JP2654035B2 - Semiconductor IC device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thin semiconductor IC device used by being incorporated in an IC card or the like.

[Background Art] Conventionally, DIP (Dual Inline Packa) has been used as a semiconductor IC device.
ge) and SOP (Small Outline Packlage). These are formed, for example, by mounting the IC chip 1 on the leads 3, 3... Of the lead frame and enclosing the IC chip 1 together with the lead 3 in a molding resin 4 as shown in FIGS. 3 (a) and 3 (b). I have. However, in these devices, the connection between the IC chip 1 and each of the leads 3 is performed by bonding a wire 22 such as a gold wire.
Has to be formed with a certain thickness or more, and there is a problem in that there is a limit in reducing the thickness of the semiconductor IC device. Further, since these semiconductor IC devices are formed by encapsulating the IC chip 1 in the molding resin 4, it is easy for the IC chip 1 to stay inside the heat generated by the IC chip 1, and as shown in FIG. body
24 is buried with its surface exposed, and the radiator 24
The heat of the IC chip 1 is dissipated. However, in this case, the heat radiator 24 must be inserted into the molding resin 4, so that the number of manufacturing steps increases, and
There has been a problem that the semiconductor IC device cannot be made thinner due to the heat radiator 24.

[Object of the Invention] The present invention has been made in view of the above points, and it is possible to easily reduce the thickness and enhance the heat dissipation of the IC chip. It is an object of the present invention to provide a semiconductor IC device having excellent conduction reliability.

[Disclosure of the Invention] Thus, in the semiconductor IC device according to the present invention, a plurality of leads 3, 3... Of the metal lead frame 2 having a linear expansion coefficient of 3 × 10 ⁻⁶ / ° C. to 1.8 × 10 ⁻⁵ / ° C. Each of the chip mounting pieces 5 is formed, an IC chip 1 formed of a silicon wafer is mounted on one surface of the chip mounting piece 5 and directly mounted, and the IC chip 1 is enclosed in a molding resin 4 together with the leads 3. The present invention is characterized in that the other surface of the other side of the chip mounting piece 5 is exposed on the surface of the molding resin 4, and the present invention will be described in detail below with reference to examples.

Lead frame 2 is 42 alloy (Ni42% Ni-Fe alloy)
The left and right frames 17 are connected by connecting pieces 18 to form a long strip, as shown in FIG.
The portion between the adjacent connecting pieces 18, 18 is one unit for producing a semiconductor IC device, and a plurality of pieces from the frames 17, 17 are provided at the portions between the adjacent connecting pieces 18, 18, respectively. Lead 3,3 ... is extended. The tip of each lead 3 is formed as a bent portion 19 and a wide chip mounting piece 5. In FIG. 2, reference numeral 23 denotes a feed hole formed in the frame 17 for automatically feeding the lead frame 2.

A semiconductor IC device is manufactured using the lead frame 2. First, the IC chip 1 is mounted. The IC chip 1 is mounted by directly mounting the IC chip 1 directly on the upper surface of each chip mounting piece 5, 5,... As shown by a chain line in FIG. This direct mounting can be performed, for example, by flip chip mounting. That is, bumps 20 such as solder are applied to the electrodes of the IC chip 1.
Is formed, and the bump 20 and the chip mounting piece are joined by soldering. By thus directly mounting, the fixing of the IC chip 1 to the leads 3 and the electrical connection can be performed simultaneously. After the IC chip 1 is mounted in this manner, the IC chip 1 is formed, and the IC chip 1 is embedded in the molding resin 4 together with the leads 3, 3,. This molding can be performed by continuously feeding the long lead frame 2 to a transfer molding device, a compression molding device, or the like. The resin used for this molding is not particularly limited, but a thermosetting resin such as phenol, epoxy, silicon, and polyimide, and a thermoplastic resin such as polyphenylene sulfide, polysulfone, polyether sulfone, and polyaryl sulfone are used. be able to. When sealing the IC chip 1 and the leads 3, 3... In the molding resin 4 by molding in this manner, the lower surface of the chip mounting piece 5 is formed as shown in FIG. From the surface of the chip mounting piece 5 to the external connection terminals 6.
Is formed. By separating the leads 3, 3,... From the frame 17, the semiconductor IC device A formed as shown in FIG.

In the semiconductor IC device A thus formed, since the IC chip 1 is connected to the leads 3 of the lead frame 2, the printed circuit board 11 is used as a substrate as in the conventional example of FIG. There is no need to perform hole processing or circuit processing, and since the IC chip 1 is mounted directly on the chip mounting piece 5, fixing and electrical connection can be performed simultaneously, and wire bonding and the like can be performed. Therefore, the number of processing steps in manufacturing can be reduced. In addition, since the substrate can be formed by the molding resin 4 molded,
It can be formed with greater thickness and dimensional accuracy than when the substrate is formed from a printed wiring board 11 obtained by lamination molding, and is suitable as a package that requires thinness, such as when incorporating it into an IC card, and also as an IC chip. Since the wire 1 is directly mounted on the chip mounting piece 5 without wires, it is necessary to set the thickness of the molding resin 4 to a certain value or more in order to store the wire 22 in the molding resin 4 as in the conventional example of wire bonding. However, the overall thickness of the semiconductor IC device A can be made thinner. Therefore, the thickness of the semiconductor IC device A can be set to 1 mm or less, desirably 0.7 mm or less, and formed so that it can be incorporated into an IC card.

When the semiconductor IC device A thus formed is used for an IC card, the semiconductor IC device A is formed with the terminals 6 formed on the exposed surfaces of the chip mounting pieces 5 of the leads 3 exposed from the surface of the IC card. Can be embedded and integrated into an IC card. Here, the IC chip 1 is mounted in direct contact with the chip mounting piece 5 exposed as the terminal 6, and the heat generated by the IC chip 1 can be efficiently radiated to the outside from this portion. It is possible to prevent the resin from remaining in the molding resin 4. Especially the second
By widely forming the chip mounting pieces 5 as in the embodiment shown in the figure, heat radiation can be improved. As described above, heat can be dissipated without using the heat radiator 24 as in the conventional example. Therefore, the man-hour for embedding the heat radiator 24 in the molding resin 4 is not required, and the semiconductor IC device A Does not increase in thickness. Incidentally, in the embodiment shown in FIG.
3a also protrudes from the molding resin 4, but the semiconductor IC device A
The end 3a of the lead 3 protruding can be used as a positioning when assembling the IC in an IC card or the like, or can be used as a ground terminal for releasing static electricity or as a heat radiation terminal for releasing heat. .

In the present invention, the metal material forming the lead frame 2 has a linear expansion coefficient of 3 × 10 ^{−6 /} ° C. to 1.8 ×.
10 ^-5 / ° C, preferably with a coefficient of linear expansion of 4 × 10 ^-6 / ° C
9 × 10 ⁻⁶ / ° C. is used. As the IC chip 1, a chip formed of a silicon wafer is used. If the linear expansion coefficient of the lead frame 2 is significantly different from the linear expansion coefficient of the silicon wafer of 3 to 4 × 10 ⁻⁶ / ° C., the temperature change is caused. The difference in the expansion dimension may cause a displacement at the joint between the chip mounting piece 5 of the lead 3 of the lead frame 2 and the IC chip 1, which may cause a problem in the reliability of conduction between the IC chip 1 and the lead 3. And lead frame 2
Used have a coefficient of linear expansion of 1.8 × 10 ⁻⁵ / ° C. or less. For the linear expansion coefficient as the metal that can be used in the lead frame 2 do not see smaller than 3 × 10 ^-6 / ℃, the lower limit of the coefficient of thermal expansion of the lead frame 2 is virtually 3 × 10 ^-6 / ℃ Will be set.

Here, the effect of the linear expansion coefficient of the lead frame 2 will be illustrated by a test.

Using a lead frame made of the material shown in the following table, a silicon wafer evaluation chip with 2.3 × 3.2 mm and 0.2 mm thick comb-shaped Al wiring formed on the lead of this lead frame was flip-chip mounted with solder bumps. Then, epoxy resin sealing molding was performed by a transfer molding apparatus. The package prepared in this manner was subjected to a thermal shock test in which the operation of cooling to -65 ° C and then heating to 150 ° C was repeated as one cycle, and each cycle was inspected for the occurrence of disconnection failure. The test was performed on 10 samples, and the number of thermal shock cycles when 5 samples were disconnected was shown in the following table as a result.

As can be seen from the table, the coefficient of linear expansion of test 5 was 2.3 × 10
^{When the} lead frame is made of ^-5 / ° C aluminum, the thermal shock test results are poor, but the coefficient of linear expansion is in the range of 3 × 10 ^-6 / ° C to 1.8 × 10 ^-5 / ° C It is confirmed that the results of the tests 1 to 4 obtained can obtain good results of the thermal shock test. All of the disconnection failures were caused by the separation between the lead and the solder bump of the chip.

[Effect of the Invention] As described above, according to the present invention, an IC chip is mounted on one surface of a chip mounting piece at one end of each of a plurality of leads of a metal lead frame, and the IC chip is directly mounted. The IC chip can be directly mounted on the chip mounting piece without wires because it is enclosed in the molding resin together with the leads. It is not necessary that the semiconductor IC device be contained in the molding resin, and the overall thickness of the semiconductor IC device can be reduced. In addition, since the IC chip is mounted in direct contact with the chip mounting piece exposed from the molding resin, heat generated by the IC chip can be efficiently radiated to the outside from this part. The heat radiation can be ensured without necessity. Further, since the linear expansion coefficient of the lead frame is formed by 3 × 10 ^-6 /℃~1.8×10 ^-5 / ℃ metal coefficient of linear expansion of the silicon wafer of 3~4 × 10 ^-6 / ℃ It is possible to approximate the linear expansion coefficient of the lead frame to the IC chip and prevent the bonding between the IC chip and the chip mounting piece of the lead from coming off due to the difference in thermal expansion, thereby reducing the conduction reliability. .

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a perspective view of a part of a lead frame used in the embodiment, and FIG.
(B) and (c) are cross-sectional views of a conventional example. 1 is an IC chip, 2 is a lead frame, 3 is a lead, 4 is a molding resin, and 5 is a chip mounting piece.

Claims (1)

(57) [Claims] (1) a coefficient of linear expansion of 3 × 10 ⁻⁶ / ° C. to 1.8 × 10 ⁻⁵ / ° C.
A chip mounting piece is formed on each of a plurality of leads of the metal lead frame, and an IC chip formed of a silicon wafer is mounted directly on one surface of the chip mounting piece, and the IC chip is molded together with the lead. A semiconductor IC device characterized by being enclosed in a package and exposing the other surface of the chip mounting piece to the surface of the molding resin.