JPS60128234A - Copper alloy for lead frame - Google Patents

Abstract

PURPOSE:To obtain the titled Cu alloy exceeding considerably a conventional Cu alloy in strength and heat resistance and having satisfactory adhesive strength to plating and solderability by adding prescribed amounts of Ni, Al, Si and Sn to Cu. CONSTITUTION:This Cu alloy for a lead frame consists of, by weight, 0.5-5.0% Ni, 0.5-5.0% Al, 0.05-2% Si, <=4% Sn and the balance Cu. Intermetallic compounds such as NixAly, NixSiy and NixSny are finely precipitated in Cu as the base of the Cu alloy, and Ni, Al, Si and Sn are solubilized in the base, so the Cu base is strengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION The alloy of the present invention relates to a steel alloy for lead frames of devices such as ICX LSIs that use semiconductors as an element, and particularly to a copper alloy having excellent heat resistance, bending workability, and mesh adhesion.

In general, devices such as iC, LS, and T that use semiconductors as elements are all composed of semiconductor pellets, leads, and ponting wires, which are sealed using methi, kusol, and ceramic seal technologies. Various types are used.

Conventionally, lead frames for these devices were made of iron.
2.Kovar (Fe-29 to %Ni-17C0 alloy), lI2 alloy, Kovar≠4 as Kel system moon phase
Clad material coated with gold, Clad material coated with A9 on iron-nickel alloy, Phosphor bronze as copper alloy, C1940
○(Cu-Fe-Zn-P alloy containing 19500 (C:u
-Fe-co-Sn-P alloy), C14410 ((Eu
=Sn-P alloy) etc. are used. However, although the above iron-nickel materials have excellent heat resistance and strength,
Since they are expensive, have poor conductivity, and have poor workability, copper-based alloys that are low in cost and have good workability, plating adhesion, and solderability have recently become mainstream. However, copper alloys such as those mentioned above have heat resistance, electrical (thermal/) properties,
Because of its poor bendability, it was unable to exhibit sufficient properties as a lead frame material. Especially in recent years, where high density and high degree of integration are strongly required, there is a need for material f-1 that has high conductivity, strength, bendability, heat resistance, and surface quality that makes it easy to plate. It has become. In other words, ■High reliability ■Economic efficiency ■Thermal performance are the requirements for modern lead frame manufacturing.

The surface quality that is easily plated is semiconductor Pelle.

Plating with gold, silver, nickel, tin, etc. is performed to improve the connectivity between the lead frame and the bonding wire, as well as between the bonding wire and the lead frame, and to improve and maintain the oxidation resistance, corrosion resistance, solderability, etc. of the lead frame. Due to its excellent adhesion, this type of plating process accounts for a large proportion of the processing cost for products such as lead frames, and has a large impact on quality reliability.゛Iron-nickel materials such as Kovar and 42 alloy are conductive,
Not only does it have poor thermal conductivity, but plating is difficult and requires special ingenuity. For example, the surface of these base materials is plated with a nickel layer and a 5n-Ni alloy layer in sequence, or the surface of the base material is plated with a cyan alkaline plating solution containing silver and copper, and the surface is plated. . Generally, there is a strong demand for a material that satisfies the following six items as a copper alloy for use in lead frames.

(1) Good electrical and thermal conductivity.

(2) Good heat resistance.

(3) Good bending workability.

(ii) High strength.

(5) Good plating adhesion.

(6) Good solderability.

In view of this, as a result of various research, the present invention has developed a copper alloy for lead frames of semiconductor devices that has better heat resistance and bending workability than conventional copper alloys for lead frames, and has sufficient strength and plating adhesion. NiO05'-5,Ow
t% (hereinafter abbreviated as Chi) AAO, 5-5.0%, SiO
, 05 to 2%, 5nl1% or less, and the remainder is Cu. That is, the alloy of the present invention uses Gu as a base material, N1,
It adds Ag, Si, and Sn.l) N1XA
j! L) Intermetallic compounds such as Nix 51f
'J1% Aimed at strengthening the base material by solid solution of JSL and Sn, it has strength and heat resistance exceeding conventional wisdom as a copper alloy, and has good plating adhesion and solderability. A copper alloy for lead frames having the following properties was obtained. In addition, the alloy of the present invention can be used not only for ordinary pure copper such as electrolytic copper or oxygen-free copper, but also for phosphorus-deoxidized copper as a raw material for CD, and even if a small amount of P remains, an alloy with almost the same properties can be obtained. It will be done.

//'iNi 0.5chi, /u0.5chi, Si 0.0
If it is less than 5%, the required strength and heat resistance cannot be obtained, and Ni
If it exceeds 5.0%, Ag5.0%, Si2%, Sn4%, excellent performance in strength and heat resistance can be obtained, but it does not mean that bending workability deteriorates, but also plating adhesion and solderability. This is because it deteriorates.

The alloy of the present invention will be explained below using examples.

After melting Cu using a graphite melt, covering the surface of the hot water with charcoal powder and thoroughly melting it, Ni, Sn, and Si are dissolved.

Adding Ag in this order and casting it gives the composition range 1 shown in Table 1.
An ingot with a length of 50 mm, a length of 200 mm, and a thickness of 25 mm was obtained.

Next, the surface of this ingot was milled 25 times per side, and then hot rolled to form a plate with a width of 150 mm and a thickness of 8 mm.
Thereafter, this plate was repeatedly cold-rolled and annealed at a final rolling reduction of 11 oz to obtain a cold-rolled phase having a thickness of 0.3 m. The bending workability, electrical conductivity, tensile strength, heat resistance, plating adhesion, and solderability of these plates were measured. These results are shown in Table 1. For comparison, similar measurements were performed on conventional lead frame alloys, and the results are also listed in Table 1.

For bending workability, cut strips of 5mm in width and 50mm in length from the plate material, perform 1800 degrees of tight bending at the center, and observe the surface condition of the bent part to ensure that no cracks or wrinkles occur. Marked with ○ because it has good bending properties for smooth objects.
Those with obvious cracks are marked as having poor bending workability and are marked with an X mark, while those with slight cracks or wrinkles in between are marked with a Δ mark.

Measurement of electrical conductivity and tensile strength 1-i JIS-HO5
05 and JIS-22241.

Plating adhesion was determined using the same methods as the lead frame plating process for the dull material of the plate: alkaline degreasing (1 minute), etching with 20 nitric acid (30 seconds), heating at 150°C (5 minutes).
Heating at 550°C for 5 minutes shows no blistering at 550°C for 5 minutes, and indicates no blistering when heated at 050°C for 5 minutes, but swelling occurs when heated at 550°C for 5 minutes. The resulting product is marked with a mu, and the product that has already blistered after heating at 150°C for 5 minutes is marked with an x.

5n at 230°C by vertical immersion method
-) Observe the surface of the object immersed in the I0%pb eutectic semi-1-F1 bath for 10 seconds. As a result, those with smooth surfaces are marked with ○, those with slight irregularities on the surface are marked with △, and the surfaces with irregularities are marked. The parts where the solder has not formed are marked with an X.

For +l+iJ thermal properties, a tensile test piece specified in JIS-22201 was cut out from the above-mentioned rolling process, and after annealing it at 1000°C for 5 minutes in an alcohol gas atmosphere, a tensile test was conducted and the tensile strength was compared with that before annealing. Those in which the rate of decrease in strength was 30 o/) or less were deemed to have good heat resistance and were marked with a circle, and those in which the rate of decrease in strength exceeded 50% were marked as poor in heat resistance and were marked with an x.

As is clear from Table 1, the alloy of the present invention, NIL L~14, has an electrical conductivity of 13~63%■Acs and a tensile strength of 55~? 9
It exhibits the characteristics of Kq f /-, has good bending workability and heat resistance, and has electrical conductivity comparable to Cu-Fe-Zn-P alloy and far superior tensile strength and heat resistance. I know that there is. In addition, plating adhesion, solder U items are also Cu
It can be seen that it is sufficiently superior to the -Fe-Zn-P alloy.

On the other hand, the comparative alloy N115, which has less N1, has insufficient tensile strength and heat resistance, and is slightly inferior in bending workability.
Comparative alloy Nα16, which contains a large amount of Ni, not only has low conductivity, but also has poor processability and poor plating adhesion and semi-FI properties. AI! The comparative alloy Nα17, which has a low amount of Ae, has insufficient tensile strength and +AiJ thermal properties, and the comparative alloy Nα18, which has a large amount of Ae, has low conductivity, poor bending workability, and poor plating adhesion and semi-1:TI ( ing.

The low Sl ratio+liQ alloy No. 19 does not have sufficient heat resistance, and the comparative alloy Nα20 with a high Sl ratio not only has poor bending workability, but also has insufficient plating adhesion, tensile strength, and heat resistance. Comparative alloy N with more N1 and jV
Although α22 has low conductivity, it does not require much force, has poor bending workability, and has poor plating adhesion and solderability. AQ and 81
The comparative alloy Nu 25 with less AA and 81 has insufficient tensile strength and heat resistance (the comparative alloy Nα21I with more AA and 81 not only has low conductivity but also poor bending workability, poor plating adhesion and solderability). Comparative alloy Hi025, which has less $1 and N1, does not have sufficient resistance to resistance, and comparative alloy NCL26, which has more $1 and N1, not only has low conductivity, but also has low conductivity.
The bending workability is poor, and the plating adhesion and solderability are also poor.

Comparative alloy Nα27, which contains a large amount of Sn, not only has low conductivity, but also poor bending workability, and poor plating adhesion and solderability.

Claims (1)

[Claims] N105~5.0 wt%, AQO5~5.0 wt%
, 0.05 to 2 wt % of Si, and 0.05 to 2 wt % of Sn, with the balance being Cu.