Partially Devitrified Insulating Porcelain Enamel And Substrates Coated Therewith For Electronic Applications

Insulating porcelain-coated circuit substrates have been extensively applied for many fields, such as automobile, military, camera, aviation, and medicine etc. These substrates have many advantages, for example, cost-effective, highly reliable and mechanically strong. A few of developed countries have already manufactured circuit boards of high performances on a large scale. However, few researches deal with this work in China;especially the technology of good performance porcelain and substrates coated therewith has not been reported yet.The present study is intended to develop novel partially devitrified porcelain enamel and manufacture substrates coated therewith. This porcelain enamel do not intenerate at 300-400℃ and has good adherence with metal substrate. Its electric performances will meet require of circuit substrates. The main studies are described as follow:1. The experiments chose the porcelain enamel system of alkaline-earth metals ion according to foreign patent information and established series of porcelain enamel compositions which mainly based on barium oxide, magnesium oxide, silicon oxide, and boron oxide.2. Experiments have proved that melting porcelain has very strong causticity and low coefficient of thermal expansion. So, quartz crucibles are used to melt porcelains in high temperature electric furnace. Common low carbon steels are used as metal substrates. The surfaces of metal have been coated nickel in order to increase adherence between metal and porcelain.3. Frits are milled by wet method. Manual dipping and mechanical spraying coating methods are adopted on metal substrates.4. Sintering temperatures of a series of porcelain enamels are tested. Porcelain composition that accord with sintering technology is chosen. Under the oxidizing atmosphere condition, F129 porcelain enamel is experimented for sintering. A good sintering system is determined after comparing the sintering effects on coatings.5. Bulk resistance, breakdown voltage and dielectric properties of partially devitrified porcelain, and thickness, breakdown voltage of circuit substrates are tested.6. The grains of milled porcelain enamel and coatings are analyzed by scanning electric microscope. The grain distribution of porcelain enamelmilled one hour has been measured by laser grain instrument. The influences of different grain and coating methods for the coating surfaces are compared.7. The coefficient of thermal expansion(0-600°C) and softening temperature of F129 porcelain enamel are measured. Different thermal analysis and X-ray analysis for porcelains are used to find out devitrified temperature and crystals.8. The influences of coating methods for the thickness of coated enamel are analyzed;the influences of MgO content and temperature for bulk resistance are discussed;the breakdown voltages of common and insulating porcelain substrates are compared at different temperatures;the relations of between dielectric properties and frequency, temperature are discussed.