Leadframe Mold Lock Study and Optimization for Flag Size Reduction using Finite Element Analysis and Reliability Testing for 3L SOT223 Package

The X Architecture is an integrated-circuit wiring architecture based on the pervasive use of diagonal wires. Compared with the traditional, currently ubiquitous, Manhattan architecture, the X Architecture demonstrates a wire length reduction of more than 20% and a via reduction of more 30%. Because of the rapidly increasing percentage of delay due to interconnect and the manufacturing challenges due to vias in the nanometer realm, these length and via reductions result simultaneously in a chip performance improvement of 10%, a power reduction of 20%, and a die cost reduction of 30%. Furthermore, the reduction in both wire length and parallel runs on different layers often both reduces die size and improves signal integrity. Remarkably, on virtually every important measure of chip quality, the X Architecture is superior to the Manhattan architecture.While diagonal wiring has been discussed for years, and short diagonal jogs have even been used for years, pervasive diagonal wiring has not been used on an IC before 2002 (to our knowledge). The fundamental reasons for this are not manufacturing limitations, as might be suspected, but EDA limitations, and the changes required to take full advantage of the X Architecture are significant and numerous. In particular, routing must be not only octilinear, but also gridless and non-preferred direction. In addition, significant changes are required at least in floorplanning, placement, global routing, extraction, power routing, clock routing, wire length estimation (e.g., in synthesis), database, graphics, and even data interchange formats. The folklore that 45-degree wiring might not be worth the trouble because it can provide only a 10% reduction in wire length is rooted in the incorrect assumptions that (a) only the router must change, (b) the router must resemble contemporary, preferred-direction, net-at-a-time maze routers, and (c) that wire length is the only major contributor to interconnect delay.In this short paper, we present some of the challenges and opportunities afforded by the X Architecture and show some early results that demonstrate the promise of pervasive, diagonal wiring, reflecting our belief that five years from now, virtually all, high-performance, integrated circuits will use the X Architecture.

Microelectronic components used in automotive applications have to meet very strict reliability requirements. In addition to the mechanical or thermomechanical stresses resulting from manufacturing and application conditions, also chemical processes have to be considered if the systems are exposed to harsh environmental conditions. In these cases, mechanical stresses do not only determine the risk of deformation-induced failure and cracking but can also affect the diffusion kinetics of any chemical species, e.g. humidity and corrosive compounds. This paper addresses chip-package interaction effects that determine the probability of chip damage by corrosion. The effects of mechanical stress resulting from both the package and from additional external loading on humidity diffusion kinetics, and finally on the resulting failure probability were investigated using finite element analysis (FEA). The simulation results were compared to the experimentally determined failure risk. Further the derived numerical results showed a distinct correlation with the experimentally detected failure risks provoked by different accelerated reliability tests. To validate the correlation between stress-supported diffusion and the occurrence of corrosive failures, a specific dedicated experimental test setup was created. The results showed a very good correlation of corrosive failure modes in the active die structures to the mechanical stresses at the critical regions determined from the accompanying FEA package simulation. In addition, scanning electron microscope investigations revealed that the corrosive chip damage started at locations that were also in accordance with the simulation results.

Higher demand of Rds(on) in power MOSFET package introduces the copper clip is used as interconnect material, this package construction increase CTE mismatch with mold compound. Warpage can be categorised as convex warpage (leadframe warpage in cavity molding) and concave warpage (mold compound warpage in map molding). This paper focus on convex leadframe warpage, where leadframe jamming & damage are observed at molding offloading tracks which subsequently effecting yield. Mold parameter, mold compound formulation, package outline, leadframe design, thermal residual stress characterizations are essential to minimize convex warpage.[1] Four TDSON packages single heatsink, dual heatsink, singles heatsink fused lead and single heatsink fused lead LTI has been studied. Copper material within package outline increase > 2.34% in fused lead packages, increasing CTE mismatch between copper-die-mold compound warpage start to be seen. To maintain current fused lead packages outline, optimization of leadframe design focusing at non-functional area is studied and the correlation of warpage versus copper material is established. Result shows reduction of warpage of the single heatsink fused lead from 5 mm to minimal of 1.4mm. Selection of basic resin, filler loading, warpage additive in mold compound plays an important role in thermal & chemical shrinkage. Lower Tg improves convex warpage, addition of short molecular chain biphenyl & LMW into Multi-Aromatic is needed. Increment of CTE to 14ppm/dC alone reduce warpage from 5mm to minimal 3mm, addition of Warpage Relief Additive (abbreviated as WRA) reduces convex warpage to 1.5mm. Correlation of WRA with mold shrinkage & convex warpage are established, result reveals addition of WRA to max 4.6% reduces warpage by 3.5mm. Addition of unreactive WRA reduces mold compound curability. Our studies also show thermal residual stress relief identified can improve convex warpage, this paper focus on of leadframe cooling time and design of degating cooling station. Study show cooling station tubing position, blowing direction and cooling mechanism contribute for different equipment contribute to 20% warpage magnitude.

Channel routing problem of area minimization is a well-defined problem in VLSI physical design automation. In this paper we have developed algorithms for computing reduced wire length channel routing solutions using a purely graph theoretic framework, TAH (track assignment heuristic) that was designed for computing minimum area routing solutions. Here we consider the total wire length of a routing solution as one of the most important factors of high performance computing. Reduction in wire length is important from signal delay as well as from the viewpoint of cost of wire segments required in interconnecting all the nets. The framework is designed for computing routing solutions in two-layer channels, and extended to route three-layer routing also in a modular fashion. All the algorithms developed under the framework of TAH are executed for computing no-dogleg and dogleg routing solutions for most of the well-known benchmark channels, with reduced total area and/or total wire length in two- and three-layer channel routing. Performance of our algorithms is highly encouraging.

Machine learning based effective linear regression model for TSV layer assignment in 3DIC

In order to develop test methods for qualification of commercially available plastic-leaded chip-carrier (PLCC) packages, a special test circuit has been used. This circuit contains piezoresistive sensors for measurements of mechanical stress, resistors for power dissipation and diodes for temperature measurements. The mechanical stress has been measured after die attach on different types of lead frames and after encapsulation in different molding compounds. Alloy 42 lead frames gave rise to less mechanical stress than copper-lead frames, but for alloy 42 there are cracks in the plastic instead. These cracks are due to the large difference in coefficient of thermal expansion between the lead frame and the molding compound. The measured stress level, as well as the aluminium-metal movements, are almost proportional to the coefficient of thermal expansion of the molding compound. The mechanical stress is relatively constant during a temperature cycle. This stress level is reached when the package has cooled down immediately after encapsulation. The highest stress levels during temperature cycling are reached at the lowest temperature. >

Mechanical stress and electric potential in cymbal piezoceramics by FEA

Footprint scaling may reduce wire lengths when more metal layers are available for routing. To achieve optimal wire length, footprint should be very small in which case pin density will be extremely high. However, high pin density may lead to detailed routing failure. We demonstrate that there is a threshold pin density beyond which standard routing heuristics fail to access pins on the bottom layer, even with unlimited number of metal layers available for routing. Future technologies, such as vertical slit field-effect transistor (VeSFET), may have layouts with pin density exceeding the threshold. We show that VeSFET layouts are still routable within footprint using two-sided routing. Compared to one-sided routing, two-sided routing achieves shorter wire lengths and fewer vias, hence lower interconnect capacitance and better performance.

With the standard approach for establishing multicast connections over a network, network nodes are utilized to forward and duplicate the packets received over the incoming links. Recently, there has been a significant interest in a novel paradigm of network coding. Network coding generalizes the traditional routing approach by allowing the network nodes to generate new packets by performing algebraic operations on packets received over the incoming links. It has been shown that network coding can increase the throughput of multicast communication. In this paper, we explore the benefits of network coding for improving the routing characteristics of VLSI designs. We demonstrate that when data has to be routed across the IC, it is often beneficial to perform network coding. Initial results demonstrate that network coding can result in a healthy reduction in wire length, wire area, interconnect power as well as the active area associated with the interconnects. This comes at a small delay penalty.

The reliability of the measurement system, accuracy, and precision are significant criteria at any measurement procedure. Strain gage sensors are one of the tools to measure the strain of structures in engineering applications. Different controllable and extraneous parameters will change the accuracy and precision of the strain gauges. As a result, it is valuable to investigate the most significant parameters and the percentage of their contributions affecting the strain measurement. This paper presents the multi-objective optimization in strain gauge measurements to determine the Reliability and Noise indices. The best set of parameters with a high-reliability index (which means low noise index) for strain measurement based on two significant objectives of accuracy and precision are evaluated. The significant parameters, their optimal levels and percentage of contributions are identified according to the Taguchi and Fuzzy Analytic Hierarchy Process (FAHP) with Technique for the Order Performance by its Similarity to the Ideal Solution (TOPSIS) methods. To obtain this evaluation, three levels (L1, L2, and L3) of temperature (P1), the length of wires (P2), and the point of applied force (P3) are considered. This configuration leads to L9 orthogonal array of Taguchi approach based on the number of parameters and their levels. The triangular membership function for the weightiness of accuracy and precision is used via AHP. By using the Taguchi method, the optimum set of parameters are identified as P1 at L1, P2 at L2, and P3 at L3 to have a higher reliability index compared to trial 8. By applying the optimum design of experiment, it is found that the reliability index is 95%. The results also show that the highest reliability index is related to trial 8 with 87.65% reliability. Finally, the combination of FAHP and TOPSIS with Taguchi method for multi-objective optimization is introduced and proposed as a practical and useful model to determine the best set of parameters with the highest reliability index in strain measurement.

Research on resolving implant fracture is still gaining attention as it can be a serious treatment failure outcome. The implant fracture is likely to occur due to increased stress in implant body associated with peri-implant bone resorption. This study aimed to investigate the relationship between degree of peri-implant bone resorption and stress distribution in implant body by using finite element analysis (FEA). The magnitude and direction of loads on implants at the mandibular molar region were measured with 3D piezoelectric force transducers in a patient during maximal voluntary clenching, grinding and tapping to obtain input for the FEA as the loading condition. Simplified finite element bone models were generated to simulate the six patterns of peri-implant bone resorption progression which the bone levels from implant platform were set at 0, 1, 2, 3, 4 and 5mm. Three types of implants with different diameters (3.5, 4.0 and 5.0mm), corresponding abutments and screws were created. FEA using the in vivo measured load was conducted to investigate how peri-implant bone loss affects stress distribution in the implant body. Loading condition affected stress distribution in the implant body. As bone resorption increased, von Mises stress in the implant body became larger, which was marked in smaller diameter implants, and this change was amply demonstrated when the bone resorption increased from 0 to 2mm. The FEA demonstrated that as peri-implant bone loss increased, the magnitude of stress in the implant increased, especially in small diameter implants.

Optical second harmonic generation (SHG) method has been applied to the investigation of mechanical stress condition of BESOI (bonded and etched-back silicon on insulator) wafers. SHG scanning of SOI wafers show drastic variations, which are explained, in the case of thin film BESOI, by the mechanical stress arising from the bonding of rough surfaces, and, in the case of thick film BESOI wafer, by the presence of polish-induced strain that results from the thinning process of the wafer. SHG rotational dependence was observed for BESOI wafers, and its symmetry preservation indicates essentially sound silicon film quality despite a high level of mechanical stress. Mechanical stress effect on the SHG signal is also demonstrated through externally applied stress on the BESOI wafer. SHG method is shown to be able to characterize mechanical stress of BESOI wafers and may even identify the sources of the stress.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

MiRNA-140-5p Modulates Cartilage Mechanical Environment by Preserving Surface Stress Homeostasis.

Stress governs tissue phenotype at the femoral insertion of the rabbit MCL

Precise knowledge regarding the mechanical stress applied to the intervertebral disc following each individual spine motion enables physicians and patients to understand how people with discogenic back pain should be guided in their exercises and which spine motions to specifically avoid. We created an intervertebral disc degeneration model and conducted a finite element (FE) analysis of loaded stresses following each spinal posture or motion. A 3-dimensional FE model of intervertebral disc degeneration at L4-5 was constructed. The intervertebral disc degeneration model was created according to the modified Dallas discogram scale. The von Mises stress and range of motion (ROM) regarding the intervertebral discs and the endplates were analyzed. We observed that mechanical stresses loaded onto the intervertebral discs were similar during flexion, extension, and lateral bending, which were greater than those occurring during torsion. Based on the comparison among the grades divided by the modified Dallas discogram scale, the mechanical stress during extension was greater in grades 3-5 than it was during the others. During extension, the mechanical stress loaded onto the intervertebral disc and endplate was greatest in the posterior portion. Mechanical stresses loaded onto the intervertebral disc were greater in grades 3-5 compared to those in grades 0-2. Our findings suggest that it might be beneficial for patients experiencing discogenic back pain to maintain a neutral posture in their lumbar spine when engaging in daily activities and exercises, especially those suffering from significant intravertebral disc degeneration.