JPH05226792A - Printed circuit board - Google Patents

Abstract

PURPOSE:To suppress the degree of warpage of a printed circuit board after a reflow to a reduced level by forming a row of slits, in which a plurality of fine slits arranged substantially orthogonal to a lengthwise direction of the board are drilled, at areas of the board to be disregarded which extend in the lengthwise direction of the board. CONSTITUTION:Perforations 2 are defined on the surface of a printed circuit board 1. A circuit board section 3 acting as an area where electronic components are mounted and areas 4 of the circuit board to be disregarded are adjacently formed with the perforations 2 between them. Fine slits 5 are formed at substantially right angles to a direction in which the circuit board 1 is transferred between various types of assembly units containing a reflow process during a process for mounting components on the board 1. A plurality of slits are also formed along a transfer direction 6. Warpage of the board 1 exists between the slits 5, but it appears outside as a considerably small amount of warp. The total amount of warpage arising over the entirety length of the board is suppressed to a value which satisfies the standard for printed circuit boards.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board on which electronic parts are surface-mounted using a so-called reflow device.

[0002]

2. Description of the Related Art In recent consumer devices, which are increasingly required to be small and portable, the surface area of the printed circuit board to be used is increased by frequently using electronic parts called surface mount type for the printed circuit board. Attempts have been made recently to reduce it.

In the mounting of components on such a printed circuit board, a method called soldering for soldering electronic components to the printed circuit board has become the mainstream. In particular, heat during reflow is applied to an electronic component mounting apparatus. The printed circuit board may be warped exceeding the allowable standard value. A conventional printed circuit board will be described below with reference to FIGS.

As shown in FIG. 4, the conventional printed circuit board 9 is divided into a circuit board portion 11 in a region where electronic components are mounted by a perforation 10 and a waste substrate 12 portion. The printed circuit board 9 in the component mounting step is set at a predetermined position when the electronic component is mounted by the electronic component mounting apparatus. At the time of setting, the warp of the printed circuit board 9 should be made as small as possible. The side edges in the longitudinal direction of the printed circuit board are clamped to the component mounting device.
Therefore, the longitudinal direction of the printed circuit board 9 during the component mounting process is the carrying direction 13.

When the printed circuit board 9 is passed through the reflow device in the transport direction 13 which is the longitudinal direction of the printed circuit board 9, the printed circuit board 9 which is not appropriately processed for warping is shown in FIG.
As shown in (1), due to heat during reflow, habits of the printed circuit board itself, etc., the printed circuit board 9 having no warp,
The printed circuit board 14 has a warp amount H ₁ .

[0006]

The amount of warp H ₁ generated in the printed circuit board as described above is determined by various kinds of electronic component mounting apparatuses used in the electronic component mounting process. Beyond that, it becomes impossible to mount electronic components on the printed circuit board by the electronic component mounting apparatus.

An object of the present invention is to provide a printed circuit board which solves the above problems with a simple structure.

[0008]

SUMMARY OF THE INVENTION The present invention provides a printed circuit board for surface mounting electronic components by reflow,
The printed circuit board is characterized in that a row of slits having a large number of fine slits substantially orthogonal to the longitudinal direction is formed in a discarded substrate portion provided in the longitudinal direction.

[0009]

According to the present invention, even if a continuous warp is generated in the moving direction of the printed circuit board due to the influence of heat in the reflow device, the fine slits arranged in the waste board portion cause The above-mentioned warping force to be continued is cut off, and thus the total amount of warpage is suppressed to an extremely low level, so that the warpage standard of the printed circuit board is satisfied.

[0010]

1 is a perspective view showing an embodiment of the present invention.
Is a printed circuit board having perforations 2 on its surface, and a circuit board portion 3 in a mounting area of electronic components and a waste board portion 4 are formed with the perforations 2 as a boundary. Reference numeral 5 is a minute slit, which is formed substantially perpendicular to a carrying direction 6 for carrying the printed circuit board 1 between various mounting devices including a reflow step and the like during a component mounting step on the printed circuit board 1. Thus, a large number of slits are arranged in the transport direction 6.

The printed circuit board 1 of the present invention formed as described above can reduce warpage as described below.

When various surface mount type electronic components are automatically mounted on the circuit board portion 3, the printed circuit board is clamped at a predetermined position of the electronic component mounter, and the clamping force prints as much as possible. To prevent the circuit board from bending, the printed circuit board is clamped at its longitudinal edges. On the other hand, the electronic component mounter structurally conveys the printed circuit board in its longitudinal direction. In other words, the longitudinal direction of the printed circuit board is the carrying direction 6.

FIG. 2 is a view for explaining the reduction of the warp of the printed circuit board 1 of the present invention, in which the printed circuit board 1 which does not reflow receives heat through the reflow device and is warped. It is the side view which compared. H
₀ is the amount of warpage generated by the device during reflow, and this amount of warpage is the amount that satisfies the warpage standard for the printed circuit board of various electronic component mounting apparatuses used for mounting electronic components.

FIG. 3 shows the influence of the slit 5 on the warp of the printed circuit board 7 on the printed circuit board 7 of FIG. 2 when the slit 5 is not provided.
FIG. 6 is a schematic view showing the state of the virtual warp of FIG.

To explain the above-mentioned structure, the printed circuit board having electronic components mounted on the circuit board portion 3 is passed through a reflow device, whereby the printed circuit board becomes a printed circuit board 7 having a warp amount of H ₀ . This is discarded and the printed circuit board 8 when the slit 5 is not provided on the board portion 4
Comparing the state of the virtual warp and the printed circuit board 7 in detail, the continuous warp of the printed circuit board 8 is interrupted by the slit 5 on the discarding board portion 4, and the continuity thereof is cut off. It can be seen that the warp of the printed circuit board 7 exists between the slits 5, but appears to the outside as an extremely small amount of warp. In other words, the printed circuit board of the present invention has an effect that the total amount of warpage over the entire longitudinal direction can be suppressed to a value that sufficiently clears the standard for the printed circuit board included in various electronic component mounting apparatuses in the electronic component mounting process. There is.

[0016]

As described above, the printed circuit board of the present invention is a fine printed circuit board, which is disposed on a waste circuit board of the printed circuit board in a fine direction substantially orthogonal to the longitudinal direction which is the carrying direction of the printed circuit board in the electronic component mounting process. By providing a large number of such slits, the amount of warpage of the printed circuit board after reflow can be suppressed to an extremely low level.

[Brief description of drawings]

FIG. 1 is a perspective view showing a printed circuit board according to an embodiment of the present invention.

FIG. 2 is a diagram showing warpage that occurs in the printed circuit board of FIG.

FIG. 3 is a diagram showing an influence of a slit of the printed circuit board of the present invention.

FIG. 4 is a perspective view showing a conventional printed circuit board.

5 is a diagram showing a warp in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printed circuit board, 2 ... Perforation, 3 ... Circuit board part, 4 ... Waste board part, 5 ... Slit, 6 ...
Transport direction.

Claims (1)

[Claims] 1. A printed circuit board on which electronic components are surface-mounted by reflow, and a slit row in which a large number of fine slits substantially orthogonal to the longitudinal direction are formed in a discarded board portion provided in the longitudinal direction of the printed circuit board. A printed circuit board characterized by being formed.