JPH06275401A - Chip resistor - Google Patents

Abstract

PURPOSE:To provide a chip resistor that may not cause the Manhattan phenomenon at the time of bulk mounting. CONSTITUTION:A chip resistor comprises a substrate 10, on the upper and lower sides of which are formed, respectively, primary electrodes 11a and 12a, and 12a and 12b; secondary electrodes 13 and 14 connecting the primary electrodes on the upper side with the primary electrodes on the lower side; a resistor 15 in contact with the primary electrodes 11a and 12a on the upper side; an undercoat 16 on the resistor 15; a middle coat covering the resistor 15 and the under coat 16; and an overcoat 18 covering the middle coat 17 and the primary electrodes 11a and 12a. The overcoat has cuts. This resistor structure is supported on four corners of the overcoat at the time of bulk mounting.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in chip resistors.

[0002]

2. Description of the Related Art A chip resistor, for example, as shown in FIG. 7, includes a substrate 50 and primary electrodes 51a, 52a and 5 formed on the upper and lower surfaces of the substrate 50 on opposite sides thereof.
1b and 52b, secondary electrodes 53 and 54 for conducting the primary electrodes of the upper and lower surfaces, respectively, and primary electrodes 51a and 51a of the upper surface,
Resistor 55 provided in contact with 52a, and resistor 5
5 is provided with an undercoat 56, a middle coat 57 that covers the resistor 55 and the undercoat 56, and an overcoat 58 that covers the middle coat 57. Here, the undercoat 56, the middle coat 57, and the overcoat 58 form a protective coat.

[0003]

As shown in FIG. 8, the chip resistor as described above may be subjected to bulk mounting (back surface mounting) on the circuit board 60 with the overcoat 58 side facing downward. is there. However, in an ordinary resistor as shown in FIG. 7, the secondary electrode 5 located on the upper surface of the substrate 50 is
Since the surface of the overcoat 58 is higher than the surface of 3, 54, that is, the secondary electrode 5 at the relative end portion on the substrate 50.
Since there is a difference in height between 3, 54 and the overcoat 58,
Solder 60, 6 by reversing resistors as in bulk mounting
When soldering with No. 1, the so-called Manhattan phenomenon in which one side of the resistor is pulled and the other side floats easily occurs.

Therefore, an object of the present invention is to provide a chip resistor in which the Manhattan phenomenon does not occur in bulk mounting.

[0005]

To achieve the above object, a chip resistor according to the present invention comprises a substrate, electrodes provided on both sides of the substrate, and a resistor provided in contact with the electrode. In a chip resistor including a protective coat for covering the resistor, the protective coat is provided on the upper face electrode so as to expose substantially the central portion of the upper face electrode on both sides of the substrate and to extend to the end portions on both sides of the substrate. It is characterized by

[0006]

[Function] Since the protective coat exists up to the end of the upper surface of the substrate and the height difference between the relative end on the substrate and the protective coat disappears due to the extension of the protective coat, bulk mounting in which the protective coat side is mounted on the circuit board is performed. When this is done, the contact area between the protective coat side of the resistor and the circuit board increases, and the resistor is supported by the portions near the four corners of the upper surface of the substrate. That is, at the time of bulk mounting, since the resistors are supported at four places near the corners on the protective coat side, the Manhattan phenomenon does not occur.

[0007]

EXAMPLES A chip resistor of the present invention will be described below based on examples. 1 is an external perspective view of a resistor according to one embodiment, FIG. 2 is a sectional view taken along line AA of FIG. 1, FIG. 3 is a sectional view taken along line BB of FIG. 1, and FIG. 4 shows. This chip resistor includes a substrate 10, primary electrodes 11a, 12a and 11b, 12b formed on the upper and lower surfaces of the substrate 10 on opposite sides thereof, and a secondary electrode 13 for conducting the primary electrodes of the upper surface and the lower surface, respectively. , 14 and the resistor 1 provided in contact with the primary electrodes 11a, 12a on the upper surface.
5, the undercoat 16 applied on the resistor 15, and the middle coat 1 covering the resistor 15 and the undercoat 16.
7 and an overcoat 18 that covers the middle coat 17 and the primary electrodes 11a and 12a. Then, the undercoat 16, the middle coat 17, and the overcoat 18 constitute a protective coat.

In this embodiment, the secondary electrodes 13 and 14 are provided on the overcoat 18 extending to the primary electrodes 11a and 12a on both sides of the substrate 10, and the secondary electrodes 13 and 14 are provided. , Electrodes 12a, 12
b and 14 form electrodes on both sides of the substrate 10 relative to each other. Of the protective coats, overcoat 18
Has a notch 18a, 18b for passing through the primary electrodes 11a, 12a on the substrate 10 and extending to both ends of the substrate 10 on opposite sides, and exposing substantially the central portion of the primary electrodes 11a, 12a. . These notches 18a, 18b
To protect the overcoat 18 from the primary electrodes 11a and 12a.
It is possible to prevent a decrease in contact between the primary electrodes 11a and 12a and the secondary electrodes 13 and 14 due to the provision thereof. That is, as can be seen from FIG. 3, the secondary electrode 13 comes into contact with the primary electrode 11a at the notch 18a, and the primary electrode 1
A sufficient contact area between 1a and the secondary electrode 13 is secured, and conduction between both electrodes 11a and 13 is ensured. Notch 1 as well
Also in 8b, the secondary electrode 14 is in contact with the primary electrode 12a.

As mentioned above, the overcoat 18 is
Except for the notches 18a and 18b, the electrodes extend to above the primary electrodes 11a and 12a on the substrate 10, and the secondary electrodes 13 and 14 are provided on both ends of the overcoat 18 (see FIG. 4). Incidentally, when the overcoat 18 is extended to the end portion of the substrate 10 without forming the notch as shown in FIG. 5, the contact between the primary electrodes 11a and 12a and the secondary electrodes 13 and 14 is the corner portion of the substrate 10. Since the contact area between both electrodes becomes small, the reliability becomes low.

In the chip resistor as described above, since the overcoat 18 is provided up to the upper end of the substrate 10, there is no difference in height between the upper end of the substrate 10 and the overcoat 18. Therefore, in FIG. 6, when the chip resistor is bulk-mounted, portions near the four corners of the substrate 10 (four portions surrounded by circles in FIG. 4) come into contact with the circuit board 20, and the resistor overcoating is performed. Since the contact area between the 18 side and the circuit board 20 is increased and the resistors are supported at the four positions, the Manhattan phenomenon does not occur when soldering with the solders 21 and 22.

In the above resistor, the overcoat 18
In order to form the secondary electrodes 13 and 14 on the ends of the substrate, after forming the overcoat 18 having the shape as shown in FIG. 4, the secondary electrodes 13 and 14 are formed on the side surface and the lower surface of the substrate 10, respectively. It may be formed at the same time (dip). In the above embodiment, only the overcoat 18 of the protective coat is extended to the end of the substrate 10. However, not only the overcoat 18 but also the middle coat 17 or the undercoat 16 is applied to the end of the substrate 10. You may provide up to. In short, in the chip resistor of the present invention,
It suffices that the protective coat is provided up to the end of the substrate in such a manner that the substantially central portion of the upper surface electrode of the substrate is exposed. Also, the electrode is composed of a primary electrode and a secondary electrode.
It is not specified as long as sufficient contact can be made between the electrode conducting to the resistor during bulk mounting and the pattern wiring of the circuit board, and it suffices that the substantially central portion of the upper surface electrode of the board is exposed from the protective coat.

[0012]

As described above, in the chip resistor of the present invention, the protective coat is extended on the upper surface electrode to the end portions on both sides of the substrate by exposing the substantially central portion of the upper surface electrode on both sides of the substrate. , The height difference between the top edge of the board and the protective coat disappears, and the contact area between the protective coat side of the resistor and the circuit board increases during bulk mounting, and the resistor is located at four locations near the four corners of the board. Supported, the Manhattan phenomenon will not occur.

[Brief description of drawings]

FIG. 1 is an external perspective view of a chip resistor according to an embodiment.

FIG. 2 is a cross-sectional view taken along line AA of the chip resistor shown in FIG.

3 is a cross-sectional view taken along line BB of the chip resistor shown in FIG.

4 is a plan view of the chip resistor shown in FIG. 1. FIG.

5 is a plan view for explaining another form of overcoat in the chip resistor shown in FIG. 1. FIG.

FIG. 6 is a diagram showing a state in which the chip resistor shown in FIG. 1 is bulk-mounted.

FIG. 7 is a cross-sectional view of essential parts of a chip resistor according to a conventional example.

FIG. 8 is a diagram showing a state when the chip resistor shown in FIG. 7 is bulk-mounted.

[Explanation of symbols]

 10 Substrate 11a, 12a Primary electrode 11b, 12b on upper surface of substrate 11b, 12b Primary electrode on lower surface of substrate 13,14 Secondary electrode 15 Resistor 18 Overcoat 18a, 18b Notch of overcoat

Claims (1)

[Claims] 1. A chip resistor comprising a substrate, electrodes provided on both sides of the substrate, a resistor provided in contact with the electrode, and a protective coat for covering the resistor, wherein the protective coat is provided. A chip resistor, wherein substantially the central portion of the upper surface electrodes on both sides of the substrate is exposed and the upper surface electrodes are extended to the end portions on both sides of the substrate.