Temperature Dependent Viscoplastic Simulation of Controlled Collapse Solder Joint Under Thermal Cycling

1993 ◽  
Vol 115 (1) ◽  
pp. 16-21 ◽  
Author(s):  
V. Sarihan
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Strong Dependence ◽  
Inelastic Strain ◽  
Operating Conditions ◽  
Material Behavior ◽  
Time Dependent ◽  
Strong Temperature Dependence ◽  
Electronic Packages ◽  
Material Response

Solder is being extensively used in electronic packages for both electrical and mechanical connection. Solder joints are subjected to severe operating conditions and hence their reliability is very critical for the packages. Simulation is very effective for understanding, predicting and design improvement of electronic packages where solder is the prime joiner, however all the material response complexities of solder over the temperature regime it is subjected to should be modelled. Solder in electronic components very often operates at 0.6 to 0.8 times it’s melting point. In this regime the time dependent material response (creep and stress relaxation) is very significant and can no longer be ignored. Also the plastic and creep responses of solder alloys have a very strong dependence on temperature. A nonlinear finite element based methodology has been developed for simulation of solder alloy over its full regime of material behavior, also accounting for the strong temperature dependence. This includes elastic, time independent plastic, and time dependent viscoplastic response. The methodology has been used for predicting the response of a flip chip with 95Pb5 percent Sn peripheral bumps subjected to thermal cycling. Correlation is observed between the location of failure in the bump and the maximum inelastic strain. The importance of doing a multicycle simulation is demonstrated and a direction is indicated for the bump size modification for flip chip bump design improvements for greater reliability.

Thermal Cycling Guidelines for Automotive, Computer, Portable, and Implantable Medical Device Applications

2000 ◽  
Author(s):  
Rajiv Raghunathan ◽  
Raghuram V. Pucha ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Inelastic Strain ◽  
Computer Applications ◽  
Material Behavior ◽  
Implantable Medical Device ◽  
Implantable Medical Devices ◽  
Device Applications ◽  
Component Assembly ◽  
Virtual Qualification

Abstract The objective of this work is to develop qualification guidelines for Flip-Chip on Board (FCOB) and Flip Chip Chip-Scale Packages (FCCSP) used in implantable medical devices, automotive applications, computer applications and portables, taking into consideration the thermal history associated with the field conditions. The accumulated equivalent inelastic strain per cycle and the maximum strain energy density have been used as damage parameters to correlate solder fatigue damage during field use and thermal cycling. The component assembly process mechanics, the time and temperature-dependent material behavior, and the critical geometric features of the assembly have been taken into consideration for developing the comprehensive virtual qualification methodology.

Accelerated Thermal Cycling Guidelines for Electronic Packages in Military Avionics Thermal Environment

2004 ◽  
Vol 126 (2) ◽  
pp. 256-264 ◽  
Author(s):  
Raghuram V. Pucha ◽  
Krishna Tunga ◽  
James Pyland ◽  
Suresh K. Sitaraman
Keyword(s):  
Thermal Cycling ◽  
Thermal Environment ◽  
Inelastic Strain ◽  
Electronic Packages ◽  
Strain Accumulation ◽  
Material Models ◽  
Process Mechanics ◽  
Accelerated Thermal Cycling ◽  
Damage Mapping ◽  
Board Level

A field-use induced damage mapping methodology is presented that can take into consideration the field-use thermal environment profile to develop accelerated thermal cycling guidelines for packages intended to be used in military avionics thermal environment. The board-level assembly process mechanics and critical geometric features with appropriate material models are taken into consideration while developing the methodology. The models developed are validated against in-house and published accelerated thermal cycling experimental data. The developed mapping methodology is employed to design alternate accelerated thermal cycles by matching the creep and plastic strain contributions to total inelastic strain accumulation in solder under military field-use and accelerated thermal cycling environments, while reducing the time for accelerated thermal cycling and qualification.

Die Stress Variation During Thermal Cycling Reliability Tests

2007 ◽  
Author(s):  
M. Kaysar Rahim ◽  
Jordan Roberts ◽  
Jeffrey C. Suhling ◽  
Richard C. Jaeger ◽  
Pradeep Lall
Keyword(s):  
Thermal Cycling ◽  
Electronic Packaging ◽  
Room Temperature ◽  
Flip Chip ◽  
Constitutive Relations ◽  
Temperature Cycling ◽  
Material Behavior ◽  
Aging Effects ◽  
Test Chips

Thermal cycling accelerated life testing is an established technique for thermo-mechanical evaluation and qualification of electronic packages. Finite element life predictions for thermal cycling configurations are challenging due to several reasons including the complicated temperature/time dependent constitutive relations and failure criteria needed for solders, encapsulants and their interfaces; aging/evolving material behavior for the packaging materials (e.g. solders); difficulties in modeling plating finishes; the complicated geometries of typical electronic assemblies; etc. In addition, in-situ measurements of stresses and strains in assemblies subjected to temperature cycling are difficult because of the extreme environmental conditions and the fact that the primary materials/interfaces of interest (e.g. solder joints, die device surface, wire bonds, etc.) are embedded within the assembly (not at the surface). For these reasons, little is known about the evolution of the stresses, strains, and deformations occurring within sophisticated electronic packaging geometries during thermal cycling. In this work, we have used test chips containing piezoresistive stress sensors to characterize the in-situ die surface stress during long-term thermal cycling of electronic packaging assemblies. Using (111) silicon test chips, the complete three-dimensional stress state (all 6 stress components) was measured at each rosette site by monitoring the resistance changes occurring in the sensors. The packaging configuration studied in this work was flip chip on laminate where 5 × 5 mm perimeter bumped die were assembled on FR-406 substrates. Three different thermal cycling temperature profiles were considered. In each case, the die stresses were initially measured at room temperature after packaging. The packaged assemblies were then subjected to thermal cycling and measurements were made either incrementally or continuously during the environmental exposures. In the incremental measurements, the packages were removed from the chamber after various durations of thermal cycling (e.g. 250, 500, 750, 1000 cycles, etc.), and the sensor resistances were measured at room temperature. In the continuous measurements, the sensor resistances at critical locations on the die device surface (e.g. die center and die corners) were recorded continuously during the thermal cycling exposure. From the resistance data, the stresses at each site were calculated and plotted versus time. The experimental observations show cycle-to-cycle evolution in the stress magnitudes due to material aging effects, stress relaxation and creep phenomena, and development of interfacial damage.

An Optical Method for Measuring the Two-Dimensional Surface Curvatures of Electronic Packages During Thermal Cycling

2000 ◽  
Vol 123 (3) ◽  
pp. 196-199 ◽  
Author(s):  
Yong Du ◽  
Jie-Hua Zhao ◽  
Paul Ho
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Cycling ◽  
Optical Method ◽  
Flip Chip ◽  
Laser Beams ◽  
Electronic Packages ◽  
Two Dimensional ◽  
Element Analysis ◽  
Dimensional Surface

An optical method was developed to measure the two-dimensional (2D) surface curvatures of electronic packages by employing four laser beams. Each laser beam measures the slopes of the surface at the incident point along two perpendicular directions. By combining four pairs of slopes, the 2D surface curvatures of the package can be calculated. The surface warpage of an underfilled flip-chip package during thermal cycling was measured by this method and the result was verified by finite element analysis (FEA). Both experimental and FEA results show that the surface warpage is almost a linear function of temperature between 25°C and 150°C for the measured package.

Thermomechanical Fatigue of a Directionally-Solidified Ni-Base Superalloy in the Presence of Stress Concentrations

2009 ◽  
Author(s):  
Robert A. Kupkovits ◽  
Richard W. Neu
Keyword(s):  
Gas Turbines ◽  
Turbine Blades ◽  
Thermomechanical Fatigue ◽  
Operating Conditions ◽  
Material Behavior ◽  
Time Dependent ◽  
Temperature Cycle ◽  
Directionally Solidified ◽  
Stress Concentrations ◽  
Damage Mechanisms

Directionally-solidified (DS) Ni-base superalloys are used in high temperature gas turbines because of their excellent properties in the most aggressive mechanical, thermal, and environmental operating conditions. Complex thermomechanical loading of turbine blades is induced by repeated engine start-up, firing, and shut-down transients. These histories make life prediction for such components difficult and subjective. In addition, accurate techniques need to account for the presence of cooling hole stress concentrations, time-dependent dwells, thermal gradients, and anisotropic material properties. In working towards such an analytical life model, this paper describes the cyclic deformation response and damage mechanisms resulting from thermomechanical fatigue (TMF) of directionally-solidified CM247LC DS. Experimental LCF tests consisted of linear in-phase (IP) and out-of-phase (OP) TMF cycles performed on smooth and notched round-bar specimens in both longitudinal and transverse grain orientations. Results take into consideration anisotropy, time-dependent deformation, and notch effects in addition to the waveform and temperature cycle characteristics. The active damage mechanisms are identified as a function of these parameters. Conclusions are drawn in light of fractography, microscopy, and finite element analysis conducted to evaluate geometric and microstructural influences on material behavior.

Evolution of the Stress-Strain and Creep Behavior of Underfill Encapsulants With Aging

2009 ◽  
Author(s):  
Chang Lin ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Creep Rate ◽  
Thermal Cycling ◽  
Aging Time ◽  
Aging Temperature ◽  
Isothermal Aging ◽  
Flip Chip ◽  
Material Behavior ◽  
Initial Slope ◽  
Aging Effects ◽  
Stress Strain

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, measurements of material behavior changes occurring in flip chip underfill encapsulants exposed to isothermal aging have been performed. A novel method has been developed to fabricate freestanding underfill uniaxial test specimens so that they accurately reflect the encapsulant layer present in flip chip assemblies. Using the developed specimen preparation procedure, isothermal aging effects have been characterized at several elevated temperatures (+ 80, +100, + 125, and +150 °C). Samples have been aged at the four temperatures for periods up to 6 months. Stress-strain and creep tests have been performed on non-aged and aged samples, and the changes in mechanical behavior have been recorded for the various aging temperatures and durations of isothermal exposure. Empirical models have been developed to predict the evolution of the material properties (modulus, strength) and the creep strain rate as a function of temperature, aging time, and aging temperature. The evaluated underfill illustrated softening behavior at temperatures exceeding 100 °C, although the documented Tg ranged from 130–150 °C. The obtained results showed an obvious enhancement of the underfill mechanical properties as a function of the aging temperature and aging time. Both the effective elastic modulus (initial slope) and ultimate tensile strength (highest stress before failure) increase monotonically with the amount of isothermal aging or aging temperature, regardless of whether the aging temperature is below, at, or above the Tg of the material. From the creep results, it was seen that at a given time, the creep strains were much lower for the aged samples relative to the non-aged samples. Thermal aging has a significant effect on the secondary creep rate, which decreases with both the aging temperature and the aging time. Up to a 100X reduction in the creep rate was observed, and the major changes occurred during the first 50 days of the isothermal aging.

Development of a Novel Test Setup to Study the Combined Effects of Electromigration and Mechanical Stress in Solder Interconnects

2020 ◽  
Author(s):  
Mahsa Montazeri ◽  
David R. Huitink
Keyword(s):  
Tensile Stress ◽  
Thermal Cycling ◽  
Current Density ◽  
Flip Chip ◽  
High Current Density ◽  
Operating Conditions ◽  
Reliability Estimation ◽  
High Current ◽  
Test Setup ◽  
Solder Interconnects

Abstract One key concern that arises from scaling of device interconnects with increasing power density requirements is electromigration (EM). On the other hand, thermal cycling fatigue has always been a reliability challenge in solder interconnects. Variations in device temperature caused by environmental or operating conditions induce stress in solders, as they usually connect two components with different coefficients of thermal expansion (CTE). These thermally induced stresses may lead to crack formation within the solders. The combination of EM effects and thermal cycling add to the complexity of the reliability estimation for high current density applications. In this work, a novel test setup has been designed and developed to estimate the reliability of solder interconnects under high current density, while a constant tensile stress is also applied to the solder interconnect. The test set up offers the ability to test up to four samples at the same time. Additionally, the test samples are fabricated with two copper wires connected by Pb/Sn solder to imitate copper UBM in a flip-chip bonding connection. Strain in solder is measured by monitoring the elongation of the wire during testing, while failure of the connection is detected by continuous monitoring of the electrical resistance. The experiment is conducted for conditions including pure tensile stress, pure EM and coupled EM and tensile stress where a significant reduction in life-time is observed for the coupled degradation effects. Comparing the experimental results of different current densities at different stress levels will help in identifying the nature of degradation in solders, which will help inform the drive for miniaturization.

Improving the Long-Term Performance of Elastomeric Seals by Material Behavior Design

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ryan B. Sefkow ◽  
Nicholas J. Maciejewski ◽  
Barney E. Klamecki
Keyword(s):  
Energy Density ◽  
Contact Pressure ◽  
Strain Energy ◽  
Applied Pressure ◽  
Material Behavior ◽  
Time Dependent ◽  
Ring Section ◽  
Stiff Material ◽  
Elastomeric Seals

Previously it was shown that including smaller inset regions of less stiff material in the larger O-ring section at locations of high stress results in lower strain energy density in the section. This lower energy content is expected to lead to improved long-term seal performance due to less permanent material deformation and so less loss of seal-housing contact pressure. The shape of the inset region, the time-dependent change in material properties, and hence change in seal behavior over time in use were not considered. In this research experimental and numerical simulation studies were conducted to characterize the time-dependent performance of O-ring section designs with small inset regions of different mechanical behaviors than the larger surrounding section. Seal performance in terms of the rate of loss of contact pressure of modified designs and a baseline elastic, one-material design was calculated in finite element models using experimentally measured time-dependent material behavior. The elastic strain energy fields in O-ring sections were calculated under applied pressure and applied displacement loadings. The highest stress, strain, and strain energy regions in O-rings are near seal-gland surface contacts with significantly lower stress in regions of applied pressure. If the size of the modified region of the seal is comparable to the size of the highest energy density region, the shape of the inset is not a major factor in determining overall seal section behavior. The rate of loss of seal-housing contact pressure over time was less for the modified design O-ring sections compared with the baseline seal design. The time-dependent performance of elastomeric seals can be improved by designing seals based on variation of mechanical behavior of the seal over the seal section. Improvement in retention of sealing contact pressure is expected for seal designs with less stiff material in regions of high strain energy density.

A Highly Accelerated Thermal Cycling (HATC) Test for Solder Reliability Assessment in BGA Packages

2007 ◽  
Author(s):  
X. Long ◽  
I. Dutta ◽  
R. Guduru ◽  
R. Prasanna ◽  
M. Pacheco
Keyword(s):  
Thermal Cycling ◽  
Solder Joints ◽  
Low Cycle Fatigue ◽  
Inelastic Strain ◽  
Fatigue Reliability ◽  
Element Analysis ◽  
Mechanical Cycling ◽  
Experimental Apparatus ◽  
Dependent Strain ◽  
Accelerated Thermal Cycling

A thermo-mechanical loading system, which can superimpose a temperature and location dependent strain on solder joints, is proposed in order to conduct highly accelerated thermal-mechanical cycling (HATC) tests to assess thermal fatigue reliability of Ball Grid Array (BGA) solder joints in microelectronics packages. The application of this temperature and position dependent strain produces generally similar loading modes (shear and tension) encountered by BGA solder joints during service, but substantially enhances the inelastic strain accumulated during thermal cycling over the same temperature range as conventional ATC (accelerated thermal cycling) tests, thereby leading to a substantial acceleration of low-cycle fatigue damage. Finite element analysis was conducted to aid the design of experimental apparatus and to predict the fatigue life of solder joints in HATC testing. Detailed analysis of the loading locations required to produce failure at the appropriate joint (next to the die-edge ball) under the appropriate tension/shear stress partition are presented. The simulations showed that the proposed HATC test constitutes a valid methodology for further accelerating conventional ATC tests. An experimental apparatus, capable of applying the requisite loads to a BGA package was constructed, and experiments were conducted under both HATC and ATC conditions. It is shown that HATC proffers much reduced cycling times compared to ATC.

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