Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1998-08-10
2001-05-01
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C361S762000
Reexamination Certificate
active
06225570
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a circuit board having an electric component such as a resistive element, an inductor, a capacitor or the like on a surface of a circuit board and manufacturing method thereof, and more particularly, to an electric component-mounted circuit board which is capable of achieving high density equipment of the electric components, and manufacturing method thereof.
BACKGROUND OF THE INVENTION
An electric component-mounted circuit board formed with an electric component such as a resistive element, an inductor, a capacitor or the like by printing on a substrate has been generally used. The electric component comprises electrodes and an electric element such as a resistive element, a dielectric element, or the like. A multilayered circuit board is also generally known, in which an electrically insulating layer and an electrically conductive layer are built up alternately to form multilayered structure. For the circuit boards in these structures, where printing method is used to form the electric components, conventionally, a screen process printing has been commonly adopted. A previously prepared mesh mask is used in the screen process printing. For forming the electric elements, a paste material for forming electric elements, for example, a resistive paste, is applied on the mask and spread by a squeegee. Through the pores of the mask mesh, the paste material sticks to the surface of the circuit board or onto electrodes in a circuit pattern on the surface of the circuit board. If the opening of the pores of the mesh is designed decreased, or if finer mesh is used, a minute printing is done that is intended to reduce the size of the electric element. However, even if the opening of the pores of the mesh can be decreased, decreasing the diameter of the various particles included in the electric element forming paste material is limited. Thus, under the existing circumstances, there is a certain limit for reducing the size of the electric element by the minute printing performed in decreasing the opening of the pores of the mesh. The screen process printing causes irregularity on the surface of the electric element due to the mask mesh. The more the size of the electric element is reduced, the more the roughness of the irregularity affects the electrical characteristic value of the electric element.
An object of the present invention is to provide an electric component-mounted circuit board having a reduced sized electric element than a conventional element and a method of manufacturing same.
Another object of the present invention is to provide an electric component-mounted circuit board which is capable of trimming and has a reduced sized electric element than a conventional element, and a method of manufacturing same.
DISCLOSURE OF THE INVENTION
The electric component-mounted circuit board in accordance with the present invention is formed with a circuit pattern having one or more contact electrodes on a surface of a board made of electrically insulating material. A photoresist film having one or more electric element forming holes is formed on the circuit board by a lithography technology so as to expose at least part of the contact electrode. An electric element forming hole is filled with the electric element forming paste to form an electric element. When the electric element is a resistive element or an inductor, at least part of a pair of electrodes is generally positioned in the electric element forming hole. When the electric element is a capacitor, one contact electrode (lower side electrode) is positioned in the electric element forming hole, and the other electrode (upper side electrode) is formed on the exposed surface of the electric element which is formed by filling the electric element forming paste in the electric element forming hole.
The lithography technology is a technique used in a minute process such in the manufacturing process of a semiconductor. In this technique, a photoresist film is exposed through a mask with a previously prepared pattern (photolithograpy), or, instead of the exposure, irradiation of the electron beams (electron radiation lithography) is performed. The exposed or irradiated part of the photoresist film turns to have solubility in developer different from the other part. If the exposed part becomes easily soluble, the resist film is called a positive-type, and if the exposed part becomes solvent-resistant, it is called a negative-type. The desired resist film is formed by removing the soluble part of the photoresist film by etching, either by wet etching or dry etching. In the present invention, the lithography technology is used to form the electric element forming hole in the photoresist film. In this method, the size of the electric element forming hole can be very small, even a hole having a diameter of 0.1 mm can be accurately formed. Therefore, the electric element, for example, having a size of 0.6 mm ×0.3 mm can be formed, while the minimum size of the electric element formed by screen process printing is 1.6 mm ×0.8mm.
In accordance with the present invention, the size of the electric element formed on the circuit board can be greatly smaller than a conventional element, which can consequently meet the needs of the high density of the circuit pattern on the board. The circuit board in accordance with the present invention can also be used as a core board in a multilayered circuit board for achieving higher density of the multilayered circuit board.
A protective film made of a synthetic resin paste can be provided to covet the electric element forming hole filled with the electric forming paste material for prevention of the characteristics change of the electric element. The protective film can also be used in the multilayered circuit board for prevention of the characteristics change of the electric element. For forming a multilayered circuit board, an insulating layer or a multilayered insulating layer made of a synthetic resin is further laid on the photoresist film, and a circuit pattern is formed on the insulating layer. When the electric element should be a capacitor, the upper side electrode of which can be formed simultaneously with the circuit pattern formed on the insulating layer.
For adjustment or trimming of the electrical characteristics of the electric element formed as above, a laser trimming or the other already known trimming methods can be used. However, in the multilayered circuit board, the insulating layer must have been previously formed with a trimming hole at a position corresponding to the electric element so as to expose at least part of the protective film. The trimming hole can be formed by etching or mechanically formed. Thus, the trimming of the electric element in the multilayered circuit board can be done finally after completion of the fabrication of the multilayered circuit board.
The method of manufacturing the circuit board in accordance with the present invention includes a step of forming a circuit pattern having one or more contact electrodes on the surface of the board made of insulating material, a step of forming a photoresist film on the surface of the circuit board, a step of forming one or more electric element forming holes on the photoresist film using lithography technology so as to expose part of the contact electrode, and a process of forming an electric element in the electric element forming hole by filling an electric element forming paste.
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Higashi Koji
Ishiyama Ichiro
Nagare Ichiro
Ohara Yozo
Yamazaki Morikatsu
Gaffin Jeffrey
Kokuriku Electric Industry Co., Ltd.
Norris Jeremy
Rankin, Hill Porter & Clark LLP
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