JPH05327196A - Printed board for mounting electronic component using narrow pitch electrodes - Google Patents

Abstract

PURPOSE:To eliminate the cause of short-circuit and to prevent a defective product on a surface by preventing formation of a bridge between adjacent connecting conductors with excess solder at the time of mounting an electronic component on a printed board for mounting the component having narrow pitch electrodes. CONSTITUTION:Part of an insulating layer 4 between connecting conductors 3 of a printed board 1 is removed, excess solder releasing recess 6 is formed in a capacity of a volume of the excess solder 5 at the time of placing a component, or part of the layer at each position corresponding to a narrow pitch electrodes of the component is removed on the board, a recess having a capacity of sum of the volumes of the electrodes to be solder-connected to the conductors to be formed thereon and the excess solder at the time of placing the component is provided, and a conductor is formed in the inner surface of the recess.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a printed circuit board for surface mounting an electronic component having a narrow pitch electrode.

[0002]

2. Description of the Related Art Electronic components such as ICs, LSIs, VLSIs and the like are solder pastes (not only Sn-Pb type pastes but also Ag pastes and other conductive materials) on a printed circuit board through conductors (pads) for electrode connection. If a large amount of solder paste is used, the excess solder will squeeze out when the components are mounted. For example, as shown in FIG. A bridge may be formed between the three.

Since this bridge causes a short circuit and makes the product defective, it is necessary to prevent the bridge from being formed by the excess solder 5. Conventionally, for example, as shown in FIG. Apply 8
In other words, the formation of dikes prevented the formation of bridges.

[0004]

However, as described above, the means for applying the solder resist ink 8 between the conductor portions 2 to prevent the bridge formation due to the excess solder 5 is to increase the number of pins and the density of the electronic parts. When the pitch of the electrodes is further narrowed and the pitch between the conductor portions 3 for connection on the substrate side is also narrowed (for example, the wiring density is 0.3 mm pitch or less), the conductor portions 3
There is a problem that the accuracy of applying the solder resist ink 8 between the gaps and the decrease in the adhesion strength of the ink 8 occur. Therefore, the above means is no longer effective in preventing the formation of bridges due to excess solder.

Therefore, there is a demand for the development of means capable of effectively preventing the formation of a bridge due to excess solder without increasing the cost with a simple means. The present invention is intended to solve the above problems in a printed circuit board for mounting an electronic component having a narrow pitch electrode, and an object thereof is to mount an electronic component having a narrow pitch electrode between connecting conductor portions. Another object of the present invention is to provide a printed circuit board that prevents the formation of bridges due to excess solder and eliminates the occurrence of short circuits on this surface.

[0006]

[Means for Solving the Problems]

A. A first printed circuit board for mounting an electronic component having a narrow pitch electrode according to the present invention is a connecting conductor portion formed on the printed circuit board 1 at a narrow pitch corresponding to the narrow pitch electrode 2 of the electronic component. In between 3, a part of the insulating layer 4 of the printed board 1 is removed with a volume equal to or larger than the volume of the excess solder 5 at the time of mounting the component, and the excess solder escape recess 6 is formed (FIG. 1 ・ See Fig. 2).

The above-mentioned recess 6 for excess solder escape may be a recess having a bottom or a hole having no bottom.

B The second printed circuit board for mounting an electronic component having a narrow pitch electrode according to the present invention has an insulating layer 4 at each position on the printed circuit board 1 corresponding to each narrow pitch electrode 2 of the electronic component. A concave portion 7 having a volume not less than the sum of the respective volumes of the electrode 2 to be solder-joined to the connecting conductor portion 3 formed therein and the surplus solder 5 at the time of mounting the component is provided.
The conductor portion 3 is formed on the inner surface.

In the figure, reference numeral 9 indicates a bonding solder.

[0010]

When the narrow pitch electrodes 2 of the electronic component are bonded to the conductor portions 3 for connection on the printed circuit board 1 with solder paste and mounted, an excessive amount of solder paste is placed on the conductor portions 3 when the components are mounted. If there is, it becomes the excess solder 5. If the amount of solder paste is too much for joining, excess solder 5
Is also increased by that amount, and as it is, a bridge connecting the adjacent conductor portions 3 is formed.

1) However, the above-mentioned first printed circuit board for mounting an electronic component having a narrow pitch electrode according to the present invention has a portion of the insulating layer 4 between the connecting conductor portions 3 of the printed circuit board 1. The excess solder 5 is removed to form the excess solder escape recess 6 with a volume equal to or larger than the volume of the excess solder 5 when the component is mounted.

Therefore, even if the surplus solder 5 is generated, the surplus solder 5 flows into the surplus solder escape recess 6 between the conductor portions 3. However, the volume of the recess 6 is the volume of the surplus solder 5 as described above. Because of the above, no bridge connecting the adjacent conductor portions 3 is formed (see FIGS. 1 and 2). The excess solder 5 in the recess 6 can be easily removed.

2) On the other hand, the second printed circuit board for mounting an electronic component having a narrow pitch electrode according to the present invention is
When a part of the insulating layer 4 at each position corresponding to each narrow pitch electrode 2 of the electronic component is removed on the printed circuit board 1 and the electrode 2 to be soldered to the connecting conductor portion 3 formed therein and the component are mounted The recesses 7 having a volume not less than the sum of the respective volumes of the excess solder 5 are provided, and the conductor portion 3 is formed on the inner surface of each recess 7.

Therefore, even if the surplus solder 5 is generated, the surplus solder 5 flows into the recess 7, but the volume of the recess 7 is the electrode 2 and the surplus solder which are soldered to the connecting conductor portion 3 as described above. Since it is equal to or more than the sum of the respective volumes of No. 5, the excess solder 5 does not overflow from there and a bridge connecting the adjacent conductors 3 is not formed (see FIG. 3).

[0015]

1 and 2 show a first printed circuit board for mounting an electronic component having narrow pitch electrodes according to the present invention, and FIG. 3 shows the second printed circuit board. Although a single-layer printed circuit board is shown in the illustrated example, the same applies to a double-sided or multi-layer printed circuit board.

As a base material of a printed circuit board for mounting electronic parts having narrow pitch electrodes according to the present invention, for example, an organic solder which can form the above-mentioned recess 6 or recess 7 for excess solder escape by irradiation of excimer laser or the like. It is better to use a molecular material. Specifically, it may be used for an aramid-based printed circuit board material, a polyimide-based FPC, TAB, or the like.

Further, the recess 6 for recessing the excess solder and the recess 7 are provided.
Is formed by removing the desired volume from the insulating layer 4 by irradiating the excimer laser or the like, for example, using a mask image, a contact mask, or a conformal mask formed of a printed circuit board surface layer conductor. do it.

In the first printed circuit board of the present invention, the excess solder escape recess 6 is a recess having a bottom as shown in FIG. 1 or a through hole having no bottom as shown in FIG. May be In the second printed circuit board of the present invention, the connecting conductor portion 3 formed in each recess 7 may be formed by, for example, copper plating the inner surface of the formed recess 7.

[0019]

As is apparent from the above, the printed circuit board for mounting an electronic component having a narrow pitch electrode according to the present invention is used for mounting an electronic component having a narrow pitch electrode between connecting conductor portions for connection by excess solder. It is possible to prevent the occurrence of the bridge.

That is, in a conventional printed circuit board for mounting an electronic component having a narrow pitch electrode, a solder resist ink is generally applied between the conductor portions to prevent the occurrence of a bridge between the connecting conductor portions due to excess solder. .. However, when the pitch of the conductors on the printed circuit board side becomes narrower in response to the narrower pitch of the electrodes of electronic parts as in recent years, there is a problem that the accuracy of solder resist ink application between the conductors and the adhesion strength of the ink decrease. Occurs and is no longer effective in preventing the formation of bridges.

On the other hand, in the present invention, as described above, by removing a part of the insulating layer between the connecting conductor portions of the printed circuit board, the excess solder escapes at a volume equal to or larger than the volume of the excess solder when the component is mounted. When mounting a component by forming a recess or removing a part of the insulating layer at each position corresponding to each narrow-pitch electrode of the electronic component on the printed circuit board and solder-bonding the electrode A recess having a volume not less than the sum of the respective volumes of the excess solder is provided and a conductor portion is formed on the inner surface of each recess.

Therefore, in the present invention, the above-mentioned first and second
In both cases, the excess solder is in the recess between the connecting conductors,
Alternatively, it flows into the recess and accumulates therein, but since the volume of the recess or the recess has a volume equal to or larger than the volume of the excess solder,
Excessive solder will not overflow from it, and the formation of bridges connecting adjacent conductor portions can be prevented. Therefore, it is possible to prevent the occurrence of a short circuit due to the bridge due to excess solder, and to eliminate the occurrence of defective products on this side.

[Brief description of drawings]

FIG. 1 is a partially enlarged vertical perspective view showing a first embodiment of a printed circuit board according to the present invention.

FIG. 2 is a partially enlarged vertical perspective view showing a modified example of the first embodiment of the printed circuit board according to the present invention.

FIG. 3 is a partially enlarged vertical perspective view showing a second embodiment of the printed circuit board according to the present invention.

FIG. 4 is a partially enlarged vertical perspective view showing a state in which a bridge is formed on a conventional printed circuit board.

FIG. 5 is a partially enlarged vertical perspective view showing a bridge formation preventing means in a conventional printed circuit board.

[Explanation of symbols]

1-Printed circuit board 2-Narrow pitch electrode 3
-Connecting conductor part 4-Insulating layer 5-Excessive solder 6
-Recess 7-Recess 9-Joint solder

Claims (2)

[Claims] 1. A part of an insulating layer 4 of a printed circuit board 1 is mounted between parts of connecting conductors 3 formed at a narrow pitch on a printed circuit board 1 in correspondence with a narrow pitch electrode 2 of an electronic device. A printed circuit board for mounting an electronic component having a narrow pitch electrode, which is formed by removing the excess solder 5 with a volume equal to or larger than that of the excess solder 5 and forming the excess solder escape recesses 6. 2. A printed circuit board (1) is provided with a portion of an insulating layer (4) at each position corresponding to each narrow pitch electrode (2) of an electronic component and an electrode (2) soldered to a connecting conductor portion (3) formed there. A recess 7 having a volume equal to or larger than the sum of the respective volumes of the excess solder 5 when the component is mounted is provided, and the conductor portion 3 is formed on the inner surface of each recess 7.
Printed circuit board for mounting electronic components with narrow pitch electrodes.