Column Grid Research Articles

Solder Immersion Process of Ceramic Column Grid Array Package Assembly for Space Applications

Ceramic column grid array (CCGA) packages are progressively being utilized for logic and microprocessor functionalities requiring very high-density interconnections. These packages offer various advantages, such as high reliability, good thermal and electrical performance, and reduced size and weight, due to which the use of these packages in space applications is becoming more and more popular. Assembly of such packages is always challenging for assembly and quality assurance engineers due to its post assembly inspection and rework limitations. These packages are usually assembled using the standard surface-mount technology (SMT) assembly processes involving solder paste printing on printed circuit boards (PCBs), component placement, and reflow soldering. An innovative tweak to the SMT process named solder immersion process (SImP) for assembly of CCGA is invented, where the solder paste is applied on the columns of the CCGA packages replacing the conventional solder paste printing/dispensing. SImP is useful for prototyping and reworkability and results in substantial improvement of the solder joint quality. This article explains the SImP in detail, test vehicle preparation, quality evaluation and subsequent accelerated thermal cycling test results, its applications, and advantages in the field of prototyping and reworkability.

SOLVING DIAGONAL SUDOKU PUZZLE 9X9 GRID BY JAVA PROGRAMMING ALGORITHM

Sudoku is one of the well-known puzzle game that has been played worldwide. There are many types of Sudoku puzzle that exist to be played such as diagonal, diagonal even, diagonal odd, is sudoku, lucky seven, parquet and others. This paper focuses on solving the diagonal Sudoku by using Java Programming Algorithm for 9x9 grid. For normal Sudoku, the number 1-9 must be filled up in all grids with no number duplication conflict in the row, column and 3x3 grid inside the Sudoku puzzle itself. While the diagonal Sudoku has one extra condition to be considered that is the number 1-9 must also be filled in the diagonal place which starts from the most upper-left or bottom-left to the most upper-right or bottom-right of the puzzle. There is no conflict with other grid in its diagonal region. In order to solve the puzzle, we have to construct an algorithm and translate it using Java Programming Language. The guessing method with backtrack approach has been selected to construct the algorithm. This Java Programming is designed to solve the diagonal Sudoku puzzle for a 9x9 grid.

Microstructure and its subsequent evolution of Sn37Pb/Cu column interconnect obtained by friction plunge welding

To optimize the column planting process of copper column grid array (CuCGA) package, friction plunge welding was proposed to implement the solder/Cu column interconnect assisted without mold. On account of friction and extrusion action during feeding of Cu column, high homologous temperature and large strain, which conformed to the condition of dynamic recrystallization, were generated in the solder zones near interface. The irregular island-like, fragment-like recrystallization α-Pb phases and striped-like α-Pb phases in β-Sn matrix formed at different distances from the interface of Sn37Pb/Cu column, respectively. Meanwhile, a thin, wave-like Sn/Cu diffusion layer formed at the interface. This indicates that micro-join can also be achieved by friction welding method, and the column planting is changed into a solid-state welding from conventional soft soldering. After the subsequent reflow soldering, the diffusion layer transformed into scallop-like, most α-Pb phases in the solder regressed to disk-like, and the pull-out load of joint is not lower than that of traditional column planting method.

Board-level vapor phase soldering (VPS) with different temperature and vacuum conditions

Purpose Vapor phase soldering (VPS), also known as condense soldering, is capable of improving the mechanical reliability of solder joints in electronic packaging structures. The paper aims to discuss this issue. Design/methodology/approach In the present study, VPS is utilized to assemble two typical packaging types (i.e. ceramic column grid array (CCGA) and BGA) for electronic devices with lead-containing and lead-free solders. By applying the peak soldering temperatures of 215°C and 235°C with and without vacuum condition, the void formation and intermetallic compound (IMC) thickness are compared for different packaging structures with lead-containing and lead-free solder alloys. Findings It is found that at the soldering temperature of 215°C, CCGA under a vacuum condition has fewer voids but BGA without vacuum environment has fewer voids despite of the existence of lead in solder alloy. In light of contradictory phenomenon about void formation at 215°C, a similar CCGA device is soldered via VPS at the temperature of 235°C. Compared with the size of voids formed at 215°C, no obvious void is found for CCGA with vacuum at the soldering temperature of 235°C. No matter what soldering temperature and vacuum condition are applied, the IMC thickness of CCGA and BGA can satisfy the requirement of 1.0–3.0 µm. Therefore, it can be concluded that the soldering temperature of 235°C in vacuum is the optimal VPS condition for void elimination. In addition, shear tests at the rate of 10 mm/min are performed to examine the load resistance and potential failure mode. In terms of failure mode observed in shear tests, interfacial shear failure occurs between PCB and bulk solder and also within bulk solder for CCGA soldered at temperatures of 215°C and 235°C. This means that an acceptable thicker IMC thickness between CCGA solder and device provides greater interfacial strength between CCGA and device. Originality/value Due to its high I/O capacity and satisfactory reliability in electrical and thermal performance, CCGA electronic devices have been widely adopted in the military and aerospace fields. In the present study, the authors utilized VPS to assemble a typical type of CCGA with the control package of conventional BGA to investigate the relation between essential condition (i.e. soldering temperature and vacuum) to void formation.

Experimental research of punching shear mechanism of reinforcing concrete slab

The analysis of various regulatory methods for calculating reinforced concrete slabs for pushing and comparing with experiment results is made. The tested sample, measuring equipment and test bench are described. Sizes and materials for experimental prototype were chosen by existing beamless and capless slabs of monolithic reinforced concrete superstructures with column grid from 8×8 to 9×9 m. Experimental research results of reinforcing concrete plate structure are presented for study purpose of stress-strain state when punching shear collapse occurring. Various aspects and observations obtained during the test are given. The comparison of the tested slab fragment with the complete response of slab structure is performed. Analysis of tested sample stress-strain state and punching bearing capacity calculations results in according to existing regular standards were made. Main criterias of punching shear collapse were determined and new procedure for punching calculation of RC concrete slabs was offered basing on significantly new approach in punching bearing capacity defining.

Elevated Standoff Heights of Solder Joint Interconnections Can Result in Appreciable Stress and Warpage Relief

Abstract The “head-in-pillow” (HnP) defects in lead-free solder joint interconnections of Integrated Circuit (IC) packages with conventional (small) standoff heights of the solder joints, and particularly in packages with fine pitches, are attributed by many electronic material scientists to the three major causes: attributes of the manufacturing process, solder material properties, and design-related issues. The latter are thought to be caused primarily by elevated stresses in the solder material, as well as by the excessive warpage of the Printed Circuit Board (PCB)-package assembly and particularly by the differences in the thermally induced curvatures of the PCB and the package. In this analysis, the stress and warpage issue is addressed using an analytical predictive stress model. The model is a modification and an extension of the model developed back in 1980s by the first author. It is assumed that it is the difference in the postfabrication deflections of the PCB-package assembly that is the root cause of the solder material failures and particularly and perhaps the HnP defects. The calculated data based on the developed stress model suggest that the replacement of the conventional ball grid array (BGA) designs with designs with elevated standoff heights of the solder joints could result in significant stress and warpage relief and, hopefully, in a lower propensity of the IC package to HnP defects as well. The general concepts are illustrated by a numerical example, in which the responses to the change in temperature of a conventional design, referred to as BGA, and a design with solder joints with elevated standoff heights, referred to as column grid array (CGA), are compared. The computed data indicated that the effective stress in the solder material was relieved by about 40% and the difference between the maximum deflections of the PCB and the package was reduced by about 60%, when the BGA design was replaced by a CGA system. Although no definite proof that the use of solder joints with elevated standoff heights will lessen the package propensity to the HnP defects is provided, the authors nonetheless think that there is a reason to believe that the application of solder joints with elevated standoff heights could result in a substantial improvement in the general IC package performance, including, perhaps, its propensity to HnP defects.

Analytical Study of Flat Slab Collapse Mechanisms due to Overloading in a Cluster of Exterior Panels

Analytical equations found in the literature to give the ultimate load of folding, punching shear and local slab collapse mechanisms have been generally derived assuming a uniform load on all flat slab panels. Regarding that these formulas are not able to consider the impact of unbalanced bending moment due to partial loading, they cannot be applied to evaluate scenarios like overcrowding during operation and change of occupancy. This paper categorizes various collapse modes due to overloading in a cluster of exterior panels as well as presenting analytical equations for the ultimate loads using virtual work method and yield line theory. The study also introduces two novel local slab collapse patterns around interior columns located at the corner of overloaded area. Predicted ultimate loads indicate that flat slabs on a square column grid are expected to be more prone to punching shear and asymmetric local modes around the internal columns supporting two adjacent overburdened panels compared to other column locations.

Comparative material-based life cycle analysis of structural beam-floor systems

Abstract In a residential building, various structural flooring systems are feasible. For moderate spans (4 m–6 m) and for a predetermined column grid, distinct combinations of wood, steel and concrete elements can be implemented as beam-floor system. Besides comparing these beam-floor systems based on weight, cost, speed of installation etc., a comparison can also be based on their environmental impact. Indeed, whereas some materials appear to be environmentally friendly for many applications, this may not be true for this particular case. For such a comparison, a life cycle assessment (LCA) according to ISO 14040/44 has been implemented in this paper. In this study, the functional unit consists of a square meter of a structural beam-floor system of an arbitrary composition, i.e. three main beam materials (concrete, steel and wood) have been combined with appropriate structural floor systems. The paper presents the results of the LCAs for different impact categories, and both midpoint and endpoint assessment methods. This provides a broad idea of the environmental profile of the considered beam-floor systems representative for current Belgian building practice for the defined functional unit. Furthermore, the influence of the respective impact assessment methods (ReCiPe World versus Europe) was found to be important, especially regarding wooden structural elements. Lastly, some sensitivity analyses (use of recycled aggregates, use of aerated concrete waste, transport types and distances, ratio virgin-recycled steel) have been performed in order to obtain a more nuanced view on the setup and results of this study. These sensitivity analyses show that mainly the ratio virgin-recycled steel in a beam-floor system can result in widely varying impacts on the environment and thus give some opportunities for improved environmental impact.

Analysis of Slab-column Shearwall Structure of 6000 Tons Cold Storage

Combining with the functional requirements, the site conditions and the 6000 tons load characteristics of cold storage, so determine its structure system for the slab-column-shear wall structure. The paper recommends the design of foundation, the settings of column cap, the arrangement of shear wall, the punching shear of floor slab and the analysis and calculation results of main structure. By addition shear wall in slab-column structure to increase the overall stiffness of structure and improve the seismic performance of structure. Take the detached form between the main structure and the external wall insulation, while set anchorage beam between in the main floor and the ring beam along the axis of the column grid to enhance the overall stability of the external wall insulation.

Preparation and Study of a Type of Magneto-Rheological Materials Used in Vibration Control of Space Grid Structure

A type of Magneto-Rheological Materials (MRMs) was prepared. The off-state viscosity and the shear stress of the MRMs were characterized and studied by an advanced rotational rheometer system. A kind of Self-Decoupling Magneto-rheological (SDMR) damper was established based on these MRMs. An intellectual isolation system for grid structures was obtained by integrating SDMR damper and isolation device. The seismic whiplash effect of the top bent frame column and space grid roof of the hydropower plant could be reduced. Furthermore, the half stable increment method was proposed as the semi-active strategy. The results indicated that the SDMR dampers used at the grid roof supports setting plate rubber bearings can significantly improve the vibration performance and energy dissipation structure roof isolation system in different seismic intensity. In addition, these SDMR dampers can effectively reduce the lateral slippage of the plate rubber, so as to avoid failure or damage of the isolation system because of the transfinite horizontal displacements. Compared with the conventional damper only in case of multiple earthquakes, the damping force and adjustable multiple of this SDMR damper have better adaptability, and this SDMR damper provides a higher safety factor.

WITHDRAWN: Update on CGA packages for space applications

Abstract This paper is the 10th anniversary update of a previous paper published in 2006 on the topics of ceramic column grid array (CCGA or CGA) packages and assembly reliability. CGAs are commercial-off-the-shelf (COTS) area array packaging technologies that are now widely used in numerous high reliability applications including National Aeronautics and Space Administration (NASA) electronic systems. Key updates on packaging technologies and test data on assembly reliability characterizations are discussed in seven topics: (1) updates on the recent microelectronics packaging roadmaps, especially those for single-chip CGA packages, (2) tensile-strength test data for characterizations of the individual column integrity of CGAs before and after environmental exposures, (3) thermal cycle test data showing solder joint behavior of decoupling capacitors mounted on the high inputs/outputs (I/Os) flip-chip CGA ceramic substrate, (4) thermal cycle test results performed under a number of thermal cycle conditions including extreme cold exposures for CGA assemblies with internal wire-bond or flip-chip die having a large number of columns — from 1144 to 1752 columns and 1-mm pitch, (5) test results revealing synergistic effects of mechanical drop shock or vibration test results for “as assembled” CGAs and those with initial thermal cycling conditions, (6) images and photomicrographs taken by optical microscopy, X-ray, and C-SAM as well as failure mechanisms revealed by non-destructive and destructive methods using scanning electron microscopy (SEM), cross-sectioning, and dye-and-pry techniques, and (7) simple analytical models developed for analyses of stresses and strains of solder joints for single- and double-sided mirror-image CGA assemblies.

Could thermal stresses in a BGA/CGA-system be evaluated from a model intended for a homogeneously bonded assembly?

An analytical stress model is developed for the evaluation of thermal stresses in an inhomogeneously bonded assembly of the ball-grid-array (BGA) or column grid array (CGA) type. It is shown that one can get away with employing a simpler model intended for an assembly with a homogeneous bond, if the gaps between the supports (BGA balls or CGA columns) are small, so that the ratio \( \frac{p}{2l} \) of the pitch p (the distance between the joint centers) to the joint widths 2l is below 5, and the product kl of the parameter k of the interfacial shearing stress and half the assembly length l in the equivalent homogeneously bonded assembly is above 2.5. This is indeed the case for actual BGA and CGA systems. This finding can be used also in other areas of engineering, such as, say, mechanical or structural, when there is an intent to simplify the calculations by replacing a model for beams on separate supports by using a model intended for a beam on a continuous elastic foundation.

Coupling effects of mechanical vibrations and thermal cycling on reliability of CCGA solder joints

The microstructures and crack propagation behavior of CCGA (ceramic column grid array) solder joints after sinusoidal vibration loading, random vibration loading, and thermal cycling test have been discussed in this study. The failure mechanism of solder joints was analyzed using an experimental method and finite element analysis. It was found that the failed solder joints mainly distributed at the peripheral area in the solder column arrays and the crack initiation was mainly caused by mechanical vibrations. The deformation of PCB (printed circuit board) introduced by mechanical vibrations brought the outermost solder columns in CCGA devices with significant stress concentration and induced the initiation of cracks. Furthermore, cracks propagated during the process of mechanical vibrations and thermal cycling. The cracks propagated rapidly and the solder joints finally failed. The structure of the PCB holder was improved to relieve the vibration response from the peripheral joints. No visible crack was found in the solder joints after the same mechanical vibrations and thermal cycling test. The reliability of solder joints have been greatly improved with the new PCB holder.

Individual Building Growth Model Based on Column Grid Cellular Automata

Architectural generative design has gained an overwhelming contemporary popularity when it comes to the digital architecture research. This paper proposes a model which mimics the growth of plants. Take the growth of a plant for example, branches grow before leaves. Similarly, the inward streamlines initiated from various entrances and exits within the boundaries of individual building are like branches, so are the functional areas to leaves. With the help of this idea, a growth model framework based on flat column grid cellular automata has been established which develops organic integration between CA model, site column grid and spatial database model. This model not only simulates the expansion of architectural space, but also reflects the building spatial variation of internal structure. It is a space-time dynamic model with basic features of complex systems and has great practical reference value for architects to understand the evolution process of architectural space. To help designers improve the efficiency of project decision, this paper uses genetic algorithm to obtain the positioning of function area, so as to effectively simulate the thought process of a successful architect.

Ceramic Column Grid Array Assembly Qualification and Reliability Analysis for Space Missions

Ceramic column grid array (CCGA) devices are presently the state-of-the-art packaging solutions for advanced computational electronics. For high-reliability applications incorporating thermal and vibration loads, CCGA columns provide more compliant interconnect during thermal cycle of the assembly and improve interconnection reliability by design. Assembly of such high interconnect count device requires process development and qualification prior to their deployment in space borne payloads. CCGA assembly process development, comprehensive assembly qualification tests (thermal cycling, vibration, humidity, microsectioning, and 3-D Computed Tomography X-ray inspection), and reliability estimation are presented in this paper.

Interface and Wear Resistance of SiC Ceramic Column Grid Array Reinforced High-Chromium Cast Iron Composite Pretreated with TiH2

Abstract Reaction-bonded SiC ceramic columns were coated by titanium hydride (TiH2) powder paste firstly, and then pretreated in a vacuum at 1000 or 1400 oC for 20 min. After that, the pretreated SiC ceramic columns were fixed on a graphite plate. Subsequently, a kind of SiC ceramic column grid array reinforced high-chromium cast iron composites, with high macro-uniformity, reliability and designability of the ceramic reinforcements, were fabricated by metal casting. The microstructure analysis on the ceramic coating and the ceramic/metal interface of the SiC/iron composite reveals that a reliable metallic composite coating can be formed on the SiC surface after the pretreatment at 1400 oC which was proved to be a better pretreatment temperature. The as-formed coating would not be dissolved during the metal casting process, and the interfacial reactions between SiC and iron were also restrained effectively, resulting in an excellent ceramic/metal interface without delamination after wear testing. Moreover, the wear resistances of the SiC/iron composites with different SiC ceramic contents are improved markedly in comparison with that of the metal matrix due to the effective additions of SiC ceramic columns.

Measurement of change in properties of PCB for the irradiation of Co-60 gamma-ray for space application of CCGA484 daisy chain FPGA device

The FPGA (field programmable gate array) manufactured by using the CCGA484 (ceramic column grid array 484) package has been increasingly growing in demand day by day. However, the CCGA484 package has not been evaluated in space programs yet. In addition, the CCGA484 package is soldered on a PCB (printed circuit board) by the combination of Pb and Sn in ratios from 37% to 67%. If the thermal characteristics of the device for use in space program is to be improved and the numbers of input ports, output ports and internal gates are to increased, the pin quantity and other characteristics of the CCGA484 package must be ensured. During the qualification test for the application of the CCGA484 package in space programs, the changes in properties of the materials in the soldered parts and the changes in the electrical and the physical characteristic were investigated and yielded results that the dose increased from 0 krad to 100 krad. The difference between the electric potential before the radiation and after the accumulation of radiation was less than 0.01%.

Three-Dimensional Parametric Data Exchange for Curved Steel Bridges

Improved software interoperability is key to realizing more fully the potential benefits of integrated and accelerated project delivery in a way that also somehow ensures product quality. The increasing appeal of three-dimensional (3-D) building information modeling (BIM) notions applied to bridges [known as bridge information modeling (BrIM)] motivates the need for principled prescriptions of associated electronic data exchanges between various project stakeholders and the various software applications that they use. Such data exchanges must be sufficiently precise to facilitate detailing for fabrication and construction while being sufficiently concise to facilitate parametric modeling and thereby avoid needless data duplication. The highway geometry to which bridges must conform distinguishes BrIM from the building column grid orientation of BIM at the outset of the bridge life cycle. In contrast to the over defined highway geometry in the LandXML data exchange standard, a 3-D control curve is defined, presented, illustrated, and recommended as the basis for parametric data exchange suitable through the life cycle of steel I-girder bridges on (straight and) curved alignments. This 3-D control curve combines in a single curve the traditional horizontal control line and profile grade line that bridge structural engineers receive from highway designers to define bridge geometry. Data exchanges associated with three distinct stages in the life cycle of a steel bridge are defined and illustrated: analysis and design, detailing for fabrication, and erection and construction. The data exchange based on a 3-D control curve provides the data integrity required through the life cycle of a steel bridge.

Thermal Cycling Ramifications of Lead-Free Solder on the Electronic Assembly Repair Process

The conversion from tin-lead to lead-free electronics has created concern amongst engineers about the reliability of electronic assemblies and the ramifications that reliability changes may have on the life cycle cost and availability of critical systems that use lead-free electronics. In order to analyze the impact of the tin-lead to lead-free electronics conversion in terms of life cycle cost and availability, a simulation of fielded electronic systems to and through a board-level repair facility was created. Systems manufactured with tin-lead parts or lead-free parts that are fielded, fail and have to be repaired are modeled. The model includes the effects of a finite repair process capacity, repair prioritization, multiple possible failure mechanisms, no-fault-founds, and un-repairable units. The model is used to quantify and demonstrate the system- and enterprise-level risks posed by the conversion from tin-lead to lead-free electronics. Example analyses were performed on electronic assemblies that use SAC (tin, silver and copper) and tin-lead solder using a repair process modeled after a NSWC Crane Aviation Repair Process (8000 assemblies with 30 year support lives were modeled). The components considered consisted of ball grid array, column grid array and leadless chip carrier packaged parts that experienced three different thermal cycling profiles. The case studies revealed that when exposed to usage profiles characteristic of consumer electronics, low maximum and mean thermal cycling temperatures with long dwell times, SAC exhibited significantly reduced repair costs compared to tin-lead. For usage profiles characteristic of aerospace and high-performance applications, high maximum and mean thermal cycling temperatures with short dwell times, SAC exhibited significantly increased repair costs when compared to tin-lead.

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

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.