JPH02105420A - Flip-flop element - Google Patents

Abstract

PURPOSE:To surely execute a molten connection between solder bumps, in the central part on long sides, to be bent at a load and substrate electrodes by a method wherein the solder bumps in the central part on the long sides are formed so as to have a higher shape than solder bumps concentrated and arranged on short sides. CONSTITUTION:A diameter and a height of solder bumps 1' in the central part on long sides are set to be larger than those of solder bumps 1 on short sides of a flip-chip element 10. Thereby, the element 10 is sucked by using a collet 2; the bumps 1, 1' are aligned with electrodes 4 on a substrate 3 and are fixed temporarily by applying a load; after that, it is possible to prevent the central bumps 1' from being separated from the electrodes and from reflowing when a warp of silicon is restored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flip chip device, and particularly to the structure of a flip chip device for an LSI device, such as a memory device.

[Conventional technology]

FIGS. 2 and 3 are plan views of conventional flip chip devices, respectively.
As shown in the figure, solder bulbs 1 are placed at approximately equal intervals around a relatively small sized element of 3 ff 1 m to 5-1 square.
Normally, all the solder bumps 1 are arranged evenly on the four sides of the chip, or as shown in Fig. 3, the - part 1' is arranged almost at the center on the long side. However, most of the others are arranged near the short side. The latter arrangement structure of solder bumps has recently been rapidly developed with the aim of achieving higher density and higher functionality.
This is for large LSI elements such as ``'', and is adapted to the trend of face-down bonding and mounting. In this case, the bump electrodes on the memory element are arranged so as to be suitable for a structure in which a commercially available package can be used, and the memory element is connected to the lead frame by wire bonding and sealed with resin by transfer molding.

[Problem to be solved by the invention]

However, the structure of the flip chip device in which the solder bump is formed approximately at the center of the long side has the following drawbacks. This inconvenience occurs when mounting on a board.

Figures 4(a) to (C) are normal process diagrams for mounting a flip chip element on a substrate. - Pick up the back side of the chip element J with the collet 2, align the solder bumps 1, 1' on the flip chip element (■) with the electrodes 4 on the substrate 3, and then flip it by applying a load of 200 to 400 gr. Temporarily fix the chip element (Fig. 4(b)), then release the adsorption of collet 2 and remove the collet 2.
The solder is removed from the back surface of the flip chip element [Fig. 4(c)], and the solder is melted by an infrared reflow method or the like to fix the solder on the flip chip element. However, in the case where the solder pan 11' is formed approximately in the center of the long side, when the flip chip 1'' is temporarily fixed by applying a load, the flip chip element 11' is not fixed as shown in FIG. The silicon, which is the base material of 10, warps and the amount of solder bump collapse tends to be small on the short sides and large at approximately the center on the long sides.Therefore, the collet 2 is released from adsorption, and the flip chip When the collet 2 is removed from the back surface of the board 1o, the warp of the silicon returns, so the solder pan 71', which is located approximately in the center on the long side, is connected to the electrode 8i!4 on the board, as shown in FIG. 5(b). At this time, the gap X between the solder pan 11' and the electrode 4 on the board is as much as 10 to 20 μm.Therefore, even if reflow is performed with such a gap Only the solder bump 1' approximately in the center of is connected to the electrode 4 on the board.
They do not melt and connect, which impairs manufacturing yield, and even if they are melt-connected initially, they separate later, reducing reliability. This is a problem that first became apparent when flip-chip devices, which are large LSI devices, have solder bumps approximately in the center of their long sides.

An object of the present invention is to provide a flip chip element having a structure that ensures reliable fusion connection between the solder bump at the center of the long side and the substrate electrode.

[Means to solve the problem]

According to the present invention, the flip chip device includes solder bumps that are concentrated on the short side and solder bumps that are formed at approximately the center on the long side so as to have a higher shape than the solder bumps on the short side. The configuration includes a bump.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1(a), 1(b), and 1(c) are a plan view of a flip chip device and a cross-sectional structural view of its solder bumps, respectively, showing an embodiment of the present invention. According to this embodiment, the solder bump 1 on the short side has a diameter D=125 to 130 μm and a height H=9, for example, as shown in FIG. 1(b).
Q ~ 1.00 μm, and the solder pan 11' located approximately in the center on the other long side is slightly larger than this, with a diameter D' = 130~145 μm and a height H, as shown in Figure 1(c).
'=100 to 120 μm. Since the solder bump is spherical, the diameter and height cannot be controlled independently, but as described above, the height and major axis of the solder bump 1 on the short side and the solder pan 11' approximately in the center on the long side can be changed. By changing the bottom area of the solder bump, the
This can be easily achieved with a change of 0%. In the above embodiment, the bottom diameters of the solder bump 1 on the short side and the solder bump 1 approximately in the center on the long side are approximately 80 μm and 1°0 to 12°, respectively.
It is 08m.

〔Effect of the invention〕

The flip-chip device of the present invention has a temperature of 2°O to 40° when mounted.
When applying a load of 0gr, the solder bump collapses as follows.
The solder pan 11' located approximately at the center on the long side and the solder bump 1 on the short side are approximately the same. Therefore, even if it is reflowed, it can be stably connected to the substrate, so that the manufacturing yield can be improved and the manufacturing cost can be reduced. Also, in reliability tests such as temperature cycle tests, it was confirmed that the structure had a lifespan more than 10 times that of conventional structures, and that reliability could be improved.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are a plan view of a flip-chip device and a sectional structural view of its solder bumps, respectively, showing an embodiment of the present invention, and FIGS. 2 and 3 are a conventional one, respectively. A top view of the flip-chip device of FIG. 4 (
Figures a) to (c) are normal process diagrams for mounting a flip chip device on a board, and Figures 5 (a) to (b) are diagrams for mounting a flip chip on a board with a solder bump formed approximately in the center of the long side. FIG. 2 is a diagram illustrating problems that occur when DESCRIPTION OF SYMBOLS 10...Flip chip element, 1...Solder bump on the short side, 1'...Solder bump formed approximately in the center of the long side, 2...Collet, 3...Substrate, 4・・・
・Electrode on the board, X... gap.

Claims (1)

[Claims] A flip chip comprising: solder bumps arranged in a concentrated manner on a short side; and a solder bump formed at a substantially central position on the long side so as to have a higher shape than the solder bumps on the short side. element.