多层陶瓷基板制造技术

采用CuO浆料为布线导体材料是制造多层陶瓷基板的新技术,该方法可彻底除去浆料中的有机物,制造性能良好,易于推广和批量生产的多层陶瓷基板,本文总结了CuO多层陶瓷基板材料及其制造技术,分析了各工艺对基板性能的影响,确定了最佳技术条件。     

Low-pressure,thermo-compressive lamination

Lamination of green ceramic tapes is one of the most important technological processes in multilayer ceramic technology. Lamination affects the quality of all 3D structures (e.g., channels, chambers, membranes, etc.). Novel chemical methods of lamination reduce the deformation of 3D structures. However, these methods are useless in the fabrication of thin membranes and structures with thick-film electronic components or electric vias. Therefore, thermo-compressive lamination is still the best solution for the lamination of green ceramic tapes. Low-pressure thermo-compressive lamination with an insert material is presented in this paper. The influence of pressure and Low Temperature Cofired Ceramics (LTCC) material on the compressibility and shrinkage of LTCC, as well as the influence of the insert material on deflection and distortion of the membranes are presented and discussed in this paper.     

Three-dimensional stress analysis of composite structures using isodyne techniques

It is known that the stresses in lamination planes of composite structures are pronouncedly three-dimensional, and that criticality of the lamination defects is often very high. It is also known that the classical methods of photoelastic stress analysis are often not reliable when stress states are three-dimensional, with the exception of the gamma-ray stress-freezing method. The paper presents analytical and empirical evidence that the recently developed “isodyne” techniques allow reliable determination of the 3-D stresses existing in components of real composite structures and in lamination planes.     

Study of deformation and porosity evolution of low temperature co-fired ceramic for embedded structures fabrication

The deformation behaviors of suspended low temperature co-fired ceramic (LTCC) laminates over a cavity and the evolution of open porosity of LTCC are studied for the fabrication of embedded structures in a multi-layer LTCC platform using carbon material. The effects of the type of LTCC materials (self-constrained and unconstrained LTCC), cavity width, laminate thickness, and lamination conditions on the deformation of the suspended LTCC laminate over a cavity are studied. For suspended three-layers and six-layers LTCC laminates over cavity width ranges from 10 to 25 mm, the self-constrained LTCC laminates were more dimensionally stable (sagged by less than ?120 μm) after sintering as compared to the unconstrained LTCC. The evolution of open porosity and the distribution of open pores in the self-constrained LTCC with changes in sintering temperature and laminate thickness are also studied for process optimization.     

Fabrication of Functionally Graded and Aligned Porosity in Thin Ceramic Substrates With the Novel Freeze–Tape-Casting Process

Functionally graded and continuously aligned pore structures have been fabricated by a modified tape-casting process for use as solid oxide fuel cell electrodes, catalysts, sensors, and filtration/separation devices. Pore gradients from <5 to 100 μm and aligned pore tubules have been directly fabricated in various ceramic materials with thin substrate sections approximately 500–1500 μm utilizing both low-toxicity aqueous-based slips and organic solvents. This process allows for the generation of pores without the use of thermally fugitive pore formers in a single processing step with no need for tape lamination. The incorporation of tape casting, unidirectional solidification, and the freeze-drying process results in uniformly acicular pores aligned with the direction of the moving carrier film. Processing and microstructure variability will be discussed as it pertains to the effects of solids loading, freezing temperatures, and solvent type. Applications for this ceramic processing technology will also be discussed.     

Hot Embossing: An Alternative Method to Produce Cavities in Ceramic Multilayer

New applications of ceramic multilayers, for example, in biotechnology, sensor technology, and chemical micro-reaction technique, call for cavities with complex geometries. Hot embossing offers a promising, cost-effective way to generate these structures on the surfaces of green tapes or laminates. Cavities inside low-temperature co-fired ceramic multilayer were manufactured by a combination of hot embossing, lamination by a special adhesive technique, and zero shrinkage sintering. The edge and surface quality in the green state as well as the sintered multilayers with surface structures and cavities were extensively characterized by laser surface scanning, optical and ultrasound microscopy. Sintering shrinkage of hot-embossed laminates could be reduced in the x and y directions to less than 0.5%.     

Cold chemical lamination of ceramic green tapes

The cold chemical lamination (CCL) is a new technique of bonding ceramic green tapes into one 3D structure. Instead of a standard thermo-compression method, new solvent-based lamination is presented. A film of a special chemical agent is put on the green tape surface. The solvent melts the surface. Then the tapes are stacked. The bonding of the green tapes is made at a room temperature. The new method is used for joining green tapes of the low temperature co-fired ceramics (LTCC). A quality of the bonding depends on the solvent type. The cold chemical lamination is examined on two types of the LTCC tapes: DuPont 943 and DuPont 951. Six types of the solvents are analyzed in the paper. The bonding quality and geometry of the test structures are examined. The lamination quality is investigated by the scanning electron microscope.     

Tape casting of ferroelectric,dielectric, piezoelectric and ferromagnetic materials

Tape casting is a feasible method for preparing ceramic tapes with different electrical and magnetic properties for multilayer ceramic devices. This paper describes the tape casting process for several different electroceramic materials (BST, PZT, NZF and ZSB) utilising similar organic additive and solvent systems. The properties of tapes with different ceramic compositions before and after sintering are investigated, including surface roughness, shrinkage and microstructures. The parameters affecting the casting, shrinkage, lamination, thickness and tensile strength of green tape are also presented. This enables process design for tape which can be used in devices with true integration of dielectric and piezoelectric, ferroelectric and ferromagnetic layers in 3-dimensional multilayer structures.     

相变增韧和层状复合协同强韧化Al2O3陶瓷

本文采用相变增韧和层状复合协同强韧化Ａｌ２Ｏ３复合陶瓷,相变增韧制备出ＺＴＡ陶瓷,在此基础上,采用层状复合工艺,制备出ＺＴＡ／ＢＮ陶瓷。研究结果表明：相变增韧和层状复合协同强韧化Ａｌ２Ｏ３能基本保持陶瓷抗弯强度,冲击韧性提高了３７倍。     

Improved Compaction in Multilayer Capacitor Fabrication

The most common defects found in multi-layer ceramic capacitors are derived from residual porosity formed when solvents and binders are released from a ceramic green body. Without a well-controlled compaction technique, defects between sheets in the stacked body are often present, leading to lamination problems. This paper suggests alternative approaches, using compaction applied before and/or after the process of binder burnout with the intention of reducing the number of stacking-generated defects and the volume of voids formed after binder burn-out. Barium titanate tapes and stacked multilayer electroded discs have been investigated and characterised by microstructural examination and density measurement. The resulting properties are described, and the behaviour of the multi-layers discussed in terms of the microstructure and processing procedures. It is shown that the porosity content of sintered samples compacted at 300 MPa is approximately half that of samples compacted at 30 MPa when both are sintered at 1300°C for 2 h. A further improvement of densification can be achieved by a postcompaction treatment after binder burn out.     

Fabrication and Characterization of Dual-Channeled Zirconia Ceramic Scaffold

A novel porous ceramic with a structure containing two three-dimensional (3D) pore channels in a tetragonal zirconia polycrystals (TZP) ceramic was fabricated using a combination of a CNC-machining method and slurry coating process. A graphite scaffold with a single interconnected 3D channel as a template was prepared using CNC machining and lamination. The surfaces of the graphite scaffold were then coated uniformly with the TZP slurry, followed by heat treatment at 900°C for 3 h in air to remove the graphite material completely via thermal oxidation and at 1400°C for 3 h in air to sinter the TZP walls. This process produced a dual-channeled TZP scaffold with an additional 3D channel, which replicated the 3D graphite structure with the pre-existing channel. The fabricated scaffold showed ultra-high porosity (91%), high surface area, and high compressive strength (2.04 MPa), as well as a tightly controlled pore structure.     

Reflection intensity measurement using non-contact microwave probe and in-plane mappings for dielectric device

The reflection intensity measurement using non-contact microwave probe was carried out for multi-layer ceramic capacitor. The spatial resolution of non-contact microwave probe was improved the basis of Kirchhoff's diffraction formula with decreasing diameters of the coaxial cable and probe. Using Reflection intensity mappings, the dielectric permittivity distribution in micro-region at 9.4 GHz was measured for the cross-section of a multi-layer ceramic capacitor at room temperature. The spatial resolution was experimentally estimated to be about 10 μm from mappings of the dielectric and inner electrode layers in the multi-layer ceramic capacitor.     

Direct integration of dielectric all-ceramic thick films on a polymer substrate using room temperature fabrication

Direct integration of all-ceramic thick films and a polymer substrate has been realized for the first time without high temperature processing using the Room Temperature Fabrication method.Printable Li₂MoO₄-BaTiO₃ composite pastes with 0, 10, and 20 vol.% of BaTiO₃ were fabricated from the respective ceramic powders and water without organic additives or vehicles. The pastes were stencil printed on a polyimide substrate and dried at 120 °C without pressing or lamination.Using scanning electron microscopy, the films were observed to be in seamless contact with the substrate and to have a uniform microstructure. Relative permittivities of the ceramic films increased from 4.2 to 7.2 (at 2.5 GHz) and 4.5 to 7.5 (at 9.9 GHz) according to the vol.% content of the added BaTiO3, with corresponding dielectric losses from 10⁻³ to 10^-2.The results show that the room temperature fabrication method enables 2D printing of all-ceramic thick films on temperature-sensitive substrates.     

Self-supported ceramic substrates with directional porosity by mold freeze casting

Manufacture of thin-film ceramic substrates with high permeability and robustness is of high technological interest. In this work thin (green state thickness ∼500 μm) porous yttria-stabilized zirconia self-supported substrates were fabricated by pouring stable colloidal aqueous suspensions in a mold and applying directional freeze casting. Use of optimized suspension, cryoprotector additive and mold proved to deliver defect free ceramic films with high dimensional control. Microstructure analysis demonstrated the formation of desirable aligned porosity at macro-structural scale and resulted to be highly dependent on colloidal behaviour and freeze casting conditions. Manufactured green films were joined by lamination at room temperature and sintered to obtain symmetrical cells consisting of two porous self-supported substrate electrodes (∼420 μm) and dense yttria stabilized zirconia electrolyte (∼10 μm).     

Fabrication of embedded microfluidic channels in low temperature co-fired ceramic technology using laser machining and progressive lamination

This paper describes the application of laser micromachining techniques for the fabrication of microfluidic channels in low temperature co-fired ceramic, LTCC, technology. It is shown that embedded cavities can be successfully realised by employing a recently proposed progressive lamination process with no additional fugitive material. Various microfluidic structures have been fabricated and X-ray imaging has been used to assess the quality of the embedded channels after firing. The problem of achieving accurate alignment between LTCC layers is addressed such that deeper channels, spanning more than one layer, can be fabricated using a pre-lamination technique. A number of possible applications for the presented microfluidic structures are discussed and an H-filter particle separator in LTCC is demonstrated.     

Low‐Temperature Co‐Fired Ceramic Substrates for High‐Performance Strain Gauges

Recent advances in the development of high gauge factor thin films for strain gauges prompt the research on advanced substrate materials. A glass ceramic composite has been developed in consideration of a high coefficient of thermal expansion (9.4 ppm/K) and a low modulus of elasticity (82 GPa) for the application as support material for thin‐film sensors. In the first part, constantan foil strain gauges were fabricated from this material by tape casting, pressure‐assisted sintering, and subsequent lamination of the metal foil on the planar ceramic substrates. The accuracy of the assembled load cells corresponds to accuracy class C6. That qualifies the load cells for the use in automatic packaging units and confirms the applicability of the low‐temperature co‐fired ceramic (LTCC) substrates for fabrication of accurate strain gauges. In the second part, to facilitate the deposition of thin‐film sensor structures to the LTCC substrates, pressure‐assisted sintering step is modified using smooth setters instead of release tapes, which resulted in fabrication of substrates with low average surface roughness of 50 nm. Titanium thin films deposited on these substrates as test coatings exhibited low surface resistances of 850 Ω comparable to thin films on commercial alumina thin‐film substrates with 920 Ω. The presented material design and advances in manufacturing technology are important to promote the development of high‐performance thin‐film strain gauges.     

Monolayer Packing of Submicrometer Ceramic Spheres by Employing a Langmuir–Blodgett Film of Dicarboxylic Acid

A closely packed monolayer of spherical SiO₂ or SiO₂–TiO₂ particles of submicrometer size has been fabricated on a silicon or glass substrate by employing a Langmuir–Blodgett (LB) film of 1,12-dodecanedicarboxylic acid, followed by dehydration–condensation reaction between carboxyl groups of the dicarboxylic acid and surface hydroxyl groups of both the substrate and the ceramic spheres. Deposition of the LB film on the substrate was essential for immobilization of ceramic spheres. The flexibility of an alkyl chain in the dicarboxylic acid may have resulted in better capturing of ceramic spheres compared with surface hydroxyl groups on the substrate. Two-dimensional packing of the ceramic spheres immobilized became dense with decreasing molecular area of the dicarboxylic acid in the LB film and the temperature of the LB medium (water), although partial three-dimensional attachment of ceramic spheres was observed, especially when an LB film of quite small molecular area was used. In addition, the amount of surface hydroxyl groups on the substrate was found to significantly affect the microstructure of the two-dimensionally packed ceramic spheres. The closest two-dimensional packing was observed on a glass substrate by employing an LB film with a molecular area of 0.03 nm²·molecule⁻¹ at 20°C.     

Vacuum-Assisted Microfluidic Lithography of Ceramic Microstructures

The method to fabricate complex shaped micro-patterned ceramic structures has been developed. Vacuum-assisted infiltrating the suspensions to the micro channels generated by the contact of polydimethylsiloxane mold to the substrate enables simple micro patterning of ceramics with complex structures in a relatively large area in short time. The use of well-dispersed ethanol-based suspensions of solid loading ∼20 vol% plays an important role in a successful pattern formation without defects. The current process, called microfluidic lithography, is applicable to the entire range of ceramic materials which can be processed to colloidal suspension with relatively low viscosity. It is demonstrated that the interdigitated ceramic structures with 50 μm in the width composed of Al₂O₃ and NiO on a Si substrate were fabricated in an area of 5 mm × 5 mm.     

Laminated Object Manufacturing of in-situ synthesized MAX-phase composites

In this work green tapes comprised of TiC and SiC were further processed by lamination, pyrolysis and liquid silicon infiltration. The in-situ synthesis of MAX phase Ti₃SiC₂ by silicon infiltration was investigated and discussed. The synthesis was supported by thermodynamic calculations. The mechanical and microstructural properties of the siliconized composites were studied. The processing route, in combination with Laminated Object Manufacturing (LOM) resulted in the successful fabrication of a three-dimensional gear. The gear showed a defect-free structure with a linear shrinkage of less than 3% relative to the green state. Thus, this approach can be considered as a near-net-shaping process of ceramic components with complex geometries.     

Net Shape Manufacturing of Three-Dimensional SiCN Ceramic Microstructures Using an Isotropic Shrinkage Method by Introducing Shrinkage Guiders

The two-photon cross-linking (TPC) process using ceramic precursors is recognized as a unique fabrication means of real three-dimensional (3D) ceramic microstructures. These structures can be applied to various microscale devices that are used in harsh conditions that demand high strength, high temperature endurance, and good chemical corrosion properties. However, the large shrinkage amount of 3D structures during pyrolysis is a serious limitation to the practical application of these structures; during pyrolysis, asymmetric distortion and shrinkage occur intrinsically. In an attempt to address this, a method is proposed for the precise fabrication of 3D ceramic microstructures that utilize shrinkage guiders to lead to isotropic shrinkage. SiCN ceramic woodpile structures were fabricated to show the efficiency and usefulness of the proposed method. In the results, the woodpiles showed no distortion after pyrolysis.