The Piezoelectric crystal is used in a broad variety of common consumer, commercial, and industrial products. These crystals are used in watches, ultrasound equipment, microphones, cigarette lighters, inkjet printers, speakers, and a wide variety of sensors and motors, among many other applications.
What is a Piezoelectric Crystal?
Piezoelectric crystals are capable of the piezoelectric effect, which is the ability of a material to generate an electric charge when subjected to pressure. There are both natural and synthetic materials with this potential.
This effect was discovered in 1880 by Pierre and Jacques Curie, although it didn’t have any practical applications outside of the laboratory for many years. By World War I, it was used in the creation of sonar, which sparked interest in the potential for further technological advances using the piezoelectric effect.
How Do Piezoelectric Crystals Work?
The potential to conduct electricity is a result of the material’s structure. Piezoelectric crystals have a balanced charge with an asymmetric atomic structure. When mechanical pressure is applied, the structure is deformed, pushing the negative charge to one side and the positive charge to the other. This is known as the direct piezoelectric effect. Crystals with symmetric structure aren’t impacted by pressure in this way and are not piezoelectric.
This effect works in reverse as well—passing electricity from an external source through piezoelectric crystals will convert the electrical energy into sound waves. This is what was used to create sonar, and it is called the inverse piezoelectric effect.
How to Generate Electricity from Piezoelectric Crystals
The process is simple for generating electricity from a piezoelectric crystal that is fairly simple. To turn mechanical energy into electrical energy (the direct piezoelectric effect), metal plates are used to squeeze the crystal. The pressure disturbs the atomic structure and creates an electrical charge which is collected by the plates. More pressure means more electrical power.
The inverse piezoelectric effect is created when the balanced crystal, again placed between two metal plates, is charged with electricity. This essentially forces the crystal to squeeze itself, deforming its structure, which releases a sound wave.
Which Type of Crystals/Materials Exhibit Piezoelectricity?
Quartz is probably the most well-known piezoelectric crystal, perhaps because of its use in quartz clocks and watches. However, there are other materials (crystals and others) with this quality found in nature:
Synthetic piezoelectric materials are typically more cost-effective than naturally occurring ones, so manufactured materials like langasite, lithium niobate, barium titanate, potassium niobate, sodium tungstate, lead zirconate titanate (PZT), and others are often used instead of natural crystals. These synthetic options also tend to have stronger piezoelectric potential.
Piezoelectric Materials at Kadco Ceramics
At Kadco Ceramics, we have a great deal of experience machining a wide variety of piezoelectric materials for everything from sonar to medical equipment, and we can help you choose the piezoelectric material that would best suit your application. In some cases, quartz or topaz may be ideal, or it may be better to use synthetic ferroelectric ceramics for their stronger piezoelectric effect and cost-effectiveness. We’re happy to discuss your project and help you determine the best option.
Dicing is commonly used to separate optical components or electronics imaged onto wafers. The substrates can be waxed onto hard mounts to minimize chipping.
Experienced dicing experts are able to make precise cuts and grooves and optically align microscopic patterns.
What is Wafer Dicing?
The wafer dicing process separates small blocks of semiconducting material (known as dice) from a semiconductor wafer. Depending on the application’s needs, the dicing process may involve wafer scribing, through cutting, or wax mounting. The wafer is sawed in the extra spaces between dice to separate them.
Usually, manufacturers mount wafers onto tape to improve their backside support. Once the wafer has been mounted, it’s loaded into a cassette and then into the actual dicing mechanism, which cuts the wafer into individual dice.
The dicing mechanism contains an abrasive blade that it rotates with a spindle at high speeds (usually 30,000–60,000 rpm).
Blades used for this purpose comprise diamond grit embedded into an electroplated nickel matrix. Because these blades are so strong, they easily crush wafers, and any debris that it creates can be removed while the machine works.
The blade moves between active areas of the dice through dedicated lines known as streets. This creates a groove in the substrate material.
Wafer Dicing Techniques
The term “scribing” refers to a specific die singulation technique. This technique uses only one process tool to partially cut through a wafer. Then, a breaking step divides the wafer into individual dice along scribed lines. This separates scribing from the more traditional option of dicing, which involves cutting through a wafer entirely in just one step.
When wafers are through cut on tape, it’s easy to achieve higher tolerances on the final chip size. The primary drawback of this process is that it can result in some bottom-side chipping. Some manufacturers get around this by wax mounting wafers onto glass to offer more precise cuts.
Wax mounting on glass is labor intensive, but doing so often leads to superior quality. Before the process can begin, manufacturers must clean the workpieces, which helps achieve the best possible edge quality. When substrates are wax mounted on glass, the superior bottom-side support results in fewer instances of chipping. Sometimes tape mounting is used for a simpler process.
Wafer Dicing Services at Kadco Ceramics
Dicing work involves quartz, alumina, piezoceramics, glass, and layered combinations of materials. Our work involves not only die singulations on wafers but also cutting grooves and forming surface features.
Our staff uses multiple Disco and K&S dicing machines to meet our clients’ wafer dicing needs. Our certified team of engineers is dedicated to understanding the individual needs of each client—they’ll speak with you about your goals, the tradeoffs you may make to reach them, and any other requirements you’re working with.
If you would like to learn more about Kadco Ceramics’ wafer dicing services, contact us today.
Computer numerical control (CNC) milling is a machining process that uses rotating multipoint cutting tools and computerized controls to cut and shape workpieces into custom-designed components.
Manufacturers use CNC milling to produce a wide range of products from materials ranging from:
In contrast with traditional drilling equipment, CNC milling machines operate along multiple axes, allowing for the creation of a wide variety of shapes, slots, holes, and other impressions required for the specific end application.
How Does the CNC Milling Process Work?
The CNC milling process conforms to the same basic stages of production as other machining processes. These stages include:
CAD model design
Conversion of the CAD model into a CNC program
CNC milling machine setup
Execution of the milling operation
The initial CAD design for the desired product can be rendered in either 2D or 3D. Upon completion of the design, engineers transfer it to a CNC-compatible file. CAM software converts this file into a CNC machine program that will control the milling machine’s subsequent movements and actions.
Next, the CNC machine operator prepares the milling machine to execute the program. The appropriate milling tools are attached to the machine’s spindle, and the workpiece is either affixed to an attached worktable or a vise. The choice between worktable and vise depends on whether the workpiece will remain stationary during the milling operation or slowly be fed into the rotating tool.
When the milling operation begins, the CNC cutting tool reaches speeds as high as thousands of rotations per minute. During operation, the CNC machine will perform one of these three cutting methods:
Slowly feed the material into the rotating tool as it remains fixed in place
Move the rotating tool over and across the stationary target material
Use a combination of the above two methods by moving both the target material and the rotating tool in relation to each other
Additionally, milling equipment operates via one of two methods:
Climb milling, in which the CNC machine feeds the target material with the rotation of the cutting tool
Conventional milling, in which the material is fed against the tool’s rotation
Operators frequently run the target material through the CNC machine multiple times to ensure that it meets specified tolerances. After completing the milling operations, the product is ready for finishing and post-processing.
CNC Milling Machines
Milling machines typically come in either horizontal or vertical forms. Horizontal milling equipment uses horizontally oriented spindles, and vertical milling equipment uses vertically oriented spindles.
The shape, size, and weight of the target workpiece along with its desired result play a large role in determining which type of milling machine would be more effective for a particular operation.
For instance, horizontal milling machines are usually more effective at cutting heavy workpieces, whereas vertical milling machines are ideal for those involving complex designs.
Some common types of CNC milling machines include the following:
These types of milling machines use fixed spindles mounted on vertically adjustable worktables. The machine’s “knee” supports its “saddle,” which in turn supports the worktable.
The machine’s knee is attached to the main column. The knee can be lowered and raised depending on the rotating tool’s position. This CNC machine category includes floor-mounted and bench-type plain horizontal milling machines.
Ram-type milling machines have a movable housing, or “ram,” attached to the main column. The machine spindle attaches to this adjustable housing. This allows the machine tool to enjoy the freedom of movement along the x and y-axes.
Floor-mounted universal horizontal and swivel cutter head milling machines are two very common examples of this type of CNC machine.
In this type of milling machine, worktables are affixed directly to the machine bed, which stabilizes the workpiece and prevents undesirable movement along the y and z axes. The operator positions the workpiece beneath the cutting tool, which is often capable of moving along all three main directional axes (x, y, and z).
Some bed-type milling machines include simplex, duplex, and triplex milling machines. One main difference between these three machines is the number of spindles they employ: simplex machines use one spindle, duplex machines use two, and triplex machines use three.
Planer-type milling machines are comparable with bed-type machines in that they have worktables fixed along the y and z-axes.
They also have spindles that can move along all three of the main directional axes. Planer-type machines offer simultaneous support for multiple machine tools (typically as many as four).
This can greatly reduce the turnaround time for the production of complex parts.
Best Materials for CNC Milling
CNC milling is a versatile manufacturing process that encompasses the use of a variety of materials. The best material to use for a specific order depends on the desired end application of the product.
Some of the harder materials suitable for CNC milling include:
Alumina: Alumina comes in different varieties. Producers use 99.6% alumina for thin-film microwave circuits that operate at higher frequencies. 92% alumina is effective for packaging applications.
Garnet: Garnets are extremely hard metal silicates. They see use in the electronics and optics fields.
LiNbO3: LiNbO3 is a dense synthetic crystal used for photonics applications.
Tungsten: Tungsten is a hard metal that works well in electronic applications.
What Is Core Drilling?
Core drills remove cylindrical cores from targeted areas on a workpiece. Depending on the desired application, the end product could be the newly hollow material or the core itself.
Examples of core drilling machines include machines used for mineral exploration as well as construction core drills that create holes for pipes and manholes.
CNC Milling Service and Core Drilling at Kadco Ceramics
Kadco Ceramics has years of experience in the CNC milling and core drilling industry. We apply our vast expertise to the detailed, precise shaping of just about any machinable hard material. Our experienced machine operators use precision milling equipment to produce complicated, highly customized shapes to client specifications within quick turnaround times.
Ceramics can be made from several different types of hard metal oxides or nitrides. Additionally, materials like silicon carbide (SiC) may not fit the precise definition of a ceramic material, but they can still be classified as part of the ceramic “family.”
Manufacturers use ceramic machining to produce a wide range of mechanical, electrical, and optical appliances. To prepare for the machining process, operators wax mount ceramic substrates onto glass surfaces. Then, operators use manufacturing equipment to cut the ceramic material with focused streams of pressurized water flowing through diamond blades.
Kadco Ceramics performs a variety of ceramic machining operations, such as:
Our experienced machinists ensure that Kadco delivers high-quality work that meets or exceeds client specifications.
CNC Milling and Core Drilling
Two common machining services that Kadco offers are CNC milling and core drilling.
CNC milling stands for computer numerical control milling. Milling is very similar to drilling and cutting, and CNC milling machines perform both of these operations at a variety of angles.
CNC milling is a highly customizable automated machining process. Equipment used for this technique rely on computerized controls and specialized cutting tools to create the desired product by progressively removing material from the workpiece.
How does a CNC milling machine work? The milling process moves through the same four production stages as other machining models. These stages are:
The design of a CAD (computer-aided design) model for the product
The CAD model’s conversion into a CNC program
Setup of the CNC milling machine for operation
Execution of the milling operation
CNC milling machines may be either horizontally or vertically oriented depending on the nature of the cutting operations as well as the properties of the target material. The milling machine’s rotating multipoint (or “multi-tooth”) cutting tools perform the desired milling operations according to the instructions from the CNC program.
Milling operations in which the machine feeds the target material along with the rotation of the cutting tool are known as climb milling processes. In contrast, milling operations that feed the moveable workpiece against the tool’s rotation are referred to as conventional milling processes.
Upon completion of the milling operations, the product passes over to finishing and post-processing operations.
Core drilling removes a cylindrical core from the drill hole. A core drill comprises three main parts:
drill bit or bits
The drill bit(s) are typically coated with either diamond or carbide. Core drills used for concrete generally have diamond-coated drill bits, whereas masonry core drills use carbide-coated bits.
Many types of core drills are in use today. These range from small core drills used by homeowners for DIY projects to huge core drills that cut concrete on big construction projects.
Core drilling allows for the clean removal and analysis of a core of the material. In other applications, where the desired outcome is simply the formation of a hole, the core is discarded.
Wafer dicing is a machining process that separates dice from a wafer of semiconducting material. This separation is accomplished through scribing and breaking, mechanical sawing, or laser-cutting operations. Upon completion of the dicing process, leftover individual silicon chips are encapsulated in chip carriers and are subsequently used in a variety of electronic applications.
Wafers can generally be tape mounted on a film frame for ease of handling. Alternatively, the wafers can be wax mounted on the glass to increase cutting precision. Kadco Ceramics performs several types of wafer dicing operations, including:
Bevel cutting: This cutting process creates a V-shaped groove or chamfer in the target substrate.
Burr control: Combinations of machining tools and speeds can mitigate the burr formed on the target material’s cut edge.
Chip control: Kadco operators carefully monitor factors such as feed, speed, and coolant flow to ensure that edge chipping levels remain well within specifications.
Scribing: Scribing, or marking the wafer, can assist in subsequent breaking operations.
Wraparound metallization: Wraparound metallization provides good grounding properties in microwave circuits.
Cleaning and packaging: Upon completion of dicing operations, thorough die cleaning ensures that the finalized product is in pristine condition and ready for packaging. In some processes, the target substrate can be coated with a protective layer before dicing begins.
Inner or internal diameter (ID) slicing operations are an extremely effective way to create repeated cuts on hard, brittle materials. ID slicing saws provide enhanced accuracy.
The ID slicing saw blade is composed of an annular (ring-shaped) apparatus with a diamond-plated internal diameter. This configuration allows for the machine to perform highly precise cutting operations with minimal kerf loss. ID slicing operations are effective for materials as diverse as:
ID slicing operations typically do not require extensive setup procedures, and they’re usually easy to program. This ease of use often makes ID slicing more cost effective than other methods such as outer diameter slicing or wire sawing.
Surface grinding is a common refining and smoothing process. In this process, a grinding wheel or disc removes the roughness from the target material’s surface, and then it refines the workpiece’s surface and edges too tight tolerances.
There are three basic types of surface grinders:
Grinders with horizontal spindles: In these grinding operations, the flat edge of the grinding wheel contacts the workpiece, leading to high-precision results.
Grinders with vertical spindles: In contrast with horizontal spindle grinders, vertical spindle or wheel-face grinders remove large amounts of material at a time. The face of the grinding wheel, instead of its edge, comes into contact with the targeted surface.
Single- or double-disc grinders: Disc grinders can be horizontally or vertically aligned, and they often can grind two sides of the workpiece at the same time.
Piezoelectric materials can generate electrical charges when placed under mechanical tension or pressure. Examples of piezoelectric materials include:
A number of ceramic types can also be classified as piezoelectric, such as:
Piezoelectric machining helps produce a wide range of applications. For example, soft piezoelectric ceramics build ultrasonic transmitters and receivers, microphones, sound transducers, and other electronic products.
Ceramic Machining Services at Kadco Ceramics
Our primary goal at Kadco Ceramics is to provide clients with high-quality work at reasonable prices. We work hard to ensure that our products meet your specifications down to the smallest detail. We’re committed to providing our customers with the highest level of satisfaction.
At Kadco Ceramics, our engineers and machine operators work with a wide range of materials, such as:
Since 1982, we’ve provided cost-effective engineering and manufacturing solutions to a broad spectrum of clients. We work hard to preserve our reputation as a premier source for ceramic machining services.
If you’d like to learn more about how our ceramic machining services can benefit your company, please reach out to us today.
Introduction to Piezoelectricity and Piezoelectric Ceramics
Piezoelectricity is the creation of electric potential in certain materials when they are under mechanical stress, such as bending, stretching, or compressing. Physicists refer to this phenomenon as the piezoelectric effect. The materials that exhibit these characteristics are called piezoelectric materials.
The piezoelectric effect happens when the electric charge domains in the piezoelectric material are displaced under stress. Piezoelectric materials also exhibit the reverse property – called inverse piezoelectric effect – of changing shape in an electric field. The inverse property is due to the external electric field pushing the positive and negative charge crystals inside the material away from each other.
Piezoelectric materials are used for making many household items such as inkjet printers and quartz watches, as well as industrial devices like sound generators and detectors.
Quartz and topaz are examples of naturally occurring piezoelectric materials. There are many other natural piezoelectric materials, but synthetic ferroelectric ceramics exhibit stronger piezoelectric effects and are far more affordable. Hence, ceramic piezoelectric materials have been widely adopted by the industry.
What Are Piezoelectric Ceramics
Ceramics, in general, are made up of electrically charged crystals. In most ceramics, except ferroelectric ceramics, the electrical charges of the crystals balance out. Ferroelectric ceramics are electrically polarized and hence possess piezoelectric properties.
Right after they are made, however, they do not exhibit piezoelectric effects due to the random distribution of electrical charge bearing crystals. The crystals need to be aligned by applying a high DC voltage, thus polarizing the ceramic to make it piezoelectric. Once they are polarized, piezoelectric ceramics retain polarization even when the DC voltage is removed.
Piezoelectric ceramics include:
Lead Zirconate Titanate (PZT)
The latter, PZT, is the most widely used and is a mix of lead zirconate and lead titanate. PZT has higher piezoelectric sensitivity and greater stability at high temperatures than other materials. In addition, the piezoelectric properties of PZT can be formulated to be hard or soft. All these characteristics have led to the wide adoption of PZT, despite environmental concerns about the use of lead.
Soft vs Hard Piezoelectric Materials
Softness or hardness of a piezoelectric material refers to how easily they are polarized. Soft piezoelectric materials are easily polarized while hard ones are not.
Soft piezoelectric materials have a high coupling coefficient, which means that they have greater sensitivity to electric fields. They also have a high piezoelectric charge coefficient, a high dielectric constant and a noise-free response to the stimulus. Their common applications include:
Equipment for non-destructive inspection and testing in the automotive and aeronautical industries
Hard piezoelectric materials require a high DC voltage for polarization. They are very stable and operate well in environments with high mechanical or electric stress. So they are used in ultrasonic cleaners and sonar devices that call for high electrical power and mechanical strength.
Piezoelectric Ceramics from Kadco
Piezoelectric ceramics are used in a wide range of household products and industrial applications. It is important that you work with the right vendor to select the appropriate ceramic material and shape it to your specifications.
Kadco Ceramics can help you choose piezoelectric ceramics with the right characteristics for your application. We also offer a variety of machining services for your prototyping or production needs.
Our piezoelectric machining capabilities can produce the complex geometries required for varied ultrasonic applications ranging from submarine detection to non-invasive neurological surgery for Parkinson’s disease.
The piezoelectric effect was discovered by brothers Pierre and Jacques Curie in 1880, and named after the Greek word piezein, that means to press or squeeze. They found that certain crystals were able to generate an electrical charge when mechanically loaded with tension or pressure. If exposed to an electric field, the same crystals would undergo a controlled deformation known as the inverse piezoelectric effect.
Compression and tension generate voltages of opposite polarity, so when compressed, the piezoelectric material decreases in volume and will have a voltage that has the same polarity as the material. When subjected to tension, the material will increase in volume and its voltage will be opposite to the polarity of the material.
Piezoelectric materials produce a voltage that is proportional to whatever mechanical pressure is applied.
When discussing piezoelectric ceramics and/or materials, it is important to know there are two types of material – crystals and ceramics. Most crystals occur naturally, while piezoelectric ceramics are manmade.
Quartz, the second-most common mineral in the Earth’s crust after feldspar.
Berlinite, a rare transparent high-temperature mineral that has the same crystal structure as quartz.
Topaz, a gemstone that forms in numerous colors.
Tourmaline, classified as a semi-precious stone.
Cane sugar used to manufacture granulated sugar.
Rochelle salt, made from two of the first materials found to be piezoelectric: potassium sodium tartrate and monopotassium phosphate.
Manmade crystals include:
Gallium orthophosphate, a colorless crystal with similar properties to quartz, but double the piezoelectric effect.
Langasite, a piezoelectric crystal similar to quartz that was first produced about two decades ago.
There are a number of piezoelectric ceramic types, including:
Lead zirconate titanate (PZT)
Piezoelectric systems manufactured today are primarily made from PZT, which is a mixture of lead zirconate and lead titanate crystals, or PZT and barium titanate. Making piezoelectric ceramics involves mixing the components in very specific proportions, then heating them to create a uniform powder. This powder is mixed with an organic binder before being formed into various structural elements.
Once the elements have been fired according to specified temperature and time requirements, they are shaped and trimmed, and electrodes are applied to surfaces where required. A variety of tools are used for this, but ID slicing saws are one of the most common and efficient solutions for machining piezoceramics.
Difference Between Ferroelectric and Piezoelectric Materials
While all ferroelectric materials are piezoelectric, not all piezoelectric materials are ferroelectric.
Ferroelectric and piezoelectric materials respond differently to electric fields, with the latter requiring a very high electric field. The field needed is so intense that the material achieves electric breakdown before polarization can occur. When the temperature is altered, however, the polarization of the crystal changes.
Conversely, ferroelectric materials are polarized spontaneously even though are piezoelectric. This is because of a lack of symmetry in the material caused by a crystal structure that is non-centrosymmetric. Ferroelectric materials also exhibit permanent magnetic behavior.
Piezoelectric material will generate electric potential if is subjected to some sort of mechanical energy. With ferroelectric material, when an external electric field is applied, polarization can be reversed.
Material classes for piezoelectric materials include organic, ceramic, and single crystals, while ferroelectric materials are only organic or ceramic in nature.
Although piezoelectric materials produce electricity, the quantity is too small to be usable.
Hard and Soft Piezoelectric Materials
Piezoelectric materials may be hard or soft, depending on the mobility of the charged or magnetized dipoles in the material. This directly affects polarization and depolarization.
PZT materials that are ferroelectrically hard can be subjected to very high mechanical and electrical stresses without affecting noticeable changes to their properties. They also have substantial advantages, including good stability, operating field strength, and high mechanical qualities.
Soft materials are fairly easy to polarize, even when field strengths are low. This gives them several advantages, such as:
Large piezoelectric charge coefficients
Moderate permittivity that enables storage of electrical energy
High coupling factors
Piezoelectric Ceramics Applications
Piezoelectric ceramic materials have a wide range of applications, particularly for devices that are fuel-igniting, for solid-state batteries, and devices that are force-sensing. However, hard and soft materials have distinctly different uses.
Hard materials are particularly well suited to high-power acoustic applications. These include:
Ultrasonic cleaning devices
Tools used for drilling, bonding, and welding
Medical and surgical instruments
Soft piezoelectric ceramics are ideal for:
Sensors, including conventional vibration detectors
Ultrasonic transmitters and receivers
Actuators used for nano-positioning or micro-positioning
Object monitoring and identification
Electro-acoustic applications, including microphones and sound transducers
Sound pickups for musical instruments
Kadco Ceramics specializes in precision diamond machining and milling to produce components with complex geometries. Our equipment includes ID slicing saws and other machines which are ideal for machining and cutting piezoelectric ceramics. We have a great deal of experience machining piezoelectric materials for a variety of applications and industries.
If you work with piezoelectric materials, the professional team at Kadco Ceramics is ready to discuss your needs. Please contact us to see how we can help you.