Encapsulating Protective Layers for Enhancing Survivability of Circuit Board Assemblies in Harsh and Extreme Environments

Author(s):  
Nien-Hua Chao ◽  
John A. Dispenza ◽  
Mario E. DeAngelis

Potted electronics are becoming more common in precision-guided artillery-launched munitions and also missile systems due to the requirements for miniaturization and structural-robustness. In this paper we have presented a methodology for encapsulating circuit board assemblies (CBA) with a thin polymer layer. The protective polymer layer is both flexible and soft enough to protect the CBA from damage caused by CTE mismatches, and without any appreciable degradation in the structural support during the high-g forces of projectile launch. The application process described here allows for the use of a broad range of polymer materials including those that may not be formed directly against an actual CBA. Proof-of-concept experimental tests and finite-element simulations have been performed and the tests and simulation results are shared in this paper. In addition, the protective polymer layer can also be used to improve in-circuit board crosstalk and RF interference shielding, tin-whisker growth control, moisture barrier properties, and thermal management for un-potted and potted CBAs.

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Nien-Hua Chao ◽  
John A. Dispenza ◽  
Mario DeAngelis

Potted electronics are becoming more common in precision-guided smart munitions designs due to the requirements for miniaturization and structural-robustness. In most of these applications, the potted electronics are inactive for most of their lifetime and may be stored without environmental (temperature and humidity) controls for up to 20 yr. The uncontrolled environment for smart munitions however makes the thermal management task especially difficult due to the coefficient of thermal expansion (CTE) mismatch that can exist between the potting material and the electronic components. In this paper, we will do the following: (1) present a methodology being developed for reducing the thermal stresses to the potted electronics used in uncontrolled environments by encapsulating the circuit board assembly (CBA) with a thin polymer layer which has been precisely formed to conform to the imprecisely shaped, as-populated, CBA. The protective polymer layer will be both flexible and soft enough to protect the CBA components from damage caused by thermal expansion mismatches, but not degrade the structural support that the potting provides during high-g force projectile launches, (2) discuss how the protective polymer layer methodology can also be used to lessen in-circuit board crosstalk, improve shielding from external RF interference, control tin-whisker growth, and enhance moisture barrier properties and thermal management for CBAs, and (3) demonstrate how to improve the smart munitions survivability under extreme high-g applications through the use of syntactic foams and material characterization before and after accelerated temperature-cycling and thermal-aging tests.


Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2588
Author(s):  
Mansuri M. Tosif ◽  
Agnieszka Najda ◽  
Aarti Bains ◽  
Grażyna Zawiślak ◽  
Grzegorz Maj ◽  
...  

In recent years, scientists have focused on research to replace petroleum-based components plastics, in an eco-friendly and cost-effective manner, with plant-derived biopolymers offering suitable mechanical properties. Moreover, due to high environmental pollution, global warming, and the foreseen shortage of oil supplies, the quest for the formulation of biobased, non-toxic, biocompatible, and biodegradable polymer films is still emerging. Several biopolymers from varied natural resources such as starch, cellulose, gums, agar, milk, cereal, and legume proteins have been used as eco-friendly packaging materials for the substitute of non-biodegradable petroleum-based plastic-based packaging materials. Among all biopolymers, starch is an edible carbohydrate complex, composed of a linear polymer, amylose, and amylopectin. They have usually been considered as a favorite choice of material for food packaging applications due to their excellent forming ability, low cost, and environmental compatibility. Although the film prepared from bio-polymer materials improves the shelf life of commodities by protecting them against interior and exterior factors, suitable barrier properties are impossible to attain with single polymeric packaging material. Therefore, the properties of edible films can be modified based on the hydrophobic–hydrophilic qualities of biomolecules. Certain chemical modifications of starch have been performed; however, the chemical residues may impart toxicity in the food commodity. Therefore, in such cases, several plant-derived polymeric combinations could be used as an effective binary blend of the polymer to improve the mechanical and barrier properties of packaging film. Recently, scientists have shown their great interest in underutilized plant-derived mucilage to synthesize biodegradable packaging material with desirable properties. Mucilage has a great potential to produce a stable polymeric network that confines starch granules that delay the release of amylose, improving the mechanical property of films. Therefore, the proposed review article is emphasized on the utilization of a blend of source and plant-derived mucilage for the synthesis of biodegradable packaging film. Herein, the synthesis process, characterization, mechanical properties, functional properties, and application of starch and mucilage-based film are discussed in detail.


Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2835 ◽  
Author(s):  
Zhongjie Hou ◽  
Jinxi Xiang ◽  
Yonggui Dong ◽  
Xiaohui Xue ◽  
Hao Xiong ◽  
...  

A prototype of an electrocardiogram (ECG) signal acquisition system with multiple unipolar capacitively coupled electrodes is designed and experimentally tested. Capacitively coupled electrodes made of a standard printed circuit board (PCB) are used as the sensing electrodes. Different from the conventional measurement schematics, where one single lead ECG signal is acquired from a pair of sensing electrodes, the sensing electrodes in our approaches operate in a unipolar mode, i.e., the biopotential signals picked up by each sensing electrodes are amplified and sampled separately. Four unipolar electrodes are mounted on the backrest of a regular chair and therefore four channel of signals containing ECG information are sampled and processed. It is found that the qualities of ECG signal contained in the four channel are different from each other. In order to pick up the ECG signal, an index for quality evaluation, as well as for aggregation of multiple signals, is proposed based on phase space reconstruction. Experimental tests are carried out while subjects sitting on the chair and clothed. The results indicate that the ECG signals can be reliably obtained in such a unipolar way.


2021 ◽  
pp. 51-59
Author(s):  
Ольга Владимировна Бессараб ◽  
Наталья Евгеньевна Посокина

Рассмотрены основные виды реторт-упаковки, полимерные и комбинированные материалы, применяемые для ее изготовления. С учетом области применения такой упаковки к ней применяются определенные требования: устойчивость к стерилизации при температуре не ниже 120 °С, паро- и влагонепроницаемость, химическая инертность к консервируемым продуктам, герметичность, низкая газопроницаемость. Для придания реторт-упаковке требуемых свойств ее изготавливают из многослойных полимерных или комбинированных материалов, каждый из слоев которого выполняет определенные функции. В качестве внешних слоев чаще всего используют полипропилен или полиэтилентерефталат, так как эти полимерные материалы термически и химически устойчивы, паро- и влагонепроницаемы. В качестве серединного слоя используют материалы, являющиеся барьерами для газов - алюминиевую фольгу, металлизированные пленки, этиленвиниловый спирт, полиамид. Для изготовления таких материалов и упаковки применяют соэкструзию полимеров, многослойное литье под давлением или ламинирование. Благодаря барьерным свойствам полимерных и комбинированных материалов по отношению к кислороду реторт-упаковка обеспечивает сроки годности консервированной продукции до 5 лет. Это сравнимо с консервами в традиционной упаковке, что позволяет рассматривать реторт-упаковку из полимерных и комбинированных материалов в качестве альтернативы стеклянной и металлической упаковке. В розничной продаже консервы в реторт-упаковке из полимерных и комбинированных материалов представлены в основном мясными паштетами, пюреобразными консервами для детского питания, соусами и кетчупами, а также влажными кормами для животных. В реторт-упаковке также выпускают тушеное мясо, первые и вторые обеденные блюда, консервированный сыр, некоторые виды фруктовых и овощных консервов, но это в основном продукция для спецконтингента (например, военнослужащие, космонавты). This article describes the main types of retortable package, polymer and combined materials used for its. Taking into account the application of such package, certain requirements apply to it: resistance to sterilization at a temperature of not less than 120 °C, vapor and moisture resistance, chemical inertia to canned products, leakproofness, low gas permeability. To give the retort packaging the required properties, it is made of multilayer polymer or combined materials, each of the layers of which performs certain functions. As the outer layers, polypropylene or polyethylene terephthalate is most often used, since these polymer materials are thermally and chemically stable, vapor and moisture-proof. As the middle layer, materials that are barriers to gases are used aluminum foil, metallized films, ethylene vinyl alcohol, polyamide. For the manufacture of such materials and package, polymer co-extrusion, multi-layer injection molding or lamination are used. Due to the barrier properties of polymer and combine materials in relation to oxygen, retortable packaging provides shelf life of canned products up to 3 years. This is comparable to canned food in traditional package, which allows us to consider retortable package made of polymer and combined materials as an alternative to glass and metal packaging. In retail sales, canned food in retortable package made of polymer and combined materials is mainly represented by meat pates, canned puree for baby food, sauces and ketchups, as well as wet animal feed. The retortable packaging also produces stewed meat, dinner dishes, canned cheese, some types of fruit and vegetable canned food, but these are mainly products for special contractors (for example, military personnel, astronauts).


Author(s):  
Heejin Park ◽  
Ji-Hyuk Lim ◽  
Suk-Jin Ham ◽  
Bongtae Han

In this paper, the standard procedures for measuring moisture sorption properties of thin film form of polymer materials such as polyethylene terephthalate (PET) using thermo-gravimetry method and permeation method to characterize the moisture diffusion in polymer is presented. Analytical solution of moisture diffusion and FEA implementation using thermal-moisture analogy for comparison with measurements are presented, in which temperature dependent material properties are characterized. The measurement of permeability is used for validation of moisture diffusion characteristics. Nonlinear behavior of moisture diffusion dependent on concentration is investigated using a specimen having diffusion on half side and diffusivity constants are obtained by solving non-Fickian model and minimizing errors of least square with measurement. Application of characterizing moisture sorption properties to moisture effect on the interfacial layer in multi-layered printed circuit board (PCB) and estimation of relative humidity (RH) through permeation of moisture in hermetic sealing of crystal resonator are presented in this paper: i) The discrepancy of moisture concentration at the interlayer in multi-layered PCB was estimated as loading condition varies. ii) Moisture content through sealant based on temperature dependent permeability was estimated using mixture of ideal gases and vapor pressure.


2020 ◽  
Author(s):  
Zetao Guo ◽  
Xiang Xu ◽  
Tao zhang

The MEMS magnetometer determines the orientation for the MEMS inertial system. Because of the large noise of the MEMS magnetometer and the interference of soft and hard iron outside, the measurement error of the MEMS magnetometer is large. To reduce the effects of the random noises, the MEMS magnetometer arrays are designed in this paper. In our design, thirty-two MEMS magnetometers are welding on a printed circuit board (PCB), which area is 5×5 cm2. The forty general-purpose input-output (GPIO) ports, which are thirty-two data ports and eight clock ports, are used to collect the data of MEMS magnetometers. Then, averaging the thirty-two measurements of the MEMS magnetometers, the random noises of the measurements of the MEMS magnetometers can be reduced. Based on the averaging operation for the collected sensors’ data, a unified measurement model for the MEMS magnetometer arrays is constructed. Using the unified measurement model, an adaptive Kalman filter is developed to estimate the unknown parameters. To validate the performance of the MEMS magnetometer arrays, the simulation and experimental tests are designed. The test results show that, comparing with the single MEMS magnetometer, the random noises of the MEMS magnetometer arrays are reduced effectively.


2017 ◽  
Vol 71 (1) ◽  
pp. 85-94
Author(s):  
Spasenija Milanovic ◽  
Biljana Pejic ◽  
Vera Lazic ◽  
Bojan Konstantinovic ◽  
Milan Blagojevic

Functional food is positioned above the traditional, with the potential to improve human health. Thanks to very good physico-mechanical and barrier properties polymers became very popular in food industry as a packaging materials. Wild range of fermented dairy products could be packed in this packaging materials according to their?s inertness as well. Functional milk beverage was obtained from milk with 0,9% milk fat content by applying 10% v/v of kombucha?s inoculum cultivated on a black tea sweetened with sucrose. The beverage was packed in a different packaging materials: polyamid-polyethylen (PA/PE) coextruded foil bags and polyprophylen (PP) cups closed with aluminium (Al) foil lids under atmospheric conditions (ATM). Beverages were storaged for 15 days at 4?C. The quality of kombucha inoculum, milk and obtained kombucha fermented milk beverage were analysed. Characterization of the packaging materials was done by investigating physico-mechanical, barrier and structural properties. The composition and changes in the headspace atmosphere, after production and during the storage, were analysed. The influence of packaging material properties and packaging conditions on the biochemical transformations of the milk?s components (the content of: lactose, L-lactic acid, D-galactose, ethanol, B1 and B2 vitamins) influenced by kombucha starter were analysed as well. On the bases of the obtained results of characterisation of packaging materials, it can be concluded that PA/PE and PP materials are proper to be used for analysed beverage?s packaging. Also, there is no significant difference in content of components which were quantified, between analysed materials in correlation with the packed fermented milk beverage.


2018 ◽  
Vol 25 (6) ◽  
pp. 1167-1176 ◽  
Author(s):  
Nahit Oztoprak ◽  
Mehmet Deniz Gunes ◽  
Metin Tanoglu ◽  
Engin Aktas ◽  
Oguz Ozgur Egilmez ◽  
...  

AbstractComposite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance.


2014 ◽  
Vol 67 (1) ◽  
pp. 6 ◽  
Author(s):  
Xiaoqing Zhang

Processing wheat gluten-based renewable and biodegradable polymer materials through chemical modifications has been demonstrated as an effective way to improve the mechanical strength and modulus, material flexibility, barrier properties, and thermal processability, and to introduce new functionalities. Challenges still remain in further enhancing material properties, balancing hydrophilicity/hydrophobicity and biodegradability in the material, achieving a designed performance, and maintaining the material sustainability. A good understanding of protein structures, reactivity, and functionalities of wheat gluten is fundamental for such research and development, and a close collaboration between bio-chemists, polymer chemists, and material scientists is necessary for the approach.


2019 ◽  
Vol 48 (11) ◽  
pp. 7573-7584 ◽  
Author(s):  
Terho Kutilainen ◽  
Marko Pudas ◽  
Mark A. Ashworth ◽  
Tero Lehto ◽  
Liang Wu ◽  
...  

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