JP2003298218A - Printed wiring board and mounting circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board and a mounting circuit board both of which can easily improve soldering reliability. <P>SOLUTION: A broad part 14b having a broader width than the terminal 14a of a circuit pattern 14 has is formed at the front end of the terminal 14a and the front end of the broad part 14b is electrically connected to a solder land 16. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a mounted circuit board, and more particularly to a printed wiring board and a mounted circuit board capable of improving the reliability of soldering with lead-free solder.

[0002]

2. Description of the Related Art Conventionally, there has been known a mounted circuit board in which electronic components such as capacitors, resistors, transistors, ICs and connectors are mounted individually or in combination on a printed wiring board. To mount an electronic component on a printed wiring board in such a mounting circuit board, insert the lead of the electronic component into a solder land formed so as to cover a through hole that is a component mounting hole of the printed wiring board, The structure that solders the solder land and the lead,
It is used for the reason that it is easy to increase the mounting strength of electronic parts on a printed wiring board.

FIGS. 4 and 5 show an example of a conventional mounting circuit board. A printed wiring board 2 of the conventional mounting circuit board 1 has an insulating substrate 3 formed of resin, A circuit (wiring) pattern 4 made of a conductor and having a predetermined shape is formed on both front and back surfaces of the insulating substrate 3. Further, the insulating substrate 3 is formed with a through hole 5 penetrating in the thickness direction for attaching the electronic component 8, and a solder land 6 is formed in the through hole 5. The solder land 6 has a cylindrical tubular portion 6a that covers the inner surface of the through hole 5 and a plane circle that extends radially outward from both ends of the tubular portion 6a along the surface of the insulating substrate 3. It is formed by a pair of upper and lower annular flange portions 6b, and the terminals 4a of the circuit pattern 4 are electrically connected to the outer peripheral edge of each flange portion 6b. Further, the circuit pattern 4 is covered with a protective film 7 except for the tip of the terminal 4a. The lead 8a of the electronic component 8 is inserted into the solder land 6 formed on the printed wiring board 2, and the solder land 6 and the lead 8a of the electronic component 8 are connected to each other. Solder 9 for electrically connecting 6 and the lead 8a of the electronic component 8 is provided by soldering. In the mounted circuit board 1 such as a liquid crystal display device to which high-density wiring is provided, the width of the terminal 4a of the circuit pattern 4 is about 60 μm, and the solder land 6 is used.
It is generally formed to be smaller than the inner diameter of.

[0004]

However, in the above-mentioned conventional mounting circuit board 1, the solder 9 and the printed wiring board 2 contract when the solder 9 in a molten state is solidified, and are exaggerated in FIG. As described above, land peeling occurs in which the connecting portion between the tip portion of the terminal 4a of the circuit pattern 4 and the flange portion 6b of the solder land 6 which is not covered with the protective film 7 peels off from the insulating substrate 3. There is a problem in that 4a may be disconnected, resulting in poor reliability of soldering. In FIG. 6, only land separation on the upper surface side of the insulating substrate 3 is shown, but land separation occurs on both the upper and lower surfaces of the insulating substrate 3. Further, such land peeling occurs remarkably when lead-free solder having a high melting temperature is used as the solder.

The present invention has been made in view of this point, and an object thereof is to provide a printed wiring board and a mounted circuit board which can easily improve the reliability of soldering.

[0006]

In order to achieve the above-mentioned object, the printed wiring board of the present invention according to claim 1 is characterized in that the solder lands formed in the through holes of the insulating substrate are insulated. In a printed wiring board that is electrically connected to the terminals of the circuit pattern formed on the board and is formed so that the leads of electronic components can be soldered to the solder lands, the width of the terminals can be A wider part having a wider width is formed, and the tip of the wide part is electrically connected to the solder land. And by adopting such a configuration, the wide portion,
Since the contact area with the insulating substrate is surely widened, it is possible to reliably maintain the adhesion between the wide portion and the insulating substrate, and
It is possible to shorten the cooling time when the molten solder solidifies in the vicinity of the wide portion and to increase the cooling rate. As a result, land peeling can be reliably and easily prevented,
The reliability of soldering can be easily improved.

The printed wiring board according to a second aspect of the present invention is characterized in that, in the first aspect, the base end side of the wide portion is covered with a protective film for protecting the circuit pattern and the front end side of the wide portion is included. The width of the externally exposed portion not covered by the protective film located at is formed to be greater than or equal to the minimum diameter of the inner circumference of the solder land and less than or equal to the maximum diameter of the outer circumference. By adopting such a configuration, it is possible to easily optimize the width of the wide portion.

A mounting circuit board according to a third aspect of the present invention is characterized in that, in a mounting circuit board in which electronic components are soldered to a solder land formed on the printed wiring board, the printed wiring board is claimed. The printed wiring board according to claim 1 or 2, wherein the solder used for soldering is lead-free solder. By adopting such a configuration, lead-free soldering parts can be easily achieved, and land peeling can be reliably and easily prevented, so that the reliability of soldering can be easily improved. And it can be ensured.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the embodiments shown in the drawings.

FIGS. 1 and 2 show a first embodiment of a mounting circuit board to which a printed wiring board according to the present invention is applied. FIG. 1 is an enlarged vertical sectional view showing an essential part, and FIG. It is a plan view of the main part of.

The mounted circuit board of this embodiment is exemplified by a liquid crystal display device or the like on which high-density wiring is provided.

As shown in FIG. 1, the printed wiring board 12 of the mounted circuit board 11 of this embodiment has a circuit pattern 14 of a predetermined shape formed on both front and back surfaces of an insulating substrate 13.
In addition, at a predetermined position of the insulating substrate 13, a through hole 15 penetrating in the thickness direction for mounting the electronic component 18 is formed.
Are formed, and solder lands 16 are formed in the through holes 15. The leads 18 a of the electronic component 18 are inserted inside the solder land 16.
Then, the solder land 16 and the lead 18 of the electronic component 18
Solder 19 for electrically connecting the solder land 16 and the lead 18a of the electronic component is provided between the solder land 16a and the lead 18a of the electronic component. The solder 19 is formed by soldering. The circuit pattern 14 may be formed on one surface of the insulating substrate 13.

As shown in FIGS. 1 and 2, the solder land 16 of the present embodiment has a cylindrical tubular portion 16a which covers the inner surface of a through hole 15 formed so as to penetrate the insulating substrate 13, and a cylindrical tubular portion 16a. From both ends of the tubular portion 16a, the insulating substrate 13
And a pair of upper and lower flange portions 16b having a planar annular shape and extending radially outward along the surface of the.

As shown in FIG. 2, a wide portion 14b wider than the width of the terminal 14a is formed at the tip of the terminal 14a of the circuit pattern 14 of this embodiment.
4b is the flange portion 16b of the solder land 16
Is electrically connected to the outer peripheral edge of. In addition, the wide portion 14
The base end side shown in the left side of FIG. 2 of FIG. 2B is covered with a protective film 17 that protects the circuit pattern 14. Further, the protective film 17 located on the tip side of the wide portion 14b shown on the right side of FIG.
The width of the external exposed portion 14ba which is not covered by
2 is formed to be larger than the minimum diameter of the inner circumference of the solder land 16 and smaller than the maximum diameter of the outer circumference shown by the reference numeral Max of FIG. If the width of the wide portion 14b exceeds this range, high-density wiring cannot be performed, and the solder 9 flows out when soldering is performed, so that fillets tend to be difficult to form. If the width of the wide portion 14b is less than this range, the adhesiveness between the wide portion 14b and the insulating substrate 13 cannot be maintained, and land separation tends to occur.

In the present embodiment, the circuit pattern 14
The width of the terminal 14a is about 60 μm, the inner diameter of the cylindrical portion 16a which is the minimum diameter of the inner periphery of the solder land 16 is about 1.1 mm, and the outer diameter of the flange portion 16b which is the maximum diameter of the outer periphery of the solder land 16 is 1 The wide portion 14b is formed to have a width of about 1.3 mm as shown in the vertical direction in FIG.
In this case, the length of the wide portion 14b is 0.3 m as the length of the external exposed portion 14ba which is the distance from the outer peripheral edge of the flange portion 16b of the solder land 16 to the protective film 17.
m, about 0.3 mm as the length capable of absorbing the forming accuracy of the protective film 17, and about 0.3 mm as the length of the portion covered by the protective film 17, a total of 0.9 mm
It is about degree. Although this length varies depending on the degree of high-density wiring of the mounting circuit board, the accuracy of forming the protective film 17 is taken into consideration in the design, and 1/4 or more of the length is the protective film 1
It is good to coat with 7.

The solder land 16 is referred to as a through hole plating hole. After the through hole 15 is formed in the insulating substrate 13 on which the circuit pattern 14, the terminal 14a and the wide portion 14b are formed, the solder land 16 is formed in the through hole 15. It is formed by plating and patterning. Copper plating is most commonly used as this plating.

The shape of the through hole 15 is as follows.
Circular according to the cross-sectional shape of the lead 18a of the electronic component 18,
Various shapes such as an elliptical shape, a semicircular shape, and a polygonal shape can be selected and used, and the shape is not particularly limited to the circular shape of this embodiment.

The flange portion 16 of the solder land 16
As the outer peripheral shape of b, various shapes such as a circle, an ellipse, a semicircle, and a polygon can be selected and used according to the shape of the through hole 15, and is particularly limited to the circle of the present embodiment. is not.

Therefore, the minimum diameter of the inner circumference of the solder land 16 of the wide portion 14b is an inscribed circle when the inner circumference of the cylindrical portion 16a of the solder land 16 is elliptical, semicircular or polygonal. Shows the diameter of. The maximum diameter of the outer periphery of the solder land 16 of the wide portion 14b indicates the diameter of the circumscribing circle when the outer peripheral shape of the flange portion 16b of the solder land 16 is elliptical or polygonal.

As the solder 19, Sn-Pb, S
Lead solder such as n-Ag-Pb, and Sn-Ag-
Lead-free solder such as Cu can be used, but it is preferable to use lead-free solder from the viewpoint of environmental pollution. Even if lead-free solder having a higher melting temperature than that of lead solder is used, the mounting circuit board 11 of the present embodiment can reliably prevent land separation and disconnection of the terminal 14a caused by thermal strain.

As the lead 18a of the electronic component, a copper wire whose surface is plated is generally used.
The lead 18a is plated with Sn, Ni
It is preferable to use -Pd plating in the sense that it is possible to prevent environmental pollution due to lead when the conventional Sn-Pb plating is applied.

As a method for soldering the leads 18a of the electronic component 18 and the solder lands 16 in this embodiment, a soldering iron using a soldering iron or a solder 19 in a molten state is stored and melted in a solder bath whose temperature can be adjusted. A method of supplying the solder 19 in a state to the soldering portion is selected and used according to needs such as the number of products produced and the design concept.

As the insulating substrate 13, a laminated plate is generally used in order to make it thin and to have sufficient strength, and a flexible substrate is used if necessary.

Further, as the protective film 17, a polyimide resin, an epoxy resin, an acrylic resin or the like can be selected and used.

Next, the operation of this embodiment having the above-mentioned structure will be described.

According to the mounting circuit board 11 of this embodiment,
The reliability of soldering can be easily improved.

That is, the mounted circuit board 11 of the present embodiment.
According to this, a wide portion 14b wider than the width of the terminal 14a is formed at the tip of the terminal 14a of the circuit pattern 14 of the printed wiring board 12, and the tip of the wide portion 14b is electrically connected to the solder land 16. Since the wide portion 14b is surely widened in contact with the insulating substrate 13 since it is connected, the adhesion between the wide portion 14b and the insulating substrate 13 can be surely maintained, and the melted state near the wide portion 14b can be maintained. The cooling time can be shortened by shortening the cooling time when the solder 19 solidifies. As a result, land peeling can be reliably and easily prevented, so that the reliability of soldering can be easily improved.

Further, according to the mounted circuit board 11 of the present embodiment, the base end side of the wide portion 14b of the printed wiring board 12 is covered with the protective film 17 which protects the circuit pattern 14, and the tip of the wide portion 14b. Protective film 1 located on the side
Since the width of the external exposed portion 14ba which is not covered by 7 is formed to be equal to or larger than the minimum diameter of the inner periphery of the solder land 16 and equal to or smaller than the maximum diameter of the outer periphery thereof, when the width of the wide portion 14b exceeds this range. It is possible to reliably prevent the inconvenience that high-density wiring is difficult to occur and the inconvenience that the fillet is difficult to be formed because the solder 9 flows out when soldering is performed. Adhesion between the wide portion 14b and the insulating substrate 13 that is generated cannot be maintained, and the disadvantage that land separation tends to occur can be reliably prevented. That is, the wide portion 1
4b can be easily optimized.

Further, according to the mounted circuit board 11 of the present embodiment, it is possible to easily and reliably achieve lead-free soldering and improve the reliability of soldering.

FIG. 3 shows a second embodiment of a mounted circuit board to which the printed wiring board according to the present invention is applied. In the mounted circuit board 11A of this embodiment, the width of the base end of the wide portion 14Ab formed at the tip of the terminal 14a of the circuit pattern 14 is set to the terminal 14a of the circuit pattern 14.
The width of the solder land 16
It is formed so as to gradually increase toward. In addition,
The width of the externally exposed portion 14Aba, which is not covered by the protective film 17 located on the tip side on the right side of FIG. 3 of the wide portion 14Ab, is equal to or larger than the minimum diameter of the inner circumference of the solder land 16 shown by the symbol Min in FIG. It is formed so as to hold a range equal to or smaller than the maximum diameter of the outer periphery of the solder land 16 shown by reference numeral Max in FIG. Other configurations are the same as those of the mounting circuit board of the first embodiment described above.

According to the mounting circuit board 11A having such a configuration, the same effects as those of the mounting circuit board 11 of the first embodiment described above can be obtained, and the circuit pattern 1 can be obtained.
It is possible to easily avoid sharp bending of the connecting portion between the terminal 14a of No. 4 and the wide portion 14Ab.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made as necessary.

[0033]

As described above, according to the printed wiring board of the present invention according to claim 1, land peeling can be reliably and easily prevented, so that the reliability of soldering can be easily improved. Has an extremely excellent effect.

Further, according to the printed wiring board of the present invention according to the second aspect, there is an extremely excellent effect that the width of the wide portion can be easily optimized.

According to the third aspect of the mounted circuit board of the present invention, it is possible to easily achieve lead-free soldering and to reliably and easily prevent land peeling. It has an extremely excellent effect that the reliability of attachment can be easily and surely improved.

[Brief description of drawings]

FIG. 1 is an enlarged vertical cross-sectional view showing a main part of a first embodiment of a mounted circuit board to which a printed wiring board according to the present invention is applied.

FIG. 2 is a plan view of a main part of FIG.

FIG. 3 is a view similar to FIG. 2 showing a main part of a second embodiment of a mounted circuit board to which a printed wiring board according to the present invention is applied.

FIG. 4 is an enlarged vertical sectional view showing a main part of a conventional mounting circuit board.

5 is a plan view of the main part of FIG.

FIG. 6 is an enlarged vertical cross-sectional view showing land separation in a conventional mounting circuit board.

[Explanation of symbols] 11, 11A mounting circuit board 12 Printed wiring board 13 Insulation board 14 circuit patterns 14a terminal 14b, 14Ab wide part 14ba, 14Aba Externally exposed part 15 through holes 16 Solderland 17 Protective film 18 electronic components 18a lead 19 solder

Claims (3)

[Claims] 1. A solder land formed in a through hole of an insulating substrate is electrically connected to a terminal of a circuit pattern formed on the insulating substrate, and a lead of an electronic component is soldered to the solder land. In a printed wiring board that can be attached, a wide portion that is wider than the width of the terminal is formed at the tip of the terminal, and the tip of the wide portion is electrically connected to the solder land. A printed wiring board characterized in that 2. A base end side of the wide portion is covered with a protective film that protects the circuit pattern, and a width of an externally exposed portion that is located on the tip end side of the wide portion is not covered by the protective film. A printed wiring board, wherein the printed wiring board is formed so as to have a diameter not less than the minimum diameter of the inner circumference of the solder land and not more than the maximum diameter of the outer circumference. 3. A mounted circuit board in which electronic components are soldered to a solder land formed on the printed wiring board, wherein the printed wiring board is the printed wiring board according to claim 1 or 2. A mounted circuit board, wherein the solder used for the soldering is lead-free solder.