Printed Wiring Board Assemblies Research Articles

Comparison of Warpage Measurement Capabilities and Results Obtained by Using Laser and Digital Fringe Projection Methods

Electronic packaged devices are becoming increasingly smaller in size and higher in density while requiring higher performance and superior reliability. Warpage is one of the crucial factors for the thermomechanical reliability of electronic packages and warpage control becomes a more crucial process during the printed wiring board (PWB) fabrication and package assembly processes. This requirement necessitates more accurate methods of measuring warpage. The fringe projection methods are recent trends for measuring the warpage of chip packages, PWBs, and PWB assemblies (PWBAs) because of their noncontact, full-field, and high-resolution measurement capabilities. This paper presents a comparison of two fringe projection methods: laser fringe projection (LFP) (projection moiré) and digital fringe projection (DFP). Experimental results show that digital fringe projection has higher practical resolution, and better accuracy and precision than laser fringe projection.

Techniques for Measuring Warpage of Chip Packages, PWBs, and PWB Assemblies

One of the crucial factors for the thermo-mechanical reliability of electronic packages is warpage that occurs during the printed wiring board (PWB) fabrication, solder masking and solder reflow processes. As the quality and reliability requirements of electronic components (packages) become higher, warpage control becomes a more crucial process during the PWB fabrication (manufacturing) and package assembly processes. The warpage of PWBs, PWB assemblies and electronic packages are measured by various techniques. Each technique has both its advantages and disadvantages; therefore the choice of a particular technique depends on whether one wants to measure the warpage of a PWB, PWB assembly or chip package. This paper reviews the pros and cons, such as resolution, speed, costs, accuracy, in-line capability, flexibility, and robustness, of different techniques used for measuring the warpage of chip packages, PWBs and PWB assemblies.

Advanced Microelectronics Packaging Solutions for Miniaturized Medical Devices

The wide range of applications for medical electronics drives unique requirements that can differ significantly from commercial & military electronics. To accomplish this, new packaging structures need to be able to integrate more dies with greater function, higher I/O counts, smaller die pad pitches, and high reliability, while being pushed into smaller and smaller footprints. As a result, the microelectronics industry is moving toward alternative, innovative approaches as solutions for squeezing more function into smaller packages. In the present report, key enablers for achieving reduction in size, weight, and power (SWaP) in electronic packaging for a variety of medical applications are discussed. Advanced microelectronics packaging solutions with embedded passives are enabling SWaP reductions. Implementation of these solutions has realized up to 27X reduction in physical size for existing PWB assemblies, with significant reductions in weight. Shorter interconnects can also reduce or eliminate the need for termination resistors for some net topologies. Successful miniaturized products integrate the following design techniques and technologies: component footprint reduction, thin high density interconnects substrate technologies, I/O miniaturization and IC assembly capabilities. This paper presents fabrication and electrical characterization of embedded actives and passives on organic multilayered substrates. We have designed and fabricated several printed wiring board (PWB) and flip-chip package test vehicles focusing on embedded chips, resistors, and capacitors. Embedded passive technology further enhances miniaturization by enabling components to be moved from the surface of the substrate to its internal layers. The use of thin film resistor material allows creating individual miniaturized buried resistors. These resistors provide additional length and width reduction with negligible increases to the overall substrate and module (SiP) height. Resistor values can vary from 5 ohm to 50 Kohm with tolerances from 5 to 20% and areas as small as 0.2 mm2. The embedded resistors can be laser trimmed to a tolerance of <5% for applications that require tighter tolerance. The electrical properties of embedded capacitors fabricated from polymer-ceramic nanocomposites showed a stable capacitance and low loss over a wide frequency and temperature range. A few test vehicles were assembled to do system level analysis. Manufacturing methods and materials for producing advanced organic substrates and flex along with ultra fine pitch assemblies are discussed. A case study detailing the fabrication of a flexible substrate for use in an intravascular ultrasound (IVUS) catheter demonstrates how the challenges of miniaturization are met. These challenges include use of ultra-thin polymer films, extreme fine-feature circuitization, and assembly processes to accommodate die having reduced die pad pitch. In addition, new technologies for embedding a variety of active chips are being developed. A variety of active chips, including a chip having dimensions of one millimeter square, have been embedded and electrically connected to develop high performance packages.

Heavy metal partitioning from electronic scrap during thermal End-of-Life treatment

Samples of identical Printed Wiring Board Assemblies (PWBA) have been thermally treated in a Quartz Tube Reactor (QTR) in order to detect the volatility of selected heavy metals contained in electronic scrap being of environmental concern. In preparation, evaporation experiments were performed using a Thermo Gravimeter (TG) in connection with an Inductively Coupled Plasma-Optical Emissions Spectrometer (ICP-OES). The QTR experiments were performed under reducing and under oxidising conditions at 550 and at 880 degrees C. The volatilisation has been determined for As, Cd, Ni, Ga, Pb, and Sb using ICP-OES analysis of the ash residues. The results were evaluated by thermodynamic equilibrium calculations, the TG-ICP measurements and in comparison with similar studies. In coincidence with the preparative TG-ICP measurements as well as with thermodynamic equilibrium calculations neither As nor Cd could be detected in the residuals of the thermally treated PWBA samples, suggesting a high volatility of these metals. Ga does not show a distinct volatilisation mechanism and seems to be incorporated in the siliceous fraction. Ni remains as stable compound in the bottom ash. Sb shows a high volatility nearly independent of temperature and oxygen supply. The results imply that, if electronic scrap is thermally processed, attention has to be paid in particular to Sb, As, and Ga. These metals are increasingly used in new electronic equipment such as mobile phone network equipment of the third generation.

Life cycle assessment in the telecommunication industry: A review

Background, Goal and ScopeToday, after the technologically and commercially successful breakthrough of electronic telecommunication facilities, rapid and globally untrammelled information exchange has become an indispensable service in daily life. Associated with the tremendous growth in electronic telecommunication hardware (GSMAssociation 2005), however, was and continues to be an increasing awareness of the environmental effects related to both the operation and the production, as well as the End-of-Life (EoL) treatment of such communication equipment. Environmental concerns, for example, have resulted in various governmental regulations such as the WEEE- (CEC 2003b) and the RoHS-directives (CEC 2003a).To analyse, interpret and improve the environmental performance of electronic telecommunication equipment, life cycle assessment (LCA) is increasingly recognised as one promising analytical tool. Based on a thorough review of the scientific work and by discussing industrial views, this paper is intended to determine the key milestones achieved, to analyse the current research situation and to outline the key challenges concerning LCA and electronic telecommunication industries.MethodStarting with a brief reflection of the LCA approach, the particularities in context with telecommunication products1 are discussed. Exemplary for various stakeholders participating in the supply chain of telecommunication means recent industry perspectives are also presented.ResultsIn the core section of the proposed paper, the pertinent scientific literature on LCA and electronic telecommunication means is reviewed and the most impressive achievements are documented. Particular attention is dedicated to subcomponents of individual electronic telecommunication devices (e.g. Printed Wiring Board Assemblies (PWBA) of mobile phones), components of mobile communication networks (e.g. Base Transceiver Stations (BTS)) and entire networks concentrating on product comparisons, inventory approaches, impact assessment method development, result interpretations and presentation, and usability of LCA in decision-making.DiscussionFrom the reviewed scientific literature and industry views, it was found that telecommunication products, in general, represent complex objects requiring a well thought-out performance of the LCA tool. It has been shown that today there is a lack of stakeholder involvement resulting in LCA studies which only partly fulfil the expectations of the contractors. In this spirit it was recognised, at present, that most of the LCA studies on telecommunication equipment result in bulky and stakeholder unspecific compilations of findings impossible to be used in rapid decision-making. This aspect may explain why LCA so far is not or only partly integrated into decision-making of globally integrated industries, such as in telecommunication industries.ConclusionsIn summary, it can be stated that LCA represents a promising alternative to analyse, to interpret and essentially to adjust the environmental performance of electronic telecommunication products. The review showed that there is a need to focus research efforts in order to arrive at sound improvements of the LCA methodology.PerspectivesThe conclusions from the presented review suggest concentrating in particular on further development of the LCA methodology with respect to efficiency, effectivity and flexibility. This challenge is associated with the need for LCA to be understood as a process rather than a discontinuously applicable tool, attending industrial processes, in essence to contribute to improved environmental performances of products. In this context, particular attention should be paid to proper stakeholder involvement and continuous exchange of concentrated information relevant for the respective stakeholder.

Life cycle assessment in the telecommunication industry: A review

Today, after the technologically and commercially successful breakthrough of electronic telecommunication facilities, rapid and globally untrammelled information exchange has become an indispensable service in daily life. Associated with the tremendous growth in electronic telecommunication hardware (GSMAssociation 2005), however, was and continues to be an increasing awareness of the environmental effects related to both the operation and the production, as well as the End-of-Life (EoL) treatment of such communication equipment. Environmental concerns, for example, have resulted in various governmental regulations such as the WEEE- (CEC 2003b) and the RoHS-directives (CEC 2003a). To analyse, interpret and improve the environmental performance of electronic telecommunication equipment, life cycle assessment (LCA) is increasingly recognised as one promising analytical tool. Based on a thorough review of the scientific work and by discussing industrial views, this paper is intended to determine the key milestones achieved, to analyse the current research situation and to outline the key challenges concerning LCA and electronic telecommunication industries. Starting with a brief reflection of the LCA approach, the particularities in context with telecommunication products1 are discussed. Exemplary for various stakeholders participating in the supply chain of telecommunication means recent industry perspectives are also presented. In the core section of the proposed paper, the pertinent scientific literature on LCA and electronic telecommunication means is reviewed and the most impressive achievements are documented. Particular attention is dedicated to subcomponents of individual electronic telecommunication devices (e.g. Printed Wiring Board Assemblies (PWBA) of mobile phones), components of mobile communication networks (e.g. Base Transceiver Stations (BTS)) and entire networks concentrating on product comparisons, inventory approaches, impact assessment method development, result interpretations and presentation, and usability of LCA in decision-making. From the reviewed scientific literature and industry views, it was found that telecommunication products, in general, represent complex objects requiring a well thought-out performance of the LCA tool. It has been shown that today there is a lack of stakeholder involvement resulting in LCA studies which only partly fulfil the expectations of the contractors. In this spirit it was recognised, at present, that most of the LCA studies on telecommunication equipment result in bulky and stakeholder unspecific compilations of findings impossible to be used in rapid decision-making. This aspect may explain why LCA so far is not or only partly integrated into decision-making of globally integrated industries, such as in telecommunication industries. In summary, it can be stated that LCA represents a promising alternative to analyse, to interpret and essentially to adjust the environmental performance of electronic telecommunication products. The review showed that there is a need to focus research efforts in order to arrive at sound improvements of the LCA methodology. The conclusions from the presented review suggest concentrating in particular on further development of the LCA methodology with respect to efficiency, effectivity and flexibility. This challenge is associated with the need for LCA to be understood as a process rather than a discontinuously applicable tool, attending industrial processes, in essence to contribute to improved environmental performances of products. In this context, particular attention should be paid to proper stakeholder involvement and continuous exchange of concentrated information relevant for the respective stakeholder.

Life Cycle Assessment of Mobile Telephone Networks, with Focus on the End-of-Life Phase

Life Cycle Assessment of Mobile Telephone Networks, with Focus on the End-of-Life Phase

Parametric study of warpage in printed wiring board assemblies

Out-of-plane displacement (warpage) causes mis-registration, delamination, possibly solder joint opening(s), and other printed wiring board assembly (PWBA) failures during surface-mount assembly processes and life-span operations. Many material, geometry, and process related parameters contribute to the warpage of a PWBA. The objective of this paper is to investigate these parametric effects on PWBA warpage. Based on the parametric study, the identified material, geometry, and process parameters can then be optimized to achieve the most reliable product. In this paper, a PWBA test vehicle consisting of a four-layer PWB and a surface-mount ball grid array package is studied. Its warpage during infrared reflow is measured by the shadow moire/spl acute/ method to validate finite-element results. The validated modeling results are used for parametric study. In the parametric study, Taguchi and full-factorial design of experiments (DOE) are adopted to systematically vary parameters that are of interest. After running experiments based on DOE, analysis of variance is employed to identify the influential parameters. Thereafter, the warpage data is regressed with respect to the identified influential parameters. According to the regression model, the influential parameters can be optimized within practical range to achieve the least warped design.

System for Real-Time Measurement of Thermally Induced PWB/PWA Warpage

Abstract An automated on-line warpage measurement system for printed wiring board assemblies (PWBAs) has been developed. The system is capable of simulating an infrared reflow soldering process and performing real-time PWBA warpage measurements using the shadow moire´ technique. The system can be used to characterize the warpage behavior of virtually any PWBA during infrared soldering processes as well as during operational conditions. Using this system, warpage of PWB test vehicles was measured during simulated infrared reflow soldering. The measurement results and the measurement system will be presented. The measured warpage varied significantly during reflow soldering from that observed both before and after reflow. These results help us to understand how the board deforms at every stage of the reflow process.

In-process board warpage measurement in a lab scale wave soldering oven

An automated on-line warpage measurement system for printed wiring boards (PWBs) and printed wiring board assemblies (PWBAs) has been developed. The system is capable of simulating a variety of soldering processes, including the wave soldering process, and performing real-time PWB/PWBA warpage measurements using the shadow moire technique. The system can be used to characterize the warpage behavior of virtually any PWB/PWBA during the soldering process. Using this system, warpage of PWB test vehicles was measured during simulated wave soldering. The measured warpage varied significantly during wave soldering from that observed both before and after wave soldering. These results help us to understand how the board deforms at every stage of the soldering process.