POWER CIRCUIT BOARD AND MANUFACTURING METHOD

Abstract: The circuit board comprises an insulating board (2) of insulating material and an electric circuit formed of etched copper layers (3,4) provided on the outer surfaces of it. A shorting bar (5) as a high-current conductor is placed, through a burring process, on the copper layer (3) which conduct large amounts of current, and an electric component is placed on the burred portion and screwed fixedly with a bolt (7).

Description: Technical Field This invention relates to a circuit board device for a magnetics circuit for use in wiring an electric circuit which handles a high current, and a method of manufacturing the same. Background Art In recent years, a so-called printed circuit board, in which an electric circuit pattern is formed by the use of a copper foil printed for wiring on the front surface of an insulator blank in the shape of a thin plate, has been extensively utilized for connecting an electric circuit. In a printed circuit board of this type, the electric circuit pattern is prepared by a copper foil etching process, and therefore the thickness of the copper foil to be used is limited. That is, the cross-sectional area of each copper foil portion to constitute the electric circuit is subject to a certain limitation with regard to the limited area of the circuit board. Accordingly, a printed circuit board of this type is generally used for a low-current signal processing circuit. In a case where a magnetics circuit which handles a high current is to be formed flat, use is made of a circuit board device of the so-called laminated type wherein conductor pieces to serve as portions for conducting currents are punched and then bonded on an insulating plate, and prescribed power components are properly mounted on the circuit board device for the magnetics circuit, thereby to construct the magnetics circuit. Each of the two circuit board devices stated above has merits and demerits. By way of example, with the printed circuit board of the former, fabrication is easy but the thickness of the copper foil is limited because of the use of the etching process. Moreover, when the former is applied to a high-current circuit, problems arise due to the current capacity of the current conducting portion, the generation of heat ascribable to current conduction, etc. With the latter circuit board device for the magnetics circuit wherein the punched conductor pieces are bonded, the foregoing problems can be solved but labor is required for the steps of punching and bonding the conductor pieces. Moreover, when an electric circuit in which a low current and a high current coexist is to be formed, the steps become still more complicated (see e.g. EP-A-0 185 773). This is a problem which is difficult to solve in terms of cost. Disclosure of the Invention The present invention has been devised in order to solve such problems, and its object is to provide a circuit board device for a magnetics circuit, which is capable of forming conduction paths of large current capacities in a limited area. Another object of the present invention is to provide a method of manufacturing a circuit board device for a magnetics circuit, which is easy to fabricate and low in cost. According to the present invention, there is provided a circuit board device for a magnetics circuit, characterized by a printed circuit board in which circuit patterns of copper foil portions are formed by an etching process on plate surfaces of an electric insulator blank that is formed with openings provided in the copper foil and penetrating both the surfaces, and short bars fastened to the copper foil portions including the openings and which serve as conductor pieces for the high currents, wherein through-holes somewhat smaller in diameter than the openings are provided in positions of the short bars corresponding to the openings, and peripheral end parts of the through-holes are bent into the openings and are burred to secure mechanical and electrical connections. In addition, according to the present invention, there is provided a method of manufacturing a circuit board device for a magnetics circuit, comprising the steps of forming a solder layer on an outer surface of each copper foil portion to which the short bar is to be fastened, placing the corresponding short bar on the solder layer and then bringing the former into pressing contact with the latter by means of a heating roller, and mechanically fixing the short bar by the burring in the openings which penetrate both surfaces of the printed circuit board. Thus, with the circuit board device for a magnetics circuit and the manufacturing method therefor according to the present invention, the short bar to serve as the conductor piece for a high current is clinched by the burring onto the copper foil portion that is required to conduct the high current, and the terminal portion of an electric component for the high current can be screwed into the burred hole. The effects are that the current capacity of the current conduction portion can be enlarged and that fear of losses such as by heat generation is eliminated. In addition, according to the present invention, an electric circuit for a high current and an electric circuit for a low current can be disposed on both surfaces of the printed board and then connected through the burred portions. The effect is that the formation of an electric circuit in which the high current and the low current coexist is facilitated. Brief Description of the Drawings Fig. 1 is a view of the upper surface of a printed board showing an embodiment of the present invention, Fig. 2 is an explanatory view of the lower surface pattern of the printed board as seen through this printed board from above, Fig. 3 is a plan view of an example of a short bar, and Fig. 4 shows enlarged sectional views each illustrating the connection between a copper foil portion and an electric component. Best Mode for Carrying Out the Invention An embodiment of the present invention will now be described in detail with reference to the drawings. In Figs. 1 and 2, numeral 2 denotes an insulating plate which is an insulator blank in the shape of a thin plate and which serves as the base material of a printed board 1. Copper foil portions 3 and 4 formed into predetermined shapes by an etching process are respectively fastened on the upper and lower surfaces of the insulating plate. Here the copper foil portions 3 on the upper surface serve as a high-current circuit, while the copper foil portions 4 on the lower surface serve as a signal current circuit or a low-current circuit, and they function as leads for electrically connecting various electric components to be subsequently mounted on the printed board 1. Fig. 3 is a plan view showing an example of the shape of a short bar 5 which functions as a conductor for high currents. The short bar 5 is formed by punching a copper plate, for example, having a thickness of 1 mm into the same shape as that of the corresponding copper foil portion 3, and the end parts thereof are provided with through-holes 51 each having a diameter smaller by a predetermined value than that of an opening 31 which is provided in the copper foil portion 3 as well as the insulating plate 2 while penetrating both surfaces of the printed board 1. In splicing the short bar 5 to the corresponding copper foil portion 3, the upper surface of the copper foil portion 3 is coated with a solder, the short bar 5 is placed on the resulting upper surface of the copper foil portion 3, and the short bar 5 is brought into pressing contact with the solder layer by a heating roller. After such splicing, each through-hole 51 at the end part of the short bar is machined with respect to the opening 31 of the printed board 1 in such a manner that the peripheral end part of the through-hole 51 is bent into the opening 31 and is burred, whereby the short bar 5 is mechanically clinched and electrically coupled to the copper foil portion 3. Fig. 4 shows enlarged sectional views each illustrating the connection between the copper foil portion 3 thus subjected to clinching and an electric component for a high current. Fig. 4(a) depicts the state in which the electric component is mounted on the lower surface side of the printed board 1, while Fig. 4(b) depicts the state in which the electric component is mounted on the upper surface side thereof. In Fig. 4(a), the terminal portion 6 of the electric component is fixed to the clinched short bar 5 by the machined hole 52 of the latter using a bolt 7 as well as a nut 8, thereby establishing the mechanical and electrical connections of the terminal portion with the printed circuit board 1. In Fig. 4(b), the terminal portion 6 is clamped and fixed by a bolt 9 threadably engaged with a machined hole 53 formed by threading the portion of the through-hole 51 of the short bar 5 after clinching. Numeral 71 denotes a washer, and numeral 72 designates a spring washer. In this embodiment thus constructed, the electric circuit for a low current is wired and operated by the copper foil portions 4 on the lower surface of the printed board 1. On the other hand, the electric circuit for a high current is operated as a circuit of large current capacity because the short bars 5 clinched to the copper foil portions 3 on the upper surface of the printed board 1 conduct high currents. This makes it easier to dispose the high-current electric circuit and the low-current electric circuit within a limited area on the printed board of the single kind. In this embodiment, both the upper and lower surfaces of the printed board 1 are respectively provided with the copper foil portions, but in a simple electric circuit, a high-current circuit can be constructed using the short bars on only one surface. Industrial Applicability In the circuit board device for a magnetics circuit and the method of manufacturing the same according to the present invention, electric circuits are respectively formed on the front and rear surfaces of a printed circuit board by the use of copper foils, and conductors for high currents are clinched in portions for passing the high current, thereby simplifying the manufacturing process and lowering cost.

Claims: A circuit board device for a magnetics circuit for use in wiring an electric circuit which handles a high current, characterized by: a printed circuit board (1) in which circuit patterns of copper foil portions (3, 4) are formed by an etching process on plate surfaces of an electric insulator blank (2) that is formed with openings (31) provided in the copper foil and penetrating both the surfaces; and short bars (5) fastened to the copper foil portions including said openings and which serve as conductor pieces for the high currents; wherein through-holes (51) somewhat smaller in diameter than said openings are provided in positions of said short bars corresponding to said openings, and peripheral end parts of said through-holes are bent into the openings and are burred to secure mechanical and electrical connections. A circuit board device for a magnetics circuit according to claim 1, characterized in that said short bars are provided on one surface of said printed circuit board, while the circuit pattern for low currents is formed on the other surface thereof. A circuit board device for a magnetics circuit according to claim 1, characterized in that said each short bar is spliced to the corresponding copper foil portion by soldering. A circuit board device for a magnetics circuit according to claim 1, characterized in that an electric component is fixed to the burred hole (52, 53) of said short bar (5) through threadable engagement. A circuit board device for a magnetics circuit according to claim 1, characterized in that an electric component is fixed to the copper-foil circuit pattern of said printed circuit board by said through-holes formed in both end parts of said each short bar. A method of manufacturing the circuit board device for a magnetics circuit according to claim 1, comprising the steps of: forming a solder layer on an outer surface of said each copper foil portion to which said short bar is to be fastened; placing the corresponding short bar on said solder layer, and bringing the former into pressing contact with the latter by means of a heating roller; and mechanically fixing said short bar by the burring in said openings which penetrate both surfaces of said printed circuit board.

Inventors: FUJIOKA, YOSHIKI FANUC MANSION HARIMORI 6-305
Applicants: FANUC LTD.
Application year: 1988
Main classification: H05K1
IPC codes: H05K1, H01B5, H05K3, H05K7