JPH0770426B2 - Capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a capacitor used in electronic equipment and electric equipment,
Among them, it relates to film chip capacitors.

2. Description of the Related Art In recent years, efforts have been made to increase the functionality and size of electronic devices and electric devices, and the electronic components used for these devices have become light, thin, short, and small. A typical example is chipping. Therefore, the surface mounting method, which is different from the conventional one, has been rapidly progressed as the method of mounting the components on the printed circuit board which constitutes the circuit. In this method, parts are fixed on one side or both sides of the substrate with an adhesive or cream solder, and the components are passed through a solder bath or a high-temperature furnace for soldering. Therefore, the component body is directly exposed to a high temperature, and the temperature applied to the component body becomes much higher than that of the conventional leaded component in which only the lead wire is immersed in the solder bath. For example, in the case of a film capacitor, the internal temperature of the conventional leaded type is 100 to 130 ° C when only the lead wire is soldered, whereas the internal temperature of the chip film capacitor is
It is 210-240 ℃, about 100 ℃ higher. Furthermore, in order to miniaturize the equipment, the space inside the equipment is reduced and the board configuration density is increased, so heat generated by active electronic components (ICs, transistors, diodes, etc.) is The temperature rises.

As described above, the chip component is stricter in temperature than the conventional leaded component. Film capacitors
Polyethylene terephthalate notebook (hereinafter PE
Although abbreviated as T) and polypropylene (hereinafter abbreviated as PP) were used, a new plastic material having excellent heat resistance has been desired because of difficulty in heat resistance.

Recently, polyphenylene sulfide (hereinafter abbreviated as PPS) and polyphenylene oxide (hereinafter abbreviated as PPO) have been developed as heat resistant dielectric materials. PPS and PPO are PET, P
It has better heat resistance than P and also has excellent electrical characteristics, which is one of the major characteristics of film capacitors.

Conventionally, a laminated type film chip capacitor was obtained by forming a vapor deposition electrode made of aluminum on both surfaces of a dielectric film made of polyphenylene sulfide, and further making a thin coating dielectric made of polyphenylene oxide on both surfaces thereof. After stacking hundreds of long and narrow double-sided vapor deposition and double-sided coating films, aluminum bronze is formed in the lower layer and a metallikon layer made of tin-lead alloy is formed in the upper layer to obtain electrical connection from the vapor deposition electrodes, and then cut to a certain size. Then, a laminated film capacitor element was obtained by welding the external electrodes, pouring epoxy resin into a mold of a certain size, and curing by heating to perform mold exterior, and processing the external electrodes to obtain a laminated film chip capacitor.

Problems to be Solved by the Invention After laminating this metallized film, a metal layer as an electrode lead-out portion is formed on the end face. At this time, since the electrodes are independent of each other, a desired capacitance cannot be obtained unless the electrode and the metal layer are bonded even in one of the electrodes. Therefore, in this type of film capacitor, improving the coupling state between the electrode and the electrode lead-out portion is the most important factor for stabilizing the electrical characteristics of the capacitor. The electrode extension is
Usually, it is formed by metal spraying (hereinafter referred to as metallikon). The metallikon is for injecting compressed air to molten metal and blowing the compressed air as molten spheres onto the end faces to deposit the molten spheres. At this time, it is known that an alloy layer is formed between the molten sphere reaching the electrode and the electrode. However, the higher the melting point of the sprayed metal is with respect to the melting point of the electrode, the more the electrode is melted, and thus the bonding property is improved. Is generally good.

However, since zinc is used as the sprayed metal of the conventional film capacitor, the melting point is low and the electrode metal can be alloyed only slightly.

On the other hand, in order to realize the miniaturization of the film capacitor, the film and the lacquer film are about 1 μm. As a result, the contact area between the electrode and the sprayed metal becomes very small, so that the electrical coupling between the electrode and the electrode extraction layer becomes more disadvantageous.

In this conventional film capacitor, it is not preferable in terms of characteristics to reduce the thickness of the dielectric and reduce the size thereof, because the electrical coupling between the electrode and the electrode lead layer is significantly deteriorated.

Further, it is well known that when zinc is used in a high temperature and high humidity atmosphere, it has a problem of losing electrical connection with the electrode in a short time due to corrosion of zinc itself.

On the other hand, when a copper-aluminum alloy, which has a very high melting point for the electrode and is weather resistant and chemically stable, is used as the metal spray material, the heat of the molten spheres causes the end face film and the lacquer film to shrink and There is a problem that deformation occurs, and the electrical coupling between the electrode and the electrode lead-out layer deteriorates.

Problems to be Solved by the Invention In addition to the miniaturization of the metallized film capacitor as described above, there has been a problem that the electrical coupling between the electrode and the electrode extraction layer is deteriorated due to the material of the electrode extraction layer. .

The present invention is intended to solve the above conventional problems,
It aims to improve the electrical characteristics of a film capacitor to which metallikon is applied while making the film capacitor smaller.

Means for Solving the Problems In order to achieve this object, a capacitor according to the present invention has a first layer of an electrode lead portion in which a copper-zinc matrix having a zinc component ratio of 5% or more and 60% or less in a copper-zinc alloy is used. Second, composed of alloy
The layers are composed of solder.

Action With this configuration, the electric connection between the electrode and the electrode lead portion can be firmly and stabilized without thermally affecting the capacitor element, particularly the film and the lacquer film,
Moreover, the electrode lead-out portion itself can be used as a connecting portion to another electric circuit.

Examples The contents of the present invention will be described in more detail based on examples below.

FIG. 1 is a perspective view showing a cross section of a part of a laminated film chip capacitor according to an embodiment of the present invention.

The vapor deposition electrodes 2 and 3 made of aluminum having a thickness of about 400 Å are provided on both sides of the dielectric film 1 made of a PPS film having a thickness of 2 μm and having a thickness of about 1 μm and the coating dielectric made of PPO having a thickness of about 1 μm Form body films 4 and 5 to make a film with double-sided vapor deposition and double-sided coating, then stack 500 sheets of the double-sided vapor deposition and double-sided coating films, and pull out the electrode from the vapor-deposited electrodes 2 and 3. The parts 6 and 7 were formed to obtain a long strip capacitor. After that, after cutting into a unit capacitor having a width of about 4.6 mm, two cut surfaces are formed on a polyimide film 8a having a thickness of 25 to 75 μm and a thickness of 15 to 50 μm as shown in FIG.
After attaching a thermosetting sheet called a prepreg sheet on which a μm epoxy resin layer 8b is formed, it is heat-cured to form an exterior member 8 with a capacitance of 0.10 μF and a height of 2 mm and a width.
A laminated film chip capacitor with a length of 6 mm and a length of 5 mm was obtained.

Here, as shown in FIG. 1 and FIG.
Protective layers 9 and 10 are provided above and below the capacitive portion where the double-sided coated films are laminated to protect the capacitive portion and to reinforce the entire portion. The protective layers 9 and 10 are formed by laminating a film in which a resin film 12 made of PPO is formed on both surfaces of a resin film 11 such as a PPS film, similar to the film forming the capacitive portion. And the exterior material 8
Has a width that covers all the end faces of the capacitance portion and is arranged over the entire region or a partial region of the end faces of the protective layers 9 and 10. As an example, the protective layers 9 and 10 having a thickness of 0.15 mm are provided, and the width of the exterior material 8 is set to be 0.10 mm shorter than the entire thickness of the protective layer 9.10. The exterior member 8 also has such a length that it is arranged over the entire area or a partial area of the end surface of the electrode lead-out portions 6, 7 on the cut surface side.

Further, the protective layers 9 and 10 and at least the coating dielectric film 4,5 and the resin film 12 of the capacitive portion are colored brown to blackish brown by crosslinking a resin such as PPO which is a constituent material. . Also, with respect to the exterior member 8, the surface layer is brown to
It is colored blackish black.

Furthermore, the electrode lead-out portions 6 and 7 have a first layer 6a and 7a formed by spraying a copper-zinc alloy with a thickness of 0.15 mm and a second layer 6a and a second layer 6a formed by spraying solder with a thickness of 0.25 mm. 7b and. In the first layers 6a, 7a and the second layers 6b, 7b of the electrode lead-out portions 6, 7, the first layers 6a, 7a have a thickness of 0.10 mm to 0.20 mm.
Therefore, it is preferable to use a copper-zinc alloy having a zinc component ratio of 5% to 60% by weight, and the second layers 6b and 7b have a thickness of
It is preferable to use a solder (Sb-Pb-Sn alloy) having a liquidus temperature of 195 ° C to 215 ° C and a solidus temperature of 189 ° C with a thickness of 0.20 mm to 0.40 mm. The composition of this solder is Sb3%, Pb67%, Sn30%
I used the one.

FIG. 4 shows the charge and discharge test of the capacitors of the present example in which the zinc component ratio was changed from 5% by weight to 10% by weight, and the tan of this capacitor was measured.
The number of times until δ reaches 1.5 times the initial value (tan δ defect occurrence frequency) is shown.

As is clear from this result, when the zinc component ratio is 75% by weight or more, the tan δ defect occurs at a small number of times.

On the other hand, when the content ratio of zinc is less than 5% by weight, the melting point becomes high and the deterioration of the film on the bridge surface is promoted, so that the charge / discharge characteristics are significantly deteriorated. However, the zinc component ratio is 5 to 60 by weight.
It can be seen that, even if an ultrathin film dielectric having a thickness of about 1 μm is used in terms of weight%, very excellent charge / discharge characteristics are exhibited.

FIG. 5 shows the case where the zinc component ratio is changed as in FIG.
The tan δ value and the reduction rate of the electrostatic capacity at 1000 hours at a humidity resistance load test of 60 ° C and 95% RH are shown.

According to this, since the zinc component ratio is likely to corrode to a high degree, the variation in the tan δ value becomes large, and when the zinc component ratio exceeds 60% by weight, electrical contact becomes insufficient,
Although it causes an extreme decrease in capacitance, when the zinc content is less than 60% by weight, it exhibits excellent weather resistance.

From the above results, in order to make the electrical contact between the electrode and the electrode lead-out portion of the laminated film capacitor shown in this example stable and strong and to obtain further excellent weather resistance, copper-zinc was used. A copper-zinc master alloy having a zinc component ratio of 5% by weight to 60% by weight in the alloy may be used.

The composition ratio of copper-zinc is 30% by weight-70% by weight, respectively.
Also, the same effect as described above can be obtained with a commercially available alloy obtained by adding 2-3% by weight of a third element such as Sn, Al, or Ni to a 40% -60% by weight copper-zinc based master alloy. .

FIG. 6 and FIG. 7 show a state in which the laminated film chip capacitor according to this embodiment is mounted on a printed board. As shown in FIGS. 6 and 7, a chip capacitor 15 is placed on a printed circuit board 14 having a wiring pattern 13, and soldering by dipping in a solder bath or soldering by a reflow method is performed. The electrode lead-out portions 6 and 7 of the capacitor 15 are connected to the wiring pattern 13 by solder 16. At this time, the bottom center portion 15a of the chip capacitor 15
When the chip capacitor 15 is placed on the printed circuit board 14, a space is formed between the bottom center portion 15a of the chip capacitor 15 and the printed circuit board 14 by making the shape curved inward. The adhesive 17 for temporarily fixing 15 disposed on the printed circuit board 14 does not laterally protrude, and the connection between the wiring pattern 13 and the electrode lead portions 6, 7 is not hindered.

Compared with the conventional laminated film chip capacitors (height: 3 mm, width: 7 mm, length: 5 m), the laminated film chip capacitors obtained according to this example are as follows:
The volume was reduced by about 43% and the dimensional accuracy was the same. In addition, 100 laminated film chip capacitors were adhered to a printed wiring board and soldered at a temperature of 260 ° C for 5 seconds, and the result was that the cracking failure rate of the exterior was 0% and the change in capacitance was within ± 1%. Met.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

In other words, it is possible to establish a firm and stable electrical connection between the vapor deposition electrode of the element and the electrode lead-out portion without giving a thermal effect to the capacitor element. Even when the portion itself is used for connection to the outside, the effect that the solderability is good can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a part of a laminated film chip capacitor according to an embodiment of the present invention in section, FIG. 2 is a perspective view showing a sheet used for the capacitor, and FIG. 3 is a schematic view of the capacitor. Fig. 4 and Fig. 5 are cutaway views showing the number of tan δ defects in the charge and discharge test, the capacity decrease rate in the moisture resistance load test, and the tan δ value, respectively, when the zinc component ratio in the electrode extraction part is changed. Characteristic diagram showing
6 and 7 are a perspective view and a side view showing a state in which the capacitor is mounted on a printed board. 1 ... Dielectric film, 2,3 ... Vapor-deposited electrode, 4,5 ... Coating dielectric film, 6,7 ... Electrode extraction part, 6a, 7a ... 1st
Layer, 6b, 7b ... Second layer, 8 ... Exterior member, 8a ... Polyimide film, 8b ... Epoxy resin layer, 9,10 ... Protective layer, 11 ... Resin film, 12 ... Resin film, 13 …… wiring pattern, 14 …… printed circuit board, 15 …… chip capacitor, 15a …… bottom center, 16 …… solder, 17 …… adhesive.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenji Ishida Kenji Ishida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kenji Kuwata Kazoma 1006 Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Nobuyuki Kume 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Noriyuki Sugiura, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference JP 61 -119023 (JP, A) Japanese Patent Publication Sho 53-29218 (JP, B2)

Claims (1)

[Claims] 1. A film capacitor element is formed by forming an electrode lead-out portion on an end face, and the first layer of the electrode lead-out portion has a zinc component ratio of 5% or more in a copper-zinc alloy.
% Or less of a copper-zinc master alloy and a second layer of solder.