E.C. Folk

Bio: E.C. Folk is an academic researcher from University of Arkansas. The author has contributed to research in topics: Microvia. The author has an hindex of 1, co-authored 1 publications receiving 58 citations.

Fabrication of microvias for multilayer LTCC substrates

Abstract: Advances in screen printing and photoimageable paste technologies have allowed low-temperature cofired ceramic (LTCC) circuit densities to continue to increase; however, the size of vias for Z-axis interconnections in multilayer LTCC substrates have been a limiting process constraint. In order to effectively exploit the 50-100-/spl mu/m line/spacing capabilities of advanced screen printing and photoimageable techniques, microvia technologies need to achieve 100 /spl mu/m and under in diameter. Three main steps in fabrication of microvias include via formation, via metallization or via fill, and layer-to-layer alignment. The challenges associated with the processing and equipment for the fabrication of microvias are addressed in this paper. Microvias down to 50 /spl mu/m in diameter with spacings as small as 50 /spl mu/m are achieved in 50-254-/spl mu/m-thick LTCC tape layers through the use of a mechanical punching system, whereas the minimum size of 75-/spl mu/m via/spacing is obtained using a pulse laser-drilling system in the LTCC tape layers with the same thicknesses as those for the punching test. The quality of punched microvias and laser-drilled microvias will be presented as well. Layer-to-layer alignment is crucial to the connection of vias in adjacent LTCC tape layers. Through a stack and tack machine with a three-camera vision system and an adjustable precision stage, less than 25-/spl mu/m layer-to-layer misalignment is achieved across a 114.3/spl times/114.3 mm (4.5/spl times/4.5 in) design area. In a six-layer LTCC test substrate (152/spl times/152/spl times/0.762 mm), microvias of 50, 75, and 100 /spl mu/m in diameter are successfully fabricated without the use of via catch pads. The cross section of fired microvias filled with silver conductor pastes at various locations of this substrate demonstrates a minor layer-to-layer misalignment in both X and Y directions across the substrate.

Overview on fabrication of three-dimensional structures in multi-layer ceramic substrate

Abstract: Three-dimensional structures in a multi-layer ceramic substrate are important in realizing ceramic-based meso- and micro-systems. During lamination and/or co-firing, three-dimensional structures, especially those with suspended structures, tend to deform and sag due to the intrinsic nature of the green (un-fired) ceramic material. Fabrication of three-dimensional structures with well-controlled dimensional stability and mechanical integrity remains a challenge. This paper discusses the challenges in fabricating structures in a multi-layer ceramic substrate. An overview is provided of the current state of the art in patterning and lamination techniques for the fabrication of these three-dimensional structures.

Overview on low temperature co-fired ceramic sensors

Abstract: Low Temperature Co-fired Ceramics (LTCC) is one of the microelectronic techniques. This technology was initially developed as an alternative to Printed Circuit Boards (PCB) and classical thick-film technology, and it has found application in the fabrication of multilayer ceramic boards for electronic devices. Fast and wide development of this technology permitted the fabrication of 3D mechanical structures and integration with various different processes. Thanks to this, LTCC has found application in the manufacturing of various microelectronic devices. This paper presents an overview on LTCC technology and gives a detailed summary on physical quantity sensors fabricated using LTCC technique.

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

Abstract: 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.

Tunable Microwave Phase Shifters Using LTCC Technology with Integrated BST Thick Films

Abstract: Low temperature co-fired ceramic (LTCC) reflection and delay line type microwave phase shifters utilizing completely integrated barium strontium titanate (BST) varactors are investigated. Dielectric properties of the screen printed BST paste in 1–8 GHz frequency range are presented. Sintering temperature and time were varied and their effect on the dielectric properties of the film was studied. Phase shifters were sintered at 875°C for 25 min in line with a standard LTCC sintering profile. The relative phase shift of the reflection and delay line type phase shifters were found to be 5 and 11.5° at 2.5 GHz with applied bias field strength of 8 V/μm, respectively.

Laser Prototyping of Microwave Circuits in LTCC Technology

Abstract: In this paper, a process for direct laser structuring of microwave circuits in low-temperature co-fired ceramic (LTCC) technology is reported. An efficient alternative to screen printing is proposed for prototyping circuits by laser patterning the conductors on the unfired tape. A line width and gap of 50 ?m are achieved with laser machining. A range of samples has been studied using a scanning electron microscope in order to optimize the process parameters. The surface roughness of laser-treated samples is measured with a surface profiler and compared with the untreated samples. A method of creating microvias and trenches in thick LTCC substrate is also demonstrated. For 254 ?m thick green tape, vias with a diameter and separation of 50 ? m are realized along with trenches having a width as small as 30 ?m. The method of optimizing the laser machining process is described in detail. A band-stop mushroom resonator and a microstrip ring resonator filter are fabricated and their results compared against simulations.