JPS6267144A - Copper alloy for lead frame - Google Patents

Abstract

PURPOSE:To obtain a copper alloy improved in various characteristics suitable for lead material for semiconductor equipment, particularly in bendability, by specifying respective quantities of Sn, Ni and P and also specifying the range of grain size after final annealing. CONSTITUTION:The copper alloy for lead frame has 10-30mu grain size after final annealing and consists of, by weight, 0,8-4.0% Sn, 0.05-1.0% Ni, 0.01$0.4% P and the balance Cu with inevitable impurities. this copper alloy for lead frame combines high electric conductivity with strength, heat resistance, bendability, solderability and corrosion resistance. Further, this alloy is inexpensive because it is a copper alloy and expensive additive elements are not contained too much and, in addition, it has a coefficient of thermal expansion close to that of seal resin, so that it can be suitably used for plastic package.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object] The present invention relates to a copper alloy suitable as a lead material for semiconductor devices such as transistors and integrated circuits (ICs).

[Prior art and problems]

Conventionally, high nickel alloys such as Kovar (Fe-29Ni-18Go) and 42 alloy have been favorably used as lead materials for semiconductor devices because of their low coefficient of thermal expansion and good adhesion and sealing properties with elements and ceramics. Ta. However, in recent years,
With the increase in the degree of integration of semiconductor circuits, the number of ICs with high power consumption has increased, resins are increasingly used as encapsulating materials, and improvements have been made in adhesion between elements and lead frames. Copper 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) The leads are required to have good electrical conductivity (thermal conductivity) because they are required to act as electrical signal transmission parts and also to release heat generated during the packaging process and circuit use to the outside. Something.

(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 the lead is manufactured by etching or punching the lead material, the workability of these materials must be good.

(5) Many leads are bent. Also, since it is a structure that supports semiconductor components, it must be strong and have good bending workability.

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

(7) 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 be resistant to peeling over time during use.

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

(9) The price is paper storage.

In response to these various required properties, the oxygen-free copper, tin-containing copper, phosphor bronze, Kovar, and 42 alloys that have been used conventionally all have advantages and disadvantages, and cannot satisfy all of these properties.

[Structure of the invention]

The present invention has been made in view of the above, and aims to improve the drawbacks of conventional copper alloys and provide a copper alloy with improved thin adhesion properties, particularly bendability, suitable as a lead material for semiconductor devices.

That is, the present invention uses Sn0.8-4.0% in weight% whose grain size after final annealing is more than 10μ and less than 30μ.
Copper alloy for lead frame consisting of Ni 0.05-1.0%, PO001-0.4%, balance Cu and unavoidable impurities, and the crystal grain size after annealing before final annealing is more than 10 μ and 30 μ or less The copper alloy for lead frames described above, and the crystal grain size after final annealing exceeding 10μ,
Sn 0.8-4.0%, Ni in weight% less than μ
As, Cr, Mg, Mn, Sb, Fe, C01A1 as subcomponents in 0.05-1.0%, P0.01-0.4%
, Ti, Zr, Be, and Zn in a total amount of 0. o o i~1. Copper alloy for lead frames consisting of Owt, %, balance Cu and unavoidable impurities, and crystal grain size after annealing before final annealing exceeding 10μ, 30
The copper alloy for lead frames described above has a particle diameter of μ or less.

[Detailed description of the invention]

Next, the alloy components and crystal grain size of the copper alloy constituting the present invention will be explained. Sn content in weight% from 0.8 to 4.0
% is because if the Sn content is less than 0.8%, the expected strength as a lead frame material cannot be obtained even with the co-addition of other components; This is because if it exceeds the range, the conductivity will decrease and problems will arise in the heat dissipation properties of the lead frame material. Ni content 0.05-1.0%
The reason for this is that if the Ni content is less than 0.05%, no strength improvement can be obtained by adding Ni;
The reason why the 6P content is set to 0.01 to 0.4% is that the conductivity decreases when the P content exceeds 0.01%.
This is because if the P content is less than 0.4%, no improvement in strength or heat resistance can be obtained by adding P, and conversely, if the P content exceeds 0.4%, the electrical conductivity and workability will decrease.

Furthermore, the reason why the content of the subcomponent is set to 0.01 to 1.0% is that if the content of the subcomponent is less than 0.01%, no strength improvement can be obtained by adding the subcomponent; is 1.0
This is because if it exceeds %, the conductivity will drop significantly.

Next, the reason why the grain size after final annealing or after final annealing and after annealing before final annealing should be more than 10μ and less than 30μ is that if it is less than 10μ, the bendability of the material will be poor, and if it exceeds 30μ, the expected strength of the material will be reduced. 9. Final annealing means recrystallization annealing, and low-temperature strain relief annealing that does not involve recrystallization is not included in final annealing.

Therefore, alloys corresponding to the present invention which are subjected to strain relief annealing after final annealing are naturally included in the present invention.

〔effect〕

Thus, according to the present invention, a copper alloy for lead frames is obtained which is highly conductive and has excellent strength, heat resistance, bending workability, solderability, and corrosion resistance. Furthermore, since it is a copper alloy and does not contain large amounts of expensive additive elements, it is inexpensive, and its coefficient of thermal expansion is close to that of sealing resin, making it suitable for plastic packages. No prior art alloy possesses such comprehensive properties.

Next, the method of the present invention will be explained using examples.

〔Example〕

Ingots having the chemical compositions shown in Table 1 were produced by ordinary atmospheric melting casting. After the surface of this ingot was ground, it was heat-treated at 650°C for 4 hours in a non-oxidizing atmosphere. Further, after being cold rolled to form a plate with a thickness of 4 strokes, the same heat treatment as above was performed, and a plate with a thickness of 1.5 m was obtained by cold rolling.

After annealing this plate under various heat treatment conditions and pickling,
A plate with a thickness of 0.4 m was obtained by cold rolling.

After further annealing and pickling under various heat treatment conditions,
A plate having a thickness of 0.2511I11 was produced by final cold rolling. Thereafter, strain relief annealing was performed at 250°C for 3 hours. During the above heat treatment process, plates with various grain sizes were produced by controlling the annealing temperature and annealing time. Comparative alloys were also produced using various manufacturing processes.

To evaluate the sample prepared in this way as a lead material, the strength and elongation were measured by a tensile test, the heat resistance was measured by the softening temperature at a heating time of 5 minutes, and the electrical conductivity (heat dissipation) was measured by the conductivity (%IAC8). ). This is because electrical conductivity and thermal conductivity are proportional to each other and can be evaluated by electrical conductivity.

Soldering is done using the vertical immersion method in a solder bath at 230±5℃ (
(Sn 60%, Pb 40%) Dip for 5 seconds and visually check the state of solder wetting. The evaluation was made by observing the results. The bendability was evaluated by repeatedly bending a test piece of t×10w×Q (lIIl1) at 90° in the direction parallel to rolling and in the perpendicular direction with the same bending radius as the plate thickness, and the number of times until breakage occurred.

As shown in Table 1, the alloy of the present invention has excellent strength, electrical conductivity,
It exhibits heat resistance and solderability, and since it is a copper alloy, it is inexpensive and has a thermal expansion coefficient close to that of resin as a sealing material, making it suitable as a lead frame material for semiconductor devices that satisfies all characteristics. It can be said that it is a material.

Margin below

Claims (1)

[Scope of Claims] 1) Sn 0.8 to 4.0% and Ni 0.05 to 1 in weight percent whose grain size after final annealing is more than 10μ and less than 30μ.
．． A copper alloy for lead frames consisting of 0% P, 0.01 to 0.4% P, and the balance Cu and inevitable impurities. 2) The grain size after annealing before final annealing exceeds 10 μ3
The copper alloy for lead frames according to claim 1, which has a particle diameter of 0μ or less. 3) Sn 0.8-4.0%, Ni 0.05-4.0% by weight where the grain size after final annealing is more than 10μ and less than 30μ
1.0%, P0.01-0.4% with As as a subcomponent,
Cr, Mg, Mn, Sb, Fe, Co, Al, Ti, Z
The total amount of one or more of r, Be, and Zn is 0.0
01~1.0wt. Copper alloy for lead frames consisting of % Cu and unavoidable impurities. 4) The grain size after annealing before final annealing exceeds 10 μ3
The copper alloy for lead frames according to claim 3, which has a particle diameter of 0μ or less.