JPS6373514A - Laminated ceramic capacitor and manufacture of the same - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a small multilayer ceramic capacitor with a large capacitance and a method for manufacturing the same.

[Conventional technology]

Conventionally, multilayer ceramic capacitors (hereinafter abbreviated as capacitors) are manufactured by first kneading finely ground ceramic powder and an organic binder, and then producing an unfired ceramic green sheet (hereinafter abbreviated as green sheet) using a doctor blade method. This raw sheet is cut into a desired shape, and internal electrodes are formed on the surface thereof by means such as screen printing.

Next, multiple raw sheets with internal electrodes printed on one side are stacked so that the upper and lower sides are sandwiched between protective layers consisting of multiple raw sheets without internal electrodes printed on them, and then thermocompression bonded to form a laminate. Cut the body into individual chips. A capacitor is produced by firing each piece of raw Tegg and burning terminal electrodes at both ends.

FIG. 5 is a schematic cross-section 1 of a conventional capacitor manufactured as described above, in which one internal electrode 1 and the other internal electrode t&1 opposing thereto are laminated with a ceramic layer 3 interposed therebetween.

The capacitance of the capacitor described above is proportional to the number of overlapping areas of one internal electrode 1 and the other internal electrode 1 and the number of overlapping layers of the internal electrode 10.

One way to respond to the recent demands for smaller capacitors and larger capacitance is to reduce the thickness of the dielectric and thereby increase the number of overlapping layers of internal electrodes within the same volume. There is. According to this method, for example, by reducing the thickness of the dielectric to 1/2, it is possible to obtain approximately 40 times the capacity with the same volume.

[Problem that the invention seeks to solve]

In the conventional capacitor described above, in contrast to the overlapping part of the opposing internal electrodes at the center of the capacitor, the opposing internal electrodes do not overlap at both ends of the capacitor and are thinned by the thickness of one internal electrode. There is. In particular, in capacitors that have thinner ceramic layers to make them smaller and larger in capacity, there are a large number of raw sheets on which internal electrodes are adhered, so the central part is divided into two areas: one where the opposing internal electrodes overlap, and the other where only one internal electrode overlaps. There will be a large difference in thickness between both ends. Therefore, both ends of the capacitor are thinner, the center part is thicker and the upper part is bent, and the entire capacitor is bent into an arched shape, which causes stress inside the capacitor and heat and solder when mounting the capacitor on a printed circuit board. The disadvantage was that reliability deteriorated due to mechanical stress caused by

SUMMARY OF THE INVENTION The object of the present invention is to provide a capacitor and a method for manufacturing the same which eliminates the above-mentioned drawbacks.

In contrast to the conventional capacitors described above, the present invention has the original content of preventing the occurrence of internal stress in the capacitor by adjusting the thickness balance of the internal electrodes, thereby improving reliability particularly against thermal stress.

[Means for solving problems]

The present invention provides a multilayer ceramic capacitor in which a part of one internal electrode and a part of the other internal electrode overlap each other with a ceramic layer interposed therebetween, in which the thicknesses of the one internal electrode and the other internal electrode in the parts that do not overlap with each other are It is assumed that the thickness is twice the thickness of the one and the other internal electrodes in the mutually overlapping portion.

The method for manufacturing the multilayer two-layer capacitor of the present invention is as follows:
A first step of forming a first internal electrode by screen printing on one side of the raw mix sheet, and after this 'sl' process, a 20th internal electrode is screen printed on a part of the first internal electrode. a 20th step in which the 20th internal electrode is not adhered to, and a portion of the first internal electrode formed in contact with the groove in the 20th step overlaps with the 20th internal electrode. and a third step of laminating a plurality of the raw ceramic sheets.

〔Example〕

Embodiment 1 of the present invention will be described in detail below with reference to FIGS. 1 and 4.

FIG. 1 is a schematic sectional view of a capacitor according to an embodiment of the present invention.

One internal electrode structure and the other internal electrode 1 facing it are laminated with a ceramic layer 3 in between.

At both ends of the capacitor where the opposing internal electrodes 1 do not overlap, the internal electrodes 2 are formed on the internal electrodes 1 . Since the thickness of internal electrode 2 is the same as that of internal electrode 1, the total thickness of internal electrodes 1 and 2 is twice the thickness of internal electrode 1, and the internal thickness at the center and both ends of the capacitor is Electrode 1
．． Since the sum of the thicknesses of the two capacitors is equal, the thickness of the entire capacitor is also uniform at the center and both ends.

FIG. 2 is a plan view of the screen 4 used for printing the internal electrode 1t of the embodiment shown in FIG. 1, sb, and the internal electrode 1 of the conventional capacitor shown in FIG. The through hole 114.llb provided in the screen 4 corresponds to the internal electrode 1, and the elongated through hole 11a is divided into two equal parts when cutting the laminate into individual green chips. The rectangular through holes 11b are for printing the internal electrodes 1 that are separated into two pieces of raw chips. They are provided in the end rows of the matrix of through holes arranged in the screen 4.

FIG. 3 is a plan view of the screen 5 used for printing the internal electrodes 2 of the embodiment of the present invention shown in FIG. The through holes 12a provided in the screen 4 are for printing internal electrodes 2 that are divided into two equal parts and separated into two raw chip pieces when the laminate is cut into raw chip pieces. . The through holes 12b are for printing the internal electrodes 2 in one raw chip, and are provided in the end rows of the matrix of through holes arranged in the reed screen 4.

Fig. 4 (→~(Φ is the through hole 11JL and 12L, respectively.

The through holes 11JL, 12& are lines corresponding to the actual cutting lines.

The sizes and positional relationships of 11b and 12b are indicated by dimensions La, ja, Lb, and jb.

The lengths of the through hole 11 & in the vertical and horizontal directions (vertical and horizontal here refer to the vertical and horizontal in FIGS. 2 to 4; the same applies hereinafter) are 2xLa and Lb, respectively, and the transparent hole in the vertical and horizontal directions is Hole 11J1. Let the distance between llb be 2×ノ& and 2×jb, respectively. The lengths of the through hole 11b in the vertical and horizontal directions are each La ten jars! a and Lb.

The length of the through hole 12Jl in the vertical and horizontal directions is 2, respectively.
Xjm and Lb, and the lengths of the through hole 12b in the vertical and horizontal directions are l &1'zl& and Lb, respectively.

The through hole 12jL is arranged so that the horizontal axis of symmetry of the through hole 12a coincides with the horizontal axis of symmetry for the through hole 11.

The through hole 12b is located at the upper side of the through hole 11b.
2b so that the upper sides thereof coincide with each other. Also, the horizontal distance between the through holes 121 and 12b is 2×! b.

Explain in detail.

First, after kneading finely ground ceramic powder and organic pineapple, the doctor blade method was used to form a powder with a thickness of 15 cm.
A raw sheet of μ is prepared, and then this raw sheet is cut into a desired shape. Next, using a stainless steel screen 4 shown in FIG. 2, a screen stamp is applied to the surface to form the internal electrode lt-adhesion, and after drying, the internal electrode 2 is formed using a screen 5 shown in FIG. 3. It is deposited on the previously formed internal electrode 1 and dried.

Printing using the screen 5 is performed so that the corresponding positions of the centers of the through holes 11a and the centers of the through holes 128 coincide, and the corresponding positions of the upper sides of the through holes 11b and the upper sides of the through holes 12b coincide with each other.

Internal electrodes 1, 2t - multiple raw sheets printed on one side (
For example, 40 sheets) are stacked (internal electrodes printed on a screen 4°5, with the second pattern facing the first direction and the second pattern facing the 20th direction rotated 180° from the first direction). ), this stacked internal electrode 1
A laminate is formed by sandwiching a plurality of green sheets printed with . The raw chip pieces formed by cutting this laminate are fired, and terminal electrodes are baked on both ends to obtain the multilayer ceramic capacitor of the present invention.

As described above, the present invention provided with the internal electrode 1.2 has a thickness of 1n.
This process was performed on an n(t) 95X alumina substrate using 3% silver solder at 270°C and 300°C for 3 seconds each, and at a temperature of 125° and an applied voltage of 25V as shown in the following photo.
An accelerated test of 1000 hours and a temperature of 65°C, an applied voltage of 25 cm, and a humidity of K 90 x 500 hours was conducted. The results are also shown in the table below.

Margins below, ramie 2 1 + □r [Effects of the Invention] As explained above, the present invention provides reliability against thermal stress even if the thickness of the ceramic is reduced, the size is made smaller, and the capacitance is increased. It has the effect that high multilayer ceramic capacitors can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a plan view of a screen for printing the internal electrodes shown in FIG. Figure 4 (older sister) (→ is a partial enlarged view of the through holes 11a and flb shown in Figure 2, respectively, Figure 4 (b) l (ψ is the through hole shown in Figure 3, respectively) 12a and 12b are partially enlarged views, and FIG. 5 is a sectional view of a conventional capacitor. 1.2... Internal electrode, 3... Ceramic layer, 4° 5...・・Screen, 11 &, llb
, 12a. 12b...Through hole. Figure 3 (gradient (b) (C) (random) Figure 4 Figure 5

Claims (2)

[Claims] (1) In a multilayer ceramic capacitor in which a part of one internal electrode and a part of the other internal electrode overlap each other via a ceramic layer, the thicknesses of the one internal electrode and the other internal electrode in the parts that do not overlap with each other are A multilayer ceramic capacitor characterized in that the thickness is twice as thick as that of the one and the other internal electrodes in the overlapping portion. (2) A first step of forming a first internal electrode on one side of the green ceramic sheet by screen printing, and after this first step, a second internal electrode is formed on a part of the first internal electrode. a second step of adhering and forming by screen printing, and after this second step, the first
a third step of laminating a plurality of the raw ceramic sheets so that the portions of the internal electrodes on which the 20th internal electrode is not adhered overlap.