JPH0432234A - Bump structure for flip-chip bonding - Google Patents

Abstract

PURPOSE:To prevent nearly no shape change from being produced even after joint by forming each of two solder bumps with different melting points on a surface of a semiconductor element and a substrate and achieving a minimum required size when performing fluxing junction of the solder bump at a low melting-point side. CONSTITUTION:A semiconductor element 1 where a solder bump 4A at a high melting-point side is formed and a substrate 2 where a solder bump 4B at a low melting-point side is formed are positioned. Then, both are pressed together by a specified load. Finally, the entire body is heated to a temperature exceeding the melting point of the solder bump 4B and below a melt point of the solder bump 4A and allows only the solder bump 4B at the low melting-point side to be melted. Then, a size of the solder bump 4b at the low melting-point side is minimized enough for performing fluxing joint, thus enabling reduction in height and width in a junction part after performing fluxing joint of the semiconductor element 1 and the substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for electrically connecting semiconductor devices, and particularly to improving the structure of bumps used in flip chip bonding.

[Prior Art] FIGS. 2(a) to 2(C) are cross-sectional views showing a conventional flip chip bonding vibe structure and its operation. In the figures, 1 is a semiconductor element, and 2 is a semiconductor element 1.
3 are solder bumps for electrically connecting the semiconductor element 1 and the substrate 2.

Next, the operation will be explained.

For example, the semiconductor element 1 and the substrate 2 each having a solder bump 3 formed thereon by a vapor deposition method are aligned (FIG. (a))
.

Next, press both together with a predetermined load (Figure (b))
.

Finally, the whole is heated to a temperature higher than the melting point of solder bump 3 to melt and join the solder bumps on both sides (Figure (C)
)).

[Problem to be Solved by the Invention] Since the conventional bump structure for flip chip bonding is configured as described above, the shape of the solder bump after melt bonding has a height as shown in FIG. 2(C). decreases and width increases. Due to this shape change, for example, the heat cycle resistance of the bond deteriorates due to a decrease in height, and the pitch between adjacent solder bumps cannot be reduced due to an increase in width, for example. There was a point.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a bump structure for flip chip bonding that hardly changes in shape even after bonding.

[Means to solve the problem]

The bump structure for flip chip bonding according to the present invention forms two types of solder bumps with different melting points on a semiconductor element and a substrate, respectively, and reduces the size of the solder bump on the lower melting point side to the minimum size necessary for melting and bonding. This is what I did.

[Effect]

In this invention, two types of solder bumps with different melting points are formed on the semiconductor element and the substrate, respectively, and the solder bumps on the lower melting point side are reduced in size to the minimum necessary size, and only the solder bumps on the lower melting point side are melted. Since the parts are joined together, almost no change in shape occurs even after joining.

〔Example〕

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

1(a) to 1(C) are cross-sectional views showing the bump structure for flip chip hoarding and its operation according to the present invention, and the same reference numerals as in FIG. 2 indicate the same or corresponding parts, and 4
A is a solder bump on the high melting point side formed on the semiconductor element 1, and 4B is a solder bump on the low melting point side formed on the substrate 2.

Next, the operation will be explained.

Semiconductor element 1 with solder bumps 4A formed on the high melting point side
and the substrate 2 on which the solder bumps 4B on the low melting point side are formed are aligned (FIG. (a)).

Next, press both together with a predetermined load (Figure (b))
.

Finally, the whole is heated to a temperature higher than the melting point of the solder bumps 4B and lower than the melting point of the solder bumps 4A to melt and join only the solder bumps 4B on the lower melting point side.

In this embodiment, the solder bumps 4A having a higher melting point than the opposing solder bumps 4B are provided on the semiconductor element 1, and the shape of the lower melting point side solder bumps 4B is adapted to perform melt bonding. Since the size is set to the minimum necessary size, it is possible to reduce the reduction in height and width at the bonded portion after the semiconductor element 1 and substrate 2 are melt-bonded, thereby improving the heat cycle resistance of the bond. deterioration of the solver bumps can be reduced, and the pitch between the solver bumps can be reduced.

In the above embodiment, the solder bumps 4A on the high melting point side are formed on the semiconductor element 1, and the solder bumps 4B on the low melting point side are formed on the substrate 2. The solder bumps 4B and the high melting point side solder bumps 4A may be formed on the semiconductor element 1 and the substrate 2, respectively.

Further, in the above embodiment, an example was shown in which the semiconductor element 1 and the substrate 2 were bonded, but even if they were bonded using solder bumps,
For example, it goes without saying that it can also be used to bond semiconductor elements or substrates together.

[Effects of the Invention] As described above, according to the bump structure for flip chip bonding according to the present description, two types of solder bumps with different melting points are used, and the solder bump on the lower melting point side is made to the minimum necessary size, Since only the solder bumps on the low melting point side are melted and bonded, there is almost no change in shape even after melt bonding, there is no deterioration in the heat cycle resistance of the bond, and the pitch of the solder bumps is This has the effect that it can also be made smaller.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are cross-sectional views showing a bump structure for flip chip bonding and its operation according to an embodiment of the present invention, and FIGS. 2(a) to (C) are cross-sectional views of a conventional bump for flip chip bonding. FIG. 3 is a cross-sectional view showing the structure and its operation. 1 is a semiconductor element, 2 is a substrate, 4A is a solder bump on the high melting point side, and 4B is a solder bump on the low melting point side. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 1

Claims (1)

[Claims] (1) In the solder bumps formed on the surfaces of the semiconductor element and the substrate for electrically connecting the semiconductor element and the substrate on which it is mounted, two types of solder bumps with different melting points are used for the semiconductor element and the substrate on which the semiconductor element is mounted. A bump structure for flip chip bonding, which is formed on the surface of a substrate and has a minimum size necessary for melting and bonding a solder pipe on the low melting point side.