JPH062241Y2 - Chip resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a chip resistor surface-mounted on a printed wiring board.

[Conventional technology]

FIG. 2 is a sectional view showing a state in which a conventional general chip resistor is mounted on a printed wiring board.

In FIG. 1, a chip resistor 1 has a substantially rectangular parallelepiped ceramic substrate 2 formed by firing and dividing a so-called green sheet in which a slurry is formed into a thin plate, and a side surface of the ceramic substrate 2 is held to reach a top surface and a bottom surface. A pair of electrodes 3, 4,
Nickel plating layers 5 and 6 applied to the surfaces of the electrodes 3 and 4 to prevent silver nicking, and nickel plating layers 5 and 6 to ensure solder wettability. The solder plating layers 7 and 8, a resistor 9 that connects the electrodes 3 and 4 on the top surface of the ceramic substrate 2, and an overcoat 10 such as a glass material that covers the surface of the resistor 9 are used. There is.

When mounting the chip resistor 1 on the printed wiring board 11, the overcoat 10 on the top surface side is suction-chucked by a mount nozzle of an automatic mounting machine (not shown), and pre-paste solder is applied. After mounting the chip resistor 1 by aligning the electrodes 3 and 4 with the pair of lands 12 and 13, the chip resistor 1 is surface-mounted on the printed wiring board 11 by heating in a reflow furnace or the like for soldering. To be done. Reference numerals 14 and 15 in the drawing indicate solder.

[Problems to be solved by the device]

However, in the conventional chip resistor 1 described above, it is difficult to precisely define the thicknesses of the nickel plating layers 5 and 6 and the solder plating layers 7 and 8 formed by barrel plating or the like. Of the printed circuit board 11 and therefore the chip resistor 1
However, there is a problem in that when it is mounted on the lands 12 and 13, a positional deviation easily occurs.

Further, on the top surface side of the chip resistor 1, since a step is formed on the surface and the peripheral edge of the overcoat 10 that covers the resistor 9, air easily leaks at the time of chucking by the mount nozzle, so that a chucking failure occurs. There was also a problem that the mounting rate decreased.

The present invention has been made in view of such circumstances, and an object thereof is to provide a chip resistor that is less likely to cause a chucking defect that is displaced from the land and is suitable for automatic mounting.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides a chip resistor having a pair of electrodes coated with a plating layer on the surface of an insulating substrate having a substantially rectangular parallelepiped shape, and a resistor connecting the two electrodes. Both ends of the bottom surface of the insulating substrate are formed in a concavo-convex shape, the electrodes are provided on the concavo-convex portion, and the resistor is provided at the central portion of the bottom surface of the insulating substrate.

[Action]

By arranging the electrode and the resistor on the bottom surface side of the chip resistor, only the flat surface of the insulating substrate (ceramic substrate) can be exposed on the side surface and the top surface of the chip resistor. The dimensional accuracy is improved, and the positional deviation from the land is less likely to occur, and the top surface of the chip resistor is flattened, and the chucking failure is less likely to occur.
Further, since the electrodes are formed on the concave and convex portions of the insulating substrate to enhance the peeling strength, there is no fear of peeling after mounting even if the electrodes are only on the bottom surface side.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a state in which a chip resistor according to an embodiment of the present invention is mounted on a printed wiring board, and the portions corresponding to those in FIG. 2 are designated by the same reference numerals.

The chip resistor 1 shown in FIG. 1 has concavities and convexities 2a and 2b formed at both ends of the bottom surface of a substantially rectangular parallelepiped ceramic substrate 2, and electrodes 3 and 4 are formed on the surfaces of these concavities and convexities 2a and 2b, respectively.
4 are formed, and nickel plating layers 5 and 6 and solder plating layers 7 and 8 are adhered to the surfaces of the electrodes 3 and 4, respectively. Further, a resistor 9 for connecting the electrodes 3 and 4 is formed at the center of the bottom surface of the ceramic substrate 2, and an overcoat 10 is applied to the surface of the resistor 9. In other words, the chip resistor 1 includes the electrodes 3, 3 covered with the nickel plating layers 5, 6 and the solder plating layers 7, 8.
4 and the resistor 9 covered with the overcoat 10 are all disposed on the bottom surface side, and only the flat surface of the ceramic substrate 2 is exposed on the side surface and the top surface of the chip resistor 1.

The outer dimension L of the chip resistor 1 is equal to the outer dimension of the ceramic substrate 2 defined by the pitch of the dividing grooves of the green sheet, and depends on the thickness of the nickel plating layers 5, 6 and the solder plating layers 7, 8. Since it disappears, the dimensional accuracy is significantly improved. Therefore, this chip resistor 1
The alignment accuracy is improved when the printed circuit board 11 is mounted on the lands 12 and 13 of the printed wiring board 11, and the positional deviation is less likely to occur. Further, since the top surface of the chip resistor 1 is flat, air leakage is less likely to occur during chucking by the mount nozzle, and therefore, chucking failure is less likely to occur as compared with the conventional product. The mounting rate can be significantly increased by automatically performing the mounting using the chip resistor 1 which is less likely to cause the positional deviation from the lands 12 and 13 and the chucking failure.

Furthermore, in the chip resistor 1, since the electrodes 3 and 4 are formed on the surfaces of the irregularities 2a and 2b of the ceramic substrate 2 to enhance the peeling strength, even if the electrodes 3 and 4 only on the bottom surface side are mounted after mounting. There is no need to worry about peeling. In addition, in the conventional product, electrodes are formed by printing not only on the bottom surface of the ceramic substrate but also on the side surface and the top surface, whereas the chip resistor 1 needs to be printed only on the bottom surface. There is also an advantage that you can down. In addition, the unevenness 2a, 2
b may be collectively formed in a pressing process of forming the dividing groove in the green sheet which is the base material of the ceramic substrate 2.

[Effect of device]

As described above, according to the present invention, the electrodes are provided on the uneven portions formed on both ends of the bottom surface of the insulating substrate (ceramic substrate), and the resistor is provided on the central portion of the bottom surface of the insulating substrate. The accuracy of the external dimensions is improved, the positional deviation from the land is unlikely to occur, the top surface is flat and chucking failure is less likely to occur, and the number of steps can be reduced because the electrodes can be provided only on the bottom side. It is possible to provide a chip resistor that is suitable for mounting and that can reduce the cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which a chip resistor according to an embodiment of the present invention is mounted on a printed wiring board, and FIG. 2 is a sectional view showing a state in which a conventional general chip resistor is mounted on a printed wiring board. . 1 ... Chip resistance, 2 ... Ceramic substrate (insulating substrate), 2a, 2b ... Roughness, 3, 4 ... Electrode, 5, 6 ...
… Nickel plated layer, 7, 8 …… Solder plated layer, 9…
... resistor, 10 ... overcoat, 11 ... printed wiring board, 12,13 ... land.

Claims (1)

[Scope of utility model registration request] 1. A chip resistor surface-mounted on a printed wiring board, comprising a pair of electrodes coated with a plating layer on the surface of a substantially rectangular parallelepiped insulating substrate, and a resistor for connecting the two electrodes together. A chip resistor, characterized in that both ends of a bottom surface of the insulating substrate are formed in a concavo-convex shape, the electrodes are provided on the concavo-convex portion, and the resistor is provided at a central portion of the bottom surface of the insulating substrate.