JPH0983133A - Deposition method of plating layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase adhesion irrespective of conditions of an involved filler and without being influenced by the surface state of a polished surface by polishing the surface of a coating layer for plating, striking the polished surface with fine particles to elute the filler from a roughened surface, and plating the surface after rendered to the elution. SOLUTION: By polishing a coating layer 21 for plating a surface layer where the coating layer 21 for plating is cured is removed and a filler 21B is partly exposed. Thereafter, by striking the polished surface with fine particles the polished surface is uniformly roughened to form a roughened surface. For this, traces of mechanical polishing is reduced, and the filler 21B buried in the vicinity of the surface is exposed anew. Accordingly, in an eluting process of the filler 21B more surface holes 30 can be formed on the surface of the coated layer 21 for plating, and the surface can be made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for depositing a plating layer, and more particularly to a technique suitable for depositing a plating layer on a printed circuit board.

[0002]

2. Description of the Related Art Conventionally, a plating layer made of a conductive material such as gold or copper may be formed on the surface of a printed circuit board made of synthetic resin. This plated layer becomes a wiring circuit pattern by subjecting it to an etching treatment with a predetermined pattern later. In this case, the most serious problem is the adhesive force of the plating layer to the synthetic resin, and generally, the plating layer formed on the synthetic resin has a weak adhesive force and has a high risk of peeling. If the adhesive strength is weak, the plating layer is likely to be peeled off due to repeated temperature rises and falls, which deteriorates the durability of the products and often causes the products that cannot withstand durability tests such as cooling and heating cycles.

Therefore, as described in Japanese Patent Laid-Open No. 5-230276, there is a method of applying a reactive resin containing a filler on the surface of a synthetic resin. In this method, as shown in FIG. 4, a reactive resin 10A containing a filler 10B is applied and then cured by heating or light irradiation to form a coating layer 10 for plating, and thereafter, a surface 10a thereof is machined. A part of the filler 10B is exposed on the surface 10b by mechanically or chemically polishing.
At this time, part of the filler 10B is separated from the inside of the layer by polishing, and the surface hole 11 is formed. Next, the exposed filler 10B is eluted with an acid to form a large number of fine surface holes 12 on the surface 10c.

The surface 1 on which the surface holes 11 and 12 are formed
By performing electroless plating on 0c, the plating layer is also formed in the surface holes 11 and 12, and this serves as an anchor to enhance the adhesion of the plating layer, so that the plating layer having a strong adhesion is coated. You can wear it. Note that the filler usually has a complicated and irregular shape, but in the figure, the shape is abbreviated and expressed as a circle. The same applies to the other drawings described below.

[0005]

In the conventional method for depositing a plating layer, the conditions such as the content of filler, material and particle size in the reactive resin are set within a predetermined range in order to increase the adhesion of the plating layer. It must be adjusted within and process control is complicated to maintain these conditions. Further, it is necessary to increase the amount of the filler in order to increase the adhesiveness of the plating layer. However, if the amount of the filler is excessively increased, the kneading and coating work of the synthetic resin becomes difficult, and the plating coating layer 10 There is a problem that the device itself becomes fragile, pinholes are generated in the plating layer, and the surface condition of the plating layer is deteriorated.

Further, the surface 10b of the coating layer to be plated.
Depending on the surface state of the polishing surface formed on the, the elution state of the filler becomes non-uniform and the adhesive force may vary,
There is also a problem in terms of the quality of the plating layer that the flatness of the plating layer is hindered.

Therefore, the present invention is to solve the above-mentioned problems, and the problem thereof is that in the method of depositing a plating layer using the above-mentioned reactive resin containing a filler as a base, regardless of the conditions of the contained filler. Another object of the present invention is to obtain a deposition method that can always improve the adhesion of the plating layer without being affected by the surface state of the polishing surface and can obtain a high-quality plating layer.

[0008]

The method of depositing a plated layer according to the present invention comprises a composition coating step of coating an object to be plated with a composition to be plated, which is obtained by filling a resin having a reactive group with a filler. A curing step of polymerizing and curing the composition to be plated to form a coating layer to be plated, a polishing step of polishing the surface of the coating layer to be plated, and a polishing surface of the coating layer to be plated. A roughening treatment step of tapping with fine particles, an elution treatment step of eluting the filler from the roughened surface of the coating layer to be plated, and a plating treatment on the surface of the coating layer to be plated after the elution treatment It has a plating process.

In this case, it is preferable that the roughening treatment step is set so as to hit the fine particles with a strength such that the fine particles are not embedded inside the coating layer for plating.

Further, it is preferable that the particle size of the fine particles is larger than that of the filler.

According to the first aspect of the present invention, the hardened surface layer of the plated coating layer is removed and the filler is partially exposed by polishing the plated coating layer. After that, by hitting the polishing surface with fine particles, the surface of the polishing surface is uniformly roughened to form a rough surface, so that the traces of mechanical polishing are reduced and the filler embedded near the surface is removed. Newly exposed. Therefore, in the elution step of the filler, it is possible to form a larger number of surface holes formed on the surface of the coating layer to be plated and to make the surface condition uniform, so that the adhesion of the plating layer formed thereon can be improved. It is possible to improve the properties such as smoothness and homogeneity of the plating layer while improving the durability and durability.

When the plating layer and the lower conductor are connected to each other, the surface of the conductor is covered with a plating coating layer,
Even if unnecessary materials such as an insulating resist adhere, these adhered substances can be removed in the roughening treatment step. Further, in this step, since the surface of the conductor is hit by the fine particles, fine irregularities are formed on the surface, so that the adhesion with the plating layer is improved.

According to the second aspect, since the fine particles hit the fine particles with a strength such that they are not buried in the plated coating layer, the fine particles are embedded in the plated coating layer or on the surface of the plated coating layer. Since it does not adhere strongly, it is necessary to prevent deterioration of the plating quality such as a decrease in the adhesion of the plating layer, a decrease in durability, a decrease in smoothness, etc., due to the presence of fine particles between the particles and the plating layer. You can

According to the third aspect, by making the particle size of the fine particles larger than that of the filler, it is not necessary to deeply or strongly drive the fine particles to expose the filler. It is not embedded in the layer or strongly adhered to the surface, and it is possible to prevent deterioration of the quality of the plating layer due to the residual fine particles.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method of depositing a plating layer according to the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing a method of depositing a plating layer of this embodiment. As shown in FIG. 1A, a synthetic resin containing a filler is selectively placed on the surface 20a of a substrate 20 such as a printed circuit board by screen printing or the like. When it is not necessary to selectively dispose a fine pattern, a synthetic resin containing a filler may be applied by another method. Here, if there is a problem in the adhesion between the base 20 and the synthetic resin, one or more underlayers may be formed.

The synthetic resin containing the filler is preferably the same type as the synthetic resin on the surface of the substrate 20, for example, epoxy resin, polyethylene, phenol resin, urethane resin or the like is used as a base to impart predetermined curing characteristics. For this reason, a polymerization initiator, a colorant, a dispersant, a solvent and the like are appropriately mixed. The solvent is mixed to adjust the viscosity of the synthetic resin, and the mixed amount is adjusted by the coating thickness and the coating method in the coating process.

Fine particles of calcium carbonate, barium sulfate, magnesium oxide and the like are mixed as fillers in this synthetic resin. The particle size of this filler is 0.05μ
The thickness is preferably about m to 10 μm, and particularly preferably 5 μm or less. Further, the compounding amount of the filler is about 5 to 25% by weight. The thickness of the synthetic resin is preferably about 15 to 60 μm.

Next, the filler-containing synthetic resin is subjected to a curing treatment to form a plating coating layer 21. This curing treatment is performed by heating when the synthetic resin is a thermosetting resin and by irradiating light when the synthetic resin is a photocurable resin. For example, heat treatment at 150 ° C. for 30 minutes is applied to a resin coated with an epoxy resin-based synthetic resin mixed with calcium carbonate or barium sulfate having an average particle diameter of 3 to 5 μm as a filler to a thickness of 30 to 45 μm. By doing so, it can be almost completely cured.

The surface side of the coating layer 21 for plating at this time is as shown in FIG. 2 (a). When the coating layer to be plated 21 cannot be formed to have a desired thickness in one coating or printing process, the synthetic resin 21A is once cured, and then the synthetic resin is coated again to be cured. By repeating a plurality of steps, it can be formed to an arbitrary thickness.

Next, the surface 21 of the coating layer 21 for plating
a is polished by buffing as shown in FIG.
The surface of the coating layer 21 to be plated is approximately 0.5 to 1.0 μm.
Surface 2 where a part of the filler 21B is exposed after being removed to some extent
1b is formed. This surface state is shown in FIG. In the buffing, the hardened layer near the surface 21a is removed, and a part of the filler 22 embedded inside is exposed on the surface. The filler 21B largely exposed on the surface 21b in this polishing step is removed during polishing,
A fine surface hole 30 is formed.

In the buffing process, the plated coating layer 21
Of the buff and other polishing materials, which do not contain much filler 21B formed in the vicinity of the surface 21a and are relatively hard as compared with the inside, or to partially break this surface layer. It is sufficient for the member to lightly contact the surface. This step is not limited to a mechanical polishing method such as buffing or polishing cloth, but may be a chemical polishing method such as etching using a corrosive solution.

Next, as shown in FIG. 1C, the surface 21
Abrasive grains such as alumina are sprayed on b together with water, and scrubbing is performed. The conditions that the present inventors are actually performing are
The spraying pressure (water pressure) is 2 kg / cm ² , and the average grain size of the abrasive grains is about 55 μm (mesh No. 220). This scrubbing may be a step in which abrasive grains are struck with a predetermined strength, and may be simply sandblasting (no water is required).

By this scrubbing process, the surface 21b of the coating layer 21 to be plated is roughened on average, and the striped polishing marks formed in the buffing process are almost completely disappeared and become uniform. A rough surface 21c is formed. At this time, as shown in FIG. 2 (c), a large number of surface recesses 40 are formed on the surface 21c by hitting the abrasive grains,
Due to the surface recess 40, a larger number of fillers 21B are exposed on the surface 21c.

Here, the abrasive grains at the time of scrubbing are larger than the grain size of the filler 21B.
It is approximately 10 times or more the particle size of B. Thus the surface 21
By increasing the grain size of the abrasive grains hitting b, it is possible to eliminate the risk of the abrasive grains being driven into the plating-coated layer 21 and being embedded therein. The reason for increasing the particle size of the abrasive grains is that if the abrasive grains remain in or on the surface of the coating layer to be plated, the adhesion of the plating layer is reduced and the smoothness of the surface of the plating layer is impaired. The particle size of the abrasive grains and the water pressure during scrubbing are adjusted by the hardness of the coating layer to be plated so that the abrasive grains will not be embedded in the coating layer to be coated or remain on the surface.

Next, the surface purification treatment is performed on the plated coating layer 21 having the surface 21c shown in FIG. 2 (c). This treatment is performed on the surface 21c after scrubbing.
This is for removing the abrasive grains and chemicals remaining on the top. This purification treatment is, for example, washing with hot water or water, soft etching, etc., but the filler 21B exposed on the surface 21c is eluted by sulfuric acid, sodium persulfate, etc. used in the soft etching and a large number of particles are left on the surface. The surface hole appears. The number of surface holes formed by elution of the filler 21B is increased as compared with the normal case due to the presence of the filler 21B exposed more in the surface recess 40.

As shown in FIG. 1 (d), on the plated coating layer 21 having a large number of surface holes, as shown in FIG.
Until electroless plating of gold, silver, copper, nickel, zinc, etc. and their alloys is performed, the surface holes are fully filled with the plating layer, and the entire surface of the plated coating layer is sufficiently covered with the plating layer. The plated layer 22 is formed.

After that, the surface of the plated layer 22 is subjected to a purification treatment, and then electrolytic plating for depositing the same kind of metal is performed to form the plated layer 23. This electrolytic plating is plating layer 2
Performed until a total thickness of 2,23 is formed to the desired thickness.

As described above, in this embodiment, the scrubbing is performed after the mechanical polishing to eliminate the traces during the mechanical polishing to eliminate the polishing habit, and to form a uniform rough surface, and at the same time, in the vicinity of the surface. Since the existing filler can be exposed, the number of surface holes after elution of the filler can be increased, which improves the adhesion of the plating layer and enhances the adhesion, and at the same time, improves the adhesion of the plating layer. The smoothness can be improved.

FIG. 3 shows a plating layer forming process in the process of forming the multilayer circuit board. In this forming step, the multilayer circuit boards are sequentially stacked in a build-up method. An annular conductive portion 51 corresponding to the edge of the blind via hole selectively formed in the substrate and exposed on the surface, and a wiring portion 52 formed in a predetermined pattern on the surface of the substrate are respectively planned above. When connecting to a wiring circuit, the plating layer deposition method as described above is used. Here, the conductive portion and the wiring portion are also copper patterns formed by the plated layer.

FIG. 3A shows a state in which two layers of insulating resists 61 and 62 are laminated in a state in which the conductive portion 51 and the wiring portion 52 which need to be connected to the upper layer are avoided. As shown in FIG. 3 (b), a plating coating layer 63 similar to the above is formed on the insulating resists 61 and 62 by screen printing and curing. The plating coating layer 63 is applied so as to contact the peripheral portions of the conductive portion 51 and the wiring portion 52, and yet leave the exposed portions of the conductive portion 51 and the wiring portion 52 sufficiently.

The above-mentioned plated wear coating layer 63 is subjected to the above mechanical polishing and scrubbing, and a large number of surface holes (not shown) are formed on the surface thereof. At this time, due to the bleeding of the screen printing, the partially conductive portion 51 and the wiring portion 5
If there are surplus portions 63a and 63b of the coating layer to be coated with plating formed on the unnecessary portions on the surface of No. 2, as shown in FIG. 3 (c), the plating layer 64 and the conductive portion 51 formed thereon are formed. , The excess portions 63a, 6 between the wiring portion 52 and
3b intervenes, which deteriorates the electrical conductivity and reduces the adhesiveness of the plating layer at these connecting portions.

However, at the time of scrubbing in this embodiment, the conductive portion 5 is formed at the same time as the surface of the plated coating layer 63.
1. Since the surface of the wiring portion 52 is also hit with the abrasive grains, these surplus portions 63a and 63b can be removed by the abrasive grains. Since the scrubbing is basically performed on the entire surface of the substrate, it is not necessary to form a mask for performing a selective treatment, and the surface of the conductive pattern is also cleaned with abrasive grains as described above. You can Furthermore, since this scrubbing step also forms irregularities on the surface of the conductive pattern itself, it is possible to enhance the adhesion of the plating layer even at the connection portion with the lower layer.

[0033]

As described above, according to the present invention,
In the filler elution step, more surface holes can be formed on the surface of the plated coating layer,
Since the surface condition can be made uniform, the adhesion and durability of the plating layer formed thereon can be improved, and at the same time, the smoothness and uniformity of the plating layer can be improved. .

When the plating layer and the lower conductor are connected to each other, the surface of the conductor is covered with a plating coating layer,
Even if unnecessary materials such as an insulating resist adhere, these adhered substances can be removed in the roughening treatment step. Further, in this step, since the surface of the conductor is hit by the fine particles, fine irregularities are formed on the surface, so that the adhesion between the conductor and the plating layer can be improved.

[Brief description of drawings]

FIG. 1 is a process drawing (a) to (d) for explaining an embodiment of a method for depositing a plating layer according to the present invention.

FIG. 2 is a schematic explanatory view (a) for explaining the surface condition of the plated coating layer in the same example step by step.
It is (c).

FIG. 3 is a schematic explanatory view (a) to (c) showing a state where the same embodiment is applied to the surface of a substrate having a conductive portion and a wiring portion.
It is.

FIG. 4 is a schematic explanatory view (a) showing a surface state of a plating coating layer for explaining a conventional plating layer coating method.
It is (c).

[Explanation of symbols]

 20 Base Material 21 Plating Covering Layer 21A Synthetic Resin 21B Filler 21a, 21b, 21c Surface 22 Electroless Plating Layer 23 Electroplating Layer 30 Surface Hole 40 Surface Recess

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yoshiko Nakajima 4-125, Shinmeicho, Okaya City, Nagano Prefecture Daiwa Kogyo Co., Ltd. (72) Inventor Mitsuhiko Kitamura 4-125, Shinmeicho, Okaya-shi, Nagano Prefecture Daiwa Industry Co., Ltd.

Claims (3)

[Claims] 1. A composition coating step of coating an object to be plated with a composition to be plated, which is obtained by filling a resin having a reactive group with a filler, and plating the composition to be plated by polymerizing and curing the composition to be plated. A curing treatment step of forming a coating layer, a polishing step of polishing the surface of the coating layer to be plated, a roughening treatment step of hitting the polishing surface of the coating layer to be plated with fine particles, the coating to be plated The elution treatment step of eluting the filler from the roughened surface of the coating layer, and the plating treatment step of performing a plating treatment on the surface of the plating adhered coating layer after the elution treatment How to wear. 2. The surface-roughening treatment step according to claim 1, wherein the fine particles are struck with a strength such that the fine particles are not embedded inside the coating layer to be plated. Method of depositing plating layer. 3. The method for depositing a plating layer according to claim 1, wherein the particle size of the fine particles is larger than that of the filler.