The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Consistent and wide-ranging material property data are needed for microelectronics encapsulants for the determination of mechanical design, reliability assessment, and process optimization of electronic packages. Since, the vast majority of contemporary underfills used are epoxy based, they have the propensity to absorb moisture, which can lead to undesirable reductions in their mechanical and adhesion...
In this work, we have used nanoindentation methods to explore the creep behavior, and aging effects of SAC305 solder joints at several elevated testing temperatures from 25 to 125 oC. A special high temperature stage and test protocol was used within the nanoindentation system to carefully control the testing temperature, and make the measurements insensitive to thermal drift problems. Solder joints...
When exposed to a temperature changing environment, solder joints in electronic assemblies are subjected to cyclic thermal-mechanical loading due to the mismatches in coefficients of thermal expansion (CTE) of the different assembly materials. Eventually, the cyclic loading can result in fatigue failure of solder joints, which is one of the common failure modes in electronic packaging. While it has...
The mechanical behavior of lead free solders is highly dependent on the testing temperature. Previous investigations on mechanical characterization of conventional and doped lead free SAC solders have mainly emphasized stress-strain and creep testing at temperatures from 25 to 125 °C. However, solders are exposed to very high temperatures from 125–200 °C in several harsh environment applications including...
Isothermal aging of lead-free Sn-Ag-Cu (SAC) solder joints leads to growth of intermetallic (IMC) particles in the solder bulk as well as growth of intermetallic layers at the joint interfaces with copper bond pads. Fracturing near the interfacial IMC layers is often found to be the primary reason for failures caused by drop impacts. The IMCs in SAC joints are primarily AgsSn and Cu6Sn5 binary compounds...
Lead free solder materials are susceptible to significant creep deformations in harsh high temperature environments including automotive, avionics, military, and oil exploration applications. In addition, dramatic degradations will occur in the creep responses of lead free solder alloys when they are exposed to long term isothermal aging during product applications at high temperatures. Such degradations...
Reliable, consistent, and comprehensive material property data are needed for microelectronics encapsulants for the purpose of mechanical design, reliability assessment, and process optimization of electronic packages. Since the vast majority of contemporary underfills are epoxy based, they have the propensity to absorb moisture, which can lead to undesirable changes in their mechanical and adhesion...
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 thermal cycling environments. In our ongoing studies, we are exploring aging phenomena by nano-mechanical testing of SAC lead free solder joints extracted from PBGA assemblies. Using nanoindentation techniques,...
Experimental testing and microstructural characterization have revealed that lead-free solders exhibit evolving properties that change significantly with environmental exposures such as isothermal aging and thermal cycling. These changes are especially large in harsh environments, where the effects of aging on solder joint behavior must be accounted for and included in constitutive models when predicting...
In this work, aging phenomena in solder joints have been explored by nano-mechanical testing. Using nanoindentation techniques, the elastic, plastic, and creep behavior of SAC305 solder joint materials have been explored for various aging conditions. Single crystal solder joints were first extracted from PBGA assemblies (14 × 14 mm, 0.8 mm ball pitch, 0.46 mm ball diameter), and then subjected to...
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...
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)...
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...
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...
The Anand viscoplastic constitutive model is often used to represent the deformation behavior of solders in electronic assemblies. In the Anand model, plasticity and creep are unified and described by the same set of flow and evolution relations. The nine parameters of the Anand constitutive model are typically determined from uniaxial stress-strain tests at several strain rates and temperatures using...
It has been demonstrated that isothermal aging leads to large reductions (up to 50%) in several key material properties for lead free solders including stiffness (modulus), yield stress, ultimate strength, and strain to failure. In addition, even more dramatic evolution has been observed in the creep response of aged solders, where up to 10,000X increases have been observed in the steady state (secondary)...
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 the observed material behavior variations of Sn-Ag-Cu (SAC) lead free solders during room temperature aging (25°C) and elevated temperature...
Microelectronic encapsulants exhibit evolving properties that change significantly with environmental exposures such as isothermal aging and thermal cycling. Such aging effects are exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In this work, the material behavior changes occurring in flip chip underfill encapsulants (silica...
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...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.