An efficient equivalent mechanical model for composite panel assembly and its application in assembly process optimization

Composite structures are widely used due to their superior properties, such as low density, high strength, and high stiffness-to-weight ratio (Mallick, 1993, Fiber-Reinforced Composites: Materials, Manufacturing, and Design, Marcel Dekker, New York). However, the lack of methodologies for variation modeling and analysis of composite part assembly has imposed a significant constraint on developing dimensional control for composite assembly processes. This paper develops a modeling method to predict assembly deviation for compliant composite parts in a single-station assembly process. The approach is discussed in two steps: considering the part manufacturing error (PME) only and considering both the PME and the fixture position error (FPE). Finite element method (FEM) and homogenous coordinate transformation are used to reveal the impact of the PME and the FPE. The validity of the method is verified with two case studies on assembly deviation prediction of two composite laminated plates considering the PME only and both the PME and the FPE, respectively. The proposed method provides the basis for assembly deviation prediction in the multistation composite assembly.

Flip Chip Land Grid Array (FcLGA) packages are widely used in Mobile product applications due to their thin form factor and performance. Assembly process qualification requires careful selection of materials and optimization of reflow processes to make consistent and reliable product. The fcLGA typically uses an organic substrate on which the die is reflowed instead of the copper lead frame used in QFN packages. This requires assessment of CTE mismatch and controlled reflow processes to prevent bump separation [1]. The paper reviews the selection of substrate, optimization of assembly process and reliability testing conducted for package qualification

There are only few works in literature that suggest an assembly process optimization method based on manufacturing errors in the precision manufacturing area. A multi-objective assembly process parameters evaluation and optimization method for precision assembly performance of microstructures with manufacturing errors has been proposed in this paper. Based on the model with manufacturing errors, the ABAQUS software is used for simulation and calculation, and the assembly performance evaluation indexes of the microstructures under different assembly process parameters, such as stress value, stress distribution value and pose offset, are obtained. The mapping model of the key assembly process parameters and assembly performance is established based on BP neural network. Finally, the best assembly process parameters for the optimal assembly performance are solved based on the genetic algorithm, and the method has been verified by the optimization results of preload forces of the 3D mechanism, which can be used to guide and monitor the assembly process quantitatively in the precision manufacturing area.

This paper describes the equivalent mechanical and electrical models of vibration suppression systems using piezoelectric elements. All vibration modes of the host structure are included in the equivalent mechanical and electrical models proposed in this paper. Using these equivalent models, the coupling between the original vibration modes of the host structure can be considered. The equivalent mechanical and electrical models are theoretically derived. Using these equivalent models, not only the mechanism of the vibration suppression can be understood with ease but also simulations using conventional software become possible.

An approach for simulating the assembly process where compliant airframe parts are being joined by riveting is presented. The foundation of this approach is the mathematical model based on the reduction of the corresponding contact problem to a Quadratic Programming (QP) problem. The use of efficient QP algorithms enables mass contact problem solving on refined grids, which is needed for variation analysis and simulation as well as for the consequent assembly process optimization. To perform variation simulation, the initial gap between the parts is assumed to be stochastic and a cloud of such gaps is generated based on statistical analysis of the available measurements. The developed approach is illustrated with two examples, simulation of A350-900 wing-to-fuselage joining and optimization of A320 wing box assembly. New contact quality measures are discussed.

3D technologies are now in production for high end products. TSV (middle or last) as well as copper pillar have been extensively published over the last few years, specifically for high end memory cubes. Nevertheless, when talking about very high performance systems (HPC or datacenter) or for imaging application (direct stacking of backside illuminated sensor on Logic device), finer pitch technologies are necessary. This paper proposes to enter into details on fine pitch Chip-to-Chip interconnections. More particularly, copper pillar and hybrid bonding technologies will be introduced. Two use cases will then be described; first for HPC application and secondly for high end imager application. 1- Chip-to-Chip interconnection Copper pillars lowest pitch currently available on the market is 40µm. If copper pillar will classically follow the shrinkage trend, the increasing complexity of its integration as well as of the final stacking will make shrink cost prohibitive. Additionally, resistance and capacitance increase due to miniaturization could also discourage designers from using them for advanced partitioning. Thereby, pitch from 20µm to 10µm appear to be the limit. It is one of the reasons why Leti has introduced since few years Cu-Cu hybrid bonding. The latter allowing hermetic bonding without underfill, low resistance and capacitance electrical interconnects and interesting perspectives for ultra-fine pitch. 1.1 20µm pitch copper pillar After introducing the process flow and optimizations required to adapt to fine pitch, a specific focus will be made on critical process steps: impact of barrier and seed layers nature and thickness, lithography, barrier and seed layers etching. Morphological characterization of our 3D interconnects has been achieved through interferometric measurements and FIB/SEM technique. A high uniformity over interconnects height has been obtained at wafer scale. Assembly process including pre-applied underfill will also be deeply described. A test vehicle including daisy chains ranging from 1 to more than 20000 interconnections, has been used to assess process and assembly quality. Electrical tests enable to quickly screen the best assembly configurations. After assembly process optimization, good electrical yields have been obtained and electrical resistance per interconnect is in the range of 45 to 55mΩ. 1.2 Hybrid bonding The hybrid bonding principle will be introduced. The main advantage of this technology is that neither compression nor underfill is needed. Here, fine pitch interconnect is possible thanks to high accuracy equipment. Furthermore, larger pitch application can also take benefit from the process robustness. Last results of wafer level fine pitch technology leading to less than 10µm pitch will be detailed. Extensive electrical data as well as wafer level reliability results are given. A resistance contact around 10mOhms/µm² is obtained. Roadmap and early work on more aggressive pitch (in a perspective of a 2µm to 1µm pitch) are presented. Chip level bonding from its part is based on a similar surface preparation. The complexity here comes from die handling after the wafer level surface preparation: dicing, plasma and chip-to-wafer bonding itself. Process flow will be detailed and daisy chain vehicle test will be described. Electrical data per interconnection show that resistance is very similar to the one obtained at wafer level scale. 2 – Some of potential use cases 2.1 HPC application It is clear now that we are entering the era of zettabytes of information (1021 bytes). For datacenters, the zettabyte era will have to be a “green” computing era. Interposers are key technologies to provide a cost- and power-effective solution. The performances are nevertheless limited in the case of the passive interposer, which only consists in a copper re-routing. To go further, we propose the new concept of “CMOS interposer,” a high-performance but smaller interposer that embeds some logic functions and power management. This concept is only valuable if we have very high density of interconnects from die to die, so through the interposer. Pitch of 20µm was simulated and sufficient considering the whole system, knowing that the interposer embeds 150K interconnections. 2.2 Imager application Stacked imagers, since 2 to 3 years, and more particularly Backside illuminated sensor over logic stack, have been reported by major players in the industry. Connect as nearer as possible pixels to data treatment is a clear advantage of 3D Stack for imaging. Wafer level bonding integration is well suited to this application, as both wafers can be prepared in parallel, their yield are supposed to be good (mature process), top and bottom can be designed to have similar size. A test vehicle will be described and electrical data will be given. Early work on reliability (thermal cycling and electromigration) will be detailed. Figure 1

Chip packaging interaction (CPI) has drawn great attention to advanced silicon technology nodes due to the introduction of Low-K (LK) and Ultra Low-K (ULK) materials in back end of line (BEOL) and Cu pillar in chip package interconnects. This paper summarizes GLOBALFOUNDRIES's activities in CPI studies for the 20 nm technology node, which includes CPI structure design, BEOL process characterization and optimization, assembly process optimization and reliability tests. The key issues and challenges were identified, analyzed, and overcome through a Design of Experiment (DOE) study in BEOL Q-time and reflow parameters in assembly process. It has been found that 1) BEOL ULK layer Q-time before SiCN capping is critical for moisture diffusion into BEOL materials, which affects both electrical performance and reliability; 2) Reflow temperature plays key role to control the package warpage to avoid non-wet issue. Package level reliability evaluation was performed and the results were reported. Through this study, it has been demonstrated that GLOBALFOUNDRIES's 20 nm technology successfully passed all CPI reliability tests. CPI challenges for future technology nodes and emerging packaging integration solutions are also discussed in the paper.

Real-time information driven intelligent navigation method of assembly station in unpaced lines

This paper focus on optimization of assembly process using DFMA on portable bluetooth speaker. However, the problem regarding this speaker is it comes with box shaped that is outdate and bulky. It also does not resistant to water as it limited to dry places only. The objectives of this paper are to redesign a much compact and sleek looking portable bluetooth speaker that meets the needs of the music lovers and to assure the speaker to be water resistant. The design of portable bluetooth speaker is using CAD software and then transfer to Finite Element Analysis (FEA) to analyses the capabilities of part design. At the end of this paper, this research will give understanding about design using CAD software and do analysis that improved the portable bluetooth speaker. Hence, Sonic Gear Pandora Mini Portable Bluetooth Speaker in grey colour was chosen as a benchmark in this paper.

This paper reports on analysing components of a drone in minimising the quantity required as well as to examine the potential sustainable design that can be improved. Design for Manufacturing Assembly (DFMA) and Life Cycle Analysis (LCA) were applied and combined in this work. Results showed how the numbers of components were reduced down to 38% after applying DFMA, whereas the LCA proved that the weight was reduced to 30%, carbon footprint 38.4%, water eutrophication 36.4%, air acidification 67% and total energy consumed 31.2%. This newly approach is significant in proving the effectiveness of both tools to be applied in reducing the cost of manufacturing a drone as well as to improve the sustainable aspects of designing products.

In future manufacturing human-machine interaction will evolve towards flexible and smart collaboration. It will meet requirements from the optimization of assembly processes as well as from motivated and skilled human behavior. Recently, human factors engineering has substantially progressed by means of detailed task analysis. However, there is still a lack in precise measuring cognitive and sensorimotor patterns for the analysis of long-term mental and physical strain. This work presents a novel methodology that enables real-time measurement of cognitive load based on executive function analyses as well as biomechanical strain from non-obtrusive wearable sensors. The methodology works on 3D information recovery of the working cell using a precise stereo measurement device. The worker is equipped with eye tracking glasses and a set of wearable accelerometers. Wireless connectivity transmits the sensor-based data to a nearby PC for monitoring. Data analytics then recovers the 3D geometry of gaze and viewing frustum within the working cell and furthermore extracts the worker's task switching rate as well as a skeleton-based approximation of worker's posture associated with an estimation of biomechanical strain of muscles and joints. First results enhanced by AI-based estimators demonstrate a good match with the results of an activity analysis performed by occupational therapists.

A special class of quadratic programming (QP) problems is considered in this paper. This class emerges in simulation of assembly of large-scale compliant parts, which involves the formulation and solution of contact problems. The considered QP problems can have up to 20,000 unknowns, the Hessian matrix is fully populated and ill-conditioned, while the matrix of constraints is sparse. Variation analysis and optimization of assembly process usually require massive computations of QP problems with slightly different input data. The following optimization methods are adapted to account for the particular features of the assembly problem: an interior point method, an active-set method, a Newton projection method, and a pivotal algorithm for the linear complementarity problems. Equivalent formulations of the QP problem are proposed with the intent of them being more amenable to the considered methods. The methods are tested and results are compared for a number of aircraft assembly simulation problems.

Optimization of Assembly Processes by Heated Air Technology

Designing highly selective and stable water transport channel through graphene oxide membranes functionalized with polyhedral oligomeric silsesquioxane for ethanol dehydration

In order to improve the real-time control and optimization of assembly process, this article takes the basic execution unitassembly station as the study subject. Based on real-time manufacturing information, the concept of the intelligent navigation of assembly activities is put forward. Through the application of RFID technology to capture the multi-source information, three kinds of navigation services, namely real-time assembly operating guidance service, collaborative manufacturing service among assembly stations and real-time optimization service of task queue, are designed to implement optimal navigation. The presented concept and services will facilitate the real-time data driven process monitor and control between the assembly line and assembly station.