JPH02301187A - Manufacture of both-sided wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a double-sided wiring board, and more particularly to a method for achieving electrical conduction between the front and back surfaces of a double-sided wiring board.

[Prior Art J Conventional Art 1 A double-sided wiring board to which wiring patterns on both the front and back sides are connected is manufactured by the following method. first,
Metal foils such as copper are laminated on the front and back surfaces of a substrate made of an insulating film or the like. Thereafter, a through hole is formed from the metal foil on the front surface through the substrate to the metal foil on the back surface by machining such as punching or drilling. Thereafter, a base plating layer is formed on the entire surface of the metal foil including the inner surface of the through hole by electroless plating. Then, a resist is patterned on the metal foil on the front and back sides excluding the wiring pattern forming areas corresponding to the front and back sides of the board at the locations of the through holes, and using this resist as a mask, copper etc. are applied to the base plating layer of the wiring pattern forming areas including the through holes. A plating layer is formed by electrolytic plating. Finally, the resist is removed to expose the base plating layer, and using the plating layer as a mask, the base plating layer and the metal foil are sequentially etched to remove unnecessary portions. As a result, three layers consisting of a plating layer, a base plating layer, and a metal foil are formed on the front and back surfaces of the board.
A layered wiring pattern is formed by being connected at the through hole.

[Problem to be Solved by the Invention J However, in the method for manufacturing a double-sided wiring board as described above, it is necessary to laminate metal foil on the front and back surfaces of the board in advance, and after that, one through hole is formed, At the very least, a base plating layer and a plating layer are formed on the inner surface, and then the first laminated metal foil is etched to form wiring patterns on the front and back surfaces of the board, which requires a large number of manufacturing steps. However, there are problems in that manufacturing operations are complicated, productivity is low, and costs are high.

In order to solve this problem, a method of filling the through holes with conductive paste has been considered, but since conductive paste is made by mixing conductive particles such as carbon into the paste, the electrical resistance is low. It has a problem of high value and lack of reliability in terms of weather resistance and current capacity.

An object of the present invention is to provide a method for manufacturing a double-sided wiring board that does not use conductive paste, simplifies the manufacturing process, has good productivity, and can ensure continuity between wiring patterns on both the front and back sides. be.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention forms a through hole penetrating the insulating film from the front surface to the back surface by machining such as a drill or a press. After forming a metal I film on the front and back surfaces and the inner surface of the through hole by vapor deposition or sputtering, a plating layer is patterned on the metal thin film in the corresponding wiring pattern forming area at least at the location of the through hole, and finally the metal By etching the thin film and removing unnecessary parts, a two-layer wiring pattern consisting of a plating layer and a gold i thin film is formed with electrical continuity at the through hole.

[Function] According to the present invention, a through hole is first formed in an insulating film, and then a metal thin film and a plating layer are sequentially laminated and etched on the surface of the insulating film including the inner surface of the through hole. As a result, a two-layered wiring pattern consisting of a plating layer and a thin metal film is made conductive at the through-holes, eliminating the need for the conventional process of laminating metal foil on the front and back sides of an insulating film. In addition, the process of etching the metal foil to form a wiring pattern becomes unnecessary. This makes it possible to simplify the manufacturing process, improve productivity, and reduce manufacturing costs. In this case, after forming a through hole in the insulating film, a metal thin film is formed by vapor deposition or sputtering on the front and back surfaces of the insulating film and the inner surface of the through hole. A thin metal film can also be easily formed on the inner surface of the hole. Moreover, since this metal thin film serves as the base plating for the plating layer, a plating layer can be easily and favorably formed on the surface of the metal thin film in a subsequent process. Thereby, conduction between the front and back wiring patterns can be ensured by the metal thin film and plating layer formed on the inner surface of the through hole.

[First Embodiment] The manufacturing method of the first embodiment of this invention 11 will be explained below with reference to FIG.

First, as shown in FIG. 1(A), an insulating film 1 is prepared. This insulating film 1 is made of synthetic resin such as polyimide, polyester, glass epoxy, etc., and is formed into a sheet shape. Then, as shown in FIG. 1(B), a through hole 2 penetrating from the front surface to the back surface is formed in the insulating film 1 by machining such as a drill or a press.

Next, as shown in FIG. 1C, a metal thin film 3 is formed on the front and back surfaces of the insulating film 1 and the inner surface of the through hole 2 by vapor deposition or sputtering.

This metal is thin! 13 is made of a metal such as copper (Cu) or aluminum (A1), and is formed to have a thickness of about several hundred λ to several thousand λ. In this case, the metal i-film 3 is continuously formed through the through hole 2 over the front and back surfaces of the insulating film 1. Of course, in reality, this vapor deposition or sputtering is performed twice, on the front and back surfaces of the insulating film 1, but the attachment of the metal thin film 1lI3 to the 1 through hole 2 is performed on both of them, making it more reliable. .

Thereafter, as shown in FIG. 1(D), a plating layer 4 is formed on the entire surface of the metal thin film 3 by electrolytic plating. Since the metal thin film 1193 serves as the base plating for this plating layer 4, it can be easily formed on the surface of the metal thin film 3 by electrolytic plating. It is also formed on the surface of 13. In this case, the material of the plating layer 4 is the metal thin 159 mentioned above.
It may be the same as 3, but it may be different.
Moreover, the thickness of this plating layer 4 is formed to be approximately aJLm to several tens of gm.

After this, as shown in FIG. 1(E), the insulating film l
In the plated layers 4 on the front and back sides, a resist 5 is formed by screen printing, photo patterning, or the like in wiring pattern formation regions whose portions correspond to each other at the locations of the through holes 2. As this resist 5, a thermofusible resin, a photoresist, or the like is used. When the resist 5 is formed by screen printing, it is formed by printing the resist on the insulating film l through a screen. In addition, when forming the resist 5 by a photo patterning method, the photoresist is formed on the entire surface of the insulating film 1. A pattern is formed by exposing the photoresist to light through a mask and developing it.

Thereafter, as shown in FIG. 1(F), using the resist 5 as a mask, the plating layer 4 and the metal thin film 3 are sequentially etched to remove unnecessary parts, that is, areas other than the wiring pattern forming area where the resist 5 is not formed. The plating layer 4 and metal film 3 are removed.

In this case, if the plating layer 4 and the metal thin film 3 are made of the same material, they can be etched simultaneously in one etching process, but if they are made of different materials, each layer 3 and 4 is etched separately.

Finally, as shown in FIG. 1 (CG), the resist 5 is removed. In this case, the resist 5 is removed by heating and melting, or by etching. When the resist 5 is removed in this way, a two-layer wiring pattern 7 consisting of the plating layer 4 and the metal thin film 3 is formed.

In this wiring pattern 7, portions corresponding to the front and back sides of the insulating film 1 are electrically connected to each other at the location of the through hole 2.

As a result, a double-sided wiring board in which the wiring pattern 7 is electrically connected to the front and back surfaces of the insulating film 1 at the through holes 2 is obtained.

Therefore, according to the method for manufacturing a double-sided wiring board as described above, the through holes 2 are first formed in the insulating film l, and then the entire surface of the insulating film l including the inner surface of the through holes 2 is coated with metal. While forming the thin film 3, this metal thin film 3
A plating layer 4 is formed on the entire surface of the etching layer 4, and finally, the plating layer 4 and the metal thin film 3 are sequentially etched using the resist 5 as a mask, thereby forming a two-layer wiring pattern 7 consisting of the metal thin layer 13 and the plating layer 4. It can be formed to be electrically conductive at the location of the through hole 2. Therefore, there is no need to laminate metal foil on the insulating film in advance as in the past, and there is also no need to etch this metal foil to form a wiring pattern, which greatly simplifies the manufacturing process. It is possible to manufacture double-sided wiring boards with good productivity and efficiency.

In this case, in particular, after forming the through holes 2 in the insulating film 1, the metal thin film 3 is formed on the entire surface of the insulating film 1 and the inner surface of the through holes 2 by vapor deposition or sputtering. Metal QI15I3 can be formed not only on the front and back surfaces but also on the inner surface of the 1 through hole 2. Moreover, since the metal thin film 3 formed in this manner serves as the base material for the plating layer 4, the plating layer 4 can be easily and favorably formed on the surface of the metal thin W23 by electrolytic plating. As a result, wiring patterns 7 corresponding to each other at the through holes 2 are formed by the metal thin film 3 and the plating layer 4, and the wiring patterns 7 on the front and back sides are formed by the metal thin film 3 and the plating layer 4.
are reliably connected by the metal thin film 3 and plating layer 4 formed on the inner surface of the through hole 2. In particular, the metal thin film 3 and plating layer 4 formed on the inner surface of the first through hole 2 are compared to conductive paste.

It has a low electrical resistance value and is highly reliable in terms of resistance and current resistance, so the wiring patterns 7 on the front and back sides can be reliably connected, resulting in extremely high continuity reliability. .

[Second Embodiment 1 Next, referring to FIG. 2, a manufacturing method according to a second embodiment of the present invention will be described. In this case, the same parts as in the first embodiment described above are given the same reference numerals, and the explanation thereof will be omitted.

Similar to the above embodiment, a through hole 2 penetrating from the front surface to the back surface is formed in the insulating film l in advance, and a metal R film is formed on the front and back surfaces of the insulating film l and the inner surface of the through hole 2 by vapor deposition or sputtering. form 3. Thereafter, as shown in FIG. 2(A), a pattern of resist 5 is formed on the thin metal W 23 except for the wiring pattern forming area corresponding to 1 at the location of the through hole 2 in the same manner as in the embodiment described above. . As a result, only the metal thin film 3 in the wiring pattern forming area is exposed.

Thereafter, as shown in FIG. 2(B), a plating layer 4 is formed on the exposed surface of the metal thin film 3 by electrolytic plating.

In this plating layer 4, since the metal thin film 3 serves as the base plating as in the above-mentioned embodiment, the metal thin film 3 is easily exposed by electrolytic coating. 3, but not at all on the surface of the resist 5. This is because metal particles of the plating solution do not adhere to the surface of the resist 5 due to electrolytic plating. In this case, the thickness of the plating layer 4 is finally formed to be approximately several JLm to several tens of meters, but if the material of the plating layer 4 is the same as that of the metal thin film 3, the thickness of the plating layer 4 is Since the plating layer 4 is etched, it should be formed as thick as the thickness of the metal thin film 3 in advance in anticipation of this. Also, if the material of the plating layer 4 is different from the metal thin film 3, the metal thin W
Since it is not etched at the same time as J3, there is no need to form the plating layer 4 thickly in advance.

Finally, as shown in FIG. 2(C), the resist 5 is peeled off in the same manner as in the embodiment described above, and the metal thin film 3 is removed from unnecessary parts.
expose. Then, in this state, the exposed metal thin film 3 is removed by etching using the plating layer 4 as a mask.

That is, when etching the metal thin film 3, one part of the metal thin film 3 is removed in a short time using a high-speed etching solution, but at the same time, the plating layer 4 is also removed by the thickness of the metal thin film 3. Ru. However, since the plating layer 4 is formed in advance to be as thick as the metal thin film 3, it is finally formed to have a thickness of approximately several gm to several + gm as described above. As a result, plating layer 4 and gold 1i! Q1g! A wiring pattern 7 having a two-layer structure consisting of three layers is formed on the front and back surfaces of the insulating film l. As a result, the same insulating film l as in the first embodiment was obtained.
A double-sided wiring board is obtained in which the wiring pattern 7 is electrically connected to the front and back surfaces at the locations of the through holes 2.

Therefore, according to the manufacturing method of such a double-sided wiring board, as in the first embodiment, the through holes 2 are formed in the insulating film l.
A thin metal film 3 is formed on the front and back surfaces of the insulating film 1 and on the inner surface of the through hole 2. ! 13
A plating layer 4 is formed only in the wiring pattern formation area, and this plating layer 4 is used as a mask to form a thin metal layer! By etching I3, the two-layer wiring pattern 7 consisting of the plating layer 4 and the metal B film 3 is made conductive at the through hole 2, so that the same effect as in the first embodiment described above is obtained. In addition, the process of etching the plating layer 4 is no longer necessary, and only the metal thin film 3 needs to be etched, making it possible to further integrate the manufacturing process and manufacturing double-sided wiring boards extremely efficiently. I can do it. In particular, when forming the plating layer 4, the resist 5 is formed outside the wiring pattern forming area, and the plating layer 4 is formed using this resist 5 as a mask, so the plating layer 4 is not formed on the surface of the resist 5. The plating layer 4 can be formed only on the surface of the metal thin film 3 in the wiring pattern forming area on the surface of the metal thin film 3. Therefore, the plating solution is not wasted and plating can be performed efficiently.

Note that the present invention is not limited to the embodiments described above, and can be modified in various ways. For example, the metal thin film 3 and the metal layer 4 may be etched by immersion in an etching solution, or by dry etching. Alternatively, if solder, gold (Au), or the like is used as the metal material of the plating layer 4, it will not easily corrode.

Further, the metal thin film 3 does not necessarily have to have a single layer structure, but may have a multilayer structure, and the through holes 2 are provided not only in one place but in multiple places to improve the reliability of the connection. Alternatively, the insulating film 1 may be surface-treated or coated with a suitable coating material, or may be laminated with a plurality of sheets.

Furthermore, the double-sided wiring board referred to in the present invention is not limited to the above-mentioned one, and includes, for example, a wiring board on which only a wiring pattern is formed to connect one board to another, or a board to an electronic component, or one electronic component to another, a so-called connector. It also includes what is called.

[Effects of the Invention] As explained in detail above, according to the method for manufacturing a double-sided wiring board according to the present invention, a through hole is first formed in an insulating film, and then the insulating film including the inner surface of the through hole is formed. By sequentially laminating a metal thin film and a plating layer on the surface of the plated layer and etching the two
Since the layered wiring pattern is made conductive at the through holes, not only does the conventional process of laminating metal foil on the front and back sides of the insulating film become unnecessary, but the metal foil can also be etched to form the wiring. The process of forming a pattern is also unnecessary. This makes it possible to simplify the manufacturing process, improve productivity, and reduce manufacturing costs. In this case, after the through holes are formed in the insulating film, a metal thin film is formed by vapor deposition or spar phthaling on the front and back surfaces of the insulating film and on the inner surfaces of the through holes. A metal thin film can also be easily formed on the inner surface of the first through hole. And this money! Since the thin film serves as the base plating for the plating layer, the plating layer can be easily and favorably formed on the surface of the metal thin film in a subsequent process. This results in
The metal thin film and plating layer formed on the inner surface of the through hole can ensure electrical continuity between the front and back wiring patterns.

[Brief explanation of drawings]

Fig. 1 shows a first embodiment of the present invention, Fig. 1 (A) is a sectional view of the main part of an insulating film, and Fig. 1 (B) shows a state in which through-holes are formed in the insulating film! Figure 1 (C) is a cross-sectional view of the main part of the island, with gold IiA thin film formed on the front and back surfaces of the insulating film and the inner surface of the through hole, and Figure 1 (D) is a cross-sectional view of the main part of the island with gold IiA thin film formed on the front and back surfaces of the insulating film and the inner surface of the through hole. Figure 1 (E) is a cross-sectional view of the main part with a plating layer formed on the surface, and (E) is a cross-sectional view of the main part with a resist formed on the wiring pattern forming area of the plating layer.
Figure (F) is a sectional view of the main part after etching the plated layer and metal thin film using the resist as a mask, and Figure 1 (G).
2 is a cross-sectional view of a main part of a double-sided wiring board obtained by removing the resist, FIG. 2 shows a manufacturing method according to a second embodiment of the present invention, and FIG. Figure 2 (B) is a cross-sectional view of the main part of the formed state, Figure 2 (B) is a cross-sectional view of the main part of the state where a plating layer is formed on the metal thin film in the wiring pattern formation area using the resist as a mask, and Figure 2 (C) is the resist removed. FIG. 1... Insulating film, 2... Through hole, 3... Metal thin film, 4... Plating layer,
5...Resist, 7...Wiring pattern. Patent applicant Casio Computer Co., Ltd. Same as above Toyo Metallizing Co., Ltd.
- (A u ε) te Z n 2 z de Σ] Otsu-1 glaze fi property i + 几mu (B) 7 pieces/l] 1 Figure 1 Figure 2

Claims (3)

[Claims] (1) A step of forming a through hole penetrating the insulating film from the front surface to the back surface by machining such as a drill or press, and forming a metal thin film by vapor deposition or sputtering on the front and back surfaces of the insulating film and the inner surface of the through hole. forming a plating layer on the entire surface of the metal thin film at least in a wiring pattern forming area corresponding to the through hole; and etching the metal thin film to remove unnecessary portions. A method for manufacturing a double-sided wiring board, comprising the steps of: forming a wiring pattern on the front and back surfaces of the insulating film that is electrically connected to each other at the through hole. (2) In claim 1, the step of forming a plating layer on the entire surface of the metal thin film at least in a wiring pattern forming area corresponding to the through hole includes the steps of: a step of forming a plating layer on the entire surface of the metal thin film formed on the inner surface of the through hole; a step of patterning a resist in a wiring pattern forming area corresponding to the through hole in the plating calendar; A method for manufacturing a double-sided wiring board, comprising: etching and removing the plating layer using the resist as a mask. (3) In claim 1, the step of forming a plating layer on the entire surface of the metal thin film at least in a wiring pattern forming area corresponding to the through hole includes the steps of: forming a resist pattern on the metal thin film formed on the inner surface of the through-hole other than the wiring pattern forming area; forming a plating layer only on the metal thin film in the wiring pattern forming area using the resist as a mask; A method for manufacturing a double-sided wiring board, comprising: a step of removing resist formed in areas other than the wiring pattern forming area.