JPH0252498A - Multilayer board with built-in capacitor - Google Patents

Abstract

PURPOSE:To improve accuracy of static capacity of a built-in capacitor by providing a hole or a recess for laser trimming formed on the surface of a multilayer ceramic substrate for enabling trimming by laser beam to be made later. CONSTITUTION:Ceramic substrates 12 to 20 are laminated on a multilayer board 10. Then, a capacitor electrode 22 is formed on the lower surface of the substrates 12, 16, and 20, while a capacitor electrode 24 is formed on the lower surface of the substrates 14 and 18. Electrodes 22 and 24 are connected to through-hole conductors 26 and 28 penetrating the one-piece boards 12 to 20 and the conductors 26 and 28 are connected to pattern conductors 30 and 32 formed on the surface of the substrate 12. A hole 34 for laser trimming is formed directly above the electrode 22 and the electrode 22 is exposed. Thus, a laser beam is irradiated through a hole 34 to allow one part of the electrode 22 to be eliminated and the opposing area with the electrode 24 to be reduced. In this manner, after calcination, by irradiating the laser beam through the hole 34, the value of static electricity built into the board 10 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer board with a built-in capacitor, and more particularly to a multilayer board with a built-in capacitor, which has a built-in capacitor using laminated substrates as dielectrics.

[Prior Art] A multilayer board with a built-in capacitor is well known, in which internal electrocutions are printed on a ceramic green sheet, laminated and pressure-bonded, and integrally fired.

[Problem to be solved by the invention]

Conventional multilayer boards with built-in capacitors cannot be trimmed, so the variation in capacitance (direction) of the built-in capacitors was as large as ±20%. Therefore, high-precision capacitors that require an accuracy of ±3% are not trimmed. Instead, a capacitor chip was added as an external component.The need to add an external capacitor in this way means that
This was hindering high density.

Therefore, the main object of the present invention is to provide a multilayer board with a built-in capacitor that can contain a higher precision capacitor.

[Means for Solving the Problems] Simply put, the present invention provides a multilayer ceramic substrate, a multilayer capacitor region formed in a part of the multilayer ceramic substrate, and a laser trimming region formed on the surface of the multilayer ceramic substrate. It is a multilayer board with a built-in capacitor that has holes or recesses.

[Operation] When laser light is irradiated through the hole or recess for laser trimming, all or part of the internal electrode forming the capacitor in the capacitor region is removed, thereby changing the capacitance.

〔Effect of the invention〕

According to this invention, since it is provided with a hole or recess for laser trimming, it can be trimmed later with a laser beam, thus improving the accuracy of the capacitance value of the built-in capacitor and adding external parts. There is no need to do so. Therefore, according to the present invention, it becomes possible to increase the density.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Embodiment) FIG. 1 is a perspective view showing a main part of an embodiment of the present invention. The multilayer ceramic substrate 10 of this embodiment is formed by laminating five layers of ceramic substrates 12 to 20. As shown in FIG. 2, a capacitor electrode 22 is provided on the lower surfaces of the ceramic substrates 12, 16 and 20, and a capacitor electrode 24 is provided on the lower surfaces of the ceramic substrates 14 and 18.
Each is formed. These capacitor electrodes 22 and 24 form a capacitor region similar to known multilayer ceramic capacitors.

That is, the capacitor electrode 22 is connected to a through-hole conductor 26 that penetrates the integrated ceramic substrates 12 to 20, and the capacitor electrode 24 is connected to a through-hole conductor 28.
are connected to each. And through-hole conductor 26
are connected to a pattern conductor 30 formed on the surface of the ceramic substrate 12, and the through-hole conductor 28 is connected to a pattern conductor 32. Therefore, between the patterned conductors 30 and 32, the respective capacitor electrodes 22 and 24
A plurality of capacitances formed between the two capacitors are connected in parallel. The capacitance is the capacitance of the capacitor electrodes 22 and 24.
It is determined by the opposing area of the capacitor electrodes 22 and 24, the distance between the capacitor electrodes 22 and 24, and the dielectric constant of the ceramic substrate itself sandwiched between the capacitor electrodes 22 and 24.

On the ceramic substrate 12 disposed on the top of the multilayer ceramic substrate 10, a laser trimming ring 34 is formed directly above the capacitor electrode 22. Therefore, in this hole 34, the capacitor electrode 22 is exposed. Therefore, when a laser beam is irradiated through the hole 34, a part of the capacitor electrode 22 is removed, and the area facing the capacitor electrode 24 is reduced. In this manner, the capacitance value built into the multilayer ceramic substrate 10 can be adjusted by irradiating laser light, such as a YAG laser or a CO2 laser, through the hole 34 after firing. In order to facilitate laser beam irradiation, the size of the hole 34 is set to, for example, about 1 diameter or 1 ffi11 square.

Note that after the laser trimming is completed in this manner, the hole 34 is filled with, for example, glass in order to prevent deterioration of moisture resistance.

When trimming the electrode 22, a laser beam is irradiated through the hole 34, but at this time, the ceramic substrates 12 and 14 may be reduced by the laser beam and their insulation resistance may deteriorate. Therefore, in this embodiment, a non-reduced ceramic is used for the ceramic substrate at least in the portion that is affected by the laser beam. Such a non-reducing ceramic.

For example, if it is a crystallized glass-based material, cordierite-based Zn0-MgO・Al2O,・
If 5in2 is made of glass composite, S t O2
・If B20x glass + 802o3 is a non-glass type, it is APzo3 ・CaO・S ioz MgO・
B203 or BaO-3iOz ・Affz O
:l -CaO-r3zo o:l type and the like can be used.

In this way, if non-reduced ceramic is used, Cu can be used as the capacitor electrodes 22 and 24. Ag, Ag/Pd, etc. are also used as capacitor electrodes 22 and 24.
However, if Cu is available, it is inexpensive.

In the above embodiment, the hole 34 formed in the ceramic substrate 12 reached the capacitor electrode 22;
As shown in FIG. 3, the hole 34' may be deep enough so that the capacitor electrode 22 is not exposed. Even if a thin layer of the material of the ceramic substrate 12 remains on the capacitor electrode 22, the remaining ceramic substrate 12 can be removed by irradiating the laser beam, so there is no particular problem in trimming. According to this embodiment, since the capacitor electrode 22 in the uppermost layer is not exposed at first, if trimming is not required, it may be left as is without being filled with glass as described above.

Note that the multilayer ceramic substrate described above has holes 34 (or 3
4') After preparing the ceramic substrate 12 provided with - and the other ceramic substrates 14 to 20 in the form of ceramic green sheets, and printing necessary capacitor electrodes and other conductors on each ceramic green sheet, It can be made by laminating layers and firing them together.

However, after the ceramic substrate 12 and the block consisting of the other ceramic substrates 14 to 20 are individually fired, they may be joined together using solder, glass, or the like.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the present invention. FIG. 2 is an illustrative cross-sectional view of the embodiment shown in FIG. FIG. 3 is an illustrative cross-sectional view showing another embodiment. In the figure, 12 to 20 are ceramic substrates, 22 and 24 are capacitor electrodes, 26 and 28 are through-hole conductors, and 34 and 34' are holes. Patent applicant Murata Manufacturing Co., Ltd. Representative Patent attorney Yama 1) Yoshito

Claims (1)

[Claims] 1. A multilayer ceramic substrate, a multilayer substrate with a built-in capacitor, comprising a capacitor region formed in a part of the multilayer ceramic substrate, and a hole or recess for laser trimming formed on the surface of the multilayer ceramic substrate. .