JPH0358537B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a flip chip mounting structure in which a flip chip having bumps (protruding electrodes) on its entire surface is connected to a circuit board via a tape carrier film.

<Prior art> Flip chips, which can be mounted using bumps formed on the active region, are devices with a high degree of freedom in design because the electrodes (bumps) can be taken out from any position. It is extremely advantageous for multi-terminal connections because it can be formed easily, and unlike wire bonding, it does not require a dedicated connection area on the chip surface, making it possible to reduce the size and cost of the chip. Furthermore, since the connection inductance of the wiring within the chip and the electrodes is small, it has various features such as being extremely suitable for mounting high-speed devices.
However, as shown in FIG. 4, this flip chip is attached by directly soldering the bumps 2 formed on the surface of the chip 1 to the terminal electrodes 4, 4' of the circuit board 3 of the package.
Due to the heat generated by the chip 1 and changes in ambient temperature, distortion occurs due to the difference in thermal expansion between the chip 1 and the circuit board 3, and the connection between the bumps 2 and the terminal electrodes 4' on the periphery of the chip 1 is particularly damaged. I have an easy problem to solve.

Therefore, the circuit board 3 is made of materials such as silicon carbide ceramics and aluminum nitride ceramics, which have a coefficient of thermal expansion close to that of silicon, which is the material of the chip 1, so that there is no difference in thermal expansion between the two. Although mounting structures have been devised, they have not been widely put into practical use due to high costs and problems with electrical characteristics. As a mounting method to solve the above problem, the flip chip 1 is not directly mounted on the circuit board 3, but is first bonded and connected to a tape carrier film made of a flexible film, and then mounted on the circuit board 3 via the tape carrier film. There is area TAB technology (area tape automated bonding technology) that is implemented on top.

The area TAB technique will be explained based on FIGS. 5 to 7. As shown in FIG. 5, pads 6 are provided on the tape carrier film 5, and are designed in advance to correspond to the arrangement of the bumps 2 on the flip chip 1. The bump 2 is connected to the pad 6 of the tape carrier film 5 by bonding. Thereafter, as shown in FIG. 6, the board connection leads 8, which are arranged radially from each pad 6 across the square-shaped cutting holes 7, are cut along the cutting holes 7. , the flip chip 1 to which this tape carrier film 5 is attached
However, as shown in FIG. 7, each board connection lead 8
It can be attached by connecting it to the terminal electrode 4 of the circuit board 3. In this mounting method, since the flexible tape carrier film 5 is interposed between the flip chip 1 and the circuit board 3, distortion due to the difference in thermal expansion between the chip 1 and the circuit board 3 is absorbed by the flexible tape carrier film 5. High reliability can be obtained, and since a tape carrier method is used, high mass productivity can be obtained.

<Problems to be Solved by the Invention> However, although the above-mentioned mounting structure exhibits a remarkable effect, the electric signal of the flip chip 1 is first transferred from the bump 2 to the bump on the film 5 by wiring on the tape carrier film 5. Pull it out to the board connection lead 8 around the connection pad 6,
It is necessary to transmit the signal to the circuit provided on the circuit board 3 via this lead 8. For example, when a large number of bumps 2 are arranged in a matrix over the entire surface like the flip chip 1 shown in FIG. It becomes impossible to take out the terminal, and there is a limit to the possibility of increasing the number of terminals.

More specifically, as shown in FIG. 8, a board connection lead 8' is provided on the other side of the tape carrier film 5, and the pad 6 on one side is electrically connected to this lead 8' through a via hole 9. Even in the case of the connected double-sided wiring tape carrier film 5, as is clear from FIG. Since it is possible to extract the signals from only the pads 6 inside the flip chip 1, if there are a large number of pads 6, 6', it is not possible to extract the signal from the central pad 6'.

The present invention was made in view of the above-mentioned conventional problems and to solve the problems.
The object of the present invention is to provide a flip chip mounting structure in which all bumps can be connected to a circuit board with high reliability via a tape carrier film.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a flip chip mounting structure in which a flip chip is connected to a circuit board via a tape carrier film, in which the flip chip is connected to the tape carrier film. The board connection lead led out from the bump connection pad connected to the bump on the periphery of the bumps formed on the entire surface, and the opposite side corresponding to the bump connection pad connected to the bump in the center of the flip chip. A board connection pad is formed on the side surface and electrically formed on this pad through a via hole, and the bumps on the peripheral edge of the flip chip are connected to the bump connection pad of the tape carrier film and the board connection pad. The bump at the center of the flip chip is electrically connected to the terminal electrode of the circuit board through the lead for connection, and the bump at the center of the flip chip is connected to the terminal electrode of the circuit board through the bump connection pad, via hole, and board connection pad of the tape carrier film. The gist is that the structure is electrically connected to a terminal electrode.

<Function> With the above structure, the bumps in the center part of the flip chip, which had been difficult to connect to the circuit board in which bumps were formed over the entire surface, were connected in an electrically connected state on the tape carrier film. Since the flip chip is connected to the terminal electrodes of the circuit board through the bump connection pads, via holes and board connection pads, all the bumps on the flip chip can be connected to the terminal electrodes of the circuit board. In addition, the bump at the center of the flip chip is almost directly connected to the terminal electrode without using a lead, and the amount of distortion caused by the difference in thermal expansion between the flip chip and the circuit board is relatively small in this center. , there is no problem with reliability. On the other hand, the bumps on the periphery of the flip chip, which have a relatively large amount of distortion due to the difference in thermal expansion between the flip chip and the circuit board, are connected to terminal electrodes by flexible board connection leads via a flexible tape carrier film. , sufficient reliability can be obtained.

<Example> Hereinafter, one embodiment of the present invention will be explained in detail.

In FIG. 1, which shows a cut front view of an embodiment of the present invention, the same or equivalent parts as in FIG. 8 are given the same reference numerals. Then, board connection pads 10 are connected to the opposite surface of the tape carrier film 5 in correspondence with the bump connection pads 6' of the tape carrier film 5 to which the bumps 2 at the center of the flip chip 5 are connected. This differs from the one shown in FIG. 8 in that both pads 6' and 10 are electrically connected by a via hole 9, and terminal electrodes 4 are provided at positions corresponding to the board connection pads 10 on the circuit board 3, respectively. do.

And the flip chip 1 in the above embodiment
The bumps 2 are arranged in a matrix over the entire surface, and bump connection pads 6, 6' are arranged on one surface of the tape carrier film 5 in a corresponding arrangement. Further, the tape carrier film 5 used in the above embodiment is made of an insulating material such as polyimide/glass epoxy or polyester, and its thickness is preferably about 25 to 127 μm ⁺ . Further, the pads 6, 6', 10 and leads 8, 8' on the tape carrier film 5 are made of copper with a thickness of 10 to 35 μm ⁺ , and have a surface that improves weldability with solder. For this reason, it is plated with tin, gold, etc. Furthermore, the connections between the board connection leads 8, 8' of the tape carrier film 5 and the board connection pads 10 and the terminal electrodes 4 of the circuit board 3 are made using solder 11 having a lower melting point than the bumps 2.
This is done by attaching.

The bump connection pad 6 connected to the bump 2 on the peripheral edge of the flip chip 1 is connected to the board connection lead 8 on one side of the film 5 as shown in FIG. 2 and via hole 9 as shown in the third part. The board connection lead 8' on the other side of the film 5
It is connected to the terminal electrode 4 via. On the other hand, the bump connection pad 6' in the center, from which signals cannot be taken out via leads to the periphery of the flip chip 1, is connected directly to the via hole 9 and the film 5.
The circuit board 3 is connected via the board connection pad 10 on the bottom surface.
It is electrically connected to the terminal electrode 4 of.

With the above configuration, the flip chip 1
The highly reliable central pad 6', which has a relatively small amount of distortion due to the difference in thermal expansion between the pad 6 and the circuit board 3, is directly connected to the terminal electrode 4 of the circuit board 3 through the via hole 9 and the board connection pad 10. connected,
On the other hand, the bumps 2 on the periphery of the flip chip 1, which have a relatively large amount of distortion due to the difference in thermal expansion between the flip chip 1 and the circuit board 3, are made of flexible copper board connection leads 8 via a flexible tape carrier film 5. , 8' to the terminal electrode 4, sufficient reliability can be obtained.

<Effects of the Invention> As is clear from the above description, according to the flip chip mounting structure of the present invention, a flip chip in which bumps are formed in high density can be connected to a circuit board with high reliability, and a single device can be connected. Since multiple terminals can be taken out from the chip, there is an advantage that, for example, LSIs can be made smaller and have more pins.

[Brief explanation of drawings]

1 to 3 show an embodiment of the flip-chip mounting structure of the present invention, in which FIG. 1 is a cutaway front view, FIGS. 2 and 3 are a partially cutaway front view, and FIG. 4 is a partially cutaway front view. 1 is a front view showing a conventional mounting structure of a flip chip on a circuit board without using a tape carrier film, and FIGS. 5 to 7 are exploded perspective views, perspective views, and perspective views showing the process of attaching a tape carrier film to a flip chip. , FIG. 8, and FIG. 9 are a cutaway front view and a plan view, respectively, showing a conventional mounting structure. 1... flip chip, 2... bump, 3...
Circuit board, 4...Terminal electrode, 5...Tape carrier film, 6, 6'...Bump connection pad,
8, 8'... Lead for board connection, 9... Via hole, 10... Pad for board connection.

Claims (1)

[Claims] 1. In a flip chip mounting structure in which a flip chip is connected to a circuit board via a tape carrier film, the tape carrier film is provided with bump connection pads connected to the bumps on the periphery of the bumps formed on the entire surface of the flip chip. A board connection lead led out from the flip chip and a bump connection pad connected to the bump at the center of the flip chip are formed on the opposite surface thereof and are electrically connected to this pad via a via hole. a board connection pad is formed, and the bumps on the peripheral edge of the flip chip are electrically connected to the terminal electrodes of the circuit board via the bump connection pads of the tape carrier film and the board connection leads, A flip chip mounting structure characterized in that a bump at the center of the flip chip is electrically connected to a terminal electrode of the circuit board via a bump connection pad, a via hole, and a board connection pad of the tape carrier film.