JPH02121386A - Printed resistor board - Google Patents

Abstract

PURPOSE:Not only to improve a circuit design in the degree of freedom but also to increase a board in density by a method wherein an opening of a hole structure is covered with a resin layer to form a planar base, and a resistor is printed on the base. CONSTITUTION:A printed resistor board is constituted in such a manner that resin 5 is filled into a through-hole 4 which is provided to a board 1 and made electrically conductive by plating its inner wall by copper, resin layer 5 is provided onto a region which includes the opening of the through-hole 4 to form a base, and a resistor 7 is printed on the base. The resin layer 3 covering the through-hole 4 meets characteristics required as a base layer for a printed resistor and enable the excellent resistor 7 to be formed thereon, and it can be obtained by forming a hardened film of photosensitive resin such as liquid solder resist or the like into a required pattern. The printed resistor 7 is formed of resistive paste after a silver electrode 6 has been formed of silver paste on a copper electrode 2 of a copper pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printed resistor board having a printed resistor that can be used in electronic equipment such as VTRs, radios, and televisions.

[Prior Art] In circuit boards equipped with low-resistance (printed resistors) formed by screen printing or photolithography, it is necessary to connect wiring below the printed resistors in order to increase the degree of freedom in circuit design. is being carried out.

For wiring to the bottom of such a printed resistor, a layer of insulating paste is placed on the signal line or electrode wiring made of a conductive material such as copper placed on the board, and then the resistor is printed on the insulating layer. It is obtained by doing.

[Problem to be solved by the invention] Even in the case of a circuit board having a hole structure such as a through hole or a blind hole, the degree of freedom in circuit design can be further increased by providing a printed resistor over the through hole or blind hole. can be increased.

However, no structure has yet been found that allows for the formation of through holes, blind holes, etc. on printed resistors.

For example, if the technique using an insulating paste layer as described above is applied as is to cover an opening such as a through hole, the thickness of the paste layer covering the opening may not be uniform, or the paste layer may not be thick enough. A step may occur in the portion corresponding to the opening, making it difficult to obtain the smoothness necessary for forming a good printed resistor. As a result, it is not possible to stably obtain a predetermined resistance value for the resistor printed on the paste layer,
The low antibodies formed are unreliable.

Further, in such a structure, the insulation properties of the insulation paste layer itself tend to be unreliable.

Furthermore, if the opening, such as a through hole, is large, the opening cannot be covered with the insulating paste layer, making it impossible to form a printed resistor over the opening.

Therefore, through holes and the like have conventionally been arranged avoiding areas where printed resistors are formed.

The purpose of the present invention is to provide a configuration in which hole structures such as through holes can be freely formed under the printed resistor, thereby realizing higher density and smaller size of the printed resistor board, An object of the present invention is to increase the degree of freedom in designing a circuit board such as a printed wiring board that has a printed resistance board as a part of its configuration.

[Means for Solving the Problems] The printed resistor board of the present invention is characterized in that a base is provided in the openings of hole structures such as through holes and blind holes of the board to enable formation of good printed resistors. Features.

This base is formed by covering the opening with a resin layer or by providing a resin layer over the opening of the pore structure that is closed by filling with a filler.

Note that circuit boards such as printed wiring boards that include the printed resistance board of the present invention as part of their configuration are also included within the scope of the present invention.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

1 and 2 are cross-sectional views showing the formation process of an embodiment of the printed resistance substrate of the present invention, and FIG. 3 is a plan view of the printed resistance substrate shown in FIG. 2.

In the printed resistance board shown in these figures, a through hole 4 made of conductive copper plating on the inner wall surface of a through hole of a board 1 is filled with resin 5, and a region including the opening of the through hole is filled with resin. It has a structure in which a layer 3 is provided to form a base, and a resistor 7 is printed on the base.

In this example, an electrode 2 made of a copper pattern is connected to the resistor 7 via a silver electrode 6 made of silver paste.
Further, an overcoat layer 8 is provided.

As the substrate 1, those commonly used for forming printed resistance boards, printed wiring boards, etc. can be used.

As the resin 5 filled in the through hole 4, the resin layer 3
Any material can be used as long as it can obtain a filling state that allows smooth formation of the material. For example, an insulating resin such as a solder resist can be used.

Further, the through hole 4 may be filled with a conductive material, and in that case, solder, silver paste, copper paste, etc. can be used.

Note that when silver paste or copper paste is used, the copper plating in the through holes 4 in FIGS. 1 and 2 can be omitted.

The resin layer 3 covering the through-hole 4 may be made of any material as long as it satisfies the characteristics as a base layer of a printed resistor and allows formation of a good printed resistor 7 on top of the resin layer 3. Anything is fine.

Specifically, this resin layer 3 is formed by, for example, forming a cured film of a photosensitive resin such as a liquid type solder resist in a predetermined pattern, or by forming a photosensitive resin film such as a dry film type solder resist in a predetermined pattern. It can be obtained by buttering the shape.

Note that when a photosensitive resin film is used, it is possible to cover the opening of the through hole 4 without filling it with a filler, and a smooth base for forming the printed resistor can be obtained.

In this case, the diameter of the through hole 4 is 0.5+n
The thickness is preferably 0.3 mm or less, particularly preferably 0.3 mm or less.

Further, the thickness of the photosensitive resin film in this case is preferably as thick as possible, or for example, preferably 115 times or more the diameter of the through hole 4.

The copper electrode 2 and the silver f electrode 6 are provided for wiring to the printed resistor 7, and their arrangement is not limited to the illustrated example. These may be formed using materials commonly used in this field.

Further, the overcoat layer 8 is provided as necessary to prevent the printed resistor 7 from absorbing moisture, and can be made of, for example, epoxy resin, melamine resin, phenol resin, or the like.

A specific example of the method for forming the illustrated printed resistor will be shown below.

First, we started with a glass epoxy resin substrate with a copper thickness of 18 μm (
A through hole 4 (inner diameter: 0) having a copper pattern 2 with a thickness of approximately 48 μm and a conductive layer made of copper with a thickness of approximately 30 μm was formed in a TL (Nie 551) manufactured by Toshiba Chemical Corporation using a normal method.
．． 3mm) to obtain the printed wiring board 1, the first
As shown in the figure, the inside of the through hole 4 was filled with epoxy resin as the resin 5 and cured.

Next, a photosensitive solder resist film (trade name: manufactured by Hitachi Chemical Co., Ltd.) Otec SR-130 with a thickness of about 75 μm was applied.
0G) was laminated on a substrate, exposed and developed to form a pattern (3) made of a predetermined cured resin, and at the same time, the through hole 4 was covered and insulated.

Next, as shown in FIG. 2, a silver electrode 6 was formed using silver paste on the copper electrode 2 of the copper pattern, and then a printed resistor 7 was formed using resistance paste.

Finally, a paste mainly composed of epoxy resin was formed on the printed resistor by screen printing to prevent moisture absorption, and then cured to form an overcoat layer 8 to obtain a printed resistor board. .

The thus obtained printed resistor on the through hole had performance and reliability equivalent to that of the printed resistor provided on the substrate without the through hole.

Further, a printed resistance board can be obtained in the same manner as described above, except that after filling the through holes with resin, an insulating paste is applied to predetermined portions including the openings of the through holes to form an insulating layer.

The thickness of the insulating paste layer at this time is preferably about 75 μm when the inner diameter of the through hole is 0.3 mm.

Although the present invention has been described above with respect to a substrate having through holes, the present invention is not limited thereto, and the configuration of the present invention can be applied to forming a printed resistor on a similar hole structure such as a blind hole.

Further, as the materials that can be used to form the printed resistance substrate of the present invention, those commonly used in this field can be used.

[Effects of the Invention] According to the present invention, since a hole structure such as a through hole can be freely provided in the portion of the circuit board where the printed resistor is formed, the degree of freedom in circuit design can be increased and at the same time , high density substrates can also be achieved.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the process of forming a printed resistor substrate of the present invention, and FIG. 3 is a plan view of FIG. 2. 1 Niblint wiring board 2: Copper electrode 3; Photosensitive solder resist film 4 Varnish through hole 5: Resin 6: Silver electrode 7: Printed paper body 8 Ni-barcode

Claims (1)

[Scope of Claims] 1) A printed resistance board, characterized in that the openings of the hole structure of the board are covered with a resin layer to form a planar base, and a resistor is printed on the base. 2) The printed resistance board according to claim 1, wherein the hole structure is filled with a filler. 3) The printed resistance board according to claim 2, wherein the filler is a conductive material. 4) The printed resistance board according to claim 2, wherein the filler is an insulating material. 5) The printed resistance board according to claim 4, wherein the filler is an insulating resin material.