避熱式旋轉放電法於針尖1-μm之單晶鑽石探針高效成形研究

Abstract

本研究旨在針對「針尖圓弧半徑1 µm」的單晶鑽石探針，進行快速研磨成形研究。為獲得高效能的單晶鑽石探針之成形加工，研究提出一種「避熱式旋轉放電法(Heat-prevented rotation wire electrical discharge machining, Heat-prevented RWEDM)」，透由避熱路徑演算法，計算出銅線放電加工的最佳路徑，以便對真空焊接(Vacuum brazing)完成的含硼單晶鑽石(Boron-doped monocrystalline diamond, BD-MCD)進行旋轉式放電。高溫火花熔蝕可無視於鑽石的硬度，探針能被快速旋轉熔蝕至針尖10 µm的雛形，除了可移除鑽石與基材的大部分材料外，更可避免鑽石因高熱而脫離母材，著實能大幅減少後續的研磨加工時間。高溫亦可使探針表面由sp3的鑽石結構降至sp2的石墨化層結構，有利於後續研磨過程中的潤滑。完成的鑽石探針雛型，續以陶瓷結合劑鑽石磨輪進行切線式的粗加工、精加工研光及拋光。實驗發現，於研磨的最終階段，添加#14,000超微磨粒，並以進給深度0.1 µm/stroke進行精拋光，可使鑽石探針針尖半徑達1.0 µm，表面粗糙度達Ra86 nm，全程耗時僅2小時36分鐘。比起傳統僅以研磨方式成形，效率提高54%。最後由表面粗糙度量測儀對成形的鑽石探針進行量測驗證，證實本製品的量測結果能達JIS 2001規範的標準差範圍，顯示本研究所開發的單晶鑽石探針能應用於商用的表面粗糙度量測儀的量測，研究所提方法具「技術自主」及「商業化」價值。This study presents the development of a high-performance hybrid process technique for making an industrial monocrystalline diamond (MCD) probe with 1-μm tip-radius. To realize high-performance formation of MCD probe, a heat-prevented rotation wire electrical discharge machining (RWEDM), by which an optimum CNC path of wire-cutting is schemed via the designed heat-prevent algorithm, is proposed to swiftly erode the boron-doped monocrystalline diamond (BD-MCD) in this study. Regardless of the hardness of workpiece, the diamond probe prototype with 10-μm at tip-radius can be speedily formed by the high-energy spark of temperature. The diamond blank separated from the substrate due to an unduly high discharge heat would not has happened. Besides which, it can remove most of material decreasing substantially the time of consequent grinding process. The high-temperature of spark erosion greatly facilitates the SP3 diamond bond structure into SP2 graphite structure, which is helpful in the effect of lubrication during grinding process. Tangential lapping and polishing are conducted, respectively by a vitrified bond diamond grinding wheel after the diamond probe prototype formed. Experimental results show that the monocrystalline diamond (MCD) probe with 1-μm tip-radius and surface roughness of Ra86 nm can be achieved when combining the grinding depth of 0.1 µm/stroke with ultra-fine abrasives of #14,000. It also demonstrates that total processing time is only 2 hours and 36 minutes, which the machining efficiency has evidently increased by 54% compared with that only using conventional grinding method. The finished diamond probe has been confirmed by a commercial surface roughness measuring instrument and proved that the range of errors fully fall into the JIS 2001 standard. It indicates that the developed monocrystalline diamond probe can been employed as a commercial probe for servicing in the surface roughness measuring. It is expected that the hybrid process technique will significantly contribute to the high-precision industry and to future micro fabrication techniques.