Heat Sink Induced Thermomechanical Joint Strain in QFN Devices

2014 ◽  
Vol 11 (2) ◽  
pp. 80-86
Author(s):  
Gerard McVicker ◽  
Vijay Khanna ◽  
M. Sri-Jayantha
Keyword(s):  
Solder Joint ◽  
Heat Sink ◽  
Power Distribution ◽  
Strain Energy ◽  
Heat Dissipation ◽  
Coefficient Of Thermal Expansion ◽  
Inelastic Strain ◽  
Temperature Cycling ◽  
Image Correlation ◽  
Solder Joint Fatigue

A blade server system (BSS) utilizes voltage regulator modules (VRMs), in the form of quad flat no-lead (QFN) devices, to provide power distribution to various components on the system board. Depending on the power requirements of the circuit, these VRMs can be mounted as single devices or banked together. In addition, the power density of the VRM can be high enough to warrant heat dissipation through the use of a heat sink. Typically, at field conditions (FCs), the BSS are powered on and off up to four times per day, with their ambient temperature cycling between 25°C and 80°C. This cyclical temperature gradient drives inelastic strain in the solder joints due to the coefficient of thermal expansion (CTE) mismatch between the QFN and the circuit card. In addition, the heat sink, coupled with the QFN and the circuit card, can induce additional inelastic solder joint strain, resulting in early solder joint fatigue failure. To understand the effect of the heat sink mounting, a FEM (finite element model) of four QFNs mounted to a BSS circuit card was developed. The model was exercised to calculate the maximum strain energy in a critical joint due to cyclic strain, and the results were compared for a QFN with and without a heat sink. It was determined that the presence of the heat sink did contribute to higher strain energy and therefore could lead to earlier joint failure. Although the presence of the heat sink is required, careful design of the mounting should be employed to provide lateral slip, essentially decoupling the heat sink from the QFN joint strain. Details of the modeling and results, along with DIC (digital image correlation) measurements of heat sink lateral slip, are presented.

Heat Sink Induced Thermo-Mechanical Joint Strain in QFN Devices

2013 ◽  
Vol 2013 (1) ◽  
pp. 000467-000472
Author(s):  
Gerard McVicker ◽  
Vijay Khanna ◽  
Sri M. Sri-Jayantha
Keyword(s):  
Solder Joint ◽  
Heat Sink ◽  
Power Distribution ◽  
Strain Energy ◽  
Heat Dissipation ◽  
Coefficient Of Thermal Expansion ◽  
Inelastic Strain ◽  
Temperature Cycling ◽  
Image Correlation ◽  
Solder Joint Fatigue

A Blade Server System (BSS) utilizes Voltage Regulator Modules (VRM), in the form of Quad Flat No-Lead (QFN) devices, to provide power distribution to various components on the system board. Depending on the power requirements of the circuit, these VRM's can be mounted as single devices or banked together. In addition, the power density of the VRM can be high enough to warrant heat dissipation through the use of a heat sink. Typically, during field conditions (FC) the BSS are powered on and off up to four times per day, with their ambient temperature cycling between 25°C and 80°C. This cyclical temperature gradient drives inelastic strain in the solder joints due to the coefficient of thermal expansion (CTE) mismatch between the QFN and the circuit card. In addition, the heat sink, coupled to the QFN and the circuit card, can induce additional inelastic solder joint strain, resulting in early solder joint fatigue failure. To understand the effect of the heat sink mounting, a FEM (Finite Element Model) of four QFN's mounted to a BSS circuit card was developed. The model was exercised to calculate the maximum strain energy in a critical joint, due to the cyclical straining, and the results were compared for a QFN with and without a heat sink. It was determined that the presence of the heat sink did contribute to higher strain energy and therefore could lead to earlier joint failure. While the presence of the heat sink is required, careful design of the mounting should be employed to provide lateral slip, essentially decoupling the heat sink from the QFN joint strain. Details of the modeling and results, along with DIC (Digital Image Correlation) measurements of heat sink lateral slip, are presented.

Thermal Fatigue Prediction for Leadless Solder Joint of TFBGA

2006 ◽  
Author(s):  
Chia-Lung Chang ◽  
Tzu-Jen Lin ◽  
Chih-Hao Lai
Keyword(s):  
Energy Density ◽  
Solder Joint ◽  
Creep Strain ◽  
Thermal Fatigue ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Creep Property ◽  
Inelastic Strain ◽  
Temperature Cycling ◽  
Element Analysis

Nonlinear finite element analysis was performed to predict the thermal fatigue for leadless solder joint of TFBGA Package under accelerated TCT (Temperature Cycling Test). The solder joint was subjected to the inelastic strain that was generated during TCT due to the thermal expansion mismatch between the package and PCB. The solder was modeled with elastic-plastic-creep property to simulate the inelastic deformation under TCT. The creep strain rate of solder was described by double power law. The furthest solder away from the package center induced the highest strain during TCT was considered as the critical solder ball to be most likely damaged. The effects of solder meshing on the damage parameters of inelastic strain range, accumulated creep strain and creep strain energy density were compared to assure the accuracy of the simulation. The life prediction equation based on the accumulated creep strain and creep strain energy density proposed by Syed was used to predict the thermal fatigue life in this study. The agreement between the prediction life and experimental mean life is within 25 per cent. The effect of die thickness and material properties of substrate on the life of solder was also discussed.

A Systems Approach to Solder Joint Fatigue in Spacecraft Electronic Packaging

1991 ◽  
Vol 113 (2) ◽  
pp. 121-128 ◽  
Author(s):  
R. G. Ross
Keyword(s):  
Solder Joint ◽  
Electronic Packaging ◽  
Thermal Cycle ◽  
Systems Approach ◽  
High Reliability ◽  
Temperature Cycling ◽  
Failure Behavior ◽  
Acceptance Test ◽  
Solder Fatigue ◽  
Solder Joint Fatigue

Differential expansion induced fatigue resulting from temperature cycling is a leading cause of solder joint failures in spacecraft. Achieving high reliability flight hardware requires that each element of the fatigue issue be addressed carefully. This includes defining the complete thermal-cycle environment to be experienced by the hardware, developing electronic packaging concepts that are consistent with the defined environments, and validating the completed designs with a thorough qualification and acceptance test program. This paper describes a useful systems approach to solder fatigue based principally on the fundamental log-strain versus log-cycles-to-failure behavior of fatigue. This fundamental behavior has been useful to integrate diverse ground test and flight operational thermal-cycle environments into a unified electronics design approach. Each element of the approach reflects both the mechanism physics that control solder fatigue, as well as the practical realities of the hardware build, test, delivery, and application cycle.

DIC Based Investigation Into the Effect of Mean Temperature of Thermal Cycle on the Strain State in SnAgCu Solder Joint

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Kazi Mirza ◽  
Jeff Suhling
Keyword(s):  
Solder Joint ◽  
Thermal Fatigue ◽  
Thermal Cycle ◽  
Strain State ◽  
High Reliability ◽  
Image Correlation ◽  
Harsh Environment ◽  
Fatigue Reliability ◽  
Mean Temperature ◽  
Solder Joint Fatigue

Electronics in high reliability applications may be subjected to cyclic thermo-mechanical loads after being deployed for extended periods of time in harsh environment. Cyclic thermal excursion may result in solder joint fatigue leading to failure. Previous researchers have shown that exposure to high temperature for extended periods of time results in evolution of the mechanical properties of SnAgCu alloys. Deployment of leadfree electronics in harsh environment applications may result in exposure to a multitude of thermal cycles. The effect of cyclic thermal range and thermal aging on the thermal fatigue reliability has been widely documented; however the effect of the mean temperature on the thermal fatigue reliability and the strain evolution of during cyclic exposure has not been studied. In this paper, an experimental investigation has been undertaken using digital image correlation to quantify the evolution in the strain state under different mean temperatures and cyclic thermal intervals. Three different test vehicles, BGA 144, 256 and 324 were used in this study under three different test conditions 50–150°C, 0–100°C and −50–50°C. A framework to evaluate the effect of mean temperature of thermal cycle has been developed.

The Effect of Intermetallic Compound in Solder Joint Fatigue Life Prediction Using Finite Element Modeling

2003 ◽  
Author(s):  
Mohammad Masum Hossain ◽  
Dereje Agonafer ◽  
Puligandla Viswanadham ◽  
Tommi Reinikainen
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Intermetallic Compound ◽  
Solder Joint ◽  
Finite Element Modeling ◽  
Life Prediction ◽  
Temperature Cycling ◽  
Fatigue Life Prediction ◽  
Element Modeling ◽  
Solder Joint Fatigue

The life-prediction modeling of an electronic package requires a sequence of critical assumptions concerning the finite element models. The solder structures accommodate the bulk of the plastic strain that is generated during accelerated temperature cycling due to the thermal expansion mismatch between the various materials that constitute the package. Finite element analysis is extensively used for simulating the effect of accelerated temperature cycling on electronic packages. There are a number of issues that need to be addressed to improve the current FEM models. One of the limitations inherent to the presently available models is the accuracy in property values of eutectic 63Sn/37Pb solder or other solder materials (i.e. 62Sn/36Pb/2Ag). Life prediction methodologies for high temperature solders (90Pb/10Sn, 95Pb/5Sn, etc.) or lead-free based inter-connects materials, are almost non-existent due to their low volume use or relative infancy. [1] Another major limitation for the models presently available is excluding the effect of intermetallic compound (Cu6Sn5, Cu3Sn) formation and growth between solder joint and Cu pad due to the reflow processes, rework and during the thermal aging. The mechanical reliability of these intermetallic compounds clearly influences the mechanical integrity of the interconnection. The brittle failures of solder balls have been identified with the growth of a number of intermetallic compounds both at the interfaces between metallic layers and in the bulk solder balls. In this paper, the effect of intermetallic compound in fatigue life prediction using finite element modeling is described. A Chip Scale Package 3D Quarter model is chosen to do the FE analysis. Accelerated temperature cycling is performed to obtain the plastic work due to thermal expansion mismatch between the various materials. Solder joint fatigue life prediction methodologies were incorporated so that finite element simulation results were translated into estimated cycles to failure. The results are compared with conventional models that do not include intermetallic effects. Conventionally available material properties are assumed for the eutectic 63Sn/37Pb solder and the intermetallic material properties. The importance of including intermetallic effect in finite element modeling will be discussed.

Effect of Compressive Loading on the Interconnect Reliability Under Thermal Cycling

2011 ◽  
Author(s):  
Da Yu ◽  
Tung Nguyen ◽  
Ho H. Lee ◽  
Namseo Goo ◽  
S. B. Park
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Power Density ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Failure Modes ◽  
Failure Time ◽  
Compressive Loading ◽  
Interfacial Thermal Resistance ◽  
Interconnect Reliability

The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove the heat away from the device. A compressive loading was applied to reduce the interfacial thermal resistance between package and heat sink. In this study both numerical modeling and experimental approaches were employed to study the effect of compressive loading on the interconnect reliability, especially for high power density package, under thermal cycling loading conditions. The JEDEC standard thermal cycle tests were conducted and the resistance of the daisy chained circuits was in-situ measured to record the failure time. The failure analysis has been performed to indentify the failure modes of solder joint with and without the presence of compressive loading. A finite element based thermal fatigue life prediction model for SAC305 solder joint under compressive loading was also developed and validated with the experimental results.

Key Parameters Affecting Solder Joint Life of Chip Resistors and Chip Capacitors Mounted on Insulated Metal Substrate

2000 ◽  
Author(s):  
Nicoletta Sangalli ◽  
Donald B. Barker
Keyword(s):  
Solder Joint ◽  
Heat Dissipation ◽  
Coefficient Of Thermal Expansion ◽  
Metal Substrate ◽  
Design Guidelines ◽  
Element Analysis ◽  
Dielectric Thickness ◽  
Component Size ◽  
Board Material ◽  
Temperature Ranges

Abstract Aluminum insulated metal substrate (IMS) is often used as an alternative to FR-4 to enhance heat dissipation in high power applications. Although IMS offers better heat dissipation, the solder joint life of leadless chip resistors and chip capacitors under thermal cycling can decrease. This is due to the higher mismatch of the coefficient of thermal expansion between the ceramic based components and the aluminum board. This paper has two main objectives. One is to investigate the sensitivity of solder joint life of ceramic chip capacitor and chip resistor mounted on IMS to variations in dielectric thickness, board material, and solder thickness on. This sensitivity analysis is conducted with finite element analysis (FEA) simulation. The other objective is to determine the solder joint life for different resistor sizes at different temperature ranges with FEA modeling and experiment data. These results are presented in terms of design guidelines to be used in the selection of component size, board material, and temperature ranges, given an expected solder joint life.

scholarly journals Reliability Assessment of Preloaded Solder Joint Under Thermal Cycling

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Da Yu ◽  
Hohyung Lee ◽  
Seungbae Park
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Thermal Fatigue ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Failure Modes ◽  
Compressive Loading ◽  
Interfacial Thermal Resistance ◽  
Sac305 Solder

The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive loading is usually applied to reduce the interfacial thermal resistance between package and heat sink. In this paper, both experimental approaches and numerical modeling were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling conditions. A special loading fixture which simulated the heat sink was designed to apply compressive loading to the package. The JEDEC standard thermal cycle tests were performed and the resistance of daisy chained circuits was in situ measured. The time to crack initiation and time to permanent failure were identified separately based on in situ resistance measurement results. Failure analysis has been performed to identify the failure modes of solder joint with and without the presence of compressive loading. A finite element based thermal-fatigue life prediction model for SAC305 solder joint under compressive loading was also developed to understand the thermal-fatigue crack behaviors of solder joint and successfully validated with the experimental results.

scholarly journals Probabilistic methodology for reliability assessment of electronic packages

2019 ◽  
Vol 286 ◽  
pp. 02002
Author(s):  
H. Hamdani ◽  
B. Radi ◽  
A. El Hami
Keyword(s):  
Solder Joint ◽  
Reliability Assessment ◽  
Temperature Cycling ◽  
Time Dependent ◽  
Electronic Packages ◽  
Finite Element Analyses ◽  
Material Parameters ◽  
Joint Reliability ◽  
Design Variables ◽  
Solder Joint Fatigue

In the mechatronic devices, the finite element analyses are the most used method to determine time-dependent solder joint fatigue response under accelerated temperature cycling conditions, the deterministic analyses are the most used methods. However, the design variables show variability and randomness which will affect the lifetime prediction quality. This paper focuses on solder joint reliability in tape-based chip-scale packages(CSP) with the consideration of uncertainties in material parameters.

Sign in / Sign up

Export Citation Format

Share Document