JP2002141666A - Manufacturing method for multi-layered copper plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a multi-layered copper plate which can efficiently etch away projecting copper around and in a small- diameter hole of the multi-layered copper plate and make external layer copper foil thin by etching. SOLUTION: The projection copper around and in the small-diameter hole is etched away by using a solution containing 0.5 to 10 wt.% hydrogen peroxide, 1 to 15 wt.% sulfuric acid, at least one of 0.001 to 1 wt.% tetrasol and a tetrasol derivative, and 0.005 to 0.5 wt.% phenyl uric acid at need. The surface of the copper foil is uniformly etched to make the copper thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer copper clad for effectively removing copper, for example, protruding copper and burr copper, protruding around the non-through hole of a copper clad plate having at least two copper layers. The present invention relates to a method for manufacturing a plate. More specifically, the present invention relates to forming a fine pattern by efficiently etching and removing a protruding copper or burr copper of an outer layer copper foil which is a problem in drilling by a carbon dioxide gas laser using a special etching solution. The printed wiring board using the multilayer copper-clad board obtained by the perforation is used for a small semiconductor plastic package or the like.

[0002]

2. Description of the Related Art In forming a high-density fine circuit used for a semiconductor plastic package or the like, a three-dimensional connection is performed in addition to a planar connection. In recent years, non-through holes (blind via holes) for three-dimensional connections have become smaller and smaller than 0.15 mm in diameter. For such small holes, a carbon dioxide laser has been used in place of conventional mechanical drilling. A hole is formed by the above method, but protruding copper and burr copper are generated in an outer layer copper foil portion around the hole. In addition, the outer layer copper foil is irradiated with a laser through a hole previously formed by chemical etching or the like, and only the resin layer is processed to form a small-diameter hole (conformal mask method). Drilling by a laser with a weak output does not produce protruding copper or burr copper on the outer layer copper foil, but has a disadvantage that a large amount of smear is generated on the inner layer copper foil surface. For this reason, carbon dioxide laser processing is performed with an excessive output or irradiation number for the purpose of reducing the amount of smear, but in this case, protruding copper or burr copper of the outer layer copper foil portion around the hole is generated. Since the periphery of the hole becomes a base for copper plating in the next step, the quality of the hole affects the plating quality and is directly related to the reliability of the connection. Therefore, the quality of the periphery of the hole is important. In particular, protruding copper or burr copper on the surface copper foil around the hole hinders formation of a uniform plating layer, and causes a cavity that is inconvenient for forming a circuit. For this reason, conventionally, mechanical polishing or
Protruding copper and burr copper have been removed by a method of treating with an etchant (referred to as a SUEP method) disclosed in Japanese Patent Application Laid-Open No. 04-263488. However, with this type of conventional removal method, it is possible to reduce the thickness of copper for finer circuits, but it has been difficult to efficiently remove protruding copper and burr copper around the hole.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above problems by forming a small-diameter non-through hole in a multilayer copper-clad board.
It is an object of the present invention to provide a method of manufacturing a multilayer copper-clad board in which copper overhanging around the hole is efficiently removed, and a part of the outer layer copper foil is etched to make the copper thinner.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, they have found that they contain at least one of tetrazole and tetrazole derivatives and, if necessary, phenylurea. By using an etching solution consisting of hydrogen peroxide and sulfuric acid, the surface of the copper foil can be uniformly etched in a plane to reduce the thickness of the copper foil and efficiently remove the copper protruding around the small diameter holes. Heading, the present invention has been completed. That is, in a method of manufacturing a multilayer copper-clad board having two or more copper layers and a non-through hole, a non-through hole is formed in the multilayer copper-clad board, and then the copper projecting around the hole is replaced with hydrogen peroxide. 0.5 to 10% by weight, sulfuric acid 1 to 15% by weight, at least one of tetrazole and tetrazole derivative is 0.001 to 1%
% By weight, and optionally phenylurea 0.005 to 0.005%
The present invention relates to a method for producing a multilayer copper-clad board, which comprises removing using an aqueous solution containing 0.5% by weight.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The concentration of hydrogen peroxide in an etching solution used in the present invention is 0.5 to 10% by weight.
If it is less than 0.5% by weight, the substantial etching rate is insufficient, and if it exceeds 10% by weight, the etching rate is too fast to control.

The concentration of sulfuric acid is 1 to 15% by weight. If the sulfuric acid content is less than 1% by weight, it becomes difficult to etch the surface of the copper foil two-dimensionally and efficiently remove protruding copper, burr copper and the like around the small diameter hole. Also, the use of sulfuric acid in an amount of 15% by weight or more causes a decrease in the solubility of copper sulfate produced in the course of dissolving copper, and precipitates copper sulfate crystals.

The tetrazole and tetrazole derivative include 1H-tetrazole, 5-amino-1H-tetrazole, 5-amino-1-methyltetrazole, 1-methyltetrazole, 2-methyltetrazole, 5-methyl-1H-tetrazole, -Phenyltetrazole, 5-
Phenyl-1H-tetrazole is used. Especially 5-
Amino-1H-tetrazole (hereinafter simply referred to as aminotetrazole) is preferably used. The content of the tetrazole is 0.001 to 1% by weight, preferably 0.01 to 1%.
1% by weight.

[0008] The content of phenylurea used in the etching solution of the present invention is not particularly limited and may be appropriately selected depending on the circumstances, but is usually 0.005 to 1% by weight, preferably 0.01 to 0. 3% by weight. As the content increases, the stabilizing effect of hydrogen peroxide and the degree of elimination of processing unevenness increase, but under normal processing conditions, a content of up to 0.3% by weight is sufficient.

The etching solution of the present invention may be added separately to each of the above components so as to have the contents determined at the time of use, but may be mixed in advance. Therefore, it is convenient to prepare a concentrated solution and then dilute it with water so as to have the content specified in the present invention. As the water, ion-exchanged water is desirable.

The processing method for etching and removing protruding copper and burr copper generated on the outer layer copper foil around the holes of the copper-clad plate using the etching solution of the present invention is not particularly limited, but is not limited to spraying.
The treatment may be performed by an arbitrary method such as a spray method using an etching machine, a swing in an etching tank, and a dipping method by pump circulation. The etching rate is not particularly limited, but is generally 0.02 to 1.0 μm / sec. The thickness of the copper foil of the outer layer to be removed by etching is 3 to 7 μm, and the pressure of the spray or the like is also adjusted so as to remove protruding copper and burr copper at the same time. The temperature of the treatment is not particularly limited.
The treatment may be performed at 0 to 50 ° C, usually 25 to 40 ° C. Since the higher the processing temperature, the higher the etching rate, it may be set according to the purpose. As a guideline for removing the protruding copper and burr copper in the outer layer copper foil portion around the hole, the remaining thickness of the outer layer copper foil is usually 3 to 3 in consideration that it is etched at a higher etching rate than the outer layer copper foil. It is preferable to perform etching so that the thickness becomes 7 μm. After the protruding copper and burr copper in the outer layer copper foil around the hole are removed by etching, the surface of the outer layer copper foil can be smoothed or the thickness can be finely adjusted by using a known etching method.

[0011]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by the embodiments.

Examples 1 to 5 and Comparative Examples 1 to 3 In FIG. 1, non-through holes are formed in a copper clad board having two or more copper layers (12 μm thick) by a carbon dioxide laser using a laser sheet. In the method, a part of the copper foil on the surface of the perforated copper clad board is etched to make it thinner (5 μm
Thickness) and the step of etching and removing the protruding copper and burr copper of the outer layer copper foil around the hole. FIG. 1a is a sectional view of a copper-clad multilayer laminate. Non-through holes are formed in the multilayer laminate by a carbon dioxide gas laser as shown in FIG. 1b.
In order to establish conduction between the outer layer and the inner layer copper foil, the non-through hole is plated in a later step. However, in the state of FIG. The formation of a uniform plating layer is hindered, which causes an inconvenience in forming a circuit. Then, as shown in FIG. 1c, the circuit board after the drilling was immersed in an etching tank at a temperature of 35 ° C. using the chemicals shown in Table 1, and then rinsed with pure water and dried. Thereafter, the cross section of the periphery of the hole was observed with an optical microscope and a scanning electron microscope, and as shown in FIG. 1c, whether or not the protruding copper or burr copper around the hole was removed, and the outer layer copper foil was uniformly thin copper. It was observed whether or not it had been converted. As a comparative example, a chemical solution containing no tetrazole (Comparative Examples 1 to 3) was similarly treated and observed under a microscope. The observation results were evaluated according to the following criteria. The results are shown in Table 1. <Evaluation criteria> (Removability of protruding copper and burr copper) ：: Completely removed, ：: Partially remaining, ×:
Most remained (uniform thinning of outer layer copper foil) ：: Completely uniform, ：: Partial lack of uniformity, ×: Lack of uniformity

[0013]

[Table 1]

Example 6, Comparative Examples 4 and 5 The ability to form a fine pattern was evaluated. A four-layer laminate on which a 12-μm-thick copper foil is mounted is prepared by adding 2% by weight of hydrogen peroxide and 7% of sulfuric acid.
Using an etching solution comprising an aqueous solution containing 0.2% by weight of aminotetrazole and 0.2% by weight of phenylurea, removal of protruding copper and burr copper and etching of the outer layer copper foil by 7 μm by spray etching at 35 ° C. And thinned. Next, a copper pattern having a desired line and space (L (μm) / S (μm)) was formed on the outer layer copper foil portion, and a 15 μm copper plating was applied thereon to form a fine pattern. Various L (μm) / S (μ
20) Fine patterns each composed of m) were prepared, and whether or not lines were formed was determined by observation with an optical microscope and measurement of line conductivity. For comparison, Comparative Example 4 was treated with an etching solution containing propanol as an additive (2% by weight of hydrogen peroxide, 7% by weight of sulfuric acid and 2% by weight of propanol), and Comparative Example 5 was 12 μm without etching. The test was also performed when the thick outer copper foil was used as it was. The case where fine patterns were formed for all of the 20 samples was evaluated as ◎, and the case where the fine pattern was less than that was evaluated as ×, and the percentage of non-defective products is shown in parentheses. The results are shown in Table 2.

[0015]

[Table 2]

Example 7, Comparative Examples 6 and 7 The connection reliability was evaluated. As shown in FIG. 2, a continuous 1000-hole chain pattern was prepared and tested. That is,
A copper foil having a pattern for producing a continuous 1000-hole chain pattern on a copper foil having a thickness of 18 μm on the inner layer and a four-layer laminate having a copper foil having a thickness of 12 μm on the outer layer were prepared. Next, by using a laser sheet (manufactured by Mitsubishi Gas Chemical Company) to process the outer layer copper foil with a carbon dioxide gas laser, a blind via hole was formed in accordance with the pattern portion of the inner layer copper.
0 holes were drilled. Then, using an etching solution comprising an aqueous solution containing 2% by weight of hydrogen peroxide, 7% by weight of sulfuric acid, 0.2% by weight of aminotetrazole and 0.2% by weight of phenylurea, spray-etching is performed at 35 ° C. on the protruding copper or Removal of burr copper and etching removal of the outer layer copper foil by 7 μm were performed to reduce the thickness of copper. Next, after the smear inside the hole was removed by desmear treatment, the hole and the outer layer copper foil were plated with copper. After that, line and space 70 is applied to the outer copper foil.
A 1000-hole continuous chain pattern in which an outer layer and an inner layer copper pattern were continuously connected was prepared. With respect to the thus-prepared laminate having a continuous 1000-hole chain pattern, the operation of holding at −55 ° C. for 30 minutes and then holding at 125 ° C. for 30 minutes was repeated 1000 cycles, and the conduction resistance was measured. The connection reliability was evaluated based on whether or not the rate of change of the resistance value was less than ± 10%. For comparison, as Comparative Example 6, an etching solution containing propanol as an additive (2% by weight of hydrogen peroxide, 7% by weight of sulfuric acid)
And 2% by weight of propanol) and Comparative Example 7 in which the outer layer copper foil having a thickness of 12 μm was used without etching. The case where the rate of change of the resistance value was less than ± 10% was indicated by ◎, and the case where the rate of change was more than ± 10%. The results are shown in Table 3.

[0017]

[Table 3]

Example 8 A four-layer laminate was prepared by using, as an outer copper foil, a copper foil having a glossy surface of a copper foil subjected to a surface treatment having good energy absorption efficiency of a carbon dioxide laser as an outer copper foil. A printed circuit board with holes formed by irradiation with a carbon dioxide laser and a printed circuit board with holes formed by a conformal mask method using a carbon dioxide laser were evaluated. First, as Example 8, a four-layer laminate using a copper foil having a glossy surface of a copper foil having a surface treatment having good energy absorption efficiency of a carbon dioxide laser as an outer copper foil was irradiated with a carbon dioxide laser to form a hole. The printed circuit board having the opening was treated in the same manner with the etching solution used in Example 6 above, and then a fine pattern having a line and space of 30 μm and a continuous 1000-hole chain pattern were prepared. The connection reliability was evaluated. The method of displaying the test results of the ability to form a fine pattern and the connection reliability was performed in the same manner as in Tables 2 and 3 above. The results are shown in Table 4.

Example 9 and Comparative Examples 8, 9, and 10 FIG. 3 shows a process by a conformal mask method. As shown in FIG. 3A, a pattern for producing a 1000-hole continuous chain pattern is used as an inner layer. A four-layer laminate having the 18 μm-thick copper foil and having holes formed in the outer copper foil in advance by a chemical etching method or the like was prepared. Next, the resin layer up to the inner layer copper pattern was removed by irradiating a carbon dioxide gas laser through the hole of the outer layer copper foil (FIG. 3B). 4 shown in FIG.
The layered laminate was subjected to carbon dioxide laser processing with an excessive number of irradiations to remove most of the smear (FIG. 3c). However, protruding copper was generated in the peripheral portion of the outer layer copper foil due to the excessive irradiation of the carbon dioxide gas laser. This four-layer laminate was similarly treated with the etching solution used in Example 6 above,
Next, a 30 μm line-and-space fine pattern and a 1000-hole continuous chain pattern were prepared, and the ability to form the fine pattern and the connection reliability were evaluated. As a comparative example 8 for comparison, a copper foil having a glossy surface subjected to a surface treatment having good energy absorption efficiency of a carbon dioxide laser and a blind via hole formed by a carbon dioxide laser method was etched with propanol as an additive. The test was carried out with a liquid (2% by weight of hydrogen peroxide, 7% by weight of sulfuric acid and 2% by weight of propanol). Comparative Example 9 shows an etching solution containing propanol as an additive (2% by weight of hydrogen peroxide, 7% by weight of sulfuric acid, and 2% by weight of propanol 2) for a four-layer laminate (FIG. 3C).
% By weight). Comparative example
As No. 10, the four-layer laminate having the blind via holes shown in FIG. 3B was treated in the same manner with the same etchant as in Example 6, and then the fine pattern formation ability and connection reliability were evaluated. The method of displaying the test results of the fine pattern forming ability and connection reliability (1000 cycles) was the same as in Tables 2 and 3 above. The results are shown in Table 4.

[0020]

[Table 4]

[0021]

According to the present invention, in the non-through hole made by the carbon dioxide laser, the protruding copper or burr copper generated in the outer layer copper foil portion around the hole, which has been conventionally difficult, can be easily removed by using the etching solution of the present invention. Can be removed,
It has become possible to significantly improve the conduction characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention in which a copper-clad board according to an embodiment of the present invention efficiently removes protruding copper and burr copper generated in an outer layer copper foil portion around a non-through hole, and at the same time, a part of a surface copper foil. FIG. 3 is a view showing a step of thinning copper by etching also, a: preparation of a multilayer copper-clad board, b: drilling, c: removal of protruding copper and burr copper generated on the surface copper foil portion around the hole and outer layer. Each step of partial etching in the thickness direction of the copper foil and d: conducting the conduction between the outer copper foil and the inner copper foil through the small-diameter hole by copper plating are shown.

FIG. 2 is a sectional view showing connection of a 1000-hole continuous chain pattern.

FIG. 3 is a cross-sectional view showing a step of forming a hole by a conformal mask method, wherein a: a four-layer laminate in which holes are formed in an outer copper foil in advance by an etching method, b: a hole formed by laser irradiation;
c: Each step of drilling by excessive laser irradiation is shown.

[Explanation of symbols]

 Reference Signs List 1 outer layer copper foil 1a thinner outer layer copper foil 2 inner layer copper foil 3 non-through hole 3 'hole drilled by chemical etching 4 protruding copper, burr copper 5 insulating resin layer 6 etching solution of the present invention 7 copper 8 smear L laser irradiation

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05K 3/42 610 H05K 3/42 610A (72) Inventor Ryuji Soga Red 22 Wadai, Tsukuba, Ibaraki Pref. Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Fukusaburo Ishihara 1-2-18, Iwamotocho, Chiyoda-ku, Tokyo Ryoko Chemical Co., Ltd. (72) Inventor Toshimitsu Kawamura 1-2-18, Iwamotocho, Chiyoda-ku, Tokyo Ryuji 4K057 WA11 WB04 WE03 WE25 WF01 WN01 5E317 AA24 BB01 BB12 CC53 CD01 CD32 GG11 5E343 AA07 BB24 BB67 DD76 EE02 EE13 GG13 5E346 AA43 CC32 CC58 DD12 FF03 GG15 GG22

Claims (3)

[Claims] 1. A method for producing a multilayer copper-clad board having two or more copper layers and a non-through hole, comprising the steps of: forming a non-through hole in the multilayer copper-clad board; 0.5 to 10% by weight of hydrogen peroxide, 1 to 15% by weight of sulfuric acid, 0.001 to 1% by weight of at least one of tetrazole and tetrazole derivatives, and 0.005 to 0% of phenylurea as required. A method for producing a multilayer copper-clad board, comprising removing using an aqueous solution containing 0.5% by weight. 2. The method of claim 1, wherein the tetrazole and the tetrazole derivative are 1H-tetrazole, 5-amino-1H-tetrazole, 5-amino-1-methyltetrazole, 1-methyltetrazole, 2-methyltetrazole, 5-methyl-
The method for producing a multilayer copper-clad board according to claim 1, which is 1H-tetrazole, 1-phenyltetrazole, or 5-phenyl-1H-tetrazole. 3. The method for producing a multilayer copper-clad board according to claim 1, wherein said non-through holes are formed by a carbon dioxide gas laser.