JPH01268834A - Copper alloy for lead material of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture the title copper alloy having excellent strength, electric conductivity, heat resistance, etc., by incorporating specific ratios of Zn and Sn to Cu. CONSTITUTION:A Cu-Zn alloy contg., by weight, 2.0-7.0% Zn and 0.05-0.8% Sn, if required, contg. total 0.01-1.0% of one or more kinds selected from the group of P, B, Al, Fe, Cr, Co, Ni, Mn, Si, Mg, Be, Ti, Zr, In, Te, Y and rear earth elements and the balance consisting of Cu with inevitable impurities is prepd. By this method, the alloy having excellent electric and heat conductivity, heat resistance, workability, plating adhesion, solderability, corrosion resistance, etc., as a copper alloy for a lead material of a semiconductor device can be obtd. at low cost.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a copper alloy for lead material of semiconductor devices such as transistors and integrated circuits (ICs). This invention relates to a material that has been improved for use as a lead material.

[Prior art] Conventionally, high nickel alloys such as Kovar (re-29N+-18co) and 42 gold, which have a low coefficient of thermal expansion and good adhesion and sealing properties with elements and ceramics, have been used as lead materials for semiconductor devices. It has been liked and used. However, in recent years,
Due to the increase in the number of ICs with high power consumption due to the improvement in the degree of integration of semiconductor circuits, the increased use of resin as a sealing material, and improvements in the bonding between elements and lead frames, Copper-based alloys with good heat dissipation are now being used as lead materials.

Generally, lead materials for semiconductor devices are required to have the following properties.

(1) Leads must exhibit excellent thermal and electrical conductivity, as they are required to act as an electrical signal transmission unit and also have the function of discharging heat generated during the unpacking process and during use of the circuit to the outside. .

(2) Since the adhesion between the lead and the mold is important from the perspective of protecting the semiconductor element, the thermal expansion coefficients of the lead material and the mold material are close, and the adhesion of the oxide film formed on the surface of the lead is good. thing.

(3) It must have good heat resistance since various heating processes are involved during packaging.

(4) Since most leads are manufactured by punching and bending lead material, the workability of these materials must be good.

(5) Since the surface of the lead is plated with precious metals, the plating adhesion to these precious metals must be good.

(6) exposed outside the sealing material after packaging;
Since many items are soldered to the outer leads, good soldering should not only show good soldering properties but also have peeling resistance against changes over time during use.

(7) Good corrosion resistance from the standpoint of equipment reliability and lifespan.

(8) The price must be low.

In response to these various required properties, the oxygen-free copper, tin-containing copper, phosphor bronze, Kovar, and 42 alloys that have been conventionally used all have advantages and disadvantages, and cannot necessarily satisfy all of these properties. . In addition, many new alloys have been proposed in recent years, and although attempts have been made to improve various properties, none have been improved, including in terms of lower prices.

[Problems to be Solved by the Invention] From the viewpoint of cost, copper alloys containing a large amount of Zn, such as brass and red copper, are the best, but they are highly susceptible to stress corrosion cracking, which poses a practical problem. In order to reduce the price of materials, it is necessary to select inexpensive metals as alloying elements, and it is also necessary that special manufacturing processes such as solution treatment and aging treatment are not required, and that the material has good workability. It is.

The present invention has been made in view of this point, and is based on the conventional Cu-
The object of the present invention is to provide a copper alloy that improves the defect of stress corrosion cracking of Zn alloys, has various properties suitable as a copper alloy for lead materials of semiconductor devices, and is inexpensive.

[Means for Solving the Problems] The present invention contains 2.0 to 7.0% by weight of Zn and 0.0% by weight of Sn.
05 to 0.8% by weight, balance consisting of Cu and unavoidable impurities, and Zn 2.0 to 7.0% by weight, Sn0
．． 05-0.8 ffl 96 and P, B, AI, Fe
.

C", C01N i, Mn, s i, Mg5Be.

One or more selected from the group consisting of Ti, Zr, In5TeSY, and rare earth elements in a total amount of 0.01-1
．． It is an alloy containing 0% by weight and the balance consisting of Cu and unavoidable impurities, and has excellent electrical and thermal conductivity, heat resistance, workability, plating adhesion, and solderability as a copper alloy for lead materials of semiconductor devices. It is an inexpensive alloy that has excellent corrosion resistance.

(Detailed Description of the Invention) Next, the reasons for limiting the alloy components constituting the alloy of the present invention will be explained. . The reason for setting the Zn content to 2.0 to 7.0% by weight is that if the Zn content is less than 2.0'ff1m%, the expected strength and heat resistance cannot be obtained even if Sn and other additive elements are added. This is because if it exceeds 7.0 fIrffi%, the electrical conductivity decreases and the stress corrosion cracking susceptibility increases rapidly. The Sn content is set to 0.05 to Q, 3 mm% because if the Sn content is less than 0.05% by weight, the expected strength and heat resistance cannot be obtained even if Zn is used. This is because if it exceeds 8% by weight, the conductivity will decrease and the price will also increase. Furthermore, P, B, Al5Fe.

C', Co SN l s M n s S is M
g % B e −.

The reason for adding 1g1 or 2Ff1 or more selected from the group consisting of Ti5ZrS In, Te5Y, and rare earth elements is to improve the strength and heat resistance without significantly reducing the electrical conductivity. Among them, B, Mg
, Y, and rare earth elements also have the effect of improving oxide film adhesion. The reason why the total content is set to 0.01 to 1.0 mm% is that if it is less than 0.0% by weight, the above-mentioned effect cannot be expected.
This is because if it exceeds 1.0 mm%, the electrical conductivity will drop significantly.

[Example] The present invention will be explained below with reference to examples.

Ingots having various component compositions of the alloy of the present invention shown in the table were melted and cast using electric or oxygen-free copper as a raw material in a high-frequency melting furnace in air, an inert atmosphere, or a reducing atmosphere.

Next, this was heated at 800°C for 1 hour, hot rolled into a plate with a thickness of 8cm, then the face side was processed and cold rolled to a thickness of 1cm.
．． It was made into a 5-inch board. 500 pieces of this 1.5mm thick plate
After annealing for 1 hour at °C, cold rolling was performed to 0.51, and after further annealing, cold rolling was performed to OJO■.

To evaluate the sample prepared in this way as a lead material, the strength and elongation were measured by tensile tests, and the bendability was measured by repeated 90'' reciprocating bending (until breakage) at the same bending radius as the plate thickness (= 0.30 nv). The heat resistance was shown by the softening temperature at a heating time of 5 minutes, and the electrical conductivity (heat dissipation) was shown by the conductivity (%IACS).Electrical conductivity and thermal conductivity are in a proportional relationship with each other. This is because it can be evaluated by electrical conductivity.Solderability is 230% by vertical dipping method.
It was immersed in a solder bath (Sn 130%, PB 40%) at ±5° C. for 5 seconds, and the state of solder wetting was evaluated by visually observing it. The peeling resistance of the solder was 0.3 after heating the sample soldered by the above method at 150°C in the air for 1500 hours.
A 90° bend of 5R was performed and 6 no peeling was planned. Plating adhesion was evaluated by applying Ag plating to a thickness of 3 μm to a sample and visually observing the presence or absence of blisters occurring on the surface. Oxide film adhesion is determined by heating the sample at 400°C for 1 minute, making incisions on the material surface with a grid knife at 21 intervals, applying adhesive tape, peeling it off from the material, and determining whether there is an oxide film attached to the tape. The gender was evaluated.

The stress corrosion cracking susceptibility was 9 when the sample was bent at a bending radius of 0.35 mm.
The sample was bent by 0" and left in a desiccator containing ammonia diluted twice with water for 72 hours, and the presence or absence of cracks was observed.

In addition, price was evaluated based on two points: alloy raw material cost and whether special processes such as aging treatment were required. These results are shown in the table along with comparative alloys.

As shown in the table, the alloy of the present invention exhibits excellent strength, bendability, conductivity, heat resistance, solderability, solder peeling resistance, plating adhesion, oxide film adhesion, and stress corrosion cracking resistance. It is also clear that it is inexpensive, and it can be said that it is a suitable material as a general-purpose material for lead materials of semiconductor devices, etc.

[Effects of the Invention] The alloy of the present invention has excellent strength, electrical conductivity, and heat resistance, and exhibits moderately good mechanical properties such as strength and elongation for punching and bending, and is easy to solder. It is a copper alloy with good plating adhesion and corrosion resistance. In addition, solder peeling resistance, which is an important technical item in order to avoid deteriorating reliability, which is a key point when making copper alloys for lead frames,
A copper alloy with good oxide film adhesion.

In addition, its coefficient of thermal expansion is close to that of plastic, making it suitable for plastic packaging. Furthermore, it is an inexpensive alloy containing 3 white Zn, and is suitable as a lead material for general-purpose semiconductor devices. No prior art alloy has this combination of overall properties.

Patent applicant [Ippon Mining Co., Ltd. Agent Patent Attorney Hidetake Komatsu

Claims (2)

[Claims] (1) A copper alloy for a lead material of a semiconductor device, characterized by comprising 2.0 to 7.0% by weight of Zn, 0.05 to 0.8% by weight of Sn, and the balance being Cu and unavoidable impurities. (2) Zn2.0-7.0% by weight Sn0.05-0.8% by weight and P, B, Al, Fe, Cr, Co, Ni, Mn, S
Contains one or more selected from the group consisting of i, Mg, Be, Ti, Zr, In, Te, Y, and rare earth elements in a total amount of 0.01 to 1.0% by weight, with the balance being Cu and unavoidable elements. A copper alloy for lead material of semiconductor devices characterized by containing impurities.