Method of electroplating and depositing metal

A method of electroplating and depositing metal includes: providing an insulation substrate formed with conductive through holes; forming a first conductive layer on a first surface of the insulation substrate and forming a resist layer on a first portion of the first conductive layer, leaving a second portion of the first conductive layer uncovered by the resist layer as a to-be-plated area; disposing the insulation substrate in a first electroplating solution and depositing a first metal layer on the to-be-plated area; removing the resist layer and the portion of the first conductive layer; forming a second conductive layer on a second surface of the insulation substrate; forming a mask layer on the second conductive layer; disposing the insulation substrate in a second electroplating solution and depositing a second metal layer on the first metal layer of the to-be-plated area; and removing the mask layer and the second conductive layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electroplating technology, and, more particularly, to a method of depositing metal on an insulation substrate.

2. Description of Related Art

In the conventional electroplating on an insulation substrate, the critical step of forming a metallization pattern is that a position to be formed with a metallization pattern on an insulation substrate needs to be electrically connected to a cathode (a negative electrode) performing a reduction such that metal ions in electroplating solution are deposited on the insulation substrate via the reduction. For example, if copper is to be electroplated on the specific position of an insulation substrate, the portion of the insulation substrate that is not be electroplated with copper is masked. Then the insulation substrate is placed in electroplating solution. The specific position of the insulation substrate is electrically connected to a negative electrode, and copper ions are then reduced on the specific position of the insulation substrate to form a metallization pattern.

In the electroplating technology, there are acidic and basic electroplating solutions, and the acidic electroplating solution is better for usage due to its compatibility. In the prior art, the resist layer, such as a dry film or a photoresist, has anti-acid property but has no anti-alkali property. In the basic electroplating solution, the dry film or the photoresist has poor attachment. Currently, electroplating with leading wires and cured resist layer are used in the basic electroplating solution for electroplating.

FIG. 1AtoFIG. 1Gare sectional views illustrating conventional metal deposition in the electroplating solution by using leading wires according to the prior art. As shown, a conductive layer2is sputtered on an insulation substrate1, a resist layer3is applied to form a pattern30to be plated, and a leading wire31(shown in FIG.1C′) is provided. In the electroplating of Cu, Ni and Ag, the acidic electroplating solution is used for electroplating Cu, and the basic electroplating solution is used for electroplating Ag, such that the two electroplating procedures need to be performed separately. The insulation substrate1is then placed in the acidic electroplating solution, and the resist layer3has anti-acid property and thus has desired attachment property to the substrate. After the copper4is deposited on the pattern30and on the leading wire31of the insulation substrate1, the resist layer3and the exposed conductive layer2are removed. Then, as shown inFIG. 1G, the electroplating of Ni and Ag is performed respectively. For this process, the resist layer3has no anti-alkali property and thus needs to be removed, and the pattern30is electrically connected to the negative electrode via the leading wire31, so as to complete the deposition of the Ni and Ag5. In order to selectively plate a metal layer on the surface of the insulation substrate1in the basic electroplating solution, the metallization structure of the insulation substrate1includes the pattern30and the leading wire31which is electrically connected to the pattern30. When the leading wire31having Cu, Ni and Ag between the two patterns30is formed, a dicing blade or laser light would be affected by the leading wire31during cutting and thus the blade edge may be destroyed once it is in touch with metal or the energy of laser spot is reflected by the leading wire31without absorption from the insulation substrate1. Therefore, these two cutting machines will fail to completely separate the insulation substrate1. Further, the patterns30are electrically connected to one another by the leading wire31, such that the open circuit or short circuit test of each of the patterns30on the insulation substrate1cannot be performed due to the electrical connection formed by the leading wire31.

FIG. 2is a sectional view showing a cured resist layer for the electroplating according to the prior art. The electroplating shown inFIG. 2is similar to that inFIG. 1. An insulation substrate1is provided, a conductive layer2and a resist layer3are formed to construct a pattern30to be plated (as shown in FIG.2C′) and the electroplating is performed in the acidic electroplating solution to form the copper4. At this time, the resist layer3is not removed and the resist layer3is cured by baking (as shown inFIGS. 2D and 2E, the resist layer3is cured to be the resist layer3′). The electroplating of the nickel layer is subsequently performed, and then the substrate is provided in the basic electroplating solution, so as to form the deposition of the silver5. In this method, the cured resist layer3′ has a little anti-alkali property, such that it is necessary for the electroplating to be completed in a short period of time. For example, upon the development of the dry film the baking is performed before electroplating, or upon the development of the dry film the hard baking is formed to enhance curing, so as to improve the anti-alkali property of the dry film. However, this method has poor stability, and peeling of the resist layer may occur in the basic electroplating solution since the basic solution, NaOH, for example, is just used for removing the resist layer. Moreover, during removing the over cured resist layer3′, residual films may stay in slots between metals. It is hard to completely clean those residual films.

Briefly, the metal electroplating in the basic solution should be further improved. Conventional leading wire method may cause a big problem during the cutting process with a dicer or a laser. On the other hand, using cured resist layer in the basic electroplating cannot provide a stable yield in production due to the film residue. There is a need to improve the electroplating in the basic electroplating solution, so as to simplify the processing and reduce the cost.

SUMMARY OF THE INVENTION

The present invention provides a method for electroplating and depositing metal in an acidic or basic electroplating solution via a conductive layer and a mask layer.

In accordance with the present invention, the method includes: providing an insulation substrate formed with a plurality of conductive through holes; forming a first conductive layer on a first surface of the insulation substrate, forming a resist layer on a portion of the first conductive layer, and leaving a second portion of the first conductive layer uncovered by the resist layer as a to-be-plated area; disposing the insulation substrate in a first electroplating solution and depositing a first metal layer on the to-be-plated area; removing the resist layer and the first portion of the first conductive layer; forming a second conductive layer on a second surface of the insulation substrate opposing the first surface, and forming a mask layer on the second conductive layer; disposing the insulation substrate in a second electroplating solution and depositing a second metal layer on the first metal layer of the to-be-plated area; and removing the mask layer and the second conductive layer.

In accordance with the present invention, it is not necessary to perform metal deposition in the first electroplating solution with an acidic electroplating solution. In other words, the metal electroplating-deposition method of the present invention is capable of being applicable to an acidic electroplating solution or a basic electroplating solution. For example, the first electroplating solution is an acidic electroplating solution, and the second electroplating solution is a basic or acidic electroplating solution.

In an embodiment of the present invention, the conductive through hole is made of silver conductive paste or copper.

In another embodiment of the present invention, the second metal layer is deposited in the to-be-plated area by electrically connecting the conductive through hole and the second conductive layer to a cathode of an electroplating system, and thus the second metal layer is an electroplated nickel layer and an electroplated silver layer.

In another embodiment of the present invention, the mask layer is a plating resist tape or a tooling fixture for preventing the electroplating solution from penetration.

In addition, the present invention further provides a method of electroplating and depositing metal, including: providing an insulation substrate formed with a plurality of conductive through holes; forming a first metal layer on a first surface of the insulation substrate and forming a second conductive layer on a second surface of the insulation substrate opposing the first surface; forming a mask layer on the second conductive layer; disposing the insulation substrate in an electroplating solution and depositing a second metal layer on the first metal layer; and removing the mask layer and the second conductive layer.

In the method of electroplating and depositing metal according to the present invention, the reduction deposition is performed based on the electrical interconnection of both surfaces of the insulation substrate, and both the acidic electroplating solution and the basic electroplating solution can be used. In comparison with the prior art of exposed leading wires or cured resist layers, the method of electroplating and depositing metal according to the present invention can be performed stably in acidic or basic electroplating solution and has an improved yield and reduced cost.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following specific examples are used for illustrating the present invention. A person skilled in the art can easily conceive the other advantages and effects of the present invention.

FIGS. 3A to 3Lare sectional views illustrating electroplating metal in an electroplating solution according to a method of electroplating and depositing metal of the present invention. The method of the present invention can be practiced in an acidic electroplating solution or a basic electroplating solution. In an embodiment of the present invention, the electroplating of copper is performed in the acidic electroplating solution, and the electroplating of silver is performed in the basic electroplating solution. In accordance with the present invention, the metal and electroplating solution are not limited to those described in the embodiments.

As shown inFIG. 3A, an insulation substrate10having a first surface and a second surface opposing to the first surface is provided. The insulation substrate10can be made of aluminum nitride or aluminum oxide.

As shown inFIG. 3B, a conductive through hole11is formed in a specific position of the insulation substrate10, and can be made of a silver conductive paste or a copper. In an embodiment, the conductive through hole11is used as the electrical connection between the first surface and the second surface of the insulation substrate10while filling the silver conductive paste or electroplating copper.

As shown inFIG. 3C, a first conductive layer20is formed on the first surface of the insulation substrate10, and includes a titanium layer and a copper layer formed by sputtering.

As shown inFIG. 3D, a resist layer80is formed on the first surface of the insulation substrate10, and a portion of the first conductive layer20that is not covered by the resist layer80is used as a to-be-plated area81. The resist layer80may be a dry film or a photoresist for covering a portion of the first conductive layer20that is not to be electroplated. In other words, the resist layer80is formed on a specific position of the first surface according to the pattern to be plated, and the portion, which is to be plated, is the to-be-plated area81. FIG.3D′ shows the top view of the sectional view shown inFIG. 3D, wherein the to-be-plated area81is an area where metal is electroplated and deposited.

As shown inFIG. 3E, the insulation substrate10shown inFIG. 3Dis disposed in the acidic electroplating solution, and then a first metal layer40is deposited in the to-be-plated area81. Due to the operation in the acidic electroplating solution, the first metal layer40can be the electroplated copper layer.

As shown inFIG. 3F, the resist layer80inFIG. 3Eis removed. In the prior art, since the resist layer80has no anti-alkali property, the cured resist layer used for electroplating in the basic electroplating results in residual films in slots between metals. In an embodiment of the present invention, the resist layer80is not formed by curing, and thus will not be peeled off in the basic electroplating solution or stay in slots between metals.

As shown inFIG. 3G, the first conductive layer20under the resist layer80, i.e., a portion of the first conductive layer20exposed from the first surface, is removed, such that the first metal layer40is electrically isolated. In other words, after removing the resist layer80, the exposed first conductive layer20is removed, such that the first metal layer40cannot be electrically connected to one another via the first conductive layer20, so as to facilitate the open circuit or short circuit test of an electroplated pattern formed by the first metal layer40.

As shown inFIG. 3H, a second conductive layer60is formed on a second surface of the insulation substrate10opposing the first surface. In an embodiment, the second conductive layer60can be a copper layer only formed by sputtering.

As shown inFIG. 3I, a mask layer70is formed on the second conductive layer60of the second surface of the insulation substrate10, so as to prevent the second conductive layer60on the second surface from being exposed and to prevent metals from being deposited on the second surface during electroplating. The mask layer70may be a plating resist tape or a tooling fixture for preventing the electroplating solution from penetration.

As shown inFIG. 3J, the insulation substrate10inFIG. 3Iis placed in a basic electroplating solution, and then a second metal layer50is deposited on the first metal layer40in the to-be-plated area81. The conductive through holes11and the second conductive layer60are used for electrically connecting the negative electrode (cathode) of the electroplating system, and thus metal ions are deposited on the first metal layer40, such that the second metal layer50is deposited. Since the operation is performed in the basic electroplating solution, the second metal layer50may be the electroplated silver layer.

Referring toFIG. 3J, in another embodiment of the present invention, the insulation substrate10is placed in an acidic electroplating solution, a barrier layer (not shown) is formed on the first metal layer40in the to-be-plated area81, such as nickel electroplating, then the insulation substrate10is placed in a basic electroplating solution, and silver is deposited on the electroplated nickel layer. In other words, the second metal layer50includes the electroplated nickel layer and silver layer.

As shown inFIGS. 3K and 3L, the mask layer70and the second conductive layer60are removed. The second metal layer50is formed on the first metal layer40, and the structure is similar to the structures shown inFIGS. 1G and 2H.

In another embodiment of the present invention, an insulation substrate with a conductive through hole is provided, a first metal layer is formed on a first surface of the insulation substrate, a second conductive layer is formed on a second surface of the insulation substrate opposing the first surface, a mask layer is formed on the second conductive layer, the insulation substrate is placed in a second electroplating solution, a second metal layer is deposited on the first metal layer, and the mask layer and the second conductive layer are removed. In an embodiment of the present invention, the insulation substrate with the first metal layer is provided (as shown inFIG. 3G), and then the procedures shown inFIGS. 3H to 3Lare performed, so as to complete the method of electroplating and depositing metal according to the present invention. In an embodiment, the first metal layer and the second metal layer are not limited to be formed in sequence, and the insulation substrate having a metal layer can be used in the method of electroplating and depositing metal according to the present invention.

In the method of electroplating and depositing metal according to the present invention, the insulation substrate can be used in the acidic or basic electroplating solution for electroplating, wherein the second conductive layer and the mask layer are formed for electrical connection, electrons from the negative electrode are coupled with metal ions on the surface of the first metal layer via the second conductive layer, the conductive through hole, the first conductive layer and the first metal layer, and thus the metals are deposited on the surface of the first metal layer. Therefore, metal layers can be sequentially formed on both surfaces of the insulation substrate by using the present invention, so as to eliminate the drawbacks resulting from using the conventional leading wires and cured resist layers.

Hence, in the method of electroplating and depositing metal according to the present invention, the reduction deposition is performed based on the electrical interconnection of both surfaces of the insulation substrate, and both the acidic electroplating solution and the basic electroplating solution can be used. In comparison with the prior art of exposed leading wires or cured resist layers, the method of electroplating and depositing metal according to the present invention can be performed stably in acidic or basic electroplating solution and has an improved yield and reduced cost.

The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements.