JPH0529530A - Cu based material for semiconductor package - Google Patents

Abstract

PURPOSE:To obtain Cu based material excellent in glass sealing properties, in various usages for a lead frame, a substrate, etc., for a semiconductor package, like lead frame material for a ceramics package as the usage necessary for nonmagnetic high conductivity for low inductance requirement. CONSTITUTION:On at least a surface to be glass-sealed when a package is assembled by molding a lead frame, or on the whole surface of inner leads, a thin Al film is formed by such a means as vapor deposition. A Cu material surface is not exposed on the surface at a position necessary for glass sealing and wire bonding. The reliability of the material for glass sealing is remarkably improved, and Al wire bonding properties can be ensured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly heat-conductive Cu-based material used for a lead frame or a substrate for a semiconductor package, and a semiconductor in which an Al thin film is provided on a required surface of the material to improve the glass sealing property. The present invention relates to a Cu-based material for packages.

[0002]

2. Description of the Related Art Conventionally, a lead frame material for a ceramic package is 29 wt% Ni-17 wt% Co-F.
A low thermal expansion material typified by an e alloy and a 42 wt% Ni-Fe alloy is used, and its reliability for glass sealing is very excellent.

However, the low thermal expansion material such as the Fe--Ni alloy has a large electric resistance and poor thermal conductivity and is not suitable for an element that generates a large amount of heat. Ferromagnetism causes a large lead inductance for high frequencies. However, there are problems such as being unsuitable, and unsuitable when the influence of the magnetization distortion on the signal system is concerned.

Although various Cu-based alloys are used as lead frame materials for semiconductor packages, they are used only in plastic packages because they cannot be glass-sealed.

[0005]

If the Cu-based alloy lead frame material can be used for the ceramic package, a ceramic package most suitable for use in high frequency power devices such as microwaves, transistors, ICs, etc. can be obtained. A Cu-based lead frame material having excellent properties has not been proposed.

The present invention can be applied to various applications such as lead frames and substrates for semiconductor packages, such as lead frame materials for ceramic packages for applications requiring non-magnetic high conductivity due to low inductance requirements.
The purpose is to provide a Cu-based material having excellent glass sealing properties.

[0007]

The present invention is a Cu-based material for a semiconductor package, which is characterized by having an Al thin film on at least a glass sealing surface of Cu or a Cu-based alloy material.

[0008]

When the present invention is used, for example, as a lead frame material for a ceramic package, at least the surface to be sealed with glass or the entire surface of the inner lead, that is, the IC chip of the lead frame when molded into a lead frame and assembled into a package. A desired position for glass sealing and wire bonding is provided by providing an Al thin film on the surface of the portion that comes into contact with the glass during glass sealing or the portion where wire bonding is performed between the substrate and the gap on which the glass is mounted by vapor deposition or the like. Since the Cu material surface is not exposed on the surface of, the reliability of the material for glass sealing can be significantly improved, or the Al wire bondability can be secured. In addition, A is formed on the entire surface of the Cu-based material.
By providing a thin film, deterioration of the material can be prevented.

In the present invention, as the Cu-based material, in addition to pure Cu, a Cu-based alloy containing various additive elements can be appropriately selected according to the application and required properties. For example, as the Cu-based alloy, known materials such as Cu-Fe-based, Cu-Cr-based, and Cu-Sn-based can be used. Further, in the present invention, as the Al thin film deposited on the Cu-based material, in addition to pure Al, an Al-based alloy containing various additive elements can be appropriately selected according to the use and required properties.

In the present invention, the method of depositing the Al thin film on the surface of the Cu-based material is vapor deposition on one surface, the entire surface or a glass sealing surface such as a stripe shape or an island shape of the material.
A known vapor deposition method such as sputtering is appropriately selected to form a film having a required thickness. For example, if the thickness of the Al thin film provided on the required surface of the lead frame material is less than 1 μm, aluminum and copper are alloyed by heating during glass sealing, and aluminum has the effect of improving the reliability of glass sealing. Moreover, since a thickness exceeding 10 μm is unnecessary for the purpose of improving the reliability of glass sealing, the thickness is set to 1 to 10 μm. Desirably 3-5 μm
Is.

[0011]

Example 1 The entire surface of a Cu alloy strip (composition 0.1% Fe-0.03% P-remaining Cu) having a thickness of 0.15 mm and a width of 20 mm was washed with an alkaline solution, and then, as shown in FIG. As shown in A, pure A is applied to the entire striped required surface and the back surface of the Cu alloy strip 1.
1 was vapor-deposited to a thickness of 3 to 5 μm to obtain a lead frame material having the Al thin film 2. Then, using a PbO-based low melting point glass, glass sealing was performed on an Al thin film of a Cu alloy strip at a thickness of 20 to 30 μm at a temperature of 420 ° C. for 15 minutes.
The glass sealing property was evaluated by shearing strength with glass.
The results are shown in Table 1. For comparison, 41 wt of the same size
% Ni-Fe alloy (ASTM F-30 Alloy equivalent material) material and the above Cu alloy strip without Al thin film were similarly glass-sealed, and the glass-sealing property was evaluated. The results are shown in Table 1. .

[0012]

[Table 1]

Example 2 Pure Cu strip (99.9) having a thickness of 0.15 mm and a width of 20 mm
% Cu) lead frame material is punched out to form a desired lead frame, and the entire surface is washed with an alkaline solution. Then, as shown in FIG. 1B, the entire surface of the Cu strip 3 is Al (composition 99.%). 99% Al) was evaporated to a thickness of 3 to 5 μm to form an Al thin film 4. Further, when the lead frame of the present invention having an Al thin film and the pure Cu lead frame of the comparative example as punched were subjected to a corrosion resistance test, the lead frame of the present invention showed a corrosion resistance several tens of times that of the comparative example. Further, the evaluation of the glass sealing property of Example 1 was the same as in Table 1. It can be seen that the lead frame of the present invention having the Al thin film is extremely effective in preventing deterioration of the pure Cu lead frame and has excellent glass sealing property.

[0014]

Since the Cu-based material according to the present invention has an Al thin film, it can be sealed with glass, and by using it in a ceramic package having high heat generation such as IC with high integration and power device. The amount of heat radiated from is increased, and the temperature rise can be suppressed.
Since it has good conductivity, it can be used for a transistor or the like in which electrical conductivity is a problem. In particular, Cu-based alloy leads can be used for high-frequency devices where plastic packages cannot be used due to dielectric loss, and non-magnetism reduces lead inductance, improving high-frequency characteristics, and improving device output for improved conductivity and heat dissipation. Can be expected. It has the effect of preventing deterioration of the Cu-based material. And other effects.

[Brief description of drawings]

1A and 1B are cross-sectional explanatory views of a Cu-based lead frame material according to the present invention, in which A is an example without punching and B is an example without punching.

[Explanation of symbols]

 1 Cu alloy strip 2,4 Al thin film 3 Cu strip

Claims (1)

1. A Cu-based material for a semiconductor package, which has an Al thin film on at least a glass sealing surface of Cu or a Cu-based alloy material.