JPS63125628A - Copper alloy for semiconductor device lead material - Google Patents

Abstract

PURPOSE:To obtain a copper alloy for semiconductor device lead material excellent in solderability, adhesive strength of plating, and etching characteristic, by specifying a composition consisting of Cr, Si, and Cu and also by controlling the size of a precipitate. CONSTITUTION:The copper alloy for semiconductor device lead material has a composition consisting of, by weight, 0.05-1.0% Cr, 0.02-0.8% Si, and the balance essentially Cu and further containing, if necessary, 0.01-1% of one or more elements among Zn, Mg, P, Sn, Fe, Be, Ti, Hf, Co, and In and also has a structure in which size of a precipitate is regulated to <=1.0mum. This copper alloy is excellent in strength, electric conductivity and heat resistance and further has superior workability, etc. The size of the above precipitate is controlled by properly selecting a combination of solution heat treating, cold working, and age treating conditions.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a copper alloy for lead materials of semiconductor devices such as transistors and integrated circuits (ICs), particularly a Cu-based alloy with improved plating adhesion and etching properties. This relates to Qr-3i alloys.

[Prior art] Conventionally, lead materials for semiconductor devices have a low coefficient of thermal expansion and good contact and sealing properties with elements and ceramics.]
High nickel alloys such as Var (Fe-29N 1-16CO), 42 alloy have been preferred. but,
In recent years, as semiconductor circuits have become more integrated, many ICs with high power consumption have come into use, resins have been increasingly used as sealing materials, and bonding between elements and lead frames has also improved. As a result, copper-based alloys with good heat dissipation properties have come to be used as lead materials.

[Problems to be Solved by the Invention] Generally, lead materials for semiconductor devices are required to have the following characteristics.

(1) Since the lead is required to act as an electrical signal transmission part and also have the function of releasing heat generated during the packaging process and circuit use to the outside, it must have excellent thermal and electrical conductivity. Something to show.

(2) Adhesion between the lead and the mold is unnecessary from the perspective of protecting the semiconductor element, so the thermal expansion coefficients of the lead material and the mold 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) Excellent etching processability.

(6) Since the surface of the lead is plated with precious metals, the lead should have good plating adhesion to these precious metals.

(7) Exposed outside the sealing material after packaging;
Since many items are soldered to the outer leads, they must exhibit good solderability and have good peeling resistance against changes over time during use.

(8) Good corrosion resistance from the viewpoint of equipment reliability and lifespan.

(9) The price is low.

Oxygen-free copper, tin-containing copper, phosphor bronze, ]Var, and 42 alloys that have been conventionally used to meet these various required properties all have advantages and disadvantages, and cannot necessarily satisfy all of these properties. do not have.

On the other hand, although the Cu-Cr-3i alloy satisfies the above characteristics to a large extent, it has poor soldering properties due to the size of the precipitates.
Since there is a large difference in plating adhesion or etching workability, it is essential to specify the size of the precipitates in copper alloys for lead frame materials.

Therefore, the present invention solves these problems and provides a copper alloy for lead material that has excellent soldering properties, plating adhesion, and etching properties, as well as excellent opening properties. The purpose is to

[Means for solving the problems] The present invention provides the following as means for solving the problems described above.
Configure as below.

That is, in the first aspect of the present invention, Cr is 0.05 wt% or more and 1.0 wt% or less, and 0.02 wt% or more is 0.
．． This is a copper alloy for a lead material of a semiconductor device, which is characterized by containing 8 wt% or less of 3i, the remainder being substantially Cu, and having a precipitate size of 1.0 μm or less. Similarly, the second invention is 0.05 wt% or more and 1.0 wt%
The following Cr, 0.02 wt% or more and 0.8 wt% or less Si, and Zn, Mg, P, Sn, Fe5Be, T
i, l-1fSCo, one or more elements selected from the group consisting of In, singly or in combination, 0.01
Contains i at wt% or more, owt% or less, and the balance is substantially C.
This is a copper alloy for lead material of semiconductor devices, characterized in that the size of the precipitates is 1.0 μm or less.

Next, the reasons for limiting the alloy components constituting both the alloys of the present invention (1) and (2) will be explained. Cr content 0.05wt
% to 1.0 wt% or less is because if the Cr content is less than 0.05 wt%, the expected strength and heat resistance will not be obtained, and if it exceeds 1.0 wt%, the electrical conductivity will decrease. decreases,
Furthermore, the plating properties (blistering of the plating due to heating) and peeling resistance of the solder deteriorate.The content of 3i is reduced to 0.
The reason why the content of 3i is set to 0.02 wt% or more and 0.8 wt% or less is that if the 3i content is less than 0.02 wt%, the expected strength and heat resistance cannot be obtained even if Or is co-added, and if it exceeds O or awt%. This is because, in relation to the content of other additive elements, the amount of 3i that does not form an intermetallic compound and is solidly dissolved in CLI increases, resulting in a decrease in electrical conductivity. Furthermore, Zn, IVF, P, Sn, Fe1
The reason for adding one or more elements selected from the group consisting of Be, Ti5Hf, Co, and In is that these additions improve strength and heat resistance without significantly reducing conductivity. Among these, 7n, Mg, and In have the effect of improving oxide film adhesion and solder peeling resistance, and their content alone or in combination is 0.01 wt% or more. Owt
% or less because if it is less than 0.01 wt %, the above-mentioned effect cannot be expected, and if it exceeds 1.0 wt %, the conductivity will drop significantly. In addition, the size of the precipitates was reduced to 1.0 μm.
Jy, the reason for lowering is that by precipitating fine grains of 1.0 μm or less in Cu, an alloy with good strength, conductivity, solderability, plating adhesion, etching property, etc. can be obtained. .

That is, when the size of the precipitates exceeds 1.0 μm, the strength and conductivity begin to decrease. Furthermore, when soldering or plating is applied, the wettability of the precipitates is poor, making it difficult for normal solder and plating to adhere to the precipitates, and the adhesion of the plating to the product is also rapidly reduced. As for etching properties, the corrosion rate differs between the matrix and the precipitates, so if the size of the precipitates exceeds 1.0 μm, the etching properties drop sharply, leaving paris-like precipitates on the etched surface, which can be used as lead material. A phenomenon occurs in which the predetermined dimensions of the object are not met. Therefore, in the Cu-Cr-3i alloy, the size of the precipitates is reduced to 1
．． Unless the thickness is 0 μm or less, the alloy cannot be used for practical use.

The size of the precipitates can be reduced to 1.0 μm or less by selecting a combination of solution treatment, cold working T, and aging treatment conditions.

[Example] Alloy ingots having various component compositions according to the present invention (1) and (2) not shown in Table 1 were melted in the atmosphere, or inert or reducible, using electrolytic copper or oxygen-free copper as raw materials in a high-frequency melting furnace. Melted and cast in an atmosphere. Next, this was heated at 850'C for 1 hour and hot rolled to form a plate with a thickness of 8 mm.The rear side was then cold rolled to form a plate with a thickness of 2.5 mm. This 2.
A 5 mm plate was solution treated at 950°C for 1 hour, water quenched, cold rolled into a 0.25 mm thick plate, and finally aged under various conditions. The size of the precipitates in the sample material thus obtained was confirmed, and its use as a lead material was evaluated in the following manner.

Strength and elongation are determined by tensile tests, and bendability is determined by bending in the direction parallel to the rolling direction of the plate (〃), bending in the direction perpendicular to the same (for earth), bending with the same thickness as the plate under a constant load (225qf). Heat resistance is determined by the softening temperature at a heating time of 5 minutes, and electrical conductivity and heat dissipation are determined by repeated bending at R (0.25 mm) (the number of 90° bending cycles that can be bent without breaking). (%■△C8
This is because electrical conductivity and thermal conductivity are in a proportional relationship with each other, and both can be evaluated by electrical conductivity. Soldering is done by vertical dipping method at 230±5℃.
The solder was immersed in a solder bath (60% Sn, 40% Pb) for 5 seconds, and the wetting state of the solder was evaluated by visually observing it.

The peeling resistance of the solder was evaluated by heating a sample soldered by the above method in the air at 150° C. for 11,500 hours, then bending it at 90° with a bending radius (0.25 mm) equal to the thickness of the plate, and evaluating the presence or absence of peeling. Etching properties were evaluated by etching the sample material with ferric chloride and checking the presence or absence of Paris-like protrusions on the cross section.

Adhesion was evaluated by applying Ag plating with a thickness of 3 μm to the sample and visually observing the presence or absence of blisters on the surface. Oxide film adhesion was determined by heating the sample at 400'C for 1 minute, cutting grids at 2 mm intervals on the sample surface with a knife, applying adhesive tape, and peeling it off from the sample. The gender was evaluated. These results are shown in Table 1, including comparative alloys.

As shown in Table 1, the alloy of the present invention has excellent strength, bendability, electrical conductivity, heat resistance, solderability, solder peeling resistance, etching property, plating adhesion, and oxide film adhesion. This is obvious, and it can be said that it is suitable for use as a bonding shrine for semiconductor devices.

[Effects of the Invention] The copper alloys according to the present invention (1) and (2) have excellent strength, electrical conductivity, and heat resistance, and can be punched and bent, yet have moderately good strength and In addition to exhibiting mechanical properties such as elongation, it also has good solderability, plating adhesion, etching resistance, corrosion resistance, etc.

In addition, when using copper alloy for lead frame material, the key point is to maintain low reliability! On the other hand, the solder removability and oxide film adhesion, which are important technical items, are good. Historically, its coefficient of thermal expansion is close to that of plastic, making it suitable for use in solid packaging.

None of the prior art alloys of d3 have such an overall temporality.

Claims (2)

[Claims] (1) Cr: 0.05-1.0% by weight and Si: 0.0
A copper alloy for a lead material of a semiconductor device, characterized in that the copper alloy contains 2 to 0.8% by weight, the remainder is substantially Cu, and the size of precipitates is 1.0 μm or less. (2) Cr: 0.05-1.0% by weight, Si: 0.02
~0.8% by weight and Zn, Mg, P, Sn, Fe, Be
, Ti, Hf, Co, In.
0.01 to 1 of a species or two or more elements alone or in combination
1. A copper alloy for a lead material of a semiconductor device, characterized in that the balance is substantially Cu and the size of precipitates is 1.0 μm or less.