JPH04259356A - Manufacture of aluminum foil for printed circuit - Google Patents

Abstract

PURPOSE:To offer a method for manufacturing aluminum foil for a printed circuit in which sharp etching is capable and a printed circuit having high density can be manufactured. CONSTITUTION:An aluminum ingot having >=99.85% purity is prepd. This aluminum ingot is subjected to hot rolling and cold rolling. The aluminum sheet before the cold rolling after the hot rolling or in the process of the cold rolling is subjected to process annealing. As for the conditions of the process annealing, it is heated at >=0.1 deg.C/sec temp. rising rate and is held at 350 to 600 deg.C for 1 to 600sec. With obviated process annealing or in addition to the process annealing, final annealing is executed to the aluminum foil after the cold rolling. The conditions of the final annealing lie in the temp. and time in the range shown by the hatched line in the figure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of manufacturing aluminum foil for use in making printed circuits for printed circuit boards.

0002

2. Description of the Related Art Printed circuit boards are used in electrical and electronic equipment. This printed circuit board is manufactured by the following manufacturing method. That is, a photosensitive resin is applied to the surface of the aluminum foil of a laminated product in which aluminum foil is bonded to a substrate such as a synthetic resin sheet, and the photosensitive resin is exposed to light so as to form a predetermined circuit pattern. Then, the photosensitive resin outside the circuit pattern is removed. The aluminum foil is exposed in the areas where the photosensitive resin has been removed. This exposed aluminum foil portion is dissolved by etching. In this way, a printed circuit is formed by the portions of the aluminum foil that are not melted away.

[0003] Conventionally, as aluminum foil for forming printed circuits, JIS H 4160 IN30
Chemical composition defined by (Si+Fe=0.7% or less, C
u=0.1% or less, Mn=0.05% or less, Mg=0.
0.05% or less, Zn=0.05% or less, Al=99.30
% or more, and other unavoidable impurities. However, all percentages are by weight. ) are used. Alloys specified by JIS H 4160 IN30 have excellent rollability and mechanical properties such as bending resistance. Therefore, it is possible to obtain an aluminum foil having excellent bending resistance even if the thickness is, for example, about 6 μm. When aluminum foil, which is thin and has excellent bending resistance, is used for printed circuits, the amount of dissolution during etching can be reduced, and even when used as a flexible printed circuit board, it is possible to reduce the amount of dissolution during etching. This is preferable because it can prevent breakage.

[0004] In recent years, with the miniaturization of electrical equipment and the like, printed circuits themselves have also become smaller and printed circuit patterns have become more dense. That is, the width of the circuit lines themselves has become narrower, and the intervals between the circuit lines have become narrower. In order to form such circuit lines, sharp etching must be performed. Sharp etching means that the edges of the circuit lines form smooth lines, in other words, the edges of the circuit lines are not jagged, and there are no partial protrusions on the edges of the circuit lines. There should be no concavities or recesses. If sharp etching is not possible, the jagged edge of the circuit line may be close to the adjacent circuit line, causing a short circuit, or the edge of the circuit line may have a recessed area. , the circuit will be disconnected and power will no longer be able to flow.

[0005]

[Problems to be Solved by the Invention] However, it has been difficult to perform sharp etching on the aluminum foil specified by JIS H 4160 IN30, which has been used in the past. This is because coarse crystal precipitates are present in the aluminum foil, and etching is concentrated on these areas, resulting in unevenness at the edges of the circuit lines.

[0006] For this reason, the applicant of the present case filed the patent application No. 2-41
In No. 4626, by regulating the aluminum purity in aluminum foil, the number of coarse crystal precipitates is reduced, and when etching is performed, sharp etching is possible, which prevents short circuits or inability to conduct electricity. We have proposed an aluminum foil that can produce printed circuits that are less prone to damage.

The aluminum foil proposed in Japanese Patent Application No. 2-414626 is manufactured by subjecting an aluminum ingot of a predetermined purity to homogenization treatment, hot rolling, and cold rolling. Then, intermediate annealing may be performed to improve rolling properties, or final annealing may be performed to remove rolling oil adhering to the surface of the aluminum foil or to improve the flexibility of the aluminum foil. However, if intermediate annealing or final annealing is performed carelessly, coarse crystal precipitates are formed in the aluminum foil, making it difficult to perform sharp etching, which may result in the above-mentioned drawbacks.

Therefore, the present invention suppresses the generation of coarse crystal precipitates and enables sharp etching by performing intermediate annealing and/or final annealing under certain specific conditions.
The present invention aims to provide an aluminum foil that can be suitably used for printed circuits.

[0009]

[Means for Solving the Problems] That is, the present invention has a purity of 9
In a method for producing aluminum foil for printed circuits by subjecting an aluminum ingot of 9.85% by weight or more to hot rolling and cold rolling, after hot rolling and before cold rolling, or during cold rolling. An aluminum plate was heated at a heating rate of 0.
Heating at a rate of 1°C/sec or more, at a temperature of 350°C to 600°C,
It is characterized by performing intermediate annealing by holding the aluminum foil for 600 seconds, and/or performing final annealing on the aluminum foil after cold rolling at a temperature and time condition within the shaded range in FIG. The present invention relates to a method for producing aluminum foil for printed circuits.

First, in the present invention, an aluminum ingot having a purity of 99.85% by weight or more is prepared. If the purity of the aluminum ingot is less than 99.85% by weight, the amount of impurities will be relatively large, the number of coarse crystal precipitates will increase in the obtained aluminum foil, and sharp etching will not be possible, so it is preferable. do not have.

[0011] This aluminum ingot is subjected to facing treatment and homogenization treatment, if desired. Then, hot rolling and cold rolling are performed. The facing, homogenization treatment, hot rolling, and cold rolling may be performed by conventionally known methods.

[0012] At this time, in order to improve the rolling properties of the aluminum plate, intermediate annealing is generally performed after hot rolling and before cold rolling. Further, in order to improve the rollability of the aluminum plate during cold rolling, intermediate annealing is generally performed. This intermediate annealing must be performed under the following conditions. That is, first, the temperature increase rate is set to 0.1° C./second or more. If the heating rate is less than 0.1° C./sec, it will take a long time to reach a predetermined temperature, and impurities in the aluminum will precipitate during heating, increasing the number of coarse crystal precipitates. Therefore, a large number of coarse crystal precipitates are present in the obtained aluminum foil, making it impossible to perform sharp etching, which is not preferable. In addition, the holding temperature for intermediate annealing is 3
Must be between 50 and 500°C. Hold temperature at 35
If the temperature is lower than 0°C, it will take a long time for the aluminum plate to soften, impurities will precipitate during that time, and the number of coarse crystal precipitates will increase. Therefore, a large number of coarse crystal precipitates are present in the obtained aluminum foil, making it impossible to perform sharp etching, which is not preferable. On the other hand, if the holding temperature during intermediate annealing exceeds 500°C, the oxide film on the surface of the aluminum plate will become thicker, the rolling oil will be baked on, the surface will change color, or blisters will occur, causing the resulting aluminum foil to deteriorate. The electrical properties of the material deteriorate, making it unsuitable for use in printed circuits. Furthermore, the holding time of intermediate annealing is 1 to 600.
Must be seconds. If the holding time is less than 1 second, the aluminum plate will not be sufficiently softened and rolling properties will not be improved, which is not preferable. On the other hand, if the holding time exceeds 600 seconds, impurities in the aluminum plate will coarsely precipitate. Therefore, a large number of coarse crystal precipitates are present in the obtained aluminum foil, making it impossible to perform sharp etching, which is not preferable.

After cold rolling, final annealing is generally performed to remove rolling oil adhering to the surface of the aluminum foil or to improve the flexibility of the aluminum foil. The final annealing must be performed at a temperature and time within the shaded range in FIG. If the temperature is less than 200°C, it is not preferable because the rolling oil, which is the purpose of final annealing, cannot be sufficiently removed. On the contrary, the temperature is 500℃
If it exceeds this value, even if the final annealing is performed in a vacuum atmosphere or an inert gas atmosphere, the rolling oil will seize and discolor the surface, or the electrical properties of the resulting aluminum foil will deteriorate, which is not preferable. Furthermore, if the temperature exceeds 500° C., when final annealing is performed in a coiled state, the aluminum foils will adhere to each other and cannot be unwound normally, which is not preferable. Furthermore, the holding time of the final annealing must be between the time delineated by line a and line b in FIG. If the time is less than the time indicated by line a, rolling oil may not be removed sufficiently or it may become difficult to impart flexibility to the aluminum foil, which is not preferable. Further, if the time is longer than the time indicated by line b, impurities will precipitate in the resulting aluminum foil, the number of coarse crystal precipitates will increase, and sharp etching will not be possible, which is not preferable. Note that the holding time for final annealing does not include the time during heating and cooling.

The aluminum foil obtained as described above can be suitably used when producing a printed circuit board by a conventionally known method.

[0015]

[Example] Examples 1 to 3, Comparative Examples 1 and 2 First, an aluminum ingot (thickness 60 mm x width 18
0 mm x length 180 mm) was prepared.

[Table 1] After face cutting both sides of this aluminum ingot by 5 mm each (thickness: 50 mm), homogenization treatment was performed at 600° C. for 12 hours. After that, this ingot was hot rolled to a thickness of 3 mm.
aluminum plate. Subsequently, this aluminum plate was cold-rolled to a thickness of 0.8 mm, and then heated in an atmospheric furnace at a temperature increase rate of about 0.4°C/sec, and heated to 400°C for 30 minutes.
Intermediate annealing was performed by holding for 00 seconds. Further, the aluminum foil was then cold rolled to obtain a 20 μm thick aluminum foil, which was then final annealed at 400° C. for 12 hours to obtain an aluminum foil for printed circuits.

[0016] This printed circuit aluminum foil and a polyester film (thickness: 50 μm) were bonded together using a urethane adhesive. Note that the thickness of the adhesive layer was 5 μm. A circuit was printed on the aluminum foil surface of this laminate by photolithography and etched using an 85% H3PO4 solution at 60°C. The circuit pattern is striped, with a circuit line width of 0.5 mm and an interval between adjacent circuit lines of 0.5 mm.
And so. Then, it was checked whether there were any irregularities on the edge of the circuit line, that is, whether the edge of the circuit line was chipped or whether there were any bumps. The results are referred to as pattern etching properties, and those with almost no unevenness were evaluated as ○, those with some unevenness were evaluated as Δ, and those with many unevenness were evaluated as ×, and are shown in Table 2.

[Table 2] As is clear from Table 2, when the aluminum foils for printed circuits obtained by the methods according to Examples 1 to 3 were used,
It had excellent pattern etching properties. On the other hand, in the case of the aluminum foils obtained by the methods according to Comparative Examples 1 and 2, the pattern etching properties were poor.

Examples 4 to 11 and Comparative Examples 3 to 7 Aluminum foils for printed circuits were obtained in the same manner as in Example 1, except that the intermediate annealing conditions were as shown in Table 3. In addition, only in Example 4, intermediate annealing was performed in a salt bath.

[Table 3] The surface properties and tensile strength of the aluminum plate after intermediate annealing were evaluated and measured, and the results are shown in Table 4. Furthermore, the pattern etching properties of the aluminum foils for printed circuits obtained after the final annealing were evaluated in the same manner as in Example 1, and the results are also shown in Table 4.

[Table 4] As is clear from Table 4, the aluminum plates obtained by the methods according to Examples 4 to 11 had no abnormality in surface texture and had decreased tensile strength, so that sufficient softening occurred. It can be seen that it has excellent flexibility and improved rolling properties. Moreover, the aluminum foil for printed circuits after final annealing also had excellent pattern etching properties. On the other hand, the aluminum plates obtained by the methods according to Comparative Examples 3 and 4 did not have a sufficient reduction in tensile strength, were not sufficiently softened, had poor flexibility, and had poor rolling properties. Furthermore, the aluminum foils obtained by the methods according to Comparative Examples 5 and 7 had poor pattern etching properties. Furthermore, since discoloration and blisters occurred on the surface of the aluminum plate obtained by the method according to Comparative Example 6, the production of aluminum foil was discontinued without performing subsequent steps.

Examples 12 to 17 and Comparative Examples 8 to 15 Example 1 except that the final annealing conditions were as shown in Table 5.
An aluminum foil for printed circuits was obtained in the same manner as above. In addition,
Those whose temperature was 500°C or higher were subjected to final annealing in argon gas, and those whose temperature was less than 500°C were subjected to final annealing in the atmosphere.

[Table 5] The surface properties and tensile strength of the obtained aluminum foil for printed circuits were evaluated and measured, and the results are shown in Table 6. Further, pattern etching properties were evaluated in the same manner as in Example 1, and the results are shown in Table 6. Furthermore, the adhesiveness between the obtained aluminum foil for printed circuits and the polyester film was evaluated by the following evaluation method. In other words, those with excellent adhesive strength are marked as ○, those with slightly poorer adhesive strength are marked as △, and those with poorer adhesive strength are marked as ×.
And so. The results are also shown in Table 6.

[Table 6] As is clear from Table 6, the aluminum foils for printed circuits obtained by the methods of Examples 12 to 17 had no abnormalities in surface properties, had excellent adhesive properties, and had good pattern etching properties. It was excellent. On the other hand, in the aluminum foils obtained by the methods of Comparative Examples 8, 9, 11, and 13, the rolling oil on the surface was not sufficiently removed, and the adhesiveness with the polyester film was poor. In particular, Comparative Examples 8 and 9
The aluminum foil obtained by the method described above had poor adhesion, so it was impossible to evaluate pattern etching properties. Furthermore, the aluminum foils obtained by the methods according to Comparative Examples 10, 12, and 14 had poor pattern etching properties. Furthermore, in the method according to Comparative Example 15, other performance evaluations were not possible due to the aluminum foils sticking together.

[0019]

[Effects of the Invention] As explained above, if a printed circuit is made using the aluminum foil for printed circuits obtained by the method according to the present invention, sharp edges can be obtained because the aluminum foil has excellent etching properties. You can create circuit lines with edges. Therefore, even if a circuit is created using a high-density printed pattern, adjacent circuit lines are unlikely to come into contact with each other, and short circuits can be prevented. In addition, since the aluminum foil for printed circuits obtained by the method according to the present invention can produce circuit lines with sharp edges, chipped recesses are less likely to occur at the edges of the circuit lines, and wire breaks are less likely to occur. Also plays.

[Brief explanation of the drawing]

FIG. 1 shows conditions for final annealing in the present invention.

Claims (3)

[Claims] Claim 1. A method for producing aluminum foil for printed circuits by hot rolling and cold rolling an aluminum ingot having a purity of 99.85% by weight or more, wherein after hot rolling and before cold rolling, Or a printed circuit characterized by performing intermediate annealing by heating an aluminum plate during cold rolling at a temperature increase rate of 0.1° C./sec or more and holding it at a temperature of 350 to 600° C. for 1 to 600 seconds. Method of manufacturing aluminum foil for use in aluminum foil. 2. A method for producing aluminum foil for printed circuits by subjecting an aluminum ingot having a purity of 99.85% by weight or more to hot rolling and cold rolling, in which the aluminum foil after cold rolling has the following characteristics: 1. A method for producing aluminum foil for printed circuits, characterized in that final annealing is performed under temperature and time conditions within the shaded range of 1. 3. A method for producing aluminum foil for printed circuits by subjecting an aluminum ingot having a purity of 99.85% by weight or more to hot rolling and cold rolling, wherein: after hot rolling and before cold rolling, Alternatively, the aluminum plate during cold rolling is heated at a temperature increase rate of 0.1°C/sec or more and held at a temperature of 350 to 600°C for 1 to 600 seconds to perform intermediate annealing, and after the cold rolling is completed, 1. A method for producing aluminum foil for printed circuits, which comprises subjecting aluminum foil to final annealing at a temperature and time within the shaded range of FIG.