JPH027171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chip-shaped solid electrolytic capacitor molded with resin, and provides an electrolytic capacitor that can be easily soldered when mounted on a circuit board and does not require flux during soldering. The purpose is to

Chip-shaped solid electrolytic capacitors are made by forming a dielectric oxide film on the surface of a valve metal such as tantalum or aluminum that has an anode lead wire, and then providing an electrolyte layer such as manganese dioxide on top of the dielectric oxide film. A so-called comb terminal formed by continuously punching out a thin metal plate in a comb shape is connected to both poles of a capacitor element in which layers, cathode layers, etc. As shown in FIG. 1, terminals 2 are pulled out from both ends of an exterior 1 made of resin mold, bent at almost right angles along the sides of the exterior, and further bent at right angles inward along the bottom surface.
When attaching this to a circuit board, the electrolytic capacitor is usually fixed to the circuit board with adhesive and then dipped into a bath of molten solder and pulled up, or the electrolytic capacitor is placed on the circuit board without using adhesive. A method is used in which a large number of capacitors are soldered at once by passing the solder through a heating furnace.
In this case, the most important issue is soldering performance, and chip electrolytic capacitors have metal terminals 4 on the entire circumferential surface of both ends of the main body 3, like the ceramic chip capacitor or resistor chip shown in FIG. Unlike others, as shown in Figure 1a, there are terminals 2 only on a portion of both ends of the main body, so when soldering many electrolytic capacitors at once, it is easy to have unsoldered parts. If even one board is poorly soldered, the entire board is defective and will need to be repaired, which will reduce productivity. The present invention enables a chip-shaped solid electrolytic capacitor having a terminal structure as shown in FIG. 1 to be easily and reliably soldered to a circuit board.

With the terminal structure shown in Figure 1, the soldering is not necessarily good or the finish is not neat, partly because there are no solderable metal thin plate terminals on the entire circumference of the end as shown in Figure 2. However, since the surface of the metal terminal becomes oxidized due to long-term storage, and the exterior of the main body is made of synthetic resin such as epoxy resin or silicone resin, it is difficult to fix this chip-shaped component to a circuit board, for example, with temporary adhesive. When the entire chip-like part is immersed in a solder bath and pulled out, molten solder may partially adhere to the surface of the exterior resin.
This is because solder scum (solder oxide) adheres to the main body surface in spots, and the solder scum also forms bridges between the metal terminal portion and the exterior or adjacent parts.

In order to solve these drawbacks, the present invention applies flux to the terminal portion of a chip-shaped solid electrolytic capacitor, or to the exterior surface of the terminal portion and its surroundings, or to the entire outer peripheral surface of the capacitor including the terminal portion. A thin film is formed in advance.

Oxidation of the terminal portion can be prevented by using a flux that does not contain a halogen compound, especially a flux that does not contain chlorine. If it contains chlorine, it is undesirable because it will corrode the metal terminals of the capacitor in a humid place. This flux film can be formed by immersing this chip-shaped capacitor in a solution of pine resin dissolved in isopropyl alcohol, pulling it out, and drying it. Furthermore, if the adhesion is insufficient with the pine resin film alone, a strong pine resin film can be formed by applying a thermoplastic resin such as urethane resin as a binder to the surface of the chip capacitor.

The thickness of the flux film is preferably 10μ to 500μ. The reason for this is that chip components are generally manufactured with good dimensional accuracy to facilitate automatic mounting, so if the flux layer is made too thick, the dimensional accuracy will vary and automatic mounting will not be possible. The value is a value that can prevent oxidation of the terminals without impairing the dimensional accuracy of this capacitor.

This flux film may be provided only on the surface of the terminal 2 shown in FIG. 1, or the flux film 5 may be formed on the entire circumferential surface of the chip capacitor including the terminal as shown in FIG. As shown in FIG. 4, a flux film 5 may be provided on the surface of the terminal 2 and the surface of the exterior 1 around it. In addition, the formation of a flux film is
Rather than forming the capacitor element after the resin sheathing and before bending the terminals, it is better to bend the terminals along both sides of the sheath, further bend them inside the bottom surface, and then form the flux film. The reason for this is that flux can enter the gap between the resin surface of the exterior and the surface of the metal terminal, allowing a large amount of flux to adhere to it, and also filling the grooves of the metal terminal with flux. be. It should be noted that FIG. 3 is effective when the chip component is not fixed to the circuit board with adhesive, and FIG. 4 is effective when the bottom surface is temporarily bonded to the circuit board.

The flux film thus formed prevents oxidation of the terminals during storage of the chip capacitor, and also melts and flows out due to the solder temperature or heating furnace temperature during soldering, improving solder flow. Improves solder wetting and improves soldering. Furthermore, since it can be used without flux during soldering, a chip capacitor that is extremely easy to use can be obtained.

In addition, when a flux film is also formed on the surface of the exterior of the capacitor, when the entire capacitor is immersed in a molten solder bath and soldered, it is possible to prevent solder and solder scum from adhering to the exterior surface, and This prevents solder from forming bridges between adjacent parts, allowing for clean soldering.

As described above, the chip-shaped solid electrolytic capacitor of the present invention has pine resin or pine resin and a thermoplastic synthetic resin as main components on the surface of the terminal plate pulled out from the side of the molded resin exterior, or on the terminal plate and the surface of the molded resin exterior. This flux film does not contain halogen compounds, especially chlorine, and is composed mainly of pine resin or pine resin and thermoplastic synthetic resin, so it can be stored as is for a long period of time. Corrosion of the terminal board can also be prevented. Furthermore, when a thermoplastic synthetic resin is used as a binder, a strong film can be obtained.

Further, the flux film melts and flows out due to the temperature of the solder or the temperature of the heating furnace during soldering when fixing the chip-shaped solid electrolytic capacitor to the circuit board, and improves the flow of the solder.
It is possible to improve solder wetting and improve soldering, and it can be used without flux during soldering, making it extremely easy to use.

Furthermore, since the thickness of the flux film is 10μ to 500μ, there is no variation in the dimensional accuracy of chip-shaped solid electrolytic capacitors, and automatic mounting on circuit boards is possible. When a film is provided on the terminal board and the exterior surface of the molded resin, it is possible to prevent solder and solder scum from adhering to the exterior surface when the entire capacitor is immersed in a molten solder bath and soldered. This prevents the formation of solder bridges between parts and allows for clean soldering.

[Brief explanation of drawings]

Fig. 1 is an external perspective view a and a side view b of a conventional chip electrolytic capacitor, Fig. 2 is a perspective view of an example of a conventional ceramic chip capacitor, and Fig. 3 is an external perspective view of an embodiment of the present invention. a and side sectional view b,
FIG. 4 is a perspective view a and a side sectional view b of another embodiment of the present invention. 1... Exterior, 2... Terminal board, 3... Ceramic capacitor body, 4... Metal terminal, 5... Flux film.

Claims (1)

[Claims] 1. In a chip-shaped solid electrolytic capacitor that is packaged with molded resin and has a terminal plate pulled out from the side of the package, bent downward along the side of the package, and further bent inward along the bottom surface, the surface of the terminal plate or the terminal On the exterior surfaces of the board and molded resin, a film of flux that is mainly composed of pine resin or pine resin and thermoplastic synthetic resin and does not contain halogen compounds is provided,
A solid electrolytic chip capacitor characterized in that the flux film has a thickness of 10μ to 500μ.