JPH07183421A - Semiconductor package - Google Patents

Abstract

PURPOSE:To especially improve the transmission characteristics (signal delay) of a high frequency signal, and remarkably decrease crosstalk noise or the like by using a package having a lead frame structure of low cost. CONSTITUTION:A semiconductor chip 2 is mounted in the cavity 1a or a ceramics substrate 1. A lead frame 6 wherein at least the surface of a wiring part is covered with an insulating layer 5 is bonded to the semiconductor mounting surface side of the ceramics substrate 1, with conductive sealing material 4 which is electrically connected with a reference voltage like a ground voltage, a power supply voltage, etc. The semiconductor chip 2 and the lead frame 6 are electrically connected through bonding wires 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor package using a ceramic substrate.

[0002]

2. Description of the Related Art Generally, as a semiconductor chip package, a plastic package, a metal package, or a ceramic package is used. Of these, particularly the ceramic package has high reliability in hermetically sealing the LSI, and has excellent moisture resistance and heat dissipation, so that a CMOS gate array or E
It is used for packaging CL gate arrays.

The structure of the above-mentioned ceramic package includes a DIP (dual inline package) using a lead frame, a QFP (quad flood package), a PGA (pin grid array) using lead pins, and an input / output land. The LGA (land grid array) used and the like are known. Among these, the package using the lead frame is widely used for various semiconductor chips because of its simple structure and low cost. In particular, the QFP is widely used because it can cope with an increase in the number of input / output signals and is a surface mount type.

The lead frame of the above-mentioned ceramic package is generally 42 wt% Ni-Fe or 29 wt% Ni-16 wt% Co-
Fe-Ni based alloys such as Fe and Cu-based alloys such as Cu-Cr-Zr are used, and as such a lead frame sealing material,
Insulating sealing materials such as sealing glass and epoxy resin are used.

Meanwhile, in recent semiconductor chips, there is a strong tendency to increase the operating frequency (system clock frequency) in order to increase the operating speed, and the problem due to crosstalk noise is becoming more prominent. In the conventional ceramic package described above, the insulating sealing material is only interposed between the signal lines in the lead frame,
Since electric capacitance is generated between the signal lines, there is a problem that crosstalk noise or the like is likely to occur.

On the other hand, as a measure against the signal delay, for example, by providing an Al thin film or the like electrically connected to the ground on the ceramic substrate side, the electrical coupling between the signal lines in the lead frame is reduced. Although attempts have been made to achieve this, this method cannot be said to be sufficient because only one surface of the lead frame can be electrically coupled to the ground, and it is attempted to cope with recent high-frequency semiconductor chips. Therefore, it is desired to further reduce the electric capacitance between the signal lines.

[0007]

As described above, the conventional ceramic package using a lead frame, especially QFP, has a simple structure, can be manufactured at low cost, and can cope with an increase in the number of input / output signals to some extent. On the other hand, the electric capacitance between the signal lines in the lead frame is large, and the crosstalk noise becomes remarkable especially in the high frequency region, and the signal delay etc. becomes large due to the electric capacitance generated between the signal lines. Had a problem.

The present invention has been made to solve the above problems, and is a semiconductor package having an inexpensive lead frame structure, in which crosstalk noise is improved especially in a high frequency region and signal delay is improved. Is intended to provide.

[0009]

A semiconductor package according to the present invention comprises a ceramic substrate on which a semiconductor chip is mounted,
A semiconductor package comprising: a lead frame joined to a mounting surface side of the semiconductor chip of the ceramic substrate via a sealing material; and a connecting means for electrically connecting the semiconductor chip and the lead frame, The frame is characterized in that at least the surface of the wiring portion is covered with an insulating layer, and a conductive material electrically connected to a reference potential is arranged outside the insulating layer. In the above semiconductor package,
The conductive material is the sealing material having conductivity.

[0010]

In the semiconductor package of the present invention, by individually covering the signal lines in the lead frame with the insulating layer,
The lead frames are electrically insulated, and a conductive material connected to a reference potential such as a power supply potential or a ground potential is placed between the lead frames to prevent an electric capacitance from being generated between the signal lines. Therefore, even when a semiconductor chip having a high operating frequency is mounted, it is possible to reliably prevent the occurrence of crosstalk noise and reduce the signal delay. By these,
It is possible to significantly improve the pass characteristic of a high frequency signal.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a sectional view showing a schematic structure of a semiconductor package (QFP) according to an embodiment to which the present invention is applied. In the figure, reference numeral 1 is a ceramic substrate having a cavity 1a that serves as a housing portion for the semiconductor chip 2. As the material of the ceramic base 1, various ceramics sintered bodies can be applied, but in consideration of heat dissipation, a high thermal conductivity ceramics sintered body, for example, a sintered body containing aluminum nitride as a main component. It is preferable to use the body.

Cavity 1a of the ceramic substrate 1
A chip mounting portion 3 is provided therein, and the semiconductor chip 2 is bonded and mounted on the chip mounting portion 3 using a paste such as Ag-polyimide or Ag-glass. Also,
The mounting surface side of the semiconductor substrate 2 of the ceramic substrate 1,
That is, a lead frame 6 having an insulating layer 5 on its surface is bonded to the outer edge-side convex end surface 1b of the ceramic substrate 1 by a conductive sealing material 4. The lead frame 6 and each electrode of the semiconductor chip 2 are electrically connected by a bonding wire 7. The material of the lead frame 6 is 42wt% Ni-Fe or 29wt% Ni-16wt% C
Fe-Ni-based alloys such as o-Fe and Cu-based alloys such as Cu-Cr-Zr are used. It is preferable to use non-magnetic Cu-based alloys in order to improve high frequency characteristics.

On the lower surface side of the ceramic substrate 1 on which the semiconductor chip 2 is bonded and mounted, the insulating layer 5 is formed on the surface.
The ceramics sealing member 8 is joined by the sealing material 4 having the same conductivity through the lead frame 6 having the above, and the semiconductor chip 2 is hermetically sealed. As the material of the ceramics sealing member 8, various ceramics sintered bodies can be applied, but in consideration of heat dissipation, it is preferable to use a sintered body containing aluminum nitride as a main component. Mullite is also effective. In the lead frame 6 described above, as shown in FIG. 2, the surface of the inner lead portion (portion existing inside the semiconductor package: wiring portion, etc.) is covered with the insulating layer 5 except for the wire bonding portion 9. , Between leads (for example, 6a and 6)
(b) is insulated. The insulating layer 5 may extend to a part of the outer lead portion. Here, the leads 6a and 6b indicate leads functioning as signal lines, and the signal line leads 6a and 6b are covered with the insulating layer 5 as described above. Such a lead frame 6 is joined to the ceramic substrate 1 by a conductive sealing material 4, and the conductive sealing material 4 is electrically connected to a reference potential.

In the semiconductor package of this embodiment, an insulating layer is not formed on the surface of the ground lead 6c, and the ground lead 6c and the conductive sealing material 4 are directly electrically connected. is doing. The reference potential for connecting the conductive sealing material 4 is not limited to the ground potential, but may be a constant potential, and it is also possible to connect to the power source potential, and similar effects can be obtained. When the conductive sealing material 4 is connected to the ground lead 6c, the insulating layer 5 is naturally formed on the surface of the power supply lead. In addition, the conductive sealing material 4 is electrically
It is also possible to adopt a configuration in which it is divided into two, one is connected to the ground potential and the other is connected to the power supply potential.

As the conductive sealing material 4, a glass-based sealing material or a resin-based sealing material, which is a normal sealing material, to which a conductive material such as Ag filler is added can be used. . The type of the sealing material 4 may be either glass-based or resin-based as described above. For example, when a Cu-based alloy is used as the material of the lead frame 6, the ceramic base 1 and the Cu alloy-based lead frame 6 are Since the difference in the coefficient of thermal expansion is large, it is preferable to use the resin-based sealing material in order to relieve the thermal stress caused by the difference in the coefficient of thermal expansion.

As the material of the insulating layer 5 covering the surface of the lead frame 6, for example, when a resin-based sealing material is used as the conductive sealing material 4, it is preferable to use the same resin-based insulating material. When a glass-based sealing material is used as the conductive sealing material 4, it is preferable to use a material having high compatibility with glass, such as an insulating oxide layer. As a result, it is possible to improve the hermetic sealing property and the reliability. The insulating layer 5 made of a resin-based insulating material is formed on the necessary surface of the lead frame 6 by using, for example, a dipping method or a spray coating method. The insulating layer 5 made of an insulating oxide or the like can be formed by subjecting the lead frame 6 to surface oxidation treatment or the like.

In this embodiment, the lead frame 6
A Cu-Cr-Zr-based material is used as the lead (5a, except for the ground lead 6c of the Cu-Cr-Zr-based lead frame 6).
The surface of the inner lead portion (excluding the wire bonding portion 9) of 5b) was coated with an epoxy resin to form the insulating layer 5. Then, an epoxy resin added with an Ag filler was used as the conductive sealing material 4 and was joined to the ceramic substrate 1 made of an aluminum nitride sintered body to form a semiconductor package. A mullite sealing member was used as the ceramics sealing member 8, and the epoxy resin containing Ag filler was also used for bonding.

Using the semiconductor package thus constructed, the signal passing characteristics and crosstalk noise were evaluated. Further, as a comparison with the present invention, a semiconductor package is formed by joining an aluminum nitride sintered body ceramic base with a normal insulating sealing material (epoxy resin) without forming an insulating layer on the surface of the lead frame. Was produced. In addition, the constituent materials and the like of the lead frame and the sealing member were the same as those in the above-mentioned embodiment.

The signal transmission characteristic of the semiconductor package is 300 k
Network analyzer with bandwidth from Hz to 6 GHz
(HP8753C) was used for measurement. Crosstalk noise was evaluated using a pulse generator and digital scope. As a result, regarding the signal passage characteristics, the semiconductor package of the example was able to pass a high-frequency waveform about three times as high as that of the semiconductor package of the comparative example. The crosstalk noise was reduced to about 1/10.

In addition, in the semiconductor package of the above-mentioned embodiment, the same characteristic evaluation is performed for the semiconductor package having the same configuration except that the reference potential for connecting the conductive sealing material 4 is changed from the ground potential to the power source potential. Then, the same result as that of the semiconductor package in which the conductive sealing material 4 was connected to the ground potential was obtained.

In the semiconductor package of the above-described embodiment, the conductive sealing material 4 connected to the reference potential such as the power source potential or the ground potential is arranged between the signal line leads 6a and 6b. An electric capacitance is not generated between the leads 6a and 6b, so that they are not electrically coupled. This allows
Even when the semiconductor chip 2 having an increased operating frequency is mounted, it is possible to reliably prevent generation of crosstalk noise and the like, and it is possible to reliably suppress signal delay. Therefore, it becomes possible to significantly improve the passing characteristic of the high frequency signal.

As described above, in the semiconductor package of the present invention, since the package structure itself is a structure using a simple lead frame, the pass characteristic of the high frequency signal is significantly improved in the inexpensive lead frame structure package. It is possible to reduce the noise, and it is possible to significantly improve the reliability of the operating characteristics of the high-speed operation type or highly integrated type semiconductor element 2. further,
By using an aluminum nitride sintered body with excellent thermal conductivity as the ceramic substrate 1 and using a QFP structure as the package structure, it is possible to handle an input / output signal number of 100 or more and to improve heat dissipation as a package. It is possible to improve the reliability of the semiconductor package and reduce the size of the package.

In the above embodiment, an example in which the conductive sealing material is used as both the sealing material between the lead frame and the ceramic substrate and the sealing material between the lead frame and the ceramic sealing member is shown. Even when a conductive sealing material is used as one of these sealing materials, the same effect can be obtained.

In the above embodiment, an example in which the present invention is applied to a cavity-down type semiconductor package has been described. However, the same effect can be obtained also in a cavity-up type semiconductor package. To be Further, in the above-mentioned embodiment, the conductive sealing material 4 is used as the conductive material arranged around the insulating layer 5, but the conductive material can be arranged separately from the sealing material. However, the use of the conductive sealing material 4 has an advantage that the connection with the reference potential is facilitated.

[0026]

As described above, according to the semiconductor package of the present invention, it is possible to particularly improve the signal delay of the high frequency signal and to significantly reduce the crosstalk noise and the like. Therefore, for example, it is possible to provide an inexpensive semiconductor package capable of stably operating a high-speed operation type or highly integrated type semiconductor chip.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a semiconductor package according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part of the semiconductor package shown in FIG.

[Explanation of symbols]

 1 ... Ceramic substrate 2 ... Semiconductor chip 4 ... Conductive sealing material 5 ... Insulating layer 6 ... Lead frame 6a, 6b ... Signal wire lead 6c ... Ground lead 7 ... Bonding wire 8 ... Ceramics Sealing member

Claims (2)

[Claims] 1. A ceramic base on which a semiconductor chip is mounted, and a lead frame bonded to the mounting surface side of the semiconductor base of the ceramic base via a sealing material,
In a semiconductor package comprising a connecting means for electrically connecting the semiconductor chip and a lead frame, in the lead frame, at least a surface of a wiring portion is covered with an insulating layer, and the lead frame is provided outside the insulating layer. A semiconductor package, in which a conductive material electrically connected to a reference potential is arranged. 2. The semiconductor package according to claim 1, wherein the conductive material is the sealing material having conductivity.