Patent Publication Number: US-2012024573-A1

Title: Printed circuit board and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0073639 filed on Jul. 29, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printed circuit board and a manufacturing method thereof, and more particularly, to a printed circuit board and a manufacturing method thereof capable of preventing plating from being performed on dummy portions thereof during a plating process. 
     2. Description of the Related Art 
     According to the related art, two surfaces of a substrate are coated with a photo solder resists (PSR) by using a screen printing method and a roll printing method. The PRS may be patterned on the substrate through exposure and development so that the PRS is formed only on desired portions of the substrate. 
     However, since a clamp and an absorption pad for transporting the substrate after a screen printing process is performed are attached to edge portions of the substrate when the PSR is patterned thereon, dummy portions in which the PSR is not formed are formed at the edge portions of the substrate. 
     Since the PSR is not formed on the dummy portions, plating is performed up to the dummy portions of the edge portions of the substrate during a plating process, thereby causing an increase in manufacturing costs. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides a manufacturing method of a printed circuit board capable of preventing plating from being unnecessarily performed on dummy portions during a plating process by masking resists on the dummy portions corresponding to non-active regions of a substrate using an inkjet printing method 
     According to an aspect of the present invention, there is provided a manufacturing method of a printed circuit board, including: preparing a substrate having active regions and non-active regions, the non-active regions being formed on edges thereof; printing resists on dummy portions corresponding to the non-active regions of the substrate by using an inkjet printingmethod; curing the resists; and performing plating on the active regions of the substrate. 
     The manufacturing method may further include selecting the dummy portions formed on the substrate by imaging the substrate before printing the resists. 
     The resists may be photo-curable resists or heat-curable resists. 
     The plating may be an Au plating. 
     The manufacturing method may further include, prior to the performing of plating on the active regions of the substrate, printing theresists on dummy portions of another surface of the substrate on which the resists are not formed; and curing the resists. 
     The printing of the resists may include simultaneously forming the resists on the dummy portions formed on both surfaces of the substrate. 
     The printing of the resists may include pre-curing the resists while printing the resists. 
     According to another aspect of the present invention, there is provided a printed circuit board, including: a substrate having active regions and non-active regions, the non-active regions being formed on edges thereof; and resists printed on dummy portions corresponding to the non-active regions of the substrate by using an inkjet printing method. 
     The resists may be photo-curable resists or heat-curable resists. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a flow chart schematically showing a resist forming process according to an exemplary embodiment of the present invention; 
         FIGS. 2A to 2C  are process flow charts schematically showing a resist forming process according to an exemplary embodiment of the present invention; 
         FIG. 3  is a plan view showing a substrate having resists formed thereon according to an exemplary embodiment of the present invention; and 
         FIGS. 4A and 4B  are cross-sectional views showing a resist printing process on the substrate according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the shape, size, and the like, of components are exaggerated for clarity. 
       FIG. 1  is a flow chart schematically showing a resist forming process according to an exemplary embodiment of the present invention, and  FIGS. 2A to 2C  are process flow charts schematically showing a resist forming process according to an exemplary embodiment of the present invention. 
     Hereinafter, a manufacturing method of a printed circuit board according to an exemplary embodiment of the present invention shown in  FIG. 1  will be described according to manufacturing process shown in  FIGS. 2A to 2C . 
     According to an exemplary embodiment of the present invention, in operation (S 10 ), a substrate having pads formed on one surface thereof and having first resists formed on remaining portions thereof, excluding the pads, so that plating is performed only on the pads, is prepared. The first resists are formed on portions of the substrate, excluding the pads, in order that plating may be performed on the pads. 
     In operation (S 20 ), second resists are formed on dummy portions of the substrate using an inkjet printing method. A process of determining the dummy portions is required in order to form the second resists. In order to determine the dummy portions, an imaging process may be performed. The dummy portions of the substrate may be determined in consideration of the contraction and the deformation of the substrate through the imaging process. 
     On the substrate, the dummy portions, corresponding to non-active portions on which circuits are not to be formed refer to portions required for manufacturing the substrate. For example, the dummy portions may be portions to which a clamp for transporting the substrate and an absorption pad are attached. 
     After the second resists are formed on the substrate using the inkjet printing method, the second resists are cured in operation (S 30 ). The second resists may be photo-curable resists or thermo-curable resists. Accordingly, the second resists may be cured by light or heat, according to the characteristics thereof. 
     In operation (S 40 ), a plating process is performed on the substrate having the first and second resists formed thereon. In particular, the plating process may be a gold (Au) plating process. In the case that gold is unnecessarily plated on the dummy portions, high manufacturing costs may be incurred. 
     According to an exemplary embodiment of the present invention, the second resists are formed on the dummy portions of the substrate to prevent gold from being unnecessarily plated thereon, such that manufacturing costs may be reduced. 
     Hereinafter, a manufacturing process of a printed circuit board according to an exemplary embodiment of the present invention will be described with reference to  FIGS. 2A to 2C . 
     Referring to  FIG. 2A , according to an exemplary embodiment of the present invention, a substrate, having pads  110  formed on a surface thereof and having first resists  130  formed on portions of a substrate, excluding portions on which the pads  110  are formed, so that plating may be performed on surfaces of the pads  110  is prepared. 
     According to an exemplary embodiment of the present invention, the first resists  130  may be formed as, for example, photo solder resists (PSRs); however the first resists  130  are not limited thereto. The first resists  130  serve to prevent portions of the substrate from being plated, with the exception of the pads  110 , in active portions in which circuits of the substrate are formed. 
     The first resists  130  which may be photo solder resists are formed on the substrate  100 , and may be selectively cured in consideration of a pattern to be cured. For example, the portions of the substrate, other than the pads  110 , are selectively cured using a method such as an exposure method, or the like. 
     The photo solder resists formed on the pads  110  of the substrate  100  are selectively removed, such that the pads  110  are exposed 
     The substrate  100 , on which only the pads  110  are exposed, and having the first resists  130  formed on the remaining portions thereof is prepared, such that when a plating process is performed on the substrate  100 , only the pads  110  of the substrate  100  may be plated. 
     Referring to  FIG. 2B , second resists  150  are formed on the outermost dummy portions of the substrate  100 . 
     The first resists  130  may not be formed on the dummy portions corresponding to non-active regions of the substrate  100 . 
     Accordingly, the second resists  150  are formed such that the dummy portions of the substrate  100  are not plated. The second resists  150  may be formed by using the inkjet printing method. 
     The selection of dummy portions is required in order to apply the second resists  150  to the substrate  100 . 
     Dummy portions indicate non-active regions of the substrate in which circuits are not to be formed. Dummy portions may also be regions required for attaching a clamp or an absorption pad, in a substrate manufacturing process. 
     Dummy portions indicate the non-active regions of the substrate formed at the edge portions of the substrate. 
     Meanwhile, according to an exemplary embodiment of the present invention, among the edge portions of the substrate, the second resists  150  may not be formed on a test terminal for testing the substrate, a plating deviation prevention pattern for preventing plating deviation during the plating of the substrate, a transport hole for transporting the substrate, and a printing target on which printing, such as screen printing or the like, will be performed. 
     Since the test terminal, the plating deviation prevention pattern, the transport hole, and the printing target need to be active portions in the manufacturing and testing process of the substrate, the second resists maybe not formed on these portions. 
     According to an exemplary embodiment of the present invention, an imaging process is used in order to select the regions in which the second resists  150  are to be formed on the substrate  100 . 
     First, the substrate  100 , having the first resists  130  formed on portions thereof, other than the pads  110 , is prepared. The first resists may be PSRs. The substrate  100  is imaged by an image apparatus such as a camera, or the like. 
     For example, an image of the substrate is converted into a printable bit map file format. Then, a substrate device is arranged to measure a change in the size of the substrate generated in passing through a previous process, thereby performing a conversion that increases or decreases the size of the image of the bit map file according to the substrate. 
     Through this conversion, second resist application regions may be selected by considering deformation due to the manufacturing process of the substrate. Thereafter, the second resists  150  may be applied to the selected second resist application regions. 
       FIG. 2C  is a view showing a curing process of the second resists  150  according to an exemplary embodiment of the present invention. 
     The second resists  150 , formed using the above-mentioned method are cured according to the characteristics of a material of which they are composed. 
     According to an exemplary embodiment of the present invention, the second resists  150  may be thermo-curable resists or photo-curable resists; however the present invention is not limited thereto. When the second resists  150  are the thermo-curable resists, the second resist  150  may be cured by applying heat thereto. Alternatively, when the second resists  150  are the photo-curable resist, the second resists  150  may be cured by being exposed to light. 
     According to an exemplary embodiment of the present invention, since the second resists  150  are applied by using the inkjet printing method, a removal process thereof is not required. The formed resists may be only cured to be used in the next process. 
     Since the second resists  150  are applied using the inkjet printing method, second resist application regions in which the second resists  150  are to be formed may be accurately selected and a removal process thereof is not required, and thus, the manufacturing efficiency of the printed circuit board may be improved. 
     Then, a plating process is performed on the substrate on which the first and second resists  130  and  150  are formed. For example, a gold plating process may be performed on the substrate. 
     When the gold plating process is performed, gold is not plated on the regions on which the resists are formed, thereby preventing the gold from being plated on portions not requiring gold plating, such that manufacturing efficiency may be improved and manufacturing costs may be lowered. 
       FIG. 3  is a plan view showing a substrate having resists formed thereon according to an exemplary embodiment of the present invention. 
     In  FIG. 3 , the second resists  150  are formed on the substrate  100  and particularly, the second resists  150  are not formed in predetermined active portions among the edge dummy portions of the substrate. 
     Since the imaging process is performed prior to printing the second resists  150 , the substrate may be manufactured by considering the deformation of the substrate during the manufacturing of the substrate. Therefore, the reliability of the substrate may be improved. 
     In addition, since the resists are formed using the inkjet printing method, resists may be accurately formed in desired portions as well as the resists may be formed excluding, predetermined active portions in the manufacturing process of the substrate, for example, the test terminal, the printing target, the plating deviation prevention pattern, the substrate transport hole, and the like. 
     Further, since the resists are partially formed, a process of removing the resists formed at the unnecessary portion after the resists are cured is not required, thereby significantly simplifying the process. 
       FIGS. 4A and 4B  are cross-sectional views showing a process of printing the resists on the substrate according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4A , resists  250 ′ are discharged from an inkjet head  260  to a substrate  200  to form second resists  250  on the substrate  200 . 
     According to an exemplary embodiment of the present invention, a pre-curing unit  270  may be provided next to the inkjet head  260 . After the resists  250 ′ are discharged from the inkjet head  260 , the pre-curing unit  270  may pre-cure the second resists  250  by passing on the resists  250 ′. 
     The second resists  250  are formed while being cured through the pre-curing process, such that the resist may be stably formed. 
     In the case of  FIG. 4A , the second resists are formed on one surface of the substrate, the substrate is cured, the second resists are formed on another surface of the substrate, and then the substrate is cured. 
     According to another exemplary embodiment of the present invention, a method in which the second resists are simultaneously formed on both surfaces of the substrate and both surfaces are simultaneously cured to simplify a manufacturing process of the substrate is provided. 
       FIG. 4B  shows a process in which the second resists  250  and  251  are simultaneously formed on both surfaces of the substrate  200 . 
     The second resists  250 ′ and  251 ′ are simultaneously discharged through inkjet heads  271  and  273  horizontally moved with reference to the substrate  200 , and pre-curing units  261   a ,  261   b ,  263   a , and  263   b  passing through regions through which the inkjet heads have passed may pre-cure the discharged resists. 
     According to an exemplary embodiment of the present invention, the pre-curing units  261   b  and  263   a  are formed on both sides of the inkjet heads  271  and  273  to pre-cure the resists formed at the regions through which the inkjet heads have passed along a direction thereof. 
     Similar to this, the second resists  250  are simultaneously formed on both surfaces of the substrate  200 , such that the process of manufacturing the substrate may be simplified and the manufacturing time thereof may be shortened. 
     As set forth above, according to the exemplary embodiments of the present invention, the resists are masked on the dummy portions corresponding to the non-active regions of the substrate to thereby prevent plating from being unnecessarily performed on the dummy portions during the plating process. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.