Assembly and Reliability Studies on Reworked and Non-Reworked QFN Packages

2009 ◽  
Author(s):  
Salil Pradhan ◽  
Francois Billaut ◽  
Sunil Gopakumar
Keyword(s):  
Thermal Cycling ◽  
Process Improvement ◽  
Cross Sections ◽  
Design Guidelines ◽  
Electrical Performance ◽  
Osp Surface Finish ◽  
Pattern Comparison ◽  
Construction Type ◽  
Penetration Tests ◽  
Rework Process

Quad Flat No lead (QFN) packages are being used as alternative components to some of the large form-factor packages due to their smaller footprint, improved thermal and electrical performance. During the past few years, there has been a surge of published papers by end users and component manufacturers on the topic of assembly and reliability of the QFN packages. Both empirical and simulation data has been published, which has helped several manufacturers to develop design guidelines and assembly processes for these packages. There exists a gap in the current published work on the assembly and reliability of high I/O count QFNs on thick boards. In addition, reliability of the rework process on QFNs is not well documented. Therefore, objectives of this research were the following: • Evaluate the second level reliability in thermal cycling for reworked and non-reworked QFNs; • Evaluate the reliability of different sized QFNs on 125 mil thick boards and compare with existing literature; • Failure analysis and recommendations for reliability improvement; • Land pattern comparison; and • Rework process improvement. Studies have been conducted on different QFN packages between 32 pins and 164 pins on 125 mil thick boards with Organic Solder Preservative (OSP) surface finish. Experimental design includes the use of different package sizes, alternate thermal pad patterns, and use of tin-lead versus lead free processes. A subset of some of the package types has also been reworked using variations of the standard BGA rework processes to evaluate its reliability. All packages were daisy chained. Boards were subjected to thermal cycling test between 0 to 100 deg C for 6000 hours. Data is analyzed using Weibull distribution. Failure mechanisms have been analyzed using dye penetration tests and cross sections. The reliability results are discussed in terms of package construction, type of land patterns and rework. Recommendations for process improvement are delineated.

Oxidation of Some Titanium Alloys in Air at Elevated Temperatures

2008 ◽  
Vol 595-598 ◽  
pp. 967-974 ◽  
Author(s):  
E. Godlewska ◽  
M. Mitoraj ◽  
B. Jajko
Keyword(s):  
Thermal Cycling ◽  
Titanium Alloys ◽  
Constant Temperature ◽  
Cross Sections ◽  
Elevated Temperatures ◽  
Mixed Oxides ◽  
Oxidation Mechanism ◽  
Testing Procedure ◽  
Oxidation Products ◽  
Outward Diffusion

This paper presents comparative studies on the performance of two titanium alloys (Ti- 6Al-1Mn, Ti-45.9Al-8Nb) in an oxidizing atmosphere at 700 oC and 800 oC. Testing procedure comprised thermogravimetric measurements at a constant temperature and in thermal cycling conditions (1-h and 20-h cycles at constant temperature followed by rapid cooling). The overall duration of the cyclic oxidation tests was up to 1000 hours. The oxidized specimens were analyzed in terms of chemical composition, phase composition, and morphology (SEM/EDS, TEM/EDS, XRD). The extent and forms of alloy degradation were evaluated on the basis of microscopic observation of specimen fractures and cross-sections. Selected specimens were examined by means of XPS, SIMS and GDS. Oxidation mechanism of Ti-46Al-8Nb was assessed a two-stage oxidation method using oxygen-18 and oxygen-16. Apparently, the oxidation of this alloy proceeded in several stages. According to XPS, already after quite short reaction time, the specimens were covered with a very thin oxide film, mainly composed of aluminum oxide (corundum). A thicker layer of titanium dioxide (rutile) developed underneath. These two layers were typical of the oxidation products formed on this alloy, even when tested in thermal cycling conditions. In general, the scale had a complex multilayer structure but it was thin and adherent. Under the continuous layer of titania, there was a fine-grained zone composed of mixed oxides. The alloy/scale interface was marked with niobium-rich precipitates embedded in a titanium-rich matrix. There were some indications of secondary processes occurring under the initial continuous oxide layers (e.g. characteristic layout of pores or voids). Thickness of inner scale layers clearly increased according to parabolic kinetics, while that of the outer compact layer (mainly TiO2) changed only slightly. The distribution of oxygen isotopes across the scale/alloy interface indicated two-way diffusion of the reacting species – oxygen inward and metals outward diffusion. Silicon deposited on Ti-6Al-1Mn alloy positively affected scale adhesion and remarkably reduced alloy degradation rate.

Design and Robustness of Quilt Packaging Superconnect

2012 ◽  
Vol 2012 (1) ◽  
pp. 000524-000530
Author(s):  
M. Ashraf Khan ◽  
Jason M. Kulick ◽  
Alfred M. Kriman ◽  
Gary H. Bernstein
Keyword(s):  
Thermal Cycling ◽  
High Speed ◽  
Low Cycle Fatigue ◽  
Simulation Models ◽  
Electrical Performance ◽  
Cycle Fatigue ◽  
Signal Delay ◽  
Thermal Reliability ◽  
Simulation Results ◽  
Quilt Packaging

Quilt Packaging (QP) is a novel high-speed superconnect (i.e. direct interchip interconnect), developed to improve electrical performance — signal delay, power loss, etc. Ultrahigh bandwidth has already been demonstrated for QP, but its unique structure requires thermal reliability issues to be studied. To this end, simulation models were developed to study the robustness of QP. QP structures were fabricated, and thermal cycling tests were performed focusing on the reliability for various shapes of nodules, the basic physical interconnect unit of QP. Simulations were performed to determine stress over a range of temperatures and estimate low cycle fatigue lifetimes. Simulations considered two types of solder and several adhesives. Thermal cycling experiments indicate that QP provides a robust structure, in agreement with the simulation results.

scholarly journals Innovative Design of Drone Landing Gear Used as a Receiving Coil in Wireless Charging Application

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3483 ◽  
Author(s):  
Tommaso Campi ◽  
Silvano Cruciani ◽  
Francesca Maradei ◽  
Mauro Feliziani
Keyword(s):  
Near Field ◽  
Base Station ◽  
Electrical Circuit ◽  
Design Guidelines ◽  
Landing Gear ◽  
Electrical Performance ◽  
Secondary Coil ◽  
Wireless Power ◽  
Innovative Solution ◽  
Aluminum Pipe

A near-field wireless power transfer (WPT) technology is applied to recharge the battery of a small size drone. The WPT technology is an extremely attractive solution to build an autonomous base station where the drone can land to wirelessly charge the battery without any human intervention. The innovative WPT design is based on the use of a mechanical part of the drone, i.e., landing gear, as a portion of the electrical circuit, i.e., onboard secondary coil. To this aim, the landing gear is made with an adequately shaped aluminum pipe that, after suitable modifications, performs both structural and electrical functions. The proposed innovative solution has a very small impact on the drone aerodynamics and the additional weight onboard the drone is very limited. Once the design of the secondary coil has been defined, the configuration of the WPT primary coil mounted in a ground base station is optimized to get a good electrical performance, i.e., high values of transferred power and efficiency. The WPT design guidelines of primary and secondary coils are given. Finally, a demonstrator of the WPT system for a lightweight drone is designed, built, and tested.

scholarly journals Performance Optimization of Polymer Fibre Actuators for Soft Robotics

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 454 ◽  
Author(s):  
Ivan D. Rukhlenko ◽  
Syamak Farajikhah ◽  
Charles Lilley ◽  
Andre Georgis ◽  
Maryanne Large ◽  
...  
Keyword(s):  
Cross Sections ◽  
Performance Optimization ◽  
Analytical Calculation ◽  
Design Guidelines ◽  
Soft Robotics ◽  
Positive Pressure ◽  
Cross Sectional ◽  
Bending Angle ◽  
Pneumatic Actuators ◽  
Wide Range

Analytical modeling of soft pneumatic actuators constitutes a powerful tool for the systematic design and characterization of these key components of soft robotics. Here, we maximize the quasi-static bending angle of a soft pneumatic actuator by optimizing its cross-section for a fixed positive pressure inside it. We begin by formulating a general theoretical framework for the analytical calculation of the bending angle of pneumatic actuators with arbitrary cross-sections, which is then applied to an actuator made of a circular polymer tube and an asymmetric patch in the shape of a hollow-cylinder sector on its outer surface. It is shown that the maximal bending angle of this actuator can be achieved using a wide range of patches with different optimal dimensions and approximately the same cross-sectional area, which decreases with pressure. We also calculate the optimal dimensions of thin and small patches in thin pneumatic actuators. Our analytical results lead to clear design guidelines, which may prove useful for engineering and optimization of the key components of soft robotics with superior features.

scholarly journals Assessment of Standards and Codes Dedicated to CFRP Confinement of RC Columns

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2390 ◽  
Author(s):  
Stefan Kaeseberg ◽  
Dennis Messerer ◽  
Klaus Holschemacher
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Rupture Strength ◽  
Axial Strain ◽  
Design Guidelines ◽  
International Standards ◽  
National Standards ◽  
Rc Columns ◽  
New Findings ◽  
Cfrp Confinement

Reinforced concrete (RC) columns are often placed under confinement to increase their strength and ductility. Carbon fiber reinforced polymer (CFRP) materials have recently been recognized as favorable confinement systems. At present, a number of national standards and codes dedicated to the design of concrete components strengthened with CFRP in general and CFRP confinement in particular are available. These sets of rules provide design equations for confined reinforced concrete columns with circular and rectangular cross sections. Most of the standards and codes exhibit significant differences, including the used predictive models, limitations, observed effects and covered loading conditions. In this paper, five international standards and design guidelines are introduced and discussed. The purpose is to present a constructive and critical assessment of the state-of-the-art design methodologies available for CFRP confined RC columns and to discuss effects not previously considered properly. Therefore, some recent research efforts and findings from the Leipzig University of Applied Sciences are also introduced. The obtained data is used for a comparative study of the guideline predictive equations. Furthermore, it is shown that some new findings concerning the rupture strength and the maximum strength plus accompanying axial strain of a CFRP confined column are suitable to improve the current guidelines.

Investigation of Oxide-Nucleation on Ferritic FeCr Interconnect Alloys for Solid Oxide Fuel Cells Exposed to Anode and Cathode Gases at 850°C

2008 ◽  
Vol 595-598 ◽  
pp. 779-787
Author(s):  
Georg Kunschert ◽  
Hans Peter Martinz ◽  
Michael Schütze
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Thermal Cycling ◽  
Oxide Scale ◽  
Cross Sections ◽  
Scale Formation ◽  
Solid Oxide ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Fuel

In recent years solid-oxide fuel cell (SOFC) interconnect components have proven to be a key-component accountable for the functionality of high temperature fuel cells. Amongst adequate thermal expansion and high temperature strength, highest oxidation resistance in anode and cathode gases under thermal cycling conditions is required in order to reach long term durability, particularly when using thin film light-weight components with particular focus on automotive applications. In order to match the challenging parameter profile Plansee developed the mechanically alloyed ITM, a ferritic P/M Fe26Cr alloy strengthened with additions of Y2O3 dispersoids, since it has been observed that apart from their HT strengthening effect, which is of specific interest for thin sheets components, finest ODS particles reduce the growth and enhance the adhesion of the forming oxide layers. The latter effect is of particular interest in applications where alloys are exposed to HT cyclic conditions. In this work the nucleation phase of the oxide scale formation on P/M ODS Fe26Cr ITM is compared to that on a reference ingot steel Fe22Cr in typical anode gases containing significant amounts of H2, CO and approximately 3% H2O as well as in laboratory air at 850°C. Thermal cycling oxidation tests following the COTEST standard up to 168h are carried out in both environments. Moreover cyclic oxidation tests are performed in dry anode gas. Detailed studies of oxide scale formation and evolution by means of electron microscopy of cross sections as well as oxide surfaces are undertaken.

Experimental and Numerical Investigation of the Reliability of Double-Sided Area Array Assemblies

2006 ◽  
Vol 128 (4) ◽  
pp. 441-448 ◽  
Author(s):  
S. Chaparala ◽  
J. M. Pitarresi ◽  
S. Parupalli ◽  
S. Mandepudi ◽  
M. Meilunas
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Printed Circuit Board ◽  
Solder Joints ◽  
Mirror Image ◽  
Circuit Board ◽  
Thermal Dissipation ◽  
Electrical Performance ◽  
Area Array ◽  
Plastic Ball

One of the primary advantages of surface mount technology (SMT) over through-hole technology is that SMT allows the assembly of components on both sides of the printed circuit board (PCB). Currently, area array components such as ball grid array (BGA) and chip-scale package (CSP) assemblies are being used in double-sided configurations for network and memory device applications as they reduce the routing space and improve electrical performance (Shiah, A. C., and Zhou, X., 2002, “A Low Cost Reliability Assessment for Double-Sided Mirror-Imaged Flip Chip BGA Assemblies,” Proceedings of the Seventh Annual Pan Pacific Microelectronics Symposium, Maui, Hawaii, pp. 7–15, and Xie, D., and Yi, S., 2001, “Reliability Design and Experimental work for Mirror Image CSP Assembly”, Proceedings of the International Symposium on Microelectronics, Baltimore, October, pp. 417–422). These assemblies typically use a “mirror image” configuration wherein the components are placed on either side of the PCB directly over each other; however, other configurations are possible. Double-sided assemblies pose challenges for thermal dissipation, inspection, rework, and thermal cycling reliability. The scope of this paper is the study of the reliability of double-sided assemblies both experimentally and through numerical simulation. The assemblies studied include single-sided, mirror-imaged, 50% offset CSP assemblies, CSPs with capacitors on the backside, single-sided, mirror-imaged plastic ball grid arrays (PBGAs), quad flat pack (QFP)/BGA mixed assemblies. The effect of assembly stiffness on thermal cycling reliability was investigated. To assess the assembly flexural stiffness and its effect on the thermal cycling reliability, a three-point bending measurement was performed. Accelerated thermal cycling cycles to failure were documented for all assemblies and the data were used to calculate the characteristic life. In general, a 2X to 3X decrease in reliability was observed for mirror-image assemblies when compared to single-sided assemblies for both BGAs and CSPs on 62mil test boards. The reliability of mirror-image assemblies when one component was an area array device and the other was a QFP was comparable to the reliability of the single-sided area array assemblies alone, that is, the QFP had almost no influence on the double-sided reliability when used with an area array component. Moiré interferometry was used to study the displacement distribution in the solder joints at specific locations in the packages. Data from the reliability and moiré measurements were correlated with predictions generated from three-dimensional finite element models of the assemblies. The models incorporated nonlinear and time-temperature dependent solder material properties and they were used to estimate the fatigue life of the solder joints and to obtain an estimate of the overall package reliability using Darveaux’s crack propagation method.

Finite Element Analysis of <img src="/images/tex/20750.gif" alt="\hbox {Nb}_{3}\hbox {Sn}"> Sub-Cables Under Transverse Compression With Different Approaches

2013 ◽  
Vol 23 (3) ◽  
pp. 8400705-8400705 ◽  
Author(s):  
Tiening Wang ◽  
Luisa Chiesa ◽  
Makoto Takayasu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cross Sections ◽  
Load Distribution ◽  
Strain State ◽  
Transverse Load ◽  
Electrical Performance ◽  
Flat Plates ◽  
Element Analysis ◽  
Mechanical Loads

Currently, very few experimental results describing the behavior of Nb3Sn subcables under transverse load are available. Those results are of importance for predicting how a full-sized cable-in-conduit conductor behaves during operations. Current experimental devices used to study the effect of transverse load on the electrical performance of cables utilize concave plates to apply mechanical loads and contain the sample and subject it to mechanical loads that mimic the electromagnetic loads of full-sized cables during operation. From finite element analysis, it is found that the strain state in the strands of a triplet is greatly affected by the shape of the pressing element contact surface. We will discuss the strain state within the strands from the simulations using two pressing configurations: concave and flat plates. The strain state in each strand in a twisted triplet is investigated by considering two cross-sections of a triplet along the length of the cable. Those results can provide useful information on the electrical performance of each strand based on its location along the axis. It is verified that the load distribution is very different depending on the shape of the pressing plates.

Reliability of Ceramic Column Grid Array (CCGA717) Interconnect Packages Under Extreme Temperatures for Space Applications*

2010 ◽  
Vol 7 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Rajeshuni Ramesham
Keyword(s):  
Thermal Cycling ◽  
Experimental Test ◽  
High Reliability ◽  
Extreme Temperature ◽  
Electrical Performance ◽  
Extreme Temperatures ◽  
Thermal Cycles ◽  
Space Applications ◽  
Temperature Range

Ceramic column grid array packages have been increasing in use based on their advantages such as high interconnect density, very good thermal and electrical performance, compatibility with standard surface-mount packaging assembly processes, and so on. CCGA packages are used in space applications such as in logic and microprocessor functions, telecommunications, flight avionics, and payload electronics. As these packages tend to have less solder joint strain relief than leaded packages, the reliability of CCGA packages is very important for short-term and long-term space missions. CCGA interconnect electronic package printed wiring boards (PWBs) of polyimide have been assembled, inspected nondestructively, and subsequently subjected to extreme temperature thermal cycling to assess the reliability for future deep space, short- and long-term, extreme temperature missions. In this investigation, the employed temperature range covers from −185°C to +125°C extreme thermal environments. The test hardware consists of two CCGA717 packages with each package divided into four daisy-chained sections, for a total of eight daisy chains to be monitored. The CCGA717 package is 33 mm × 33 mm with a 27 × 27 array of 80%/20% Pb/Sn columns on a 1.27 mm pitch. The resistance of daisy-chained, CCGA interconnects was continuously monitored as a function of thermal cycling. Electrical resistance measurements as a function of thermal cycling are reported and the tests to date have shown significant change in daisy chain resistance as a function of thermal cycling. The change in interconnect resistance becomes more noticeable as the number of thermal cycles increases. This paper will describe the experimental test results of CCGA testing under extreme temperatures. Standard Weibull analysis tools were used to extract the Weibull parameters to understand the CCGA failures. Optical inspection results clearly indicate that the solder joints of columns with the board and the ceramic package have failed as a function of thermal cycling. The first failure was observed at the 137th thermal cycle and 63.2% failures of daisy chains have occurred by about 664 thermal cycles. The shape parameter extracted from the Weibull plot was about 1.47, which indicates the failures were related to failures that occurred during the flat region or useful life region of the standard bathtub curve. Based on this experimental test data, one can use the CCGAs for the temperature range studied for ∼100 thermal cycles (ΔT = 310°C, 5°C/minute, and 15 min dwell) with a high degree of confidence for high reliability space and other applications.

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