JPH07142668A - Lead frame, manufacture thereof, and semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device excellent in electrical properties by a method wherein a lead frame matched to a certain characteristic impedance is prepared so as to mount a semiconductor chip which is capable of operating on high frequency at a high speed on a resin-sealed lead frame. CONSTITUTION:Dielectric films 12 and 14 coated with conductor layers 12a and 14a respectively are fixed to the upside and underside of an inner lead 10b by pressure, and the dielectric films 12 and 14 are kept at a grounding potential to constitute a strip line structure to the inner lead 10b, wherein dielectrics 12b and 14b of the films 12 and 14 and the films 12 and 14 are so controlled in thickness as to realize a required characteristic impedance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame, its manufacturing method and a semiconductor device.

[0002]

2. Description of the Related Art Resin mold packages are versatile,
Although it is widely used as a semiconductor device because of its low manufacturing cost, semiconductor chips to be mounted are mainly for low frequencies due to the electrical characteristics of the package, and high-speed and high-frequency semiconductor chips are for electrical packages such as ceramic packages. It is mounted in a package with excellent characteristics. For example, in the case of a ceramic package, the pattern width and pattern interval of the wiring pattern are designed appropriately, and the characteristic impedance is matched by appropriately designing the layer interval in consideration of the dielectric constant of the ceramic constituting the package body. Is possible.

[0003]

As a method of improving the electrical characteristics of the above resin mold package, a metal is attached to the outer surface of the package, but matching the characteristic impedance is especially required. Not done. This is probably because most resin-molded packages were mounted with semiconductor chips for low frequencies. However,
Recently, high-frequency semiconductor chips have become widely used, and since ceramic packages with high-frequency semiconductor chips are expensive, the required electrical characteristics can be obtained with a cheaper resin mold package. There is an increasing demand for products that have them.

An object of the present invention is to provide a lead frame excellent in electrical characteristics, capable of mounting a higher speed semiconductor chip, a method of manufacturing the same, and a semiconductor device in such a resin mold package.

[0005]

The present invention has the following constitution in order to achieve the above object. That is, in a lead frame, a dielectric film having a conductor layer coated on one surface is attached from the upper surface and the lower surface of the inner lead with the conductor layer outside, and the conductor layer is set to the ground potential with respect to the inner lead. It is characterized in that a stripline structure is formed, and the dielectric used for the dielectric film and the film thickness are adjusted to match a required characteristic impedance value. In addition, a conductor layer sandwiching the inner lead from the upper surface and the lower surface is connected at an intermediate position between adjacent inner leads, and each inner lead has a coaxial structure. Further, conductor layers sandwiching the inner lead from the upper surface and the lower surface are connected in a scattered manner at an intermediate position between adjacent inner leads to form a pseudo coaxial structure for each inner lead. Further, in the method for manufacturing a lead frame, a dielectric film having a conductor layer coated on one surface thereof is attached from the upper surface and the lower surface of the inner lead with the conductor layer facing outward, and a flat plate-like member is formed at an intermediate position between the adjacent inner leads. It is characterized in that a welding electrode is press-fitted to connect the upper and lower conductor layers to each other to form a coaxial structure for each inner lead. Further, a dielectric film having a conductor layer adhered on one surface is attached from the upper surface and the lower surface of the inner lead with the conductor layer facing outward,
A needle-shaped welding electrode is press-fitted into an intermediate position between adjacent inner leads to connect the conductor layers on the upper surface and the lower surface in a scattered manner, and a pseudo coaxial structure is formed for each inner lead.

Further, in the semiconductor device, a semiconductor chip is mounted on the lead frame and is resin-molded with a resin containing a filler of silicon carbide or aluminum nitride. Further, the semiconductor chip is connected to one end of the wiring pattern of the TAB tape having the conductor layer adhered to the back surface of the base film, and the wiring pattern faces the inner lead of the lead frame and is electrically connected to the inner lead. Are electrically connected, the conductor layer of the TAB tape is set to the ground potential, and resin-molded.

[0007]

The strip line structure is formed by attaching the dielectric film with the conductor layer to the inner lead portion of the lead frame to match the characteristic impedance of the lead frame. As a result, it is possible to obtain a product having excellent high-speed characteristics in the resin mold package. In addition, by performing resin molding using a resin containing filler of silicon carbide or aluminum nitride, it is possible to obtain a semiconductor device having excellent heat dissipation and electrical characteristics. Further, by mounting the semiconductor chip via the TAB tape, a semiconductor device having more excellent electrical characteristics can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a sectional view of an embodiment of a lead frame according to the present invention. In the lead frame of the embodiment, a die pad 10a, an inner lead 10b, and an outer lead 10c are formed in a predetermined pattern on a lead frame body 10 and polyimide films 12 and 14 with copper foil as a dielectric film with a conductor layer are attached by thermocompression bonding or the like. Wear it. Polyimide films 12 and 14 with copper foil are copper foil 1
The polyimide layers 12b and 14b are attached to the lead frame body 10 by thermocompression bonding or the like with 2a and 14a outside. An adhesive layer is formed on the pressure-bonded surfaces of the polyimide layers 12b and 14b. The copper foils 12a and 14a are connected to the ground lead of the lead frame body 10 to have a ground potential.

FIG. 2 shows a state in which the polyimide films 12 and 14 with copper foil are attached to the inner lead 10b portion as viewed from the end face side of the inner lead 10b. The inner leads 10b are polyimide films 12 and 1 with a copper foil.
Sandwiched from above and below by the polyimide layers 12b, 14b
It is buried inside. The inner lead 10b is a copper foil 12a,
It is sandwiched from both sides by 14a to form a strip line.

Since the polyimide layers 12b and 14b are dielectric layers, the thickness of the polyimide layers 12b and 14b is appropriately set, and the copper foils 12a and 14a are set to the ground potential, so that the characteristic impedance of the inner lead 10b is set to a predetermined value. The value can be adjusted. When the lead frame is manufactured, the thickness of the polyimide layers 12b and 14b is set in advance in consideration of the characteristic impedance value to be matched, and the lead frame body 10 is sandwiched between the polyimide films 12 and 14 with copper foil and attached. A lead frame with matching characteristic impedance can be obtained.

In the above embodiment, the lead frame body 10 is used.
Although the inner lead 10b and the polyimide film 14 with the copper foil are provided on the entire lower surface of the inner lead 10b, it may be provided only on the inner lead 10b for the purpose of matching the characteristic impedance of the inner lead 10b. In the case of the embodiment, the shape retention of the lead frame is improved by sticking the polyimide film 14 with the copper foil on the entire lower surface of the lead frame body 10, so that the radiator 16 can be attached to the outer surface of the copper foil 14a. The heat dissipation of the package can be improved.

Further, although the copper foil-attached polyimide films 12 and 14 are used in the above-mentioned embodiment, a strip line structure similar to that of the embodiment is constructed by using a dielectric material having an appropriate dielectric constant instead. Good. For example, it is possible to use a material mixed with a material having a high dielectric constant in order to adjust the dielectric constant of the dielectric. This is because the matching of the characteristic impedance is determined by the dielectric constant of the dielectric, the thickness of the dielectric (the distance between the signal lead and the conductor portion set to the ground potential), and the lead width of the signal lead. Moreover, since the copper foils 12a and 14a are used as conductor layers having a ground potential, they are not necessarily copper materials.

The lead frame formed by sticking a specific dielectric film on both surfaces of the lead frame body 10 as in the embodiment has an advantage that the characteristic impedance is not affected by the dielectric constant of the molding resin. Therefore, even if the resin is unsuitable as a molding resin due to its large dielectric constant, it is possible to use the lead frame of the embodiment type. For example, it is possible to use a resin containing a filler of silicon carbide or aluminum nitride in order to improve the heat dissipation of the molding resin. This makes it possible to provide a resin mold package having excellent heat dissipation.

In the above embodiment, the polyimide films 12 and 14 with copper foil are simply attached to both surfaces of the inner lead 10b, but the inner lead 10b is made to have better electric characteristics for each inner lead 10b.
An example in which b is coaxially structured is shown in FIGS.
As shown in FIG. In the embodiment shown in FIG. 3, after the polyimide tapes 12 and 14 with copper foil are adhered to the lead frame body, the flat plate-shaped welding electrode 20 is press-fitted into the intermediate position between the adjacent inner leads 10b to press the polyimide tape 12 with copper foil. , 14
Is clamped and the copper foil 12a and the copper foil 14a are welded between the inner leads 10b. In this case, each inner lead 10b has a substantially coaxial structure, and the electrical characteristics of the lead frame can be effectively improved.

In the embodiment shown in FIG. 4, after the polyimide tapes 12 and 14 with copper foil are adhered to each other, the needle-like welding electrode 22 presses the intermediate position of the inner lead 10b to weld the copper foil 12a on the upper side. And the lower copper foil 14a are connected in a scattered manner. The embodiment shown in FIG. 5 has an upper copper foil 1
A rib 24 is provided between the copper foil 12a and the lower copper foil 14a to partially connect the copper foil 12a and the copper foil 14a.
Although the embodiments shown in FIGS. 4 and 5 both have a pseudo coaxial structure, they have an advantage that the effects of matching characteristic impedance and preventing crosstalk are effectively exerted as compared with the embodiment shown in FIG.

When a semiconductor chip is mounted on the lead frame of the above-described embodiment, an empty space is formed above the semiconductor chip as shown in FIG. 1, so that the electrical characteristics of the package deteriorate at this portion. 6 and 7 show a method of mounting a semiconductor chip without deteriorating the electrical characteristics.
The lead frame shown in FIG. 6 shows a perspective view of the embodiment shown in FIG. Outer leads 10c of the lead frame body extend outward from the outer peripheries of the copper foil-attached polyimide tapes 12 and 14, a rectangular storage recess is formed in the mounting portion of the semiconductor chip, and the inner lead 10b is bonded inside the storage recess. The department is facing.

The semiconductor chip 30 has the inner lead 1
It is mounted by being electrically connected to the bonding part of 0b.
In this embodiment, the semiconductor chip 30 is mounted on the lead frame via the TAB tape 40. A wiring pattern 40b is provided on the TAB tape 40 in accordance with the pattern of the bonding portion of the inner lead 10b. After the wiring pattern 40b is attached to the chip, the TAB tape 40 is connected to the inner lead 10b of the lead frame. Figure 6
For the sake of description, a state in which the semiconductor chip 30 is mounted on the TAB tape 40 is shown upward. The copper foil 40a is also provided on the back surface of the TAB tape 40.

FIG. 7 shows a state in which the semiconductor chip 30 is mounted on the lead frame via the TAB tape 40.
As shown in the figure, the wiring pattern 40b of the TAB tape 40 and the inner lead 10b of the lead frame are located at opposite positions and are collectively bonded, and the semiconductor chip 30 is housed downward. The copper foil 40a of the TAB tape 40 is exposed outside. The copper foil 40a of the TAB tape 40 is also the tongue and TA
The semiconductor chip 30 and the inner lead 10b are connected to the ground lead by the via provided in the B tape and set to the ground potential, whereby the semiconductor chip 30 and the inner lead 10b are surrounded by the copper foils 12a, 14a, 40a having the ground potential.
The lead frame is resin-molded after mounting the semiconductor chip 30 in this way, and the semiconductor device thus obtained is provided as a product having excellent electrical characteristics in which characteristic impedance matching and crosstalk prevention are suitably performed.

[0019]

As described above, the lead frame according to the present invention is a resin-mold type lead frame, and the characteristic impedance can be matched, so that a high-speed and high-frequency semiconductor chip can be suitably mounted. become. In addition, the electrical characteristics of the lead frame can be improved by forming the inner lead in a coaxial structure or a pseudo coaxial structure. Further, by using a mold resin having excellent heat dissipation, it is possible to provide a semiconductor device having excellent heat dissipation and electrical characteristics. In addition, by mounting a semiconductor chip using a TAB tape, it is possible to obtain a remarkable effect such that a semiconductor device having more excellent electrical characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a lead frame.

FIG. 2 is an explanatory diagram showing an end face structure of an inner lead.

FIG. 3 is an explanatory diagram of forming inner leads and a copper foil-coated polyimide tape in a coaxial structure.

FIG. 4 is an explanatory diagram in which an inner lead and a polyimide tape with a copper foil have a pseudo coaxial structure.

FIG. 5 is an explanatory diagram showing an inner lead and a polyimide tape with a copper foil having a pseudo-coaxial structure.

FIG. 6 is an explanatory diagram of mounting a semiconductor chip on a lead frame.

FIG. 7 is a sectional view showing a state in which a semiconductor chip is mounted on a lead frame.

[Explanation of symbols]

 10 Lead frame body 10b Inner lead 10c Outer lead 12, 14 Polyimide tape with copper foil 12a, 14a Copper foil 12b, 14b Polyimide layer 16 Radiator 20, 22 Welding electrode 24 Rib 30 Semiconductor chip 40 TAB tape 40a Copper foil 40b Wiring pattern

Claims (7)

[Claims] 1. A dielectric film having a conductor layer coated on one surface thereof is attached from the upper surface and the lower surface of the inner lead with the conductor layer facing outward, and the conductor layer is grounded to form a strip with respect to the inner lead. A lead frame comprising a line structure and adjusting a dielectric used in the dielectric film and a film thickness to match a required characteristic impedance value. 2. The lead frame according to claim 1, wherein conductor layers sandwiching the inner lead from the upper surface and the lower surface are connected at an intermediate position between adjacent inner leads to form a coaxial structure for each inner lead. 3. A pseudo coaxial structure is formed for each inner lead by connecting conductive layers sandwiching the inner lead from the upper surface and the lower surface in a scattered manner at an intermediate position between adjacent inner leads. Lead frame as described. 4. A dielectric film having a conductor layer coated on one surface thereof is attached from the upper surface and the lower surface of the inner lead with the conductor layer facing outward, and a flat plate-shaped welding electrode is press-fitted at an intermediate position between adjacent inner leads. Then, the conductor layers on the upper surface and the lower surface are connected to each other, and a coaxial structure is formed for each inner lead. 5. A dielectric film having a conductor layer coated on one surface thereof is attached from the upper surface and the lower surface of the inner lead with the conductor layer facing outward, and a needle-shaped welding electrode is press-fitted at an intermediate position between adjacent inner leads. Then, the conductor layers on the upper surface and the lower surface are connected in a scattered manner, and a pseudo coaxial structure is formed for each inner lead. 6. A semiconductor device comprising a semiconductor chip mounted on the lead frame according to claim 1, 2 or 3, and resin-molded with a filler-containing resin of silicon carbide or aluminum nitride. 7. A lead frame according to claim 1, 2 or 3, wherein a semiconductor chip is connected to one end of a wiring pattern of a TAB tape having a conductor layer adhered to the back surface of a base film. A semiconductor device characterized in that it is electrically connected to the inner lead so as to face the inner lead, and the conductor layer of the TAB tape is set to a ground potential and resin-molded.