2020/05/08

HIT ceramic substrates machining introduction-Hantop Intelligence Tech.

Picture from HIT ultrasonic applications of ceramics crucibles 
 

Brief introduction of ceramic substrates

A ceramic substrate is a special process board where copper foil is directly bonded to the surface of an aluminum oxide (Al2O3) or aluminum nitride (AlN) ceramic substrate at high temperature. The manufactured ultra-thin composite substrate has excellent electrical insulation properties and high thermal conductivity. Therefore, the ceramic substrate has become the basic material of high-power electronic circuit structure technology.  The ceramic substrate has high mechanical strength. It can also be used as a supporting part in order to carry components, finished surface can be smooth and flat, which withstands low temperature and high humidity environment, furthermore, ceramic substrates can also be processed into various complex shapes.

 

The Definition of Technical Ceramic

Technical ceramic is also referred as precision ceramic and advanced ceramic. Technical ceramic can be classified with applications or the compositions of materials, such as technical ceramic and engineered ceramic, or silicate ceramic and oxide ceramic. Popular types of technical ceramic are alumina, zirconia, SiC and AIN. 

The differences between technical ceramic and traditional ceramic are derived from raw materials and manufacture process. Traditional ceramic is naturally-occurring and commonly combined with clay and quartz sands. With three main procedures, mixing, shaping and firing, traditional ceramic is often applied to artwork and furniture, such as bricks, tiles and pottery.  Technical ceramics were made by a totally different way. First, it requires to be highly purified inorganic compounds which are formed from finely divided powders. The forming procedure is also including mixture with organic binder to help consolidate the powder, so that it can shape more precisely. If dimensional spec is not needed to be precise, material can machine before sintering to prevent extreme hardness and brittleness.  

The second step is sintering, which means heating the blank in high temperature condition to strengthen its structures. Apparent shrinkage about 10-40% after sintering is a big problem when it comes to precision demands, the extreme hardness after sintering is also a challenge. Consequent procedures such as secondary machining and polishing are depends on the requirements of final workpiece.

To sum up, technical ceramic is highly purified powder and manufactures by multiple procedures to make sure it is strong enough to apply in harsh environment. We can think technical ceramic is a kind of upgrading product compared to traditional ceramic.

 

The Advantages of Technical Ceramic

Technical ceramic comes in excellent properties and makes it a suitable choice in various industries. For aerospace industries, selecting technical ceramic for engines and turbines parts due to its incredible wear resistance and high temperature.      

Excellent electrical properties are important in 3C electronics which assures hi-speed and stable transmission. Chemically inert and corrosion resistant are essential both in semiconductor and biomedicine industries. Since bio-inserts and relevant equipment have high standard demands of preventing infection and semiconductor industries contains chemical etching procedure which easily damage processing equipment.

 

Difficulties in Ceramic Machining

The processing of ceramic substrates follows the trend of minimizing parts and developing various functions to meet the market's demand for lightness and precision, and the difficulty of processing has also increased. The main processing methods of ceramic substrate micro-hole processing are laser processing and CNC processing. The main advantages of laser processing are high speed and high efficiency. Although the speed is fast, there are tapered holes (crack), and only low depth holes can be handled. Traditional CNC is good in shaping accuracy and surface roughness. However, the brittleness of the material results long processing time and the processing procedure may damage the contact area between the work piece and the tool, which may cause cracks or even largely shorten the tool life which ends up causing bigger overall cost.

 

Pros and Cons of Different Methods in Technical Ceramic Processing

1. CNC Milling/Grinding/Drilling
Most common way to process technical ceramic, and it is also suitable for various shapes and features without restrictions of thickness. Take equipment cost and versatility into consideration, conventional CNC is the most economist way.
However, because the hardness and brittleness of technical ceramic, so it is susceptible to micro-cracks, and improper cutting force and accumulated cutting heat also cause short tool life and low efficiency. 

2. Water-jet cutting 
Water-jet cutting method can apply to various materials with no limitations of thickness and hardness, and it is relatively user-friendly to manufacturers. 
The tolerance of water-jet cutting is about 0.03mm-0.05mm, which can be acceptable in many applications. Moreover, the principle of water-jet cutting is using high-pressured water column jetting straightly to objects, so that there’s no need to worry about thermal impact and chemical effect. Although it seems to be perfect in all aspects, water-jet cutting is hard to cut small piece materials and the expensive selling price might to too hard to invest. Water-jet cutting is popular in aerospace industries to cut composites currently due to precision demands, huge workpiece and the consideration of thermal impact.

3. Laser cutting
Laser cutting is a kind of non-contact machining without frictions in cutting. By high energy of laser spotlight heating the material to ultra-high temperature instantaneously, it can easily melt or even gasify the surface of materials. The principle of laser cutting is using instant-heating to penetrate materials, the problems of materials thickness can be a challenge. Generally speaking, the drilling availability of laser cutting in alumina and zirconia ceramic is about 0.5mm, it is the least depth than all kinds of machining methods. Despite tolerance of laser cutting (about 0.02mm) is more precise than water-jet and conventional CNC machining, we cannot ignore the carbonize surface of the material and extremely expensive price of laser cutting machine.

4. LS- Wire EDM
Low-Speed Wire cut EDM is commonly applied to extremely hard materials, thin-walled materials and hard to cut materials since it has low cutting force with high precision. The electrode wire moves in one direction at a low speed, the wire speed is generally lower than 0.2mm/s, the accuracy is 0.001mm, and the surface quality is close to the grinding level. According to the sophisticated machined performance, the shortage is apparent, either. Slow speed and special purpose machine will be a dilemma for manufacturers.

 

How Ultrasonic Ceramic Machining Works?

Despite Aluminum Oxide bears excellent mechanical properties,  the challenges in its hardness and brittleness have existed till nowadays. Crucibles also require special demands in smooth surface and various shaping.

In this case, HIT conducts ultrasonic-assisted machining on aluminum oxide with the HSK-A63 ultrasonic machining module.  The high-speed, high-frequency micro-vibration ultrasonic machining mechanism helps reduce the cutting force and makes the chip removal process easier.  With HIT Ultrasonic, the machining efficiency is greatly enhanced while maintaining great workpiece quality.
 

Ultrasonic Machining Applied in Semiconductor Ceramic Parts

High standard of surface quality is the basic in semiconductor industries because of the processing environment cannot withstand any pollution. The high cost per workpiece requires stable processing, and tool life is an important factor. Ultrasonic machining prolongs tool life, and it can both reduces tool costs and lower the surface roughness.
Ultrasonic micro-machining is commonly applied in semiconductor parts fabrication. The oscillation removes materials in each micro-oscillation and avoid improper cutting force from damaging workpiece. The vibrations also prevent cutting accumulation in micro-holes drilling and the coolant can flow to the processing area more easily.


 

What HIT Ultrasonic Machining Brings to Ceramic Machining

Ultrasonic Technology

Ultrasound technology is widely applied in diverse areas, from ultrasonic cleaner to food cutter. The whole process of ultrasonic machining has no thermal and chemical impact. With 20000-40000Hz high frequency ultrasonic vibration in Z-axis dimension, it can slightly remove materials from surface and prevent micro-cracks hard and brittle materials machining. Also, the amplitude of ultrasonic vibrations can effectively reduce cutting force and enable coolant directly drip to the tool edge, so that the tool life can be prolonged greatly.

 

Highlights of HIT Ultrasonic Machining

HIT ultrasonic machining adopts non-contact power transmission technology. The air gap between transmitter and toolholder doesn’t limit the high rotating speed of spindle which makes it more suitable for hard to cut material machining since high rotation speed can enlarges materials removal, enhance efficiency and quality. 
Plug and play module design is another highlight of HIT ultrasonic module. We can apply ultrasonic machining technique on various CNC machining by simply install our module on current CNC machine.  

Automatically tracking system can detect the slight tool wear or adapt to most of the tools and adjust to the suitable resonance, which can keep the ultrasonic processing more stable and easier to control by users.

HIT ultrasonic machining module has improved the efficiency by more than 3 times in past customer experiences. With high frequency, tool wear can be significantly reduced. In addition, the Z-axis vibration can effectively remove cutting chips in alumina drilling. Ultrasonic cutting instead of traditional continuous cutting makes the tip of the tool difficult to store heat and extend the life of the tool. HIT has aluminum oxide parts machining, alumina oxide crucible machining, and zirconia micro-drilling cases in the semiconductor applications.

 

2 Successful HIT Cases of Ultrasonic Ceramic Machining

1. HIT Ultrasonic Machining : Aluminum Oxide Deep Micro-Drilling

HIT conducted ultrasonic machining on aluminum oxide deep micro-drilling with the HSK-A63 ultrasonic machining module.  The tool life is improved over 5 times longer than that of the original, while maintaining good, consistent workpiece quality.
 

2. HIT Ultrasonic Machining : Aluminum Oxide Grinding

HIT conducted ultrasonic machining on aluminum oxide grinding with the HSK-A63 ultrasonic machining module.  The machining efficiency is enhanced by 83%, while maintaining good, consistent workpiece quality.

 

Ultrasonic Ceramic Machining FAQ

Q1  When machining ceramic materials, would the vibration of ultrasonic damage the workpiece quality?

A1  The high speed, high frequency "micro-vibration" of ultrasonic machining mechanism actually helps reduce the cutting force during the machining process.  When machining hard and brittle materials such as ceramics, the size of edge-cracks is very small and well-controlled.
 

Q2  How to adjust the feed rate and amplitude when I start machining ceramics with HIT's ultrasonic machining module system?

HIT aims to help clients face the challenges in ceramics machining.  This includes providing the optimized machining parameters (for ultrasonic machining) and services to ensure clients having the best experiences in using HIT's ultrasonic machining module system.

 

Ceramic Machining : Choose HIT