JP6806526B2 - Printed wiring board - Google Patents

Description

The present disclosure relates to a printed wiring board in which short circuit defects of wiring are suppressed.

A semi-additive method is mentioned as one of the methods for forming wiring on a substrate. This semi-additive method includes, for example, steps (1) to (5) shown below.
(1) A seed layer of electroless copper plating is formed on the insulating material.
(2) Form a plating resist for a dry film.
(3) Exposure and development are performed to remove the plating resist other than the conductor portion.
(4) A conductor is formed by electrolytic pattern copper plating at a portion where the plating resist has been removed, and the plating resist is peeled off.
(5) The electroless copper plating of the seed layer is removed by flash etching to form wiring.

As shown in Patent Document 1, for the convenience of design, the wiring may be bent from a straight portion to change the traveling direction so as to avoid conductors such as a land on a board and a pad for mounting a component. ..

Jitsukaisho 62-190369 Gazette

The printed wiring board of the present disclosure includes a substrate, a conductor constituting at least one of a land and a pad arranged on the substrate, and a wiring arranged on the substrate, and the wiring is formed so as to avoid the conductor. , A gap is provided between the conductor and the wiring, and in the gap provided around each of the conductors, there are two or less portions narrower than the wiring width of the wiring avoiding the conductor. It is characterized by.

It is explanatory drawing which shows one Embodiment of the printed wiring board of this disclosure. (A) is an enlarged explanatory view of a portion of wiring according to the printed wiring board of the present disclosure, and (b) is an enlarged explanatory view showing another embodiment of wiring. It is an enlarged explanatory view which shows the other embodiment of the printed wiring board of this disclosure.

When wiring is formed on a substrate by adopting the above-mentioned semi-additive method, the dry film may expand or contract due to swelling (development) or temperature change (particularly before and after drying) in a developing or drying process. In this case, if the wiring is straight, the dry film is evenly contracted along the wiring, so that it is difficult to peel off. However, as the wiring is refined, the contact area between the dry film and the insulating material tends to be narrowed. Therefore, in the portion where the wiring is bent, only an inward contraction force is generated in the bending direction, so that the dry film is likely to be peeled off. Further, depending on the relationship between the wiring width and the gap, the dry film is likely to peel off due to the flow of the developing solution. When the dry film is peeled off, the electrolytic pattern copper plating sneaks into the peeled gap at the bottom of the dry film. As a result, conductors such as lands and pads that are close to the wiring, or wirings are erroneously connected to each other, resulting in a short circuit failure.

In the printed wiring board of the present disclosure, the wiring arranged on the substrate is formed so as to avoid the conductor arranged on the substrate, and a gap is provided between the conductor and the wiring. In the gaps provided around each of the conductors, there are two or less portions narrower than the wiring width of the wiring. Therefore, according to the printed wiring board of the present disclosure, it is possible to suppress the occurrence of short-circuit defects between the wiring and the conductor constituting at least one of the land and the pad, and large-scale short-circuit defects in the peripheral portion. The reason why the gap between the wiring and the conductor has such a width is that when the printed wiring board is manufactured, the contact area between the dry film and the insulating material is widened at the bending point where the stress of the dry film is concentrated. It comes from doing. As a result, the peeling of the dry film is suppressed, and the sneaking of the copper plating is also suppressed.
Further, when forming a land as a conductor on a substrate, in the land of the laser via, the insulating material of the substrate around the land is roughened due to the influence of the heat of the laser, the adhesion with the dry film is lowered, and a short circuit defect Tends to occur easily. Therefore, if the gap between the wiring and the conductor is formed as described above, the progress of roughening of the insulating material can be suppressed and the occurrence of short-circuit defects can be suppressed.

A printed wiring board according to an embodiment of the present disclosure will be described with reference to FIG. As shown in FIG. 1, the printed wiring board 10 includes a substrate 1, wiring 2, and a conductor 3.

The substrate 1 is not particularly limited as long as it is made of a material having an insulating property. Examples of the insulating material include organic resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. Two or more kinds of these organic resins may be mixed and used. When an organic resin is used as a material having an insulating property, a reinforcing material may be mixed with the organic resin and used. Examples of the reinforcing material include insulating cloth materials such as glass fiber, glass non-woven fabric, aramid non-woven fabric, aramid fiber, and polyester fiber. Two or more types of reinforcing materials may be used in combination. Further, the insulating material may contain an inorganic filler such as silica, barium sulfate, talc, clay, glass, calcium carbonate and titanium oxide.

The substrate 1 may have a single-layer structure, or may have a multi-layer structure in which two or more insulating layers formed of the above-mentioned insulating material are laminated. In addition to the wiring 2, the substrate 1 may be formed with, for example, a conductor layer (not shown) such as a power supply layer (solid layer) and a ground layer (solid layer). Further, the substrate 1 may be provided with a solder resist layer (not shown) in order to protect the wiring. The substrate 1 usually has a quadrangular shape. The substrate 1 may have a size of about 5 mm in length and 5 mm in width to 80 mm in length and 80 mm in width.

As shown in FIG. 1, the wiring 2 is formed so as to surround a part of the conductor 3 along the periphery thereof and to avoid the conductor 3 arranged on the substrate 1. The wiring 20 connected to the wiring 2 refers to a wiring unrelated to avoiding the conductor 3. The upper limit of the width of the wiring 2 may be 30 μm or 20 μm in consideration of the comparison with the diameter of the conductor 3 and the refinement of the wiring. The number of wirings 2 may be plural, and for example, a pair of two wirings may be double wirings in parallel.

The wiring 2 is made of a conductor. Examples of the conductor include copper, aluminum, gold, silver and the like. Copper should be used in consideration of workability and cost. The wiring 2 is formed of, for example, chemical (electroless) plating such as chemical copper plating (electroless copper plating), electrolytic plating such as electrolytic copper plating, and metal foil such as copper foil. It may be formed by plating a metal foil such as copper foil with copper plating or the like.

At least one conductor 3 is arranged on the substrate 1, constitutes at least one of a vialand or a pad for mounting a component connected to the wiring conductor, and electrically connects the mounted component (not shown) and the printed wiring board 10. It is to connect to the target. The conductor 3 may be formed of, for example, a copper foil and may have a diameter of 100 μm or less, or 90 μm or less. The shape of the conductor 3 may be circular, elliptical, polygonal or the like.

A plurality of gaps 4 are provided between the wiring 2 and the conductor 3. The gap 4 means the width of a perpendicular line from any one point on the periphery of the conductor 3 closest to the wiring 2 to the wiring 2 adjacent to the wiring 2. If the gap 4 is wide, the dry film is less likely to peel off and short circuit defects can be suppressed. However, since the wiring 2 needs to be arranged in the limited space of the substrate 1, expanding the gap 4 infinitely is a layout. It is difficult to do. Therefore, with respect to the plurality of gaps 4 provided around the conductor 3, the portion narrower than the wiring width 21 of the wiring 2 avoiding the conductor 3 is suppressed to two or less places, so that the dry film is less likely to peel off. Short-circuit defects can be suppressed. Of the gap 4, the portion narrower than the wiring width 21 may or may not be one as long as it is two or less.

As shown by an arrow in FIG. 2A, the wiring 2 is shifted to the space above and below the conductor 3, and in the gap 4 between the conductor 3 and the wiring 2, there is one gap 42 in a portion wider than the wiring width 21. Form. At this time, two gaps 41 are formed in a portion narrower than the wiring width 21. As a result, peeling of the dry film is less likely to occur, and short-circuit defects can be suppressed.
Further, as shown in FIG. 2B, if the number of gaps 42 with respect to the wiring 2 is increased among the gaps 4 provided around the conductor 3 so that the gaps 42 are two and the gaps 41 are one. , It can be expected to suppress short circuit defects.

The width of the gap 41 is not particularly limited as long as it is narrower than the wiring width 21, and may be 30 μm or less, or 18 μm or less. If the gap 41 and the wiring width 21 have the same width, a short circuit defect does not occur. The width of the gap 42 is not particularly limited as long as it is wider than the wiring width 21. When a gap 42 is formed and there is another wiring (not shown) in the direction in which the wiring 2 shifts, the wiring is also shifted in the same direction as the wiring 2 to suppress a short circuit defect between the wirings. The gap between the wiring 2 and another wiring is not particularly limited, but the wiring width of the wiring 2 is preferably 21 or more.

(Other embodiments)
FIG. 3 shows another embodiment of the present disclosure. The same members as those described above are designated by the same reference numerals, and the description thereof will be omitted. On the substrate 1, the wiring 2 is arranged in a substantially V shape so as to surround the conductor 3. In the present specification, the "substantially V-shaped" also includes a substantially U-shaped and a substantially U-shaped.

As shown in FIG. 3, the angle θ of the intersection of the outermost wires 23 and 23 surrounding the conductor 3 of the wiring 2 on the extension line may be 110 degrees or more, and the upper limit thereof may be less than 180 degrees. Good.

Hereinafter, the printed wiring board of the present disclosure will be specifically described with reference to examples, but the printed wiring board of the present disclosure is not limited to these examples.

(Example 1)
The printed wiring board was formed by a known semi-additive method. First, a dry film (plating resist) (RD series manufactured by Hitachi Kasei Co., Ltd.) having a thickness of 25 μm was formed on the surface of the seed layer of the substrate, and exposed and developed. Next, the plating resist other than the conductor portion was removed, and a wiring having a wiring width of 30 μm and a conductor having a diameter of 95 μm as a land were formed by electrolytic pattern copper plating. At this time, the wiring was formed so as to avoid the conductor and the land, and the gap between the wiring and the other wiring was secured to be at least the same length as the wiring width. Of the gaps between the conductor and the adjacent wiring, there were two locations narrower than the wiring width. Next, the remaining dry film was peeled off and the seed layer was removed by flash etching. During the manufacture of the printed wiring board, no dry film peeling occurred between the wiring and the conductor. In this way, a printed wiring board was obtained in which the gap between the wiring and the conductor to be avoided by the wiring was less than the wiring width (30 μm) at two locations between the plurality of wirings and the conductor. In the obtained printed wiring board, short-circuit defects did not occur between the wiring and the conductor and between the wiring and other wiring.

(Example 2)
A printed wiring board was obtained in the same procedure as in Example 1 except that the wiring width of the wiring was changed to 18 μm. In the obtained printed wiring board, there were two places where the gap between the wiring and the conductor was less than the wiring width (18 μm). During the production of this printed wiring board, the dry film did not peel off. In the obtained printed wiring board, a short circuit defect did not occur between the wiring and the conductor.

(Comparative Example 1)
A printed wiring board was obtained in the same procedure as in Examples 1 and 2 except that the wiring width of the wiring was changed to 20 μm. In the obtained printed wiring board, there were three places where the gap between the wiring and the conductor was less than the wiring width (20 μm) of the wiring. During the production of the printed wiring board, a part of the dry film was peeled off. As a result, in the obtained printed wiring board, short-circuit defects occurred between some wirings and between the wirings and the conductors.

As described above, in the printed wiring boards obtained in Examples 1 and 2, the portion of the gap provided between the conductor and the wiring that is narrower than the wiring width of the wiring formed so as to avoid the conductor is There were two or less locations, and no short circuit failure occurred. On the other hand, in the printed wiring board obtained in Comparative Example 1, there were three portions of the gap between the wiring and the conductor narrower than the wiring width, and the obtained printed wiring board had a short circuit defect.

1 Substrate 2, 20, 23 Wiring 21 Wiring width 3 Conductor 4, 41, 42 Gap 10 Printed wiring board

Claims (4)

With the board
A conductor forming at least one of the lands and pads disposed on said substrate,
Wherein the wiring disposed on the substrate,
The wiring is to bypass the conductors are arranged to have a gap between said conductors,
The gap is one place narrow portion than the width of the wiring or printed circuit board narrow part than the width of the wiring is characterized in that it is a two places. The gap is composed of one portion narrower than the width of the wiring and two portions wider than the width of the wiring, or two portions narrower than the width of the wiring and wider than the width of the wiring. The printed wiring board according to claim 1, wherein the portion is configured in one place . The printed wiring board according to claim 1 or 2, wherein the wiring is arranged in a substantially V shape so as to surround the conductor. The printed wiring board according to any one of claims 1 to 3 , wherein the wiring is a pair of parallel dual wirings .

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