KR930012180B1 - Lead frame material of bare bonding - Google Patents

Abstract

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Description

[Name of invention]

Lead Frame Material for Bare Bonding

Detailed description of the invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bare bonding leadframe materials, and more particularly to bare bonding, which does not adversely affect component elements of leadframe materials to semiconductor devices even when barebonding is performed using Au-Si eutectic alloying. It relates to a lead frame material.

[Prior art]

The assembling process of a semiconductor consists of a die bonding process for joining an element (semiconductor chip) and a lead frame, a wire-bonding process for connecting the element wiring and the lead frame with Au or Al wire, and a process of sealing with resin.

In these processes, since the lead frame is heated, the lead frame material used is not softened by these heatings, that is, heat resistance is required.

On the other hand, copper alloys (copper alloys) having excellent thermal conductivity and electrical conductivity have been used as lead frame materials mainly for applications requiring good heat dissipation such as transistors.

These copper-based lead frame materials are made of a copper alloy containing various additive elements in order to satisfy the properties required as lead frame materials such as heat resistance and mechanical strength.

In the die bonding step, the element and the lead frame are usually joined by three kinds of methods.

That is, Au-Si eutectic alloy adhesion method, solder adhesion method, and conductive resin adhesion method.

Among these methods, the Au-Si eutectic alloying method performs bonding by heating the element and the lead frame for several tens of seconds at a temperature of 420 to 440 ° C. which is 50 to 70 ° C. higher than the process temperature of 370 ° C.

However, the demand for cost-down in semiconductor devices is strong, and as a means of this, a technique called "bare bonding", which performs die bonding or wire bonding without the plating on the lead frame, which has been conventionally performed, is being widely carried out mainly on transistors. . In this bare bonding, die-bonding by the Au-Si eutectic alloying method has been found to cause a change in the characteristics of the semiconductor device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a bare frame lead frame material which is excellent in heat resistance and mechanical strength without causing any change in the characteristics of a semiconductor device even when bare bonding is carried out using Au-Si eutectic alloy bonding method. .

The bare frame lead frame material according to the present invention is characterized by containing Fe: 0.5 to 3.0 wt%, Si: 0.005 to 0.25 wt%, Zn: 0.05 to 1.0 wt%, and the balance is substantially made of Cu.

The knowledge gained in achieving the present invention from the action of the present invention will be described below with the reason for component limitation.

The present inventors first clarified the cause of the change in the characteristics of the semiconductor element when the bare bonding was carried out using the Au-Si eutectic alloy bonding method.

As a result, the following facts were released: That is, component elements in the copper alloy lead frame in contact with the molten Au-Si layer while heated at 400 to 440 ° C. for several tens of seconds pass through the Au-Si layer and diffuse into the Si element.

Among the elements diffused in Si, N, P, As, Sb, etc. belonging to group B, Al, Ga, In, or group Vb belonging to Periodic Group IIIb act as acceptors and donors to Si semiconductors, respectively. To form a semiconductor. In the case of a transistor, the bottom portion of a Si element, which is bonded to a lead frame, is generally a collector. In this region, elements belonging to the group IIIb or group Vb invade from the lead frame to form an impurity semiconductor, thereby affecting the electrical characteristics of the transistor. It was found to be adversely affected.

That is, the conventional copper alloy contained various additional elements in order to improve heat resistance and mechanical strength, and these additive elements caused the deterioration of the electrical characteristics of the semiconductor element.

In the case of applying the Au-Si eutectic alloy bonding method to the bare bonding, if the copper-based lead frame material contains a component element belonging to group IIIb or group Vb, there is a problem that the Si element is adversely affected as described above. That's why.

Therefore, in such a case, a cheap lead frame material which is a copper alloy having high heat resistance, conductivity, and mechanical strength and does not contain component elements belonging to Group IIIb or Group Vb is required.

Here, the inventors have studied a cheap bare-bonding copper-based lead frame material which does not contain elements belonging to Groups IIIb and Vb, which adversely affect Si elements, as well as having high conductivity, required strength, and excellent heat resistance. It was.

As a result, even if it did not contain an additional element, when the basic component was restrict | limited to the predetermined | prescribed range, it discovered that the lead frame which has the outstanding heat resistance and mechanical strength was obtained, and came to this invention.

First, the components and proportions of the bare frame lead frame material according to the present invention will be described.

(Fe)

Fe is an element which contributes to the improvement of strength and heat resistance by finely depositing in Cu. If the content of Fe is less than 0.5 wt%, the effect is small. If the content of Fe is more than 3.0 wt%, the strength and the heat resistance are improved.

Moreover, since the Fe which crystallized is easy to come out, it may not be suitable at the time of plating. Moreover, since it takes time for Fe to melt | dissolve at the time of melt | dissolution, it becomes a cost up.

Therefore, Fe content is made into 0.5 to 3.0 wt%.

(Si)

Si is an element that becomes a deoxidizer during ingot, reduces oxygen in the molten metal, eliminates defects generated in the ingot, and creates a good ingot.

The effect is less than 0.005 wt%, and when contained in excess of 0.25 wt%, there exists deoxidation effect, but cold workability and annual workability fall.

Furthermore, the deterioration of the peeling resistance of the solder and the electrical conductivity decrease.

Therefore, Si content is made into 0.005 to 0.25 wt%.

(Zn)

Zn is an element that improves the peeling resistance of the solder. When the content is less than 0.05 wt%, the effect is small. When Zn is contained in excess of 1 wt%, the effect is saturated and the conductivity is lowered.

Therefore, Zn content is 0.05 to 1 wt%.

None of the above component elements belong to group IIIb or group Vb. Therefore, even if the lead frame material according to the present invention is omitted without die plating and die-bonded by the Au-Si eutectic alloying method, these elements do not diffuse into the Si element and thus do not adversely affect the characteristics of the Si element.

On the other hand, elements such as B, Al, Ga, In, N, P, As, and Sb belonging to Group IIIb and Group Vb are included in the raw materials as impurities and penetrate into the manufactured copper alloy.

Therefore, the intrusion into the target copper alloy is prevented by regulating content in a raw material. As is evident from the above description, the content of these impurities is preferably small, and depending on the semiconductor used, 0.001% or less is preferable in either case.

EXAMPLE

A bare bonding lead frame material according to the present invention will be described with reference to Examples.

The alloying components and content ratios shown in the first table were melted in the air under charcoal coating using a creeptolo, and a 45 mmt x 75 mmw x 200 mm ingot was cast using a cast iron book mold. In Comparative Example No. 7, a defect due to deoxidation deficiency occurred in the ingot, so that subsequent sample adjustment was abandoned.

Next, the front and back surfaces of the ingot were hot rolled to 15 mmt at a temperature of 850 ° C. after being chamfered by 2.5 mm, and water cooled at a rate of 30 ° C./sec from a temperature of 700 ° C. or higher.

Furthermore, after cold-rolled to 0.5 mm plate thickness, after annealing for 2 hours at the temperature of 580 degreeC, when it reached 500 degreeC in the middle of cooling, annealing for 4 hours was performed further.

Thereafter, 0.3 mmt of sheet material was obtained by cold rolling.

The following tests were done about these samples.

The test results are shown in the second table.

The test method is as described below.

(1) The electrical conductivity was calculated from the electrical resistance value measured by the double bridge using the test piece of 15 mmw x 300 mml.

(2) Hardness was measured at a load of 500 gr using a micro-Vickers hardness tester.

(3) The heat resistance was measured for 5 minutes by heating at each temperature using a saltpeter, and then the hardness was measured. The hardness after heating was evaluated as the temperature at which 80% of the hardness before heating was obtained.

(4) The peeling resistance of the solder was soldered by immersing 60Sn-40Pb solder in a 20 mmw x 50 mml test piece for 5 seconds at a temperature of 230 ° C. using a weakly active flux and then heating it at a temperature of 150 ° C. for 1000 hours to 180 with 2 mm R. Bent to < RTI ID = 0.0 > The spread was intact and evaluated for the presence or absence of peeling.

As apparent from Table 2, alloy Nos. 1 to 4 of the present invention have good electrical conductivity of 70% IACS or higher, hardness of Vickers hardness of Hv 110 or higher, and heat resistance of 400 ° C or higher.

Moreover, the peeling resistance of a solder is also favorable by the effect of Zn.

On the other hand, Comparative Example No. 5 is excellent in electrical conductivity but inferior in hardness, and further has low heat resistance at 380 ° C. Although No. 6 also has good hardness, heat resistance conductivity, and peeling resistance of the solder, Fe contained more than 3.0 wt%, so that melting of Fe takes time, resulting in cost up. No. 8 had a Si content of more than 0.2 wt%, and No. 9 had a Zn content of less than 0.05 wt%, resulting in peeling of the solder. In No. 10, since the Zn content exceeded 1.0 wt%, the electrical conductivity decreased.

TABLE 2

[Effects of the Invention]

As described above, since the bare-bonding lead frame material according to the present invention has the above-described configuration, it is excellent in conductivity, strength and heat resistance, and is inexpensive. Even if die-bonding is performed, it does not adversely affect an element.

Claims (1)

A bare frame lead frame material comprising Fe: 0.5 to 3.0 wt%, Si: 0.005 to 0.25 wt%, Zn: 0.05 to 1.0 wt%, and the balance is substantially made of Cu.