JP3173435B2 - Laser trimmable condenser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser trimmable capacitor used for electric and electronic equipment.

[0002]

2. Description of the Related Art In a portable information device such as a cellular phone or a pager which has recently been used, a variable-capacitance capacitor is used for adjusting the frequency setting of an oscillation circuit. Further, recently, instead of the conventional mechanical trimmer capacitor, a laser trimmable capacitor which does not have a capacity shift due to a change with time or an impact at the time of dropping has been used more and more. FIG.
1 shows a conventional laser trimmable capacitor using ceramic as a dielectric. The structure has an upper electrode 1 that can be removed by trimming with a laser on the upper part, and obtains a predetermined capacitance between the lower electrodes 3-a and 3-b inside the device. The external electrode 4 is connected to the lower electrodes 3-a and 3-b from the side surface of the element and covers the lower and upper parts of the element. Further, the upper electrode 1 has a gap of 0.2 to 0.3 mm between the upper electrode 1 and the overlying portion of the external electrode on the plane of the element, and also from the end of the element perpendicular to the opposing external electrode. 0.2 ~
It is formed inside 0.3 mm.

According to this structure, the capacitance of the capacitor is generated between the upper electrode 1 and the lower electrodes 3-a and 3-b. Only a capacitance corresponding to an electrode area of / 4 or less is generated.

[0004]

[0005]

[0006]

[0007]

However, there is a high demand for a portable information device such as a cellular phone or a pager using a laser trimmable capacitor to reduce the size and weight. .6 × 0.
An object of 8 mm or 1.0 × 0.5 mm is required.

To cope with this, it is necessary to further reduce the size of the laser trimmable capacitor and increase the capacity.

However, also in the capacitor of FIG. 3, the capacitance is the series combined capacitance of the upper electrode 1 and the two capacitors generated between the lower electrodes 3-a and 3-b, and is 1 / the area of the upper electrode 1. The point that only a capacitance corresponding to an electrode area of 4 or less is generated is the same as that of the ceramic capacitor.

On the other hand, a structure shown in FIG. 4 can be considered as a structure proposal for miniaturization based on a ceramic capacitor.

In FIG. 1, reference numeral 1 denotes an upper electrode, which is directly connected to an external electrode 4 on one side. Further, it has a lower electrode 3 with the dielectric 2 interposed therebetween. In this structure, the capacitor capacitance is generated only at one opposing portion of the upper electrode 1 and the lower electrode 3, and the structure of FIGS. 2 and 3 becomes a series combined capacitance of two capacitors, and is 1/1 of the area of the upper electrode 1. Compared to a case where only a capacitance corresponding to an electrode area of 4 or less is generated, a small-sized and large-capacity capacitor can be obtained.

However, in manufacturing the ceramic capacitor having the structure shown in FIG. 4, a silver paste as a main component constituting an external electrode and an Ag-paste forming an upper electrode and a lower electrode are used.
There is a problem of electrical corrosion between dissimilar metals with the Pd paste. Also in this structure, two external electrodes are exposed on the upper part, and the laser power for trimming the upper electrode needs the same power as processing the copper pattern of the circuit board on which the element is mounted. From that,
In order not to damage the circuit board, it is necessary to finish the laser trimming on the element without fail. Therefore, the upper electrode should be 0.2 to 0.2 mm from the end of the element perpendicular to the opposing external electrode.
As is clear from the fact that it is necessary to form the element within 0.3 mm, when the size of the element is reduced, the expansion of the capacity contribution area of the capacitor is insufficient.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem in increasing the capacity of a conventional laser trimmable capacitor, and provides a thin, highly reliable laser trimmable capacitor using an organic film as a dielectric. The purpose is to:

[0014]

Means for Solving the Problems] laser trimmer Burukon Den Sa of the present invention, two external power toward lower surface from the side
A marker is provided on the entire upper surface of the substrate 5 on which the poles 4 are provided.
Are electrically insulated by the
And a lower electrode 3-a electrically connected to the
A lower electrode 3 made of a pole 3-b, on the lower electrode 3
Dielectric 2 covering the entire surface of the upper part of the external electrode 4
And the lower electrode 3-a and the capacitor 2
In addition to forming a capacitor, the capacitor
The upper electrode 1 electrically connected to the lower electrode 3-b
The surface of the upper electrode 1 has no external electrode 4 exposed.
I'm trying. The capacitor capacitance is generated at one opposing portion of the upper electrode 1 and the lower electrode 3.

[0015] With the structure having no exposure of the external electrodes 4 prior SL upper electrode 1 surface, expanding the length of the upper electrode by the amount having no external electrode, and the upper electrode,
Output of fundamental wave and second harmonic of YAG laser 100m
By using a material that can be trimmed at w or less, the width of the upper electrode is increased to a dimension perpendicular to the inter-electrode direction of the device.

Due to the combination of the capacitor capacitance generating structure and the effect of enlarging the electrode area, a sufficiently large capacitor capacitance can be obtained even if the size is reduced.

Further, an organic dielectric having a dielectric thickness of 10 μm or less is used, and the substrate has a thermal expansion coefficient of 20 to 60 ×.
By making the resin or organic film of 10-6 / ° C,
Capacitors with a thickness of 0.4 mm or less can be made unbreakable, and even if a glass epoxy multilayer board is used for the circuit board, stress due to temperature changes during mounting and use is small, cracking of the capacitor, Provide a highly reliable capacitor that does not cause solder cracks.

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows the structure of the laser trimmable capacitor of the present invention.

In FIG. 1, the upper electrode 1 is
Together with a, the capacitance of the capacitor is formed with the dielectric 2 interposed therebetween.
Further, the upper electrode 1 is electrically connected to the lower electrode 3-b through the connection portion 7.

The lower electrodes 3-a and 3-b are electrically insulated by a margin 8. Also, the dimension of 3-b is limited to the minimum necessary dimension for forming the connection portion 7.

In one embodiment of the present invention, the connecting portion 7 is removed in several places in a circular shape having a diameter of 0.1 mm, and the upper electrode is formed thereon by sputtering.
The dimension of -b was set to the minimum dimension of 0.2 mm.

The lower electrode 3-a is a part for forming the capacitance of the capacitor, and the lower electrode 3-a and the margin 8 are determined from the length of the product.
Take the maximum dimensions excluding the dimensions of the upper electrode and the clearance with the product outer shape of the upper electrode. Here, the clearance is a gap for preventing the upper electrode 1 from protruding from the end face of the product and not being connected to the external electrode by soldering at the time of mounting. In the embodiment of the present invention, the clearance may have a small dimension of 0.05 mm or less. .

Due to the configuration of the lower electrodes 3-a and 3-b and the upper electrode 1, no external electrode is provided on the upper surface of the product.
The capacitance of the capacitor can be formed by sandwiching the dielectric 2 between the upper electrode 1 and the lower electrode 3-a.

According to this structure, the capacitance of the capacitor is not generated between the upper electrode 1 and the lower electrode 3-b, but is one capacitor between the upper electrode 1 and the lower electrode 3-a.
2 and 3 become a series combined capacitance of the two capacitors, which is three times or more even with the same product size as compared with the point that only a capacitance corresponding to an electrode area of 1/4 or less of the area of the upper electrode 1 is generated. You can get the capacity.

The upper electrode 1 functions to trim the electrode area by a laser beam and change the capacitance of the capacitor. This metal is conductive for obtaining a high Q value in a high frequency region and workability by the laser beam. In consideration of the above, in one embodiment of the present invention, it is formed of an aluminum sputtered metal having a thickness of 0.2 to 0.25 μm.

The upper electrode 1 is formed of a thin film metal having a thickness of 0.1 to 0.5 micron, and the same effect can be obtained even if the material is gold, silver, aluminum, copper or a material containing these as main components. Is obtained.

According to the configuration of the upper electrode, the trimming is performed with the output of the fundamental wave and the second harmonic of the YAG laser.
mw or less.

In FIG. 1, the dielectric 2 has a frequency of 1 MHz or more.
An organic material having a dielectric loss of 1 GHz or less and a thickness of 10 μm or less at 1 GHz is PPS in one embodiment of the present invention, but the same effect can be obtained even with syndiotactic polystyrene. can get.

The dielectric is formed by lower electrodes 3-a and 3-
The lower electrode covering the upper portion of the b all surfaces are disposed so as not to appear in the upper portion of the dielectric junction.

Further, in FIG. 1, the substrate 5 is a resin or an organic film having a coefficient of thermal expansion of 20 to 60 × 10 −6 / ° C. In one embodiment of the present invention, it is made of polyimide.

Thus, even when the thickness of the element is 0.4 mm or less, cracking does not occur due to its flexibility, in combination with the organic film constituting the dielectric material.

With this configuration, even when a glass epoxy substrate is used as a circuit board, the thermal expansion coefficient of the element substrate is closer to that of the circuit board than that of a conventional substrate made of ceramic, so that the temperature at the time of mounting and use is reduced. It has an effect that the stress due to the change is small and the capacitor is not cracked or the solder is not cracked.

In FIG. 1, the protective film 6 is formed by mounting the upper electrode 1 formed of the thin film metal having a thickness of 0.1 to 0.5 μm and a dielectric made of an organic material having a thickness of 10 μm or less. In the present invention, an insulating protective film made of an acrylic resin is provided.

In the present invention, the material of the protective film is an acrylic resin. However, any other insulator having good laser beam transmission properties, such as SiO2, may be used.

(Embodiment) An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, the laser trimmable capacitor of the present invention has a size of 1.6 mm × 0.8 mm.

The upper electrode 1 is made of Al having a thickness of 0.2 μm.
It is a sputtered thin film, and the dielectric 2 is PPS having a thickness of 1.5 microns.

The lower electrodes of 3-a and 3-b are obtained by plating nickel and gold on copper, and the dimension of 3-a is 1.2 mm for a product length of 1.6 mm.

With this structure, the laser trimmable capacitor of the present invention has a size of 1.6 mm × 0.8 mm and a capacitance of 17 pF. This is because the dielectric material invented by the present inventors in FIG. Conventional laser-trimmable capacitor using film is 3.2mm x 2.5mm and capacity is 21pF
Compared to that, it has realized much smaller size.

The Q value is equivalent to that of the structure shown in FIG.
20 or more can be obtained at 00 MHz.

The laser power required for laser trimming is the same as that of the structure shown in FIG. 3, and processing can be performed at 20 to 60 mW in the case of a second harmonic output of a YAG laser.

The substrate 5 is an organic film having a polyimide thickness of 75 μm and a coefficient of thermal expansion of 20 to 30 × 10 −6 / ° C.

The protective film 6 is an acrylic resin film having a thickness of 10 to 20 μm and protects the upper electrode 1, but has a good laser beam transmittance and does not affect the laser trimming.

Next, referring to FIG. 5 and FIG. 6, the state of mounting and trimming a conventional ceramic capacitor and the state of mounting and trimming a laser trimable capacitor according to the structure of the present invention are compared. The reason why the structure can be reduced in size and increased in capacity due to its trimming property will be described.

FIG. 4 schematically shows a state in which a laser trimming capacitor made of a conventional ceramic capacitor is mounted on a circuit board and laser trimming is performed.

In order to increase the capacitance or reduce the size, there is a method of reducing the thickness of the dielectric or increasing the size of the upper electrode.

In the ceramic capacitor, the disadvantages of increasing the size of the upper electrode include the necessity of a gap with the external electrode exposed above the element and the fact that the laser power for trimming the upper electrode is about 1 W. Since the same power is required to process the copper pattern of the mounted circuit board 10, it is necessary to start and end the trimming by the laser beam 9 on the element without fail to damage the circuit board 10. Therefore, the upper electrode should be 0.2 to 0.3 from the end of the element perpendicular to the opposing external electrode.
There is a limit that only about 50% of the element area can be actually used from the two points that it needs to be formed inside the millimeter.

FIG. 6 schematically shows a state where the laser trimming capacitor according to the structure of the present invention is mounted and laser trimming is performed.

According to the structure of the present invention, since the external electrode is covered with the dielectric and is not exposed to the upper part, the upper electrode can be expanded in the direction of the opposing external electrode to the length of the element. Further, according to the configuration of the upper electrode of the present invention, since the trimming can be performed with the output of the fundamental wave and the second harmonic of the YAG laser of 100 mw or less, the width of the element in the direction perpendicular to the direction of the external electrode opposed to the upper electrode is full. As shown in the figure, even if laser light is applied to a circuit board other than the element and trimming is started, there is no damage to the circuit board. Therefore, the laser trimmable capacitor of the present invention can increase the area of the upper electrode to almost the same size as the element.

[0057]

As described above, according to the present invention, from the side
On a substrate 5 on which two external electrodes 4 are provided over the lower surface
Provided on the entire surface and electrically insulated by the margin 8
And are electrically connected to the external electrodes 4 respectively.
Electrode composed of a lower electrode 3-a and a lower electrode 3-b
3 and the upper part of the lower electrode 3 and the upper part of the external electrode 4
The dielectric 2 covering the entire surface and the lower electrode 3-a are guided together.
In addition to forming the capacitance of the capacitor with the
Electrically connected to the lower electrode 3-b via the connection portion 7 inside the body 2
A conductive upper electrode 1 and an upper electrode 1
By so that no exposure of the electrode 4, as compared with the conventional structure can obtain a large capacity for the same upper electrode area, the area of Mataue portion electrode to substantially the same size as the area of the element Because it can be expanded, the capacity can be increased or the size can be reduced.

Even if the thickness of the element is 0.4 mm or less, no crack is generated due to its flexibility. In addition, since the thermal expansion coefficient of the element is close to that of the circuit board, it is possible to provide a highly reliable capacitor that has the effect of preventing cracking of the capacitor due to stress due to temperature change during mounting and use and cracking of the solder. it can.

[Brief description of the drawings]

1A is a plan view of a laser trimmable capacitor according to an embodiment of the present invention, FIG. 1B is a cross-sectional view, and FIG.

2A is a plan view of a conventional ceramic laser trimmable capacitor, FIG. 2B is a cross-sectional view, and FIG.

3A is a plan view of a conventional organic film laser trimmable capacitor, FIG. 3B is a sectional view thereof, and FIG.

FIG. 4A is a plan view of a miniaturization plan of a ceramic laser trimmable capacitor, FIG. 4B is a cross-sectional view, and FIG.

FIG. 5 is a diagram showing a state in which a conventional laser trimmable capacitor is mounted and trimmed.

FIG. 6 is a diagram showing a state in which the laser trimmable capacitor of the present invention is mounted and trimmed.

[Explanation of symbols]

 1 Upper electrode 2 Dielectric 3 Lower electrode 4 External electrode 5 Substrate 6 Protective film 7 Connection between upper electrode and lower electrode 8 Lower electrode margin 9 Laser beam 10 Circuit board

Continuation of the front page (72) Inventor Nobuki Sunaru 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-34522 (JP, A) JP-A-3-12958 (JP JP-A-56-104430 (JP, A) JP-A-2-98911 (JP, A) JP-A-63-33619 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01G 4/00-4/40 H01G 13/00-13/06

Claims (4)

(57) [Claims] 1. Two external electrodes extending from a side surface to a lower surface.
The entire surface of the upper surface of the substrate (5) provided with (4) is provided.
And is electrically insulated by the margin (8).
And the lower electrodes electrically connected to the external electrodes (4), respectively.
Lower electrode comprising pole (3-a) and lower electrode (3-b)
(3), the upper part of the lower electrode (3) and the outer electrode (4).
A dielectric (2) covering the entire upper surface, and the dielectric (2) sandwiched together with the lower electrode (3-a);
A capacitor for forming a capacitor;
The lower electrode (3-b) through an internal connection (7);
And an upper electrode (1) which are electrically conductive, the said upper electrode (1) surface without exposure of external electrodes (4)
Laser trimmable capacitor which is adapted. 2. The upper electrode is formed of a thin metal having a thickness of 0.1 to 0.5 μm and capable of being trimmed at an output of 100 mw or less of a fundamental wave and a second harmonic of a YAG laser. 2. The laser-trimmable capacitor according to claim 1, comprising silver, aluminum, copper and a material containing these as main components. 3. The laser-trimmable capacitor according to claim 1, wherein the dielectric is an organic dielectric having a dielectric loss of 0.01 or less at 1 MHz to 1 GHz and a thickness of 10 μm or less. 4. A substrate for supporting a dielectric, an upper electrode and said external lead-out electrode has a coefficient of thermal expansion of 20 to 60 × 10
The laser trimmable capacitor according to any one of claims 1 to 3, which is a resin or an organic film having a temperature of ^-6 / C.