been designed for small solder joints. Such test equipment must be able to extract solder mechanical properties and physics of failure fatigue lifetime parameters/models for numerical model and prediction of lifetime of real electronic components. This paper focuses on the design, analysis and development of this type of test facility.
IEEE Transactions on Instrumentation and Measurement, 2011
The European Union Restriction of Hazardous Substances Directive of 2006 has revolutionized the u... more The European Union Restriction of Hazardous Substances Directive of 2006 has revolutionized the use of materials for electronic packaging: tin-lead solder has had to be replaced with lead-free solder. While years of experience and data acquired in the field are available for tin-lead solder, the same cannot be said for lead-free solder. The lack of data on these new alloys hinders the use of modeling for predicting the reliability of lead-free solder. This paper describes a new testing machine that can assess the properties of solder joints in a copper-solder-copper structure. Finite-element analysis models using the newly acquired data will improve lifetime predictions. During a typical test, a model solder joint is expanded and contracted in shear. This actuation is achieved from the thermal expansion of a steel tube, which provides a smooth movement at a rate that is equivalent to that encountered on printed circuit boards when thermally stressed. The applied force is measured using a load cell; the sample displacement is determined from laser displacement sensors. Hysteresis load-displacement loops are obtained and can be used for evaluating the material plastic response and loading history. A camera/microscope system captures time-lapse photography images, which digital image correlation software can analyze to obtain strain profiles and study crack propagation. The instrument is capable of investigating creep, stress relaxation, and isothermal and thermal-mechanical fatigue behavior of solder interconnects. Results from this new instrument are presented here for isothermal and thermal cycling fatigue tests.
The changeover from eutectic Sn-Pb solders to lead-free solders has been driven by environmental ... more The changeover from eutectic Sn-Pb solders to lead-free solders has been driven by environmental concerns and market accessibility in the last few years. Though a number of creep constitutive laws of lead-free solder have been reported due to the importance of creep in solder joint failure in the electronic packaging, these constitutive laws often show great variations across the applicable stress range. In-situ measurement of strain fields in micro regions can help make the creep model more realistic. In this study, shear tests have been carried out on small solder joints in order to gain insight into the factors affecting solder properties. In order to measure the strain in solder joints, the Digital Image Correlation Method (DICM) has been used. The experimental results proved that there are two mechanisms that disturb the uniform deformation in solder joint. One is the interfacial strain concentration which has a dimension of less than 30μm and the other is spreading across interfaces from the locally deformed area, which has a size from about 50μm to 100μm. The existence of these local concentrations of creep strain is thought to be at least one of the causes of the variations in the published creep parameters. The deformation of solder joint on the shear test has also been modeled using Finite Element Method (FEM), and a three-layered model has been proposed to simulate the experimental results.
Vibration is commonly encountered during the life time of electronic components. It is a major ca... more Vibration is commonly encountered during the life time of electronic components. It is a major cause of failure due to cyclic strain and stress that give rise to damage in the materials making up the component. The recent move from lead to lead-free soldering by the electronics industry has necessitated the generation of material properties data that will allow accurate prediction of the lead-free solder's performance under vibration conditions. To assess the reliability of lead-free solders under vibration loading, test equipment has been designed for small solder joints using a piezoelectric cell as the vibration source. This equipment will also be used to produce results that can be used to extract solder mechanical material properties and fatigue lifetime parameters suitable for numerical simulations and prediction of solder joint lifetime under vibration loading. This paper focuses on the analysis of the structure of the proposed vibration test equipment using Finite Element analysis method. Modal analysis as well as transient analysis has been undertaken to help understand the equipment response in vibration tests. A number of design variables and loading conditions have been analysed in this work.
Lead-free selective soldering can result in extended times at high temperatures, which in turn ca... more Lead-free selective soldering can result in extended times at high temperatures, which in turn can result in excessive dissolution of exposed copper, such as plated through holes. This phenomenon is more severe with lead-free, since the alloys have higher melting points, hence requiring longer times for the PTH to reach the higher temperatures, and the alloys typically have a greater capacity to dissolve copper. This paper discusses a test method that characterises the dissolution rate of copper from PWBs. A PWB design was created that allowed the time for the dissolution of a copper pad to be measured. With this quantitative method a soldering process or an alloy can be characterised in terms of dissolution rates at specific conditions of temperature and flow rate. This methodology provided repeatable measurements that allowed the various experimental parameters to be isolated. Particular attention was paid at the flow rate of the molten solder. In fact, different alloys at the sam...
Microelectronics Reliability, 2010
Vibration loading can have a significant impact on the reliability of electronic components. Due ... more Vibration loading can have a significant impact on the reliability of electronic components. Due to the cyclic strain and stress in the materials making up the component these can cause damage and hence wear out failures. The recent move from lead to lead-free soldering by the electronics industry has necessitated the generation of material properties data that will allow accurate prediction of the lead-free solder's performance under vibration conditions. To assess the reliability of lead-free solders under vibration loading, test equipment has been designed for small solder joints. Such test equipment must be able to extract solder mechanical properties and physics of failure fatigue lifetime parameters/models for numerical model and prediction of lifetime of real electronic components. This paper focuses on the design, analysis and development of this type of test facility.
IEEE Transactions on Instrumentation and Measurement, 2011
The European Union Restriction of Hazardous Substances Directive of 2006 has revolutionized the u... more The European Union Restriction of Hazardous Substances Directive of 2006 has revolutionized the use of materials for electronic packaging: tin-lead solder has had to be replaced with lead-free solder. While years of experience and data acquired in the field are available for tin-lead solder, the same cannot be said for lead-free solder. The lack of data on these new alloys hinders the use of modeling for predicting the reliability of lead-free solder. This paper describes a new testing machine that can assess the properties of solder joints in a copper-solder-copper structure. Finite-element analysis models using the newly acquired data will improve lifetime predictions. During a typical test, a model solder joint is expanded and contracted in shear. This actuation is achieved from the thermal expansion of a steel tube, which provides a smooth movement at a rate that is equivalent to that encountered on printed circuit boards when thermally stressed. The applied force is measured using a load cell; the sample displacement is determined from laser displacement sensors. Hysteresis load-displacement loops are obtained and can be used for evaluating the material plastic response and loading history. A camera/microscope system captures time-lapse photography images, which digital image correlation software can analyze to obtain strain profiles and study crack propagation. The instrument is capable of investigating creep, stress relaxation, and isothermal and thermal-mechanical fatigue behavior of solder interconnects. Results from this new instrument are presented here for isothermal and thermal cycling fatigue tests.
The changeover from eutectic Sn-Pb solders to lead-free solders has been driven by environmental ... more The changeover from eutectic Sn-Pb solders to lead-free solders has been driven by environmental concerns and market accessibility in the last few years. Though a number of creep constitutive laws of lead-free solder have been reported due to the importance of creep in solder joint failure in the electronic packaging, these constitutive laws often show great variations across the applicable stress range. In-situ measurement of strain fields in micro regions can help make the creep model more realistic. In this study, shear tests have been carried out on small solder joints in order to gain insight into the factors affecting solder properties. In order to measure the strain in solder joints, the Digital Image Correlation Method (DICM) has been used. The experimental results proved that there are two mechanisms that disturb the uniform deformation in solder joint. One is the interfacial strain concentration which has a dimension of less than 30μm and the other is spreading across interfaces from the locally deformed area, which has a size from about 50μm to 100μm. The existence of these local concentrations of creep strain is thought to be at least one of the causes of the variations in the published creep parameters. The deformation of solder joint on the shear test has also been modeled using Finite Element Method (FEM), and a three-layered model has been proposed to simulate the experimental results.
Vibration is commonly encountered during the life time of electronic components. It is a major ca... more Vibration is commonly encountered during the life time of electronic components. It is a major cause of failure due to cyclic strain and stress that give rise to damage in the materials making up the component. The recent move from lead to lead-free soldering by the electronics industry has necessitated the generation of material properties data that will allow accurate prediction of the lead-free solder's performance under vibration conditions. To assess the reliability of lead-free solders under vibration loading, test equipment has been designed for small solder joints using a piezoelectric cell as the vibration source. This equipment will also be used to produce results that can be used to extract solder mechanical material properties and fatigue lifetime parameters suitable for numerical simulations and prediction of solder joint lifetime under vibration loading. This paper focuses on the analysis of the structure of the proposed vibration test equipment using Finite Element analysis method. Modal analysis as well as transient analysis has been undertaken to help understand the equipment response in vibration tests. A number of design variables and loading conditions have been analysed in this work.