JP2712601B2 - Method of manufacturing circuit board with built-in resistor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board having a built-in resistor and a method for manufacturing the same.

<Conventional technology> A resistor built-in substrate has a standard thickness of 70 μm or 35 μm,
An electrolytic copper foil of 18 μm is used for a highly conductive material layer, and a resistance material layer such as a nickel alloy and an insulating support are provided on one side of the layer by wet plating.

In order to form a circuit board with a built-in resistor from the substrate with a built-in resistor, a photoresist method is used. First, a combination pattern of a resistor pattern and a conductor pattern is covered with a photoresist, and the height of a portion other than the pattern is raised. The conductive material layer and the resistive material layer immediately thereunder are removed by corrosion, and then, while only the conductive pattern is covered, the portion of the high conductive material layer of the electrical resistance pattern is removed by corrosion to form a desired resistance circuit.

1 (a) to 1 (h) show a process of manufacturing a circuit board having a built-in resistor. FIG. 1A shows a substrate with a built-in resistor before processing, which is composed of a high conductive material layer 1, a resistance material layer 2, and an insulating support 3 in this order from the upper layer. First
FIG. 1B is a diagram in which a predetermined photoresist film 4 is provided on the surface of the above-mentioned resistor-containing substrate, and FIG. 1C shows a structure in which the highly conductive material layer 1 is selectively removed by etching. State. After that, the photoresist film 4
FIG. 1 (e) shows a state in which the resistive material layer is selectively removed while passing through (FIG. 1 (d)) and the photoresist film 4 is peeled off. At this time, a basic circuit pattern is formed. Then, a photoresist film 5 is provided again on the high conductive material layer 1 (FIG. 1 (f)), and the high conductive material layer 1 is selectively removed as shown in FIG. 1 (g). Thereafter, the photoresist film 5 is peeled off, and the highly conductive portions 6 as shown in FIG.
The formation of the resistance portion 7 and the insulating portion 8 on the insulating support 3 is completed.

As described above, in this step, the highly conductive material layer is subjected to at least two etching steps (FIG. 1B).
(C) and FIGS. 1 (f) to (g)).
In particular, the second etching step (FIGS. 1 (f) to (g))
Must be performed without corroding the resistive material layer immediately below the highly conductive material layer. In other words, the etchant used in this step must have selectivity for the highly conductive material layer and the resistive material layer. However,
The selectivity of the corrosiveness of the high conductive material layer which can be actually used is not so strict, and therefore, when the high conductive material layer is etched, the resistive material layer which is exposed from underneath is partially corroded and the resistance is lowered. The value will be increased, and will deviate from the desired resistance value. For example, using copper as a highly conductive material,
When a nickel alloy is used as the resistance material, an aqueous solution of ferric chloride, cupric chloride, or the like, which is most widely used as an etching solution for copper foil, is used for etching in FIGS. 1 (b) to 1 (c). Although there is no problem in the case of etching in FIGS. 1 (f) to 1 (g), it is impossible to use this kind of circuit board with a built-in resistor in view of the above selectivity. Was used. Nevertheless, the selectivity of the etching is not satisfactory, and therefore, care must be taken not to touch the etching solution as much as possible after the etching of the copper foil so that the exposed resistive material layer is formed. In addition, hexavalent chromium is harmful from the viewpoint of equipment and environment, so special equipment is required, and the work environment needs to be improved more than before in consideration of safety.

<Problems to be Solved by the Invention> The present invention is to solve the problem of insufficient selectivity of a high-conductivity material layer and a resistive material layer, which has been a problem in the past, by using a dedicated etchant by changing the etchant. Things.

<Means for Solving the Problems> That is, the present invention relates to a circuit board with a built-in resistor, from a substrate with a built-in resistor in which a resistance material layer made of a nickel alloy and a high conductor layer are formed on at least one surface of an insulating support. A method of using a solution of ammonium sulfate and copper sulfate (divalent copper ion concentration is 5 to 200 g /) and a hydroxide compound having a pH of 7.5 to 9.5 at the time of etching. This is a method for manufacturing a circuit board with a built-in resistor.

<Operation> A method for manufacturing a circuit board with a built-in resistor according to the present invention will be described in Examples, but an etching solution used in FIGS. 1 (f) to 1 (g) in manufacturing will be described.

The material structure of the circuit board with a built-in resistor in the present invention is shown in FIG. 1 (a) in which a resistive material layer made of a nickel alloy and a high conductor layer are formed on at least one surface of an insulating support. It is. The etching solution used in FIGS. 1 (b) to 1 (c) and FIGS. 1 (c) to 1 (d) is the same as the etching solution conventionally used, but is not changed in FIGS. 1 (f) to 1 (g).
As the etching solution in the above, the following solution of the present invention was used. Although a mixed solution of chromic acid and sulfuric acid has been used as a conventional etching solution in FIGS. 1 (f) to 1 (g), the lower resistive material layer is slightly etched when the highly conductive material layer is removed as described above. Resulting in. Also, since chromic acid is used, work cannot be performed in ordinary facilities and environment,
Special equipment is also required. The authors studied various reagents to solve the above points, and found that ammonium sulfate,
It has been found that the dissolution rate ratio between copper and nickel alloy is more than 1000: 1 when the liquid composed of copper sulfate (divalent copper ion concentration is 5-200 g /) and hydroxide compound is in the pH range of 7.5-9.5. I was sorry. The hydroxyl compound used herein refers to sodium hydroxide, potassium hydroxide, and ammonium hydroxide. At this time, the reaction formula in the chemical dissolution of copper is considered as follows.

Cu + Cu (NH ₃ ) ₄ ²⁺ → 2Cu (NH ₃ ) ₂ ⁺・ ・ ・ ・ (1) Cu (NH ₃ ) ₂₊ +1/40 ₂ + 2NH ₃ + 1 / 2H ₂ O → Cu (NH ₃ ) ₄ ^{2+ + OH - ···· (2) (} 1) formula is intended to indicate a dissolution of the copper, the copper is present as part ammonia complex.

The formula (2) shows a liquid recovery mechanism for oxidizing a monovalent copper complex ion to divalent and using it again in the reaction of the formula (1).

 Hereinafter, the present invention will be described in detail with reference to examples.

<Example> A glass epoxy material having a thickness of 1.6 mm as an insulating support on the circuit board, a 35 μm-thick electrolytic copper foil (manufactured by Nippon Mining Co., Ltd.) for a highly conductive material layer, and a thickness for a resistance material layer sandwiched in the center 0.
A resistor built-in substrate using a 4 μm Ni-P alloy was produced. Thereafter, the target circuit board is manufactured according to the steps shown in FIGS. 1 (a) to 1 (h).
In the steps of FIGS. (B) to (c), a ferric chloride solution was used as an etching solution and a spray method was used. Etching temperature is 40
C. and the etching time was about 2 minutes. The photoresist used at this time is a dry film (manufactured by DuPont). The etching of FIGS. 1 (c) to 1 (d) is performed by dipping the Ni-P alloy which is a resistive material layer with a mixed solution of copper sulfate and sulfuric acid through the predetermined photoresist film of FIG. 1 (b) as it is. And removed by etching. Etching temperature is 90
9595 ° C., the etching time was about 3 minutes. After that, the photoresist film used in FIG.
A predetermined photoresist film as shown in FIG. 1 (f) is provided, and pH 7.5 comprising ammonium sulfate / copper sulfate (divalent copper ion concentration is 20 to 40 g /) and a hydroxide compound, which is the point of the present invention, is used. Only copper, which is a high conductor layer on the resistance material layer, was etched by a spray method with a liquid in the range of 範 囲 9.5. Copper etching was performed under the conditions shown in Table 1, but the dissolution state of the Ni-P alloy after etching was only about 0.01 μm.

The photoresist used in FIG. 1 (f) is the same as the dry film used in the first patterning.

<Effect of the Invention> In the manufacturing process of the circuit board with a built-in resistor of the present invention,
By changing the chromic acid-sulfuric acid mixture used in the process to the solution according to the present invention, it was possible to provide a circuit board with a built-in resistor with high accuracy without erosion of the resistance material layer. . In addition, the problem of the working environment, which has been a problem in the past, has been eliminated, and the equipment has been simplified.

[Brief description of the drawings]

1 (a) to 1 (h) are explanatory views schematically showing steps of manufacturing a circuit board with a built-in resistor. DESCRIPTION OF SYMBOLS 1 ... High conductive material layer, 2 ... Resistive material layer 3 ... Insulating support, 4, 5 ... Photoresist film, 6 ... High conductive part, 7 ... Resistance part, 8 ... Insulating part,

Claims (1)

(57) [Claims] 1. A method for manufacturing a circuit board with a built-in resistor from a substrate with a built-in resistor, in which a resistive material layer made of a nickel alloy and a high-conductivity layer are formed on at least one surface of an insulating support, A method for manufacturing a circuit board with a built-in resistor, characterized by using a solution of ammonium sulfate / copper sulfate (divalent copper ion concentration: 5 to 200 g /) and a hydroxide compound in a pH range of 7.5 to 9.5.