JPH07254775A - Circuit board - Google Patents

Abstract

PURPOSE:To obtain a circuit board capable of checking the running solder and mounting a compact element for integrated circuit without solder resist prossing at all forming trenches for checking the running solder on a circuit pattern. CONSTITUTION:In order to make a conductive circuit pattern, trenches are formed near the neck of a compact element simultaneously or additionally. Next, a metallic pattern 1 is formed in junction with an insulating supporting substrate such as resin etc., so as to mount a compact element 6 as if striding over the lands 8, 8. At this time, the trenches 3 are formed in the mettallic pattern 1 near the solder land. By these trenches 3, the running solder can be checked in the solder reflow time, pasty solder filling step and compact element mounting step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive circuit pattern, and more specifically to a structure for blocking the flow of solder in the conductive circuit pattern.

[0002]

2. Description of the Related Art There are various types of circuit boards that form electronic circuits for controlling electronic equipment and methods of forming the same. In order to avoid the environmental atmosphere and the magnetic influence of the circuit, the strength used while maintaining the shape should be improved for those used in circuits integrated with magnetic members and those used in electronic devices that require shape retention. In order to keep it, a metal plate such as an iron plate or aluminum is coated with an insulative resin to form an insulative metal base supporting substrate, and a copper foil is adhered onto it, or a metal foil such as a copper clad laminated sheet There is a circuit board in which a pattern is formed on a copper foil surface after being attached to a metal plate and then etched to form a circuit board. A circuit board in which a solder resist is formed on the pattern after the formation of the circuit board to stop the flow of the solder in the pattern before mounting the small element for the integrated circuit is widely known.

As a method other than the pattern formation by etching, a metal plate such as an iron plate or a copper plate or a metal foil stamped and molded into a circuit pattern shape is embedded in an insulating layer, coated with an insulating resin, or an insulating plate. There is also a circuit board in which a circuit integrated with an insulating support base is formed by a method of sandwiching the circuit board. In this case, if electronic components are not mounted, or if they are electronic components with lead legs even if they are mounted, a solder resist for stopping the flow of pattern solder is not particularly required, but a small element for integrated circuits is mounted. In order to do so, the same solder resist as the above circuit board was required.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a groove for preventing the flow of solder is formed in a conductive circuit pattern of a circuit board so that the flow of solder is blocked and a small size for an integrated circuit can be obtained without performing a solder resist process. An object of the present invention is to provide a method for forming a conductive circuit pattern on which an element can be mounted, simplifying the manufacturing process, and at the same time making the circuit board inexpensive.

[0005]

SUMMARY OF THE INVENTION Therefore, according to the present invention, in a circuit board in which an electric circuit component is soldered to a conductive circuit pattern, a solder flow prevention is provided in the vicinity of the conductive circuit pattern where the electric circuit component is soldered. A groove for forming was formed.

[0006]

When the circuit forming the conductive circuit pattern is formed, the groove is formed in the vicinity of the neck of the soldering land portion for mounting the small element simultaneously or by additional machining. The groove can prevent the solder flow when the paste solder is piled up, the small element is mounted, and the solder reflow is performed. As a result, it becomes unnecessary to form a resist for preventing solder flow.

[0007]

FIG. 1 is a side sectional view showing a groove formed on a circuit pattern of a punched circuit board according to the present invention and a case where a small element for an integrated circuit is mounted on the circuit pattern. Figure 1
In, the metal pattern 1 is formed by being joined to the insulating support base 4 made of resin or the like, and the small element 6 is mounted so as to straddle the lands 8, 8. There are grooves 3 in the metal pattern 1 near the lands 8 to which the solder (7) is attached. In FIG. 1, the angle formed by the side surface of the groove 3 and the bottom surface of the groove 3 is shown as a right angle, but the portion indicated by R may be tapered.

FIG. 2 shows an example in which the groove of the present invention is formed except the insulating end portion of the insulating support base, and is a view of the circuit pattern seen from above. In FIG. 2, a supporting substrate 4 such as resin
A metal pattern 1 is formed adjacent to
There is a groove 5 on the metal pattern 1 in the vicinity of 8. The groove 5 traverses the metal pattern 1 but does not extend to the metal pattern 9 adjacent to the support substrate 4. Therefore, the groove has a substantially rectangular shape. The groove 5 may completely traverse the metal pattern 1.

FIG. 3 is an explanatory diagram of an experimental example for explaining the fact that the groove prevents the solder flow. First, a convex upper punch was dropped on a strip-shaped tin-plated copper plate having a thickness of 0.1 mm and a width of 2.5 mm to form a groove. The width of the groove is 0.35 mm and the depth of the groove is 0.04 mm. Then, a certain amount of solder paste was placed on the solder land portion separated by the groove and reflow was performed. In this case and after reflowing, a fixed amount of solder paste was placed on the solder land portion (not divided by grooves) of a strip-shaped tin-plated copper plate having a thickness of 0.1 mm and a width of 2.5 mm, and after reflow. The difference in the solder outflow length is as shown in the graph of FIG.

FIG. 4 shows the measured outflow length X when a solder flow occurs over the groove.
Area Smm of the part separated by the groove and the same part without the groove
^The result of dropping to ² and melting by reflow is G / S (g / S
mm ² ) is plotted on the horizontal axis and the solder outflow length X is plotted on the vertical axis.
As shown in the figure, when a groove is provided, there is no solder flow up to 2.8 g / Smm ² , and the effect of preventing the solder flow after reflow by the groove is obvious. See Thus, for example, the amount of applied solder of solder land portion on the conductive circuit pattern created by the process shown in FIG. 5 and are effective solder flow prevention in 1.1~1.2g / Smm ² because the grooved land part To be disregarded.

FIG. 5 is a flow chart showing an example of a method for forming a circuit board according to the present invention corresponding to a method for manufacturing a circuit board using a metal plate punched out in a circuit shape. In the first step, a punching circuit is formed by pressing a copper or tin-plated, gold-plated, silver-plated steel plate or the like according to the pattern. However, if the circuit is pressed so that only the circuit is left, the circuit is dispersed, so that a part necessary for holding the circuit is left. Alternatively, a copper plate may be attached to a base sheet having releasability to form a transfer sheet and chemically etched to obtain a metal circuit. That is, after attaching the copper plate to the adhesive sheet, the copper plate is subjected to etching corresponding to the pattern to leave only the circuit pattern. Similar to the punching, the pattern holding member for preventing circuit dispersion is left. After that, the adhesive sheet is removed.

In the second step, a groove is formed by a convex upper punch in the soldering portion of the punching circuit.

In the third step, the distortion when the circuit is punched out is corrected by sandwiching it with a metal plate having a smooth surface.

The resin frame forming the insulative support base has through holes necessary for performing the unnecessary part cutting press which is a post-process, and the material is any synthetic resin which can be hot pressed. May be. For example, epoxy resin, phenol resin, acrylic nitrite resin, etc. can be used. The resin frame is hot pressed so that the upper surface of the punching circuit is exposed, and the punching circuit and the resin frame are integrally molded.

In the fourth step, unnecessary portions of the punching circuit are cut and pressed using the through holes in the resin frame. Next, in the fifth step, solder paste is printed, and after mounting small components, soldering is performed by solder reflow.

Although the manufacturing process has been described with respect to the circuit board using the punched conductive circuit pattern, the present invention is not limited to the punched conductive circuit pattern but can be applied to a circuit board having a conductive circuit pattern formed by etching.

[0017]

The groove in the metal plate or metal foil stops the solder flow in the solder reflow furnace.
As a result, a resist for preventing solder flow is not required, which is highly economical and reduces the manufacturing cost. The groove can be relatively easily formed by dropping the upper punch on the metal plate or the foil, and further, the post-treatment such as deburring and polishing is not necessary, and the reliability of the circuit is improved. It is possible to omit complicated steps such as resist printing, resist stripping, and water washing.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a case where a small element for an integrated circuit is mounted on a groove formed on a circuit pattern of a punched circuit board of the present invention and a pattern of the circuit board.

FIG. 2 is an enlarged view showing a groove of the present invention formed by removing an insulating end portion of an insulating support base.

FIG. 3 is an explanatory diagram of an experimental example in which the fact that solder flow is prevented by the groove is compared with the case where the groove is not formed.

FIG. 4 is a comparative diagram comparing the outflow results in the experiment according to FIG.

FIG. 5 is a flow chart showing an example of a method for forming a circuit board according to the present invention, which corresponds to a method for manufacturing a circuit board using a metal plate punched out in a circuit shape.

[Explanation of symbols]

 1 Metal Pattern 3 Groove 4 Support Base 5 Groove 6 Small Element 7 Solder 8 Land 9 Metal Pattern

Claims (1)

[Claims] 1. A circuit board formed by soldering an electric circuit component to a conductive circuit pattern, wherein a groove for preventing solder flow is formed in the conductive circuit pattern in the vicinity of the electric circuit component being soldered. Characteristic circuit board.