Tape Casting - Revision history

NBT MLCC at 20:21, 30 October 2022

2022-10-30T20:21:16Z

NBT MLCC at 20:21, 30 October 2022

2022-10-30T20:21:05Z

NBT MLCC at 20:20, 30 October 2022

2022-10-30T20:20:32Z

NBT MLCC at 20:18, 30 October 2022

2022-10-30T20:18:52Z

NBT MLCC at 20:15, 30 October 2022

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NBT MLCC at 20:14, 30 October 2022

2022-10-30T20:14:58Z

NBT MLCC at 20:13, 30 October 2022

2022-10-30T20:13:55Z

NBT MLCC at 20:12, 30 October 2022

2022-10-30T20:12:45Z

NBT MLCC: /* Tape characterization */

2022-10-30T20:11:17Z

‎Tape characterization

NBT MLCC: /* Tape characterization */

2022-10-30T20:11:03Z

‎Tape characterization

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 [[File:Schematic doctor blading_2.png|500px|thumb|Schematic of the doctor blade tape casting technique. The slip is poured in a reservoir and cast on a carrier substrate on an exemplarily granite block. The doctor-blade height defines the green tape's thickness.]]
 === Tape casting machine ===
 Tape casting machines are available in different scales. Usually big industrial companies have continuous tape casters with a length of up to several hundred meters. However, in academic research much smaller lab-scale tape casters are used which can range from half a meter to several meters in length. Major components of such machines are a solid and level casting surface, reservoir for the slip, doctor blade systems, drying chamber with measures for controlling the airflow and temperature of the air during drying, an adjustable speed drive control during casting, and underbed heating systems. Underbed heating systems and drying chambers are optional; however, both are useful measures to control variables during drying. The ingredients of the slip need to be adjusted towards elevated temperatures to avoid rapid drying and bubbling. Solvents may evaporate much faster thereby degrading the green tape severely. It is recommended to use temperatures close to room temperature.

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 One of the most well-known and used method to manufacture multilayered ceramic components is the doctor blade tape casting technique. Glenn N. Howatt is regarded as the godfather of tape casting and established this processing method in 1947<ref>[https://doi.org/10.1111/j.1151-2916.1947.tb18889.x] Howatt, G.N., Breckenridge, R.G. and Brownlow, J.M. (1947), FABRICATION OF THIN CERAMIC SHEETS FOR CAPACITORS. Journal of the American Ceramic Society, 30: 237-242.</ref> and also filed the first patent in 1948<ref>[https://patents.google.com/patent/US2582993A/en] Howatt, G.N., Method of Producing High Dielectric High Insulation Ceramic Plates, U.S. Patent 2,582,993 (filed October 29, 1948).</ref>. A plentiful variety of electronic components like multilayer ceramic capacitors (MLCC), actuators (MLA), varistors (MLV) or tapes for low/high temperature cofired ceramics (LTCC, HTCC) can be manufactured.
 [[File:Schematic doctor blading_2.png|500px|thumb|Schematic of the doctor blade tape casting technique. The slip is poured in a reservoir and cast on a carrier substrate on an exemplarily granite block. The doctor-blade height defines the green tape's thickness.]]
 == Components of a tape caster ==

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 One of the most well-known and used method to manufacture multilayered ceramic components is the doctor blade tape casting technique. Glenn N. Howatt is regarded as the godfather of tape casting and established this processing method in 1947<ref>[https://doi.org/10.1111/j.1151-2916.1947.tb18889.x] Howatt, G.N., Breckenridge, R.G. and Brownlow, J.M. (1947), FABRICATION OF THIN CERAMIC SHEETS FOR CAPACITORS. Journal of the American Ceramic Society, 30: 237-242.</ref> and also filed the first patent in 1948<ref>[https://patents.google.com/patent/US2582993A/en] Howatt, G.N., Method of Producing High Dielectric High Insulation Ceramic Plates, U.S. Patent 2,582,993 (filed October 29, 1948).</ref>. A plentiful variety of electronic components like multilayer ceramic capacitors (MLCC), actuators (MLA), varistors (MLV) or tapes for low/high temperature cofired ceramics (LTCC, HTCC) can be manufactured.
 [[File:Schematic doctor blading_2.png|500px|thumb|Schematic of the doctor blade tape casting technique. The slip is poured in a reservoir and cast on a carrier substrate on an exemplarily granite block. The doctor-blade height defines the green tape's thickness.]]
 == Components of a tape caster ==
 === Tape casting machine ===
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 Drying chambers are not necessary to cast tapes. They, nevertheless, come with lots of benefits for the process. First of all, the drying process can be controlled by keeping a constant drying rate of the slip. Choosing the right amount of air flow is equally important as retaining a steady temperature. The drying rate is highly dependent on the ingredients of the slip. The vapor pressure of solvents highly impact the drying behavior of the fluid film after casting. Another advantage that comes along a drying chamber is keeping dirt and dust away from the tape. Especially for small lab-scale tape casters drying chamber are not always available or has to be custom-made.
 == Process of tape casting ==
 === Slip delivery ===

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 Continuous as well as discontinuous tapes can be prepared with lab-scale tape casters. For continuous tapes, guide rollers, and rollers with the carrier substrate are needed. If discontinuous tapes are produced, carrier substrate sheets can be used likewise.
-[[File:Collage tape caster small.png|800px|thumb|center|left and center: Lab-scale doctor-blade tape casters. Reservoirs and doctor-blade are exchangeable. An additional underbed heating system in the center device supports constant drying rates. Right: Lab-scale tape casting machine from KEKO equipment d.o.o. with drying chamber. The carrier substrate is moving here while the doctor blade is stationary.<ref>[https://www.keko-equipment.com/Laboratory_Tape_Casters_L-series.php] Webpage KEKO equipment d.o.o. Laboratory Tape Casters L-Series, accessed: October 29, 2022</ref>]]
+[[File:Collage tape caster small.png|600px|thumb|Left: Lab-scale doctor-blade tape caster with exchangeable Reservoir and doctor blade. Right: Lab-scale tape casting machine from KEKO equipment d.o.o. with drying chamber and integrated underbed heating. The carrier substrate is moving here while the doctor blade is stationary.<ref>[https://www.keko-equipment.com/Laboratory_Tape_Casters_L-series.php] Webpage KEKO equipment d.o.o. Laboratory Tape Casters L-Series, accessed: October 29, 2022</ref>]]
 === Carrier substrate ===

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 One of the most well-known and used method to manufacture multilayered ceramic components is the doctor blade tape casting technique. Glenn N. Howatt is regarded as the godfather of tape casting and established this processing method in 1947<ref>[https://doi.org/10.1111/j.1151-2916.1947.tb18889.x] Howatt, G.N., Breckenridge, R.G. and Brownlow, J.M. (1947), FABRICATION OF THIN CERAMIC SHEETS FOR CAPACITORS. Journal of the American Ceramic Society, 30: 237-242.</ref> and also filed the first patent in 1948<ref>[https://patents.google.com/patent/US2582993A/en] Howatt, G.N., Method of Producing High Dielectric High Insulation Ceramic Plates, U.S. Patent 2,582,993 (filed October 29, 1948).</ref>. A plentiful variety of electronic components like multilayer ceramic capacitors (MLCC), actuators (MLA), varistors (MLV) or tapes for low/high temperature cofired ceramics (LTCC, HTCC) can be manufactured.
-[[File:Schematic doctor blading_2.png|400px|thumb|Schematic of the doctor blade tape casting technique. The slip is poured in a reservoir and cast on a carrier substrate on an exemplarily granite block. The doctor-blade height defines the green tape's thickness.]]
+[[File:Schematic doctor blading_2.png|500px|thumb|Schematic of the doctor blade tape casting technique. The slip is poured in a reservoir and cast on a carrier substrate on an exemplarily granite block. The doctor-blade height defines the green tape's thickness.]]
 == Components of a tape caster ==
 === Tape casting machine ===

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 * The quality of the cast tape can be checked with rather easy measures. A light transmission analysis (LTA) compares the light transmission in different regions of the tape. It helps to identify streaks, cracks, bubbles, dust, wrinkles, non-uniform thicknesses, and agglomerates. A perfect tape would be completely uniform and light is transmitted equally. However, any inhomogeneity disturbs the transmission of light. Alternatively, this can also be performed by utilizing the human eye as the detector.
 * The green tape thickness and its flatness/uniformity is probably the most vital characteristic to be evaluated. Various instruments are available to measure the thickness of the tape. Nevertheless, a micrometer with flat faces is supposed to be the most appropriate device. Tips and faces of some calipers or micrometers have rounded or sharp tips and are inappropriate due to too high pressures.
 * Determining the green oxide-only density is another key parameter. Enough shrinkage and high fired densities can only be achieved when ceramic particles are in proximity already in the green state but especially after the binder burnout. This density is calculated by the mass of ceramic powder per unit volume while organics and volatile ingredients are not taken into account. This is necessary because after binder burnout usually only the brittle and rigid ceramic network within the pre-defined volume is left.