JPH04340212A - Chip type aluminum electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance the solder thermal resistance by a method wherein the inner porosity of a metallic case containing a capacitor element is maintained in the value exceeding specific level. CONSTITUTION:The title chip type aluminum electrolytic capacitor previously manufactured is fed to a reflow furnace so that the thermal effects on the capacitor may be compared in consideration of the changes in the visual shapes (expansion size of sealing rubber). Furthermore, when another capacitor in proper capacity made of a high capacity electrode foil is likewise fed to the reflow furnace, the expansion size of sealing part of the title chip type aluminum electrolytic capacitor in the same porosity of 25% amounted to the little value of only 0.04mm. Through these procedures, the thermal resistance can be enhanced by keeping the porosity exceeding 25% so that the requirement range for the reflow soldering step may be enlarged thereby enabling the title chip type aluminum electrolytic capacitor in high reliability to be manufactured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is based on a reflow method.
This invention relates to a chip-type aluminum electrolytic capacitor that is soldered and mounted on a board.

0002

[Prior Art] Conventional electrolytic capacitors are manufactured by connecting lead terminals to etched and chemically treated anode foil and cathode foil, winding them through electrolytic paper, storing them in a cylindrical case, and tightening the case to seal it. The electrostatic capacitance is determined by the specified withstand voltage and the composite capacitance of the foil. Therefore, the element diameter of the electrolytic capacitor varies depending on the size and rating.

0003

[Problems to be Solved by the Invention] In recent years, with the increasing density of electronic equipment, various soldering methods have been developed with the aim of improving the reliability of soldering. Typical examples include hot air method, V.
P. There are methods such as S method. However, in order to improve soldering reliability, it is necessary to improve thermal conductivity. However, the boiling point of the electrolytic solution used in chip-type aluminum electrolytic capacitors is generally 150°C to 170°C. However, the soldering temperatures applied during reflow far exceed this. Therefore, excessive heat during reflow causes an increase in internal pressure, which causes expansion of the sealing part of the chip-type aluminum electrolytic capacitor and expansion of the bottom of the case, leading to destruction in the worst case. Therefore, the usage conditions for chip-type aluminum electrolytic capacitors are limited, and some products are difficult to use.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides an electrolytic electrolyzer in which a lead lead drawn out from a capacitor element is passed through a lead hole provided in a sealing body and housed in a cylindrical metal case. In capacitors, the void ratio inside the metal case is 2 regardless of the case size or rating.
This is a chip-type aluminum electrolytic capacitor characterized by a capacitance of 5% or more.

[0005]

[Function] The simplest and most appropriate measure to increase the heat resistance of chip-type aluminum electrolytic capacitors is to suppress the vapor pressure of the electrolyte used and further increase its boiling point. However, raising the boiling point of the electrolyte will have a significant impact on the current characteristics and will require a significant amount of time to develop. Therefore, the present invention reduces the internal pressure of the electrolytic capacitor under high temperatures during reflow, which is a problem in current reflow soldering, by reducing the internal gas pressure by increasing the void ratio in the metal case to 25% or more. A chip-type aluminum electrolytic capacitor with improved heat resistance and suitable for reflow soldering was obtained.

[0006]

EXAMPLES The present invention will be explained in detail below based on examples. Using electrode foils with the same formation voltage and changing the length of the housing foil, 5
Manufacturing capacitor elements with different element diameters, storing them in a metal case, and tightening the case opening, JP-A-59-21
A chip-type aluminum electrolytic capacitor as disclosed in Japanese Patent No. 1214 was obtained, and the capacitor was passed through a reflow oven, and the degree of influence of heat on the capacitor was compared in terms of changes in external shape (particularly the expansion size of the sealing rubber). The test conditions used were the temperature profile of the current heat resistance limit where the sealing part of the chip-type aluminum electrolytic capacitor expands. FIG. 1 shows the results of determining the void ratio and the expansion coefficient of the sealing portion of the chip-type aluminum electrolytic capacitor in this manner. The smallest chip type aluminum electrolytic capacitor with a void ratio of 10% has a rubber seal of 0.6 m.
The expansion size is about 0 to 0.05 mm in the case of the present invention which secures a void ratio of 25%.
It's clearly an improvement. Furthermore, a capacitor with the desired appropriate capacity was manufactured by using high-capacity foil as the electrode foil, and passed through a reflow oven in the same manner as above. The expansion of the sealing part of the electrolytic capacitor was small and its size was 0.04 mm, which was the same as the above result. In addition to the above-mentioned embodiments,
Needless to say, the present invention can be similarly applied to a horizontal chip type electrolytic capacitor as disclosed in Japanese Patent Application Laid-Open No. 1-218004.

[Effects of the Invention] As described above, the chip-type aluminum electrolytic capacitor of the present invention can improve heat resistance by maintaining a void ratio of 25% or more, allowing for a wider range of reflow soldering conditions and providing reliability. It is possible to obtain a chip-type aluminum electrolytic capacitor with high performance, which is of great industrial value.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the porosity-sealing expansion dimension characteristic of the chip-type electrolytic capacitor of the present invention.

Claims (1)

[Claims] An electrolytic capacitor in which an extraction lead led out from a capacitor element passes through a lead hole provided in a sealing body and is housed in a cylindrical metal case, wherein the chip has a void ratio inside the metal case of 25% or more. Aluminum electrolytic capacitor.