Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-04-14
2003-04-22
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S117200
Reexamination Certificate
active
06551753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a preparation of a printed wiring board utilizing an electrophotographic reverse developing method which uses a material to be developed having a metal conductive layer and a photoconductive layer in this order on at least one surface of an insulating substrate, particularly to a liquid developing method which gives a resist image by applying a liquid toner developing treatment onto the material to be developed having a static latent image.
2. Prior Art
A method for making a printed wiring board is roughly classified into two methods of the subtractive method and the additive method. The subtractive method is a method in which a resist layer is formed on a laminated board to which a conductive layer such as copper, etc. is provided on an insulating substrate, and the conductive layer not covered by the resist layer is removed by etching. The additive method is a method in which a conductive layer is formed only at a wiring pattern portion on an insulating substrate. In addition to the above, it has been proposed a wiring transfer method in which a resist image is provided on a conductive substrate by a plate resist, metal plating is applied to the conductive substrate other than the resist image to form a metal wiring pattern, and then, after the resist image is removed, only the metal wiring pattern is transferred to the insulating material.
Preparation of a resist layer utilizing an electrophotographic method is carried out as mentioned below. A photoconductive layer is provided on a copper-clad laminated board, and after uniformly charging the surface of the photoconductive layer in a dark place, exposure is carried out according to a wiring pattern whereby charging at the exposed portion disappears and an electrostatic latent image can be formed. The electrostatic latent image is subjected to toner developing treatment and fixing to form a toner image, and by using the toner image as a resist, the photoconductive layer other than the toner image portion is dissolved and removed to prepare a resist image of a metal conductive layer comprising the toner image and the photoconductive layer. Dissolution and removal of the unnecessary portion of the metal conductive layer and the subsequent preparation step of the printed wiring board can be carried out in the same manner as in the conventional procedure.
When the electrophotographic method by the reverse developing method (hereinafter simply referred to as “an electrophotographic method”) is used, procedure is carried out that the surface of a photoconductive layer is charged in a dark place and forming an electrostatic latent image is formed by vanishing a charge at the exposed portion by exposing an image portion, and then, fine toner particles having the same polarity as those of the charged electric charge are adhered to the exposed portion, i.e., to a portion at which the electric charge is vanished. At this time, a conductive member called a developing electrode is provided opposed to the surface of an electrostatic latent image, and a bias voltage with the same polarity is applied to the electrode whereby adhesion of the toner particles to the exposed portion is promoted and a toner image with a high image quality can be obtained.
A method of preparing a resist layer to the both surfaces of a substrate utilizing the electrophotographic method has been disclosed in Japanese Provisional Patent Publication No. 224541/1994, and it is possible to form toner images on the both surfaces by simultaneously developing both surfaces of a laminated board in which a metal conductive layer and a photoconductive layer are provided on the both surfaces of an insulating substrate.
At present, in a progress of high density preparation of a printed wiring board, a printed wiring board having a lot of conductive fine pores called through holes provided to respective substrate with a multi-layered structure has been prepared. In this case, circuits formed on the both surfaces of the substrate are connected by the through holes. Thus, not only precision of the circuit itself formed on the substrate but also precision of formed positions of the circuits on the both surfaces relative to the through holes as a standard, i.e., positional precision prior to formation of the resist film are required.
Moreover, according to the recent trend of making light, thin, short and compact, or variety of electronic devices, in a printed wiring board, it is now required to make it with high density and within a short period of time. Also, a direct drawing method by the use of data from a computer using a flat bed scanning exposure device which uses laser beam or light emitting diode in place of the conventional surface exposure drawing method using a photomask has now been investigated. An application of an electrophotographic material has been investigated as a resist material.
As a flat bed scanning exposure device to be used for preparing a resist film utilizing the electrophotographic method, it is possible to use a device which uses various kinds of lasers or light emitting diode as a light source. During exposure, it is carried out by moving at least either one of an optical system or a material to be exposed placed on a flat bed.
When a both-surfaces printed wiring board is to be prepared by using the flat bed scanning exposure device to be used in the above-mentioned direct drawing method, there may be mentioned a method in which one surface of a laminated board is statically charged and exposed, then the laminated board is turned over, and the other surface of the laminated board is statically charged and exposed to effect both surfaces exposure, and toner development is carried out on the both surfaces simultaneously, or a method in which one surface of a laminated board is statically charged, exposed and subjected to toner development, and then, the other surface of the same is similarly treated to form a resist pattern. In the former method, an electrostatic latent image is contacted with the flat bed after turn over so that the electrostatic latent image is likely disturbed whereby any measure to prevent such a disturbance is required. To the contrary, in the latter method, a non-developed surface is not statically charged at the time of toner development so that there is a possibility of causing stain at the non-developed surface due to an excess amount of the toner. However, the latter method is capable of processing the surface to which an electrostatic latent image is formed without contacting any material. Thus, the latter method (hereinafter referred to as “a one-surface stepwise developing system”) has been investigated nowadays as a process for producing a both-surfaces printed wiring board by the direct drawing method.
Moreover, when a both-surfaces printed wiring board having a through hole(s) is to be prepared, depending on the size of a diameter of the through hole(s) and a thickness of a material to be developed, a problem occurs that toner is electrodeposited on a non-developed surface side of a penetrated through hole(s) by a bias voltage to cause a defect at the time of liquid toner development by carrying out the above-mentioned one-surface stepwise developing system.
Also, in the above-mentioned one-surface stepwise developing system, when a thin copper-clad laminated board having a thickness of 0.4 mm or less is used as a substrate, the substrate bends between electrodes (which also varies depending on the size of the material to be developed) so that the change in the distance of gaps between the electrode and the substrate causes a problem. At this time, a bottom side of the substrate is contacted with rolls to move the substrate so that a non-developed surface statically charged is contacted with the rolls whereby the statically charged state of said non-developed surface is disturbed. Also, a liquid toner migrated from the development surface side to the non-development surface side adheres to said non-development surface ununiformly so that s
Hyodo Kenji
Inoue Noritaka
Irisawa Munetoshi
Kaneda Yasuo
Komuro Toyokazu
Dote Janis L.
Manelli Denison & Selter PLLC
Mitsubishi Paper Mills Limited
White, Jr. Paul E.
LandOfFree
Liquid developing method of printed wiring board does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid developing method of printed wiring board, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid developing method of printed wiring board will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3003575