JPH1055933A - Trimming capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily trim, without causing the obtd. capacitance of a trimming capacitor to be dispersed by forming a particle-dispersed dielectric layer and opposed inner electrodes through this layer on the capacitor. SOLUTION: A capacitor 12 is laminarly formed in one surface of a multi- layer substrate 10 made of a (Ba, Sr, Ca)O-Al2 O3 -SiO2 glass and comprises a pair of opposed inner electrodes 14 with a dielectric layer 16 therebetween. The particles for efficiently absorbing the heat caused by the irradiated beam uses C particles which are dispersed in the dielectric layer 16. The capacitor 12 is irradiated with a laser beam 18 to trim the capacitance. Thus a region near the electrode cross point of the capacitor 12 on the board 10 is irradiated with the laser beam 18 to trim it, without dispersing the obtd. capacitance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trimming capacitor formed on, for example, a substrate of a hybrid IC or inside the substrate.

[0002]

2. Description of the Related Art To adjust (trim) the acquisition capacity of a trimming capacitor formed on or inside a substrate of a hybrid IC, a part of the internal electrode of the trimming capacitor is mechanically or physically removed, and the internal electrode is removed. This is done by changing the effective area. Here, as means for mechanically or physically removing a part of the internal electrode of the trimming capacitor, sand blast, laser, or the like is used.

[0003]

However, in such a conventional trimming method, a part of the internal electrode forming the trimming capacitor is mechanically or physically removed. There are inconveniences such as adhesion to wirings and electrodes formed on the surface of the substrate to lower the insulating properties of the portions and causing migration.

Further, in the conventional trimming method, since a part of the internal electrode forming the trimming capacitor is mechanically or physically removed, the trimming to reduce the acquisition capacity can be performed, but the trimming to increase the acquisition capacity is not possible. It is possible and the range that can be trimmed is limited.

Further, in the conventional trimming method, since the electrode is exposed at the portion for trimming or trimming, a cover coat is applied to this portion after trimming to ensure reliability. However, the application of the cover coat complicates the process.

Moreover, in the conventional trimming method, the obtained capacitance fluctuates due to the stray capacitance generated by applying a cover coat on the internal electrodes. Therefore, the trimming must be performed in consideration of the fluctuation. And accurate trimming was difficult.

In addition, since a part of the internal electrode forming the trimming capacitor is mechanically or physically removed together with the tissue in the vicinity thereof, a large stress is generated around the removed part, and the stress causes a problem. As a result, microcracks occurred, migration of the internal electrodes and the like were likely to occur, and the reliability was reduced. Moreover, it is difficult to detect the occurrence of microcracks non-destructively at an early stage, which has been a potential deterioration factor.

Further, in the conventional trimming method, a part of the internal electrode is mechanically or physically removed together with the tissue in the vicinity thereof, so that the trimmed portion can be formed only near the surface layer of the substrate, and the degree of freedom in circuit design is increased. Was low.

In order to solve these problems, the present applicant irradiates a trimming capacitor formed on or in the substrate with an electromagnetic wave such as a laser beam to heat the dielectric layer, and the heat is applied to the crystal. We have invented a method of changing its crystal structure between crystalline and amorphous, thereby trimming its acquisition capacity.

[0010] The present invention provides, when embodying the above invention,
An object of the present invention is to provide a trimming capacitor that can be easily trimmed without causing variation in the acquisition capacity of the trimming capacitor.

[0011]

A trimming capacitor according to the present invention includes a dielectric layer in which fine particles are dispersed, and internal electrodes facing each other via the dielectric layer. Here, the internal electrodes may face each other in a laminated state, or may face each other in a butt state. The latter internal electrode may be provided on the laser beam irradiation side, inside or on the opposite side of the dielectric layer.

The material of the fine particles is one that does not dissolve or decompose into the dielectric during the firing process, or that exists as fine particles before trimming, and is decomposed during the trimming process. Or a material that dissolves into the dielectric can be used.

As a material for such fine particles, for example, carbon, silver, copper, palladium, platinum, gold, nickel or an alloy thereof can be used, but those which do not adversely affect the characteristics of the dielectric layer are used. If so, other than these may be used. Instead of being added from the outside, phase-separated particles formed by deposition from the dielectric ceramic composition forming the dielectric layer may be used.

The average particle diameter of the fine particles is preferably at least ４ of the wavelength of the light irradiated for trimming. When the average particle diameter of the fine particles is set to this level. This is because the scattered and reflected light is large, and the dielectric layer can be effectively heated. However, the average particle diameter of the fine particles is preferably 10 μm or less. If it is larger than this, it becomes difficult to prepare a green sheet.

The content of the fine particles is 0.1% by volume to 40%.
% By volume is preferred. If the content is less than 0.1% by volume, a clear effect is not recognized. If the content is more than 40% by volume, the rate of change upon trimming becomes small, which is not practical. In addition, when metal powder is used as the fine particles, if the content of the fine particles is too large, there is a possibility that conduction between the electrodes may occur.

[0016]

【Example】

Example 1 (Ba, Sr, Ca) was a multilayer substrate having a large number of trimming capacitors with the O-Al ₂ O ₃ -SiO ₂ based glass. In the dielectric layer of the trimming capacitor formed on the multilayer substrate, 1% by volume of carbon fine particles were dispersed as fine particles for efficiently absorbing irradiated light as heat. The average particle size of the carbon fine particles is about 0.3 μm. The internal electrode was a silver (Ag) electrode. The internal structure near the capacitor of this multilayer substrate was as shown in FIG.

In FIG. 1, reference numeral 10 denotes a multilayer substrate, and a capacitor 12 is formed on one side (upper side in FIG. 1) of the multilayer substrate 10 therein. The capacitor 12 includes a pair of opposed internal electrodes 14, 14, and internal electrodes 14, 14.
And a dielectric layer 16 sandwiched between them. Reference numeral 18 denotes a laser beam emitted toward the condenser 12.

Next, with respect to the multilayer substrate provided with the capacitor, an area near the electrode intersection of the capacitor was irradiated with laser light to trim the obtained capacitance. The number of samples was 100. The laser used was an Nd-YAG laser (oscillation wavelength: 1.06 μm). Irradiation surface temperature is 900
C. and the irradiation time was 30 seconds.

When the variation in the obtained capacitance of the capacitor before and after the trimming was examined, it was as shown in Table 1. In Samples 1 to 5, the acquisition capacity was changed by changing the cross electrode area.
The electrode spacing was almost constant. The laser changed the focusing area in accordance with the cross-electrode area, and changed the laser output in proportion to the area so that the irradiation energy per unit area was almost constant.

COMPARATIVE EXAMPLE 1 Except that fine particles were not dispersed in the dielectric ceramic composition,
A trimming capacitor was prepared under the same conditions as in Example 1, and a laser beam was irradiated under the same conditions as in Example 1 to examine the variation in the obtained capacitance of the trimmed capacitor. The results were as shown in Table 1. .

[0021]

[Table 1]

As can be seen from the results in Table 1, the capacitor using the dielectric ceramic composition in which the fine particles are dispersed has a larger variation in the obtained capacity than the capacitor using the dielectric ceramic composition in which the fine particles are not dispersed. It can be seen that has decreased.

In the first embodiment, as can be understood from the structure shown in FIG. 1, the laser beam does not directly heat the dielectric layer to be trimmed, but once heats the internal electrode, and heats the heated internal electrode. It is considered that heat is transmitted to the dielectric layer, and the function of the carbon fine particles there is considered to be a function of efficiently absorbing the heat transmitted from the internal electrodes so as not to escape.

Example 2 The same substrate as that of Example 1 was prepared, and the condenser was heated by focused infrared rays instead of laser light. As a result, the heated area is slightly wider than in the case of laser light,
Although the physical properties seem to have changed up to the periphery of the target area, the obtained property changes were almost the same as in the case of the laser beam. Table 2 shows the results.

[0025]

[Table 2]

Example 3 A laser beam was applied to a trimming capacitor whose internal electrodes were brought into abutting condition as shown in FIG. 2, and a laser beam was directly applied to a dielectric layer to be trimmed. Laser irradiation conditions were the same as in Example 1. Table 3 shows the results
Shown in

[0027]

[Table 3]

Although the obtained capacitance value is lower than that of the first embodiment because of the butted structure of the internal electrodes, the other results are almost the same as those of the first embodiment. From this, it is understood that even if the fine particles are directly irradiated with the laser light, there is an effect of reducing the variation at the time of trimming.

Example 4 Metal silver fine particles were dispersed in place of the carbon fine particles dispersed in the dielectric in Example 3. The diameter of the silver fine particles was 0.3 μm, and 5 wt% was added to the dielectric material.
Table 4 shows the results. It can be seen that the same effect can be obtained by dispersing metal fine particles instead of carbon fine particles.

[0030]

[Table 4]

[0031]

According to the present invention, the fine particles dispersed in the dielectric layer efficiently receive the supplied energy, become hot, and rapidly heat the surrounding dielectric layer. Stable trimming can be performed irrespective of changes in the heat absorption conditions of the composition itself, and therefore, there is an effect that the variation in the acquired capacity of the capacitor after trimming is reduced.

Further, according to the present invention, the amount of absorption of light or the like can be controlled by changing the amount of dispersion of the fine particles, so that there is an effect that occurrence of defects due to insufficient heating or excessive heating can be prevented.

Further, according to the present invention, since the maximum wavelength of light to be absorbed can be changed by changing the size of the fine particles, it is possible to selectively trim using light of the same wavelength or the like. effective.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an internal structure near a capacitor of a multilayer substrate according to a first embodiment;

FIG. 2 is an explanatory diagram illustrating an internal structure near a capacitor of a multilayer substrate according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 10 multilayer substrate 12 capacitor 14 internal electrode 16 dielectric layer 18 laser beam

Claims (6)

[Claims] 1. A trimming capacitor comprising: a dielectric layer in which fine particles are dispersed; and internal electrodes facing each other via the dielectric layer. 2. The trimming capacitor according to claim 1, wherein the internal electrodes face each other in a stacked state or abutted state. 3. The trimming capacitor according to claim 1, wherein the fine particles are made of carbon, silver, copper, palladium, platinum, gold, nickel, or an alloy thereof. 4. The trimming capacitor according to claim 1, wherein the fine particles are phase-separated particles formed separately from a dielectric ceramic composition forming a dielectric layer. 5. The trimming capacitor according to claim 1, wherein an average particle diameter of the fine particles is at least １ ／ of a wavelength of light irradiated for trimming. 6. The content of the fine particles is 0.1% by volume to 4%.
The trimming capacitor according to claim 1, wherein the volume is 0% by volume.