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Electronics packages in precision guided munitions are used in guidance and control units, mission computers, and fuze-safe-and-arm devices. They are subjected to high g-loads during gun launch, pyrotechnic shocks during flight, and high g-loads upon impact with hard targets. To enhance survivability, many electronics packages are potted after asse...
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Citations
... Potting is the process of insulating the array with polymeric materials having a high bonding ability, small expansion coefficient, high mechanical endurance, and strong corrosion resistance. The array and potting materials are made into a solid whole, which is waterproof and resistant to shock and vibration [3]. Because an acoustic transducer array is the object to be potted in this study, the potting should not only ensure protection but also consider the acoustic performance. ...
Cymbal transducers are often used in arrays for underwater communication and detection systems. The working environment of a cymbal array is underwater; therefore, waterproofing, salt-corrosion prevention, and impact resistance are necessary for stable operation of the array. Hence, we simulated potting a cymbal array with 15 different rubber and epoxy materials available in the market, using the finite element method, and analyzed their effect on the transmitting voltage response spectrum of the array. From the analysis results, we selected the material that would achieve the widest frequency bandwidth, while preserving the structural stability of the array. A potting method corresponding to the selected material was suggested as well. This study provides guidelines for the selection of a potting material for use in underwater transducer arrays.
... Polyurethanes (PU) are widely used in the polymer industry as well as in everyday life. PU with various properties are used in a variety of applications such as apparel [1,2], appliances, automotive [3,4], flooring, furnishings, medical [5,6], marine [7], building and construction [8,9], composite wood [9], electronics [10], and packaging [11]. It can be produced by the reaction of isocyanates and polyols. ...
... In 2013, AS Haynes [162] reported a study on the reliability of the potted fuse under coupling effect of temperature and shock. The research found significant changes in the mechanical character of potting material at high temperatures (71 • C) and low temperatures (<51 • C), which affect the reliability of the system. ...
The reliability of MEMS in shock environments is a complex area which involves structural dynamics, fracture mechanics, and system reliability theory etc. With growth in the use of MEMS in automotive, IoT, aerospace and other harsh environments, there is a need for an in-depth understanding of the reliability of MEMS in shock environments. Despite the contributions of many articles that have overviewed the reliability of MEMS panoramically, a review paper that specifically focuses on the reliability research of MEMS in shock environments is, to date, absent. This paper reviews studies which examine the reliability of MEMS in shock environments from 2000 to 2020 in six sub-areas, which are: (i) response model of microstructure, (ii) shock experimental progresses, (iii) shock resistant microstructures, (iv) reliability quantification models of microstructure, (v) electronics-system-level reliability, and (vi) the coupling phenomenon of shock with other factors. This paper fills the gap around overviews of MEMS reliability in shock environments. Through the framework of these six sub-areas, we propose some directions potentially worthy of attention for future research.
... In addition, such a design architecture would be costly. For flexible LED signage modules, various packaging materials and methods are available [19][20][21][22][23]. Haynes et al. [19] investigated polyurethane for potting assembly and packaging of precision guided munitions. ...
... In addition, such a design architecture would be costly. For flexible LED signage modules, various packaging materials and methods are available [19][20][21][22][23]. Haynes et al. [19] investigated polyurethane for potting assembly and packaging of precision guided munitions. In electronics packaging, defects can occur in encapsulated micro-electronic packages at any stage during manufacturing and operation, particularly chip adhesion and encapsulation at the substrate and PCB interfaces [21,24,25]. ...
... Therefore, no further optimization was attempted. For packaging flexible LED modules, a wide range of flexible potting resins are available, e.g., polyurethane and silicones [19,23]. In this study, we considered polyurethane as it is a commonly used material in electronics potting and packaging. ...
This paper presents a new design architecture for mechanically flexible light-emitting diode (LED) signage modules for applications in digital advertising on curved surfaces. The new design comprises an array of commonly used rigid printed circuit boards (PCBs) but of smaller size with some spacing between them, which is encapsulated by a flexible substrate or potting material, instead of a large single rigid PCB in the entire LED module as in the case of conventional LED signage modules. Commonly used through-hole type RGB LEDs are considered. To demonstrate the design, manufacturing, and mechanical flexibility of the design, a prototype LED signage module with a typical industry standard size of 304 mmx304 mmx10 mm was designed and fabricated. Experimental testing and finite element simulations were conducted to analyze mechanical flexibility and internal stresses in the module. The results demonstrate that the new design provides flexible LED modules, without altering the conventional LED control system. It is shown that maximum stress occurs in the spacing between the PCBs and is small even for large module deflection. As the curvature of module deflection was decreased, the maximum stress increased, indicating as an important design parameter for the module deflection. The proposed design architecture will enable both indoor and outdoor digital advertising using billboards on a wide range of curved surfaces.
... The high frequency vibrations were also largely attenuated after fill-in of the potting resin. Haynes et al. [22] further investigated the stress response under different temperatures for both potted and unpotted cases. In this work, we extend earlier studies by developing strategies to ensure further reductions in the stress state under shock loads. ...
Shock loads which are characterized by high intensity, short duration, and vibration at varied frequencies can lead to the failure of embedded electronics typically used to operate/ control numerous devices. Failure of electronics renders these devices ineffective, since they cannot carry out their intended function. It is therefore the objective of this work to determine the behavior of a typical electronic board assembly subject to severe shock loads and the means to protect the electronics. Specifically, three aspects of the work were considered using 3D finite element (FE) simulations in supercomputer environment. The first was concerned with the dynamic behavior of selected electronic devices subject to shock loads. The second with the ability of different potting materials to attenuate the considered shock loads. The third was with the use of a new bilayer potting configurations to effectively attenuate the shock load and vibration of the electronic
board. The shock loads were delivered to the Joint Electron Device Engineering Council (JEDEC) standard board using simulated drop impact test. The effectiveness of different
protective potting designs to attenuate the effect of shock loads was determined by considering
the two key factors of electronics reliability: the stress in the interconnection and deformation of the printed circuit board. Our results reveal the remarkable effectiveness of the bilayer potting approach over the commonly adopted single potting attenuation strategy.
... These models are based on the material data presented in Refs. [16,17]. For this potting, the glass transition temperature is about À10 C, which is within the usual operating range for the Army. ...
... More details of the potting model are provided in Refs. [16,17]. ...
... In this comparison, the electronics are modeled with potting, with and without solder. The assembly is at cold temperature (233 K) and the potting is relatively stiff due to operation below the glass transition temperature [16,17]. The Von Mises stresses in the chips near the 15,000 G force are shown in Fig. 9. ...
Smart projectiles use electronic components such as circuit boards with integrated circuits to control guidance and fusing operations. During gun-launch, the electronics are subjected to 3-dimensional g-forces as high as 15,000 G. The U. S. Army uses finite element analysis to simulate electronics with high-g, dynamic loads. Electronics are difficult to model due to the large variation in size, from large circuit boards, to very small solder joints and solder pads. This means that to accurately model such small features would require very large models that are computationally expensive to analyze; often beyond the capability of resources available. Therefore, small features such as solder joints are often not included in the finite element models to make the models computationally tractable. The question is: what is the effect on model accuracy without these small features in the model? The purpose of this paper is to evaluate the effect that solder joints and solder pads have on the accuracy of the structural analysis of electronic components mounted on circuit boards during gun shot. Finite element models of simplified circuit boards, chips, and potting were created to do the evaluation. Modal analysis and dynamic structural analysis using typical gun loads were done. Both potting at high temperature (soft) and potting at low temperature (stiff) were used in the dynamic analysis. In the modal analysis there was no potting. All of these models were run with and without solder. In all cases, the results differed between the models with solder and those without. In the models with potting, there was a difference in magnitude and stress distribution between the models with and without solder. This indicates that there is a significant reduction in accuracy when solder is not included in the model.
