Printed circuit board having through-hole protected by barrier and method of manufacturing the same

#This application is based upon and claims benefit of priority of Japanese Patent Application No. 2002-107728 filed on Apr. 10, 2002, the content of which is incorporated herein by reference.

#1. Field of the Invention

#The present invention relates to a printed circuit board on which various circuit elements are mounted and to a method of manufacturing such a printed circuit board.

#FIG. 1 is a plan view showing a part of a substrate constituting a printed circuit board according to the present invention;

#FIG. 2 is a plan view showing the substrate on which a barrier preventing dampproof liquid from flowing into a through-hole is formed;

#FIG. 3 is a plan view showing the substrate on which a chip-capacitor is mounted;

#A preferred embodiment of the present invention will be described with reference to FIGS. 1-6. First, a manufacturing process of a printed circuit board according to the present invention will be described. Then, a structure of the printed circuit board will be briefly described because the structure is easily understood based on its manufacturing process. FIGS. 1-4 sequentially show the process of manufacturing the printed circuit board 1, and FIG. 5 shows a cross-sectional view of the printed circuit board 1, taken along line V-V shown in FIG. 4. Those drawings only show a part of the printed circuit board 1 relevant to the present invention.

#The printed circuit board 1 is made by printing various circuits on both surfaces of a substrate 10 and mounting various circuit elements thereon. The printed circuit board 1 is manufactured in known processes except for processes of forming a barrier and applying dampproof liquid, which will be described below in detail. As shown in FIG. 1, a through-hole 2 is formed through the substrate 10, and a pair of copper pads 101, 102 is printed on a front surface 11 of the substrate 10. The substrate 10 is made of a board such as a glass-epoxy-resin compound board. An inside surface of the through-hole 2 and areas around its front and rear openings are plated with a metallic material 21, as shown in FIG. 4. The pair of pads 101, 102 is positioned with a predetermined space apart from the through-hole 2. The predetermined space is made relatively small to mount many circuit elements in a limited space of the substrate 10.

#As shown in FIG. 2, an outer circular bank 41 and an inner circular bank 42 surrounding the through-hole 2 are formed on the front surface 11 of the substrate 10. Those circular banks 41, 42 serve as a barrier 4 for preventing dampproof liquid or paste, which is coated in a later step on a circuit element to be connected to the pads 101 and 102, from flowing into the through-hole 2. The circular banks 41, 42 are printed by screen-printing together with other patterns including marks and characters 49 in a single process. The screen-printing is a known printing method, in which a silk screen having fine meshes is masked to leave desired patterns, and ink paste substantially composed of epoxy resin and white pigment is forcibly squeezed toward the silk screen. In this manner, the desired patterns and characters are simultaneously printed. The printed marks and characters 49 indicate a position where a 75-pF capacitor is to be connected.