Modeling of Micropores Drilling Force for Printed Circuit Board Micro-holes Based on Energy Method

The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole processing.The problem of optimal control of its drilling force is one of the main factors affecting the quality of micro-hole machining.To address this problem,the thrust forces and torques in PCB drilling were first modeled and analyzed,and the corresponding prediction models were established.The drilling force analysis was carried out through the micro-hole drilling experiment,the specific cutting energy under different feed rates was calculated,the influence of the size effect was clarified,and the accuracy of the prediction model was verified.The result shows that during the drilling of glass fiber cloth,changes in the material removal mechanism are induced as the feed per revolution is varied.When the feed per revolution is less than the tool edge radius,the glass fiber is not cut by the main cutting edge,but is crushed and broken.When the feed per revolution is greater than the radius of the tool edge,the glass fiber is cut by the main cutting edge.At the same time,the established analytical model can accurately reflect the influence of the size effect on the drilling torque in PCB micro-hole drilling,and the error is within 10%.This method has certain practical application value in controlling PCB micro hole processing quality.

Fabrication of Through Micro-hole Arrays in Silicon Using Femtosecond Laser Irradiation and Selective Chemical Etching

We demonstrate a method of fabricating through micro-holes and micro-hole arrays in silicon using femtosecond laser irradiation and selective chemical etching. The micro-hole formation mechanism is identified as the chemical reaction of the femtosecond laser-induced structure change zone and hydrofluoric acid solution. The morphologies of the through micro-holes and micro-hole arrays are characterized by using scanning electronic microscopy, The effects of the pulse number on the depth and diameter of the holes are investigated. Honeycomb arrays of through micro-holes fabricated at different laser powers and pulse numbers are demonstrated.

A Novel Micro-hole Electrode Used to Investigate Electron Transfer Reactions at ITIES

A novel micro-hole electrode was fabricated to investigate the electron transfer reaction at the interface between two immiscible electrolyte solutions (ITIES). The electron transfer reaction between ferro/ferricyanide in aqueous phase (W) and ferrocene in 1, 2-dichloroethane (O) phase was studied as a test experiment. The results showed that the diffusion coefficient obtained from the micro-hole electrode was consistent with that obtained at macro-interface. Due to its simplicity and the very small IR drop it will be a useful tool for the study of ITIES systems.

Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5 μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R-C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

Improving surface integrity of micro-holes in ECDM using ultrahigh-speed rotary of tool cathode and non-water-based electrolyte

The surface integrity of metal micro-hole structures produced by electrochemical discharge machining is unsatisfactory owing to the insufficient reaction area and strength of electrolysis action.A novel ultrahigh-speed Rotary Electrochemical Discharge Machining(R-ECDM)using non-water-based electrolyte is proposed to improve surface integrity by changing the breakdown medium of spark discharge and increasing the reaction area and strength of electrolysis.A mathematical model was developed to establish the relationship between rotational speed and forces acting on the bubble.Based on the magnitude of forces,controlling rotational speed changed the behavior and departure radius of bubbles on the cathode surface.High-speed photographs validate that,in the mathematical model,the number and departure radius of bubbles on the cathode surface gradually decrease with the increase of rotational speed.The experimental results show that the roughness(Ra)of the micro-hole sidewall decreases from 2.54μm to 0.20μm when the rotational speed increases from 500 r/min to 40000 r/min.The length loss and wear ratio of the cathode are only 9.75μm and 6.5%,respectively.Finally,the micro-holes array with recast-free and surface roughness of 0.20μm is fabricated,demonstrating that the proposed approach contributes to improving surface integrity of metal micro-holes.

Influence of longitudinal-torsional ultrasonic-assisted vibration on micro-hole drilling Ti-6Al-4V

As Ti-6 Al-4 V is a typical hard to machine material,especially in micro drilling aviation parts,chip breaking difficulty is of increasing interest to explore its further development.In this study,Longitudinal-Torsional Ultrasonic Assisted Drilling(LTUAD)was employed to machine Ti-6 Al-4 V,and its feasibility was evaluated by comparing with Conventional Drilling(CD).By combining periodical characteristics and vibration models(the separated or the unseparated ultrasonic elliptical vibration),the influence of ultrasonic frequency on the intersection characteristics of trajectories were analyzed.And the intersection characteristics were divided into four categories:even periodicity,odd periodicity,non-odd and even periodicity and composite periodicity,indicating different capability for chip breaking.By applying the longitudinal-torsional compound vibration horn,the micro-hole drilling experiment was carried out on machining center.The chip morphology,the thrust force,and the burr height were discussed.Experimental results showed that the morphology of chips presented as smaller and more fragmentary ones in LTUAD compared with continuous helical conical ones and fold-shaped ones in CD.Compared with CD,the average values of the thrust force in LTUAD reduced by 1.98%to 24.9%.According to the burr around the hole exit in both LTUAD and CD,the height of the latter was greatly affected by the drilling parameters.And the burr around the exit of the hole were distributed rather evenly with smaller extension in LTUAD.Consequently,the LTUAD employed in micro-hole drilling was effective.

基于不同加工工艺的微孔节流空气静压轴承的特性研究

随着超精密加工技术和地面微低重力仿真的发展,相关产业对空气静压轴承的性能要求越来越高。由于传统的孔式节流器其结构特点不能完全满足实际使用的需要,节流孔直径与气膜间隙同一数量级的微孔节流空气静压轴承因其良好的刚度和承载特性,越来越受到关注。但在微孔节流器的发展过程中,微孔的加工工艺却限制了其推广应用。针对目前常用的三类微孔加工工艺,进行了理论仿真研究,通过建立不同加工工艺轴承仿真模型,运用双向流固耦合仿真方法,对比分析了基于不同加工工艺的微孔节流空气静压轴承的动静态特性。研究结果表明:锥孔类轴承承载性能优于其他两类,但耗气量大且在小间隙时刚度较差;薄壁直孔类轴承承载性能稍逊,但在大间隙下轴承刚度较佳;嵌套类轴承承载性能较差,但在小间隙下轴承刚度较大且耗气量较低。

聚合物真空绝缘子表面二级微结构

为研究绝缘子表面二级微结构的耐压提升机制,将表面二级微结构拆分为两种子结构,也即是表面微孔结构与表面微槽结构,并通过复合材料制备、激光处理、酸液选择性腐蚀等方式制备出表面二级微结构与相应的两种子结构。对三种结构分别进行沿面耐压性能测试,结果表明表面微孔与表面微槽均能有效地提升绝缘子的真空沿面耐压性能,而二者组合形成的表面二级微结构能够进一步提升绝缘子的真空沿面耐压性能。该结果表明通过将表面结构进行合理的组合能够实现对绝缘子表面闪络发展的多重、协同抑制,进一步提升绝缘子的真空沿面耐压水平。

微弧氧化处理对6061铝合金电偶腐蚀防护

目的提高船舶上铝合金的耐蚀性能。方法使用双极性脉冲电源对6061铝合金进行微弧氧化处理,并使用环氧树脂进行封孔,通过电化学测试、扫描电子显微镜(SEM)、能谱仪(EDS)、浸泡腐蚀试验和电偶腐蚀试验等方法,对膜层的表面形貌、截面形貌、物相组成和耐蚀性能进行测试。结果制备的6061铝合金微弧氧化膜层厚度约为40μm,致密均匀。在240h浸泡试验后,仍具有较强的耐蚀性,与316L不锈钢耦合的电流密度从约47μA/cm^(2)下降到20μA/cm^(2)左右,对6061铝合金的耐蚀性有显著提升。封孔处理后,浸泡腐蚀240h,未发现明显腐蚀,电偶电流进一步下降到11μA/cm^(2)。结论对6061铝合金进行微弧氧化处理,可以有效提高其耐蚀性能,对电偶腐蚀有较好的抑制作用,封孔处理则可以进一步提高铝合金的耐蚀性能。

超疏水微结构表面的制备工艺研究

针对装备表面大面积采用超疏水结构以实现减阻、防污的需求,考虑加工低成本、可重复及高效的目标,采用PDMS模塑工艺来实现超疏水微结构的制备,基于高速微小孔钻削工艺在铝合金表面加工阵列微孔结构作为PDMS浇铸的模具,成功在PDMS膜表面复印出阵列微柱结构,对制备的超疏水微结构PDMS膜进行了加工误差分析,误差为6%。

基于Micro CT的铜导线短路熔痕孔洞特征分析

导线短路是造成电气火灾的重要原因之一。现行国家标准中将导线短路熔痕分为起火前发生的一次短路熔痕和起火后造成的二次短路熔痕,然而现行国家标准中的鉴定仅停留在定性判断的阶段。火灾现场铜导线短路熔痕特征的量化分析研究是国内外研究人员主要关注的重点。本文应用Micro CT技术对铜导线短路熔痕进行断层扫描检测并重构铜导线短路熔痕的3D图像数据,在此基础上统计、归纳、总结铜导线短路熔痕内部孔洞形态及分布等孔洞特征。研究表明,Micro CT能够全面采集铜导线短路熔痕的整体形态和内部孔洞特征,一次短路熔痕与二次短路熔痕内部孔洞半径、表面积、紧密度的特征数据存在差别,可为短路熔痕定性和定量分析判据研究提供新的理论依据。

微通道搅拌优化空穴注入用PEDOT:PSS制备及材料表征

改进了聚(3,4-乙烯基二氧噻吩)/聚(苯乙烯磺酸盐)(PEDOT:PSS)的合成技术。采用对甲苯磺酸铁[(Fe(OTs)_(3))]作为催化剂,并在反应中引入磷酸三乙酯作为水溶性助剂并辅助催化反应且消泡稳黏,以优化PEDOT:PSS的成膜性能。同时,利用微通道搅拌方法制备了均匀粒径(<50 nm)的OE-004 PEDOT:PSS分散液,然后将OE-004应用于器件表征以全面评估OE-004与Clevios P VP AI 4083的性能差异并验证其适用性。研究结果表明,OE-004材料因更均匀的粒径尺寸和优化的微观配比,在PM6:L8-BO器件中表现出与Clevios P VP AI 4083基本一致的优秀空穴传输性能,实现了17.72%的最佳光电转换效率。器件复合过程研究表明OE-004呈现出良好的空穴提取和传输能力,在抑制器件内部的单分子复合或陷阱辅助复合方面表现出色。这些结果清晰验证了OE-004在有机太阳能电池中的适用性,其优异性能为空穴用PEDOT:PSS提供了理想的国产产品。

采煤沉陷区立体化调查监测技术体系研究

采煤沉陷带来耕地受损、生态破坏和地灾隐患等一系列问题,开展采煤沉陷区调查监测,识别沉陷范围、预测沉陷边界、监测沉陷速率,有利于及时掌握沉陷地类、沉陷机理和稳沉状态,为耕地保护、生态修复及灾害防治等工作提供参考。本文通过合成孔径雷达干涉测量(Synthetic Aperture Radar Interferometry,InSAR)、微动勘探实测数据和沉陷区地层相近区域的地面沉降光纤孔监测数据研究皖北某煤矿沉陷区边界和采空区,结果表明:以10 mm为界线,利用InSAR可以快速划定沉降边界;通过微动勘探实测数据发现1000 m深度煤系地层的横波速度比正常地层低25~50 m/s,InSAR结果也显示该区域出现了地面沉降;分析收集到相近区域12组光纤孔监测数据,77.7~200 m深度段地层为主要变形区域,压缩量约为163.77 mm,数据频率能达到分钟级。由此可见,基于InSAR、微动和光纤孔监测三种方法实现多源异构数据耦合,能够在“高潜水位、中厚煤层、千米以深”的采煤沉陷区达到“由表、及里、实时”的立体化调查监测效果,构建立体化调查监测技术体系存在可行性。

镍基高温合金喷油孔的飞秒激光精密加工

飞秒激光平面螺旋钻孔策略在灵活性、精度和工艺效率方面具有许多优势,可满足某型号航天发动机供油喷嘴直通孔的加工精度需求。因此,本研究采用飞秒激光平面螺旋钻孔方式,系统研究了激光功率、单层进给量、单层扫描时间、离焦量以及脉冲重复率之间的作用关系及对钻孔质量的影响。结果表明,离焦量对入口孔径的影响最为明显;对出口孔径和锥度影响较大的参数为功率以及进给量;对加工效率影响最大的参数为功率。根据上述影响规律进行调整,本实验成功在厚度为1.5 mm的GH3044板材上制备出孔径为390μm的通孔,出口入口孔径误差小于0.6μm、锥度小于0.5°。通过统计不同参数下微孔内壁粗糙度变化规律并以此对参数进行调整,有效地将孔壁粗糙度降低至Sa 0.6μm,满足工艺要求。孔壁形貌分析表明钻孔质量优良,随激光脉冲重复频率增加,孔壁附近组织逐渐粗化,但均无明显重铸层或热影响区,能够实现高精度微孔的相对“冷加工”。本研究为后续追求高雾化效果的异形孔的制备提供了理论依据。

电化学对微小孔毛刺去除的仿真及试验

钻削微小通孔产生的孔口毛刺严重影响了其表面质量,且微小孔因直径小导致其入口和出口毛刺去除困难,为此提出基于电化学的微小通孔双面毛刺的同步去除方法。以0.35 mm厚的304不锈钢板的钻孔毛刺为研究对象,建立电化学毛刺去除仿真模型,分析电流密度与微小孔不同区域材料去除速率间的对应关系,研究电极位置及工艺参数对毛刺去除效果的影响,并开展相关试验研究。结果表明,孔口表面电流密度大小表征了材料去除能力的强弱,毛刺尖端电流密度大,孔内壁电流密度小且分布均匀;电极位置对出口毛刺去除速率影响大,伸出型电极毛刺去除效果最好;随加工电压、电解质浓度及电极直径增大,毛刺去除效率增高,但扩孔率增大,且电极直径越大入口倒角越明显;试验基于伸出型电极位置,采用4 V加工电压、12%NaNO_(3)电解质、0.2 mm电极半径,实现了孔口毛刺的精准去除,加工后的倒角宽度为38μm,扩孔率仅1.99%,验证了仿真的准确性。研究结果可为微小通孔双面毛刺的高效、精准去除奠定研究基础。

微孔节流气体静压止推轴承跨缝过程时变特性研究

目前,大型气浮平台均采用花岗岩平台拼接而成,平台拼缝会对实验效果产生一定影响。针对上述问题,以微孔节流气体静压轴承运动中经过平台拼缝时的时变特性为研究对象,建立微孔节流止推轴承物理模型,并使用CFD软件与UDF相结合的动网格技术实现轴承跨越平台拼缝的动态过程仿真,研究不同气膜厚度、进气口压力、平台拼缝位置对轴承承载力和压力分布的影响。结果表明:当平台拼缝到达微孔分布圆附近时承载力急速下降,且平台拼缝到达轴承中心时承载力下降到最小值;随着气膜厚度的增加,轴承承载力的最大损失比例随之增加,并最终稳定到0.6;平台拼缝位于供气孔分布圆之外时,轴承边缘与平台拼缝之间的承载面将失效;通过增加进气口压力,轴承承载力整体有明显提升,但承载力损失速度也明显加快。

镍基单晶高温合金表面微阵列孔的制备方法及其实验研究

微小孔结构在航空航天、现代医疗、精密仪器等领域有着广泛的应用,但孔径尺寸微小且加工精度要求高,常规的接触式机械加工方式存在切削力致使孔精度较难控制.而电火花加工非接触和无宏观切削力的特点使其在微小孔加工中具有独特的优势.开展镍基单晶高温合金表面微阵列孔制备的实验研究,首先通过低速走丝电火花线切割方法结合精修工艺实现了边长小于340μm菱形微细阵列电极的高精度制备.采用所制备的微细阵列电极在镍基单晶高温合金表面进行微阵列孔加工,探究微阵列孔尺寸的一致性精度、孔壁的表面质量和电极损耗特点,揭示抬刀速度和抬刀模式对微阵列孔的孔壁粗糙度的影响规律,实现了镍基单晶高温合金表面微阵列孔的高效率高精度制备.

C/SiC复合材料微孔的电镀金刚石钻头钻削加工

用金刚石基本颗粒尺寸分别为20~30,36~54和63~75μm,直径在0.280~0.440 mm范围的6种电镀金刚石钻头,钻削三维针刺毡基C/SiC复合材料微孔,测试6种钻头的最佳加工工艺参数,分析工艺参数及金刚石基本颗粒尺寸、钻头直径等对微孔加工质量、加工效率的影响。结果表明:在相同钻削速度条件下,进给速度越低时,加工的微孔质量越好;钻头电镀的金刚石磨粒基本颗粒尺寸越大,其钻削效率越高;在6种钻头中,直径为0.300 mm的基体上电镀63~75μm的磨粒,直径为0.200 mm的基体上电镀36~54μm的磨粒,能够获得更优的钻孔性能。

安全滤网阵列网孔激光-电解组合加工

安全滤网阵列网孔的高效、高品质和高适应性加工至今仍面临重大技术挑战。基于此,提出采用激光-电解组合加工技术制备安全滤网阵列网孔结构。介绍了激光-电解组合加工技术的试验加工系统,探究了工艺参数对微孔形貌质量和加工精度的影响规律,并开展了安全滤网阵列网孔的制备。试验结果表明:激光加工路径显著影响微孔出口的形貌,采用同心圆轨迹(外径270μm,内径230μm,线间距2.5μm)能够显著改善微孔出口的圆度;激光功率越大、切割速度越小,微孔直径及其热影响区均越来越大;NaNO3-乙二醇溶液作为电解抛光液能够在加工表面形成扩散层发生电解抛光,将激光加工产生的喷溅物和毛刺等缺陷去除;基于优化工艺参数,加工出253个直径0.31 mm的阵列网孔结构,出入口直径方差仅为2.02和1.71,展示出较高的尺寸一致性。激光-电解组合加工技术在薄壁件上高效、高品质制备阵列网孔结构方面具有很强工艺能力和发展潜力。

提高电火花微小孔加工质量的研究进展

电火花微小孔加工是电火花加工领域的一个重要方向。因其加工设备简单、加工精度高且无切削应力等优点,成为众多难切削材料微小孔加工中的最常用加工方法。传统电火花微小孔加工中存在加工碎屑排出困难,间隙短路,频繁抬刀及二次放电等问题。针对这些问题,本文在微小孔加工技术理论基础上,系统阐述了电极形状和电极运动方式的改进,以及电火花微小孔加工与其他技术复合的加工方式,包括磁场辅助、超声振动辅助、电解电火花复合微小孔加工,其中与其他技术复合是进一步提升电火花微小孔加工性能的有效方式,将是未来研究的重点之一。归纳了目前技术改进及复合加工技术中存在的问题。最后对电火花微小孔加工的发展趋势进行了展望。