JPH0870062A - Electronic parts - Google Patents

Abstract

PURPOSE: To provide an electronic component with bumps capable of coping with thermal breakdown which is to be caused by repetition of thermal expansion and thermal contraction. CONSTITUTION: In an electronic component 10 wherein a chip 3 is mounted on the one surface of a board 2, and bumps 4 are formed on the other surface, bumps formed at the positions corresponding with the end surfaces (a) of the chip 3 are made dummy bumps 4b. Thereby, when the dummy bumps 4b are thermally broken down, the life of the electronic component 10 is not affected, because the dummy bumps 4 are meaningless from the circuit viewpoint.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component having bumps.

[0002]

2. Description of the Related Art In recent years, electronic parts having bumps (protruding electrodes) have been gradually and widely used in various electronic devices. FIG. 6 is an explanatory diagram showing a conventional electronic component mounted on a main board and a strain amplitude distribution. This electronic component 1 is configured by mounting a chip 3 on the upper surface of a substrate 2 and forming a large number of bumps 4 made of solder in a matrix on the lower surface. The circuit pattern electrodes (not shown) formed on the surface of the chip 3 are electrically connected to the bumps 4 by a conductive means (not shown). Chip 3 is bond 5
Is fixed to the surface of the substrate 2, and a mold body 6 for protecting the chip 3 is formed on the upper surface of the substrate 2. The electronic component 1 is fixed to the electrodes (not shown) of the main substrate 9 by the bumps 4.

A distortion amplitude distribution chart is shown at the bottom of FIG. When this electronic component 1 is incorporated into an electronic device and a current is applied to the circuit pattern of the chip 3 to drive the chip 3,
The chip 3 generates heat due to internal resistance. This heat is transferred to the substrate 2 and the mold body 6, and the electronic component 1 is thermally distorted. FIG. 6 shows this thermal strain, which the present inventor analyzed and obtained by FEM (finite element method) analysis.

As is clear from this distribution chart, the chip 3
In the bump 4a corresponding to just below the end surface a of the strain amplitude, the strain amplitude is most remarkable. This is because the thermal expansion coefficient of the substrate 2 and the mold body 6 is significantly different from that of the chip 3. Incidentally, for example, the thermal expansion coefficient of a glass epoxy substrate or a molded body is 20 to 60 × 10 ⁻⁶ / ° C., whereas that of the chip 3 is 3 to 4 × 10 ⁻⁶ / ° C., and the former is about 10% of the latter. Double.

[0005]

From the above, the bump 4a at the position corresponding to the end face a of the chip 3 is liable to cause fatigue fracture due to repeated thermal expansion and thermal contraction, and thus the bumps 4a and the electronic component 1 There is a problem that the life of electrical connection with the substrate 9 is shortened.

Therefore, the present invention has been made in consideration of the above points, and copes with repeated thermal expansion and thermal contraction,
An object of the present invention is to provide an electronic component capable of extending the life of electrical connection between the electronic component and the main board.

[0007]

To this end, the present invention provides an electronic component in which a chip is mounted on one surface of a substrate and bumps are formed on the other surface of the substrate at a position corresponding to the end surface of the chip. The bumps to be used are dummy bumps.

Further, in an electronic component in which a chip is mounted on one surface of a substrate and bumps are formed on the other surface, the bump formed at a position corresponding to the end surface of the chip is fixed more firmly than the other bumps. It is used as a reinforcement bump.

[0009]

In the above structure, even if the dummy bumps are broken by fatigue, they do not affect the life of electrical connection between the electronic components and the main substrate.

Further, the reinforcing bumps are less likely to be damaged by fatigue, and the life of electrical connection between the electronic component and the main board is extended.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. 1 is a sectional view of an electronic component according to a first embodiment of the present invention, FIG. 2 is a bottom view of the same, and FIG. 3 is a partial sectional view of the same. Figure 6
The same parts as those of the conventional example shown in FIG.

1 and 2, a large number of bumps 4 are formed in a matrix on the lower surface of the substrate 2 of the electronic component 10. Of these, the bumps at the positions corresponding to the end face a of the chip 3 are dummy bumps 4b. (The dummy bumps 4b are painted black). Dummy bump 4b
Means that it is not electrically connected to the electrodes of the circuit pattern formed on the surface of the chip 3, and is meaningless in terms of the circuit.

As described with reference to FIG. 6, the chip 3
The dummy bump 4b corresponding to the end face a of the has a large strain amplitude, and fatigue destruction occurs due to repeated thermal expansion and contraction, but the dummy bump 4b is meaningless in terms of a circuit, and therefore, even if fatigue fracture occurs, Board and electronic component 10
Does not affect the life of the electrical connection of.

As shown in FIG. 3, the dummy bump 4b of this embodiment is connected to the chip 3 by a heat transfer material 7 such as a metal wire having a high thermal conductivity. Therefore, the heat generated by the chip 3 is transferred to the dummy bumps 4b through the heat transfer material 7 and radiated from the dummy bumps 4b. That is, this dummy bump 4b has a heat dissipation effect, and the dummy bump 4b
The electronic component 10 can be protected from heat generation of the chip 3 by radiating heat from the electronic component 10.

FIG. 4 is a sectional view of an electronic component according to the second embodiment of the present invention. In this electronic component 20, reinforcing bumps 4c are formed at positions corresponding to the end surface a of the chip 3. The reinforcing bumps 4c are larger than the other bumps 4 and are firmly fixed to the lower surface of the substrate 2. Therefore, even if the above-described thermal expansion and thermal contraction are repeated, fatigue fracture is unlikely to occur, and The life of the connection between the component 20 and the main board can be greatly extended.

Next, an example of a method of forming the reinforcing bumps 4c will be described. 5 (a), (b) and (c) are explanatory views of the method for forming the reinforcing bumps according to the second embodiment of the present invention. FIG. 5 (a)
Is a partial plan view of the substrate 2, and FIG. 5B is a partial side view of the same. The solder balls 4 ′ are mounted on the electrodes 8 formed on the upper surface of the substrate 2. Here, one solder ball 4'is mounted on the electrode 8 on which the normal bump 4 is formed, but a large electrode 8'on which the reinforcing bump 4c is formed.
A plurality of (two in this example) solder balls 4'are mounted on the top.

When the substrate 2 is heated in a heating furnace to melt the solder balls 4'and then cooled to be solidified, FIG.
As shown in (c), hemispherical bumps 4 and reinforcing bumps 4c are formed on the electrodes 8 and 8 '. This reinforcement bump 4
The c is formed by fusing two solder balls 4 '. As shown in FIG. 5 (c), the reinforcing bumps 4c are flatter than the normal bumps 4, and are firmly fixed to the electrodes 8'and the upper surface of the substrate 2 in a wider area, so that fatigue fracture occurs. It's difficult.

[0018]

As described above, according to the present invention, it is possible to prevent fatigue damage due to repeated thermal expansion and thermal contraction by the extremely simple means of forming the bumps at the positions corresponding to the end faces of the chips as dummy bumps or reinforcing bumps. As a result, the life of the connection between the electronic component and the main board can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view of an electronic component according to a first embodiment of the present invention.

FIG. 2 is a bottom view of the electronic component according to the first embodiment of the present invention.

FIG. 3 is a partial sectional view of an electronic component according to a first embodiment of the present invention.

FIG. 4 is a sectional view of an electronic component according to a second embodiment of the present invention.

5A is an explanatory diagram of a method for forming a reinforcing bump according to a second embodiment of the present invention. FIG. 5B is an explanatory diagram of a method for forming a reinforcing bump according to a second embodiment of the present invention. Explanatory drawing of the formation method of the reinforcement bump of an Example.

FIG. 6 is an explanatory diagram showing a conventional electronic component and strain amplitude distribution.

[Explanation of symbols]

 2 substrate 3 chip 4 bump 4b dummy bump 4c reinforcing bump 10, 20 electronic component

Claims (3)

[Claims] 1. An electronic component having a chip mounted on one surface of a substrate and bumps formed on the other surface, wherein a bump formed at a position corresponding to an end surface of the chip is a dummy bump. And electronic components. 2. In an electronic component having a chip mounted on one surface of a substrate and bumps formed on the other surface, a bump formed at a position corresponding to an end surface of the chip is stronger than other bumps. An electronic component characterized by being a reinforcing bump fixed to the. 3. The electronic component according to claim 2, wherein the reinforcing bump is formed by fusing a plurality of solder balls.