JPH0543485Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a structure for mounting a flip chip provided with bumps for connection with an external circuit on a wiring board.

[Conventional technology]

With the advancement of semiconductor devices such as integrated circuits, the number of circuit elements housed in one semiconductor device has rapidly increased, and when mounting them on a wiring board, the work of connecting a large number of bonding wires has become complicated. At the same time, it has become necessary to allocate a considerable amount of area around the semiconductor device for connection lines. On the other hand, in order to miniaturize electronic devices, it is first necessary to miniaturize the wiring board, and it is necessary to increase the packaging density of semiconductor devices as much as possible. As is well known, flip chips are equipped with protruding conductors called bumps for connection with external circuits, and when mounting a flip chip, these bumps can be directly bonded to the conductors of the wiring board, so bonding is not necessary. Connection with an external circuit is possible within the area required for mounting the semiconductor device on the wiring board, without the need for wires and providing an area around the semiconductor device for connection. FIGS. 2 to 4 show the implementation of this flip chip according to the prior art.

A flip chip is an integrated circuit, for example, and is usually a rectangular plate-like body, as shown in FIG.
On one side, in the figure, on the bottom side, there are about a dozen bumps made of solder or gold. The bumps are arranged along two opposite sides of the flip chip's rectangle, or along four sides as shown.
FIG. 3 shows a state in which this flip chip 1 is mounted on a ceramic wiring board 10. In this case, solder is usually used for the bumps, and the flip chip is connected to the conductor 11 on the surface of the wiring board 10 and the solder bumps 2.
a, thereby connecting the flip chip to the plurality of conductors 11 and attaching it to the wiring board 10 by the solder connection. If the wiring board is a so-called printed wiring board that uses an ordinary glass epoxy board, it is impossible to directly mount the flip chip on the printed wiring board because the thermal expansion coefficients of the wiring board and the silicon that make up the flip chip are quite different. The flip chip must be mounted on a ceramic wiring board and then mounted on a printed wiring board. However, this requires connecting the conductor on the ceramic wiring board and the conductor on the printed wiring board with a bonding wire.
Mounting takes time and the mounting density decreases. For this reason, a mounting structure using a type of intermediary connection conductor as shown in FIG. 4 is known. This intermediate connection conductor 21 is made up of a large number of thin copper foil strips with a thickness of several tens of μm supported on an insulating film 22 made of flexible polyimide, etc., and one end of each intermediate connection conductor is connected to a bump of the flip chip 1. The end is connected to the conductor 11 of the printed wiring board 10 by soldering or the like. In this case, gold bumps 2b are usually used as the bumps, and they are heated at 450°C using a thinly tinned intermediary connection conductor 21 and a special tool.
They are joined under moderate heat and pressure. Since both the intermediary connection conductor 21 and the insulating film 22 are flexible and absorb the thermal stress that is likely to be applied to the flip chip 1, the flip chip can be mounted on an ordinary printed wiring board with the mounting structure shown in FIG. Compared to mounting via a board, connection requires less effort and the area required for mounting can be reduced.

[Problem that the invention attempts to solve]

However, as the degree of integration of semiconductor devices increases and it becomes possible to integrate complex or large numbers of circuits into a small area, the number of bumps required for connection with external circuits increases, making it difficult to arrange them all around the periphery of a flip chip. It's getting old. Of course, it is possible to reduce the size of the bumps themselves or reduce the spacing between them, but if the bumps become too small, the reliability of the connection will decrease, and if the bump spacing is made small, the conductor on the wiring board side or the intermediary connection conductor Since the spacing between the wires must be reduced accordingly, there is a lower limit to this, and there is a risk that the wires may be short-circuited during connection work. As described above, there are inherent limits to the size of bumps and their mutual spacing, so even if circuits can be highly integrated within a flip chip, the size of the flip chip must be made extra large in order to arrange the bumps around the periphery. Of course, this situation is similar when connecting by bonding wires, since the connecting pads must be arranged around the periphery of the chip.

The object of the present invention is to alleviate such difficulties and provide a flip chip mounting structure that can rationally configure flip chips and improve the mounting density on a wiring board.

[Means for solving problems]

According to the present invention, the above-mentioned object is to connect the bump electrodes to a conductor of a wiring board with the other surfaces of two plate-like flip chips each having a plurality of bump electrodes on one surface being adhered or bonded to each other; This is achieved by supporting the flip chip by the wiring board via the connection.

[Effect]

In the present invention, two flip chips, each having a bump electrode on one side, are used by bonding them back to back by bonding or soldering. At this time, the flip chips that are connected to each other may be integrated with different circuits, or
It may also be one integrated circuit divided into two flip chips. In the latter case, if the integrated circuit is a combination of a plurality of circuits of the same type, it can be easily divided into two flip chips. Furthermore, even if an integrated circuit is a series of circuits, it is often a collection of circuits each with a different function.
Usually, it is possible to divide the flip chip into two flip chips according to function. Due to such division, the apparent chip area of the semiconductor device is approximately halved, and if the size is originally increased to arrange bumps on the periphery, it will be less than halved.

The bump groups distributed on two sides in this way can be connected directly to the conductor of the wiring board as in the past due to the hassle of each, or they can be connected to the conductor of the wiring board via the aforementioned intermediary connection conductor, but someday In any case, since the connection with the conductor of the wiring board is made at a different location for the bump groups on both sides, the size of each connection point and the mutual spacing between them can be the same as before. It is possible to double the number of bumps per flip chip for the same area without shrinking it unnecessarily, and even when the area is halved as mentioned above, the number of bumps can be increased compared to the conventional one.
Approximately 40% can be achieved. In any case, since the number of bumps on the flip chip can be increased, the packaging density can be increased accordingly, and the above-mentioned problem can be solved.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows three embodiments of a flip-chip mounting structure according to the present invention, in which the same parts as in the previous figures relating to the prior art are given the same reference numerals.

Figure a shows a flip chip 1 with bumps 2 on both sides used in the present invention, and as described above, this flip chip consists of two flip chips 1a and 1b each having bumps on one side, which are bonded or bonded back to back. It is configured as follows. Figure b shows an embodiment in which this flip chip 1 is mounted on a ceramic wiring board 10. In this embodiment, the bumps on the lower surface of the flip chip 1 in the figure are solder bumps 2a, and the bumps on the upper surface of the flip chip 1 are solder bumps 2a. Gold bumps 2b are used for this. In mounting this flip chip 1, the gold bump 2b is first bonded to one end of the intermediate connection conductor 21 at a high temperature of about 450°C. The solder bumps 2a are then joined to the conductor 12 in the center of the wiring board by soldering. This bonding temperature varies depending on the solder used for the solder bump 2a, but if high temperature solder is used, for example
330°C, for example 230°C for relatively low-temperature soldering, and the joining process itself can be done in the same way as in the past. Then, the other end of the intermediate connection conductor 21 is joined to the conductors 11 on both the left and right sides of the wiring board 10 in the same manner as in the prior art, for example, by soldering. This completes the work of attaching the flip chip 1 to the wiring board 10 and connecting its bumps, but if vibration resistance or impact resistance is required, use an elastic protective A resin 30 is applied so as to cover the mounting portion and then hardened. Silicone rubber is most suitable for this resin 30, and it is convenient to select a room temperature curing type or an ultraviolet curing type as required.

Figure c shows an embodiment in which the flip chip 1 is mounted on an ordinary printed wiring board 10. In this case, the bumps are gold bumps 2b on both sides.
is used, and is connected to the conductor 11 of the wiring board via the intermediate connection conductor 21. Further, the printed wiring board in this embodiment is of a double-sided type with conductors 11 on both sides, and a window 10a is opened in which the flip chip 1 is housed as shown. For mounting, the gold bumps 2b and one end of the intermediary connection conductor 21 are first bonded under high temperature as in the previous embodiment, but this bonding work is performed on the gold bumps 2b on both sides of the flip chip 1. Can be done at the same time. Then the intermediary connection conductor 2
1 and the conductor 11 of the wiring board 10 by, for example, soldering, simultaneously to the conductor 11 on both sides of the wiring board 10 using a special tool. Subsequently, resin 30 is applied or injected in the same manner as in the previous embodiment so as to cover the entire mounting and is cured. As a result, the flexible intermediate connection conductor 21 is confined together with the flip chip 1 within the resin 30, the intermediate connection conductor is protected from vibrations and shocks, and the flip chip is supported on the wiring board 10 via the resin 30.

Figure c is a little special, but flip chip 1
An embodiment will be shown in which the circuit board is mounted between two ceramic wiring boards 10, 10. In this case, solder bumps 2a are used as bumps, and both ceramic wiring boards 10, 10 are both double-sided and can be positioned relative to each other by guide pins 40 inserted into guide holes 10b. Further, the spacer 41 allows the mutual spacing to be maintained. For mounting, first, for example, the flip chip 1 is temporarily attached to the wiring board 10 at the bottom of the figure using an appropriate means such as solder paste, and then another wiring board 10 is attached to it using guide pins 40 and spacers 41. The solder bumps 2a may be melted by heating and bonded to the conductors 11 of the wiring board. It is possible to stack a number of ceramic wiring boards 10 with a similar structure and mount the flip chip 1 between them.

As can be seen from the above examples, flip chips having bumps on both sides can be mounted on or between wiring boards with variously modified structures.

[Effect of idea]

As can be seen from the above explanation, according to the mounting structure of the present invention, the bump electrodes are attached to the wiring board with the other surfaces of two plate-like flip chips each having a plurality of pump electrodes on one side bonded or bonded to each other. Since the flip chip is connected to the conductor and the flip chip is supported by the wiring board via the connection,
By taking advantage of the inherent advantages that a mounting structure using bumps has over a mounting structure using bonding lines, it is possible to significantly improve the mounting density of semiconductor devices on a wiring board compared to the conventional method. In addition, when a flip chip with double-sided bumps is constructed by dividing an integrated circuit flip chip, which is originally one, into two pieces and gluing or joining them back to back, it is necessary to make sure that the bump dimensions and mutual spacing are consistent. This also makes it easier to arrange conductors on the wiring board. The present invention is particularly suitable for mounting integrated circuits with a large number of external connection points, and by rationalizing the arrangement of bumps as described above, the circuit arrangement within the chip can also be rationalized.

[Brief explanation of the drawing]

FIG. 1 is a perspective view and a cross-sectional view showing a flip chip used in a mounting structure according to the present invention and some mounting examples thereof. Figure 2 and subsequent figures relate to the prior art, in which Figure 2 is a perspective view of a conventional flip chip, and Figures 3 and 4 are cross-sectional views showing how to mount the flip chip on a ceramic wiring board and a printed wiring board, respectively. . In the figure, 1...flip chip, 1a, 1
b...Half of the flip chip, 2...Bump, 2
a...Solder bump, 2b...Gold bump, 10...
Wiring board, 10a...Window in wiring board, 10b...
...Window inner hole, 11, 12...Conductor of wiring board, 21
...Intermediary connection conductor, 22...Insulating film, 30
. . . resin, 40 . . . guide pin, 41 . . . spacer.

Claims (1)

[Scope of utility model registration request] The other surfaces of two plate-like flip chips each having a plurality of pump electrodes on one surface are bonded or joined together, and the bump electrodes are connected to a conductor of a wiring board, and the flip chip is connected to the conductor of the wiring board through the connection. A flip chip mounting structure characterized by being supported by a wiring board.