JPH08274444A - Structure of wiring board - Google Patents

Abstract

PURPOSE: To prevent the Manhattan effect by providing a bump, which has a height over the thickness of pads for mounting a chip part thereon, between the pads. CONSTITUTION: Between a pad 2 and a pad 3 on a board a bump 9 having a slightly higher than the thickness of the pads is provided. Cream solders 5 and 6 are printed on the pads 2 and 3, a square chip 4 is mounted over the bump 9 and the solders are reflowed by heating and are solidified. Solder swelling made during the reflow and solidification is limited by generating a small space between the pad 3 and an electrode 8 of the chip. Through the step the Manhattan effect is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a wiring board, and more particularly to a shape which is convenient for mounting chip parts.

[0002]

2. Description of the Related Art In recent years, surface mounting has become mainstream for mounting electronic components on a wiring board in order to achieve high density. For example, resistors and capacitors are becoming smaller, and rectangular or cylindrical chip type parts with electrodes on both ends, and small ones with a width of 0.5 mm, a length of 1 mm, and a height of 0.4 mm are used. There is. When these are electrically connected to the wiring board, the electrode pads 2, 3 on the wiring board 1 are connected as shown in FIG.
After applying the cream solder 5 on the electrodes 7 of the chip component 4,
8 is placed so as to straddle, and then the conductive connecting materials 5 and 6 are melt-cured and connected as shown in FIG.

However, in the process of melting or hardening the conductive connecting materials 5 and 6, one of the electrodes 7 is fixed from the pad 2 on the substrate 1 in an upright state, as shown in FIG. 9, which is generally called Manhattan phenomenon. May cause defects. There are many possible causes for this, but the conductive connecting material 5,
6 causes a difference in the melting or curing rate, the surface tension imbalance causes the chip component 4 to be attracted to the conductive material side of one of the pads 2 and 3, and the electrode on the opposite side is separated from the pad on the substrate side. It is thought that this is because it hardens as it is.

Therefore, various methods have been devised in order to prevent the Manhattan phenomenon, but as the chip component becomes smaller, the conventional method has not always been effective.

[0005]

An object of the present invention is to eliminate the drawbacks of the conventional wiring board for mounting chip parts as described above, and to prevent the Manhattan phenomenon in the process of connecting the chip parts to the pads on the substrate. An object of the present invention is to provide a structure of a wiring board that can prevent the occurrence.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the structure of a wiring board according to the present invention is such that a conductive pattern is formed on the surface of the wiring board.
It is characterized in that a protrusion having a height exceeding the thickness of the pad is provided between the pads on which electronic parts are to be mounted.

Secondly, the protrusions are flat plates extending between the pads.

Further, the protrusion has a frame-like shape extending between the pads, or the protrusion has a plurality of parallel lines extending between the pads, and further, the protrusion is It is characterized in that it has a frame-like shape that extends between the pads at right angles to the axial direction of the chip component and extends in a plurality of parallel lines.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a sectional view showing a case where a chip component is mounted on an embodiment of a wiring board according to the present invention.

That is, the pad 2, which is slightly higher than the pad 2, is provided between the pads 2, 3 on the substrate 1.
The cream-shaped solders 5 and 6 are printed on 3 and the square chip 4 is mounted so as to straddle the protrusions 9, and the solders 5 and 6 are melted and cured by heating by reflow.

FIG. 2 is a plan view showing the shape of the pads of the wiring board before mounting the chip parts, and is a view showing a state in which the projection 9 is provided between the pads 2 and 3 on the substrate by, for example, screen printing.

FIG. 3 is an enlarged and detailed illustration of a part of the structure of the wiring board according to the present invention shown in FIG. 1, in which a slight gap is formed between the pad 3 and the electrode 8 of the chip 4. Therefore, the rising amount of solder is limited.

As a result of repeated experiments with this structure, it has been confirmed that the Manhattan phenomenon is extremely reduced.

Further, the projections are not necessarily formed by printing, and a thin film sheet may be adhered, or the projections may be formed by a resist or prepreg that brings about the same effect when forming a wiring board.

Further, the protrusion is not necessarily rectangular, and may be generated only by a rectangular frame as shown in FIG. 4, or as a plurality of linear shapes as shown in FIG. 5, or as shown in FIG. As shown, it may be generated in a plurality of linear shapes formed perpendicular to the axial direction of the chip component direction.

Although the present invention has been described as an example in which the present invention is applied to a rectangular chip, the present invention is not limited to this, and may be a cylindrical shape or a lead component.

[0018]

Since the present invention is constructed as described above, it exerts a remarkable effect in preventing the Manhattan phenomenon.

Further, since the solder is interposed between the component electrode and the pad, the warp of the substrate causes stress on the connection portion, but the conductive connection material buffers it so that breakage or peeling hardly occurs.

[0020]

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view showing an embodiment of the present invention.

FIG. 3 is a sectional view showing an embodiment of the present invention in detail.

FIG. 4 is a plan view showing a state in which a protrusion according to the present invention is formed in a frame shape.

FIG. 5 is a plan view showing a state in which a protrusion according to the present invention is formed in a parallel line shape.

FIG. 6 is a plan view showing a state in which a protrusion according to the present invention is formed in a vertical linear shape.

FIG. 7 is a configuration diagram showing a conventional method of mounting a square chip (before reflow).

FIG. 8 is a configuration diagram showing a conventional method of mounting a square chip (after reflow).

FIG. 9 is a cross-sectional view showing a Manhattan phenomenon generated by a conventional method of mounting a rectangular chip.

[Explanation of symbols]

 1 ... Substrate 2,3 ... Pad 4 ... Square chip 5,6 ... Conductive connection material 7,8 ... Electrode 9 ... Protrusion

Claims (5)

[Claims] 1. A wiring board having a conductive pattern formed on a surface thereof for mounting electronic parts, wherein a projection having a height exceeding the thickness of the pads is provided between pads on which chip parts are to be mounted. Board structure. 2. The structure of the wiring board according to claim 1, wherein the protrusion has a flat plate shape extending between the pads. 3. The structure of the wiring board according to claim 1, wherein the protrusion has a frame shape extending between the pads. 4. The structure of a wiring board according to claim 1, wherein the protrusion is a plurality of parallel lines extending between the pads. 5. The projection according to claim 1, wherein the projection has a frame shape extending between the pads at a right angle to the axial direction of the chip component and extending in parallel lines. The structure of the wiring board.