JPH0525372B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing chip-type and exterior-type multilayer ceramic capacitors. More specifically, the present invention relates to a method for manufacturing a highly reliable multilayer ceramic capacitor that does not allow penetration of plating solution during the process of metal plating external electrodes. BACKGROUND OF THE INVENTION In recent years, ceramic capacitors have come into widespread use as essential components for making electronic devices and circuits smaller, faster, and more reliable. FIG. 3 is a schematic perspective view of a multilayer ceramic capacitor before external electrodes are attached, and FIG. 4 is a schematic perspective view of the multilayer ceramic capacitor with external electrodes attached. In order to manufacture such a laminated ceramic capacitor 1, barium titanate ceramic powder is mixed with an organic solvent, a plasticizer, a binder, etc. to form a slurry, and then a long piece is formed using a doctor blade method or the like. A ceramic green sheet 2 is obtained. Next, this green sheet is cut into a predetermined size, and the internal electrodes 3 are formed on the cut sheet at a predetermined position by screen printing or the like. After that,
A plurality of these elements are laminated, green sheet films are laminated on top and bottom thereof as protective layers, and the elements are integrated under pressure to obtain a laminate. Next, this laminate is cut and separated into predetermined dimensions to obtain raw laminated ceramic capacitor chips. The raw chips are then fired at a temperature suitable for firing ceramic powder. Furthermore, as shown in FIG. 4, external connection electrodes 4 made of Ag or Ag-Pd are applied to the internal electrode lead-out portions at both ends of the obtained capacitor chip, thereby obtaining a multilayer ceramic capacitor. The multilayer ceramic capacitor manufactured in this way is arranged with the external electrodes facing each other on the conductor lands on the printed wiring board, and is soldered using either the solder dipping method, in which the external electrodes are immersed in molten solder, or the reflow soldering method, using cream solder. It is used and incorporated into electronic equipment. However, if the external electrode is attached to the board by direct soldering, the external electrode will be "soldered".
There is a problem in that the capacitor becomes thinner and the mounting strength of the capacitor becomes weaker. In order to prevent solder cracking of the external electrodes of multilayer ceramic capacitors, Ni or Cu plating is further applied to the external electrodes, which were conventionally formed using conductive Ag paste or Ag-Pd paste, as a barrier to prevent solder cracking. ,
Furthermore, solder plating (or Sn, Pb plating) is applied on top of this.
There are multilayer chip capacitors that improve solder flow. Problems to be Solved by the Invention However, when plating Ni, Cu, etc., in an acidic electrolytic plating solution with a pH of about 4.5,
In addition, to perform solder plating, it is necessary to immerse the multilayer chip capacitor in an acidic electrolytic plating solution with a pH of 1 to 4 or lower, which may cause the plating solution to seep into the multilayer capacitor, resulting in a decrease in capacitance, an increase in current loss, etc. This results in performance deterioration. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily obtaining a highly reliable capacitor by preventing quality deterioration in the conventional plating process of multilayer ceramic capacitors. Means for Solving the Problems The present invention is a method for manufacturing a multilayer ceramic capacitor, which includes a step of attaching an external electrode to a plate-shaped capacitor assembly in which a ceramic sheet and an internal electrode are laminated, and a step of attaching an external electrode to the external electrode. The present invention provides a method for manufacturing a multilayer ceramic capacitor, characterized in that a step of treating with a coupling agent is provided between the step of metal plating. In the present invention, the multilayer ceramic capacitor coated with external electrodes and fired may be manufactured by a conventional method. For example, ceramic green sheets and internal electrodes (Ag-Pd, Pb,
Ag or Ag for the external electrode
Dip or apply in alloy paste, 600~850℃
Baking is performed. Next, the multilayer ceramic capacitor thus obtained is treated with a coupling agent. As the coupling agent, any of various silane coupling agents can be used, such as ClC ₃ H ₆ Si(OCH ₃ ) ₃ , CH ₂ =CHSiCl ₃ , CH ₂ =CHSi(OC ₂ H ₅ ) ₃ , _CH2 =CHSi( _OCH3 ) ₃ , _CH2 =CHSi( _{OC2H4OCH3 ) 3 , CH2 = CCH3COOC3H6Si} ( _{OCH3 ) 3} , HSC ₃ H ₆ Si (OCH ₃ ) ₃ , NH ₂ C ₃ H ₆ Si (OC ₂ H ₅ ) ₃ , NH ₂ C ₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ , NH ₂ CONHC ₃ H ₆ Si A silane coupling agent represented by a structural formula such as (OC ₂ H ₅ ) ₃ can be used. The coupling treatment is performed by immersing a fired laminated ceramic capacitor with external electrodes in a coupling agent (or its solution) under reduced pressure in a desiccator. The ceramic capacitor is then taken out and dried. It is preferable to carry out such dipping and drying two to three times. Capacitors treated with coupling agents in this way are then treated with Ni or
Electrolytic metal plating (approx. PH4.5) using Cu, etc., and electrolytic solder (or Sn, Pb) plating (<PH1~
4.5) is carried out, and a chip type capacitor is used, or
Alternatively, a lead wire can be attached to the capacitor to form an exterior capacitor. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples. (i) Chip-type multilayer ceramic capacitor Ceramic sheet: Barium titanate Internal electrode Ag-Pd External electrode Ag paste Capacitor dimensions 3.2 x 1.6 mm (ii) Silane coupling agent: (γ-glycidoxypropyl trimethoxysilane) The above 22 multilayer capacitors were immersed in a coupling agent and placed in a desiccator under reduced pressure for 30 minutes.
The penetration of the coupling agent into the porous portion was facilitated. After immersion, the capacitor was pulled up and dried at approximately 150°C. Seventeen of these capacitors were again immersed in the coupling agent and dried. Thirteen of them underwent a third immersion and drying process. The external electrodes of these chip capacitors were plated with Ni and then soldered under the following conditions. (Ni plating) Electrolyte: NiSO ₄ 220g/, NiCl ₂ 45g/, H ₃ BO ₃ 40g/, PH4~4.5 Electrode: Ni plate, voltage 1V, current 3A (Solder plating) Plating liquid: Solderon SG (Japan Metal) Co., Ltd.)
PH4 Electrode: Pb-Sn plate, voltage: 1.5V, current: 0.6A The electrical loss (tan δ) of the obtained chip capacitor after plating is compared with the value after the firing process and is shown in Table 1 and Figure 1. . Comparative Example Chip capacitors were obtained by metal plating five chips in the same manner as in the example except that the coupling treatment was not performed. Its physical properties are shown in Table 1 and FIG. 1 in the same manner as above.

[Table] As is clear from Table 1 and Figure 1, some of the samples that were not treated with a coupling agent showed a marked increase in tan δ value after the plating treatment, resulting in large electrical losses. On the other hand, for those treated with a coupling agent, the tan δ value did not increase even after plating as the number of treatments increased from once to three times, and with three treatments, there was almost no increase in the tanδ value between after firing and after plating. No difference observed. Furthermore, FIG. 2 shows the results of a deflection test of a capacitor treated with a coupling agent.
As the number of treatments increased, the amount of deflection increased, and almost all test products satisfied the 2 mm deflection test (Japan Electronics Industry Association standard RC-3402) after 2 to 3 treatments. Effects of the Invention As described above, according to the manufacturing method of the present invention, a highly reliable multilayer capacitor without an increase in capacitor current loss can be obtained by treatment with a coupling agent. Furthermore, according to the method of the present invention, a multilayer capacitor having high deflection characteristics can be obtained.

[Brief explanation of the drawing]

Figure 1 shows tanδ before and after metal plating in each treatment.
Figure 2 is a graph showing the relationship between the number of coupling treatments and the amount of deflection; Figure 3 is a schematic perspective view showing the chip capacitor before external electrodes are attached;
FIG. 4 is a schematic perspective view showing a chip capacitor with external electrodes attached. The symbols in the figure are as follows. 1... Ceramic capacitor, 2... Ceramic green sheet, 3... Internal electrode, 4... External electrode.

Claims (1)

[Claims] 1. A method for manufacturing a multilayer ceramic capacitor, in which a coupling agent is used between the step of attaching an external electrode to a plate-shaped capacitor assembly in which ceramic sheets and internal electrodes are laminated, and the step of plating the external electrode with metal. 1. A method for manufacturing a multilayer ceramic capacitor, comprising a step of processing.