JPH08330715A - Method of soldering printed-substrate and chip - Google Patents

Abstract

PURPOSE: To provide a method of soldering printed-substrate and chip capable of soldering the lead of the chip having a float bending upward onto the land of the printed-substrate without fail. CONSTITUTION: A solder resist film 4 is formed on the surface of a substrate with the land 3 of a circuit pattern formed thereon. Next, an aperture part 5 is formed in the solder resist film 4 on the land 3. This aperture part is provided with narrow width parts 5a and wide width part 5b. When the land 3 exposed in the aperture part 5 is coated with cream solder to be heated for melting down, the solder is absorbed in the wide width part 5b by surface tension to form a swelled part. Accordingly, the floating lead landing on the swelled part can be soldered without fail.

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 and a chip soldering method incorporated in an electronic device.

[0002]

2. Description of the Related Art A circuit pattern is formed on the surface of a printed circuit board, and leads of a chip are soldered to lands of the circuit pattern. By the way, the lead of the chip is apt to be lifted (bent upward) due to an error in formation or a deformation during storage and transportation. If floating occurs, the lead cannot be grounded to the solder portion on the land, resulting in poor soldering.

Therefore, the applicant of the present invention has previously proposed a printed circuit board capable of eliminating soldering failure due to floating of leads (Japanese Patent Laid-Open No. 6-77632). In this product, the planar shape of the land of the printed circuit board is a shape having a narrow portion and a wide portion. As a result, the solder portion heated and melted is attracted to the wide portion and a bulge portion is generated, and therefore the lead Even if there is some floating, the lead is grounded and soldered to this raised portion.

[0004]

In recent years, the pitch of the leads of the chip has become narrower and narrower, and the size of the land has become smaller accordingly. Although the land is formed by etching or the like, when the size of the land is reduced in this way, it is difficult to form a land having a complicated shape having a narrow portion and a wide portion in terms of processing technology.

Therefore, an object of the present invention is to provide a printed circuit board and a method for soldering a chip, which can cope with a reduction in the pitch of the leads of the chip and can reliably solder a lead having a float.

[0006]

To this end, the present invention is formed by forming a land and a solder resist film covering the land on the surface of a base material, and an opening for partially exposing the land to the solder resist film. A portion is formed, and the opening has a shape having a narrow portion and a wide portion. Further, a solder portion is formed on the upper surface of the land exposed in the opening.

Further, there is provided a chip soldering method for soldering a chip to a printed circuit board coated with a solder resist film having an opening having a narrow portion and a wide portion for partially exposing the land, wherein the opening is provided. The solder is formed on the surface of the land exposed to the part, the leads of the chip are positioned on the solder part, the chip is mounted on the printed circuit board, and the solder part is heated and melted to melt. The solder was sucked up to the wide portion and raised, and then the molten solder portion was solidified to solder the lead to the land.

[0008]

In the above structure, when the solder portion on the land is heated and melted, the melted solder is attracted to the wide portion of the opening and locally rises. Therefore, even if there is some floating in the lead, the lead can be grounded to the raised portion and reliably soldered.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a plan view of a printed circuit board according to a first embodiment of the present invention, FIG. 2 is a partial perspective view of the printed circuit board, FIG. 3 is an explanatory view of a manufacturing process of the printed circuit board, and FIG. 4 is a mounting process of the chip. FIG.

1 and 2, the printed circuit board 1
A land 3 having a circuit pattern is formed on the surface of the substrate 2. As the base material 2, glass epoxy resin, ceramics, etc. are often used. A solder resist film 4 is thinly coated on the surface of the base material 2 so as to cover the lands 3. An opening 5 is formed in the solder resist film 4 on the land 3, and the land 3 is partially exposed from the opening 5. The opening 5 has a rectangular narrow portion 5a and a circular wide portion 5b. As will be described later, the opening 5
When the solder on the land 3 is melted by forming the narrow portion 5a and the wide portion 5b on the land, the melted solder is
It is attracted to b and rises.

Next, a method of manufacturing the printed circuit board 1 will be described with reference to FIG. First, as shown in FIG. 3A, a copper foil 3 ′ is formed on the surface of the base material 2. Next, the surface is coated with an etching resist film 6 (FIG. 3B),
Next, exposure and development are performed to remove unnecessary portions of the etching resist film 6 (FIG. 3C).

Next, copper foil etching is performed to remove unnecessary portions of the copper foil 3 '(FIG. 3 (d)), and the etching resist film 6 is peeled off (FIG. 3 (e)). Next, the entire surface of the base material 2 is coated with a solder resist film 4 '(see FIG.
(F)), if the unnecessary portion is removed by performing exposure and development, the printed circuit board 1 shown in FIG. 1 is completed (FIG. 3 (g)).

Thereafter, the opening 5 is formed by a screen printing machine.
The cream solder 7'is applied onto the land 3 exposed to the outside (FIG. 3 (h)). Then, the printed circuit board 1 is heated in a heating furnace to melt the cream solder 7'and then solidify the soldered portion 7 (FIG. 3 (i)). In this case, the melted cream solder 7'is attracted to the wide portion 5b by the surface tension and the raised portion 7a is generated.

According to the above method, the above-mentioned Japanese Unexamined Patent Publication No. 6-776.
It is possible to obtain substantially the same effect as the conventional method described in Japanese Patent No. 32,32, that is, the method of forming the narrow portion and the wide portion on the land itself. Then, the land 3 is formed in a relatively large size as compared with the conventional method of forming a narrow portion or a wide portion on the land itself by, for example, chemical etching, and the solder resist film 4 ′ on the upper surface is narrowed by an optical means. The above method of forming the opening 5 having the portion 5a and the wide portion 5b allows the printed circuit board to be manufactured more accurately.

Next, a method of soldering the chip will be described with reference to FIG. In FIG. 4A, 8 is a chip, which has a large number of leads 9. In the drawing, the shape of the lead 9 on the right side is normal, but the lead 9 on the left side is bent upward and floats.

Now, the cream solder 7'is applied on the land 3 of the printed board 1 manufactured by the steps of FIGS. 3A to 3G by the step of FIG. 3H. Figure 4 (a)
The state where the lead 9 is positioned on the cream solder 7 ′ and the chip 8 is mounted on the printed circuit board 1 is shown. The chip 8 is automatically mounted on the printed board 1 by a mounter. In this case, the lead 9 on the left side has a floating
It cannot be grounded to the cream solder 7'and it is floating (Fig. 3).
(See also lead 9 in (h)).

Next, the printed board 1 is sent to a heating furnace and heated. Then, the cream solder 7 ′ is melted, but the melted cream solder 7 ′ is attracted to the wide portion 5 b as shown in FIG. Therefore, even if the lead 9 floats, the lead 9 is grounded to the raised portion 7a (see the lead 9 in FIG. 3 (i)), and the raised portion 7a that is melted and grounded to the lower surface of the lead 9 is It is attracted to the lower surface of the lead 9 and soldered as shown in FIG.

FIG. 5 is a partial plan view of a printed circuit board according to the second embodiment of the present invention. In this example, the adjacent wide portions 5b are formed in a zigzag shape, and by doing so, it is possible to more effectively prevent the adjacent wide portions 5b from being separated from each other and to form a solder bridge between them. it can.

The present invention is not limited to the above-described embodiment. For example, instead of cream solder, a solder portion may be formed on the land by other means such as solder plating means or solder leveler means. Is. Further, the specific shape of the opening is not limited to the above-described embodiment, of course, the point is to have a shape having a narrow portion and a wide portion, and melted solder is attracted to the wide portion to generate a bulge portion. You can do it like this.

[0020]

According to the present invention, an opening having a narrow portion and a wide portion is formed in the solder resist film, and the land is partially exposed from the opening. Will be attracted to the wide portion to form a raised portion, and therefore, even if the lead has some floating, the lead can be grounded to the solder and reliably soldered. Further, the printed circuit board can be manufactured more easily than the conventional method of forming the narrow width portion or the wide width portion on the land itself, and the lead pitch can be easily reduced.

[Brief description of drawings]

FIG. 1 is a plan view of a printed circuit board according to a first embodiment of the present invention.

FIG. 2 is a partial perspective view of a printed circuit board according to a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a manufacturing process of the printed circuit board according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of a chip mounting process according to the first embodiment of the present invention.

FIG. 5 is a partial plan view of a printed circuit board according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Printed Circuit Board 2 Base Material 3 Land 4 Solder Resist Film 5 Opening 5a Narrow Part 5b Wide Part 6 Copper Foil 7 Solder Part 7a Rise Part 8 Chip 9 Lead

Claims (3)

[Claims] 1. A land and a solder resist film covering the land are formed on a surface of a base material, and an opening is formed in the solder resist film to partially expose the land, and the opening is narrow. A printed circuit board having a wide portion and a wide portion. 2. A land and a solder resist film covering the land are formed on the surface of a base material, and an opening is formed in the solder resist film to partially expose the land, and the opening is narrow. A printed circuit board having a portion and a wide portion, and a solder portion is formed on an upper surface of the land exposed at the opening. 3. A chip soldering method for soldering a chip to a printed circuit board coated with a solder resist film having an opening having a narrow portion and a wide portion for partially exposing a land. By forming a solder portion on the surface of the land exposed in the opening, the lead of the chip is located on the solder portion and the chip is mounted on the printed circuit board, by heating and melting the solder portion, A method for soldering a chip, characterized in that molten solder is attracted to the wide portion to be raised, and then the molten solder portion is solidified to solder the lead to the land.