JPH0432741Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to chip-type electronic components in which electrodes for soldering are formed on both ends of a chip-shaped element body, and in particular to miniaturized surface-mounting chips. Regarding type electronic components.

[Prior Art] Chip-type electronic components such as ceramic capacitors, inductors, and resistors mounted on a circuit board have connection electrodes formed on the end faces of the component bodies, and these electrodes are connected to conductors on the circuit board. It is electrically connected by soldering.

To explain this point in detail using a chip resistor as an example, for example, an insulating porcelain cylindrical body with a diameter of 1.25 mm and a length of 2.0 mm is polished at both ends into an arc shape by means such as barrel polishing. The entire surface of the element body is coated with a resistive coating made of carbon, nichrome, etc., and metal caps are fitted to both ends of the element body, and these are used as connection electrodes. Then, the space between the electrodes on the surface of the element body is covered with an insulating resin to protect the resistive film from the outside air.

There is a strong demand for further miniaturization of such chip-type electronic components, and development of miniaturization to meet this demand is being pushed forward. As one response,
A method has been proposed in which the element body is made smaller and a connecting electrode formed of a conductive film is formed directly on the element body without using a metal cap as a terminal.

An example of this will be explained with reference to FIG. 5. For example, in the case of a chip resistor with a diameter of 1.0 mm and a length of 1.6 mm, the insulating porcelain body 1 of the above dimensions is polished to reduce the curvature of the peripheral surface at both ends. Polish so that the radius R is approximately 0.2 to 0.3 mm. Thereafter, a resistive film 2 is formed on the entire surface of the element 1, and both ends of the element 1 are held with chucks, and the resistive film 2 is coated on the central part of the element 1.
Cut into a spiral shape and adjust the resistance between both ends. Thereafter, an insulating paint 4 is applied onto the resistive coating 2 at the center of the element body 1, and is cured to form the same coating 2. Furthermore, element 1
A conductive film is formed by applying a hardened conductive resin paste mainly composed of conductors such as Ag, Cu, or Zn to both ends of the electrode, and baking it, or by plating with Ni, Cu, or solder. Form 3,3. The reason for polishing both ends of the insulating porcelain element 1 in advance is that if there are burrs or the like on both ends of the insulating element 1, the burrs will prevent the element 1 from being gripped with a chuck. This is because if you try to forcefully grasp it, the element body 1 may be damaged.

When such a chip-type electronic component such as a chip resistor is mounted on a circuit board, electrodes are formed on the surface of the circuit board 10 at intervals corresponding to the spacing between the connection electrodes of the chip-type electronic component. A solder paste 12 is applied onto the soldering lands 11, 11, and the connecting electrodes 3, 3 of the chip-type electronic component are placed on top of this, and the adhesive strength of the solder paste 12 is used to connect the chip-type electronic component into a circuit. Temporarily hold on the board. After that, the solder paste 12 is heated,
By reflowing, then cooling and hardening, the connection electrodes 3, 3 are bonded to the soldering land 1.
Solder to 1 and 11.

However, by the above means, the circuit board 1
When soldering chip-type electronic components to
External forces are applied to the chip-type electronic component by an external force applied to both ends of the chip-type electronic component and an external force applied to the chip-type electronic component as the reflowed solder contracts as it hardens. At this time, if there is a difference in the area in which the connection electrodes 3, 3 at both ends of the chip-type electronic component are in contact with the solder paste 12, there will be a difference in the external force applied to both ends of the chip-type electronic component, causing a loss of balance. As shown in FIG. 6, there is a phenomenon in which the chip-type electronic component is pulled to one side, one end of the component separates from the solder paste 12, and the chip-type electronic component stands up using the other end as a fulcrum. When such a phenomenon occurs, the connection of the chip-type electronic component becomes incomplete and the circuit connection becomes defective.

In particular, when both ends of the insulating element 1 are polished and rounded as described above, a relatively thick insulating paint 4 is applied to the center of the allotrope 1, which makes it difficult to complete the finished product. The chip-shaped electronic component bulges in the center and becomes thinner at both ends. For this reason, the chip-type electronic component stands up as shown in FIG. 6 when subjected to a slight external force. As a countermeasure against this problem, for example, a chip-shaped electronic component has been proposed in which both ends of the component body 1 on which the electrodes 3, 3 are formed are larger in diameter than the central part between them, as shown in FIG. .

[Problems to be Solved by the Invention] However, the outer peripheral surfaces of the connection electrodes 3, 3 of the chip-shaped electronic component shown in FIG. 4 are cylindrical surfaces. For this reason, as shown in FIG.
When a chip-shaped electronic component is mounted on the chip-shaped electronic component 11, the connection electrodes 3, 3 of the chip-shaped electronic component are placed on the solder paste 12, 12 on the soldering lands 11, 11 with a certain width. make face-to-face contact with In this case, the center of the chip-shaped electronic component is the soldering land 1.
1 and 11, a part of one of the connection electrodes 3 may come off the soldering land 11, so that the connection electrode 3
On the side, only a width w ₂ of the entire width is in contact with the solder paste 12 . On the other hand, the other connection electrode 3 contacts the solder paste 12 over its entire contactable width w ₁ .

In this way, even if the mounting position of the chip-shaped electronic component on the soldering lands 11, 11 is slightly shifted, the solder paste 1 on both the connecting electrodes 3, 3
Since there are variations in the widths w ₁ and w ₂ of contacting the chips 2 and 12, a difference occurs in the surface tension applied to both ends of the chip-type electronic component when the solder paste is reflowed. As a result, the chip type electronic component is pulled to one side and one end is covered with solder paste.
2, and the same chip-type electronic component stands up.

In addition, chip-shaped electronic components have recently become smaller, so if the connection electrodes 3, 3 are in surface contact with the solder paste 12, 12, when the solder paste 12, 12 is reflowed, the connection will not be possible. The electrodes 3, 3 are lifted up by the surface tension of the solder pastes 12, 12, and the chip-shaped electronic component moves freely.
As a result, even if the chip-shaped electronic component is initially mounted accurately at the center position of the soldering lands 11, 11, the mounting position of the chip-shaped electronic component will shift as a result, resulting in the chip-shaped electronic component as described above. This causes the rise phenomenon of circuit components.

For this reason, even when the chip-shaped electronic component shown in FIG. 4 is used, the phenomenon of the chip-shaped electronic component standing up as shown in FIG. 6 cannot be completely eliminated.

An object of the present invention is to provide a chip-type electronic component that can solve the above-mentioned problems.

[Means for Solving the Problems] In other words, the gist of the means adopted in the present invention to achieve the above object is that electrodes 3, 3 made of conductive films are formed on both ends of the chip-shaped component body 1. In the chip-shaped electronic component, the component element body 1
is a chip-type electronic component that is characterized by exhibiting an hourglass shape in which the diameter is the largest at both ends and gradually decreases toward the center where the diameter is the smallest.

[Function] In the chip-type electronic component according to the present invention, the component body 1 exhibits an hourglass shape in which the diameter at both ends is the largest and the diameter gradually decreases toward the center where the diameter is the smallest. As shown in Figure 3,
When a chip-shaped electronic component is mounted on the soldering lands 11, 11 coated with solder paste 12, 12, the connection electrodes 3, 3 of the chip-shaped electronic component are
A pointed arcuate portion having almost no width rests on the solder pastes 12, 12 on the soldering lands 11, 11. Therefore, even if the center of the chip-shaped electronic component is mounted with a certain degree of deviation from the middle position of the soldering lands 11, 11, both connection electrodes 3, 3 are attached to the solder paste 12, 12 by the same area. Contact.

Furthermore, when the solder pastes 12, 12 are reflowed from this state, since the connecting electrodes 3, 3 rest on the solder pastes 12, 12 in a narrow arc shape, they are not easily affected by the surface tension of the molten solder paste. Moreover, since the gravity of the chip-shaped electronic component is concentrated on the narrow contact line, the solder paste 12, 1 which is melted on the connecting electrodes 3, 3 at an early stage after reflowing.
Embedded in 2. Therefore, when the solder paste is reflowed, the chip-shaped electronic components are less likely to move, and the mounting position does not shift.

[Example] Next, an example of the present invention will be described in detail.

1 and 2 show an embodiment of the present invention, and the structure of the chip resistor according to this embodiment is as follows:
This will be explained along with its manufacturing method.

The component body 1 is made of alumina porcelain and has a length of
It is 1.6 mm in diameter, 1.0 mm in diameter at both ends, and 0.9 mm in diameter at the narrowest part in the center, and is shaped like a drum so that the diameter gradually decreases from both ends to the center. The peripheral edges at both ends of the element 1 are formed with curved surfaces having a radius of curvature R of 0.05 mm, which is usually formed by barrel polishing.

A large number of component bodies 1 are stored in a coating barrel, heated, and while the barrel is rocked, nichrome alloy is sputtered onto the surface of the element body 1 to form a nichrome alloy film as a resistance coating 2. , Next, the component body 1 is moved by the rotating support tool.
While holding both end faces of the element and rotating it, insulating paint 4 is applied to the circumferential surface of the central part of the element body, and on top of the resistive coating 2, insulating paint 4 with a width of 1.0 mm and a film thickness of 0.05 mm is applied. Forms a film of Thereafter, this element 1 is placed in a plating tank, and Ni plating is applied to both ends of the element 1 exposed from the insulating paint 4, and solder plating is applied to the resistive coating 2 on both ends of the element 1. Connection electrodes 3, 3 made of Ni and solder plating film
is formed, thereby completing a chip resistor.

A test was carried out on mounting 1000 chip resistors thus manufactured on a circuit board using the following method. That is, on a circuit board made of glass epoxy resin with copper wiring, soldering lands for soldering the connection electrodes 3, 3 of the chip-type resistors are formed in advance, and solder paste is applied to these lands. On top of this, the chip resistor described above was mounted and soldered. Thereafter, when the soldering state of the chip resistors was visually observed, none of the 1000 chip resistors had one of the connection electrodes 3, 3 peeled off from the soldering land.

For comparison, the above-described No. Using a chip resistor as shown in FIG. 5, a mounting test on a circuit board was carried out in the same manner as in the first embodiment. As a result, as shown in FIG. 6, there were 11 out of 1000 pieces in which one of the connection electrodes 3, 3 had peeled off from the soldering land.

In the explanations so far, the present invention has been applied to a chip resistor, but it goes without saying that the present invention can also be applied to other chip-type electronic components, such as chip-type inductors. As chip-type electronic components become smaller and lighter, it often occurs that one end of the chip-type electronic component stands up as described above during soldering, but this problem can occur regardless of the type of component. However, this problem can be solved by the means proposed in the present invention.

[Effect of the invention] As explained above, according to the invention, when a chip-type electronic component is soldered to a soldering land of a circuit board, the electronic component does not stand up using one end as a fulcrum. , it is possible to achieve the effect that soldering can be performed reliably.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a chip resistor showing an embodiment of the present invention, Fig. 2 is a vertical side view showing the same embodiment, and Fig. 3 is a chip resistor mounted on a circuit board. FIG. 4 is a vertical side view showing a state in which a conventional chip resistor is mounted on a circuit board. FIG. 5 is a vertical side view showing a conventional chip resistor mounted on a circuit board. FIG. 6 is a vertical side view showing the process in which the chip resistor is mounted on the circuit board. 1... Part element body, 2... Resistive film, 3... Connection electrode, 4... Insulating resin.

Claims (1)

[Scope of utility model registration request] In a chip-shaped electronic component in which electrodes 3, 3 made of conductive films are formed on both ends of a chip-shaped component body 1, the component body 1 has the largest diameter at both ends and the smallest diameter at the center. A chip-shaped electronic component characterized by exhibiting an hourglass shape in which the diameter gradually decreases as it goes up.