**Abstract**

Micromachining has emerged as a foundational technology in modern electronics, playing a crucial role in the creation of miniaturized and high-performance devices. Its significance is particularly pronounced in the domains of high-frequency RF devices and Terahertz communication, where the demand for precision, miniaturization, and performance enhancement is of utmost importance. The requirement of linear tolerances are of the order of 1–5 μm, surface toughness of 40–50 nm Ra and flatness of 0.3 μm.

**Keywords:** micromachining, tool based micromachining, electromechanical, terahertz (THz), waveguides

### **1. Introduction**

The development of micro and nanotechnology has taken place due to the rising demand for micro and miniature parts and systems. The process used to fabricate MEMS and other microelectronics products can be called MEMS micro-manufacturing or lithography-based micro and nanomanufacturing. The technologies like photolithography, chemical etching, plating, and LIGA are called micro-manufacturing technologies. Micro manufacturing is generally employed to realize parts or feature sizes ranging from tens or hundreds of micrometers. Although micro manufacturing may not be enough to produce the smallest feature size as would be possible using MEMS and NEMS. This technology is a bridging gap for macro and nanodomain of manufacturing. It has various advantages over lithography-based micro-manufacturing in terms of material choice, relative accuracy, and complexity of part geometry. Micromachining is a broad term that encompasses a variety of fabrication processes for the production of miniature parts and structures. Non-lithography-based micromachining processes, such as micro electrical discharge machining (micro EDM), micro-milling, laser cutting/patterning/drilling, micro-extrusion, micro embossing, micro stamping, and micro injection molding, are widely used in the electronics industry. These processes employ diverse working principles and exhibit unique characteristics in terms of achievable accuracy, surface finish, and production rate. However, they all share the ability to produce three-dimensional microparts from a variety of materials [1]. This chapter will focus on micro mechanical cutting processes, in which the geometry of the cutting tool is defined. The relative accuracy and feature size, which can be achieved in micro-manufacturing, is described by Chang et al. [2] identified he has established that micro and nano manufacturing technologies is one of the most significant emerging manufacturing processes to address the future challenges in high-value engineering. Micromachining is a fabrication process that can be used to create three-dimensional (3D) microparts from a variety of materials, including metals, alloys, polymers, composites, and ceramics. Micromachined parts can have dimensions as small as 10−3 to 10−5 meters (sub-micron accuracy). This is significantly higher than the accuracy achievable with MEMS-based processes, which typically have accuracies of 10−1 to 10−3 meters [1].

A micro-cutting (micro-milling) has attracted growing attention from researchers and industry in the last 2–3 decades because mechanical cutting is a well-established area. Knowledge of macro cutting has been adapted to study the micro-cutting phenomenon. Two research approaches are being investigated; one is the minimization of the conventional cutting process, tooling, and equipment, with an emphasis on their scaling down effect. Micro cutting is kinematically similar to conventional cutting but fundamentally different from it in many aspects. Micro cutting refers to the mechanical micromachining (direct removal of metal) using geometrically defined cutter edge(s) on a conventional precision machine or micro machine. The selection of production method in microelectronics depends upon the number of replications and the degree of accuracy desired. Most of the production methods used nowadays are lithography based which are a combination of photolithography, etching and electrodeposition, and require costly setups and large volumes. The geometries obtained by these lithography-based processes are limited to 2½D microstructures with high aspect ratios and accuracies. Mechanical and thermal methods provide a viable solution for higher material removal rate during electronics manufacturing process. Such processes allow manufacturing of complex 3D shapes with acceptable aspect ratios, Bissacco et al. [3]. CNCmicro milling offers to process a wide range of materials at low set up costs. A large knowledge database and infrastructure developed for macro milling can be utilized for stepping into micro zone. Mechanical micromachining, particularly micromilling, offers several advantages over other manufacturing processes for electronics manufacturing due to its versatility, accuracy, and surface quality. Micromilling can be used to machine a wide variety of materials, generate complex 3D geometries with minimal setups, and produce parts with high accuracy and surface quality. However, micromilling also faces a number of challenges, including the size effect, rapid tool wear, inherent burr formation, low tool stiffness, and limitations on the minimum feature size and surface roughness compared to lithographic techniques [1]. The machining of micro molds require very high level of geometrical tolerances and surface quality this makes the application of micro end milling very challenging Aramcharoen et al., and Vázquez et al. [4, 5]. The generated topography of the micro milled surface is mainly influenced by the tool, machining parameters and cutting strategy. Micromachining enables miniaturization and integration of high-frequency RF devices and Terahertz communication, where size reduction is critical for efficient signal propagation Sankar et al. [6]. It also achieves precision fabrication of High-Frequency devices such as antennas, filters, and resonators which ensures optimal electromagnetic performance. The tight tolerances and fine features achievable with micromilling contribute to minimizing signal losses and maintaining the required device characteristics Kunieda et al. [7]. It also enables to tailor the shape and dimensions of resonators, waveguides, and other elements enables precise tuning of their electromagnetic properties, leading to enhanced device performance Mekonnen [8].

#### *Micromachining and Its Applications for Electronics DOI: http://dx.doi.org/10.5772/intechopen.113892*

Micro cutting is kinematically similar to conventional cutting, but fundamentally different in many aspects [2]. Micro cutting refers to mechanical micromachining (direct removal of metal) using geometrically defined cutting edge (s) carried out on a conventional precision machines or micro machines. Aramcharoen et al. [4], Jain [9] has achieved and described stringent tolerances using tool based micro cutting. Wu et al. [10], Paulo et al. [11], Aramcharoen et al. [4] have described the size effect in micro milling the uncut chip thickness (UCT) is of the scale of cutting-edge radius or the tool nose radius. Based on the size effect Jun et al. [12] explained the elasticplastic stage, which occurs due to plowing, which most of the workpiece material accumulates and expands ahead of the cutting edge. Relatively large burr formation occurs as a result of inhomogeneous distribution of material flows causing high surface roughness that decreases the material removal rate. Liu et al. [13] and Weule et al. [14] have given the material removal mechanism. In micro end-milling, the thickness initially increases from zero to a maximum value approximately equal to feed per tooth. After that it reduces from feed per tooth to zero. Whereas in the case of side milling, the thickness reduces from maximum to zero. This stage may occur repeatedly for a single point cutting edge, or in most common scenarios, simultaneously for multiple cutting edges depending upon the employed tool geometries, and the cutting parameters. Malekian et al. [15] predicted the minimum uncut chip thickness MUCT for Aluminum alloy (Al6061). Chae et al. [16], Sun and Cheng [17] and Chen et al. [18] discussed the importance of tool geometry and its effect on micro milling. Klocke et al. [19] studied the microstructure of cutting tool and suggested alloying effect on strength. Cheng et al. [20] studied the effect of cutting tool and emphasized the tool nose radius, rake and relief angle. Chen et al., Boswell et al., Yang et al. [21–23] described the importance of minimum quantity lubrication (MQL) for different materials based on experimental studies. In micromilling, the cutting forces are significantly influenced by factors that are typically negligible in conventional milling, such as tool wear, tool run-out, and chatteras described by Gietzelt and Eichhorn [24]. Tool run- out is more in micro milling due the low rigidity of the tool and higher cutting speeds, which leads to deteriorated surface [17]. Therefore to maintain tighter tolerances, reduce cutting force, maintain constant chip load, and avoid premature tool failure in micro scale milling, the cutting paths and machining strategies should be optimized [25, 26].

According to Griffin et al. [27] in the sub-millimeter or THz frequency range, the skin depth of the oscillating electric field in a metal is typically very small. This means that the electric field is only able to penetrate a very short distance into the metal. If there are defects or non-uniformities on the surface of the metal, these can act as additional resistance to the electrons. This is because the electrons must flow around the defects or non-uniformities, which takes longer and uses more energy. As a result, surface roughness is one of the most important factors affecting the performance of metal waveguides at sub-millimeter or THz frequencies. Surface roughness can cause signal losses and distortions. This is especially important in small waveguides, where the skin depth is even smaller and the effects of surface roughness are more pronounced. As per Narayanan et al. [28], the split-block technique is a conventional machining process that can be used to fabricate receiver components for the submillimeter and low terahertz frequencies. It involves machining the circuit structures on two (or more) metal blocks and then mating the blocks together to form the complete component. The split-block technique offers a number of advantages over other fabrication methods. First, it is relatively straightforward to implement. Second, it allows for the easy placement of circuit components such as RF chokes, diodes, and coupling

structures on the split blocks prior to assembly. Zhang et al. [29], suggested strategies for reducing vibrations during micro milling. Quintana and Ciurana [30] presented chatter minimization strategies for suppression of chatter to get better surface finish. Researchers [31–35] discussed burr formation in details along with their location of occurrence. Strategies for minimization of burr formation were also discussed. Machine tool construction for micro machining and error sources were discussed by Lamikiz et al. [36] and Hashmi et al. [37] especially the Abbe's error and correction methods along with isolation from external vibration beds because of its very low thermal expansion coefficient of 6.5 μm/mK, 2.5 times less than the one of mineral casting. Additionally, granite with a density of 2.8 kg/dm3 is beneficial. According to Uriarte et al. [38] we are using small tools; the spindle must rotate at high revolutions (<30,000 rev/min) to achieve the adequate cutting speed for most materials. Apart from the speed, the spindle must be stiff (>25 N/μm) and must present a small run out (<1 μm) to ensure high precision in the cutting process.
