JPH0691310B2 - Wiring board manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a ceramic multilayer wiring board used for electronic equipment such as a large computer.

[Conventional technology]

In this type of conventional ceramic multilayer wiring board, gold is used as a conductor wiring in a multilayer wiring layer formed thereon, which has the characteristic that it does not oxidize when an insulating layer is formed and has a low electric resistance. Copper is either used to further reduce resistance.

FIG. 3 is a sectional view showing an example of a wiring board manufactured by a conventional manufacturing method in the order of steps.

As shown in FIG. 3 (a), the conductor wiring in which the copper layer 21 is formed on the insulating layer 23 of the ceramic multilayer substrate and the nickel layer 22 is formed thereon, the gold layer 25 is formed on the uppermost layer. ing. In order to connect the chip 30 (see FIG. 3 (d)) to this, an insulating layer 29 is formed between the conductor wires as shown in FIG. 3 (b), and between the insulating layers 29 on the upper part of the conductor wires. The solder 28 is injected into the formed via hole 24 (see FIG. 3C), and the terminals of the chip 30 are connected to the solder 28. As a material for the insulating layer 29, a photosensitive polyimide having an ionically-bonded photosensitive group introduced therein is commonly used.
The photosensitive polyimide introduced with an ionic bonding photosensitive group,
This is because the photosensitive group is easily decomposed in the heat treatment process. If the photosensitive group remains, the mechanical strength of the insulating layer will decrease. With materials other than photosensitive polyimide having an ionic bonding photosensitive group introduced therein, the photosensitive group is difficult to decompose and the photosensitive group is likely to remain after the heat treatment step.

[Problems to be solved by the invention]

As described above, gold or copper is used for the conductor wiring in the multilayer wiring layer formed on the conventional ceramic multilayer wiring board, but copper is cheaper and has lower electric resistance. Although it is desirable, copper has a drawback that it is easily oxidized, and when a photosensitive insulating resin having an ionic bonding photosensitive group is used, it is easy to form a complex with copper, which results in thin chromium on the copper wiring. It is necessary to provide this layer to improve this, but this has a drawback that the resistance of the via portion becomes high. In addition, when a copper terminal is formed on the uppermost layer of the board for component mounting and a solder dam is formed on it with an insulating layer made of the above-mentioned photosensitive material to reflow solder, the solder coatability is poor. There is also a drawback. Gold, on the other hand, has the drawback of being expensive and thus increasing the cost of the wiring board.

[Means for solving problems]

In the method for manufacturing a wiring board of the present invention, when a conductor wiring is formed, a copper layer having a low electric resistance and a thin metal film for preventing the oxidation of copper are formed on the surface of the copper layer to form an insulating layer. At this time, a via hole is formed to ensure mutual conduction between the conductor wirings of each layer, and the thin metal film of the conductor wiring appearing in the via hole is wet-etched with an acid or alkali or dried by ion beam or the like. The next layer is formed after the copper surface is exposed by removing it by an etching method or the like. That is, the method for manufacturing a wiring board of the present invention comprises forming a copper layer on an insulating layer of the wiring board, forming a metal thin film layer on the copper layer to form a conductor wiring, and forming an ion between the conductor wirings. An insulating layer made of a photosensitive material having a bonding photosensitive group introduced is formed, and the metal thin film layer of the conductor wiring exposed in the openings between the insulating layers is removed by an etching method to expose the copper layer. It is configured to include that.

〔Example〕

 Next, examples of the present invention will be described.

FIG. 1 is a sectional view showing an example of a wiring board manufactured according to the first embodiment of the present invention in the order of steps. Fig. 1 (a)
In Fig. 1 (b), between the conductor wiring 7 formed by forming the copper layer 1 on the insulating layer 3 of the ceramic multilayer plate and forming the nickel layer 2 on the copper layer 1 as shown in Fig. 1 (b). Then, the via hole 4 is formed by being covered with an insulating layer 9 made of a photosensitive polyimide into which an ionic bonding photosensitive group is introduced. Next, as shown in FIG. 1 (c), the thin nickel layer 2 on the conductor wiring 7 is etched with an acid or an alkali, and then a dry etching such as an ion beam is performed to expose the copper layer 1. As shown in FIG. 1D, a copper layer 5 and a nickel layer 8 are formed on the copper layer 1 to form an upper conductor wiring 8. The nickel layer 6 is provided to prevent oxidation of the copper layer 5. The chip is connected to the upper conductor wiring 8. At this time, part of the nickel layer 6 is removed according to the process of the second embodiment described later. Solder is supplied to the portion where the nickel layer 6 is removed. A chip is mounted on this solder.

FIG. 2 is a sectional view showing an example of a wiring board manufactured according to the second embodiment of the present invention in the order of steps.

In this embodiment, the conductor wiring is directly used as a terminal for connecting an electronic component (chip) or the like. That is, as shown in FIG. 2A, the copper layer 11 is formed on the insulating layer 13, and the nickel layer 12 is formed on the copper layer 11 to form the conductor wiring 17. Next, as shown in FIG. 2 (b), the conductor wiring 17
An insulating layer 19 made of a photosensitive material into which an ionic bonding photosensitive group is introduced is formed between the spaces, and an opening (via hole) 14 is formed above the conductor wiring 17. Next, as shown in FIG. 2 (c), the thin nickel layer 12 on the conductor wiring 17 is removed by dry etching with an ion beam or the like, and then solder 18 is formed thereon as shown in FIG. 2 (d). Then, as shown in FIG. 2 (e), the terminals of the chip 30 are mounted on the solder 18 and connected.

In each of the above-described embodiments, nickel is used as the thin metal film, but chromium, palladium, titanium, or aluminum can be used instead of nickel.

〔The invention's effect〕

As described above, the wiring board manufacturing method of the present invention is
The conductor wiring mainly composed of copper and a photosensitive insulating material having an ionic bonding photosensitive group introduced therein can be used in combination, and at the time, the copper surface can be prevented from being oxidized and formed in the upper layer. However, there is an effect that it is possible to form the conductor wiring on which the solder easily sticks after forming the solder dam with the insulating material.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a wiring board manufactured according to the first embodiment of the present invention in the order of steps, and FIG. 2 is a sectional view showing an example of a wiring board manufactured according to the second embodiment of the present invention in the order of steps. 3 and 4 are sectional views showing an example of a wiring board manufactured by a conventional manufacturing method in the order of steps. 1, 5, 11, 21 ... Copper layer, 2, 6, 12, 22, ... Nickel layer, 3, 9, 13, 19, 23, 29, ... Insulating layer, 4, 14, 24 ...
… Via hole, 7 ・ 17 …… conductor wiring, 8 …… upper layer conductor wiring, 18 ・ 28 …… solder, 25 …… gold layer, 30 …… chip.

Claims (1)

[Claims] 1. A conductor layer is formed by forming a copper layer on an insulating layer of a wiring board, and forming a metal thin film layer on the copper layer, and introducing an ion-bonding photosensitive group between the conductor wires. Forming an insulating layer of the photosensitive material, and removing the metal thin film layer of the conductor wiring exposed in the opening between the insulating layers by an etching method to expose the copper layer. Method of manufacturing wiring board.