JP2560456B2 - Semiconductor chip mounting structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mounting structure of a semiconductor chip on a circuit board, and is particularly suitable for mounting a chip such as a semiconductor optical sensor or a semiconductor X-ray sensor. Regarding the structure.

<Prior Art> Generally, as a method of mounting a semiconductor chip such as an IC chip on a circuit board, a method of accommodating and mounting the chip in a package and a method of directly mounting the chip directly on the circuit board without using the package There is a method of mounting on the chip, but the bare chip mounting is more advantageous from the viewpoint of higher packing density.

Conventional bare chip mounting methods include wire bonding and TAB (tape automated bonding).
Method, flip chip bonding method, etc., and the flip chip bonding method is particularly suitable for high-density mounting.

<Problems to be Solved by the Invention> By the way, even in the flip-chip bonding method capable of the highest density mounting, for example, two IC chips are mounted on a substrate and these chips are electrically connected to each other. If necessary, it is necessary to provide wiring for the connection on the substrate, and there is a limit to shortening the wiring distance. For example, as shown in FIG. 4, two IC chips 41 and 42 are mounted on a substrate 43 by a flip chip bonding method, and an electrode 41a of the IC chip 41 and an electrode 32a of the IC chip 42 are connected to each other. In this case, the wiring distance on the substrate 43 is at least L.

When this wiring distance becomes long, the wiring capacitance and resistance increase, the crosstalk increases, the load driving capability of the element decreases,
This causes various problems such as deterioration of processing speed, signal attenuation, and increase of noise, which becomes a problem.

In order to solve such a problem, the present applicant has already proposed the fifth
We have proposed a mounting structure as shown in the figure (Japanese Patent Application No. 62-11).
6427). That is, the two semiconductor chips 51 and 52 are made to face each other with their electrode forming surfaces facing each other, and the corresponding electrodes (51a and 52a).
b, 51b and 52c, 51c and 52d) are directly connected by soldering, and a hole 53c is formed in the substrate 53 and one semiconductor chip 51 is accommodated in the hole 53c, and the other semiconductor chip
In this structure, the remaining electrodes 52a and 52e of 52 are directly connected to the pads on the substrate 53 by soldering.

With this structure, each electrode between the chips 51 and 52 is connected to the substrate 53.
Since they are directly connected to each other without passing through the upper wiring, the wiring distance between the chips is minimized, and one chip 51 is fitted into the hole 53c of the substrate 53 and the other is placed on the other. Since the chips 52 are mounted, the conventional flip chip bonding method is also advantageous in terms of mounting density.

However, when such a structure is applied to, for example, a semiconductor photodetector, the chip 51 in FIG. 5 is used as a sensor chip and the chip 52 is used as its IC amplifier.
The light incident on both sides of the sensor chip 51 cannot be detected, and a large area sensor cannot be formed by combining a large number of such structures. That is, 1
Only as many detectors as the number of elements that can be formed on each sensor chip 51 can be made.

Furthermore, a Si chip is usually used as the IC amplifier chip 52, and its thermal conductivity is poor. Meanwhile, the sensor chip
Various single semiconductors or compound semiconductors are frequently used as 51, and they are extremely sensitive to temperature, and the structure shown in FIG.

The present invention has been made in view of the above circumstances, and has a minimum wiring distance between two chips, and further, a photodetector or an X-ray detector.
It is an object of the present invention to provide a mounting structure capable of increasing the area of the detection surface and easily taking heat dissipation measures when applied to a line detector.

<Means for Solving the Problems> A structure for achieving the above object will be described with reference to FIG. 1 corresponding to an embodiment. According to the present invention, the circuit board 3 is formed on a surface near one end surface thereof. Pads 3a, 3b, 3c, 3d
, A part of the electrode group 1e, 1f, 1g, 1h formed on one surface of the first semiconductor chip 1 is directly electrically and mechanically connected, and the remaining part of the first semiconductor chip 1 is Electrode 1a, 1
b, 1c, 1d project outwardly from the one end surface of the circuit board 3, and the remaining electrodes 1a, 1b, 1c, 1d have electrodes 2a, 2b, 2d formed on the second semiconductor chip 2, Characterized by direct electrical and mechanical connections between 2c and 2d.

Note that in this specification, being directly electrically and mechanically connected means being electrically connected by the connection and being mechanically fixed to each other, for example, electrodes to be connected. It means that the spaces are directly fixed by soldering or conductive adhesive.

<Operation> Between corresponding electrodes 1a of the first and second semiconductor chips 1 and 2
, 2a, 1b and 2b, ... Are directly connected to each other without passing through the wiring on the substrate 3 and the wiring distance between chips is minimized. Further, since the second semiconductor chip 2 is arranged on the side of the end surface of the circuit board 3, the degree of freedom of the arrangement position between the members 1, 2 and 3 is increased, for example, as shown in FIG. If necessary, the cooling pipe 10 or the like may be provided to control the temperature, or as shown in FIG. 3, it is easy to apply such as increasing the area of the detection surface by combining the layers.

<Embodiment> FIG. 1 is a side view of an embodiment of the present invention.

In this example, the second semiconductor chip 2 is a minute semiconductor sensor chip in which 4 × 4 16 pixels are formed at a pitch of 0.4 mm. The first semiconductor chip 1 is an IC chip for performing signal processing of the output of the sensor chip 2, and has transistors and the like integrated to form an amplifier and the like.
It is a Si chip. Further, the circuit board 3 is for connecting the first semiconductor chip 1 to an external circuit, or for performing further signal processing such as A-D conversion of the detection signal output via the first semiconductor chip 1. This is a board on which chips and ICs are mounted. The substrate itself may be a Si wafer on which transistors and the like are formed.

Now, in the first semiconductor chip 1, electrodes 1a to 1d for connecting to the second semiconductor chip 2 and electrodes 1e to 1h for connecting to the circuit board 3 are provided on both sides on the same surface, respectively. It is formed collectively. The electrodes 1a, 1b, 1c and 1d have electrodes 2a, 2 formed on the second semiconductor chip 2, respectively.
b, 2c and 2d are each interconnected directly by solder S ... S. In addition, the electrodes 1e, 1f, 1g and 1h,
Similarly, to the pads 3a, 3b, 3c and 3d formed on the surface close to one end surface of the circuit board 3, the solder S ...
Connected by S. As a result, the second semiconductor chip 2 is connected to the circuit board 3 via the first semiconductor chip 1.
Will be supported laterally.

The above structure can be manufactured by the following procedure.

First, after forming solder bumps on the electrodes 1a to 1h of the first semiconductor chip 1, respectively, the electrodes 2a to 2d of the second semiconductor chip 2 and the pads of the circuit board 3 are respectively formed.
It is positioned so that 3a to 3d come into contact with each other, and the solder is reflowed to be melted and solidified.

Alternatively, bumps of high melting point solder on the electrodes 1a to 1d,
Low-melting-point solder bumps are formed on the electrodes 1e to 1h, and the electrodes 2a to 2d of the second semiconductor chip 2 are first connected to the electrodes 1a to 1h.
1d to 1d and connected by high temperature reflow, and then each pad 3a to 3d of the circuit board 3 may be positioned to electrodes 1e to 1h and connected by low temperature reflow.

If each chip is lightweight, a conductive adhesive may be used instead of the solder S ... S.

According to the present invention having the above basic structure, the following applications are possible.

In the example shown in FIG. 2, just above the first semiconductor chip 1,
A cooling pipe 4 having a diameter of about 1 mm extending along the second semiconductor chip 2 and the circuit board 3 is arranged and bonded with an adhesive 5 having good thermal conductivity. By passing a coolant such as water through the cooling pipe 4, the first semiconductor chip 1 on which the Si integrated circuit serving as a heat source is formed is effectively cooled, and the influence of temperature on the semiconductor sensor chip 2 is reduced. You can

In the example shown in FIG. 3, a plurality of sets having the structure shown in FIG. 1 are stacked in a stepwise manner so that the light receiving surfaces of the plurality of sensor chips 2 ... The surface sensor device having a large area can be obtained. In this example, if a film-shaped flexible printed circuit board is used as each circuit board 3, ..., The laminated thickness becomes thin, and the sensor chips 2 ,.

<Effects of the Invention> As described above, according to the present invention, the electrodes of two semiconductor chips are directly connected by solder or a conductive adhesive, and the remaining electrodes of one semiconductor chip are connected to a circuit. Since it was directly connected to a pad formed on the surface near one end surface of the board with solder or a conductive adhesive, the wiring distance between two chips was minimized, there was almost no wiring capacitance, and performance was improved and High-density mounting becomes possible as compared with conventional mounting.

Moreover, since the semiconductor chip is arranged on the side of one end surface of the circuit board, the sensor area can be increased by combining a large number of sensors and the temperature can be controlled by arranging the cooling pipe when applied to a semiconductor sensor or the like. This facilitates the function and performance of the sensor.

In addition, solder bumps are not formed on the sensor chip (second semiconductor chip), and the Si chip (first semiconductor chip) is not formed.
Since the solder bumps can be formed only on the side to be interconnected, when the sensor chip is a compound semiconductor, there is no risk of contamination due to the bump formation. That is, the compound semiconductor may react with the plating solution and cause performance deterioration during immersion in the plating bath during the process for forming solder bumps, but this process can be omitted.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention, FIGS. 2 and 3 are side views showing their application examples, and FIG. 4 is a mutual view of two semiconductor chips mounted by a conventional flip chip bonding method. FIG. 5 is an explanatory diagram of connection, and FIG. 5 is an explanatory diagram of a mounting structure proposed in Japanese Patent Application No. 62-116427. 1 ... First semiconductor chip 1a-1h ... Electrode 2 ... Second semiconductor chip 2a-2d ... Electrode 3 ... Circuit board 3a-3d ... Pad S ... S ... Solder

Claims (1)

(57) [Claims] 1. A part of an electrode group formed on one surface of a first semiconductor chip is directly electrically and mechanically connected to a pad formed on a surface near one end surface of a circuit board, and The remaining electrodes of the first semiconductor chip project outward from the one end surface with respect to the circuit board, and the electrodes formed on the second semiconductor chip are directly electrically and mechanically attached to the remaining electrodes. The semiconductor chip mounting structure connected to the.