JP3127437B2 - Square chip electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in square chip electronic components such as square chip fixed resistors and multilayer chip capacitors.

[0002]

2. Description of the Related Art As a rectangular chip-shaped electronic component, terminal electrodes are provided on opposite sides of the chip component, and a portion of the terminal electrode near an edge of a chip of an upper surface electrode formed on the upper surface of the chip component is exposed. In some cases, a protective film is provided on the upper electrode. As an example, in the square chip fixed resistor, as shown in FIG. 3, for example, a resistor film (not particularly shown) is provided on an alumina substrate 20, and the resistor film is entirely covered with a protection film 22 and protected. ing. Electrodes 30, 40 are formed on both left and right sides of the alumina substrate 20, respectively. The left and right terminal electrodes 30, 40 are upper surface external electrodes 31, 41, side surface external electrodes 32, 42, and lower surface external electrodes 33, 43, respectively. It is composed of Of these, the upper surface external electrodes 31 and 41 are covered with the protective film 22 except for portions near the edges.

When a chip resistor having such a structure is wired on a substrate, for example, as shown in FIG.
Generally, the left and right electrodes 30, 40 of the resistor 50 are soldered and fixed to the copper wiring 71 on the substrate after the 0 is mounted on the substrate 70. At this time, soldering is performed on the lower external electrode 3
3, 43 and the side external electrodes 32, 42 as well as the upper external electrodes 31, 41, and the solder 60 is raised on the upper external electrodes 31, 41 as shown by oblique lines in the figure.

[0004]

When such soldering is performed, a temperature difference between the soldered portion and the outside air, particularly a "temperature cycle test" (a chip component such as a chip resistor) required in the automobile industry. At -50 ° C. for 15
After holding for about 30 minutes, the temperature is raised to about 150 ° C. and the cycle of holding for about 15 to 30 minutes is also repeated about 1000 times). Then, a tensile stress is generated in the upper external electrodes 31 and 41, and a crack may be generated from the inside of the electrodes, the electrodes may be separated, or the alumina substrate 20 may be broken. In particular, when these damages are remarkable, for example, cracks that traverse the upper surface external electrodes 31 and 41 occur and the electrodes are separated, or the electrodes 31 and 41 are peeled off and the contact with the resistor film is cut off. In this case, a disconnection failure occurs.

The mechanism of the above-mentioned stress generation will be described in more detail with reference to FIG. Alumina substrate 2
The resistor film 21 provided on the upper surface 0 and the upper surface external electrode 41 on the left side are connected to each other in an overlapped state at their mutual ends. 2
2 coated. Note that a Ni plating film 80 for preventing solder erosion is formed on the electrode 41. Here, when a temperature difference occurs in the soldered portion after the Sn / Pb plating film and the solder 81 are further applied on the electrode 41 and the soldering is completed, the tensile stress in the direction of arrow A is applied to the metal portions 80 and 81. A tensile stress in the direction of arrow B is generated in the glassy protective film 22. In general, since the expansion and contraction ratio of metal is greater than that of glass, a "deviation stress" in the direction of arrow C occurs on the electrode 41 due to the difference between the two stresses a and b. This by "shear stress", which is a translation of the above-mentioned problems is Ru Oko Pull <br/>.

[0006] This kind of problem is not limited to the above-mentioned square chip fixed resistors, but also applies to all square chip components such as multilayer chip capacitors. This is extremely undesirable because strict reliability is required for chip components such as chip resistors. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to eliminate disadvantages caused by soldering various rectangular chip-shaped electronic components including the above-described conventional rectangular chip fixed resistors.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventors have worked diligently on the causal relationship between the shape and size of the protective film covering the upper electrode and the above-mentioned problems, and as a result, have found that The length (l) of the protective film in the direction connecting the side surfaces on which the terminal electrodes are formed is the length (L) of the upper surface of the substrate in the same direction.
And the side of the protective film on which the terminal electrode is formed.
If the side surface of the substrate coincides with the terminal electrode forming side surface of the substrate, and the length of the protective film in the direction connecting the terminal electrode non-forming side surfaces of the substrate is substantially equal to the length of the substrate upper surface in the same direction, the "deviation stress" The present inventors have found that no occurrence occurs on the upper surface electrode, and have completed the present invention.

The length (l) of the protective film in the direction connecting the side faces of the substrate on which the terminal electrodes are formed is equal to the length (L) of the upper surface of the substrate in the same direction, and the length of the protective film in the direction of the terminal electrodes formation
The side surface of the side surface coincides with the terminal electrode forming side surface of the substrate ,
In addition, since the length of the protective film in the direction connecting the side surfaces on which the terminal electrodes are not formed is substantially equal to the length of the upper surface of the substrate in the same direction, substantially all of the upper surface electrode is covered with the protective film, and the upper surface electrode is Since it is hardly exposed to the edge, and the difference in expansion / shrinkage ratio between the soldered portion, which is a metal portion, and the glassy protective film is substantially eliminated, the “deviation stress” described with reference to FIG. No longer occurs. As a result, there are almost no problems such as cracking or peeling of the upper electrode, cracking of the alumina substrate, and disconnection failure caused by these.

However, the width of the protective film ( the terminal electrode of the substrate
The length in the direction connecting the formation side surfaces ) need not be the same as the width l of the upper surface of the substrate ( the length in the same direction), like the length l, and the ease of mounting the chip components on the substrate can be improved. Considering the above, it may be the same as the conventional one.

As understood from the above description, the chip-shaped electronic component according to the present invention is provided with terminal electrodes on opposite sides of a substrate, and a protective film is formed on an upper electrode of the terminal electrodes on the upper surface of the substrate. , And specific examples thereof include a square chip fixed resistor, a multilayer chip capacitor, and the like.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a rectangular chip-shaped electronic component of the present invention will be described in detail with reference to embodiments. However, in the following embodiments, a square chip fixed resistor will be described as a typical example of a chip component.

FIG. 1 is a perspective view of one embodiment (a plating film 1).
7, 17 'and the plating films 18, 18')
Shows a cross section taken along line AA in FIG. Alumina substrate 1
A resistor film 2, an internal protection film 3 covering the resistance film 2, and another internal protection film 4 covering the internal protection film 3 are provided in this order. Note that a laser trimming groove 5 is formed substantially at the center of the resistor film 2. On the opposite sides of the substrate 1, for example, upper electrodes 10, 10 'made of an Ag / Pd-based conductive paste and an Ag-based conductive paste, and an Ag-based conductive paste electrically connected to the electrodes, for example. Side electrodes 11, 11 'made of
1, 11 'are lower surface electrodes 12, 1 on the lower surface of the substrate 1.
2 '. Ni plating films 17 and 17 'are formed on the side electrodes 11 and 11' to prevent solder erosion.
And Sn / Pb plating films 18 and 18 '.
Here, the terminal electrodes are the upper electrodes 10, 10 ',
It is composed of side electrodes 11, 11 ', Ni plating films 17, 17', and Sn / Pb plating films 18, 18 '.

Further, the outer protective film 6, which is a feature of the present invention, covers most of the inner protective film 4 and the upper electrodes 10, 10 '. That is, in the present embodiment, the base electrodes 10 and 10 '
The length 1 of the protective film 6 in the direction connecting the terminal electrode forming side surfaces of the plate 1 is equal to the length L of the upper surface of the resistor (substrate 1) in the direction, and the upper electrodes 10, 10 'are completely covered by the protective film 6. It is a covered embodiment (see FIG. 1). In addition,
The width of the protective film 6 (the length in the direction connecting the side surfaces on which the terminal electrodes are not formed of the substrate 1 ) is the same as the conventional width of the upper surface of the resistor (also the
(Length in the direction connecting the side surfaces of the substrate 1 where the terminal electrodes are not formed )
And the inner protective film 4 is exposed from the edge in the transverse direction.

Such a resistor is, as shown in FIG.
When mounted on a glass epoxy board 70 and soldered,
Since the upper electrodes 10, 10 'are covered with the glassy outer protective film 6, the solder does not adhere to the metallic upper electrodes, and the same metallic side electrodes 11, 11' and lower electrodes 1
Only 2, 12 'is soldered, so that a large amount of solder does not adhere to the upper surface electrode as in the conventional case. As a result, the "displacement stress" caused by the temperature difference between the upper surface electrodes 10, 10 '.
Is almost eliminated, and the occurrence of cracks or peeling of the upper electrode can be avoided.

[0015]

Since the rectangular chip-shaped electronic component of the present invention is configured as described above, the upper electrode is almost covered with the protective film. As a result, no solder adheres to the upper electrode. "Displacement stress" hardly occurs on the upper electrode. Therefore,
It is possible to prevent cracking or peeling of the upper electrode, cracking of the substrate, and disconnection failure of the electrode caused by these, due to "shift stress". In addition, the structure simplifies the manufacturing process because the terminal electrode is formed after forming the protective film (because the protective film is formed before the substrate is divided).

[Brief description of the drawings]

FIG. 1 is a perspective view showing a chip resistor as a typical example of a chip-shaped electronic component of the present invention.

FIG. 2 is a cross-sectional view of the resistor shown in FIG. 1 taken along line AA.

FIG. 3 is a perspective view showing a conventional general chip resistor.

FIG. 4 is a sectional view showing a state when the conventional resistor as shown in FIG. 3 is soldered on a substrate.

FIG. 5 is an explanatory diagram for explaining a mechanism in which “displacement stress” occurs in an upper electrode in a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Alumina substrate 2 Resistor film 3, 4 Internal protective film 6 External protective film 10, 10 'Upper surface electrode 11, 11' Side surface electrode 12, 12 'Lower surface electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Etsuji Miyanaga 21 Ryosaki-cho, Saiin-ku, Ukyo-ku, Kyoto Inside ROHM Co., Ltd. , U) Hikaru 3-10270 (JP, U)

Claims (1)

(57) [Claims] 1. A rectangular chip-shaped electronic component having terminal electrodes provided on opposite sides of a substrate and having an upper electrode formed on the upper surface of the substrate and a protective film formed on the upper surface of the substrate, wherein the terminal electrodes of the substrate are formed. The length (l) of the protective film in the direction connecting the side surfaces is equal to the length (L) of the upper surface of the substrate in the same direction, and the length of the protective film on the side where the terminal electrode is formed is located.
The side surface coincides with the terminal electrode forming side surface of the substrate , and
A rectangular chip-shaped electronic component, wherein the length of the protective film in a direction connecting the side surfaces on which the terminal electrodes are not formed of the substrate is substantially equal to the length of the upper surface of the substrate in the same direction.