JP2010180095A - Metallizing process for substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallizing process for a substrate by which not only particularly excellent electrical properties can be obtained, but also cost reduction can be achieved by being applied to a general alumina substrate. <P>SOLUTION: A hole-making step, a titanium layer-copper layer forming step, a chemical copper plating step, a dry film forming step, a patterning step, a copper circuit forming step, a peeling step, a nickel plating step, a gold plating step and a titanium layer-copper layer removing step are successively performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a metallization process for a substrate (metal for the substrate) that has high frequency and high density characteristics in the thin film process and does not increase the cost, particularly in the metallization process for direct copper plating (DPC) on the substrate. Method).

  As radio equipment such as cellular systems, wireless runs, and wireless modems have advanced, the requirements for circuit boards have become stricter. For example, characteristics such as high output, high frequency, and low loss have become indispensable conditions. ing. Conventional substrate manufacturing techniques can easily achieve these conditions.

However, the above conventional substrate manufacturing technique has the following problems.
The conventional thin film process is to form a circuit by a technique such as vacuum deposition or sputtering using a special metal net in a vacuum atmosphere, and it is mentioned as an advantage that the circuit can be formed smoothly. It has been regarded as a problem that it contains impurities such as oxides or nitrides.
In order to obtain a smoothly formed circuit and ideal electrical characteristics, a substrate having a high alumina purity (99.6%) must be used, which increases manufacturing costs.
In addition, since the paint used for forming the circuit is a granular material containing impurities, the portion where the circuit is thin contains a large amount of impurities, so that the electric conduction efficiency is high. It became worse and the heat dissipation rate was not excellent.

  In addition, when a circuit is formed by another low-cost thick film process, the circuit is not accurate and cannot meet the requirements of a high-frequency circuit. Further, the optimum line width and line spacing are Since both can be formed only at 6 mils or more, they could not be applied to high frequency circuits that require miniaturization. That is, in the thick film process, the conditions required by the high frequency circuit could not be satisfied.

  Further, on the surface of the conventional substrate, through holes having different diameters are scattered before performing the copper plating process. These through holes cause an adverse effect on the electric conduction effect on the surface of the substrate during sputtering, and vent holes or bubbles due to the through holes also cause a bad influence on circuit formation.

The present invention has been made in view of the above points, and provides a metallization process for a substrate having a circuit having ideal electrical characteristics at low cost, and the substrate without a metal net by the metallization process. Sputtering directly onto the surface of the substrate, removing vents or bubbles by sputtering through a chemical copper plating step, and forming a thick and high purity metal circuit through low cost exposure, development and plating steps, Excellent electrical properties can be obtained.
Furthermore, since it can be applied to a general aluminum oxide substrate, the cost can be reduced.

The invention of claim 1 of the present application includes a drilling step of drilling a through hole (100) in the ceramic substrate (10) as a process for electrical connection to the ceramic substrate (10),
A titanium layer and a copper layer forming step of sequentially forming a titanium layer (11) and a copper layer (12) on the ceramic substrate (10);
A chemical copper plating step for allowing electrical conduction of the air holes or bubbles having no electrical conduction effect formed in the titanium layer / copper layer formation step;
A dry film forming step for applying the dry film (13);
A patterning step of exposing and developing a pattern on the surface of the ceramic substrate (10) through a mask (14);
Forming a copper circuit (15) by copper plating the circuit pattern formed on the ceramic substrate (10);
A peeling step for peeling the dry film (13) remaining on the surface of the ceramic substrate (10);
A nickel plating step for forming a nickel layer (16) for preventing electromigration on the copper circuit (15);
A gold plating step of forming a gold layer (17) on the nickel layer (16) of the copper circuit (15);
A titanium layer / copper layer removing step for removing the titanium layer (11) / copper layer (12);
A metallization step of the substrate, characterized in that the steps are sequentially performed.

  In the metallization step of the substrate according to the present invention, the circuit is formed by exposure, development and etching, so that the circuit can be formed smoothly and in a thin linear shape.

  Further, since the circuit can be formed directly by plating, and has ideal electrical conduction characteristics and heat dissipation effect by the copper circuit itself, it has advantages such as excellent high frequency characteristics, low loss, low cost and physical stability.

  The nickel plating step may be performed immediately after the copper circuit forming step.

FIG. 1 is a flowchart of a substrate metallization process according to the present invention. It is a flowchart of the metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention. It is side surface sectional drawing which shows each metallization process of the board | substrate which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a flowchart of a substrate metallization process according to the present invention, and FIGS. 2A to 2G are side cross-sectional views showing each metallization process of a substrate according to the present invention.

  As shown in FIG. 1, the metallization process of the substrate according to the present invention includes a drilling step of drilling a through hole (100) in a ceramic substrate (10), and a titanium layer (11) sequentially on the ceramic substrate (10).・ Copper layer (12) forming titanium layer / copper layer forming step, and chemical copper that enables electric conduction of air holes or bubbles formed in the titanium layer / copper layer forming step and having no electric conduction effect A plating step, a dry film forming step to which a dry film (13) is attached, a patterning step for exposing and developing a pattern on the surface of the ceramic substrate (10) through a mask, and a ceramic substrate (10). A copper circuit forming step of applying copper plating to the circuit pattern to form a copper circuit (15), and a dry residue remaining on the surface of the ceramic substrate (10). A peeling step for peeling the film (13), a nickel plating step for forming a nickel layer (16) for preventing electromigration on the copper circuit (15), and a nickel layer (16 ) Having a gold plating step for forming a gold layer (17) and a titanium layer / copper layer removing step for removing the titanium layer (11) / copper layer (12).

  FIG. 2A shows a state in which a plurality of through holes (100) are formed in the ceramic substrate (10) by the drilling step as described above.

FIG. 2B shows that a titanium layer (11) and a copper layer (12) formed by sputtering are sequentially formed on the surface of the ceramic substrate (10) by the titanium layer / copper layer forming step, and the bottom surface of the ceramic substrate (10). The titanium layer (11) and the copper layer (12) are sequentially formed.
In this embodiment, the thickness of the titanium layer (11) is 3000 mm, and the thickness of the copper layer (12) is 4000 mm.
Thus, by sequentially forming the titanium layer (11) and the copper layer (12) on the ceramic substrate (10), it becomes easy to plate the copper circuit on the ceramic substrate (10).

However, innumerable ventilation holes or bubbles due to the titanium layer / copper layer forming step may affect the electrical connection of the ceramic substrate (10) and may cause incomplete electrical conduction. ) Is formed with a diameter of 100 μm or less, it becomes difficult to form a conductive layer by sputtering on the inner peripheral wall.
Therefore, in order to avoid an adverse effect on the electrical connection of the ceramic substrate (10), chemical copper (120) is further plated in the chemical copper plating step performed after the titanium layer / copper layer forming step.
Thereby, since a copper layer can be provided also in a small diameter through-hole (100), the electrical conduction effect of a ceramic substrate (10) can be improved.

  As shown in FIG. 2C, in the dry film forming step, a dry film (13) is attached to the surface of the ceramic substrate (10) where the circuit is formed, and the dry film (13) is a polymerization that reacts to ultraviolet rays. Resin that protects the circuit from being etched.

  In the patterning step, as described above, an exposure step and a development step are performed.

As shown in FIG. 2D, in the exposure step, a positive mask (14) manufactured according to a circuit pattern is first positioned, and then further adhered to a ceramic substrate (10) to which a dry film (13) is adhered. Thereafter, the ceramic substrate (10) is evacuated, pressed, and irradiated with ultraviolet rays by an exposure apparatus.
In addition, although this ultraviolet irradiation can superpose | polymerize a dry film (13), it does not reach to the part covered with the circuit pattern formed in the mask (14).

  Further, the role of development in the development step is to remove the dry film (13) that has not been polymerized by the developer. That is, a necessary part of the circuit is left by physical or chemical peeling, and the circuit configured can be smoothly and thinly formed by the above steps.

As shown in FIG. 2E, in the copper circuit formation step, a copper circuit (15) having a predetermined thickness is formed by performing copper plating on a circuit pattern formed on the ceramic substrate (10).
In this step, since the copper circuit is directly formed by plating, ideal electrical conduction characteristics and heat dissipation effects can be obtained.

  As shown in FIG. 2F, in the peeling step, as described above, the dry film (13) remaining on the surface of the ceramic substrate (10) is removed.

  In the titanium layer / copper layer removing step, a photoresist is first applied to the copper circuit (15) of the ceramic substrate (10), and then titanium other than the copper circuit (15) on the surface of the ceramic substrate (10) is etched. The layer (11) and the copper layer (12) are removed.

  As shown in FIG. 2G, in the nickel plating step, a nickel layer (16) is plated on the surface of the copper circuit (15) in the ceramic substrate (10), and the nickel layer (16) ) In order to prevent electromigration of the copper ions to the gold layer (17) formed thereafter.

  In the gold plating step, a gold layer (17) is formed on the copper circuit (15) so that the circuit has conditions applicable to high frequencies.

Each of the steps is a specific flow of the metallization process according to the present invention, but the order of the steps is not limited thereto.
For example, as described above, the nickel plating step and the gold plating step can be performed after the titanium layer / copper layer removing step, or can be performed immediately after the chemical copper plating step.
That is, after the copper circuit (15) is plated on the surface of the ceramic substrate (10), the nickel circuit (16) for preventing electromigration of copper ions on the copper circuit (15) is immediately improved, and the signal transmission is improved. Then, a gold layer (17) to be formed may be formed, and subsequently, a peeling step and a titanium layer / copper layer removing step may be performed, and the same effect as the above-described step can be exhibited.

  According to the above description, the metallization process according to the present invention has at least the following advantages.

1. The circuit can be formed smoothly and in a straight line shape. This is a basic condition of a high-frequency circuit, that is, the circuit structure by the steps such as exposure, development and etching is very fine, and is suitable for high-density arrangement and formed. Since the circuit is excellent in accuracy, it is optimal for use as a high-frequency circuit.

2. It has high heat conduction efficiency and electrical characteristics. In the present invention, since the copper circuit is directly formed to a suitable thickness by plating, the copper circuit has an ideal heat dissipation effect, and features such as excellent electric conduction efficiency, stable physical properties and low loss. Also have.

3. low cost. Since the present invention has ideal electrical characteristics because the copper circuit is formed to a suitable thickness by plating, a substrate having a low alumina purity (about 96%) can be used. Cost can be effectively reduced.

  Since the present invention has the above-described configuration, it can be manufactured more easily and efficiently than the conventional high-frequency circuit board manufacturing process, and the cost can be reduced.

DESCRIPTION OF SYMBOLS 10 Ceramic substrate 100 Through-hole 11 Titanium layer 12 Copper layer 120 Chemical copper 13 Dry film 14 Mask 15 Copper circuit 16 Nickel layer 17 Gold layer

Claims (1)

A through hole drilling step for drilling a through hole in the ceramic substrate;
A titanium layer and a copper layer forming step for sequentially forming a titanium layer and a copper layer on a ceramic substrate by a sputtering method;
Furthermore, by performing chemical copper plating, a chemical copper plating step for removing electrical conduction inhibition due to the air holes or bubbles formed in the titanium layer / copper layer forming step,
A dry film forming step for applying the dry film;
A patterning step for forming a circuit pattern by exposing and developing the surface of the ceramic substrate through a mask; and
A copper circuit forming step of forming a copper circuit by performing copper plating on a circuit pattern formed on the ceramic substrate;
A peeling step for peeling the dry film remaining on the surface of the ceramic substrate;
A nickel plating step for forming a nickel plating layer for preventing electromigration on the surface of the copper circuit;
A gold plating step of forming a gold plating layer on the nickel plating layer formed on the surface of the copper circuit;
A titanium layer / copper layer removing step for removing the titanium layer / copper layer;
The metallization process of the board | substrate characterized by performing sequentially.

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