JPH06268018A - Method for mounting electronic component provided with bump - Google Patents

Abstract

PURPOSE:To provide a method for mounting an electronic component provided with a bump so as to surely bond a bump on the electrode of a substrate and perform accurate defect judgement. CONSTITUTION:A bump 4 heated and melted by reflow process is diffused on the electrode 6 of a substrate 5 so as to permit the cross-section shape to be trapezoid by forming the area of the electrode 6 of the substrate 5 larger than the area of the electrode of an electronic component 2. Since the cross-section shape of the bump 4 changes to be trapezoid and the height remarkably reduces at the time of reflowing, the problems of the bump height nonuniformity and the warping of the substrate 5 are solved and all of the bumps 4 can be bonded with the electrodes 6 of the substrate 5. Bonding defects can be accurately judged by measuring the flat area of the bump 4 at the time of reflowing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to bond bumps to electrodes on a substrate by landing bumps protruding from electrodes of electronic parts on electrodes on the substrate and then performing reflow treatment to heat and melt the bumps. The present invention relates to a method for mounting a bumped electronic component.

[0002]

2. Description of the Related Art Electronic components with bumps have become more popular in recent years because their mounting area can be made smaller than that of electronic components with leads. FIG. 8 is a side view of a conventional bumped electronic component mounted on a substrate. Electronic component with bump 1
Is formed by protruding bumps (protruding electrodes) 4 on the electrodes 3 of the electronic component 2. After the bumps 4 are landed on the electrodes 6 of the substrate 5, a reflow process is performed to heat and melt the bumps 4. By doing so, the bump 4 is bonded to the electrode 6.

FIG. 9 is a partially enlarged view of the bump 4 before it is bonded to the electrode 6 of the substrate 5. The bump 4 has a substantially spherical cross section. Further, FIG. 10 is a partially enlarged view after bonding, and the bump 4 is crushed by the surface tension during heating and melting and the self-weight of the electronic component 2 to have a slightly flat cross-sectional shape.

The number of bumps 4 protruding from the electronic component 2 is
Generally, the number is 10 or more, or several 100 or more, which is extremely large, but all the bumps 4 must be surely landed on the electrodes 6 of the substrate 5 to be bonded, and even one bump 4 with a defective bonding is present. Then, it becomes a defective product.

[0005]

However, variations in the height d1 of the bumps 4 are unavoidable in manufacturing, and warping of the substrate 5 is unavoidable in manufacturing. The mounting method has a problem that it is quite difficult to surely land and bond the large number of all the bumps 4 on the electrodes 6 of the substrate 5. Incidentally, the bumps 4 are formed by a screen printing method, a plating method or the like.

After mounting the electronic component 1 with bumps on the substrate 5, it is necessary to inspect whether or not the bumps 4 are firmly bonded to the electrodes 6 of the substrate 5. However, in the conventional mounting method, good bonding is achieved. Since there is not much difference in shape between the bumps 4 with defective bonding, there is a problem that it is difficult to obtain a highly reliable pass / fail judgment result even if an external appearance inspection using soft X-rays is performed.

By the way, the larger the difference Δd = d1-d2 between the height d1 of the bump 4 before reflow shown in FIG. 9 and the height d2 of the bump 4 after reflow shown in FIG. As the height of the bumps 4 shrinks, variations in the height of the bumps 4 and the warp of the substrate 5 can be absorbed, and all the bumps 4 can be reliably bonded to the electrodes 6 of the substrate 5. Further, the more the shape of the bump 4 shown in FIG. 9 differs from the shape of the bump 4 shown in FIG. 10, the easier it is to perform the visual inspection of the good / bad bonding for visual inspection.

Therefore, the present invention has been made in consideration of the above points, and it is possible to reliably bond all the bumps of the electronic component to the electrodes of the substrate, and the bonding is good and the bonding is defective in the visual inspection after mounting. It is an object of the present invention to provide a mounting method of an electronic component with bumps capable of accurately determining.

[0009]

For this reason, in the method of mounting an electronic component with bumps according to the present invention, the area of the electrode of the substrate is formed larger than the area of the electrode of the electronic component, so that it is heated and melted in the reflow process. The bumps are diffused on the electrodes of the substrate so that the cross-sectional shape is trapezoidal.

[0010]

According to the above construction, since the bumps heated and melted during reflow diffuse on the electrodes of the substrate having a large area, the cross-sectional shape becomes a trapezoid. Therefore, the bump height before reflow and the bump after reflow are increased. The difference in height becomes large, and the contraction of the height of the bumps absorbs the variation in the height of the bumps and the warp of the substrate, so that all the bumps can be bonded to the electrodes of the substrate. After the reflow, the flat area of the bump becomes significantly larger than that before the reflow. Therefore, by measuring the flat area of the bump using, for example, soft X-ray, it is possible to judge whether the bonding is good or the bonding is defective. Can be done accurately.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a perspective view of an electronic component with bumps and a substrate before mounting. The electronic component 1 with bumps is formed by protruding bumps 4 on electrodes 3 formed on the lower surface of the electronic component 2. The bumped electronic component 1 is the same as the conventional bumped electronic component described above. Further, the electrode 6 is formed on the upper surface of the substrate 5 by an etching method or the like.
The area of the electrode 6 of the substrate 5 is made considerably larger than the area of the electrode 3 of the electronic component 2. The electrodes 3 and 6 of this example
The planar shape of is circular, but may be rectangular or the like.

The electronic component 1 with bumps is applied to the electrodes 6 of the substrate 5 with flux, then the bumps 4 are landed on the electrodes 6 and mounted on the substrate 5, and then a reflow process is performed. FIG. 2 is a sectional view showing the internal structure of the reflow apparatus. Inside the heating chamber 11, a conveyor 1 that conveys the substrate 5
2 is provided, and a heater 13 and a fan 14 are provided above the conveyor 12. 15 is fan 1
4 is a driving motor. A cooling chamber 16 is provided behind the heating chamber 11, and a cooling fan 14 is provided in the cooling chamber 16.

While the substrate 5 is conveyed rightward by the conveyor 12, the air heated by the heater 13 is blown onto the substrate 5 by the fan 14 to heat and melt the bumps 4 for reflow processing, and then the substrate 5 is placed in the cooling chamber 16. By blowing cold air onto the bumps 4, the heated and melted bumps 4 are cooled and solidified. As the reflow device, a nitrogen reflow device that supplies nitrogen gas to the heating chamber can also be applied.

FIG. 3 is a side view of the electronic component 1 with bumps and the substrate 5 after reflow, and FIG. 4 is a partially enlarged view thereof. As shown in the figure, the area of the electrode 6 of the substrate 5 is equal to that of the electrode 3 of the electronic component 2.
Since the bumps 4 are heated and melted during reflow, the bumps 4 flow over the entire surface or almost the entire surface of the electrode 6 to have a trapezoidal cross section, and the height d2 thereof is the height d1 before reflow (see FIG. 8) and contracted significantly,
The difference Δd = d1-d2 is considerably larger than that in the conventional case. Therefore, the height variation of the bumps 4 and the substrate 5
Warp is sufficiently absorbed and all the bumps 4 are firmly bonded to the electrodes 6 of the substrate 5.

FIG. 5 is a side view of the substrate 5 on which the bumped electronic component 1 is mounted, which is observed by a soft X-ray apparatus, in which 17 is a soft X-ray irradiation unit and 18 is an image receiving unit. Further, FIG. 6A is an image of the bumps 4 obtained by the soft X-ray apparatus before the reflow, and FIG. 6B is an image after the reflow. Soft X
Since the line penetrates the electronic component 2 and the substrate 5, an image of the bump 4 can be obtained. As shown in the drawing, after the reflow, the bumps 4 are diffused over the entire surface of the electrode 6 of the substrate 5, so that the plane area thereof is significantly larger than that before the reflow. By the way, since the bumps 4 that cannot land on the electrodes 6 of the substrate 5 cannot diffuse on the electrodes 6 of the substrate 5, their planar shape remains the small area shown in FIG. 6A even after the reflow. Therefore, by observing the plane area of the bump 4 with a soft X-ray after the reflow and measuring the size of the plane area, it is possible to accurately determine whether the bonding is good or the bonding is defective.

7A, 7B and 7C show soft X-ray images when the planar shape of the electrode 6 is a quadrangle.
7A is an image before reflow, and FIGS. 7B and 7C are images after reflow. In the structure shown in FIG. 7B, the bumps 4 are diffused over the entire surface of the electrodes 6 by reflow and the bumps 4 are formed.
The plane shape of is a square and is a good product. On the other hand, in the case shown in FIG. 7C, the bumps 4 have not been sufficiently diffused by the reflow, and the planar shape thereof is still circular, which is a defective product. Therefore, if the planar shapes of the electrode 3 and the electrode 6 are made different in this way, it is possible to easily determine the quality based on the planar shape of the bump 4 after the reflow. The shape of the electrode 6 may be a hexagon or the like other than the square.

The present invention is not limited to the above-described embodiments, and for example, the bumped electronic component can be applied to a multi-chip package type bumped electronic component in which a plurality of chips are packaged.

[0019]

As described above, according to the method for mounting electronic components with bumps of the present invention, the bumps that are heated and melted during reflow diffuse on the electrodes of the substrate having a large area, so that the cross-sectional shape is trapezoidal. Therefore, the difference between the height of the bumps before reflow and the height of the bumps after reflow becomes large, and variations in bump heights and warpage of the substrate can be absorbed to bond all the bumps to the electrodes of the substrate. After the reflow, the flat area of the bump becomes significantly larger than that before the reflow. Therefore, by measuring the flat area of the bump using, for example, soft X-ray, it is possible to judge whether the bonding is good or the bonding is defective. Can be done accurately.

[Brief description of drawings]

FIG. 1 is a perspective view of a bumped electronic component and a substrate according to an embodiment of the present invention.

FIG. 2 is a sectional view of a reflow apparatus according to an embodiment of the present invention.

FIG. 3 is a side view of a bumped electronic component and a substrate after reflow according to an embodiment of the present invention.

FIG. 4 is a partially enlarged view of a bumped electronic component and a substrate after reflow according to an embodiment of the present invention.

FIG. 5 is a side view of a soft X-ray apparatus according to an embodiment of the present invention.

6A is an image diagram of bumps before reflow according to an embodiment of the present invention. FIG. 6B is an image diagram of bumps after reflow according to an embodiment of the present invention.

7A is an image diagram of bumps before reflow according to another embodiment of the present invention. FIG. 7B is an image diagram of bumps after reflow according to another embodiment of the present invention. FIG. 7C is another embodiment of the present invention. Image of bump after reflow

FIG. 8 is a side view of a conventional electronic component with bumps and a substrate after reflow.

FIG. 9 is a partially enlarged view of a conventional electronic component with bumps and a substrate before reflow.

FIG. 10 is a partially enlarged view of a conventional electronic component with bumps and a substrate after reflow.

[Explanation of symbols]

 1 Electronic component with bump 2 Electronic component 3 Electrode 4 Bump 5 Substrate 6 Electrode

Claims (1)

[Claims] 1. A bumped electronic component for bonding a bump to an electrode of a substrate by landing a bump protruding from an electrode of the electronic component on the electrode of the substrate and then performing reflow treatment to heat and melt the bump. In the mounting method, by forming the area of the electrode of the substrate larger than the area of the electrode of the electronic component, the bumps heated and melted in the reflow process are diffused onto the electrode of the substrate to have a cross-sectional shape. A mounting method for an electronic component with bumps, which is characterized by a trapezoidal shape.