JPS6122452B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for packaging electronic components, and in particular, an object of the present invention is to reduce the creeping up and adhesion of a resin material to an external lead member in a solid electrolytic capacitor.

Generally, this type of solid electrolytic capacitor is
As shown in the figure, a metal wire having a valve action is attached in advance to a capacitor element A made by press-forming metal powder having a valve action such as tantalum, niobium, aluminum, etc. into a cylindrical shape and sintering the anode lead B. The first external lead member C is welded to the conductive portion of this anode lead B, and the second external lead member D is soldered to the electrode lead layer E formed on the circumferential surface of the capacitor element A. After that, the main parts including the capacitor element A are covered with a resin material F.

By the way, the resin material F of the capacitor element A
The coating is carried out, for example, by a dipping method as shown in FIG. That is, as shown in FIG. 1A, first, the capacitor element A is immersed in a thixotropic resin material F' to a level such that it is completely immersed. Normally, this resin material F′ has a high viscosity, for example, 20,000 CPS or more, so immediately after immersion, the resin material
The wettability of F' to the capacitor element A is poor, and the resin material F' is not coated on the top surface of the capacitor element A.

Therefore, the immersion level of the capacitor element A is subsequently made deeper, as shown in FIG. Then, the entire circumferential surface of the capacitor element A is completely covered with the resin material F'. and,
The packaging is completed by pulling up the capacitor element A and subjecting it to heat treatment.

However, when pulling up capacitor element A from resin material F',
Because the immersion level in the resin material F' is deeper than necessary and the resin material F' existing between the first and second external lead members C and D hangs down.
The resin material F' is thinly applied to the second external lead members C and D, so that the resin material F' creeps up on the second external lead members C and D, and the appearance characteristics are significantly impaired. In addition, as shown in FIG. 3, when mounted on the printed board H, the creeping resin material G protrudes to the back surface of the printed board H, so that the first and second external lead members C , D and the printed conductor are also damaged.

On the other hand, as shown in Figure 2a, if the immersion time of the capacitor element A into the resin material F' is made long enough, the liquid level of the resin material F' will gradually rise until it reaches the position indicated by the dotted line in the figure. Return until. Therefore, if the capacitor element A is pulled up at this point, the first and second external lead members C and D
The creeping up of the resin material F' against the printed board H can be suppressed to a level that does not pose a practical problem.
However, it has the disadvantage of significantly reducing workability, and has not yet been put into practical use.

Therefore, various solutions have been proposed in the past. For example, in Japanese Patent Application Laid-Open No. 55-145328, prior to immersing a component body with a plurality of external lead members extending in the same direction in a resin material, a chain-like material such as wax, stearic acid, paraffin, etc. By immersing the component body in a chlorinated hydrocarbon solution in which hydrocarbons or higher fatty acids are dissolved, so that the external lead member is immersed,
By forming a film of chain hydrocarbon or higher fat on the component body and the external lead member, and then immersing the component body in a solvent such as trichlorethylene or trichloroethane so that the desired portion of the external lead member is not immersed. , discloses a method for packaging electronic components in which undesired portions of the coating are removed.

According to this method, even if the immersion level of the component body into the resin material is as deep as shown in FIG. Because of the coating, the resin material is repelled and unwanted creep-up and adhesion can be effectively suppressed.

By the way, when this method is applied to, for example, the solid electrolytic capacitor described above, it is possible to effectively suppress the creeping up and adhesion of the resin material F to the first and second external lead members C and D. A problem arises in that a large number of pinholes are formed on the surface of the material F, and the appearance characteristics are significantly impaired.

To elaborate on this point, since capacitor element A has a porous structure, when it is immersed in a chlorinated hydrocarbon solution in which chain hydrocarbons or higher fatty acids are dissolved, the solution is absorbed into the deep layer of capacitor element A. Even the pores in the area are impregnated. However, although the solution impregnated in the surface layer of the capacitor element A can be easily removed by simply immersing the capacitor element A in a solvent for a short time, the solution impregnated in the deep layer cannot be easily removed in a short time. Therefore, even if the material is impregnated with an impregnating agent for the purpose of preventing the formation of pinholes, the deep layer cannot be sufficiently impregnated due to the water repellent effect of the remaining coating. For this reason, the air contained in the pores in the deep layer expands thermally when the resin material F is heated and hardened, penetrates the resin material F, and is released to the outside, resulting in the formation of many pinholes. It is considered that

On the other hand, if the capacitor element A is immersed in a solvent for a long time, although the solution in the deep layer can be removed eventually, the working efficiency will be significantly reduced, making it extremely difficult to apply to a mass production process.

In view of these points, the present invention provides a method for packaging electronic components that can effectively improve not only the creeping up of the resin material onto the external lead member but also the occurrence of pinholes in the resin material. An example of application to a solid electrolytic capacitor will be described below with reference to FIGS. 4 to 8.

First, as shown in FIG. 4, a fine metal wire with a valve action is implanted in advance as an anode lead 2 into a capacitor element (component body) 1, which is made by press-molding metal powder with a valve action into a cylindrical shape and sintering it. The first external lead member 3 formed in an L shape is welded to the lead-out portion 2a of the anode lead 2 so that the bent portions 3a intersect. Then, one end 4a of the second external lead member 4 formed in a straight shape is soldered to the electrode lead layer 5 formed on the circumferential surface of the capacitor element 1 via an oxide layer, a semiconductor layer, and a graphite layer. . Note that the first and second external lead members 3 and 4 are led out in the same direction. Next, the capacitor element 1 is immersed in a water-repellent member to a deeper level than the immersion level of the first and second external lead members 3 and 4 in a resin material having thixotropic properties, which will be described later, and then pulled up. As a result, a water-repellent coating 6 is formed on the capacitor element 1 and the first and second external lead members 3 and 4, as shown in FIG. Next, the capacitor element 1 is coated with a low-viscosity impregnating agent that is compatible with the water-repellent member (water-repellent coating 6). Immerse so that the coating 6 is not immersed. Then, the impregnating agent is applied to capacitor element 1.
Even though the water-repellent coating 6 formed in the same portion has a water-repellent effect, the pores are reliably impregnated due to their mutual solubility. Then, after pulling, an impregnated layer 7 is formed on the surface of the capacitor element 1 or the water-repellent coating 6 by heat treatment, as shown in FIG. Next, the seventh
As shown in the figure, this capacitor element 1 is coated with a resin material 8' having thixotropic properties so that the upper ends of the water-repellent coatings 6 on the first and second external lead members 3 and 4 protrude slightly from the liquid level. deeply immerse in. As a result, the entire circumferential surface of the capacitor element 1 is wetted with the resin material 8' in a short time, but the resin material 8' is repelled near the liquid level of the first and second external lead members 3 and 4. Become. Next, when the capacitor element 1 is pulled up from the resin material 8', the resin material 8' existing between the first and second external lead members 3 and 4 hangs down, and at the same time, the first and second external lead members The resin material 8' that is in contact with 3 and 4 also sag. Thereafter, by heat treatment, a coating layer 8 made of a resin material is formed as shown in FIG. 8, thereby completing the exterior packaging.

In this way, the first and second external lead members 3, 4
Since the water-repellent coating 6 is formed on desired portions of the resin material 8' by dipping, when the capacitor element 1 is dipped in the resin material 8' and pulled up, the first and second external lead members 3 and 4 are An appropriate amount of the resin material 8' adhering to the undesired portion (water-repellent film forming portion) hangs down together with the resin material 8' existing between the first and second external lead members. For this reason, it is possible to almost eliminate the resin material 8' from creeping up and adhering to the first and second external lead members 3 and 4, and when mounting the first and second external lead members 3 and 4 on a printed circuit board. Soldering defects to the printed conductor No. 4 can be significantly reduced.

In addition, the formation of the water-repellent coating 6 on the first and second external lead members 3 and 4 is performed on the first and second external lead members 3 and 4 together with the capacitor element 1 on the water-repellent member.
4 is also carried out by immersion, and in addition, the water-repellent coating 6 of the capacitor element 1 is not removed at all and is used as is. 145328), workability can be significantly improved.

Moreover, the impregnating layer 7 made of an impregnating agent is formed on the capacitor element 1 after the formation of the water-repellent coating 6, but the impregnating agent may be compatible with the water-repellent material, so that the water-repellent coating cannot be formed. Regardless of the water repellency of the capacitor element 6, the impregnating agent can be impregnated deep into the capacitor element 1, and the air contained in the pores can be replaced. For this reason, when forming the resin coating layer 8 on the capacitor element 1, even if the capacitor element 1 is heat-treated, almost no trapped air penetrates the resin material and is released to the outside. Excellent appearance characteristics can be obtained without the occurrence of pinholes.

Next, specific examples will be described.

Example 1 A tantalum wire (anode lead) of 0.5φmm was installed in advance in a capacitor element made by press-molding and sintering tantalum powder into a cylinder with a diameter of 3 mm and a height of 4 mm, and this anode lead was drawn out. A first external lead member bent in an L shape and having a wire diameter of 0.5φmm is welded to the part so as to be spaced 1.5mm from the top surface of the capacitor element, and the wire diameter is 0.5φmm.
A second external lead member formed in a straight shape is soldered to the electrode lead-out layer so that the distance from the first external lead member is 5 mm. next,
This capacitor element was manufactured by Daikin Corporation under the trade name Daifree ME104 (for water repellent material), and 5 mm from the bent part of the first external lead member.
Immerse and pull up so that the separated upper part is at the immersion level. Next, without heat treatment, this capacitor element is immersed in Permachine (a water-soluble acrylic resin) manufactured by NCG Corporation in the United States so that the immersion level is 1.0 mm above the top of the capacitor element. Thoroughly impregnate. After pulling, heat at 85°C for 1 hour. After that,
The capacitor element is made of epoxy resin with a viscosity of 30,000 CPS and thixotropic properties.
A tantalum solid electrolytic capacitor is obtained by immersing the first external lead member so that the upper part separated by 4 mm from the bent part is at the immersion level, and then pulling it up and heat-treating it.

In this capacitor, the height of the epoxy resin creeping up to the first and second external lead members (height from the lowest position of the resin material between the first and second external lead members) is average. 0mm (-0.3~
+0.2mm), and no trouble occurred during mounting on the printed board. However, in the conventional example in which no water-repellent coating was formed, creeping adhesion of 1 to 3 mm occurred, resulting in poor soldering.

Furthermore, no pinholes were observed in the epoxy resin coating layer. This is thought to be due to the fact that dye-free and permanent dye are compatible, so that permanent dye can be sufficiently impregnated despite the water-repellent coating being formed in the deep layer of the capacitor element.

Example 2 A capacitor element similar to that in Example 1 was immersed in Toray Silicone SH1107 (oil-based water repellent material) manufactured by Toray Industries, Inc. under the same conditions as in Example 1 and then pulled out. It was immersed in VERSILOK201 (trade name, manufactured by Co., Ltd.) under the same conditions as in Example 1, pulled up, and then heated at room temperature. still,
VERSILOK201 is an oil-absorbing modified acrylic resin with a viscosity of 200 to 300 CPS, and has the property of absorbing oil and maintaining adhesiveness with the substrate. Thereafter, as in Example 1, it is covered with an epoxy resin having a viscosity of 40,000 CPS and thixotropic properties.

In this capacitor, no epoxy resin was observed to creep up and adhere to the first and second external lead members. In addition, some pinholes were observed in the epoxy resin coating layer, but
There was no effect on appearance characteristics.

Example 3 A capacitor element similar to Example 1 was immersed in Toray Silicone SH200 (oil-based water repellent material) manufactured by Toray Industries, Inc. under the same conditions as in Example, and then pulled up. It is immersed in an absorption type epoxy resin under the same conditions as in Example 1, pulled up, and heated at 120°C for 1 hour. Thereafter, it was covered with an epoxy resin having thixotropic properties under the same conditions as in Example 2.

In this capacitor, the creeping height of the epoxy resin to the first and second external lead members was 0.1 mm on average, and no trouble occurred during mounting on the printed board. Furthermore, no pinholes were observed in the epoxy resin coating layer.

Incidentally, in the present invention, the electronic components can be applied not only to solid electrolytic capacitors but also to multilayer ceramic capacitors, varistors, resistors, and the like. Further, impregnation with an impregnating agent can also be carried out during heat treatment of the water-repellent coating. Furthermore, an appropriate auxiliary wrapping step can be added between the impregnation step and the final wrapping step.

As described above, according to the present invention, it is possible to suppress the creeping up and adhesion of the resin material to the external lead member by a simple method to the extent that there is no practical problem, and the occurrence of pinholes in the coating layer caused by the resin material can be suppressed. can also be significantly reduced, and the appearance characteristics can be improved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional solid electrolytic capacitor, Fig. 2 is a side sectional view for explaining the packaging method, Fig. 3 is a side sectional view showing how it is mounted on a printed board, and Figs. 8 is an explanatory diagram of the method of the present invention, FIG. 4 is a side sectional view showing a state in which an external lead member is connected to a capacitor element, FIG. 5 is a side sectional view showing a state in which a water-repellent coating is formed, 6th
The figure is a side sectional view showing the state in which the impregnated layer is formed.
The figure is a side sectional view showing a state in which the capacitor element is immersed in a resin material, and FIG. 8 is a side sectional view showing a state in which the exterior is completed. In the figure, 1 is a component body (capacitor element), 3 and 4 are external lead members, 6 is a water-repellent coating, 7 is an impregnated layer, 8' is a resin material, and 8 is a coating layer.

Claims (1)

[Claims] 1. Forming a water-repellent coating on a desired portion of the external lead member by immersing a component body including a plurality of external lead members extending in the same direction in a water-repellent member such that the external lead members are immersed. , immersing the component body in an impregnating agent that is compatible with the water-repellent member in such a way that the water-repellent coating formed on a desired portion of the external lead member is not immersed; and immersing the component body in a resin material that has thixotropic properties. 1. A method for packaging an electronic component, comprising the step of immersing the external lead member so that the water-repellent coating portion is at the immersion level to cover the main part including the component body.