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Coating, Encapsulating, and Marking
Published in Fred W. Kear, Hybrid Assemblies and Multichip Modules, 2020
The physical properties of the conformal coating material should be studied to ensure that it will do the job properly. The coefficient of expansion of the material and its adhesive properties are both important in affecting total surface coating. Outgassing and degradation of the material over time are also important considerations. The role of the conformal coating material is to seal the surfaces of the hybrid assembly completely against the outside environment and to maintain this seal throughout the life of the product. In order to meet these objectives, the surface of the assembly must be clean and dry before the coating process begins. The coating material must be correctly formulated and applied. All materials do not exhibit the same properties and may not be suitable for specific applications. Some materials may need to be degassed in a vacuum chamber before application in order to minimize gas bubbles in the coating. Conformal coating materials harden by different methods such as ultraviolet curing, evaporation of volatile materials, and polymerization. Most of these curing methods are accelerated by the application of heat, which may also accelerate the outgassing of the material.
Experimental and numerical study of swirling subcooled flow boiling of water in a vertical annulus
Published in Experimental Heat Transfer, 2018
Sajjad Ahangar Zonouzi, Habibollah Safarzadeh, Habib Aminfar, Mousa Mohammadpourfard
To make swirling flow inside the annulus, a spiral fin is inserted inside the annulus. This spiral fin is made from a foil of 0.2 mm thick and width of 3.5 mm. This fin is twisted around the steel tube so that its thickness will be in direct contact with the steel tube from one side and in contact with the glass tube from other side as it is shown in Figure 3. Thus, the flow in the annuli will pass a curvy passage instead of a straight passage, and this will make a swirling flow in the annuli that will affect the hydrodynamics and heat transfer of the boiling flow inside the annuli. The pitch of the inserted spiral fin as it is depicted in Figure 4 is also 68 mm. We have also made the spiral fin electrically insulated by using an insulating coating spray with the commercial name of DCA that is a flexible, transparent, and unique modified silicone conformal coating specifically designed for the protection of electronic circuitry.
Risk-based safety and mission assurance: Approach and experiences in practice
Published in Quality Engineering, 2018
Jesse Leitner, Bhanu Sood, Eric Isaac, Jack Shue, Nancy Lindsey, Jeannette Plante
NASA’s supply chain consists of a wide variety of suppliers, some of whom have thrived over decades through NASA contracts or subcontracts and others who may have no prior involvement in aerospace at all. As a result, a project can establish a requirements baseline and levy that baseline on a prime contractor and their subcontractors and encounter throughout the project lifecycle suppliers who declare in advance that they cannot or will not be able to comply with one or more of those baseline requirements. This may also apply to the prime contractor. Waivers or similar records are used to capture these requests for requirements relief, and they should be vetted by a CRAE or appropriate commodity expert. These requests are then captured in a supplier risk-management database as well as a lesson learned. Examples include the following:Use of alternate and/or equivalent standards. The most typical examples are those used for printed circuit boards (PCBs), soldering, conformal coating and staking, and cable and wire harness manufacturingUse of a different electrical, electronic, and electromechanical (EEE) part quality and reliability grading system such as/883 versus Class BMaterials of a lower grade than minimum specificationsItems built to an unqualified or nonstandard process
Synthesis of Li1.3Al0.3Ti1.7(PO4)3-coated LiCoO2 cathode powder for all-solid-state lithium batteries
Published in Powder Metallurgy, 2023
Ki-Sun Nam, Kangsanin Kim, Kyungsun Kim, Jon-Won Lee, Ji-Woong Moon, Haejin Hwang
In the synthesis process proposed in this study, citric acid chelates various metal cations in the precursor solution, forming a metal citrate complex [25]. The chelate complex, consisting of metal ions attached to a large hydrocarbon chain, allows the homogeneous distribution of metal ions, such as Li, Al, Ti and P. Polyesterification occurs when a chelate complex is dried and calcined at high temperatures to form a polymer resin. The polymer resin in the precursor solution containing various metals provided a rigid and conformal coating layer on the surface of the pristine LCO particles. The organic residue in the polymer resin decomposed and was removed from the coating layer during calcination.