WO2016194968A1 - Metal layer formation method - Google Patents

Abstract

The present invention relates to a method for forming a metal layer on a substrate, said method including non-continuously forming, on the substrate, metal areas formed from metal microparticles, and subsequently forming the metal layer on the non-continuous metal areas so as to connect said areas.

Description

Method for forming metal layer

The present invention relates to a method for forming a metal layer, particularly a wiring.

Ceramic materials and metal materials are widely used as constituent materials for electronic components, and metal materials are used particularly for electrodes, terminals, circuit wiring, and the like.

As a wiring formation technique, a technique of forming a wiring with nano ink using an inkjet technique is known (Patent Document 1). In this technique, metal nanoparticles protected with an appropriate stabilizer are mixed with a solvent to form a nano ink, which is drawn on a substrate by an ink jet technique, and subjected to heat treatment to fuse and bond the nanoparticles. This technology is classified as a direct metallization method that “accumulates a necessary amount of nanoparticles only at a necessary site”, and is expected to be developed as a low-cost and highly efficient process.

JP 2006-257403 A

In the direct metallization method using the inkjet technology, Au, Ag, or Cu is usually used as the metal material. However, Au is expensive, Ag is prone to migration, and Cu is susceptible to oxidation, and the above method has not yet been put into practical use. In addition, particularly in the case of forming a continuous wiring, there is a problem that a large amount of nanoparticles are required and the cost is increased, and the processing time is increased. Furthermore, although it is calculated | required that the electrical conductive part of an electronic component, especially wiring are low resistance, since components other than the metal nanoparticle contained in nano ink influence resistance value, the restrictions about the composition of nano ink become large.

Accordingly, an object of the present invention is to provide a method capable of solving the above-mentioned problems relating to cost, processing time, resistance value, and each metal while taking advantage of the direct metallization method using the ink jet technology. To do.

As a result of diligent investigations to solve the above problems, the present inventors are characterized by “accumulating a necessary amount of nanoparticles only at a necessary site”, which is a feature of the direct metallization method using the ink jet technology. Going one step further, the idea was to stop the accumulation of nanoparticles from thinning (discontinuous), and then form a continuous film (or continuous layer) collectively by plating or the like. That is, in the present invention, as shown in FIG. 3A, the nanoparticles 102 are not accumulated on the wiring formation region 100 without gaps, but as shown in FIG. Nanoparticles 102 are thinned out on 100 (discontinuously formed), and a metal layer is formed thereon to connect the nanoparticles 102 to each other. As a result, the amount of the necessary metal nanoparticles can be reduced, and the metal nanoparticles are covered with the metal layer thereon, so that migration and oxidation are suppressed. Note that the nanoparticle 102 in FIG. 3 does not mean one nanoparticle, but may be an aggregate of a certain number of nanoparticles.

According to a first aspect of the present invention, there is provided a method of forming a metal layer on a substrate,
On the substrate, a metal region formed from metal fine particles is formed discontinuously,
A method is then provided that includes forming a metal layer on the discontinuous metal regions to connect them.

According to the second aspect of the present invention, there is provided an electronic component manufacturing method including forming a metal layer by the above method.

According to the method of the present invention, since drawing with ink containing metal fine particles changes from a continuous body to a non-continuous body, the processing time can be shortened, and further, the amount of ink required can be reduced. Since such an ink is an expensive special ink, the cost can be greatly reduced by reducing the required amount.

Furthermore, since the metal region formed by the ink containing metal fine particles is covered by the metal layer formed thereon, migration and oxidation can be suppressed, and the ink containing silver and copper fine particles can be used without any problem. It becomes possible to do.

Furthermore, since high conductivity is ensured by the metal layer, the conductivity of the metal region formed by the ink is not a big problem, and the degree of freedom in the composition of the ink is improved.

FIGS. 1A to 1C are diagrams for schematically explaining the metal layer forming method of the present invention. FIG. 2A shows the arrangement of dot-like metal areas when there are four adjacent metal areas, and FIG. 2B shows the arrangement of dot-like metal areas when there are six adjacent metal areas. Show. FIG. 3A is an image diagram of metal fine particles arranged in the conventional method, and FIG. 3B is an image diagram of metal fine particles arranged in the present invention.

Hereinafter, the method of the present invention will be described with reference to the drawings, taking as an example the method of forming the wiring 4 on the substrate 2.

The method of the present invention comprises two steps, namely:
Step 1: a step of discontinuously forming a metal region formed from metal fine particles on a substrate;
Step 2: forming a metal layer on the discontinuous metal regions so as to connect them;
including.

Step 1: Step of discontinuously forming a metal region formed of metal fine particles on a substrate

First, the substrate 2 is prepared (FIG. 1A). A board | substrate is not specifically limited, Substrates, such as a ceramic, resin, glass, can be used according to a use. In one embodiment, the substrate is preferably ceramic.

Next, a metal region 6 is formed on the substrate using metal fine particles. The metal region 6 is formed discontinuously in a portion corresponding to the wiring 4 (FIG. 1B). By forming the metal region 6 discontinuously, the amount of necessary metal fine particles can be reduced.

The method for forming the metal region is not particularly limited, and examples thereof include inkjet printing and screen printing. However, fine drawing is possible, and pre-processing such as masking is not required, and inkjet processing has a short processing time. Is preferred. A technique for drawing a wiring or the like on a substrate by ink-jet printing is known, and is described in Patent Document 1, for example. Commercially available inkjet printers can be used for inkjet printing. For example, Konica Minolta EB100, XY100 (manufactured by Konica Minolta IJ Co., Ltd.), Dimatics Material Printer DMP-3000, Dimatics Examples thereof include a material printer DMP-2831 (manufactured by Fuji Film Co., Ltd.).

The conductive ink used for ink jet printing contains metal fine particles and a solvent, and other components such as a stabilizer as required. By printing the conductive ink on the substrate, a metal region is formed by the metal fine particles contained therein.

The metal constituting the metal fine particles is not particularly limited, but preferably gold, silver, copper, a combination thereof, or an alloy thereof can be used.

The average particle diameter of the metal fine particles is preferably 1 nm to 0.5 μm, more preferably 5 nm to 100 nm, still more preferably 5 nm to 50 nm, for example, 5 nm to 30 nm.

The concentration of the metal fine particles in the conductive ink is not particularly limited, and may be, for example, 1 wt% or more and 50 wt% or less, preferably 5 wt% or more and 30 wt% or less with respect to the entire conductive ink.

As the conductive ink, commercially available ink can be used, and examples thereof include AGK101 / AGK102 manufactured by Kishu Giken Co., Ltd., NBSIJ-MU01 manufactured by Mitsubishi Paper Industries, Ltd., and nano ink manufactured by Colloidal Ink.

In a preferred embodiment, after the conductive ink is printed on the substrate, a post-treatment such as heat treatment may be performed.

The size of the metal region 6 is not particularly limited, and for example, the equivalent area circle diameter is 0.5 μm or more, preferably 1 μm or more, more preferably 5 μm or more. By setting the area equivalent circle diameter to 0.5 μm or more, a metal layer having higher bonding strength can be obtained when subjected to subsequent plating treatment. The upper limit of the area equivalent circle diameter is not particularly limited, but is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less from the viewpoint of reducing the amount of conductive ink to be used. The area equivalent circle diameter can be measured using an SEM (scanning electron microscope).

The area ratio of the metal region to the region for forming the metal layer is not particularly limited, but is, for example, 10% to 90%, preferably 30% to 80%, and more preferably 40% to 60%. From the viewpoint of increasing the bonding strength between the metal region and the metal layer, it is preferably as large as possible. Further, from the viewpoint of reducing the amount of conductive ink to be used, it is preferably as small as possible.

The discontinuous metal region 6 may be formed at an arbitrary position and shape in a portion corresponding to the wiring 4, and may be formed in a dot shape, a broken line shape, or a barcode shape, for example.

In a preferred embodiment, the metal regions 6 are arranged in a dot shape. It is preferable that the metal area | region arrange | positioned at dot shape exists uniformly. As shown in FIG. 2, the number of adjacent metal regions 6 at the closest distance is not particularly limited. For example, 4 (FIG. 2A) or 6 (FIG. 2B) Preferably, 6 is more preferable. By arranging the dots uniformly in this manner, the metal regions 6 can be easily connected and the adhesion of the formed metal layer can be improved in the subsequent metal layer forming step.

When the metal regions are formed discontinuously, the distance between adjacent metal regions is not particularly limited, but is preferably 5 μm to 1 mm, more preferably 10 μm to 300 μm, and even more preferably 20 μm to 100 μm. Hereinafter, it is more preferably 20 μm or more and 50 μm or less, for example, 30 μm or 20 μm. By reducing the distance between adjacent metal regions, it is easy to form a metal layer (plating layer) by subsequent plating, and the bonding strength of the metal layer can be further increased. Further, by increasing the distance between adjacent metal regions, the amount of necessary conductive ink can be reduced.

Step 2: Forming a metal layer on the discontinuous metal region so as to connect them

Next, a metal layer is formed on the metal region 6 formed in step 1, and the metal region 6 is connected to form the wiring 4 (FIG. 1C).

The method for forming the metal layer is not particularly limited, but is preferably formed by plating. The plating process is advantageous in that it is easy to operate and does not apply a load to the substrate.

In step 1, since the metal region 6 is formed in the portion corresponding to the wiring 4, a plating reaction (which may be either electrolytic plating or electroless plating) occurs through this metal region, and the metal layer ( Wiring) is formed. Thus, by forming a metal layer (wiring) by plating, the adhesion between the substrate and the metal layer can be further enhanced.

The metal region 6 is formed discontinuously (for example, in a dot shape), but is connected by a metal layer formed by plating. Specifically, the plating layer is first formed on the metal region, but the plating deposits formed on the adjacent metal regions cross the metal region in the lateral direction (that is, the direction along the substrate surface). Can also grow and come into contact with each other to form a single metal layer. The lateral growth of the plating deposit can be achieved by adjusting the composition of the plating solution, the time of the plating treatment, and the like.

The plating treatment may be either an electrolytic plating treatment or an electroless plating treatment. Since the metal region is conductive, the electroplating process is possible, and if the metal forming the metal region has catalytic activity, the electroless plating process is possible. When the metal forming the metal region does not have catalytic activity, electroless plating can be performed by applying a palladium catalyst or the like having catalytic activity to the metal region.

Although it does not specifically limit as a metal which comprises a metal layer, For example, Ni, Cu, Ag, Sn, Au etc. are mentioned.

In one embodiment, the plating process may be performed in multiple stages.

When performing multi-stage plating as described above, the metal layer is composed of a plurality of layers. The plurality of layers may be made of the same metal or different metals.

For example, first, strike plating (base plating) treatment can be performed, and then main plating treatment can be performed. Moreover, you may perform this plating process in multiple times.

For example, the metal layer may be formed by performing strike plating, thereby connecting discontinuous metal regions, and then growing the plating in the thickness direction by main plating.

In one embodiment, the strike plating and the main plating may be copper plating. The strike plating bath for strike plating preferably comprises 10-30 g / L copper pyrophosphate, 80-250 g / L pyrophosphate and 5-20 g / L potassium oxalate, with a pH of 7.5-10. .0. As the strike plating conditions, preferably, the bath temperature may be 15 to 50 ° C., and the current density may be 0.05 to 0.30 A / dm ² . By using such a strike plating bath and conditions, lateral plating growth can be promoted, and the connection between discontinuous metal regions can be performed better. Next, the metal layer can be grown to a desired thickness by the main plating. This plating can be performed by a method well known to those skilled in the art, for example, using a commercially available copper plating solution.

In another aspect, the strike plating and the main plating may be nickel plating. The strike plating bath for strike plating preferably comprises 300 to 450 g / L nickel sulfate, 35 to 55 g / L boric acid and 0.5 to 2 g / L nickel chloride with a pH of 3.5 to 5 .0. As the strike plating conditions, preferably, the bath temperature may be 40 to 75 ° C., and the current density may be 0.05 to 0.30 A / dm ² . By using such a strike plating bath and conditions, the connection between the discontinuous metal regions can be performed better. Next, the metal layer can be grown to a desired thickness by the main plating. This plating can be performed by a method well known to those skilled in the art, for example, using a commercially available nickel plating solution. Furthermore, Sn or Au or the like, preferably Sn, may be plated on the nickel layer formed by the main plating. By forming such a further plating layer, solder processing or the like when connecting to another electronic component becomes easier.

In another embodiment, copper plating or nickel plating may be formed on the metal region by electroless plating. This electroless plating treatment is usually autocatalytic plating, and when the metal forming the metal region does not have catalytic activity, it is preferable to apply an appropriate catalyst (for example, Pd catalyst) to the place to be plated. The electroless copper plating treatment can be performed by appropriately selecting conditions using a commercially available electroless copper plating solution or electroless nickel plating solution. For example, when electroless copper plating is performed, it can be performed at a pH of 11 to 13 and a bath temperature of 30 to 50 ° C. using a commercially available electroless copper plating solution (for example, OPC Copper T manufactured by Okuno Pharmaceutical Co., Ltd.). When electroless nickel plating is performed, a commercially available electroless nickel plating solution (for example, IPC Nicolon GM manufactured by Okuno Pharmaceutical Co., Ltd.) is used at pH 3.5 to 5.0 and bath temperature 60 to 90 ° C. It can be carried out. Furthermore, after performing copper plating or nickel plating (preferably nickel plating), gold or tin (preferably gold plating) may be further plated. This gold or tin plating layer may be formed by electroless plating, for example, by autocatalytic plating or displacement plating.

In one aspect, the metal layer forming method of the present invention is used in the manufacture of electronic components, particularly in the manufacture of electrodes, wirings or terminals of electronic components.

Therefore, the present invention also provides a method for manufacturing an electronic component including forming a metal layer by the above-described method of the present invention.

Although the method of the present invention has been described above, the method of the present invention is not limited to the above embodiment, and various modifications can be made.

On the ceramic plate having a thickness of 2 mm, Ag nano-ink was printed in a dot shape as shown in FIG. 2B with an ejection amount of 42 pl using an inkjet device. The distance between dots was 30 μm. Subsequently, the baking process was performed at 250 degreeC and the wiring was formed. This was immersed in a Cu plating bath (copper pyrophosphate 20 g / L, pyrophosphate 180 g / L, potassium oxalate 10 g / L) and energized for 120 minutes at a current density of 0.15 A / dm ² . This formed the metal layer with Cu.

Since the method of the present invention enables a plating process on a ceramic, it can be suitably used in the production of electronic components, particularly for the formation of wirings, electrodes, terminals and the like.

2 ... Substrate 4 ... Wiring 6 ... Metal region 100 ... Wiring forming region 102 ... Nanoparticle

Claims (9)

1. A method of forming a metal layer on a substrate,
   On the substrate, a metal region formed from metal fine particles is formed discontinuously,
   Then forming a metal layer on the discontinuous metal regions to connect them together.
2. 2. The method according to claim 1, wherein the metal constituting the metal fine particles is gold, silver, copper, or a combination thereof.
3. The method according to claim 1 or 2, wherein the metal region formed from the metal fine particles is formed by an ink jet printing method using a conductive ink containing the metal fine particles.
4. The method according to any one of claims 1 to 3, wherein a distance between adjacent metal regions is 30 µm or less.
5. The method according to any one of claims 1 to 4, wherein the metal region is formed in a dot shape.
6. 6. The method according to claim 1, wherein the metal layer is formed on the metal region by plating.
7. 7. The method according to claim 1, wherein the metal layer is Ni, Cu, Ag, Sn, or Au.
8. The method according to any one of claims 1 to 7, wherein the metal layer is an electrode, a wiring, or a terminal.
9. A method for manufacturing an electronic component, comprising forming a metal layer by the method according to any one of claims 1 to 8.

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