The present invention relates to forming a charge-containing element, which is useful as a capacitor on a printed circuit board.
Ceramic oxide layers are diverse in their properties. Apart from their unusually high mechanical strength, high wear and abrasion resistance, and high corrosion resistance, they can be considered to be dielectric, ferroelectric, piezoelectric, or optoelectronic materials. They can also be utilized in both electrical and thermal insulation applications. These ceramic oxides can be crystalline or amorphous.
Layers of ceramic materials can be manufactured using physical vapor deposition (PVD) and chemical vapor deposition (CVD), laser ablation, dip and knife coating of a ceramic precursor material, and metallo-oxide decomposition (MOD) as shown by Mir et al in commonly-assigned U.S. Pat. No. 4,880,770.
However the above-mentioned processes are time consuming, involving numerous steps for realization of the final product. In addition, the above mentioned processes are not discreet enough to selectively deposited the dielectric materials in the desired configuration or location.
Formation of dielectric material normally requires high temperature processing. This high temperature processing restricts the choice of substrates that can be selected for use. Capacitors are multilayer coatings comprised of an arrangement of conductive, dielectric, and conductive layers in sequence. There is a need for forming dielectric materials on a substrate in many applications such as capacitive devices. Capacitors are essentially materials with high dielectric constants. Dielectric (which is essentially electrically non-conducting) characteristic of ceramic materials are well known and getting increasing importance as the field of solid state electronics continues to expand rapidly. The principal applications for ceramic dielectrics are as capacitive elements in electronic circuits and as electrical insulation. For these applications, the properties of most concern are the dielectric constant, dielectric loss factor, and dielectric strength. The principal characteristics of a capacitor are that an electric charge can be stored in that capacitor and the magnitude of the charge which can be stored is dependent primarily on the nature of the material, grain size, and the impurity distribution at the grain boundaries.
As mentioned earlier, there are problems with conventional deposition methods. It is felt that the method of delivery of the metallo-organic precursor requires the development a novel approach in order to reduce the time required to manufacture dielectric components and reduce the waste involved during conventional manufacturing processes.
Ink jet printing is commonly utilized for delivery of liquid ink onto a receiver. An ink jet printhead made from a piezoelectric material is used to selectively eject ink droplets onto a receiver to form an image. Within the printhead, the ink may be contained in a plurality of channels and energy pulses are used to actuate the printhead channels causing the droplets of ink to be ejected on demand or continuously, through orifices in a plate in an orifice structure. The delivery of metallo-organic precursor material in a liquid state can be made utilizing ink jet printers utilizing suitable printheads onto selected substrates.
In one representative configuration, a piezoelectric ink jet printing system includes a body of piezoelectric material defining an array of parallel open topped channels separated by walls. In the typical case of such an array, the channels are micro-sized and are arranged such that the spacing between the adjacent channels is relatively small. The channel walls have metal electrodes on opposite sides thereof to form shear mode actuators for causing droplets to expel from the channels. An orifice structure comprising at least one orifice plate defining the orifices through which the ink droplets are ejected, is bonded to the open end of the channels. In operation of piezoelectric printheads, ink is directed to and resides in the channels until selectively ejected therefrom. To eject an ink droplet through one of the selected orifices, the electrodes on the two side wall portions of the channel in operative relationship with the selected orifice are electrically energized causing the side walls of the channel to deflect into the channel and return to their normal undeflected positions when the applied voltage is withdrawn. The driven inward deflection of the opposite channel wall portions reduces the effective volume of the channel thereby increasing the pressure of the ink confined within the channel to force few ink droplets, 1 to 100 pico-liters in volume, outwardly through the orifice. Operation of piezoelectric ink jet printheads is described in detail in U.S. Pat. Nos. 5,598,196; 5,311,218; 5,365,645, 5,688,391, 5,600,357, and 5,248,998.
It is an object of the present invention to provide an improved method of making a patterned charge-containing element.
It is another objective of the present invention to provide a method of depositing and patterning a dielectric material on a conductive portion of a substrate to form a patterned charge-containing element.
In one aspect, these and other objects of making patterned charge-containing elements are achieved by a method comprising the steps of:
(a) depositing and patterning a dielectric material on a surface by a precision precursor delivery head wherein the dielectric material includes a metallo-organic component and a liquid component; and
(b) thermally decomposing by laser light the deposited dielectric material to substantially evaporate the liquid component to cause the metallic portion of the metallo-organic material to react with oxygen causing the dielectric material to have charge-holding properties wherein the dielectric material includes a metallo-organic component and a liquid component.
It is a further object of the present invention to provide a method of depositing and patterning by a precision precursor delivery head, which responds to electrical signals to provide the dielectric material at predetermined positions.
It is still a further object of the present invention to provide a conductive portion over a substrate and forming the patterned dielectric material on such conductive portions.
It is still another object of the present invention to provide a method of converting the dielectric material at predetermined positions to electrically conductive material using a Nd-YAG laser source having wavelength 1.06 xcexcm.
The present invention is particularly suitable to provide a dielectric layer for a multilayer capacitor, flexible capacitor, capacitor integrated to circuit boards, camera body, cellular phone, personal digital assistant, pace maker, hand held electronic devices, and related components.
This invention provides a convenient way to have fully completed solid state reactions to produce desired chemistries in material layer. It is easy to control various crystallographic phases of the material by simplified doping methods.
It is an advantage of the present invention that the dielectric layer can be made using a low cost ink jet printer, which permits controlled and selective delivery of the metallo-organic precursor having high degree of thickness uniformity, and ability to deposit in a cost effective manner.
This invention overcomes many of the problems that are associated with conventional methods of fabricating printed circuit boards, multilayer capacitors, flexible capacitors, capacitors integrated onto circuit boards, and protective coatings on metals, alloys, polymers, organics, inorganics, composites, glasses, paper, photographic film, magnetic media, or ceramic substrates or combinations thereof both flexible and rigid in form.