JP2870133B2 - Film capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a film capacitor.

[Prior art] In recent years, with the miniaturization of electronic devices, there has been an increasing demand for miniaturization of electronic components such as capacitors. For this reason, the development of so-called chip capacitors which are compatible with surface mounting of film capacitors has been advanced. I have. A so-called multilayer capacitor having a structure in which a dielectric film divided into rectangles and an electrode such as a vapor-deposited film are laminated is particularly effective for miniaturization. At this time, it is known that a protective layer formed by superposing a thick film or sheet on the outside of the capacity generating portion is known because the dielectric film is usually a thin film and easily damaged. However, the chip capacitor is required to have high solder heat resistance because it is directly attached to the substrate, but there is no means for forming a protective layer having high chemical resistance and excellent dimensional accuracy.

[Problems to be Solved by the Invention] In order to form a heat-resistant protective layer, it is conceivable to use a heat-adhesive polyimide film or a biaxially oriented polyphenylene sulfide film having a high heat resistance. Films are expensive and have disadvantages such as poor chemical resistance, rapid degradation by hydrolysis under high humidity, and poor dimensional stability against humidity, which limits the use environment of capacitors. Become. In addition, according to the study of the present inventors, only the ordinary biaxially stretched polyphenylene sulfide film has poor adhesiveness between film layers, so that it can be easily peeled off after molding and has no practical use. It is also conceivable to use a film obtained by applying an adhesive to a biaxially stretched polyphenylene sulfide film.However, since the biaxially stretched polyphenylene sulfide film shrinks slightly when heated, it is shaped when it is dipped in molten solder. However, there was a defect that the change of the film and the peeling occurred, and none of them was practical.

Accordingly, an object of the present invention is to provide a capacitor having a protective layer having sufficient solder heat resistance, high chemical resistance and excellent dimensional accuracy.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. That is, the present invention provides a film capacitor having a capacitance generating portion obtained by winding or laminating a dielectric film and an electrode alternately and a protective layer formed by laminating a plastic film provided outside thereof. Wherein the outermost layer of the protective layer comprises a biaxially oriented polyphenylene sulfide film, and a thickness of 20% or more of the total thickness of the protective layer comprises a substantially unstretched polyphenylene sulfide film. It is a film capacitor.

The type of the film serving as the dielectric of the capacitor of the present invention is not particularly limited. For example, polyethylene terephthalate, polyester such as polyethylene naphthalate,
Polyolefins such as polypropylene, polystyrene,
Polycarbonate, polyphenylene sulfide, polyether ether ketone, any of well-known ones such as polyimide may be used, but since the protective layer film has high heat resistance and chemical resistance, the dielectric film is also polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyether. The effect of the present invention is great when the maximum continuous use temperature such as ether ketone exceeds 120 ° C. In particular, the effect of the present invention is extremely large when the maximum temperature of continuous use such as polyethylene naphthalate, polyphenylene sulfide, and polyether ether ketone exceeds 155 ° C. Further, a capacitor in which a layer provided by a method such as coating other than the above-mentioned film as a dielectric acts as a composite dielectric may be used.

In the capacitor of the present invention, the electrode may be a metal thin film formed on a dielectric by a vacuum evaporation method or the like, or may be a metal foil having self-supporting properties.

Further, the structure may be any of a wound type and a laminated type, but the effect of the present invention is great when the laminated film capacitor is used.

In the present invention, the outermost layer of the protective layer needs to be formed of a biaxially stretched polyphenylene sulfide film (hereinafter, may be abbreviated as a PPS-BO film). However, for the second layer immediately below the outermost layer, a PPS-BO film, a substantially unstretched polyphenylene sulfide film (hereinafter may be abbreviated as a PPS-NO film), another film, a fiber reinforced sheet, or the like is used. Of these, a PPS-BO film or a PPS-NO film is preferred. Here, when the second layer is also a PPS-BO film, the adhesive layer and the like are in a range that does not impair the characteristics of the PPS-BO film, preferably 30% or less of the thickness of the PPS-BO film. It may be present between the layers. In this case, the adhesive is preferably a thermosetting resin having a softening temperature of 260 ° C. or higher after curing, or an adhesive mainly containing a thermoplastic resin. The second layer is PPS
When the film is a —NO film, it is preferable that the film is laminated without substantially interposing an adhesive or the like.

By arranging the PPS-BO film layer in the outermost layer, the strength of the capacitor element can be maintained and the heat resistance, moisture resistance and chemical resistance of the capacitor can be balanced at a high level. When the second layer is made of a film other than the PPS-BO film, the thickness of the outermost PPS-BO film, and a plurality of PPS-B films including the outermost layer continuously.
When the O films are laminated, the total thickness of the PPS-BO film layer portions is 25 μm or more, respectively, or 30% or more with respect to the total thickness of the protective layer from the viewpoint of the element protection effect. preferable. It is also preferable to use a biaxially stretched polyphenylene sulfide film other than the outermost layer, and it is particularly preferable that a PPS-NO film and a PPS-BO film are alternately arranged.

Here, the biaxially stretched polyphenylene sulfide film (PPS-BO film) is a biaxially stretched film of a resin composition containing poly-p-phenylene sulfide as a main component. The thickness of the film is preferably in the range of 5 μm to 100 μm. The heat shrinkage of the film at 230 ° C. for 10 minutes is 0% to + 12% in the longitudinal direction of the film, and -5% to + 5% in the direction perpendicular to the longitudinal direction in view of the dimensional stability of the obtained capacitor. It is preferred that

Here, the resin composition containing poly-p-phenylene sulfide as a main component (hereinafter sometimes abbreviated as a PPS resin composition) refers to a poly-p-phenylene sulfide containing 70% by weight or more, preferably 85% by weight. Refers to a composition containing the above. When the content of poly-p-phenylene sulfide is less than 70% by weight, heat resistance, which is a feature of a film comprising the composition,
Damage frequency characteristics, temperature characteristics, etc.

Here, poly-p-phenylene sulfide (hereinafter sometimes abbreviated as PPS) refers to a repeating unit of 70-
Mol% or more (preferably over 85 mol%) is a structural formula Means a polymer comprising the structural unit represented by Such components
If it is less than 70 mol%, the crystallinity and the heat transition temperature of the polymer will be low, and the heat resistance, dimensional stability, mechanical properties and the like, which are the characteristics of a film composed of a resin composition containing PPS as a main component, will be impaired. The melt viscosity of PPS is preferably in the range of 500 to 15,000 poise at 300 ° C. and a shear rate of 200 sec ⁻¹ .

The present invention also provides a protective layer having a total thickness of 20% or more, preferably 20% or more and 70% or less, more preferably 40% or more.
It is necessary that 70% or less consist of a substantially unstretched polyphenylene sulfide film (PPS-NO film). Due to the presence of this PPS-NO film layer, the adhesion between the layers is ensured, and the PPS-NO film layer absorbs the dimensional change at the time of solder dip of the PPS-BO film, and the peeling of the protective layer, Destruction of the dielectric layer can be prevented.

Here, in the substantially unstretched polyphenylene sulfide film (PPS-NO film), the same PPS resin composition or PPS as the biaxially stretched polyphenylene sulfide film is preferably used. The thickness of the PPS-NO film is preferably in the range of 15 μm to 200 μm.

In the present invention, “substantially no stretching” means that the orientation degree measured from three directions of Through, Edge and End is 0.70 or more. Here, the degree of orientation measured from a certain direction is taken as an X-ray plate photograph from the desired direction, and [2,
[0,0] Degree of blackening when the diffraction ring is scanned in the radial direction on the equator line with a microdensitometer (I [φ = 0 °])
Similarly to the above, it is defined by the ratio (I [φ = 30 °] / I [φ = 0 °]) to the degree of blackening in the 30 ° direction (I [φ = 30 °]). That is, the degree of orientation is in the range of 0 to 1, and the closer this value is to 1, the higher the isotropy in a plane perpendicular to the measurement direction is, and it is virtually impossible for all three directions to be close to 1. Indicates orientation. If the film is in a substantially amorphous state and the [2,0,0] diffraction ring of the PPS crystal is not clearly observed, fix the film in a fixed length state and place it in an oven heated to 200 ° C. The heat treatment is performed for 1 minute to generate PPS crystals, and then the measurement is performed. This value does not change even after the capacitor is formed.

As the PPS-NO film used in the present invention, it is preferable to use a PPS-NO film having a relative crystallization index of 3.0 or less, which is substantially in an amorphous state, from the viewpoint of the handleability of the film and the adhesiveness between sheets. Here, the relative crystallization index means the maximum intensity (I ₂₀₀ ) of the [2,0,0] diffraction peak of the PPS crystal and the intensity (I ₂₅ ) at 2θ = 25 ° in the X-ray wide-angle diffraction profile of the sheet. Defined by the ratio I ₂₀₀ / I ₂₅ .

When a film made of polyphenylene sulfide in a substantially amorphous state is overlapped with a PPS-NO film or a PPS-BO film without substantially interposing an adhesive, a temperature of 100 ° C or higher and a temperature lower than the melting point of polyphenylene sulfide, 1 kg It is preferable to press the sheet in the thickness direction of the sheet with a pressure of at least / cm ² to bring the sheet layers into close contact with each other.

In addition, the crystallization temperature of the PPS-NO film used in the present invention at the time of temperature rise is preferably 130 ° C. or more from the viewpoint of ease of processing. Here, the crystallization temperature at the time of temperature rise is the temperature at which the maximum of the peak appearing in the range of 100 ° C. to 150 ° C. appears due to the progress of crystallization of PPS when the temperature is raised from room temperature at a rate of 20 ° C./min by differential thermal analysis Say that.

The capacitor of the present invention has a sufficient effect by the above configuration, but after forming a protective layer, heat-treated,
The PPS-NO film portion, preferably at a density of 1.330 g /
Crystallization to at least ³ cm ^3, more preferably at least 1.350 g / cm ³ is preferable because heat resistance is further improved.

The present invention is to obtain an excellent capacitor by using a PPS-BO film and a PPS-NO film in combination for the protective layer, but all the protective layers are formed from the biaxially oriented polyphenylene sulfide film portion and the unstretched polyphenylene sulfide film. It is not necessary to be constituted, and it is within a range that does not impair the characteristics, preferably 20% with respect to the total thickness of the protective layer.
Other sheets, films or resins such as a polyester film and a polyimide film, an adhesive layer, etc. may be used together with the biaxially stretched and substantially unstretched polyphenylene sulfide film as long as the following conditions are satisfied. PPS-BO film / PPS from outside as protective layer
-NO film, PPS-BO film / PPS-NO film / PPS
-BO film, PPS-BO film / PPS-NO film / PPS
A -BO film / PPS-NO film, a film in which more layers are laminated, and a film in which another resin, sheet, or film is interposed between the layers are conceivable, and any structure may be used.

 Next, a method for manufacturing the capacitor of the present invention will be described.

The capacitor of the present invention can be obtained without changing the conventional manufacturing method. That is, a means for obtaining a dielectric film and a metal foil or a vapor-deposited film serving as an electrode, a means for overlapping the dielectric film and the electrode so as to generate a capacitance, and a protective layer on the obtained capacity generating portion. Any conventionally known method can be applied as long as it has the means for providing. Further, a new method may be used. The method of forming the protective layer includes a method of providing a protective layer material including a PPS-NO film, and then laminating a PPS-BO film on the outermost layer.
A method of forming a protective layer by laminating a NO film and a PPS-BO film, preparing a composite film in which a PPS-NO film and a PPS-BO film are laminated in advance, and then preparing a PPS-BO
There is a method of forming a protective layer such that the film portion is on the outside. In the capacitor of the present invention, the protective layer does not need to be exposed to the outermost layer portion of the capacitor, and a so-called capacitor exterior such as coating with a resin or the like is provided around the capacitor element having the protective layer. No problem. However, the effect of the present invention is most exerted on a multilayer film chip capacitor having substantially no exterior.

[Effect of the Invention] Conventionally, the problem of delamination due to poor dimensional stability and poor adhesion of the protective layer material, which has been a problem particularly in high heat resistant capacitors, has been solved, and solder heat resistance, humidity resistance deterioration, The capacitor has a protective layer with high chemical resistance and excellent dimensional accuracy.

[Evaluation Method of Characteristics] The evaluation method of each characteristic in the present invention is as follows.

(1) Solder Resistance Test of Capacitor The capacitor is immersed in a molten solder bath at 260 ° C. for 10 seconds, and the appearance is visually inspected. The criteria for the determination are as follows.

：: Some discoloration is observed in the protective film portion, but there is no practical problem.

×: The protective film portion is softened, largely deformed or peeled, and has a practical problem.

(2) Heat-resistant stiffness test of protective layer The capacitor is immersed in a 260 ° C molten solder bath. After a lapse of 10 seconds, the degree of softening of the protective layer is observed by, for example, pinching with tweezers or the like in a solder bath. The criteria for the determination are as follows.

 ：: The protective film portion is not damaged at all.

×: There is a trace of softening of the protective layer such as a trace of tweezers on the protective film portion, and there is a practical problem.

(3) Humidity degradation test of the capacitor The capacitor is sealed in a pressure vessel filled with water and aged in an oven heated to 155 ° C for 2 hours. Remove the capacitor and inspect it visually. The criteria for the determination are as follows.

 ：: There is no change in appearance, and the strength is sufficient.

×: No change in appearance, but easily peeled or brittle.

EXAMPLES The present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 (1) Preparation of Unstretched Polyphenylene Sulfide Sheet In an autoclave, sodium sulfide (32.6 kg, 250 mol, containing 40 wt% of crystallization water), sodium hydroxide 100 g, sodium benzoate 36.1 kg (250 mol), and N- Methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP) 79.
After 2 kg was charged and dehydrated at 205 ° C., 37.5 kg (255 mol) of 1,4 dichlorobenzene (abbreviated as p-DCB) and NMP2
0.0 kg was added and reacted at 265 ° C. for 4 hours. The reaction product was washed with water and dried to obtain 100 mol% of p-phenylene sulfide.
21.1 kg (78% yield) of poly-p-phenylene sulfide having a melt viscosity of 3100 poise.

0.05% by weight of calcium stearate was added to this composition and melted at 310 ° C. with an extruder having a diameter of 40 mm.
It is filtered through a 95% cut filter using metal fibers and has a pore diameter of 10μm, then extruded from a T-die having a linear lip with a length of 400mm and a gap of 1.5mm, cast on a metal drum whose surface is kept at 25 ° C, and cooled and solidified. Then, an unstretched polyphenylene sulfide sheet having a thickness of about 25 μm was obtained. This is PPS-NO
-1. The orientation degree of PPS-NO-1 is Through = 0.89, Ed
ge = 0.94, End = 0.91, and it was substantially unstretched.
In addition, the relative crystallization index of this sheet was 1.2, and the crystallization temperature upon heating was 135 ° C.

(2) Manufacture of capacitors Biaxially-stretched PPS film (“TORELINA” manufactured by Toray Industries, Inc.
A biaxially-stretched PPS film with adhesive (hereinafter referred to as PPS-BO-1) with an epoxy-based adhesive applied to one side with a theoretical value of 3 μm on one side with a nominal thickness of 25 μm) is slit to a width of 4.7 mm.
Five turns were wound around a drum having a diameter of 600 mm so that the adhesive layer was on the outside. PPS-NO-1 was slit on the drum to a width of 4.7 mm, and wound five turns around a drum having a diameter of 600 mm. further,
On top of this, an aluminum-evaporated biaxially stretched PPS film for capacitors (“MC Torelina” manufactured by Toray Industries, Ltd., nominal thickness 2.5μ)
m, film width 4.5mm, margin 0.5mm), left margin and right margin one by one, superimposed with a shift of 0.2mm, wound 1000 turns, and PPS-NO-1 on it again Was wound 5 turns, and a PPS-BO-1 film with an adhesive was wound 5 turns so that the adhesive layer came inside. From the outside of this large diameter wound body, tighten a cylindrical ring with a heater so as to cover it, tighten it so that a pressure of 3 kg / cm ² is applied in the film thickness direction, and simultaneously heat the ring to 180 ° C. Heat molding for 5 minutes. Further, metallicone was sprayed on both end surfaces to form external electrodes, and then the ring was removed. The resulting structure was cut at two opposite locations to obtain a semicircular capacitor mother element.

The obtained capacitor mother element was cut into a length such that the capacitance became 0.1 μF to obtain a capacitor element. After the cut surface of the element was protected by applying an epoxy resin, it was placed in an oven heated to 200 ° C., heat-treated for 2 hours, and the surface of the metallikon was polished to obtain a multilayer chip capacitor. This is referred to as a capacitor A. Table 1 shows the evaluation results of the capacitor A.

Example 2 Aluminum-evaporated biaxially-stretched PPS film for capacitors (“MC Torelina” manufactured by Toray Industries, Inc., nominal thickness 2.5 μm, film width 4.5 mm, margin 0.5 mm) on a flat mandrel having a length of 320 mm and a width of 30 mm The left and right margins are stacked one on top of each other with a 0.2mm shift, wound 1000 turns, and the film thickness is increased by a parallel plate heating press heated to 180 ° C from above and below the wound body. Pressing was performed for 5 minutes while applying a pressure of 30 kg / cm ² in the vertical direction.
After pressing, metallicon was sprayed on both end surfaces to form external electrodes, and then cut at two opposing locations to obtain rod-shaped capacitor mother elements.

The obtained capacitor mother element was cut into a length such that the capacitance became 0.1 μF to obtain a capacitor element.

PPS-NO-1 obtained in Example 1 was slit to a width of 4.7 mm,
Five turns are wrapped around the outer periphery of the obtained capacitor element (four sides excluding the metallized surface), and the PPS-BO-1 with the adhesive obtained in Example 1 is further wrapped two turns, and then the end of the tape is adhesive tape. After pressing temporarily with a parallel plate heating press machine heated to 200 ° C again and applying a pressure of 30 kg / cm ² in the thickness direction of the dielectric film for one hour, the surface of the metallikon part is polished. A multilayer chip capacitor was obtained. This is referred to as a capacitor B. Table 1 shows the evaluation results of the capacitor B.

Example 3 A PPS-NO film was obtained in the same manner as in Example 1. However, at this time, the casting speed was reduced to half and the thickness was set to 50 μm. This is designated as PPS-NO-2.

Separately from this, a biaxially stretched PPS film ("Torelina" manufactured by Toray Industries, Inc., nominal thickness 50 μm) was prepared. this,
PPS-BO-2.

Both PPS-BO-2 and PPS-NO-2 were slit to a width of 4.7 mm, and were first overlapped so that PPS-BO-2 was on the inside and wound around a drum having a diameter of 600 mm for 2 turns. further,
On top of this, an aluminum-evaporated biaxially stretched PPS film for capacitors (“MC Torelina” manufactured by Toray Industries, Ltd., nominal thickness 2.5μ)
m, film width 4.5mm, margin 0.5mm), left margin and right margin, each with a 0.2mm shift, superimposed, wound 1000 turns, and then PPS-BO-2 again Is on the outside and PPS-BO-2
PPS-NO-2 was overlapped and wound for 2 turns. From the outside of this large diameter wound body, tighten a cylindrical ring with a heater so that it can be covered, and 3 kg /
Tighten the ring to 180 ° C while applying pressure of cm ²
And molded by heating for 5 minutes. Further, metallicon was sprayed on both end faces to form external electrodes, and then the ring was removed, and cut at two opposite locations to obtain a semicircular capacitor mother element.

The obtained capacitor mother element was cut into a length such that the capacitance became 0.1 μF to obtain a capacitor element. After the cut surface of the element was protected by epoxy powder coating, it was placed in an oven heated to 200 ° C. and heat-treated for 2 hours, and the surface of the metallikon was polished to obtain a multilayer chip capacitor. This is referred to as a capacitor C. Table 1 shows the evaluation results of the capacitor C.
Shown in

Example 4 PPS-NO-2 film obtained in Example 3 (thickness: 50 μm)
On both sides of the substrate, heat-laminated a biaxially stretched PPS film (“Torelina” manufactured by Toray Industries, Inc., nominal thickness 25 μm)
A laminated film having a PPS-NO / PPS-BO configuration was obtained.

An epoxy-based adhesive was applied to one side of the laminated film to a theoretical thickness of 3 μm to obtain a laminated film with an adhesive.

This laminated film with adhesive is slit to a width of 4.7 mm, and a 5 mm-diameter drum is placed so that the adhesive layer is on the outside.
Turn wound. Furthermore, a biaxially-stretched PPS film of aluminum vapor for a capacitor (“MC MC” manufactured by Toray Industries, Inc.)
Torelina ”, nominal thickness 2.5μm, film width 4.5mm, margin 0.5mm) left margin and right margin 1 each
The sheets were stacked with a shift of 0.2 mm, wound 1000 turns, and a laminated film with an adhesive was further wound thereon for 5 turns so that the adhesive layer was on the inside.

With the obtained film roll wound around the drum, 18
Heat treatment in a hot air oven at 0 ° C for 1 hour, apply metallikon to the end face of the wound body, and then
The wound body was cut at several places to obtain a semicircular capacitor mother element.

The obtained capacitor mother element was cut into a length such that the capacitance became 0.1 μF to obtain a capacitor element. After the cut surface of the element was protected by epoxy powder coating, it was placed in an oven heated to 200 ° C. and heat-treated for 2 hours, and the surface of the metallikon was polished to obtain a multilayer chip capacitor. This is referred to as a capacitor D. Table 1 shows the evaluation results of capacitor D.
Shown in

Comparative Example 1 A capacitor was produced in the same manner as in Example 1, except that the protective film portion was made only of the biaxially stretched PPS film with adhesive (PPS-BO-1) without using PPS-NO. However,
PPS-BO-1 was wound 10 turns to equalize the thickness of the protective layer. This is referred to as a capacitor E. Capacitor E
Table 1 shows the evaluation results.

Comparative Example 2 Example 1 except that PPS-NO-1 was used as the protective film portion
A capacitor was prepared in the same manner as in Example 1. However, PPS-N
O-1 was wound 10 turns to equalize the thickness of the protective layer portion. This is referred to as a capacitor F. Table 1 shows the evaluation results of the capacitor F.

Comparative Example 3 The protective film was a heat-adhesive polyimide film (Toray
DuPont "Kapton" F type, film thickness 25
μm) in the same manner as in Comparative Example 1. This is referred to as a capacitor G. Table 1 shows the evaluation results of the capacitor G.

Comparative Example 4 A capacitor was formed in the same manner as in Comparative Example 1 except that a protective film was a polyester film (“Lumirror” manufactured by Toray Industries, Inc., film thickness: 25 μm). This is referred to as a capacitor H. Table 1 shows the evaluation results of the capacitor H.

From the above results, it can be seen that the capacitor of the present invention is a capacitor having both excellent solder resistance and humidity resistance.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating the structure of a capacitor element obtained according to Example 1 of the present invention. 1: Protective layer of PPS-BO film with adhesive (outer layer) 2: Protective layer of PPS-NO film (inner layer) 3: Capacitance generating part 4: External electrode (metallicon)

Claims (2)

(57) [Claims] 1. A film capacitor having a capacity generating portion obtained by winding or laminating alternately a dielectric film and an electrode, and a protective layer formed by superposing a plastic film provided on the outside thereof. In
The outermost layer of the protective layer is made of a biaxially oriented polyphenylene sulfide film, and has a thickness of 20% with respect to the total thickness of the protective layer.
A film capacitor comprising a substantially unstretched polyphenylene sulfide film having the above thickness. 2. The film capacitor according to claim 1, wherein the capacitor is a multilayer film capacitor.