Микроконтроллеры

Dow Corning Conformal Coatings from http://www.dowcorning.com/ ---------------------------------------- Conformal Coatings should ideally possess as many of the following characteristics as possible: * One-part product * Low viscosity * Spray, dip, select, or flow-coat application options * Long pot life * Rapid cure, no by-product * Sufficient under-component cure * Repairability * Wide range of operating temperatures * Non-toxic * Low cost * Robust adhesion ---------------------------------------- Acrylic Acrylic coatings are typically solvent based and are easily repaired. Traditionally they were low cost but have become less competitive with rising regulation requirements and safety concerns with solvent usage. They were tough, hard, and transparent - but lacked stress relieving capability. Pot life was good since additional solvent could be added to keep the bath viscosity low and they exhibited low moisture absorption and had short drying times when volatile solvents were used. Epoxy Epoxy coatings are very hard, usually opaque and are good at resisting the effects of moisture. They possess excellent chemical and abrasion resistance, but can cause stress on components during thermal extremes. Cure chemistries can sometimes require extra precaution for safe handling. Fluctuating temperatures can cause considerable drift in viscosities and difficulties in controlling cure times and coating thicknesses. Urethane Urethane coatings are tough, hard and exhibit excellent resistance to solvents. Along with excellent abrasion resistance and low moisture permeability, they offer good low temperature flexibility. Their use is often prevented by their limited high-temperature capability and lack of repairability. Paraxylylene Paraxylylene coatings are very uniform and yield excellent pin coverage. Their limitations include high cost, sensitivity to contaminants and the need for vacuum application technique. Silicone Silicone coatings range from elastoplastic (tough, abrasion-resistant) to soft, elastomeric (stress-relieving) materials. They possess the following characteristics: Heat cure or RTV cure Usefulness over a very wide temperature range Good moisture and humidity resistance Processing versatility Easy repairability Low toxicity ---------------------------------------- Dow Corning Conformal Coatings are supplied in three product families. Each group is balanced to combine as many of the ideal characteristics as possible but targeted for specific needs. One of the initial considerations in selecting a silicone conformal coating is the desired cured surface characteristic of the material. RTV Elastoplastic Coatings cure with tougher, more abrasion resistant properties. Due to their physical form, they are supplied in solvent with the newer versions being low VOC. These coatings can be cured at room temperature or, after a short time at ambient to evaporate the solvents, can be heat accelerated to speed processing. If stress relief is a primary need, Dow Corning also offers silicone conformal coatings that cure with a rubbery, elastomeric surface, RTV Elastomeric and Solventless Heat Cure Coatings. These materials are solventless with both room-temperature and heat-accelerated cures. RTV Elastomeric Coatings need moisture from the atmosphere to cure. The family of coatings is rapidly gaining popularity due to its environmentally friendly and solventless formulations, its rapid cure rates that can be dramatically accelerated by mild heat and its cost effectiveness. These elastomers, when cured, offer the optimum stress relief for components and interconnections in a variety of service environments. Solventless Heat Cure Coatings are designed for rapid processing at moderate temps (above 100C). They do require some heating in order to cure and offer long bath life at room temperature. Like the room temperature curing elastomers above, these products offer the optimum stress relief for components and interconnections in a variety of service environments. This product line also features coatings that are manufactured for controlled volatility. RTV Elastoplastic Coatings have firm, dry surfaces for better handling and abrasion resistance and like other RTV materials they need moisture from the atmosphere to cure. Their cure rates can be accelerated by mild heat being applied after the solvent has dried. They are supplied in solvent with low VOC versions available.