JPH05345941A - Lead frame material made of cu alloy for resin sealed semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the adhesive strength of a lead frame material made of a Cu alloy and used for a resin sealed semiconductor device to an epoxy resin as a sealing material. CONSTITUTION:This lead frame material for a resin sealed semiconductor device is made of a Cu alloy having a compsn. consisting of, by weight, 1-4% Ni, 0.1-1% Si, 0.1-2% Zn, 0.001-0.05% Mg, 0.05-1% Sn and the balance Cu with inevitable impurities including <=20ppm S and <=20ppm C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Cu alloy lead frame material for a resin-encapsulated semiconductor device having a high adhesion strength to an epoxy resin encapsulant.

[0002]

2. Description of the Related Art Conventionally, transistors, ICs, LSIs, etc. are generally known as semiconductor devices.
Among these, for example, as one of the methods for manufacturing a resin-encapsulated IC, (a) First, a plate thickness as a lead frame material:
Prepare a Cu alloy strip having 0.1 to 0.3 mm,
(B) Forming a lead frame that conforms to the shape of the IC to be manufactured by etching or press punching from the lead frame material, and (c) then forming high purity Si, Ge, or the like at a predetermined position on the lead frame. The semiconductor chip is heat-bonded using a conductive resin such as Ag paste, or Au, A previously formed on one surface of the semiconductor chip and the lead frame material.
soldering or Au brazing via a plating layer composed of g, Ni, Cu, or an alloy thereof,
(D) The semiconductor chip and the lead frame are connected by using Au ultrafine wires, Cu ultrafine wires, or the like as bonding wires, and (e) subsequently, the semiconductor chips, bonding wires, and semiconductor chips An epoxy resin is used as a sealing material for the purpose of protecting the lead frame to which is attached, and the lead frame is sealed. (F) Finally, the mutually continuous portions of the lead frame are cut off. At the same time, the mounting foot of the lead frame is plated with an Sn-Pb alloy solder material by an immersion method to form an IC.
A method including the basic step (f) is known.

Further, various Cu alloys are used as lead frame materials in the manufacture of the resin-sealed semiconductor device. One of these Cu alloys is% by weight (hereinafter,% means% by weight). ), Ni: 1 to 4%, Si: 0.1 to 1%, Zn: 0.1 to 2%, Mg: 0.001 to 0.0
A Cu alloy containing 5% and the balance of Cu and unavoidable impurities is known, and since this Cu alloy has excellent strength and heat peeling resistance of solder, it is widely used in practice. It is also known.

[0004]

On the other hand, the high integration of semiconductor devices has been remarkable in recent years, and accordingly, the resin-encapsulated semiconductor devices described above are expected to be used under severe conditions. However, since the above-mentioned conventional Cu alloy lead frame material that constitutes the lead frame material does not have sufficient adhesion strength to the epoxy resin that is the sealing material, peeling easily occurs in a relatively short period of practical use. The outside air (especially moisture) enters through a small gap formed between the sealing material and the sealing material, which causes corrosion of the constituent members, which causes a problem in reliability. Is the current situation.

[0005]

Therefore, the present inventors have
From the above viewpoint, focusing on the Cu alloy lead frame material used in the resin-sealed semiconductor device,
As a result of research to improve the adhesion strength with respect to an epoxy resin as a sealing material, it is contained as an unavoidable impurity in the above-mentioned conventional Cu alloy lead frame material used in the above resin-sealed semiconductor device. When the contents of sulfur (S) and carbon (C) are S: 20 ppm or less and C: 20 ppm or less respectively, and 0.05 to 1% of Sn is contained as an alloy component, the resulting Cu alloy The lead frame material made of epoxy resin has significantly improved adhesion strength of epoxy resin to the encapsulant without impairing the strength and the heat-resistant peeling property of solder, and suppresses the occurrence of peeling even when used under severe conditions. The research result that it comes to be obtained.

The present invention was made based on the above research results, and Ni: 1 to 4%, Si: 0.1 to 1%, Zn: 0.1 to 2%, Mg: 0. 001-0.0
5%, Sn: 0.05 to 1%, and the balance of Cu and inevitable impurities, and the contents of S and C contained as inevitable impurities are S: 20 ppm or less and C: 20 ppm or less, respectively. It is characterized by the Cu alloy lead frame material of the resin-sealed semiconductor device composed of the Cu alloy having the above composition.

Next, the reason why the component composition of the Cu alloy constituting the lead frame material of the present invention is limited as described above will be explained. (A) Ni and Si Both components are combined and finely dispersed in the matrix.
It forms an intermetallic compound mainly composed of Ni ₂ Si and has an effect of improving strength, but its content is Ni:
If it is less than 1% and Si: less than 0.1%, the desired strength-improving effect cannot be obtained. On the other hand, if the Ni content exceeds 4%, the conductivity tends to decrease, and the Si content is 1%. If the content of Ni exceeds 1 to 4, the hot workability will be deteriorated. Therefore, the contents of Ni: 1 to 4% and Si: 0.1 to 1 respectively.
Defined as%.

(B) Zn The Zn component has the function of improving the heat-resistant peeling property of the solder, but if the content is less than 0.1%, the desired effect cannot be obtained on the above-mentioned function, while the content thereof is When the content exceeds 2%, the conductivity will suddenly decrease, so the content was defined as 0.1 to 2%.

(C) Mg The Mg component has a function of improving hot workability,
If the content is less than 0.001%, the desired hot workability improving effect cannot be obtained, while if the content exceeds 0.05%, no further improving effect appears. Was determined to be 0.001 to 0.05%.

(D) Sn The Sn component has an action of improving the adhesion strength with the epoxy resin as the encapsulating material as described above, but if the content thereof is less than 0.05%, the desired action is improved. The effect is not obtained, and on the other hand, when the content exceeds 1%, the conductivity is lowered, so the content is set to 0.05 to 1%.

(E) S and C as unavoidable impurities Generally, this type of Cu alloy contains S and C as unavoidable impurities in an amount of 30 ppm or less, respectively. However, unless the S and C contents are 20 ppm or less, respectively, Since the desired effect of improving the adhesion strength due to Sn cannot be obtained, the content of each of S and C must be limited to 20 ppm or less.

[0012]

EXAMPLES Next, the lead frame material made of Cu alloy according to the present invention will be specifically described by way of examples. Using a normal high-frequency induction melting furnace, Cu alloy melts having the composition shown in Tables 1 to 3 were prepared, and the dimensions of thickness: 150 mm × width 500 mm × length: 3000 mm were measured by the semi-continuous casting method. The ingot was made, and the ingot was hot-rolled at a rolling start temperature of 950 ° C. to form a hot-rolled sheet having a thickness of 11 mm, and after water cooling,
The upper and lower surfaces of the hot-rolled sheet were chamfered to a thickness of 10 mm, and cold-rolled, annealed, and pickled repeatedly to obtain a cold-rolled sheet having a thickness of 0.4 mm. The cold-rolled sheet was kept at a temperature of 900 ° C. for 2 minutes and then subjected to a continuous solution treatment under the condition of water cooling, and finally cold-rolled to a thickness of 0.25 mm. The lead frame materials 1 to 11 of the present invention, the conventional lead frame materials 1 to 9 which do not contain Sn as an alloy component, and the content of any one of the constituents Comparative lead frame materials 1 to 7 each made of a Cu alloy having a composition (marked with * in Table 2) outside the scope of the present invention were manufactured.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

Next, with respect to various lead frame materials obtained as a result, Vickers hardness (load: 500 g) was measured for the purpose of evaluating the strength, and the electrical conductivity was measured, and the epoxy resin adhesion test and soldering were performed. The heat peel test was performed.

In the heat peeling test of the solder, a test piece having a width of 15 mm and a length of 60 mm was used. The test piece was treated with rosin flux, and the temperature was 230 ° C. and 60% Sn.
After immersing in a solder bath composed of -40% Pb alloy and plating the surface with the solder, and then heating this in the atmosphere at a temperature of 150 ° C for 1000 hours,
The center of the test piece was bent by 180 ° and overlapped with each other, and then the sample was bent again by 180 ° to restore it to the original state, and the presence or absence of solder peeling at the bent part was observed.

For the epoxy resin adhesion test, a test piece having a plane dimension of 20 mm × 20 mm was used. The test piece was placed in a mold of a resin injection molding machine, and the temperature was set to 17 with the mold.
After heating at 5 ° C. for 20 minutes, an epoxy resin is blown into this, and a composite piece is formed by adhering an epoxy resin piece having a size of diameter: 15 mm × length: 20 mm to the center of one side surface of the test piece. Atmospheric pressure:
2 atm, temperature: 85 ° C, humidity: 85%, holding time: 24
The pressure cooker test treatment was performed under the condition of time, and then the adhesion strength between the test piece and the epoxy resin piece was measured in the state where the heat treatment was performed under the condition of keeping the temperature at 215 ° C. for 1 minute in the atmosphere. It was performed by measuring. The measurement results are shown in Tables 1 to 3.

[0019]

From the results shown in Tables 1 to 3, the lead frame materials 1 to 11 of the present invention have the same strength (hardness) and conductivity as those of the conventional lead frame materials 1 to 9 which do not contain Sn as an alloy component. , And the heat-resistant peeling property of the solder, it is clear that the adhesiveness with the epoxy resin, which is the encapsulant, is much better than the above, while as seen in the comparative lead frame materials 1 to 7. If the content of any one of the constituent components (marked with * in the table) is out of the scope of the present invention, at least one of the properties of strength, conductivity, and heat-resistant peeling property of solder Is clearly inferior.

As described above, the Cu alloy lead frame material of the present invention can secure a remarkably high adhesion strength with the epoxy resin as the sealing material. In the type semiconductor device, the lead frame material does not peel off from the encapsulating material even when it is used under severe conditions, so that high reliability can be obtained.

Claims (1)

[Claims] 1. By weight%, Ni: 1 to 4%, Si: 0.1 to 1%, Zn: 0.1 to 2%, Mg: 0.001 to 0.0
5%, Sn: 0.05 to 1%, the rest consisting of Cu and inevitable impurities, and the content of sulfur (S) and carbon (C) as inevitable impurities is S: 20 ppm or less, respectively. , C: 20 ppm or less, a Cu alloy lead frame material for a resin-encapsulated semiconductor device, which is composed of a Cu alloy.