KR101011900B1 - Laminate structure comprising stainless foil, resin and metal foil - Google Patents

Abstract

The present invention provides a laminate structure having a low warpage composed of stainless foil, resin, and metal foil, and in a laminate structure composed of a three-layer structure of stainless foil, resin, and metal foil, a stainless steel has a ferromagnetic phase and a non-ferromagnetic phase In addition, the proportion of the ferromagnetic phase is 0.1% by mass or more and 4.0% by mass or less.

Stainless foil, metal foil, ferromagnetic phase, laminate structure

Description

Laminated structure consisting of stainless steel foil, resin and metal foil {LAMINATE STRUCTURE COMPRISING STAINLESS FOIL, RESIN AND METAL FOIL}

Industrial Applicability The present invention can be used for structures for electronic devices including memory devices and circuit boards. In particular, it is suitable for the laminate structure for suspension for hard disk drives which requires stable position precision.

Composite materials, especially laminate structures composed of metals and resins, have been used in various fields because they can obtain a plurality of properties that cannot be obtained with a single substance, and their fields of application are increasingly being used for light and thin applications. .

In these fields, precise positional precision is required for the laminate structure supporting the device in order to accurately express magnetic, electrical or dielectric physical action in the device. For example, the magnetic physics is used to support the magnetic head for a hard disk, the electrical physics is applied to the flexible printed circuit board, and the dielectric physics is applied to the ferroelectric memory head. Can be mentioned.

Although it is a laminate structure used in various fields, thermal expansion properties and heat shrinkability that are different from material to material can not ignore the effects of warpage. In particular, the thinner the thickness, the greater the effect.

In the method of suppressing warpage of the laminate structure, in the case of the thermoplastic resin, the temperature is increased and softened, and after the pressure is applied to the laminate structure using a press device or the like to correct the warpage, the resin is cooled to increase viscosity and increase adhesion. On the other hand, in the case of a thermosetting resin, pressure was applied to the laminate structure with a press device or the like to correct the warpage, and at that time, temperature was applied to cure.

These measures are effective against warping in a state where the temperature of the resin is high, but when the temperature is lowered to near the room temperature, distortion due to heat shrinkage occurs and is not eliminated. Even if it is eliminated, for example, in order to correct warpage, it is necessary to heat pressurize with a press apparatus for a long time, thereby significantly lowering the productivity of the apparatus.

Conventional techniques relating to a suspension laminate structure for a hard disk drive include, for example, Japanese Patent Application Laid-Open No. 2005-125588 for a thermal expansion coefficient and adhesive force of a resin layer. Although the adhesive force and the etching workability of the alloy are mentioned, it is difficult to stably reduce the warpage as long as it goes through a heating process to increase the adhesive force in the process of manufacturing the laminate structure as described above. The technique described in the present invention, that is, optimization of the ferromagnetic phase ratio inside the stainless foil, is not mentioned at all to suppress the warpage of the laminate structure.

An object of this invention is to provide the laminated structure which consists of three layers of stainless foil, resin, and metal foil, and was curvature suppressed.

Summary of the Invention The gist of the present invention is that in a laminate structure having a three-layer structure of stainless foil, resin, and metal foil, the stainless foil is a mixed phase of the ferromagnetic phase and the non-ferromagnetic phase, and the ratio of the ferromagnetic phase is 0.1% by mass. The laminate structure is 4.0% or less. More preferably, in the laminate structure for hard disk suspension composed of a three-layer structure of stainless foil, resin, and metal foil, the stainless foil is a mixed phase of ferromagnetic phase and non-ferromagnetic phase, and the ratio of ferromagnetic phase is 0.1% or more and 4.0% by mass. Hereinafter, the other metal foil is a copper foil or a copper alloy foil, which is a laminate structure.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the cross section which shows the structure of the laminate structure of this invention.

Hereinafter, the present invention will be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows the structure of the laminate structure of this invention. As can be seen from Fig. 1, the laminate structure 1 of the present invention is formed between a stainless foil 2 and a metal foil 3, and a thermoplastic resin or a thermosetting resin or a thermoplastic resin and a thermosetting resin for joining both foils. It has a three-layer structure composed of the composite body 4.

The metal foil 3 is foil of a metal and / or alloy of a composition different from the stainless foil 2.

The laminate structure 1 is produced by applying a thermoplastic or thermosetting resin 4 for bonding between a stainless foil 2 and a foil 3 of a different metal, and then bonding them together by heating. Although the adhesion temperature by this heating is generally 100-400 degreeC, it is not limited to this, According to the hardening or plasticization temperature of resin to be used, it can select suitably.

By the way, when laminating the resin between the stainless foil which comprises this invention, and metal foil from which a component differs, the curvature accompanying the difference of the amount of heat shrinkage will generate | occur | produce in a laminated structure.

In the stainless foil, either or both of the ferromagnetic and nonmagnetic phases are mixed. The ferromagnetic phase has a small amount of heat shrinkage and, for example, tends to bend toward the stainless side when laminated with a metal such as copper. On the other hand, the nonmagnetic phase has a large amount of heat shrinkage and tends to bend to the non-stainless side when laminated with a metal such as copper.

As described above, since the ferromagnetic phase of the stainless foil has a small amount of heat shrinkage, while the nonmagnetic phase has a large amount of heat shrinkage, it is possible to control the warping when the laminate structure is formed by adjusting the ratio of these phases. In the present invention, the proportion of the ferromagnetic phase is 0.1% to 4.0% by mass. This is because when the proportion of the ferromagnetic phase is less than 0.1% by mass, the effect of suppressing warpage is small, and when the ratio is more than 4.0%, the ferromagnetic phase is easily bent on the metal foil side. Moreover, although the degree of curvature changes also with the kind of metal foil of a laminated structure, the curvature of a laminated structure can be suppressed by selecting suitably within the said range.

The measuring method of the ferromagnetic phase is not particularly limited, and a vibration sample magnetometer (VSM), a ferrite meter, or the like can be used.

In addition, the stainless foil described in this invention means an austenitic stainless steel or two-phase stainless steel. In the course of rolling, the stainless steel is thinned, and a part of the nonmagnetic phase is organically transformed into a magnetic phase to become two phase. The ratio of the ferromagnetic phase of the stainless foil can be controlled by the reduction ratio at the time of rolling, the temperature of the stainless steel at the time of rolling, and the like.

As for the metal foil described in this invention, the metal and alloy of thickness 100 micrometers or less from a stainless foil and a component are named generically. In particular, gold, silver, and copper are ductile, easy to process thinly, have a high electrical conductivity, a circuit can be formed by an etching process, and also have excellent thermal conductivity and excellent heat dissipation. In addition, it is possible to improve the mechanical strength by alloying.

Regarding the copper alloy in the metal foil, Ni, Si, Mg, Be, etc. are typically used as the alloying element, but are not limited to these, and from the viewpoint of maintaining physical properties (other than mechanical strength) that are approximately equivalent to that of Cu alone , Cu may be considered to be more than 90% by mass.

Resin described in this invention contains both a thermoplastic resin and a thermosetting resin. The thermoplastic resin refers to thermoplastic polyimide, polystyrene, polyethylene, polyamide and the like, but is not limited thereto. Especially in the case of the polyimide which is excellent in heat resistance, the amount of heat shrinkage between room temperature and high temperature is large, and the suppression effect of the curvature of the base material of this invention is large.

The thermosetting resin refers to a thermosetting polyimide, urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester, alkyd resin, urethane resin, ebonite resin and the like, but is not limited thereto. The present invention is effective for all resins requiring a heating step. The resin may be one layer or a plurality of layers. Selection and combination of a thermoplastic resin layer and a thermosetting resin layer are arbitrary. The thickness of the resin (the total in the case of multiple layers) is preferably 5 µm or more and 100 µm or less, and 5 µm or more and 25 µm is further preferable for the purpose of weight reduction, but is not limited to these numerical values.

In the recent hard growth of the hard disk drive, the gap between the magnetic head and the recording medium is narrowing year by year with increasing density. The gap, which was 100 nm around 1995, is now tightened to 20 nm or less. On the other hand, the suspension supporting the magnetic head is required to be lightweight due to vibration resistance, and stainless steel having a required thickness of 100 µm or less (generally, a thickness of 100 µm or less) is used.

According to the present invention, it is possible to eliminate the warpage of a laminate structure having a three-layer structure of a stainless foil, a resin, and a metal foil, and a laminate structure for a hard disk drive suspension having a small problem of positional accuracy due to warpage caused by a shrinkage difference even if thin. It can manufacture stably.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely based on an Example.

(First embodiment)

As stainless foil, SUS304 foil of thickness 20mm and width 400mm and 20micrometer thickness copper foil were bonded together by hardening with thermoplastic polyimide resin (hardening temperature: 350 degreeC), and the state of curvature was observed. The curvature judged that the maximum amount of the curvature of the laminated structure which fixed and hung the upper end part after cutting the laminated structure to 1 m was 100 mm or less with respect to a vertical plane. The thickness of the thermoplastic polyimide resin was 5 µm, 25 µm and 100 µm.

Among these, stainless steel foils used for samples having good warpage and samples not having good results, respectively, as a result of measuring the saturation magnetic flux density with a vibration sample magnetometer (VSM) device. It was confirmed that the shape was obtained.

Since the vibration sample magnetometer (VSM) device was expensive, installed in a clean environment, and the maintenance and inspection cost were expensive, it was measured by a ferrite meter that can easily measure the ferromagnetic phase. The results are shown in Table 1. The measurement by the ferrite meter was carried out by laminating stainless steel foil to 1.0 mm and making a magnetic sensor part contact. The measurement temperature of the vibration sample magnetometer (VSM) apparatus and the ferrite meter was made into room temperature (25 degreeC).

In addition, while the measurement of the saturation magnetic flux density by the vibration sample magnetometer (VSM) device has a small dimension and shape dependency of the sample, the measurement of the ratio of the ferromagnetic phase by the ferrite meter has a shape dependency on the thickness of the sample from the measurement principle. This exists. Therefore, the measurement by the ferrite meter in this invention laminated | stacked the stainless foil, and unified the sample thickness on 1.0 mm conditions.

Since the sample thickness of the laminated foil is constant, the saturation magnetic flux density of the stainless foil and the ferromagnetic phase ratio measured by the ferrite meter have a constant corresponding relationship as shown in Table 1 of Example.

(2nd Example)

Stainless steel foil with a thickness of 100 μm and a width of 650 mm (20 mm width for Au and Ag metals) and various metal foils (100 μm thick, 650 mm for width and short metal foils of Au and Ag) 20 mm) was hardened by epoxy resin (18 micrometers in thickness of resin), and both were bonded together (hardening temperature: 100 degreeC), and the state of curvature was observed.

In addition, as copper alloy Cu-Ni-Si-Mg, the thing of the composition range of Ni: 2.2-4.2 mass%, Si: 0.025-1.2 mass%, Mg: 0.05-0.3 mass% was used.

In addition, observation of curvature was performed similarly to the 1st Example.

The stainless foil was annealed at 1050 ° C., then rolled to 100 μm, and the reduction ratio at that time was changed to measure the ratio of the magnetic phase. In the measurement, the stainless foil was laminated | stacked to thickness 1.0mm, and the value was measured by the ferrite meter.

Table 2 shows the ratio of the magnetic phase of the stainless foil which is optimal for each kind of metal foil. By optimizing the proportion of the magnetic phase, a laminate structure without warpage can be obtained.

(Third Embodiment)

As the stainless foil, various stainless foils having a thickness of 20 μm and a width of 300 mm and copper foil (thickness of 20 μm, width of 300 mm) were bonded together by curing with a thermoplastic polyimide resin (thickness of the resin 10 μm) (curing temperature: 350 ° C.) The state of warpage was observed.

In addition, observation of curvature was performed similarly to the 1st Example.

After the stainless foil was annealed at 1150 ° C., it was rolled to 20 μm, and the reduction ratio at that time was changed to measure the ratio of the magnetic phase. In the measurement, the stainless foil was laminated | stacked to thickness 1.0mm, and the value was measured by the ferrite meter.

Table 3 shows the ratio of the optimum magnetic phase for each stainless foil. By optimizing the proportion of the magnetic phase, a laminate structure without warpage can be obtained.

Here, the steel grade of stainless foil is based on JIS G4304 and JIS G4305. In addition, each of these steel grades has been determined to correspond to ISO and related foreign standards UNS, AISI, DIN and the like.

According to this invention, it becomes possible to stabilize the curvature of the laminated structure which consists of a three layer structure of stainless foil, resin, and metal foil to a low position. Specifically, the present invention can be widely used in a field where exact positional accuracy, which is represented by a support of electrical, magnetic and dielectric elements, such as a support of a magnetic head for a hard disk, a flexible printed circuit board, and a head support for a ferroelectric memory, is required. In particular, it can be an effective means in the suspension member for hard disk drives, in which the structure is thin and high precision is required.

Claims (2)

A laminate structure comprising a three-layer structure of stainless foil, resin, and metal foil, wherein the stainless foil is a mixed phase of the ferromagnetic phase and the non-ferromagnetic phase, and the ratio of the ferromagnetic phase is 0.1% or more and 4.0% or less by mass. In the laminate structure for a hard disk suspension composed of a three-layer structure of stainless foil, resin, and metal foil, the stainless foil is a mixed phase of a ferromagnetic phase and a non-ferromagnetic phase, and the ratio of the ferromagnetic phase is 0.1% or more and 4.0% or less by mass, and a metal foil It is this copper foil or copper alloy foil, The laminated structure characterized by the above-mentioned.

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