What is the Tape Casting Process?

Have you ever thought about how the small electronic parts in your smartphone, an electric vehicle, or medical devices are produced? As technology continues to get smaller in size, the need for extremely thin and very reliable materials keeps growing as well. The most basic method for producing these extremely small parts is the tape casting process (also referred to as the "doctor blade process"), which is used to make extremely thin sheets of ceramics and metals based on its tape casting process; tape casting is supported by many scientific principles.

Whether you are an engineering major or student learning about material science, a procurement manager looking for new equipment for your facility, or even a tech enthusiast interested in how multilayer ceramic capacitors (MLCC) are created, this article will provide you with all the relevant info you require. This will include an in-depth explanation of the science behind the process, an exploration of the various pieces of specialized machinery needed in this manufacturing process and answers to the most commonly asked questions within the manufacturing industry.

How is the Tape Casting Process Completed?

The doctor blade process was developed in 1947 and is considered a liquid-forming method of manufacturing parts. With the doctor blade process, a liquid/slurry is placed onto a flat moving surface to produce continuous, thin and flexible sheets of material.

Below are the individual steps involved with using this type of process:

1. Prepare the slurry: The raw ceramic or metal powders are thoroughly mixed with solvents, binders, plasticizers, and dispersants to produce a homogeneous liquid/slurry that has the consistency of paint.
2. Fill the casting reservoir: A pump moves the slurry into a reservoir that is located behind the doctor blade.
3. Spread the slurry: A carrier film (generally made of plastic or steel, e.g., PET) moves under the doctor blade. The distance between the blade and the film determines the precise thickness of the wet sheet (somewhere between several micrometres and a few millimetres).
4. Dry the coating: The coated carrier film passes through a long drying chamber that has controlled temperature. The solvents evaporate from this chamber, resulting in the formation of a flexible, solid sheet called "green tape."
5. Process the green tape: The green tape can then be cut, punched, stacked, and finally fired in a high-temperature kiln to create the final rigid component.

The Heart of the Operation: The Tape Casting Machine

Tape casting machines are required in order to perform this process. A tape casting machine is designed to produce very precise products and must be capable of maintaining precision tolerances during continuous production runs.

Uses and Applicable Scenarios

Tape casting machines can only be used in advanced manufacturing environments. The process of tape casting is the most frequent use of tapes in the field of ceramics. Tape casting is used for most commercial applications of:

Multilayered Ceramic Capacitors (MLCCs): These are the small energy-storage devices predominately supplied in the electrical circuit boards manufactured today.

Low Temperature Co-fired Ceramics (LTCCs): Components used in the manufacture of high-frequency, radio frequency modules commonly used in 5G and aerospace communication systems.

Solid Oxide Fuel Cells (SOFCs): Thin ceramic layers used for clean energy generation.

Piezoelectric Sensors: Found in medical ultrasound equipment and automotive sensors.

Top Manufacturers

The market for tape casting equipment is small. There are manufacturers of tape-casting equipment around the globe, but the majority of these companies are highly specialized, and have significant experience in working with advanced materials and automated handling of large rolls of material.

The most established manufacturer of tape-casting equipment is KEKO Equipment. This company is a European manufacturer that is recognized for offering some of the most technologically advanced manufacturing equipment on the market today, in the areas of MLCC and LTCC casting/stacking.

The second-most established is HED International (Pro-Cast), an American-based company known for providing highly advanced and custom-built tape-casting machines for many different types of industries.

The third-most established company is Upper Shell, which is one of the leading manufacturing enterprises in the high-tech manufacturing industry, specializing in complete production lines. They are highly regarded for their fully automated, high-precision equipment used for both ceramic casting and printing.

The fourth company is Richard E. Mistler, Inc.: Often regarded as an originator in the field and producing very custom-designed tabletop and pilot-scale casting machines.

Price Range

These systems vary from small laboratory models to large multi-zone factory systems; therefore, there is a wide range of pricing for these machines:

• Lab/Benchtop Machines: These are the best choice for university research and development and generally cost between $15,000 and $50,000.
• Pilot Production Machines: Medium-sized machines for producing relatively low-volume units usually cost between $80,000 and $250,000.
• Industrial Mass-Production Lines: Fully automated machines with advanced optical scanning inspection; precise slurry delivery; and multi-zone thermal drying can exceed $500,000 to $1,500,000+.

Frequently Asked Questions (FAQ)

What is the difference between slip casting and tape casting?

Although both use a liquid ceramic mixture, slip casting and tape casting have very different applications and how they function. Slip casting uses a porous plaster mold to hold the liquid mixture— and the water will be absorbed by the mold through the thickness of the liquid, resulting in a solid clay shell on the outside of the mold. This method is traditionally used to make complex three-dimensional shapes such as toilet bowls, vases, and hollow figurines. Tape casting, on the other hand, is a two-dimensional process used to create continuous ultra-thin flat sheets for electronic components.

What are the benefits of tape casting?

This process has many unique advantages over other production processes that cannot replicate these advantages:

Ultra-Thin Capability: Only because of the cost-effective manner in which high-quality ceramic sheets can be created thinner than a human hair (down to 1-2 microns).

Excellent Surface Finish: The resulting "green tape" produced by tape casting has an incredibly smooth surface finish, essential for printing microscopic electronic circuits.

Scalability: As a continuous roll-to-roll process, manufacturers can produce miles of ceramic tape within a single day.

What are the four types of casting?

In the broader world of manufacturing and metallurgy, when we refer to casting, it generally involves pouring a liquid into a mold. The four main types of industrial casting processes are:

Sand Casting: Pouring molten metal into a mold made out of compacted sand, which works great for things such as engine blocks.

Die Casting: Forcing molten metal into steel molds through high pressure; used for creating complex and high-volume parts.

Investment Casting (Lost-Wax): Using wax patterns melted away, leaving a ceramic mold to cast molten metal (ideal for making parts such as turbine blades in aerospace).

Centrifugal Casting: Pouring molten metal into a mold rotating at a high speed, using centrifugal force to create hollow cylindrical objects such as pipes.

Note: Although the word "casting" in tape casting has the same name as the other casting methods, tape casting is not volumetrically molded, but rather is a web coating fluid forming process.

Understanding the tape casting process helps to better understand the processes used to create today's electronic and energy systems. From the precision of the rheology of the ceramic slurry to the precision of the doctor blade gap on a commercial tape casting machine, tape casting is required to be engineered with precision. As more and more industries improve their ability to utilize tape casting for ceramic-based applications, they will be able to expand their capabilities to create faster, smaller, and more efficient technology that continues to drive our world.