Entry/Backup boards development history

　　PCB entry/backup boards were born almost at the same time as PCB in the 1940s and 1950s.At the beginning, the phenolic resin cover plate was used, and the common phenolic resin Tg is low, gradually appear drilling dirt and other problems .For this reason, in the PCB industry once began to use epoxy glass fiber plate, but it cannot completely solve the problem of drilling pollution, and because the drilling speed is higher and higher, the heat is more and more, in the late 80s to cover and thermal conductivity, and low, not cooling, so the requirements, cannot meet the production of the cost is higher, so the epoxy glass fiber plate use history is not very long, is abandoned.

　　In the early 1990s, wood fiber board began to be used as drilling pad due to the advantages of cheap price, stability, less drilling pollution and relatively good heat resistance. The early surface hardness, suitable for the size of drilling holes, in the late 1990s, the surface smoothness and thickness uniformity in recent years. At the same time in the early 1990s also appeared corrugated pad and other new concept products.

　　In the middle and late 1990s, the selection of cover / pad plate varieties used in PCB drilling processing also began to use another kind of varieties with better thermal conductivity, namely the metal cover plate. At first, ordinary soft aluminum is used, aluminum thermal conductivity is much greater than the resin, the highest temperature of the drill bit can be reduced from 200℃ to more than 100℃, but its material is too soft, easy to produce scratches, resulting in the drill skid and poor hole accuracy, broken needle and other abnormal. As a result, its better processing performance of the alternative alloy aluminum cover plate appeared, and has become one of the commonly used cover / pad varieties.

　　At the beginning of the 21st century, in order to adapt to the quality requirements of smaller aperture (below 0.3mm) and higher speed drilling holes, the cover pad manufacturer developed and improved the original phenolic resin pad products, and its material characteristics, density, surface hardness, flatness, thickness uniformity and material have been improved. At the same time, in order to solve the problem of alloy aluminum cover plate surface is too hard, and easy to cause drill bit skid, lubricating aluminum sheet is developed. This aluminum sheet also plays an important role in improving the accuracy of hole position and solving the heat dissipation problem of drill bit in drill bit processing. In recent years, the application market of lubricating aluminum sheet has been rapidly expanded, and it can be predicted that in the coming years, it is one of the ideal auxiliary materials in the micro hole drilling process.

　　With the development of high-end, functional and special PCB technology, as the PCB drilling auxiliary material cover / pad technology is also gradually developing towards diversification, refinement and function. The quality and variety of the cover / pad plate play an important role in ensuring the processing quality, yield, production efficiency, extending the service life of the drill bit and the reliability of the PCB.

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