JPH0451587A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To increase the close contact property of a conductor circuit with an insulating layer and to enhance an electricityfeeding property by a method wherein an adhesion layer of titanium or the like, a conductive layer of copper or the like and a protective layer of nickel or the like are laminated sequentially on an aluminum nitride board and the conductor layer is formed and covered with the insulating layer. CONSTITUTION:An adhesion layer 4 by at least one kind of metal selected from titanium, chromium, silver and niobium is laminated on the surface of an aluminum nitride board 2; a conductive layer 5 by at least one kind of metal selected from copper, silver and aluminum is laminated on the adhesion layer 4; a protective layer 6 by at least one kind of metal selected from nickel, chrominum and niobium is laminated sequentially on the conductive layer 5. Thereby, a conductor circuit is formed. After that, an insulating layer 9 which is composed of a polyimide resin and with which at least one part of the conductor circuit is covered is formed on the surface of the aluminum nitride metal 2. By this constitution, the close contact property of the conductor circuit with the surface of the board is increased by the adhesion layer, an electricity-feeding property is ensured and the close contact property with the insulating layer is increased by the protective layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing a wiring board used for semiconductor packages, etc., and particularly relates to a method of manufacturing a wiring board using aluminum nitride and polyimide resin as insulating materials. .

[Prior Art] Conventionally, ceramics such as alumina have generally been used as materials for wiring boards constituting semiconductor packages such as pin grid arrays. Then, a conductor circuit is printed on the surface of such a ceramic green sheet using a paste containing conductive particles such as tungsten, and the sheets are laminated and fired together to create a multilayer wiring with many layers of conductor circuits. Manufactures circuit boards.

[Problem to be solved by the invention] However, for small-lot production boards such as wiring boards for hybrid ICs, it is possible to easily, quickly, and inexpensively produce a wide variety of boards without making major changes to existing manufacturing equipment. There was a desire for a manufacturing method that would allow for mass production. In order to meet this demand, the present inventors formed a conductive circuit on an aluminum nitride substrate to which external extraction pins had been brazed in advance, formed an insulating layer of polyimide resin on it, and then We are working on the development of a build-up method for manufacturing multilayer wiring boards that forms conductor circuits and insulating layers.

However, in the conductor circuit formed by the conventional method as described above, the adhesion of aluminum nitride and polyimide resin to both paper edge materials is insufficient (in particular, there is a problem that the conductor circuit peels off between the polyimide resin and the paper). Moreover, the conductor circuit itself could not necessarily be said to have sufficient electrical conductivity.

The present invention was made in view of the above circumstances, and its object is to use aluminum nitride and polyimide resin as insulating materials, and to have a conductor circuit that has excellent adhesion to these insulating materials and has excellent electrical conductivity. An object of the present invention is to provide a method for manufacturing a wiring board.

[Means and effects for solving the problems] In order to solve the above problems, the present invention provides the following features:
an adhesion layer made of at least one metal selected from titanium, chromium, silver, and niobium; a conductive layer made of at least one metal selected from copper, silver, and aluminum on the adhesion layer; and a conductive layer made of at least one metal selected from copper, silver, and aluminum. On the layer, nickel,
After a conductor circuit is formed by sequentially laminating a protective layer made of at least one metal selected from chromium and niobium, a conductor circuit made of polyimide resin and a protective layer of at least one metal selected from chromium and niobium are formed on the surface of the aluminum nitride substrate. An insulating layer is formed to partially cover the surface.

According to this configuration, the adhesion of the conductive circuit formed on the aluminum nitride substrate to the surface of the aluminum nitride substrate can be improved by the adhesion layer. Furthermore, the conductive layer ensures conductivity as a conductor circuit. Furthermore, the protective layer enhances the adhesion between the conductive circuit and the insulating layer covering at least a portion thereof, thereby preventing the insulating layer from peeling off from the surface of the conductive circuit.

Examples of the metal of the adhesion layer include titanium (Ti), chromium (Cr), silver (Ag), and niobium (Nb), which are metals that thermodynamically have a high affinity with aluminum nitride, It is a metal that easily forms a solid solution with aluminum nitride under high temperature conditions.

The metal of the conductive layer includes copper (Cu) and silver (Ag).
, aluminum (AI), which are metals with extremely excellent electrical conductivity and excellent adhesion to the pre-adhesion layer.

Examples of metals for the protective layer include nickel (Ni), niobium (Nb), and chromium (Cr), which are metals that have excellent adhesion to the conductive layer and also have good adhesion to the polyimide resin. It is also an excellent metal.

Examples of means for forming each of the layers include sputtering, chemical vapor deposition, ion blasting, and plating, and any of these methods can be applied.

Note that aluminum nitride generally has excellent electrical insulation, thermal conductivity, heat resistance, dimensional stability, and mechanical strength, and has excellent suitability as a substrate material.

Incidentally, the thickness of the adhesive layer is preferably in the range of 0.05 to 2.0 μm.

If the film thickness is less than 0.05 μm, a continuous adhesion layer cannot be formed over the entire substrate surface due to the influence of fine irregularities on the aluminum nitride substrate surface, and the adhesion strength with the conductive layer decreases. - On the other hand, if it exceeds 2.0 μm,
This is not preferable because the residual stress in the adhesive layer becomes large and cracks are likely to occur.

The thickness of the conductive layer is preferably in the range of 1.0 to 10.0 μm.

If the film thickness is less than 1.0 μm, the electrical resistance becomes large and good electrical conductivity cannot be ensured. On the other hand, 10
．． If it exceeds 0 .mu.m, it becomes difficult to remove by etching or the like, which will be described later, and this will hinder the formation of a circuit pattern.

The thickness of the protective layer is 0.05 to 1. A range of 0 μm is preferable.

If the film thickness is less than 0.05 μm, a continuous protective layer cannot be formed on the conductive layer, and the electrical insulation properties and adhesion strength with the insulating layer decrease. On the other hand, if it exceeds 1.0 μm, residual stress in the protective layer becomes large and cracks are likely to occur, which is not preferable.

Generally, after the three-layer thin film is formed on an aluminum nitride substrate, a mask is formed using photoresist or the like, and etching is performed to form a desired circuit pattern on the substrate. Alternatively, a conductor circuit in a desired pattern can be formed by forming a mask in advance on the surface of the aluminum nitride substrate to cover areas where no circuit will be formed, and forming the thin film on the exposed areas. You can.

Subsequently, on the surface of the aluminum nitride substrate on which the three-layer conductor circuit is formed, an insulating layer made of polyimide resin is formed to cover at least a portion of the conductor circuit,
This insulates at least a portion of the conductor circuit from the outside.

The insulating layer made of the polyimide resin is formed by applying a varnish made of a polyimide precursor to the surface of the substrate, and then
It is formed by heating at ~400°C to dehydrate and condense the polyimide precursor on the substrate.

Polyimide resins generally have excellent not only electrical insulation properties but also heat resistance, but their heat resistance limit is about 400°C.

Therefore, when processing a wiring board manufactured by this method into a pin grid array, etc., it is necessary to braze the pins with an external drawer to avoid decomposition of the resin due to the heat of the time <soa℃ or higher). Preferably, the insulating layer is formed on an aluminum nitride substrate to which pins have been brazed in advance.

Thereafter, a conductor circuit and an insulating layer are sequentially formed on the polyimide resin insulating layer (thereby, a multilayer wiring board made of polyimide resin with the aluminum nitride substrate as the bottom layer base material can be manufactured). .

Examples and comparative examples embodying the present invention will be described below.

[Example] As shown in FIG. 1, this substrate 2 is placed on the top surface of an aluminum nitride substrate 2 having a through hole 3 filled with a conductor and to which an external lead pin 1 is pre-brazed.
After being heated to 0° C., reverse sputtering was performed for 10 minutes at the output of IKW, and then sputtering was performed using titanium as a target. Then, a titanium layer 4 (film thickness 0.1 μm) is formed as an adhesion layer on the upper surface of the aluminum nitride substrate 2.
m) was formed.

Similarly, sputtering is performed sequentially using copper and chromium as targets, thereby depositing a copper layer 5 (thickness 3.0 μm) as a conductive layer and a chromium layer 6 (thickness 0 μm) as a protective layer on the titanium layer 4. 5 μm) to form a three-layered thin film 7.

Subsequently, the aluminum nitride substrate l on which the thin film 7 was formed
A negative photoresist was uniformly applied to the surface of the substrate, and the circuit forming portion was irradiated with ultraviolet rays to photocure the portion.

This substrate 1 was immersed in an alkaline solution to dissolve and remove the uncured photoresist, thereby exposing a portion of the thin film 7. Then, the surface of the substrate l is etched using a mixed solution of hydrofluoric acid (HF) and nitric acid (HNO3),
The exposed portion of the thin film 7 was removed. Thereafter, the hardened photoresist was treated with an organic solvent and removed, thereby exposing the thin film 7 on the surface of the substrate 1 and forming a conductive circuit 8 in a desired pattern.

Next, after applying a varnish of polyimide precursor (part name: Photonice UR3140 manufactured by Toshi Co., Ltd.) to the surface of the substrate, heating at 300 to 400 ° C.
An insulating layer 9 made of polyimide resin was formed so that a portion of the conductor circuit 8 was exposed.

In the wiring board thus obtained, the conductive circuit 8 was tightly adhered to the aluminum nitride substrate 2 and the polyimide insulating layer 9. Also, the sheet resistance of the conductor circuit is 10
It showed a low value of mΩ.

[Comparative Example] By applying a tungsten paste having the following formulation on the upper surface of the aluminum nitride substrate 2, which is the same as that of the above embodiment, a conductor circuit having the same pattern shape as that of the above embodiment (with a film thickness of l
0 μm) was formed.

Tungsten paste formulation Tungsten particles 100.0 parts by weight α-terpineol 4.8 parts by weight Ethyl cellulose 0
．． 6 parts by weight Castor oil 0.4 parts by weight On this aluminum nitride substrate 2, an insulating layer 9 made of polyimide resin was formed in the same manner as in the previous example.

In the wiring board thus obtained, peeling occurred between the conductor circuit and the polyimide insulating layer, and the portions of the conductor circuit that required insulation could not be covered. Further, the sheet resistance of the conductor circuit showed a high value of 20 mΩ.

[Effects of the Invention] As detailed above, according to the present invention, aluminum nitride and polyimide resin are used as insulating materials, and
An excellent effect is achieved in that a wiring board having a conductive circuit that has excellent adhesion to these insulating materials and excellent current conductivity can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a wiring board in an embodiment of the present invention. 2... Aluminum nitride substrate, 4... Titanium layer as an adhesion layer, 5... Copper layer as a conductive layer, 6... Chromium layer as a protective layer, 8... Conductor circuit, 9. ...Insulating layer. Patent applicant IBIDEN Co., Ltd.

Claims (1)

[Claims] 1. On the surface of the aluminum nitride substrate (2), an adhesive layer (4) made of at least one metal selected from titanium, chromium, silver, and niobium, and on the adhesive layer (4). ,
A conductive layer (5) made of at least one metal selected from copper, silver, and aluminum, and a protective layer made of at least one metal selected from nickel, chromium, and niobium on the conductive layer (5). (
After forming a conductor circuit (8) by sequentially laminating 6) and 6), the surface of the aluminum nitride substrate (2) is made of polyimide resin and at least a part of the conductor circuit (8) is coated. A method for manufacturing a wiring board, comprising forming an insulating layer (9). 2. The thickness of the adhesion layer (4) is 0.05 to 2.0 μm, and the thickness of the conductive layer (5) is 1.0 to 10.0 μm.
and the thickness of the protective layer (6) is 0.05 to 1.0μ
2. The method of manufacturing a wiring board according to claim 1, wherein m.