Application of shape coating in humid environments - three performance factors that are easily overlooked.

In today's rapidly changing technology, especially the rapid development of high-voltage systems (such as 800V power modules) led by the new energy automobile industry, the electronics industry has put forward unprecedented high requirements for the protection performance of electronic components. Humidity, ion pollution, particle residue and other factors have become a major hidden danger affecting insulation performance, resulting in leakage and equipment damage. In order to improve the protective ability of electronic components, the industry generally uses Conformal coating technology (commonly known as three anti-paint). After the coating process, the electronic products are like wearing a layer of "invisible armor," which not only strengthens the ability to resist external infringement, but also promotes the reduction of conductor spacing in the circuit board design, so as to effectively maintain the stability of electrical insulation. The performance of the coating technology in wet environment is evaluated in many aspects, including dielectric constant, thermal properties, flammability, coating creep, chemical compatibility and chemical resistance. Through the insight of practical application scenarios, this paper extracts three performance evaluation indicators that are often ignored in wet environments, aiming to provide valuable reference information for industry peers to promote a more comprehensive and in-depth consideration of material properties. 1. Hydrolytic stability Hydrolytic stability is a measure of the ability of the coating to maintain its original physical and chemical properties in a humid environment. In high humidity environments (usually relative humidity greater than 60%), the coating may experience performance degradation if it does not have good hydrolysis stability. Submicron dust particles in the atmosphere may be acidic or alkaline. At humidity ≥80%, the thickness of the water layer can reach 10 molecules, at which time the material deposited in the atmosphere begins to dissolve, resulting in a free-flowing ion stream. These ions can penetrate the coating and cause circuit short circuit, corrosion and dendrite growth, which can lead to the failure of the entire electronic system. 2. Water vapor permeability Water vapor permeability refers to the ability of water vapor to be coated through the coating. Due to the small size of water molecules, almost all polymer substrates can penetrate, so all coating materials have a certain degree of water vapor permeability, but the penetration rate and degree are different. The chemical composition, thickness, degree of cure, and environmental factors such as temperature and humidity all affect the water vapor permeability of the coating. Although a certain degree of air permeability is conducive to the natural drying of the PCB in the non-working state, excessive penetration may increase the risk of leakage current, accelerate corrosion and reduce insulation performance. Therefore, when selecting the coating, it is necessary to balance its moisture-proof and breathability to ensure that it can effectively block moisture and does not affect the natural recovery and drying ability of the circuit board. 3. Ion penetrability Ion penetrability is a direct indicator to evaluate the defense ability of the coating against ionic contaminants, especially in the environment of contaminants such as flux residue and salt spray. Ions can enter the coating through the coating defects, micropores or directly through the molecular chain, leading to electrochemical reactions that lead to corrosion and insulation degradation. Surface insulation resistance (SIR) testing, sequential electrochemical reduction analysis (SERA), and diffusion cell measurement are widely used to test the resistance of coated coatings to ion penetration. The SIR Test directly assesses the resistance change at the substrate interface under the shape coating, the SERA test focuses on the oxidation state of the metal under the shape coating, and the diffusion cell experiment directly monitors the dynamics of specific contaminants through the shape coating by simulating the environment. The comprehensive application of these test methods shows that ions have penetration, and also provides scientific basis for the selection and improvement of the coating shape, to ensure that the selected coating shape can effectively prevent the penetration of harmful ions, and maintain the electrical safety of the circuit. In practical application, the selection of shape coating should consider the cost benefit, environmental adaptability and safety. In order to ensure the reliability and long-term stability of electronic devices in wet environments, the performance evaluation of the coating is particularly important. Users should be aware of the different assessment test methods and applicability of surface cleanliness, as well as advanced technical experience in the field of reliability and surface technology, such as the reliability of shape coatings. With cutting-edge instrumental analysis technology and rich experience in the field of process technology and reliability, ZESTRON R&S is able to conduct comprehensive and accurate characterization and evaluation of electronic product surfaces, providing customers with analytical services such as Coating reliability test CoRe test, Coating Layer Test, coating layer test, etc. Help customers solve complex reliability and surface technology problems.