JP3732266B2 - Fine thick-film connection substrate and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal or LSI mounting board / connection component having a high wiring density and a method for manufacturing the same.
[0002]
[Prior art]
Generally, an LCD chip is mounted on the surface of a liquid crystal drive circuit board, and the board and LSI are connected by wire bonding, or an LSI chip on which bumps are two-dimensionally arranged is mounted face-down on the board, and the other connection terminals of the board The portion is connected to the terminal portion of the liquid crystal substrate with an anisotropic conductive sheet (ACF). Here, with the advent of liquid crystal VGA and S-VGA, a higher-density mounting substrate is required. On the other hand, since the connection terminals are laid out one-dimensionally on the four outer sides of the chip, the degree of integration of the LSI It does not go up and hinders cost reduction.
[0003]
Also, when connecting with an anisotropic conductive sheet, if the conductor is convex from the substrate surface, the protrusions protruding from both surfaces to be connected will be staggered and short-circuited. Therefore, it is necessary for such a substrate to flatten either one of the substrate surfaces. Therefore, there is a strong demand for a substrate having a high wiring density and a structure in which no conductor protrudes from the substrate surface.
[0004]
[Problems to be solved by the invention]
Conventionally, such a connection substrate has been made by an etching method. However, as the wiring density increases, a so-called plating method, that is, a method of forming a conductor at a necessary place by plating has become effective. In particular, the method of forming a wiring board by forming a resist on a conductive substrate, forming a conductor by performing electroplating with the substrate as a cathode, and then bonding together with a prepreg with the plated surface facing inward, and removing the conductive substrate It is valid. According to this method, the shape of the conductor is controlled by the resist wall, and even if the wiring density is high, the thickness can be increased, and as a result, the circuit resistance can be reduced. Moreover, since no conductor protrudes from the surface of the substrate, ACF connection is also good.
[0005]
However, in such a substrate, the connection portion needs to be plated with gold in order to improve connection reliability by wire bonding or ACF. The gold plating layer diffuses with the underlying copper, and the gold layer disappears from the surface due to heat and neglect. Therefore, in general, after a diffusion preventing film such as Ni or an alloy thereof is drawn on copper, gold plating is performed.
However, even if the surface becomes flat, if Ni plating is further performed, the surface becomes convex because of this, and at the same time, the space between the lines becomes narrow (see FIG. 2). As a result, the following problems occur.
[0006]
(1) On a high wiring density substrate, if Ni plating is performed, for example, by 5 μm (a general thickness as a base for gold plating), the distance between the lines becomes almost twice that of 10 μm. This is because Ni plating is particularly smooth and has the property of spreading as much as or more than the thickness. Accordingly, the insulation between lines is lowered. Further, a convex portion of about 5 μm is formed on the surface, which becomes a problem in ACF connection at a fine pitch.
{Circle around (2)} If a convex portion is formed on the surface, various treatments cause the treatment liquid to remain on the convex portion and cause migration. In addition, migration increases because the surface area of the circuit pattern exposed to the environmental atmosphere increases.
[0007]
[Means for Solving the Problems]
Therefore, in order to solve the above problems, the present invention provides a fine-thick film connection substrate having a wiring pitch of 80 μm or less at least at one place and a conductor thickness at that place being ½ or more of the wiring pitch. A portion not contacting the insulating material is covered with a first metal layer capable of preventing the diffusion of gold, and the conductor pattern including the first metal layer is embedded in the same insulating material. The second metal layer made of gold or an alloy thereof is formed on a part of the surface of the substrate, and the diffusion barrier metal is Ni, Ti, W or The fine thick film connection substrate, characterized in that it is an alloy thereof, or an alloy containing any one of them, and the diffusion preventing metal is Ni-P or Ni-B. Provide board Is shall.
[0008]
In order to solve the above problems, a step of forming a resist circuit pattern on the conductive substrate, a step of plating a diffusion preventing metal on the surface of the substrate on which the resist is not formed, and further forming a circuit pattern of the conductive substrate Plating the surface with a conductive metal to form a conductor pattern having a thickness of 1/2 or more of the pitch, removing the resist, and forming the conductor pattern inside, the substrates between each other, or an insulating substrate A method for producing a fine thick film connecting substrate comprising a step of adhering to both or one side of the substrate and a step of dissolving and removing the substrate, a step of performing a zincate treatment on a substrate made of aluminum or an alloy thereof, and an alkali A step of forming a circuit pattern of a development type dry film resist, and Ni or Ni-P or The step of plating i-B and the surface of the conductive substrate on which the circuit pattern is formed are subjected to acidic electrolytic copper plating, and copper having a thickness more than 1/2 times the pitch of the highest wiring density in the substrate is formed. A fine process comprising a step of forming, a step of removing the dry film resist, a step of bonding the substrates with the formed conductive pattern on the inside, or adhering to both or one side of an insulating substrate, and a step of dissolving and removing the substrate A method of manufacturing a thick film connection substrate is provided.
[0009]
[Action]
In the present invention, a gold diffusion prevention layer, which is a surface protective metal for connection, is embedded in a substrate insulating layer including a Ni plating layer, for example, so that insulation between lines can be prevented and the surface is prevented from diffusion. By smoothing including the layers, it is possible to eliminate the residual treatment liquid that causes copper migration and the surface area of the circuit pattern exposed to the environmental atmosphere, thereby improving the reliability.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to examples.
A substrate made of aluminum or an alloy thereof is used as the conductive substrate of the present invention. Since the surface property of the substrate greatly affects the surface property of the final product, a substrate having a mirror surface as much as possible is preferable. The thickness of the substrate can be freely selected, but generally 10 μm to 200 μm is preferable. If it is too thin, wrinkles and scratches are likely to occur during handling, and the resistance increases and the uniformity of the electrolytic plating is impaired.
Further, the purity of aluminum is preferably 99% or more, preferably 1N30 or more according to the so-called JIS standard of 99.6% or more. If the purity is too low, uniformity in plating and unevenness in substrate etching occur.
[0011]
The resist used in the present invention is resistant to chemicals after the resist process, has a thickness of about the required conductor thickness, and can obtain a necessary resolving power at that thickness, but generally has a high resolving power. A dry film resist is preferable from the viewpoint of workability. Further, among dry films, an alkali development type dry film is preferable in view of environmental measures and ease of peeling.
Next, when forming a circuit pattern of an alkali development type dry film resist, the substrate is replaced with zinc prior to the resist process in order to further improve the adhesion of the dry film resist and prevent light reflection during mask exposure from the substrate surface. It is better to perform plating, so-called zincate treatment. This makes it possible to form a resist having a high aspect necessary for plating a fine and thick conductor, that is, a resist having a narrow width and a large thickness (see FIG. 3). The resist thickness depends on the resolution of the resist and the surface state of the zincate base, but is preferably equal to or greater than the thickness of the conductor to be finally obtained.
[0012]
The first metal layer is formed by plating a diffusion preventing metal on the surface of the substrate on which no resist is formed. As the diffusion preventing metal, any one of Ni, Ti, W, or an alloy thereof, or an alloy containing any one of them is used, and Ni or its alloys Ni-P and Ni-B are particularly preferable from the viewpoint of diffusion preventing characteristics and economy. Is preferred. This Ni (or Ni alloy) layer serves as a barrier layer that prevents the acid resistance of the aluminum substrate, while protecting the substrate from acid copper plating, which is a subsequent process, and preventing copper migration from the substrate in the final product. There is an effect of preventing protrusion from the substrate surface.
The plating of the diffusion preventing metal may be electrolytic plating or electroless plating, but electroless plating is particularly advantageous in terms of equipment. Here, any plating solution may be used. However, since the dry film resist dissolves when it is alkaline, a neutral or acidic plating solution is desirable. Further, considering the dissolution of the base material in the plating solution, it is desirable that it is close to neutrality. In this respect, Ni or an alloy thereof is preferable because there are many plating solutions close to the neutral region.
[0013]
Next, the main second metal layer of the conductor pattern is formed. As the conductor pattern, a conductive material such as copper, copper alloy, copper silver alloy or the like is used, and the conductor thickness is preferably 1/2 or more of the wiring pitch. For example, acidic electrolytic copper plating is performed on the surface of the conductive substrate on which the circuit pattern is formed using the substrate as a cathode, thereby forming copper having a thickness of 1/2 times or more the minimum pitch in the substrate (see FIG. 4). Further, when the plating thickness is thin, the circuit resistance of the formed substrate increases, and when used in a liquid crystal driving circuit, the S / N ratio of the screen decreases. Moreover, the frequency which can be transmitted falls by circuit resistance becoming high.
In the case of performing acidic copper plating, the resist is dissolved by an alkaline copper plating solution. Therefore, copper sulfate plating that can form good quality copper at low cost by selecting a good additive is preferable.
After the plating is finished, the dry film resist is removed. Generally, caustic soda is used.
[0014]
Next, the formed conductor pattern is used as an inner side, and the substrates are bonded to each other or both surfaces or one surface of the insulating substrate by using an adhesive (see FIG. 5). A commonly used prepreg or an adhesive sheet (in this case, the sheet may have an adhesive on both sides of the base film or may be an adhesive only) may be used.
The adhesive used here becomes an insulating material after curing. Moreover, it becomes an insulating material including the base film which has the adhesive agent on both surfaces of the base film.
Next, the substrate is dissolved and removed. As the solution to be dissolved, a solution having a sufficiently high speed for dissolving the conductive substrate than the speed for dissolving the conductor pattern and the diffusion preventing metal is selected. For example, if the conductor pattern is copper, the diffusion preventing metal is Ni, and the substrate is aluminum, about 10% hydrochloric acid is preferable.
[0015]
Finally, gold plating is performed as necessary (see FIG. 6). Actually, the lands used for bonding are plated with gold. This may be any gold plating process usually performed on Ni plating, but the plating thickness is usually 1 μm or less. Further, from the viewpoint of cost, if there is an unnecessary part before gold plating, the unnecessary part may be coated with a gold-resistant plating resist.
The conductor pattern of the fine thick film connecting substrate obtained by the manufacturing method of the present invention is embedded in the same insulating material including the diffusion prevention metal layer described above, and the surface is smooth, and therefore, the surface is contaminated. Since there is no migration, it becomes a fine thick film connection substrate without migration (see FIG. 1). Hereinafter, although an Example is given, this invention is not limited to these.
[0016]
[Example 1]
The surface aluminum foil with a thickness of 150 μm and a purity standard of 1N30 was treated with a solution obtained by diluting Uemura Kogyo Co., Ltd. zincate solution (AZ-401-3X) three times at a liquid temperature of 30 ° C. for 80 seconds. After washing with water, it was washed with 15% nitric acid for 20 seconds, treated again with the zincate solution at a temperature of 30 ° C. for 80 seconds, and then washed with water.
Next, dry film resist (SPG-201, thickness 20 μm) manufactured by Asahi Kasei Kogyo Co., Ltd. is laminated, and a mask pattern with a line pitch of 50 μm, a line width of 25 μm (width from which the resist is removed), and a line pattern of 25 μm is exposed with an exposure device. And developed.
The obtained substrate was Ni-P electroplating solution manufactured by Okuno Pharmaceutical Co., Ltd., trademark Nickelin bath (L Nickelin D 200 cc / liter, nickel sulfate 150 g / liter, sodium chloride 30 g / liter), liquid temperature 60 ° C., 8 minutes. Plating was performed to form a Ni—P layer of about 5 μm. Next, 30 μm of copper was plated with a copper sulfate plating solution to form a pattern with a pitch of 50 μm, a line width of 25 μm, and a pattern thickness of 35 μm.
[0017]
Next, the dry film resist was removed with 3% caustic soda, and the substrate obtained above was bonded through a prepreg manufactured by Hitachi Chemical Co., Ltd. (GEA-67N KLN) with the side having the copper plating pattern inside. Next, the aluminum substrate was dissolved and removed with 10% hydrochloric acid.
Since the portion of the obtained substrate that is exposed on the surface of the circuit pattern is covered with Ni-P, the replacement plating is directly performed thereon with a replacement-type electroless gold plating solution (trademark manufactured by N.E. Chemcat Co., Ltd.). Thereafter, a total of about 0.5 μm of gold was deposited using an autocatalytic electroless plating solution (trade name Super Mex # 600 manufactured by N.E. Chemcat Co., Ltd.).
The obtained substrate had a wiring density of 50 μm, a conductor thickness of 35 μm, and the surface was covered with Ni—P 5 μm + gold 0.5 μm. There were no defects in 150 100 mm × 30 mm substrates, and 50 V was applied between the lines at 60 ° C. There was no change in insulation between lines even after 1000 hours in a 90-95% environment.
[0018]
[Example 2]
A surface aluminum foil with a thickness of 80 μm and a purity standard of 1N30 was treated with a solution obtained by diluting a 3-fold zincate solution (AZ-401-3X) manufactured by Uemura Kogyo Co., Ltd. at a liquid temperature of 30 ° C. for 80 seconds. After washing with water, it was washed with 15% nitric acid for 20 seconds, treated again with the zincate solution at a liquid temperature of 30 ° C. for 80 seconds, and then washed with water.
Next, dry film resist (SPG-201, thickness 20 μm) manufactured by Asahi Kasei Kogyo Co., Ltd. is laminated, and a mask pattern having a line pitch of 26 μm, a line width of 13 μm (width from which the resist is removed) and a line spacing of 13 μm is exposed with an exposure device. And developed.
The obtained substrate was treated with Ni electroless plating solution (ICP-Nicolon U) manufactured by Okuno Pharmaceutical Co., Ltd. at 85 ° C. to form about 2 μm of Ni—P. Next, 15 μm of copper was plated with a copper sulfate plating solution to form a pattern with a pitch of 26 μm, a line width of 13 μm, and a pattern thickness of 17 μm.
[0019]
Next, the dry film resist was removed with 3% caustic soda, and the surface of the polyimide film (50 μm thickness) manufactured by Toray DuPont Co., Ltd. was used. The substrate obtained above was bonded with the side having the copper plating pattern inside. Next, the aluminum substrate was dissolved and removed with 10% hydrochloric acid.
[0020]
Since the portion of the obtained substrate that is exposed on the surface of the circuit pattern is covered with Ni-P, a direct replacement type electroless gold plating solution (trade name Super Mex # 200 manufactured by N.E. About 0.1 μm gold was deposited.
The obtained substrate had a wiring pitch of 26 μm, a conductor thickness of 17 μm, and the surface was covered with Ni—P 2 μm + gold 0.1 μm. There were no defects in 150 substrates of 80 mm × 15 mm, and 25 V was applied between the lines at 60 ° C. There was no change in insulation between lines even after 1000 hours in a 90-95% environment.
[0021]
[Example 3]
A surface aluminum foil with a thickness of 80 μm and a purity standard of 1N30 was treated with a solution obtained by diluting a 3-fold zincate solution (AZ-401-3X) manufactured by Uemura Kogyo Co., Ltd. at a liquid temperature of 30 ° C. for 80 seconds. After washing with water, it was washed with 15% nitric acid for 20 seconds, treated again with the zincate solution at a liquid temperature of 30 ° C. for 80 seconds, and then washed with water.
Next, dry film resist (SPG-201, thickness 20 μm) manufactured by Asahi Kasei Kogyo Co., Ltd. is laminated, and a mask pattern having a line pitch of 26 μm, a line width of 13 μm (width from which the resist is removed) and a line spacing of 13 μm is exposed with an exposure device. And developed.
The obtained substrate was treated with Ni-B electroless plating solution (Top Chemialoy B-1) manufactured by Okuno Pharmaceutical Co., Ltd. at a liquid temperature of 65 ° C. to form about 2 μm of Ni-B.
[0022]
Next, 15 μm of copper was plated with a copper sulfate plating solution to form a pattern with a pitch of 26 μm, a line width of 13 μm, and a pattern thickness of 17 μm.
Next, the dry film resist was removed with 3% caustic soda, and the surface of the polyimide film (50 μm thickness) manufactured by Toray DuPont Co., Ltd. was used. The substrate obtained above was bonded with the side having the copper plating pattern inside. Next, the aluminum substrate was dissolved and removed with 10% hydrochloric acid.
[0023]
Since the obtained substrate is covered with Ni-B at the surface of the circuit pattern, it is directly replaced with an electroless gold plating solution (trade name Super Mex # 200 manufactured by N.E. Chemcat Co., Ltd.). About 0.1 μm gold was deposited.
The obtained substrate had a wiring pitch of 26 μm, a conductor thickness of 17 μm, and the surface was covered with Ni—B 2 μm + gold 0.1 μm. There were no defects in 150 substrates of 80 mm × 15 mm, and 25 V was applied between the lines at 60 ° C. There was no change in insulation between lines even after 1000 hours in a 90-95% environment.
[0024]
[Comparative Example 1]
The surface aluminum foil with a thickness of 150 μm and a purity standard of 1N30 was treated with a solution obtained by diluting Uemura Kogyo Co., Ltd. zincate solution (AZ-401-3X) three times at a liquid temperature of 30 ° C. for 80 seconds. After washing with water, it was washed with 15% nitric acid for 20 seconds, again treated with the zincate solution at a liquid temperature of 30 ° C. for 80 seconds, and then washed with water.
Next, dry film resist (SPG-201, thickness 20 μm) manufactured by Asahi Kasei Kogyo Co., Ltd. is laminated, and a mask pattern having a line pitch of 50 μm, a line width of 25 μm (width from which the resist is removed), and a line spacing of 25 μm is exposed with an exposure device. And developed.
About 2 μm of copper was formed on the obtained substrate by copper pyrophosphate plating. At this time, partial peeling was observed on the dry film.
[0025]
Next, 33 μm of copper was plated with a copper sulfate plating solution to form a pattern with a pitch of 50 μm, a line width of 25 μm, and a pattern thickness of 35 μm.
Next, the dry film resist was removed with 3% caustic soda, and the substrate obtained above was bonded through a prepreg manufactured by Hitachi Chemical Co., Ltd. (GEA-67N KLN) with the side having the copper plating pattern inside.
Next, the aluminum substrate was dissolved and removed with 10% hydrochloric acid. Since the obtained substrate is copper on the surface of the circuit pattern, the surface is washed with 10% sulfuric acid, and then Ni electrolytic plating Watt bath is used. Luminous nickel # 66 process manufactured by Ebara Eugene Corporation (additive is # 610) , # 62, # 63, a bath solution containing a predetermined amount of Ni), and 5 μm of Ni was formed.
Further, about 0.5 μm of gold was deposited directly thereon by an electrolytic gold plating solution (ECF-68 manufactured by N.E. Chemcat Co., Ltd.).
[0026]
The obtained substrate has a wiring pitch of 50 μm, a conductor thickness of 35 μm, and an average line gap of 10 μm. However, depending on the substrate, there are many short-circuited parts that are thought to be due to dry film peeling, and there are places where the line gap appears to be 0 μm. there were. There are 93 defects in 150 substrates of 100 mm x 30 mm. The remaining 77 non-defective products were subjected to 50 V between the lines and left to stand for 1000 hours in an environment of 60 ° C. and 90 to 95%. Eight sheets had poor insulation.
[0027]
【The invention's effect】
The fine thick film connection substrate of the present invention is finer and thicker than the conventional substrate, but the gap between the lines is not narrowed by the diffusion prevention metal layer of the connection portion, and there is no migration by the diffusion prevention layer. It is a highly reliable substrate, and since there is no projection on the surface, it is also highly reliable in connection with an anisotropic conductive sheet. Therefore, high-density LSI and liquid crystal can be mounted.
Further, according to the method of the present invention, the above-mentioned fine thick film connection substrate can be manufactured in a short process, and a low-cost connection substrate can be supplied.
[Brief description of the drawings]
FIG. 1 shows a cross-sectional view of a fine thick film connecting substrate of the present invention.
FIG. 2 is a cross-sectional view of a conventional connection substrate.
FIG. 3 is a cross-sectional view in which a dry film resist is formed after a zincate treatment is performed on an aluminum substrate.
FIG. 4 is a cross-sectional view in which Ni plating and copper plating are further performed to form a conductor having a thickness of ½ times or more the wiring pitch.
FIG. 5 is a cross-sectional view of an aluminum substrate bonded with a prepreg with the surface on which the conductor is formed facing inward.
FIG. 6 is a cross-sectional view in which gold plating is formed on a Ni layer exposed on the surface after etching an aluminum substrate.
[Explanation of symbols]
1 Copper (pattern)
2 Insulating layer 3 Ni (or Ni-P or Ni-B) layer 4 Au layer 5 Aluminum substrate 6 Dry film resist (after pattern formation)
7 Jincate layer 8 Ni layer

Claims (2)

Diffusion of gold covering a conductor pattern, an insulating material, and a portion of the conductor pattern that is not in contact with the insulating material, wherein the wiring pitch is 80 μm or less at least at one place or more and the conductor thickness at that place is ½ or more of the wiring pitch A method for producing a fine thick film connecting substrate having a first metal layer capable of preventing the above and a second metal layer made of gold or an alloy thereof covering the surface of the first metal layer,
Forming a resist circuit pattern on a conductive substrate made of aluminum or an alloy thereof, and plating a first metal layer made of Ni, Ni-P, or Ni-B on a substrate surface on which no resist is formed; And a step of forming a conductive pattern selected from the group consisting of copper, copper alloy, and copper silver alloy on the surface of the conductive substrate on which the circuit pattern is formed , and a step of removing the resist. conductive substrate each other the conductor pattern in the inside over, or a step of adhering with a conductive substrate adhesive on both surfaces or one surface of an insulating substrate, a step of dissolving and removing the conductive substrate, the land used for joining A method for manufacturing a fine thick film connecting substrate comprising a step of gold plating . Diffusion of gold covering a conductor pattern, an insulating material, and a portion of the conductor pattern that is not in contact with the insulating material, wherein the wiring pitch is 80 μm or less at least at one place or more and the conductor thickness at that place is ½ or more of the wiring pitch A method for producing a fine thick film connecting substrate having a first metal layer capable of preventing the above and a second metal layer made of gold or an alloy thereof covering the surface of the first metal layer,
A step of performing a zincate process on a conductive substrate made of aluminum or an alloy thereof, a step of forming a circuit pattern of an alkali development type dry film resist, and Ni, Ni-P, or Ni-B on a substrate surface on which no resist is formed A step of plating the first metal layer comprising: a step of forming a conductive pattern of copper by performing acidic electrolytic copper plating on the surface of the conductive substrate on which the circuit pattern is formed; and a step of removing the dry film resist And a process of bonding conductive substrates or conductive substrates to both or one side of an insulating substrate with an adhesive with the formed conductor pattern inside, a step of dissolving and removing the conductive substrate, and bonding. A method for manufacturing a fine thick film connecting substrate comprising a step of gold-plating a land .

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