JP2871840B2 - Printed wiring board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a printed wiring board on which electronic components such as an IC chip are mounted.

[Conventional technology]

2. Description of the Related Art Conventionally, for example, an IC chip is mounted on a printed wiring board, and a bonding pad row is arranged on an outer peripheral portion thereof. The two are electrically connected by wire bonding. The bonding pad is formed by repeatedly performing a surface treatment such as buffing in a drilling, plating, resist, etching, formation of a solder resist and the like, and a processing step.

[Problems to be solved by the invention]

However, in the pretreatment by the buff polishing, in particular, in the surface treatment after the pattern formation, as shown in FIG. 6, the polishing brush 13 is provided on the IC chip side of the individual bonding pads 12 in the bonding pad row on the printed board 11. Since the end portion is hit, the corner portion of the end portion is excessively polished.
Accordingly, as shown in FIG. 7, the flat portion 14 on the upper surface of the bonding pad 12 has an arc shape, and its area is reduced.
As a result, there has been a problem that an area where good bonding can be performed is reduced, or a defect such as wire stitch separation is likely to occur when bonding is performed on a polished portion.

Therefore, an object of the present invention is to provide a printed wiring board that can prevent excessive polishing of the ends of the bonding pads in the pretreatment of gold plating, and can reliably perform bonding.

[Means for solving the problem]

In order to solve the above problems, in the present invention, in a printed wiring board in which bonding pads are arranged on an outer peripheral portion of an electronic component mounting portion for mounting electronic components, at least inside the bonding pads, a height higher than the bonding pads. The gist is a printed wiring board provided with a high solder resist portion.

[Action]

With the above configuration, when the bonding pad is polished with a polishing brush in the pretreatment of gold plating, the end of the bonding pad is protected by the solder resist, and the polishing brush is difficult to hit. It will not be done.

〔Example〕

(First Embodiment) FIGS. 1 and 2 show an embodiment of the present invention.
Description will be made based on the drawings.

As shown in FIG. 1, a large number of bonding pads 2 are arranged on an outer peripheral portion of an IC chip mounting portion 1 on a printed circuit board. The bonding pads 2 have a small rectangular shape and are arranged in a large number at regular intervals in the width direction thereof. The bonding pads 2 are formed in a square ring shape so as to surround the IC chip mounting portion 1 as a whole. I have. Except for the bonding pad row 3 for connection and the like, a solder resist portion made of an epoxy resin or the like is formed on the printed board for the purpose of protecting the wiring pattern and reducing gold plating. Further, there is no wiring pattern inside the bonding pad row 3, and a solder resist portion (hereinafter referred to as a solder resist) 4 which is originally unnecessary has a predetermined distance from an IC chip (not shown) mounted on the IC chip mounting portion 1. In addition, it is formed so as to form a square ring with a substantially constant width.

As shown in FIG. 2, the height of the solder resist 4 on the printed circuit board 6 is formed higher than the height of the bonding pad 2, and the side surface of the solder resist 4 is inclined so that the lower portion is slightly wider. Is formed. The height of the solder resist 4 is formed higher than the height of the bonding pad 2 in order to prevent excessive polishing of the end of the bonding pad 2 by buff polishing described later.

The wire bonding is performed between the terminals on the IC chip mounted on the IC chip mounting portion 1 and the respective bonding pads 2. In order to increase the wire bonding speed and to prevent a short circuit between the bonding wires. Therefore, it is desirable that the wire loop be short and the bonding interval be short.

Therefore, it is desirable to use the tip of each bonding pad 2 as much as possible. In this embodiment, a solder resist 4 higher than each bonding pad 2 is provided inside the bonding pad row 3 by an IC.
Since it is formed so as to form a rectangular ring with a substantially constant width so as to have a predetermined interval with the chip, a flat surface is secured without particularly being subjected to excessive polishing due to buff polishing at the tip of each bonding pad 2. Therefore, wire bonding can be performed at the shortest interval.

The solder resist 4 formed inside the bonding pad row 3 can be formed together with a solder resist for the purpose of protecting a wiring pattern and reducing gold plating, and in that case, the number of special steps is not increased. In addition, it is of course possible to perform it as a separate process without printing all at once.
When it is performed as a separate step, the height can be increased by increasing the number of times of printing according to the wiring pattern thickness and the polishing strength.

Second Embodiment Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. In this embodiment,
A description will be given mainly of parts different from the first embodiment.

As shown in FIG. 3, inside the bonding pad row 3 and outside at a fixed distance from the IC chip mounting portion 1,
The solder resist 4 differs from the first embodiment in that a square ring is formed by a screen printing method and the inside of the four corners is rounded. The height of the solder resist 4 is higher than the height of the bonding pad 2.

A method for forming the solder resist 4 will be described. As shown in FIG.
The solder resist 4 is applied entirely by a method such as a screen printing method with a certain distance inward. Next, the outer peripheral portion of the solder resist 4 is left in a rectangular ring shape with a substantially constant width, and the inner portion of the solder resist 4 is pierced to a constant depth by a router process (rounding). In this manner, a square-shaped solder resist 4 having a substantially constant width is obtained at a position inside the bonding pad row 3 and outside the IC chip mounting portion 1.

According to this method, since the solder resist 4 may be formed in a rectangular shape, the solder resist 4 can be formed in a simple shape.
Height can be adjusted low. In addition, since the surface obtained by spot facing is flatter, there is an effect that IC chip mounting and wire bonding can be performed more stably.

Third Embodiment Next, still another embodiment will be described with reference to FIG. In the present embodiment, parts that are different from the first embodiment will be mainly described.

As shown in FIG. 4, a solder resist 4 is applied to the entire inside of the bonding pad row 3 including the IC chip mounting portion 1 by a screen printing method or the like.

According to this method, the solder resist 4 can be formed in a simple shape, and it is not necessary to perform counterboring by router processing or the like. However, solder resist 4 is IC
Since the IC chip is also formed on the chip mounting portion 1, when the IC chip is mounted on the IC chip mounting portion 1, the height of the IC chip is increased accordingly.

Fourth Embodiment Next, still another embodiment will be described with reference to FIG.
Also in the present embodiment, parts different from the first embodiment will be mainly described.

As shown in FIG. 5, the bonding pads 2 are not provided at the four corners of the outer peripheral portion of the IC chip mounting portion 1. Therefore, the solder resist 4 is also provided inside the bonding pad 2 at a position corresponding to the bonding pad 2. On the side, a solder resist 4 is formed in a discontinuous state on the outer peripheral portion of the IC chip mounting portion 1.

Even with this configuration, there is no possibility that the tip of the bonding pad 2 is excessively polished by the polishing brush 5. The position, width, and the like of the portion where the bonding pad row 3 is not provided are appropriately set according to the purpose.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION The printed wiring board of this invention has the effect that the edge part of the bonding pad can be effectively prevented from being excessively polished in the pretreatment of plating such as gold plating, and as a result, bonding can be performed reliably.

[Brief description of the drawings]

1 and 2 are views showing a first embodiment of the present invention. FIG. 1 is a plan view showing a state in which a solder resist is provided inside a bonding pad of a printed wiring board, and FIG. FIG. 3 is a cross-sectional view of a main part showing a state in which buffing is performed on the end of the bonding pad with a polishing brush; FIG. 3 is a plan view of a main part showing a second embodiment; FIG. 5 is a plan view of a main part showing a third embodiment, FIG. 5 is a plan view of a main part showing a fourth embodiment, FIGS.
FIG. 7 is a cross-sectional view of a principal part showing a state in which buffing is performed on the end of the bonding pad with a polishing brush, and FIG. 7 is a plan view showing the bonding pad after polishing. 1 ... IC chip mounting section as electronic component mounting section, 2 ...
Bonding pad

Claims (1)

(57) [Claims] An electronic component mounting section for mounting an electronic component.
A printed wiring board having a bonding pad (2) arranged on the outer periphery thereof, at least inside the bonding pad (2);
A printed wiring board provided with a solder resist portion (4) higher than the bonding pad (2).