JPH067259U - Semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a semiconductor device in which a multi-pin structure is miniaturized and thinned by improving the structure of the semiconductor device, and further, a rack is not generated during reflow. [Structure] In a lead frame in which a central die pad having an inorganic coating on the back surface is bent and the tip end portions of the die pad leads connected thereto are positioned in a descending position,
The inner lead is formed in a short size, and the inner lead and the T
While joining the outer leads of AB or FPC,
A gist of a semiconductor device is one in which an inner lead of a TAB or FPC having a hole in the central portion and an electrode of a semiconductor element fixed to the die pad are connected by a bonding wire, and the structure thus constructed is resin-molded. To do.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a semiconductor device using a composite lead frame having excellent mounting workability.

[0002]

[Prior art]

 Generally, a resin-sealed semiconductor device has a die pad 3 for mounting a semiconductor chip 2 in a central portion of a lead frame 1 as shown in a cross section in FIG. 5, and the semiconductor chip 2 is bonded with a bonding material 4 such as Ag paste. After die-bonding, the electrode pad 5 on the chip and the inner lead 1a of the lead frame 1 are joined by a bonding wire 6 such as an Au wire. It is stopped and produced. This semiconductor device is firmly bonded to the substrate 9 by the outer leads 1b of the lead frame 1, and at this time, the solder 8 applied to the outer leads 1b is subjected to heat irradiation or reflow treatment for melting by melting.

Generally, the sealing resin of a semiconductor device has a hygroscopic property, so that it absorbs moisture over time, and some of the moisture adheres to the constituent parts. Such water content mainly destroys the interface with the resin, and the water accumulated in the gap causes rapid vaporization and expansion due to reflow heating, and causes resin destruction 10. On the other hand, potentially at room temperature, it has been known that strain due to the difference in thermal expansion between the resin and component parts, especially the die pad, causes shear peeling at the interface, and this occurs during reflow heating. Water vapor generated in the separated gap promotes separation. In particular, peeling is large at the end of the die pad where stress concentration is likely to occur, and in combination with the action of vapor pressure, cracks 10 as shown in the figure occur.

As a result, the sealing performance of the semiconductor device is deteriorated and the reliability is impaired. Therefore, it is necessary to specially package the semiconductor device for moisture prevention at the time of shipment or to shorten the board mounting time. Countermeasures may be taken, such as making a request, or baking the hygroscopic product before mounting it on the board. However, these methods are extremely troublesome and need to be dealt with by the customer.

In recent years, with the high integration and high functionality of semiconductor devices, the number of leads in the leads is increasing more and more, and higher precision and fine pitch are required. Conventionally, lead frames that are connected to semiconductor chips using bonding wires have been limited in fine pitch due to the processing method and materials used. However, TAB (Tape Automated Bonding) tape and FPC (Flex Printed Curcuit) tape are available. Recently, it has been widely used as an effective technique for a large number of pins, and in particular, a composite lead frame integrally connected to a lead frame is gradually attracting attention due to the ease of work for mounting a PCB (Printed Curcuit Board). For example, as shown in FIG. 4, the outer lead 11b of the TAB tape 11 is joined to the inner lead 1a of the lead frame 1, and the electrode pad 5 of the semiconductor chip 2 and the inner lead 11a of the TAB tape 11 are joined to the device holes. There is known a semiconductor device in which a resin is sealed with a bonding wire 6 connected to each other. However, although a multi-pin structure can be formed by using a TAB tape, a semiconductor chip 2 with a drop and an inner lead 11a of the TAB are formed. There is a case where the bonding wire 6 is loosened or is deformed due to springback when connecting with each other or when the resin is sealed, and the edge 9 of the semiconductor chip 2 contacts 9. As a result, it causes a short and causes trouble. This is more likely to occur as we aim to increase the number of pins seen in recent package trends.

[0006] On the other hand, semiconductor elements have been further enhanced in functionality, and along with this, semiconductor devices have been moving toward further miniaturization and thinning. However, it is extremely difficult to use a conventional lead frame in order to miniaturize a multi-pin structure. In addition, if the reduction in thickness is pursued, the thickness of the sealing resin will be reduced, and there is a problem that the reflow crack as described above easily occurs.

[0007]

SUMMARY OF THE INVENTION The present invention improves the structure of a semiconductor device in order to solve the above problems of the current transition, thereby making the multi-pin structure smaller and thinner. Moreover, it is an object of the present invention to provide a semiconductor device in which a rack is not generated during reflow.

[0008]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, according to the present invention, in a lead frame in which a central die pad having an inorganic coating on the back surface is bent and the tip portions of the die pad leads connected to the central die pad are positioned in the descending position, It is formed in a short size, and the inner lead and the outer lead of the TAB or FPC are joined together, and the inner lead of the TAB or FPC and the electrode of the semiconductor element fixed to the die pad are connected by a bonding wire. The gist is a semiconductor device obtained by resin-molding the constructed structure.

The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows an example of a lead frame 12 used in the present invention, which has a die pad 14 connected and supported by a die pad lead 13 at a central portion thereof and an outer lead 12b connected by a dam member 15. And the inner lead 12a, the inner lead 12a is formed in a short length slightly extending from the dam member 15. When the inner leads are extended to the vicinity of the semiconductor chip, the tips become more densely packed as the number of pins increases, which results in fine leads, which makes it difficult to accurately process the leads. Therefore, in the present invention, the inner lead ends are cut out to be short, and the TAB tape or the FPC tape 11 (both abbreviated as TAB tapes hereinafter) is arranged at the position shown by the dotted line. A composite lead frame is formed by joining the short inner lead 12a and the outer lead 11b of the TAB tape 11. The lead of the TAB tape is formed by a method of plating the insulating film according to the resist pattern (two-layer TAB) or a method of bonding the Cu foil on the insulating film with an adhesive tape and then etching (three-layer TAB). As a result, it is possible to obtain leads having a fine pitch with a desired number of pins.

Further, according to the present invention, as shown in the semiconductor device of FIG. 2, the position of the die pad 14 is lowered by bending the tip portion of the die pad lead 13 connected to the die pad 14 to lower the position. Adjust to position. The semiconductor chip 2 is bonded and fixed to the die pad 14 in such a low position, but the surface position of the semiconductor chip 2 can be maintained at a desired low position. Therefore, the TAB tape 11 joined to and supported by the short inner leads 12a of the lead frame does not have a large level difference from the surface position of the semiconductor chip 2, and can be made to have substantially the same level, for example. The inner lead 11a of 11 and the electrode pad 5 of the semiconductor chip 2 can be connected by the bonding wire 6 with almost no drop. The TAB tape 11 is of a perforated type in which the resin in the central portion is removed to facilitate the flow balance of the sealing resin. With this configuration, when the bonding wire 6 is connected or when the resin is sealed, the bonding wire 6 is prevented from coming into contact with the edge portion of the semiconductor chip 2 and the structure after the resin sealing 7 is thin. You can

FIG. 3 shows another example of the present invention, which has a structure in which the inner lead 11a of the TAB tape 11 is joined and supported below the short inner lead 12a of the lead frame (other The description is omitted because the part is the same as the device of FIG. 2). Especially, the structure is easy to produce when using the FPC tape.

Further, in the present invention, the back surface of the die pad 14 is coated with the inorganic coating 16. Since this inorganic coating has extremely good adhesion to the sealing resin 7, both can be firmly bonded to form an interface with high adhesive strength, and even if moisture is adsorbed, the adhesive interface can be peeled off or peeled off. The occurrence of reflow cracks can be prevented. Further, such an action is useful for thinning and miniaturizing the sealing resin. The inorganic material, Al, Al oxide (Al _x O _y), Si oxide (Si _x O _y), Si nitride (Si _x N _y), Ti or Ti oxides (Ti _x O _y), Cr acid Compounds (Cr _x O _y ) and the like, which are covered in a single layer or a plurality of layers by a dry coating method such as thermal spraying, ion plating, plasma CVD, and sputtering. The reason for using an oxide (partially a nitride) of Al, Si, Ti, Cr or the like is that it has excellent corrosion resistance and heat resistance, and that it has extremely good adhesion to the sealing resin. Further, Al and Ti are oxidized (Al ₂ O ₃ , TiO ₂ ) when exposed to the air after coating, and the same effect as described above is obtained. In addition to the above oxides, Cr ₂ O ₃ , ZrO, CeO ₂ , ThO ₂ , MgO, BeO, etc. may be used, and a film of ZrN, HfN, VN, CrN, AlN, BN, etc. as a nitride is also applied. It is possible. In addition, it is preferable that the surface of the die pad is dull-processed in advance in a step before the inorganic coating. That is, by roughening the surface, the adhesiveness with the sealing resin or the bonding force of the inorganic coating can be improved. This rough surface formation can be performed, for example, by masking a portion that does not need to be roughened and partially performing a necessary portion by etching or the like.

As described above, according to the present invention, 144 pins are currently the maximum in the case of a body size of 20 × 20 mm, and 132 pins are the maximum in the case of 40 × 40 mm, while 265 and 265, respectively. It is possible to significantly increase the number of pins up to about 520 pins. Therefore, in combination with the structure of the device, it is possible to achieve extremely thin and small size compared to the conventional products.

[0014]

[Effect of device]

 As described above, the present invention uses the composite lead frame that is suitable for high integration and multi-pinization by combining the lead frame having the short inner leads and the TAB or FPC tape, and further, the die pad whose back surface is covered with the inorganic film is used. Since the structure is supported at a low position, the bonding wire is prevented from contacting the edge of the semiconductor chip, and the structure is extremely effective for thinning and downsizing, improving the bonding strength with the sealing resin. Therefore, it is possible to stably provide a highly reliable semiconductor device that can achieve resistance to reflow.

[Brief description of drawings]

FIG. 1 is an explanatory plan view showing an example of a lead frame used in the present invention.

FIG. 2 is an explanatory sectional view showing a semiconductor device of the present invention.

FIG. 3 is an explanatory sectional view showing another semiconductor device of the present invention.

FIG. 4 is an explanatory cross-sectional view showing a conventional semiconductor device.

FIG. 5 is an explanatory cross-sectional view showing another conventional semiconductor device.

[Explanation of symbols]

 1, 12: Lead frame 1a, 12a: Inner lead 1b, 12b: Outer lead 2: Semiconductor chip 3, 14: Die pad 7: Resin sealing 10: Crack 11: TAB tape 11a: Inner lead (TAB) 11b: Outer lead (TAB) 13: Die pad lead 15: Dam member 16: Inorganic coating

Claims (1)

[Scope of utility model registration request] 1. A lead frame in which a central die pad having an inorganic coating on the back surface is bent and the tip end portion of a die pad lead connected to the central die pad is bent to be positioned downward. The leads are joined to the outer leads of the TAB or FPC, and the inner leads of the TAB or FPC are connected to the electrodes of the semiconductor element fixed to the die pad by bonding wires, and the structure thus constructed is resin-molded. A semiconductor device comprising: