What Is a Micro Drill Bit?
Micro drill bits are very thin drill bits.
They are mainly used for fine processing of electronic parts, medical devices, jewelry, etc. Since extremely high precision is required, they are made of materials with high hardness and resistance to wear such as cemented carbide.
Micro drill bits also require very careful handling to avoid breaking or chipping of the cutting edge, since the cutting force is weak due to its very thin and sharp cutting edge. Appropriate machining conditions and coolant usage should be selected depending on the material used.
Applications of Micro Drill Bits
1. Semiconductor Manufacturing
Drilling of lead frames, drilling of amorphous silicon, drilling of capacitors, drilling of chip resistors, and drilling of electrolytic capacitors are some examples. Lead frames are metal frames used in semiconductor packages to secure semiconductor chips and connect them to external circuits.
2. Mechatronics
Examples include the drilling of small gears, gear tooth profile machining, drilling of micromirrors, and drilling of motor shafts. A micromirror is a very small mirror, which can detect optical signals and control the angle of reflection by using microscopic specular reflection.
3. Medical Device Manufacturing
Examples include the drilling of joints, needles, and catheters.
4. Automobile and Aircraft Parts Manufacturing
Examples include the drilling of cylinder blocks, drilling of turbine blades, and drilling of rotary encoders. A cylinder block is one of the main parts of an engine, which contains a cylinder with a moving piston inside and important parts such as a combustion chamber and valve mechanisms.
5. Jewelry Manufacturing
Jewelry manufacturing includes the drilling of holes for jewelry, the manufacture of gears for watches, and the processing of jewelry.
6. Optoelectronics
This includes the manufacture of LEDs, optical fiber, and optical lenses.
7. Electronics Component Manufacturing
Drilling of circuit boards, machining of lead frames, machining of connectors, etc.
Types of Micro Drill Bits
Micro drill bits can be classified by diameter, cutting edge shape (center-cut, 2-blade, 3-blade, etc.), number of blades, and material. Material classifications include the following:
1. Cemented Carbide
Cemented carbide is an alloy with main components such as tungsten carbide, and has very high hardness and wear resistance. Cemented carbide is generally used for the cutting edges of Micro drill bits. Micro drill bits made of cemented carbide are very precise and high-cutting components.
2. High-Speed Steel
High-speed steel is a material composed of iron and alloying elements such as molybdenum, chromium, and vanadium, and has excellent heat and wear resistance. HSS Micro drill bits have lower machining accuracy than cemented carbide, but it is relatively inexpensive and suitable for mass production.
3. Other Materials
Micro drill bits are sometimes made of other materials such as ceramics, polycrystalline diamond (PCD), and polycrystalline diamond (PCBN). These materials have very high hardness and heat resistance, and can provide superior machining performance compared to cemented carbide and HSS.
HSS is an abbreviation for high-speed steel, a type of steel mainly used for metalworking tools and cutting tools.
Principle of Micro Drill Bits
Micro drill bits drill holes through the following processes:
1. Chip Generation
When a micro drill bit contacts a material, the cutting edge rotates while cutting away the material. The removed material is generated as chips.
2. Chip Ejection
Chips are ejected through the spiral grooves of the micro drill bit. These spiral grooves provide space for chip collection.
3. Hole Formation
A hole is gradually formed as the micro drill bit rotates to cut the material and ejects the chips. Hole shape and machining accuracy can be adjusted by adjusting the cutting speed and feed rate.
Other Information on Micro Drill Bits
1. Machining Accuracy
Micro drill bits can achieve extremely high machining accuracy by using very hard materials such as cemented carbide and diamond. A wide variety of materials can be processed, from metals such as iron and stainless steel to non-metallic materials such as ceramics and glass.
The cemented carbides and diamonds used in micro drill bits are extremely hard and resistant to wear and deformation, so they can maintain high machining accuracy for a long period of time.
Cemented carbide and diamond are materials with extremely high thermal conductivity. Therefore, heat at the cutting edge is efficiently dissipated, minimizing thermal effects during machining and preventing transformation and deterioration of the work material. In addition, its high corrosion resistance makes it less susceptible to chemical attack and rust, thus maintaining the quality of the workpiece.
2. Rigidity
Because micro drill bits are very thin, if the rigidity is low, the cutting edge may bend or vibrate, resulting in reduced machining accuracy. However, the rigidity of micro drill bits can be improved by using high-hardness materials such as cemented carbide or ceramics.
3. Compatible Materials
Micro drill bits can be used with several materials such as cemented carbide, high-speed steel, ceramics, PCD, and PCBN.
4. Use of Cutting Fluid
Micro drill bits are very thin, so the heat generated during cutting is concentrated on the cutting edge and may cause wear and deformation of the cutting edge. Cutting fluid has cooling and lubricating effects, and is also effective in removing cutting dust and cleaning surfaces.