JPH0639143B2 - Method for correcting curl and improving dimensional stability of flexible metal foil laminates - Google Patents

Description

[0001] TECHNICAL FIELD The present invention relates to a method for straightening curl and improving dimensional stability of a long flexible metal clad laminate (hereinafter referred to as FMCL) made of a polyimide metal clad sheet, which has excellent heat resistance, electrical properties, and mechanical properties. More specifically, the present invention relates to a method for straightening curl and improving dimensional stability of a long flexible metal clad laminate (hereinafter referred to as FMCL) made of a polyimide metal clad sheet, which is manufactured by forming a thin film layer made of an aromatic polyimide on a metal foil.
This invention relates to a method for continuously correcting curl that occurs in a polyimide thin film laminate (hereinafter referred to as A-FMCL) and minimizing the dimensional shrinkage of the polyimide thin film layer that occurs when etching the metal foil.

BACKGROUND ART Flexible metal foil laminates are substrates for manufacturing flexible printed circuits, and their use has increased in recent years due to the trend toward more compact cases for housing printed circuits. Such flexible metal foil laminates have traditionally been manufactured by laminating a polyimide film to a metal foil using an adhesive. While the polyimide film in these laminates has excellent heat resistance, electrical properties, and mechanical properties, the adhesive's properties are insufficient, preventing the full utilization of the polyimide film's properties.

Therefore, methods for producing A-FMCL in which a polyimide thin film and a metal foil are directly laminated without an adhesive layer have been studied. For example, U.S. Pat. No. 3,177,437 is disclosed.
No. 9,634, JP-A-49-129,862, JP-A-58-190,091,
These methods are simple in their manufacturing process and do not require the provision of an adhesive layer, so that the properties of the resulting A-FMCL reflect the excellent properties of the polyimide used, and also have the advantage that there is little deterioration in adhesion to the metal foil even at high temperatures.

However, the A-FMCL manufactured in this manner, which does not have an adhesive layer, has the drawback of curling, which is extremely detrimental to circuit formation. This curling occurs due to the difference in dimensions between the polyimide layer and the metal foil, which is caused by volume shrinkage that inevitably occurs during the laminate manufacturing process on the polyimide layer side. Generally, the laminate has an appearance similar to a rolled-up carpet, with the metal foil facing outward, as shown in Figure 4. A laminate that has curled in this way:
One drawback of flexible metal foil laminates is that the dimensional shrinkage (IPC FC 240 method) of the polyimide foil that occurs during etching of the metal foil is extremely large, at about 0.3 to 1.0%. This curling and shrinkage are serious drawbacks of flexible metal foil laminates, making them difficult to handle in processes such as screen printing and chemical etching. They can also damage the resist and cause breaks or short circuits in the conductors, making circuit processing difficult.

Therefore, it is possible to prevent the occurrence of such curling or reduce the curling that has occurred, and to provide flatness that does not interfere with circuit processing.
Various improvements have been proposed to achieve dimensional stability of polyimide film with dimensional shrinkage of 0.1% or less.

For example, the volume shrinkage due to the ring-closure reaction of polyamic acid, the precursor of polyimide, can be eliminated by casting a solvent-soluble aromatic polyimide onto a metal foil. However, even with this method, problems still remain, such as curling due to evaporation of the solvent and differences in the linear expansion coefficients of the polyimide and the metal foil, and dimensional shrinkage of the polyimide during etching of the metal foil.

On the other hand, methods for correcting curls that have already occurred are also known. For example, see JP-A-54-66966 and JP-A-54-108272.
These methods include Patent Nos. 55-72,095, 55-160,489, and 56-23,791. However, these methods require high-temperature and long-term heat treatment, and are therefore unsuitable for correcting curls that occur in long A-FMCL.

In response to this, methods for straightening the curl of a long A-FMCL are also known. For example, JP-A-54-31480 discloses such methods. However, in these methods, high temperatures near the glass transition temperature or
The stretching or rolling is carried out under temperature conditions that soften the resin layer, such as heating to a temperature of at least 100°C while the solvent remains. Therefore, due to the difference in the linear expansion coefficient between the resin thin film layer and the metal foil or the complete removal of the remaining solvent, curling tends to occur again after the curl correction treatment. In addition, in JP-A-59-22,389, the curl correction treatment is carried out at a low temperature of 80°C or less without using a solvent, so it is suitable for long substrates and does not cause curling to occur again after the curl correction treatment. However, this method is not suitable for substrates with a curvature radius of 0.5 to 25 mm.
The long substrate is placed on the curved surface of a bar with a large curve, with the metal foil facing inward, and a very weak tension, usually 10 to 200 g/cm, is applied to the bar while sliding it in the longitudinal direction of the substrate, and the slight plastic deformation that occurs in the metal foil is used to straighten the curl.

According to this method, the metal foil undergoes slight plastic deformation, but the resin thin film layer undergoes almost no plastic deformation. Therefore, curl correction is achieved only by flattening the metal foil using the slight plastic deformation, and residual shrinkage stress due to volumetric shrinkage remains in the resin thin film layer. Therefore, when the metal foil of the substrate is etched to form a circuit and the metal foil that stretched the resin thin film layer is removed, the resin thin film layer in that area tends to shrink significantly due to the residual shrinkage stress, while the resin thin film layer bonded to the circuit portion of the metal foil does not shrink. As a result, numerous wrinkles, irregularities, etc. appear on the circuit board as a whole, which causes significant difficulties in handling the circuit board in processes subsequent to the etching process, such as the overlay process, solder resist process, and component mounting process.

DISCLOSURE OF THE INVENTION The present invention provides a method for effectively and continuously correcting and alleviating the problems of curling that occurs in a long A-FMCL manufactured by forming a thin layer of aromatic polyimide directly on a metal foil, and dimensional shrinkage of the polyimide thin layer that occurs when the metal foil is etched.

The above object can be achieved by the following method: A long A-FMCL having an aromatic polyimide thin film formed directly on a long metal foil without using an adhesive,
A first step involves sliding the metal foil in a tensile state in the longitudinal direction on the curved surface of a first bar provided at an angle (line angle) of 30 to 60 degrees relative to the width direction of the first bar, with the metal foil facing inward; a second step involves sliding the metal foil in a tensile state on the curved surface of a second bar provided at an angle (line angle) of 60 to 120 degrees relative to the first bar;
a second step of sliding the laminate in a tensile state in the longitudinal direction over the curved surface of a bar with the metal foil facing inward; a third step of sliding the laminate in a tensile state in the longitudinal direction over the curved surface of a third bar (or a first rotating roll for smoother sliding) that is provided at an angle (line angle) of 30 to 60 degrees relative to the width direction of the laminate, with the imide thin film facing inward; and a fourth step of sliding the laminate in a tensile state in the longitudinal direction over the curved surface of a fourth bar or a second rotating roll that is provided at an angle (line angle) of 60 to 120 degrees relative to the third bar (or the first rotating roll for smoother sliding).
A method for straightening curl and improving dimensional stability of A-FMCL, characterized by carrying out each step one or more times in any order.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 and 2 are schematic diagrams showing the implementation of curl correction and dimensional stability improvement of A-FMCL according to the present invention; Figure 3 is a schematic diagram showing, in cross section of the roll, a method for preventing the rotating roll in Figure 1 from being distorted by the tension applied to the long substrate; Figure 4 is a schematic diagram showing the appearance of a curled A-FMCL; Figure 5 is a schematic diagram of a laminate moving on the curved surface of a bar having a curved surface a, with the polyimide layer on the outside and the metal foil layer on the inside, while being subjected to tension; Figure 6 is a schematic diagram showing the direction in which dimensional shrinkage decreases as the laminate moves between the first bar and the second bar; and Figures 7 and 8 are schematic diagrams of cross sections perpendicular to the longitudinal direction of the bar used in the process of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the first to fourth steps can be carried out in any order. In a preferred embodiment of the present invention, the steps are carried out in the order of the first step, the second step, the third step, the fourth step, and the fourth step.
The method may be a method in which the steps are performed in an order in which each step is performed one or more times, or a method in which the steps are performed in an order of first step, third step, second step, and fourth step, and each step is performed one or more times.
However, in addition to the above-described order of steps, many other orders are applicable, such as the order of step 1, step 2, step 3, step 4; step 1, step 3, step 2, step 1, step 4, step 3, step 4, step 3, or the order of step 1, step 2, step 1, step 2, step 3, step 4.

More preferably, after the final step, 100
The step of curing the product in an atmosphere of 100°C or higher for 30 minutes or more is carried out.

The fundamental technical idea of the present invention is that when a laminate A moves circumferentially over a curved surface a of a bar b having a specific radius of curvature, with the polyimide layer c on the outside and the metal foil d on the inside, under tension, the elongation of the outer polyimide layer c is made sufficiently greater than the elongation of the inner metal foil d, thereby imparting permanent plastic deformation to the polyimide layer c. The amount of deformation is made greater than the plastic deformation of the metal foil d, so that the planar length of the polyimide layer c is made approximately equal to the length of the metal foil d, thereby reducing the dimensional shrinkage of the laminate.

Furthermore, to implement this technical concept, it is necessary to separate the process into a first step and a second step, as illustrated in Figure 6. In the first step, when laminate A passes over a first bar positioned at a 45° angle to its direction of travel, dimensional shrinkage decreases perpendicular to the bar. Furthermore, in the second step, when laminate A passes over a second bar positioned at a -45° angle to its direction of travel, dimensional shrinkage decreases perpendicular to the bar. In this way, as laminate A passes over both the first and second bars, dimensional shrinkage in all plane directions of the laminate is reduced. The degree of this reduction in dimensional shrinkage can be adjusted by controlling the tension, speed, and number of times laminate A slides over the bar in the direction of travel, the tension applied to laminate A (as shown in Figure 5), and the folding angle when laminate A is folded around the bar.

However, the first and second steps only have the effect of making the dimensions of the polyimide layer and the metal foil layer approximately equal, and the plastic deformation remaining in the metal foil causes curling opposite to the intended curl, with the metal foil facing inward. Therefore, by further performing the third and fourth steps, it is possible to achieve the following without causing any permanent plastic deformation in the polyimide layer:
The reverse curl can be corrected by causing a weak plastic deformation in the metal foil, and the foil can be flattened. The degree of correction of the reverse curl can be adjusted in the same manner as the correction of the initial curl.

Furthermore, after correcting the curl and reducing the dimensional shrinkage by using the above-mentioned plastic deformation as necessary, the laminate is heated at about 100°C.
It is preferable to cure at the above temperature, and the principle of this technology is to remove small temporary deformations other than those caused by the stretching of the polyimide when the bar passes through. In this way, curl correction and reduction of dimensional shrinkage of A-FMCL (hereinafter referred to as dimensional stability improvement) can be achieved.

Furthermore, even in the case of curl correction, which involves plastic deformation, there is substantially no deterioration in the adhesive properties and film properties of A-FMCL.

In the present invention, the aromatic polyimide of the thin film layer formed on the metal foil is a polymer obtained from an aromatic tetracarboxylic dianhydride and an aromatic diamine, and is not particularly limited. Among these polyimides, a particularly suitable polyimide is a polyimide obtained by mixing a symmetrical aromatic meta-substituted primary diamine (hereinafter abbreviated as m-diamine) and a symmetrical aromatic para-substituted primary diamine (hereinafter abbreviated as paradiamine) in an equivalent ratio of 10.
The polymer is obtained by mixing pyromellitic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride in a ratio of 1:60:90:40 and then reacting the mixture with an aromatic tetracarboxylic dianhydride. Also suitable are polymers obtained from pyromellitic dianhydride having a repeating unit represented by the following general formula (I) or (IV) and an aromatic diamine, polymers obtained from 3,3',4,4'-benzophenonetetracarboxylic dianhydride having a repeating unit represented by the following general formula (II) or (V) and an aromatic diamine, and polymers obtained from 3,3',4,4'-biphenyltetracarboxylic dianhydride having a repeating unit represented by the following general formula (III) or (VI) and an aromatic diamine.

(In the above general formula, X is O.SO ₂ .S.CO.C
Examples _of aromatic _diamines represented _{by the} above general formula include _:
4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenylmethane,
Examples include 3,3'-diaminodiphenyl ether and 3,3'-diaminodiphenyl sulfone.
The aromatic polyimide does not have to be a single one, but may be a mixture of two or more kinds.

The m-diamine can be represented by the following general formula:

[In the above general formula, X is O, SO ₂ , SO , S, CO,
X is CH ₂ , C(CH ₃ ) ₂ , C(CF ₃ ) ₂ or a direct bond, and each X may be the same or different.] Examples of m-diamines represented by the above general formula include 3,
3'-Diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, bis[4-
(3-aminophenoxy)phenyl]methane, 2,2-
Bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]
sulfide, bis[4-(3-aminophenoxy)phenyl]sulfoxide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, 4,4'-bis(3-aminophenylsulfonyl)diphenyl ether, 4,
4'-bis(3-aminothiophenoxy)diphenyl sulfone, 1,4-bis[4-(3-aminophenoxy)
These may be used alone or in combination of two or more.

The p-diamine used in combination with the m-diamine can be represented by the following general formula:

[In the above general formula, X is O, SO ₂ , SO, S, CO, C
H ₂ , C(CH ₃ ) ₂ or C(CF ₃ ) ₂ , and each X may be the same or different.] Examples of P-diamines represented by the above general formula include 4,
4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, bis[4-(4
-aminophenoxy)phenyl]methane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane,
2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene,
4,4'-bis(4-aminophenoxy)biphenyl,
Bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]ether, 4,4'-bis(4-aminophenylsulfonyl)diphenyl ether, 4,
4'-bis(4-aminothiophenoxy)diphenyl sulfone, 1,4-bis[4-(4-aminophenoxy)
These may be used alone or in combination of two or more.

The aromatic tetracarboxylic acid anhydride to be reacted with the diamine includes pyromellitic dianhydride, 3,3',4,4'-
Benzophenonetetracarboxylic dianhydride, 2,2',
3,3'-benzophenonetetracarboxylic dianhydride,
3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-
carboxyphenyl) ether dianhydride, bis(3,4
-dicarboxyphenyl)sulfone dianhydride, 1,1-
Examples of suitable dianhydrides include bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, and 1,2,7,8-phenanthrenetetracarboxylic dianhydride. These may be used alone or in combination of two or more.

Furthermore, in order to form an aromatic polyimide thin film layer directly on a long metal foil without an adhesive layer therebetween to obtain an A-FMCL, which is the subject of the present invention, the following methods can be employed, but the method is not particularly limited to these.

1) Polyamic acid, a precursor of polyimide produced by reacting aromatic diamine with aromatic tetracarboxylic dianhydride, is dissolved in an organic solvent and the solution is directly coated onto a metal foil. The film is then heated, the solvent is removed, and the water generated by the ring-closing reaction of the polyamic acid is dehydrated to form the film.

2) Aromatic diamine and aromatic tetracarboxylic dianhydride are reacted in a known solvent such as a phenolic solvent to produce a solution in which polyimide is dissolved. This solution is then directly coated onto a metal foil, and the foil is then heated and desolvated to form the film.

The above heating, dehydration or heating and desolvation is usually performed in the range of 150 to 400°C.
The aromatic polyimide layer formed usually has a thickness of 10 to 100 μm. Alternatively, a laminate can be formed by directly thermocompressing a thermoplastic polyimide film onto a metal foil.

The long metal foil used in the present invention is generally a copper foil or an aluminum foil, but other conductive metal foils such as a nickel foil can also be used. The thickness of the foil is as follows:
Usually, 10 to 100 μm is used.

The long A-FMCL produced as described above by directly forming a thin layer of aromatic polyimide on a long metal foil without an adhesive layer has the following properties in both the longitudinal and transverse directions:
There is a strong curl with the metal foil side facing outwards.
When the metal foil of A-FMCL is etched, the polyimide thin film layer undergoes significant dimensional shrinkage.

In order to facilitate understanding of the present invention, the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an example of a process for straightening and improving dimensional stability, in which a polyimide film is stretched to a greater extent than a metal foil using rectangular glass plates having curved corners in cross section as shown in FIG. 8 as the first and second bars, and then reverse curling, with the metal foil surface facing inward, is corrected by the first and second rotating rolls.

The A-FMCL7 wound on the roll 1 moves in the direction of the arrow, and is angled 30 to 60 degrees, preferably 40 degrees, with respect to the width direction of the substrate.
The metal foil surface is in contact with the corner (the radius of curvature of the corner portion is less than 0.5 mm) of the first bar ₂ (in FIG. 1, it is installed so that α ₁ with respect to the width direction of the substrate is 45 degrees) which is installed with an α 1 of 50 degrees or less, and the substrate is folded at a turning angle of, for example, 60 degrees (i.e., the plane to which the substrate supplied to the first bar 2 belongs and the plane to which the substrate from the first bar 2 belongs are 60 degrees).
The substrate from the first bar 2 is then folded back at an angle of -10 to +10 degrees relative to the first bar.
The substrate is then moved to the first rotating roll 3 (which is installed parallel to the first bar 2 in FIG. 1) which is set at an angle of 30 to 60 degrees with respect to the width direction of the substrate, and is folded back at an angle of 60 degrees so that the polyimide film comes into contact with the curved surface (the radius of curvature is 25 mm or less). The substrate from the rotating roll 3 moves in the direction of the arrow, and is turned back at an angle of 30 to 60 degrees, preferably 40 to 60 degrees, with respect to the width direction of the substrate.
The substrate is folded back at a 60-degree angle, with the metal foil surface in contact with the corner (with a radius of curvature of 0.5 mm or less) of a second bar 4 (in Fig. 1, it is installed so that _β1 relative to the width direction of the substrate is 45 degrees), which is installed at a 50-degree angle. The substrate from second bar 4 then moves to second rotating roll 5 (in Fig. 1, it is installed parallel to second bar 4), which is installed at an angle of -10 to +10 degrees relative to the second bar, and is folded back at a 60-degree angle so that the polyimide film is in contact with the curved surface (with a radius of curvature of 25 mm or less). The substrate from second rotating roll 5 continues in the direction of the arrow and is taken up by roll 6.

If the line angle is too small, the improvement in dimensional stability in the cross direction is small compared to that in the machine direction, and if the line angle is too large, the opposite problem occurs.

FIG. 2 is a schematic diagram showing an example of a situation in which a polyimide film is stretched using rectangular glass plates with cross sections having curved corners as shown in FIG. 8 as the first and second bars, and reverse curl with the metal foil surface facing inward is corrected using rectangular glass plates with cross sections having curved corners as shown in FIG. 8 as the third and fourth bars, thereby performing curl straightening and dimensional stability improvement operations.

That is, the A-FMCL 17 wound around the roll 11 moves in the direction of the arrow, and rotates at an angle of 30 to 60 degrees relative to the width direction of the substrate.
The first bar 12 is preferably set at _α2 of 40 to 50 degrees.
The substrate from the first bar 12 is then folded back at an angle of, for example, 60 degrees from the corner (the radius of curvature of the corner portion is less than 0.5 mm) of the first bar 12 ( _α2 is 45 degrees in FIG. 2). The substrate from the first bar 12 is then folded back at an angle of 60 to 120 degrees, preferably 70 to 110 degrees, and particularly 80 to 100 degrees from the first bar 14 ( _β2 is 9
The second bar 1 is folded back at a 60-degree angle while the metal foil surface is in contact with the corner (the radius of curvature of the corner is less than 0.5 mm).
The substrate from 4 is then cut by 30 to 60° in the width direction of the substrate.
The substrate then moves to a third bar 13 ( _α3 is 45° in FIG. 2 ), which is set at an angle of 60°, preferably 35 to 55°, and particularly preferably 40 to 50°, and is folded back at a 60° angle with the polyimide surface in contact with the corner (the radius of curvature of the corner portion is 0.5 to 25 mm). The substrate from the third bar 13 then moves to a fourth bar 15 (β3 is 90° in FIG. 2 ), which is set at an angle of 60 to 120°, preferably 70 to 110°, and particularly preferably 80 to 100°, with respect to the _third bar, and is folded back at a 60° angle with the polyimide surface in contact with the corner (the radius of curvature of the corner portion is 0.5 to 25 mm). The substrate from the fourth bar 15 then moves in the direction of the arrow to be taken up on a roll 16.

The material of the bar used in the first, second, third and fourth steps of the present invention may be glass, ceramics, metal,
Highly rigid materials such as synthetic resins are preferred, with tough ceramics such as zirconia ceramics being particularly preferred. The cross section (i.e., a cross section perpendicular to the length of the bar) may have any shape, such as a rectangle, square, or circle, with curved corners where the laminate contacts, as shown in Figures 7 and 8. The radius of curvature of the curved surface where the metal foil of A-FMCL contacts the bar is 0.01 mm or more and less than 0.5 mm, preferably 0.1 to 0.45 mm, and the radius of curvature of the curved surface where the polyimide layer contacts is 0.01 to 25 mm. If the radius of curvature of the curved surface of the bar where the metal foil contacts the bar is 0.5 mm or more, the difference in relative elongation between the polyimide layer and the metal foil layer is small when the long substrate moves along the bar under tension. Considering the principles of the present invention, sufficient dimensional stability for a circuit laminate (generally, a polyimide dimensional shrinkage (IPC FC240) of 0.1% or more is required) cannot be obtained. Furthermore, if the radius of curvature is smaller than 0.01 mm, the laminate may be scratched or cut when it moves along the bar, which is undesirable.

In addition, the curvature radius of the bar in contact with the polyimide layer is
If it is 25 mm or more, there is no deformation effect to sufficiently correct the plastic deformation of the metal foil, and if it is 0.01 mm or less, it is not preferable for the same reasons as above.

In the third and fourth steps of the present invention, the rotating rolls used to achieve smoother sliding of the laminate are made of metal, synthetic resin, ceramics, etc. The radius of curvature is 0.01 to 25 mm, preferably 5 to 25 mm, and the limitations on the radius of curvature are the same as those for the bar. If the rolls are deformed by the tension applied to the laminate, the rotating roll 31 can be reinforced with an auxiliary roll 32, as shown in Figure 3. It is also preferable that the rotation speed of the rotating rolls be controlled to prevent the substrate from moving to one side.

In the present invention, the "folding angle" means the angle formed by the surface of the long A-FMCL supplied to contact the bar or rotating roll, as described above, and the surface of the substrate that contacts the bar or rotating roll, is folded back, and moves. The angle is not particularly limited, but is preferably 20
〜160℃, especially preferably 60〜150℃.
If the angle is less than 160 degrees, the frictional resistance and resistance due to bending rigidity when the laminate moves on the bar or rotating roll will be large, and there will be problems with the three-dimensional configuration of the equipment, making it difficult to move the laminate smoothly.If the angle is more than 160 degrees, the distance over which the laminate contacts the bar or rotating roll will be small, and the deformation stress experienced by the laminate will be very small, making it impossible to straighten the curled laminate or improve its dimensional stability.

The A-FMCL is kept in contact with the curved surfaces of the first and second bars under tension. This tension can be maintained by a known device for applying tension to a long laminate. The appropriate tension range varies depending on the degree of curl and dimensional stability of the laminate, the materials and thicknesses of the metal foil and polyimide layer, and the radius of curvature of the bars, but is usually greater than 200 gr per cm of A-FMCL width, preferably in the range of 300 to 1500 gr.
The same applies to the case where the second rotating roll or the third and fourth bars are in contact with the first and second bars, but the appropriate tension range is 2000
If the tension applied to the laminate is 200 g/cm or less, the bending rigidity of the laminate means that when the laminate moves on the bar, the length over which the laminate moves along the curved surface of the bar is extremely short, and as a result, the radius of curvature of the curved surface drawn by the laminate on the bar becomes large, making it difficult to achieve the effects of the present invention. On the other hand, if the tension is 2000 g/cm or more, the plastic deformation of the metal foil in the tension direction due to the tension becomes larger than the plastic deformation of the polyimide layer,
This has a negative impact on the process stability improvement.

In the present invention, there is no particular limitation on the speed at which the long A-FMCL is moved on the curved surface of the bar or rotating roll.
In practice, the preferred speed is 0.2 to 10 m/min.

When curing is performed in this invention, the temperature is 100°C or higher for 30
The treatment is carried out for at least 1 minute, preferably at 140-180° C. for 30-120 minutes. Temperatures below 100° C. are possible, but the effect is slow to appear, and temperatures above 250° C. are not preferred because they may cause oxidation of the metal foil or a decrease in adhesive strength.

The curl correction and dimensional stability improvement of the present invention are preferably
The temperature is 200°C or less. Although it is possible to correct curling and improve dimensional stability at temperatures above 200°C, this is not preferred because when the substrate is returned to room temperature, the temperature change can cause curling to reoccur and dimensional stability to deteriorate. Therefore, the particularly preferred temperature range is 10 to 200°C.
When the method of the present invention is carried out in this manner, the recurrence of curling and the deterioration of dimensional stability due to subsequent temperature changes are negligible.

In addition, there is no particular limitation on the means for moving the laminate to the bar or rotating roll used in the first, second, third and fourth steps of the present invention, and if the laminate deviates from the line of travel, a controller for correcting the line can be selected from various methods as appropriate.

The method for straightening curl and improving dimensional stability of the present invention substantially eliminates curling and poor dimensional stability that occur in a long A-FMCL that consists of a long metal foil and a thin layer of aromatic polyimide that is provided on the surface of the metal foil without an adhesive layer, and by not including an adhesive layer, the circuit processability of the A-FMCL is greatly improved, taking advantage of the excellent heat resistance, electrical properties, and mechanical properties of the aromatic polyimide.

Next, the present invention will be further explained by showing examples and comparative examples.

Example 1 In a vessel equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube,
4,4'-bis(3-aminophenoxy)biphenyl 22
1 g (0.60 mol) of 4,4'-diaminophenyl ether and 280 g (1.4 mol) of 4,4'-diaminophenyl ether were dissolved in 3500 ml of N,N-dimethylacetamide, cooled to around 0°C, and 436 g (2.0 mol) of pyromellitic dianhydride was added under a nitrogen atmosphere and stirred at around 0°C for 2 hours. The solution was then returned to room temperature and stirred under a nitrogen atmosphere for approximately 20 hours. The inherent viscosity of the polyamic acid solution thus obtained was 1.7 d/g.
This polyamic acid solution was diluted to 19% with N,N-dimethylacetamide to adjust the rotational viscosity to 120,000 cps.

This solution was uniformly cast onto rolled copper foil (thickness 35μ),
After heating and drying at 130℃ for 5 minutes and then at 160℃ for 5 minutes,
The copper foil was heated for 5 minutes in a nitrogen atmosphere (oxygen concentration 3%) at 250°C to obtain a polyimide-coated copper foil.
The A-FMCL thus obtained was 24 cm x 24
When a square substrate of 2.5 cm was used, curling with a curvature radius of 2.5 cm occurred in both the TD and MD directions with the polyimide layer inside. The dimensions of the polyimide film on this substrate were compared with the state with copper foil and the state with the copper foil completely covered with ordinary dichloromethane.
When compared to the state after etching with copper solution, where only the polyimide film remains, the dimensions after etching the copper foil are 0.45 in both the TD and MD directions compared to before etching.
This reduction in size will be referred to as dimensional shrinkage hereafter.

The above-mentioned long A-FMCL was slit to a width of 24 cm using a slitter and wound on a take-up roll. Then, the laminate was moved to a first bar made of glass (see Figure 1, fixed at an angle of 45 degrees to the TD direction of the substrate, i.e., α ₁ = 45 degrees (line angle)). The cross section was 20 mm wide and 100 mm long.
The laminate was folded at an angle of 80 degrees, with the copper foil surface in contact with the corners (the radius of curvature of the corners was 0.3 mm) of a 100 mm rectangular bar. The laminate was then moved from the first bar and folded at an angle of 100 degrees so that the polyimide film was in contact with the first rotating roll (see Figure 1, fixed so as to be parallel to the first bar, with a rotation speed of 60% of the free rotation, and a radius of curvature of 5 mm). At this time, the laminate was moved while applying a tension of 12 kg (i.e., 0.5 kg/cm width). After this, the second bar (see Figure 1, with a rotation speed of 60% of the free rotation speed of the substrate) was moved.
The first bar was fixed at a 45-degree angle (line angle) (i.e., _β1 = 45 degrees) and made of the same material and shape as the first bar), and folded back at an 80-degree angle with the copper foil surface in contact with the corner. The laminate from the second bar was moved to a second rotating roll made of stainless steel (see Figure 1, fixed so as to be parallel to the second bar, and the rotation speed was controlled to 60% of the free rotation. The radius of curvature was 5 mm), and folded back at an 80-degree angle with the polyimide film in contact with the roll. At this time, the long laminate was loaded with 12 kg (i.e., 0.5 kg
The substrate was moved while applying a tension of 1000 kJ/cm width. These operations were carried out at room temperature, and the laminate was moved at a speed of 3 m/min. The above operations were repeated twice. The laminate was then wound up and placed in a dryer at 150°C for 60 minutes, after which it was allowed to cool naturally.

The laminate obtained by the above procedure was cut into a 24 x 24 cm square laminate and visually inspected for curling, but no curling was observed. The dimensional shrinkage in both the TD and MD directions was 0.08%.

Comparative Example 1 In Example 1, the tension applied to the long laminate was 2.4 kg.
The same procedure was followed except that the applied load was 0.1 kg/cm width. This laminate was cut into a 24 x 24 cm square and examined for curling, but no curling was observed. However, the dimensional shrinkage was 0.35% in both the TD and MD directions.

Comparative Example 2: The same procedure as in Example 1 was repeated, except that the curvature radius of the corner where the copper foil surface of the bar contacted was 5.0 mm. This laminate was cut into a 24 x 24 cm square laminate and the curling condition was examined. The curvature radius of the curl with the polyimide layer on the inside was 10 cm in both the TD and MD. Dimensional shrinkage of 0.40% was observed in both the TD and MD.

Example 2 In a vessel equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube,
234g of 1,3-bis(3-aminophenoxy)benzene
(0.80 mol) and 240 g (1.2 mol) of 4,4'-diaminophenyl ether in N,N-dimethylacetamide 45
The solution was dissolved in 1000 ml of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (644 g, 2.0 mol) under a nitrogen atmosphere and stirred at 10°C for 24 hours to obtain a polyamic acid solution. The inherent viscosity of the polyamic acid in the resulting solution was 1.5 d/g. The polyamic acid solution was diluted to 15% with N,N-dimethylacetamide to adjust the viscosity to 25,000 cps, and then uniformly coated onto rolled copper foil (35 μm thick) using a doctor blade.
This coated copper foil was dried by heating at 130°C for 60 minutes, and then heated at 260°C in a nitrogen atmosphere (oxygen concentration 4%) for 60 minutes to obtain a polyimide-coated copper foil. The film thickness was 25 μm.
When the polyimide film was used on a square substrate measuring 24 cm x 24 cm, curling occurred in both the TD and MD directions with a radius of curvature of 2.0 cm, with the polyimide layer facing inward. The dimensional shrinkage of the polyimide film was 0.48%.

The long A-FMCL was slit to a width of 24 cm using a slitter and wound onto a take-up roll. Then, a first glass bar (see Figure 2, 45 degrees to the TD direction of the laminate,
That is, the wire is fixed at an angle of α ₂ = 45 degrees (line angle), and the cross section is a rectangle with a width of 15 mm and a length of 100 mm), and the wire moves at a folding angle of 70° while the copper foil surface is in contact with the corner (the curvature radius of the corner is 0.4 mm).
The laminate removed from the first bar was placed on a second bar made of glass (see Figure 2, 90 degrees relative to the first bar).
degrees, i.e., β ₂ = 90 degrees,
The corner of the bar (the same shape as the first bar) (the radius of curvature is 0.4m)
The laminate was then moved to a bar (see Figure 2), and folded at a 70° angle with the copper foil surface in contact with the bar. The tension applied to the laminate as it moved between the corners of the first and second bars was 18 kg. The laminate was then removed from the second bar and placed on a third glass bar (see Figure 2, which was set parallel to the second bar, i.e., α ₃ = 45°, and its cross section was 20 mm wide and 100 mm long).
The laminate was then transferred to a fourth bar (see Figure 2, which was set at a 90-degree angle relative to the third bar, i.e., β 3 = 90 degrees; a bar of the same shape as the third bar) and folded at a 110-degree angle with the polyimide surface in contact with the bar. The laminate was then transferred to a fourth bar (see Figure 2, which was set at a 90-degree angle relative to the third bar, i.e., β ₃ = 90 degrees) and folded at a 110-degree angle with the polyimide surface in contact with the bar. The tension applied to the laminate as it moved between the corners of the third and fourth bars was 12 kg. This procedure was performed at room temperature, with the laminate moving at a speed of 1 m/min. This procedure was repeated three times. The laminate obtained after this procedure was used as a 24 x 24 cm square substrate and examined for curling; no curling was observed. Dimensional shrinkage was 0.07% in both the TD and MD directions.

Comparative Example 3 In Example 2, the first bar made of glass was
The same procedure as in Example 2 was repeated, except that the first bar was fixed at a line angle of 20 degrees relative to the TD, the second bar was set at a 40-degree angle relative to the first bar, the third bar was set parallel to the second bar, and the fourth bar was set at a 40-degree angle relative to the third bar. This laminate was cut into a 24 x 24 cm square and examined for curl. No curl was observed in the MD, but slight curl with a radius of curvature of approximately 20 cm was observed in the TD. Dimensional shrinkage was 0.0 in the MD.
06%, but in the TD direction it was 1.6%.

Example 3 In a vessel equipped with a stirrer, a reflux condenser, and a nitrogen inlet tube,
4,4'-diaminophenyl ether 421 g (2.1 mol)
was dissolved in 4000 ml of N-methylpyrrolidone. To this solution, 458 g of pyromellitic dianhydride was added under a nitrogen atmosphere.
(2.1 mol) was added and the reaction was allowed to proceed at room temperature for 24 hours. The inherent viscosity of the polyimide acid solution thus obtained was 1.8 d/g.
This polyimide acid solution was diluted to 16% with N,N-methylpyrrolidone, and the rotational viscosity was adjusted to 110,000 cps.

This solution was uniformly cast onto high ductile electrolytic copper foil (Mitsui Mining & Smelting Co., Ltd., HTE copper foil thickness 18 μm),
After heating and drying at 130°C for 5 minutes and then at 180°C for 5 minutes,
The copper foil was then heated at 25°C for 5 minutes in a nitrogen atmosphere (oxygen concentration 2%) to obtain a polyimide-coated copper foil.
When the A-FMCL thus obtained was cut into a 24 × 24 cm square laminate, curling occurred in both the TD and MD directions with a curvature radius of 1.5 cm, with the polyimide layer facing inward. The dimensional shrinkage was 0.55%.

The long A-FMCL was slit to a width of 24 cm using a slitter, and then subjected to curl correction and dimensional stability improvement in the same manner as in Example 1. This laminate was cut into a 24 cm x 24 cm square laminate and examined for curl, but no curl was observed. The dimensional shrinkage was 0.10% in both the TD and MD directions.

Example 4 In Example 2, the first and second glass bars were replaced with toughened zirconia ceramic bars (each having a rectangular cross section with a width of 0.6 mm and a length of 30 mm, and one end of the rectangular copper foil surface in contact with the bar was a semicircle with a radius of curvature of 0.3 mm). The third and fourth glass bars were replaced with toughened zirconia ceramic bars (each having a rectangular cross section with a width of 1.0 mm and a length of 30 mm, and one end of the rectangular polyimide surface in contact with the bar was a semicircle with a radius of curvature of 0.5 mm). The folding angle at which the laminate was folded with the polyimide surface in contact with the corners of the third and fourth bars was set to 15°.
0 degrees and repeating the operation twice.
The laminate obtained by this procedure was
The laminate was cut into a 24x24cm square and examined for curling, but no curling was observed. The dimensional shrinkage was 0.05% in both the TD and MD directions.

Claims (8)

[Claims] [Claim 1] A method for manufacturing a flexible metal foil laminate comprising: a first step of sliding a long flexible metal foil laminate having an aromatic polyimide thin film formed directly on a long metal foil without an adhesive, in a longitudinal direction under tension, over the curved surface of a first bar provided at an angle of 30 to 60 degrees relative to the width of the laminate, with the metal foil facing inward; a second step of sliding the laminate in a longitudinal direction under tension, with the metal foil facing inward, over the curved surface of a second bar provided at an angle of 60 to 120 degrees relative to the first bar; a third step of sliding the laminate in a tensile state in the longitudinal direction over the curved surface of a third bar or a first rotating roll disposed at an angle of 60 to 120 degrees relative to the third bar or the first rotating roll, with the imide thin film facing inward; and a fourth step of sliding the laminate in a tensile state in the longitudinal direction over the curved surface of a fourth bar or a second rotating roll disposed at an angle of 60 to 120 degrees relative to the third bar or the first rotating roll, with the imide thin film facing inward. [Claim 2] In the first and second steps, the radius of curvature of the curved surfaces of the first and second bars is less than 0.5 mm, the tension is expressed by the tension applied to the laminate, the tension is greater than 200 g/cm, and the temperature of the laminate when sliding on the curved surfaces of the first and second bars is 200°C or less, and in the third and fourth steps, the radius of curvature of the curved surfaces of the third and fourth bars or the first and second rotating rolls is 0.01 to 25 mm, and the tension applied to the laminate is 20
2. The method according to claim 1, wherein the temperature of the laminate when sliding on the curved surfaces of the third and fourth bars or the first and second rotating rolls is 200°C or less. Claim 3: The order of steps is step 1, step 2, step 3
2. The method according to claim 1, wherein the order is step 1 and step 4, and each step is carried out one or more times. 4. The method according to claim 1, wherein the steps are carried out in the order of step 1, step 3, step 2 and step 4, and each step is carried out one or more times. Claim 5: The order of steps is step 1, step 2, step 3
The method according to claim 2, wherein the order is step 1 and step 4, and each step is carried out one or more times. 6. The order of steps is step 1, step 3, step 2
The method according to claim 2, wherein the order is step 1 and step 4, and each step is carried out one or more times. 7. After the final step, the laminate is
2. The method according to claim 1, wherein the curing is carried out at a temperature of 100°C or higher for 30 minutes or more. 8. After the final step is completed, the laminate is
3. The method according to claim 2, wherein the curing is carried out at a temperature of 0°C or higher for 30 minutes or more.