High Strain Rate Mechanical Properties of SAC-Q Solder for Extreme Temperatures After Exposure to Isothermal Aging Up to 90 Days

Electronic components can be subjected to shock-impact, vibration, and high temperatures in applications such as automobile, military and oil/gas scanning. Electronic components with this harsh atmosphere can face strain rates of 1 to 100 per second and ambient temperatures of up to 200 °C. There are insufficient data for plead-free solder alloys at higher thermal aging and strain rates. For SAC305 lead-free solder alloys, previously published and available records are restricted to both lower strain rates and lower temperature and storage durations. There are not many records available for the high temperature storage for the SAC305 material. This paper represents uniaxial tensile testing of SAC305 lead-free solder, with a high strain rate and high temperature for thermal aging, at various surrounding temperatures from 25°C to 200°C. For 6 months and 8 months, the specimens were preserved at 100°C for thermal aging. Test results for SAC305 thermally aging solder specimens were measured at 10, 35, 50, and 75 per second strain rates at various operating temperatures ranging from 25°C to 200°C using reflow profiles indicating solder joint assemblies. Stress-Strain curves are made for various strain rates and operational temperatures for thermally aged specimens for thermally aged specimens up to 8 months aging durations. The research findings were consistent with the Anand Viscoplasticity model for the SAC305 and the anand constants are determined by evaluating the stress strain behavior, based on high temperature specimen storage, for the large range of temperature and strain rates.

High Temperature High Strain Rate Properties of SAC305 with Effect of 100°C Storage for Prolonged Duration

Electronic devices are often exposed to high loads during shocks, vibrations and drop-out conditions in many industries such as automotive, oil and gas, aerospace and medical technology. These electronic parts also have extremely low and high temperatures between -65°C and 200°C. In the critical situations, these electronic devices can also be subjected to strain rates of 1 to 100 per second. Many doped solder alloys have recently been introduced in the electronic component, for example. SAC-Q, SAC-R, Innolot and others. M758 solder is a general purpose doped solder alloy resistant to thermal fatigue that serves surface mounting. For maximizing the confidentiality of electronic systems at high temperature storages with high strain rates, Mechanical results and data for lead-free solder alloys are extremely significant. Moreover, due to a thermal aging that induces changes in microstructure, the mechanical properties of solder alloys can be drastically altered. There are no data available for the solder alloy M758 with extreme low to high operating temperatures. Doped solder M758 for this analysis has been checked and analyzed at operating temperatures from -65°C to 200°C and a strain rate of up to 75 per second. Stress-strain curves are calculated for a wide variety of strain rates and test temperatures. The test results and data measured were also matched to the Anand viscoplasticity model. By estimating the behavioral stress strain properties at operating temperatures -65°C to 200°C, the Anand constants was determined.

High Strain Rate Properties of M758 Solder at Extreme Operating Temperatures

Many electronic products are subjected to heat for long periods, depending on their operations. Thus, it is expected that the physical and mechanical properties of electronic elements, including the soldering joints, will be affected. In this study, the impact of thermal aging time and temperature on the microstructure and mechanical properties of 96.5Sn–3.0Ag–0.5Cu (SAC305) was investigated. The samples used were SAC305 solder balls attached to copper pads. The research began by examining the microstructure of the aged samples at 150 °C for 100 and 1000 h. Then, this was compared to the microstructure of the same samples without thermal aging. Then, five groups of 10 samples were prepared from a shear stress–shear stain experiment. The first group was as produced, the second group was aged for 2 h, the third group was aged for 10 h, the fourth group was aged for 100 h, and the fifth group was aged for 1000 h. All groups were aged at a temperature of 150 °C. An Instron testing machine was used to plot a shear stress–shear stain curve until the ball was completely sheared off the pad. The mechanical properties, including the ultimate shear strength, the ultimate energy used to shear the ball, and the total energy used to shear the ball at all thermal aging times were then estimated. The results of this study indicated the formation of a layer of Cu6Sn5 over the copper pad, which thickened with thermal aging time. Furthermore, the ultimate and total shear strengths decreased with thermal aging time. The same procedure was repeated to assess the ultimate shear strength at 100 °C. The decrease in ultimate shear strength was more severe with increasing thermal aging temperature.

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Effect of Thermal Aging on the Mechanical Properties of SAC305

In the fields such as aerospace applications, medical applications and oil/gas production, electronic components may be exposed to extreme cold temperatures. These electronic packages and assemblies can also induce shakes, shocks and impacts. The higher strain rates of 1 to 100 per second and the low temperature of the atmosphere down to -65°C will impact electronic components within such an extreme surrounding. Records for lead free solder alloys measured at cooled working temperatures and high strain rates of thermal ageing are not available. The effects of the previously mentioned SAC305 lead free solder alloys are limited to low strain rates and high working temperatures. Records are not available for SAC305 solder at low operating temperatures. In this paper lead free solder alloy SAC305 was studied and analyzed at various lower surrounding temperatures, beginning at -65°C to 0°C, at high strain rates, and isothermally aged for up to 120 days at 100°C. After reflowing, the prepared SAC305 solder alloy sample were stored for thermal ageing and then tested at 10, 35, 50 and 75 per sec strain rates at operating temperatures from -65°C to 0°C. Stress strain curves are made for different low operating temperatures and different strain rates. The calculated experimental findings of SAC305 were compared with the Anand Viscoplasticity model. The findings of the experiment were consistent with Anand Viscoplasticity model and the Anand constants were calculated by estimating stress-strain reactions at various low temperatures and high strain rates for aging up to 120 days.

High Strain Rate Properties of SAC305 Alloy at Cold Temperatures Subsequent to 100°C Storage for Periods up to 120 Days

Electronics in a number of harsh environments may be subjected to very-low operating temperatures in conjunction with high strain rates. Examples include the automotive underhood environment, in which electronics on-engine and on- transmission may be exposed to low temperatures for sustained period in addition to high strain-rates resulting from engine vibration and road shocks. Further, electronics in downhole applications may be mounted just before the drill tip and be exposed to high strain rate resulting from the deep-well drilling in addition to exposure to extreme cold-temperatures while drilling in cold-climates. Transition of the industry to leadfree solder alloys for second level interconnects has necessitated the fundamental studies for long-term reliability assurance of products in harsh environments. There is scarcity of data for solder alloys at extreme cold temperatures and high-strain rates in the neighborhood of 1-100 per sec. Low strain-rate mechanical properties for SAC allots have shown degradation. In this paper, SAC105 and SAC305 leadfree solder alloys have been tested and studied at several lower surrounding temperature starting from - 65C up to +200C, with high strain rates. The prepared lead-free alloy specimen after reflowing, have been tested at strain rates of 10, 35, 50, and 75 per sec. The calculated experimental data has been fit to the Anand Viscoplasticity model. In order to assess the predictive power of the model, the model predictions from computed parameters have been compared with experimental data.

Extreme Cold-Temperature High-Strain Rate Properties of SAC Solder Alloys

In the applications like automotive, military applications and in oil/gas exploration, the electronic parts can be exposed to vibrations, impact, shocks and high temperatures, as well. In these harsh environments, electronic components may experience strain rates of 1 to 100 per seconds and environmental temperature up to 200°C. The published literature available for lead-free solder alloys at high aging temperature and at high strain rates is scarce. Previous published and available studies for SAC305 lead-free solder alloys are restricted to either low strain rates or lower storage temperatures in the region of 50°C. High temperature, high strain-rate properties of SAC305 are not available for prolonged periods of isothermal storage. In this paper, lead- free solder alloy SAC305 has been tested and examined at numerous surrounding temperatures from 25°C up to 200°C, with high strain rates and elevated thermal aging temperature. The specimens were stored at 100°C for the duration of 3 months and 4 months for thermal aging. These thermally aged SAC305 lead-free solder specimen, which have been made using reflow profiles indicative of solder-joint manufacturing assemblies, have been tested at strain rates of 10, 35, 50, and 75 per sec at multiple operating temperatures ranging from 25°C to 200°C. Stress-strain curves are prepared for the wide range of operating temperatures and strain rates for thermally aged specimens for 3 months and 4 months durations. The experimental results have been fit to the Anand Viscoplastic model for SAC305 and the Anand constants are established by estimating the measured stress-strain behavior for the wide range of temperatures and strain rates, after high temperature storage of specimens.

Effect of 100°C Aging for Periods of up to 120-days on High Strain Rate Properties of SAC305 Alloys

In the industries like aerospace applications, medical applications and in oil/gas exploration, the electronic components can be exposed to very cold temperatures. In addition, these electronic packages and assemblies may be subjected to vibrations, shocks and impacts. In such harsh surrounding, electronic components may face strain rates of 1 to 100 per seconds and low surrounding temperature up to - 65°C. The records are not available for lead-free solder alloys tested at cold operating temperature and at high strain rates. Earlier published results for SAC305 lead-free solder alloys is restricted to low strain rates and high operating temperatures. For the material SAC305, records are not available for low operating temperatures. In this paper, lead-free solder alloy SAC305 has been tested and studied at several lower surrounding temperature starting from -65°C up to 0°C, with high strain rates. The prepared SAC305 lead-free alloy specimen after reflowing, have been tested at strain rates of 10, 35, 50, and 75 per sec at multiple operating temperatures ranging from -65°C to 0°C. Stress-strain curves are plotted for various low operating temperatures and for the range of strain rates. The calculated experimental data has been fit to the Anand Viscoplasticity model for SAC305 and the Anand constants are established by forecasting the measured stress- strain behavior for the various lower temperatures and high strain rates.

High Strain-Rate Properties for SAC305 at Cold Operating Temperatures down to -65°C

Exposure to extreme-low environmental temperatures in conjunction with high strain-rates may be encountered by electronics in several harsh-environment applications. Examples include down-hole drilling, aerospace, automotive electronics - which may endure high or low operating temperatures during operation. The automotive operating temperature range is −40°C to + 125°C. The equipment operating range for defense equipment is −55°C to + 125°C. In addition, electronic systems may experience prolonged periods of non-climate-controlled exposure to high and low temperature prior to deployment in the intended application. Materials properties of interconnects at extreme-low temperatures and high strain-rates are not well-studied and there is a scarcity of published data on undoped and doped solder alloys. The current paper fills this void in the state of art through measurements of properties of doped SAC alloys at low temperatures in the range of −65°C to high temperatures up to 200°C, at high strain rates after various durations of thermal aging. Alloys studied include SAC305, SAC-Q, and M758. In each case, the stress-strain curves have been measured at low operating temperatures using impact-hammer based tensile tests with cooling chamber. Anand Viscoplasticity model constants have been computed to model the material behavior over the whole range of temperatures and strain rates in the range of 1–100 per sec. In addition, the evolution of the model constants with the duration of thermal storage at high temperature has been quantified. The computed anand parameters has been used to simulate the drop events for a ball-grid array package on printed circuit board assembly to determine hysteresis loop and plastic work density.

Vishal Mehta

Papers

Extreme Cold-Temperature High-Strain Rate Properties of SAC Solder Alloys

Effect of 100°C Aging for Periods of up to 120-days on High Strain Rate Properties of SAC305 Alloys

High Strain Rate Mechanical Properties of SAC-Q Solder for Extreme Temperatures After Exposure to Isothermal Aging Up to 90 Days

High Strain-Rate Properties for SAC305 at Cold Operating Temperatures down to -65°C

Low-Temperature High Strain Rate Constitutive Behavior of Doped and Undoped SnAgCu Solder Alloys after Prolonged Storage at High Temperature