Electronics Manufacturing Technical Articles

BVA: Molded Cu Wire Contact Solution for Very High Density Package-on- Package (PoP) Applications

Jan 28, 2015 | Vern Solberg, Ilyas Mohammed

Stacking heterogeneous semiconductor die (memory and logic) within the same package outline can be considered for less complex applications but combining the memory and processor functions in a single package has compromised test efficiency and overall package assembly yield. Separation and packaging the semiconductor functions into sections, on the other hand, has proved to be more efficient and, even though two interposers are required, more economical. The separated logic and memory sections are configured with the same uniform outline for vertical stacking (package-on-package). The most common configuration places the logic section as the base with second tier memory section soldered to a mating contact pattern.

This paper addresses the primary technological challenges for reducing contact pitch and package-on-package interface technology....

Publisher: Invensas Corporation

Radar Control Terminal (RCT) units

Jan 26, 2015 | Ensil

In 2005 Raytheon Technical Services Company, now Raytheon Information, Intelligence and Services (Raytheon IIS), approached Ensil regarding the repair of their manufactured Radar Control Terminal (RCT) units. The RCT TRS P/N 13563090-2, a key component in the AN/MPQ-64 Sentinel System, consisted of outdated parts which caused minor to major unit failures. Ensil repaired the RCT's at every turn, correcting any component with the parts still in circulation (mother boards, displays, power supplies) to provide the client with the best available technology. These repairs were completed to military standards and kept the RCT effective, allowing for the Sentinel radar to remain operational. However, the supply of outdated parts was eventually no longer available. Ensil offered the best possible solution, utilizing the skills of their knowledgeable engineering staff, they would reverse engineer a new computer to replace the obsolete RCT while maintaining the same form, fit and function....

Publisher: Ensil

High Temperature Ceramic Capacitors for Deep Well Applications

Jan 22, 2015 | R. Phillips, J. Bultitude, A. Gurav, K. Park, S. Murillo, P. Flores, M. Laps.

Temperature requirements for ceramic capacitors have increased significantly with recent advances in deep-well drilling technology. Increasing demand for oil and natural gas has driven the technology to deeper and deeper deposits resulting in extreme temperature environments up to 200°C and above. A novel capacitor solution utilizing temperature-stable base-metal electrode capacitors in a molded and leaded package addresses the growing market high temperature demands of (1) capacitance stability, (2) long service life, and (3) mechanical durability. A range of high temperature C0G capacitors capable of meeting this 200°C and above high temperature environment has been developed.

This paper will review the electrical, reliability, and mechanical performance of this new capacitor solution...

Publisher: KEMET Electronics Corporation

Automotive Safety Systems Driving Growth in Automotive Sensor Cable Assemblies

Jan 12, 2015 | Pete Doyon, VP, Product Management, Schleuniger Inc.

V2V is a collision avoidance technology that transmits data between vehicles to help warn drivers of potential crashes. This technology would improve safety by allowing vehicles to communicate with each other and exchange basic safety data, such as position and speed and warn the driver of potentially dangerous situations....

Publisher: Schleuniger, Inc.

The Effect of Pb Mixing Levels on Solder Joint Reliability and Failure Mode of Backward Compatible, High Density Ball Grid Array Assemblies

Jan 08, 2015 | Richard Coyle, Richard Popowich, Debra Fleming, Peter Read - Alcatel Lucent, Raiyo Aspandiar, Vasu Vasudevan, Steve Tisdale - Intel Corporation, Iulia Muntele - Sanmina Corporation.

Regardless of the accelerating trend for design and conversion to Pb-free manufacturing, many high reliability electronic equipment producers continue to manufacture and support tin-lead (SnPb) electronic products. Certain high reliability electronic products from the telecommunication, military, and medical sectors manufacture using SnPb solder assembly and remain in compliance with the RoHS Directive (restriction on certain hazardous substances) by invoking the European Union Pb-in-solder exemption.

Sustaining SnPb manufacturing has become more challenging because the global component supply chain is converting rapidly to Pb-free offerings and has a decreasing motivation to continue producing SnPb product for the low-volume, high reliability end users. Availability of critical, larger SnPb BGA components is a growing concern...

Publisher: Sanmina-SCI

The Last Will And Testament of the BGA Void

Jan 05, 2015 | Dave Hillman, Dave Adams, Tim Pearson, Brad Williams, Brittany Petrick, Ross Wilcoxon - Rockwell Collins, Dr. David Bernard, John Travis, Dr. Evstatin Krastev, Vineeth Bastin - Nordson Dage.

The impact of voiding on the solder joint integrity of ball grid arrays (BGAs)/chip scale packages (CSPs) can be a topic of lengthy and energetic discussion. Detailed industry investigations have shown that voids have little effect on solder joint integrity unless they fall into specific location/geometry configurations. These investigations have focused on thermal cycle testing at 0°C-100°C, which is typically used to evaluate commercial electronic products.

This paper documents an investigation to determine the impact of voids in BGA and CSP components using thermal cycle testing (-55°C to +125°C) in accordance with the IPC-9701 specification for tin/lead solder alloys. This temperature range is more typical of military and other high performance product use environments. A proposed BGA void requirement revision for the IPC-JSTD-001 specification will be extracted from the results analysis....

Publisher: Rockwell Collins

Profiled Squeegee Blade: Rewrites the Rules for Angle of Attack

Dec 24, 2014 | Ricky Bennett, Rich Lieske - Lu-Con Technologies, Corey Beech - RiverBend Electronics

For centuries, the squeegee blade has been used throughout many applications for depositing viscous materials through screens and stencils to transfer images on to substrates, from cloth material to electronic circuit boards. One area of blade printing mechanics that have been reviewed many times is the angle of attack of the blade. Typically it has been tested from 45 degrees to 60 degrees to optimize the printing quality and efficiency. However, this typically ends up as a compromise, from fill characteristics (45 degrees) to print definition (60 degrees). This paper will present the revolutionary performance of the profiled squeegee blade, which has recently been developed to create a virtual multi angle of attack for unsurpassed process control for all types of stencil printing processes....

Publisher: Lu-Con Technologies

Head in Pillow X-ray Inspection at Flextronics

Dec 18, 2014 | Alejandro Castellanos, Adalberto Gutierrez, Gilberto Martin, Matthew Vandiver, Ranga Dematampitiya, Hung Le, Elliott Le, Phuong Chau, Hao Cui, An Qi Zhao, Wei Bing Qian, Fuqing Li, Jacky Yao, Jiyang Zhang, Leonard Brisan, Cristian Gurka, Shane Young

Manufacturing technology faces challenges with new packages/process when confronting the need for high yields. Identifying product defects associated with the manufacturing process is a critical part of electronics manufacturing. In this project, we focus on how to use AXI to identify BGA Head-in-Pillow (HIP), which is challenging for AXI testing. Our goal is to help us understand the capabilities of current AXI machines....

Publisher: Flex (Flextronics International)

Failure Modes in Wire bonded and Flip Chip Packages

Dec 11, 2014 | Mumtaz Y. Bora

The growth of portable and wireless products is driving the miniaturization of packages resulting in the development of many types of thin form factor packages and cost effective assembly processes. Wire bonded packages using conventional copper lead frame have been used in industry for quite some time. However, the demand for consumer electronics is driving the need for flip chip interconnects as these packages shorten the signals, reduce inductance and improve functionality as compared to the wire bonded packages. The flip chip packages have solder bumps as interconnects instead of wire bonds and typically use an interposer or organic substrate instead of a metal lead frame (...)

The paper provides a general overview of typical defects and failure modes seen in package assembly and reviews the efforts needed to understand new failure modes during package assembly. The root cause evaluations and lessons learned as the factory transitioned to thin form factor packages are shared...

Publisher: Peregrine Semiconductor

Metal-based Inkjet Inks for Printed Electronics

Dec 04, 2014 | Alexander Kamyshny, Joachim Steinke, Shlomo Magdassi

A review on applications of metal-based inkjet inks for printed electronics with a particular focus on inks containing metal nanoparticles, complexes and metallo-organic compounds. The review describes the preparation of such inks and obtaining conductive patterns by using various sintering methods: thermal, photonic, microwave, plasma, electrical, and chemically triggered. Various applications of metal-based inkjet inks (metallization of solar cell, RFID antennas, OLEDs, thin film transistors, electroluminescence devices) are reviewed....

Publisher: Hebrew University of Jerusalem

Preparation, Manufacturing Lead-Free Soldering Alloy

Nov 28, 2014 | Tarik Talib Issa, Asmaa Shawky Khalil

A soldering alloy composition Sn40-Bi60 has been manufactured by quenching method to achieve the both cast and wire shape. Differential scanning calorimetric (DSC) was done to study the melting behavior for a large portion of the alloy melts sharply at a approximately 136 C0 ,the melting point of Sn-Bi. X-Ray diffraction and optical microscopy were used to analyzed its microstructure characterization. The hardness of the alloys has been tested and find at a value 2 HRB as ductile form....

Publisher: University of Baghdad

Effects of Packaging Materials on the Lifetime of LED Modules Under High Temperature Test

Nov 18, 2014 | Lei Nie, Wenjing Xiang - Hubei University of Technology, Mingxiang Chen, Huajing Li, Quan Chen - Huazhong University of Science and Technology

Performance degradation of packaging material is an important reason for the lifetime reduction of LED. In order to understanding the failure behavior of packaging material, silicone and phosphor were chosen to fabricate LED samples within which an aging test at 125℃ was performed. The result of online luminance measurement showed that LED samples with both silicone and phosphor had the highest luminance decay rate among all test samples because the carbonization of silicone and the consequent outgassing reduced the luminance quickly. The result of the luminance variance with test time was analyzed and an exponential decay model was developed with which the lifetime of LED under high temperature could be estimated....

Publisher: Hubei University of Technology

Advanced Thermal Management Solutions on PCBs for High Power Applications

Nov 13, 2014 | Gregor Langer, Markus Leitgeb - Austria Technologie & Systemtechnik AG, Johann Nicolics, Michael Unger - Vienna University of Technology, Hans Hoschopf, Franz P. Wenzl - Joanneum Research Forschungsgesm.b.H.

With increasing power loss of electrical components, thermal performance of an assembled device becomes one of the most important quality factors in electronic packaging. Due to the rapid advances in semiconductor technology, particularly in the regime of high-power components, the temperature dependence of the long-term reliability is a critical parameter and has to be considered with highest possible care during the design phase (...)

The aim of this paper is to give a short overview about standard thermal solutions like thick copper, thermal vias, plugged vias or metal core based PCBs. Furthermore, attention will be turned on the development of copper filled thermal vias in thin board constructions......

Publisher: Tridonic GmbH & Co KG

Effect of Process Variations on Solder Joint Reliability for Nickel-based Surface Finishes

Nov 06, 2014 | Hugh Roberts, Sven Lamprecht, Gustavo Ramos, Christian Sebald

This paper summarizes the results of recent investigations to examine the effect of electroless nickel process variations with respect to Pb-free (Sn-3.0Ag-0.5Cu) solder connections. These investigations included both ENIG and NiPd as surface finishes intended for second level interconnects in BGA applications. Process variations that are suspected to weaken solder joint reliability, including treatment time and pH, were used to achieve differences in nickel layer composition. Immersion gold deposits were also varied, but were directly dependent upon the plated nickel characteristics. In contrast to gold, different electroless palladium thicknesses were independently achieved by treatment time adjustments....

Publisher: Atotech

Solder Joint Reliability Under Realistic Service Conditions

Oct 30, 2014 | P. Borgesen, S. Hamasha, M. Obaidat, V. Raghavan, X. Dai; Department of Systems Science & Industrial Engineering, Binghamton University, M. Meilunas, M. Anselm; Universal Instruments Corporation.

The ultimate life of a microelectronics component is often limited by failure of a solder joint due to crack growth through the laminate under a contact pad (cratering), through the intermetallic bond to the pad, or through the solder itself. Whatever the failure mode proper assessments or even relative comparisons of life in service are not possible based on accelerated testing with fixed amplitudes, or random vibration testing, alone. Effects of thermal cycling enhanced precipitate coarsening on the deformation properties can be accounted for by microstructurally adaptive constitutive relations, but separate effects on the rate of recrystallization lead to a break-down in common damage accumulation laws such as Miner's rule. Isothermal cycling of individual solder joints revealed additional effects of amplitude variations on the deformation properties that cannot currently be accounted for directly.

We propose a practical modification to Miner's rule for solder failure to circumvent this problem. Testing of individual solder pads, eliminating effects of the solder properties, still showed variations in cycling amplitude to systematically reduce subsequent acceleration factors for solder pad cratering. General trends, anticipated consequences and remaining research needs are discussed...

Publisher: Universal Instruments Corporation

5 Questions to Ask Before Choosing a New Cut and Strip Machine

Oct 27, 2014 | Pete Doyon, VP Product Management, Schleuniger, Inc.

A lot of time and effort often goes into finding the right equipment for your facility. Purchasing a new wire cut & strip machine is no different. With so many options, where does one start? Asking these five questions during the decision making process will help ensure you end up with equipment that fits all of your needs. ...

Publisher: Schleuniger, Inc.

Combination of Spray and Soak Improves Cleaning under Bottom Terminations

Oct 23, 2014 | Dr. Mike Bixenman; Kyzen Corporation, Julie Fields; Technical Devices Company, Eric Camden; Foresite.

The functional reliability of electronic circuits determines the overall reliability of the product in which the final products are used. Market forces including more functionality in smaller components, no-clean lead-free solder technologies, competitive forces and automated assembly create process challenges. Cleanliness under the bottom terminations must be maintained in harsh environments. Residues under components can attract moisture and lead to leakage currents and the potential for electrochemical migration (...)

The purpose of this research study is to evaluate innovative spray and soak methods for removing low residue flux residues and thoroughly rinsing under Bottom Termination and Leadless Components...

Publisher: KYZEN Corporation

Oxide Thickness and Solderability Methodology to Determine Long Term Storage of BGAs and QFPs

Oct 16, 2014 | Rama Hegde, senior member of technical staff; Freescale Semiconductor.

Key points are:

*Long-term storage of BGA & QFP products may be required due to:

• Fab and assembly factory transfers
• Product obsolescence requiring customers make lifetime/EOL purchases
• Providing extended service (10+ years) on vehicles
• Other program needs

* Integrity of EOL products in terms of solderability needs to be verified....

Publisher: Freescale Semiconductor Inc

Cleaning Of Assembled PCBs - A Crucial Way of Enhancing Product Reliability and Avoiding Problems in the Field

Oct 09, 2014 | Wilfried Clemens.

Over the last years more and more international newspapers reported in Europe / USA and Japan: "Tunnel train got stuck under the Channel – thousands of people stranded", "Recall of thousands of cars to workshops for control and repair", "Power Failures left households without energy for hours." Very often news like this relate to malfunctions of electric and electronic circuits under adverse conditions or sometimes even in normal operating environment (...)

The presentation will deal with all kinds of aspect of cleaning to ensure the reliability of electronic circuitry in ever changing operation conditions in the most important industrial areas....

Publisher: Kolb Cleaning Technology USA LLC

Assembly Process Feasibility of Low/No Silver Alloy Solder Paste Materials

Oct 02, 2014 | Jennifer Nguyen Ranilo Aranda, David Geiger, and Murad Kurwa

Sn3.0Ag0.5Cu (SAC305) is the most popular near eutectic lead-free alloy used in the manufacturing processes. Over the last several years, the price of silver has dramatically increased driving a desire for lower silver alloy alternatives. As the results, there is a significant increase in the number of alternative low/no silver lead-free solder alloys available in the industry recently.

In this paper, we'll present the performance and process capability of various low/no silver alloy solder pastes. Data from printability, wetting test, slump test, solder ball test, voiding, etc… will be discussed and compared with the control SAC305 solder paste. Benefits and concerns of using low/no silver alloy solder paste materials will also be addressed....

Publisher: Flex (Flextronics International)

Taking the LED Pick and Place Challenge

Sep 25, 2014 | Joshua J. Markle.

For the past few years there has been a shift in the Lighting Industry that has carried over to the surface mount technology assembly line. What is this shift you may ask? Well it is the LED revolution. This revolution or change in lighting has some very promising results already in practice and many more companies looking to implement the LED technology into their product portfolio's. With a number of companies looking to expand their portfolio to include LED fixtures there has been an increase in the number of companies that have started their own SMT lines, as well as a significant number of contract manufacturers to meet this new industries demands (...)

This presentation will discuss some issues in the pick and place process for LEDs and presents a method to troubleshoot and resolve these issues....

Publisher: Cree, Inc.

Predicting the Lifetime of the PCB - From Experiment to Simulation

Sep 18, 2014 | Markus Leitgeb, AT&S Peter Fuchs, PCCL.

Two major drivers in electronic industry are electrical and mechanical miniaturization. Both induce major changes in the material selection as well as in the design. Nevertheless, the mechanical and thermal reliability of a Printed Circuit Board (PCB) has to remain at the same high level or even increase (e.g. multiple lead-free soldering). To achieve these reliability targets, extensive testing has to be done with bare PCB as well as assembled PCB. These tests are time consuming and cost intensive. The PCBs have to be produced, assembled, tested and finally a detailed failure analysis is required to be performed.

This paper examines the development of our concept and has the potential to enable the prediction of the lifetime of the PCB using accelerated testing methods and finite element simulations....

Publisher: AT&S

Plastic vs Metal Stencils for Prototype Printing

Sep 11, 2014 | Bob Wettermann.

This article goes through the pluses and minuses of using plastic stencils for DIY prototypes. The release efficiency is measured and "rules of thumb" for using one type vs another is explained....

Publisher: BEST Inc.

Reliability of Reworked QFNs

Sep 11, 2014 | CRANE.

In this DOD study the reliability of reworked QFNs is studied with the outcome being that a stay in place stencil does not impact the reliability of a QFN reworked using this technique...

Publisher: BEST Inc.

Reballing a QFN Simplifies QFN Rework

Sep 11, 2014 | Bob Wettermann.

There are a variety of methods one can use to rework QFNs. This paper explains one of the ways to get very little center ground voiding while making it easy to place a tiny component with almost no keep out areas....

Publisher: BEST Inc.

Counterfeit Integrated Circuits: Detection, Avoidance, and the Challenges Ahead.

Sep 04, 2014 | U. Guin, M. Tehranipoor - ECE Department, University of Connecticut, D. DiMase - Honeywell Inc.,

The counterfeiting of electronic components has become a major challenge in the 21st century. The electronic component supply chain has been greatly affected by widespread counterfeit incidents. A specialized service of testing, detection, and avoidance must be created to tackle the worldwide outbreak of counterfeit integrated circuits (ICs). So far, there are standards and programs in place for outlining the testing, documenting, and reporting procedures. However, there is not yet enough research addressing the detection and avoidance of such counterfeit parts.

In this paper we will present, in detail, all types of counterfeits, the defects present in them, and their detection methods. We will then describe the challenges to implementing these test methods and to their effectiveness. We will present several anti-counterfeit measures to prevent this widespread counterfeiting, and we also consider the effectiveness and limitations of these anti-counterfeiting techniques....

Publisher: Honeywell International

The Effect of Coating and Potting on the Reliability of QFN Devices.

Aug 28, 2014 | Greg Caswell, Cheryl Tulkoff.

The fastest growing package types in the electronics industry today are Bottom Termination Components (BTCs). While the advantages of BTCs are well documented, they pose significant reliability challenges to users. One of the most common drivers for reliability failures is the inappropriate adoption of new technologies. This is especially true for new component packaging like BTCs. Obtaining relevant information can be difficult since information is often segmented and the focus is on design opportunities not on reliability risks (...)

Commonly used conformal coating and potting processes have resulted in shortened fatigue life under thermal cycling conditions. Why do conformal coating and potting reduce fatigue life? This paper details work undertaken to understand the mechanisms underlying this reduction. Verification and determination of mechanical properties of some common materials are performed and highlighted. Recommendations for material selection and housing design are also given....

Publisher: DfR Solutions

Implementing Warpage Management: A Five-Step Process for EMS Providers

Aug 19, 2014 | Ken Chiavone

Warpage management consists of planning, measuring, analyzing, sharing, and reacting to data related to the surface shapes of electronics components as they change throughout the reflow assembly process. Leading semiconductor manufacturers have had warpage management systems in place for ten years or more, mainly because microchip package warpage must be understood and compensated for in order to attain high assembly yields. Similarly, newer device architectures such as package-on-package and system-on-a-chip are sensitive to warpage-related assembly issues, and companies involved in the manufacture and assembly of these devices tend to have the most advanced warpage management programs....

Publisher: Akrometrix

Advanced Second Level Assembly Analysis Techniques - Troubleshooting Head-In-Pillow, Opens, and Shorts with Dual Full-Field 3D Surface Warpage Data Sets/

Aug 19, 2014 | Ken Chiavone

SMT assembly planning and failure analysis of surface mount assembly defects often include component warpage evaluation. Coplanarity values of Integrated Circuit packages have traditionally been used to establish pass/fail limits. As surface mount components become smaller, with denser interconnect arrays, and processes such package-on-package assembly become prevalent, advanced methods using dual surface full-field data become critical for effective Assembly Planning, Quality Assurance, and Failure Analysis. A more complete approach than just measuring the coplanarity of the package is needed. Analyzing the gap between two surfaces that are constantly changing during the reflow thermal cycle is required, to effectively address the challenges of modern SMT assembly....

Publisher: Akrometrix

Ready to Start Measuring PCB Warpage during Reflow? Why and How to Use the New IPC-9641 Standard

Aug 19, 2014 | Ken Chiavone

Understanding warpage of package attach locations on PCBs under reflow temperature conditions is critical in surface mount technology. A new industry standard, IPC 9641, addresses this topic directly for the first time as an international standard.

This paper begins by summarizing the sections of the IPC 9641 standard, including, measurement equipment selection, test setup and methodology, and accuracy verification. The paper goes further to discuss practical implementation of the IPC 9641 standards. Key advantages and disadvantages between available warpage measurement methods are highlighted. Choosing the correct measurement technique depends on requirements for warpage resolution, data density, measurement volume, and data correlation. From industry experience, best practice recommendations are made on warpage management of PCB land areas, covering how to setup, run, analyze, and report on local area PCB warpage.

The release of IPC 9641 shows that flatness over temperature of the package land area on the PCB is critical to the SMT industry. Furthermore, compatibility of shapes between attaching surfaces in SMT, like a package and PCB, will be critical to product yield and quality in years to come....

Publisher: Akrometrix

Advanced Organic Substrate Technologies To Enable Extreme Electronics Miniaturization.

Aug 14, 2014 | Susan Bagen, Dave Alcoe, Kim Blackwell, Frank Egitto.

High reliability applications for high performance computing, military, medical and industrial applications are driving electronics packaging advancements toward increased functionality with decreasing degrees of size, weight and power (SWaP) The substrate technology selected for the electronics package is a key enabling technology towards achieving SWaP. Standard printed circuit boards (PWBs) utilize dielectric materials containing glass cloth, which can limit circuit density and performance, as well as inhibit the ability to achieve reliable assemblies with bare semiconductor die components. Ceramic substrates often used in lieu of PWBs for chip packaging have disadvantages of weight, marginal electrical performance and reliability as compared to organic technologies. Alternative materials including thin, particle-containing organic substrates, liquid crystal polymer (LCP) and microflex enable SWaP, while overcoming the limitations of PWBs and ceramic.

This paper will discuss the use of these alternative organic substrate materials to achieve extreme electronics miniaturization with outstanding electrical performance and high reliability. The effect of substrate type on chip-package interaction and resulting reliability will be discussed. Microflex assemblies to achieve extreme miniaturization and atypical form factors driven by implantable and in vivo medical applications are also shown....

Publisher: i3 Electronics

Gold Embrittlement In Lead-Free Solder.

Aug 07, 2014 | Craig Hillman, Nathan Blattau, Joelle Arnold, Thomas Johnston, Stephanie Gulbrandsen; DfR Solutions, Julie Silk, Alex Chiu; Agilent Technologies.

Gold embrittlement in SnPb solder is a well-known failure mechanism in electronic assembly. To avoid this issue, prior studies have indicated a maximum gold content of three weight percent. This study attempts to provide similar guidance for Pb-free (SAC305) solder. Standard surface mount devices were assembled with SnPb and SAC305 solder onto printed boards with various thicknesses of gold plating. The gold plating included electroless nickel immersion gold (ENIG) and electrolytic gold of 15, 25, 35, and 50 microinches over nickel. These gold thicknesses resulted in weight percentages between 0.4 to 7.0 weight percent....

Publisher: DfR Solutions

Electrostatic Theory of Metal Whiskers.

Jul 31, 2014 | V. G. Karpov, Department of Physics and Astronomy, University of Toledo.

Metal whiskers often grow across leads of electric equipment and electronic package causing current leakage or short circuits and raising significant reliability issues. The nature of metal whiskers remains a mystery after several decades of research. Here, the existence of metal whiskers is attributed to the energy gain due to electrostatic polarization of metal filaments in the electric field. The field is induced by surface imperfections: contaminations, oxide states, grain boundaries, etc. A proposed theory provides closed form expressions and quantitative estimates for the whisker nucleation and growth rates, explains the range of whisker parameters and effects of external biasing, and predicts statistical distribution of their lengths....

Publisher: University of Toledo

Copper Wire Bond Failure Mechanisms.

Jul 24, 2014 | Randy Schueller, Ph.D.

Wire bonding a die to a package has traditionally been performed using either aluminum or gold wire. Gold wire provides the ability to use a ball and stitch process. This technique provides more control over loop height and bond placement. The drawback has been the increasing cost of the gold wire. Lower cost Al wire has been used for wedge-wedge bonds but these are not as versatile for complex package assembly. The use of copper wire for ball-stitch bonding has been proposed and recently implemented in high volume to solve the cost issues with gold. As one would expect, bonding with copper is not as forgiving as with gold mainly due to oxide growth and hardness differences.

This paper will examine the common failure mechanisms that one might experience when implementing this new technology....

Publisher: DfR Solutions

Enhancing Thermal Performance in Embedded Computing for Ruggedized Military and Avionics Applications.

Jul 17, 2014 | Darren Campo, Jens Weyant, Bryan Muzyka

Embedded computing systems used in many military and avionics applications are trending toward higher heat fluxes, and as a result performance is being hindered by thermal limitations. This is intensified by the high ambient conditions experience by today’s modern warfighter. In many applications liquid cooling is replacing air flow through chassis for both thermal and environmental benefits(...)

This paper outlines a series of passive thermal improvements which are easily integrated into legacy, or existing, systems and can provide a 3-4x increase in dissipated power....

Publisher: Advanced Cooling Technologies

Fatigue Damage Behavior of a Surface-mount Electronic Package Under Different Cyclic Applied Loads.

Jul 10, 2014 | Ren Huai-Hui, Wang Xi-Shu

This paper studies and compares the effects of pull–pull and 3-point bending cyclic loadings on the mechanical fatigue damage behaviors of a solder joint in a surface-mount electronic package.

The comparisons are based on experimental investigations using scanning electron microscopy (SEM) in-situ technology and nonlinear finite element modeling, respectively. The compared results indicate that there are different threshold levels of plastic strain for the initial damage of solder joints under two cyclic applied loads; meanwhile, fatigue crack initiation occurs at different locations, and the accumulation of equivalent plastic strain determines the trend and direction of fatigue crack propagation. In addition, simulation results of the fatigue damage process of solder joints considering a constitutive model of damage initiation criteria for ductile materials and damage evolution based on accumulating inelastic hysteresis energy are identical to the experimental results. The actual fatigue life of the solder joint is almost the same and demonstrates that the FE modeling used in this study can provide an accurate prediction of solder joint fatigue failure....

Publisher: Tsinghua University

Effect of Cu–Sn intermetallic Compound Reactions on the Kirkendall Void Growth Characteristics in Cu/Sn/Cu Microbumps

Jul 02, 2014 | Jong-Myeong Park, Seung-Hyun Kim, Young-Bae Park - Andong National University, Myeong-Hyeok Jeong - NEPES Corporation.

Growth behaviors of intermetallic compounds (IMCs) and Kirkendall voids in Cu/Sn/Cu microbump were systematically investigated by an in-situ scanning electron microscope observation. Cu–Sn IMC total thickness increased linearly with the square root of the annealing time for 600 h at 150°C, which could be separated as first and second IMC growth steps. Our results showed that the growth behavior of the first void matched the growth behavior of second Cu6Sn5, and that the growth behavior of the second void matched that of the second Cu3Sn. It could be confirmed that double-layer Kirkendall voids growth kinetics were closely related to the Cu–Sn IMC growth mechanism in the Cu/Sn/Cu microbump, which could seriously deteriorate the mechanical and electrical reliabilities of the fine-pitch microbump systems...

Publisher: Nepes Corporation

Enhancing Mechanical Shock Performance Using Edgebond Technology

Jun 26, 2014 | Steven Perng, Tae-Kyu Lee, and Cherif Guirguis - Cisco Systems, Inc., Edward S. Ibe - Zymet, Inc.

Edgebond adhesives have been widely used by the industry for improving the shock performance of area array packages. Most of the studies focus on the impact of material properties, such as coefficient of thermal expansion (CTE) and glass transition temperature (Tg), on reliability at room temperature. However, the operating temperature of a component on the printed circuit board bonded with edgebond adhesive can be close to or exceed Tg of the adhesive, where the material properties may be very different than at room temperature....

Publisher: Cisco Systems, Inc.

OOOH Colors, It Must Be Lead Free

Jun 23, 2014 | John Maxwell, Director of Product Development, Johanson Dielectrics Inc.

It was unusual to see chip terminations change colors when tin lead solders were used but with the introduction of lead free reflow soldering and the corresponding increases in reflow temperatures terminations are now changing colors. Two conditions are present when reflow temperatures are increased for lead free solder alloys that leads to discoloration. Reflow temperatures are above the melting point of tin (Sn MP is 232oC). Air temperatures commonly used in forced convection reflow systems are high enough to both melt the tin plating on the termination allowing it to be pulled into the solder joint due to solder joint liquid solder surface tension leaving behind the exposed nickel barrier. Now those metal oxide colors will be visible due to high air temperatures during reflow....

Publisher: Johanson Dielectrics, Inc.

Anisotropic grain growth and crack propagation in eutectic microstructure under cyclic temperature annealing in flip-chip SnPb composite solder joints

Jun 19, 2014 | Y.C. Liang, H.W. Lin, H.P. Chen, C. Chen, K.N. Tub, Y.S.Lai

For high-density electronic packaging,the application of flip-chip solder joints has been well received in the microelectronics industry. High-lead(Pb) solders such as Sn5Pb95 are presently granted immunity from the RoHS requirements for their use in high-end flip-chip devices, especially in military applications. In flip-chip technology for consumer electronic products, organic substrates have replaced ceramic substrates due to the demand for less weight and low cost. However, the liquidus temperatures of high-Pb solders are over 300°C which would damage organic substrates during reflow because of the low glass transition temperature. To overcome this difficulty, the composite solder approach was developed......

Publisher: National Chiao Tung University

Instrumentation for Studying Real-time Popcorn Effect in Surface Mount Packages during Solder Reflow

Jun 12, 2014 | Arijit Roy

Occurrence of popcorn in IC packages while assembling them onto the PCB is a well known moisture sensitive reliability issues, especially for surface mount packages. Commonly reflow soldering simulation process is conducted to assess the impact of assembling IC package onto PCB. A strain gauge-based instrumentation is developed to investigate the popcorn effect in surface mount packages during reflow soldering process. The instrument is capable of providing real-time quantitative information of the occurrence popcorn phenomenon in IC packages. It is found that the popcorn occur temperatures between 218 to 241°C depending on moisture soak condition, but not at the peak temperature of the reflow process. The presence of popcorn and delamination are further confirmed by scanning acoustic tomography as a failure analysis....

Publisher: WASET - World Academy of Science, Engineering and Technology

Stencil Printing Yield Improvements

Jun 05, 2014 | Dr. Mike Bixenman, Debbie Carboni, Jason Chan

Stencil printing capability is becoming more important as the range of component sizes assembled on a single board increases. Coupled with increased component density, solder paste sticking to the aperture sidewalls and bottom of the stencil can cause insufficient solder paste deposits and solder bridging. Yield improvement requires increased focus on stencil technology, printer capability, solder paste functionality and understencil cleaning.

(...) The purpose of this research is to study the wipe sequence, wipe frequency and wipe solvent(s) and how these factors interact to provide solder paste printing yield improvement....

Publisher: KYZEN Corporation

Solder Joint Encapsulant Adhesive Pop TMV High Reliability And Low Cost Assembly Solution

Jun 02, 2014 | Dr. Mary Liu and Dr. Wusheng Yin

With the advancement of the electronic industry, package on package (POP) has become increasingly popular IC package for electronic devices, particularly POP TMV (Through Mold Vials) in mobile devices due to its benefits of miniaturization, design flexibility and cost efficiency. However, there are some issues that have been reported such as SIR drop due to small gap between top and bottom components, difficulty underfilling and rework due to stacked IC components and process yield issues. Some suppliers have reported using some methods such as dipping epoxy paste or epoxy flux to address these issues, but so far no customer has reported using these methods or materials in their mass production. In order to address these issues for POP TMV assembly, YINCAE has successfully developed and commercialized the first individual solder joint encapsulant adhesive for mass production for years....

Publisher: YINCAE Advanced Materials, LLC.

Microspring Characterization and Flip-Chip Assembly Reliability

May 29, 2014 | B. Cheng, D. De Bruyker, C. Chua, K. Sahasrabuddhe, I. Shubin, J. E. Cunningham, Y. Luo, K. F. Böhringer, A. V. Krishnamoorthy, E, M. Chow

Electronics packaging based on stress-engineered spring interconnects has the potential to enable integrated IC testing, fine pitch, and compliance not readily available with other technologies. We describe new spring contacts which simultaneously achieve low resistance (< 100 mΩ) and high compliance (> 30 μm) in dense 2-D arrays (180 ~ 180-µm pitch). Mechanical characterization shows that individual springs operate at approximately 150-µN force. Electrical measurements and simulations imply that the interface contact resistance contribution to a single contact resistance is < 40 mΩ. A daisy-chain test die consisting of 2844 contacts is assembled into flip-chip packages with 100% yield. Thermocycle and humidity testing suggest that packages with or without underfill can have stable resistance values and no glitches through over 1000 thermocycles or 6000 h of humidity.

This paper suggests that integrated testing and packaging can be performed with the springs, enabling new capabilities for markets such as multichip modules....

Publisher: Institute of Electrical and Electronics Engineers (IEEE)

Pb-free solders: Comparison of different geometrical models in calculating of enthalpy of mixing of In-Sn-Zn ternary system.

May 22, 2014 | A. Boulouiz, M. El Moudane, M. Mekkaoui, A. Sabbar

In this paper, the general solution model of Chou has been used to predict the integral enthalpies of mixing of liquid In-Sn-Zn ternary alloys in five selected sections, xIn/xSn = 0.15/0.85, 0.34/0.66, 0.50/0.50, 0.67/0.33 and 0.85/0.15. The other traditional models such as Kohler, Muggianu, Toop and Hillert are also included in calculations. Comparison with literature data was done and showed reasonable agreement with Toop and Hillert asymmetric models....

Publisher: Université Mohammed V-Agdal

Performance of Light Emitting Diode on Surface Machined Heat Sink

May 15, 2014 | S. Shanmugan*, D. Mutharasu, O. Zeng Yin

In the point of efficient heat removal from light emitting diode (LED) package to ambient, the surface of the heat sinks must be finished based on required condition. The surface finishing plays an important role in efficient heat dissipation. In our work, the top surface of heat sink was machined like two different shapes (slotted and 'W' shaped) and tested the thermal performance for 3W green LED. The total thermal resistance was high for 'W' shaped surface at 100 mA. Surface modification was not influenced much on the thermal resistance (Rth) value at higher operating current. Noticeable increase on junction temperature was observed for 'W' shaped surface at 100 mA than slotted surface. In optical properties, low lux values were recorded for ‘W’ shaped surface at all operating current. In addition, 'W' shaped surface showed low value in CRI than other two surfaces (plain and slotted). The observed CCT value was decreased as the measuring time increased. High value in CCT was observed for ‘W’ shaped surface at higher operating current (> 350mA). Slotted surface showed good performance on both thermal and optical properties of the given 3W green LED....

Publisher: Universiti Sains Malaysia

Lead-Free Soldering Guide

May 12, 2014 | AIM

The issue of lead-free soldering has piqued a great deal of interest in the electronics assembly industry as of late. What was once an issue that seemed too far away to worry about has become a pressing reality. In order to avoid confusion, last minute panic, and a misunderstanding of how the issue of lead-free soldering will affect the industry and individuals users of solders, it is necessary for all suppliers and assemblers to become educated in this matter....

Publisher: AIM Solder

Solder Joint Encapsulant Adhesive POP Assembly Solution

May 12, 2014 | Dr. Mary Liu and Dr. Wusheng Yin

With the advancement of the electronic industry, Package on package (POP) has become increasingly popular IC package for electronic devices, particularly in mobile devices due to its benefits of miniaturization, design flexibility and cost efficiency. However, there are some issues that have been reported such as SIR drop due to small gap between top and bottom components, difficulty underfilling and rework due to stacked IC components and process yield issues. Some suppliers have reported using some methods such as dipping epoxy paste or epoxy flux to address these issues, but so far, no customer has reported using these methods or materials in their mass production. In order to address these issues for POP assembly, YINCAE has successfully developed a first individual solder joint encapsulant adhesive....

Publisher: YINCAE Advanced Materials, LLC.

Challenges in Bare Die Mounting

May 08, 2014 | Larry Gilg, Die Products Consortium.

Bare die mounting on multi-device substrates has been in use in the microelectronics industry since the 1960s. The aerospace industry’s hybrid modules and IBM’s Solid Logic Technology were early implementations that were developed in the 1960’s. The technologies progressed on a steady level until the mid 1990’s when, with the advent of BGA packaging and chip scale packages, the microelectronics industry started a wholesale move to area array packaging. This paper outlines the challenges for both traditional wire-bond die attached to a printed wiring board (pwb), to the more recent applications of bumped die attached to a high performance substrate....

Publisher: Die Products Consortium

Strain Solitons and Topological Defects in Bilayer Graphene

May 01, 2014 | Jonathan S. Aldena, Adam W. Tsena, Pinshane Y. Huanga, Robert Hovdena, Lola Brownb, Jiwoong Parkb,c, David A. Mullera,c, and Paul L. McEuen.

Bilayer graphene has been a subject of intense study in recent years. The interlayer registry between the layers can have dramatic effects on the electronic properties: for example, in the presence of a perpendicular electric field, a band gap appears in the electronic spectrum of so-called Bernal-stacked graphene. This band gap is intimately tied to a structural spontaneous symmetry breaking in bilayer graphene, where one of the graphene layers shifts by an atomic spacing with respect to the other. This shift can happen in multiple directions, resulting in multiple stacking domains with soliton-like structural boundaries between them...

Publisher: Cornell University