JPH02170938A - Copper alloy having superior direct bonding property - Google Patents

Abstract

PURPOSE:To provide a copper alloy for lead frame applicable to all semiconductor products by specifying the surface hardness and the center line average height and maximum height of surface roughness of a copper alloy containing specific amounts of Ni and Sn, respectively. CONSTITUTION:This copper alloy is prepared by regulating the surface of an alloy material having a composition consisting of, by weight, 0.5-10.0% Ni, 0.3-3.0% Sn, and the balance Cu so that surface hardness is >=150 and surface roughness is <=0.15mu by center line average height Ra and <=0.8mu by maximum height Rmax. In the above alloy, high strength and high electric conductivity cannot be obtained when Ni content is below the lower limit, and, when it exceeds the upper limit, workability, direct bonding property, and solderability are deteriorated. As to Sn content, high strength and high electric conductivity cannot be obtained when it is below the lower limit, and, when it exceeds the upper limit, workability and electric conductivity are deteriorated. Further, when the values of the above Hv, Ra, and Rmax are <150, >0.15mu, and >0.8mu, respectively, the adhesive strength of bonding wire is deteriorated and, as a result, there are cases where peeling is brought about in a resin sealing stage, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has good direct bonding properties that enable lead wires for wire bonding to be directly bonded (direct bonding) to copper alloys for lead materials of semiconductor devices. related to copper alloys.

[Prior Art] Conventionally, semiconductor devices have been manufactured by first forming a copper or copper alloy lead material into a predetermined shape by punching or etching, and then molding the bonding portion of the semiconductor element and the semiconductor element and lead material with gold. In order to perform wire bonding with a wire, etc., a predetermined portion of the lead material is plated, then the semiconductor element is die-bonded to the plated part, the semiconductor element and the lead material are wire-bonded using a wire bonding lead wire, and finally, This was sealed and made into a product.

As can be seen, plating is always required to bond the lead material and the semiconductor element and the semiconductor element and the lead material.

However, the plating operation itself requires extremely high precision because it involves plating minute spots, and the quality of the plating directly affects the die bond and wire bond.
In some cases, defective products occurred.

Furthermore, in view of the relationship between the materials of the semiconductor element and the lead material, durability, conductivity, parallelism, etc., plating with gold or silver has been performed, but this has led to extremely high costs for semiconductor devices.

For this reason, attempts have been made to reduce the plating thickness and area, and to use base metals instead of gold and silver, but these efforts have not yielded any groundbreaking results.

Furthermore, a technology has been developed to replace only the die bonding of semiconductor elements with paste and bonding, and plating is no longer necessary when die bonding semiconductor elements, but the wire used to bond the lead material and semiconductor element with gold wire still remains. Plating is required for bonding, and the number of steps has not been reduced at all, so this is not a fundamental solution.

Incidentally, in order to improve direct bonding properties, countless studies have been conducted in the past from the viewpoint of lead frame materials. For example, in Japanese Patent Publication No. 82-46071, the maximum height (Rmax) of the surface roughness of the material must be 0.5 μ■ or less, or the single area of precipitates, inclusions, etc. must be 3×10'■2 or less. It is known that direct bonding properties are improved.

[Problem to be solved by the invention] When the above-mentioned known technology is applied to actual products, the required high reliability IC5LSI and VLSI products are still not at a satisfactory level, and some transistors Currently, it is used for various purposes.

Therefore, there is a need for a copper alloy for lead frames that can be further improved in terms of direct bonding properties and can be applied to all semiconductor products from transistors to VLSI.

[Means for Solving the Problems] The present inventors investigated various material factors that affect direct bonding properties, and found that Rm m It has been found that it is necessary to specify the level of overall surface roughness, such as roughness (Ra). Conventionally, R□ was said to be 0.5 μm or less, but it has been found that even if R exceeds 0.5 μm in some parts, excellent direct bonding properties can be exhibited as long as Ra is below a certain value.

Furthermore, we have found that the hardness of the material must exceed a certain value.

Therefore, in the present invention, Ni0.5 to 10.0% by weight, Sn0
．． The surface hardness of the alloy material is 3° to 3°, including Offfilfilt%, and the balance is Cu and unavoidable impurities.
lv150 or more, and the surface roughness is center line average roughness (
Ra) is 0.15 μm or less, maximum height (R□1) is 0.
A steel alloy with good direct bonding properties, which is characterized in that a lead wire for wire bonding can be directly bonded by adjusting the thickness to 8 μm or less, and Ni 0.5 to 10.0%, Smn 0.
P s A s s S b
SF e s Co, Crs Si, Al, Tis
The material surface of an alloy to which one or more selected from the group consisting of Zr5Mg, BesMn, Zn, In5BSHf, and rare earth elements is added in a total amount of 0.001 to 2.0% by weight has a surface hardness of l1v150 or more and The surface roughness is 0.15 μm or less at the center line (1) and the average roughness (Ra), and the maximum height (
Copper alloy with good direct bondability, characterized in that lead wires for wire bonding can be directly bonded by adjusting the Rmax) to 0.8 μm or less, and a copper alloy with precipitated particles of 5 μm or less in the alloy. The present invention relates to a certain copper alloy with good direct bonding properties and a copper alloy with good direct bonding properties in which the oxygen content is loppm or less.

Next, the reasons for limiting the alloy components and other conditions will be explained. N
The reason why the content of i is set to 0.5 to 10,031fffi% is that when the Ni content is less than 0.5% by weight, Sn is set to 0.3% by weight.
Even if 96% or more of Ni is added, an alloy with high strength and high conductivity cannot be obtained, and on the contrary, the Ni content is io, o! Jlfi%
This is because if it exceeds this, the workability will decrease, and the direct bonding and soldering properties will also decrease.

The reason for setting the Sn content to 0.3 to 3.0% by weight is that Sn
If the Sn content is less than 0.3% by weight, an alloy with high strength and high conductivity cannot be obtained even if 0.5% by weight or more of NL is added, and if the Sn content exceeds 3.0% by weight, processing will be difficult. This is because the properties and conductivity are significantly reduced, and the properties of soldering are also reduced.

As subcomponents, P, As%5bSF'e, Co5Cr,
S 1SAISTiSZn, Mg, Be.

If the total amount of one or more selected from the group consisting of Mn, Zn, In5BSHf, and rare earth elements is less than 0.001% by weight, an alloy with high strength and corrosion resistance cannot be obtained;
This is because if it exceeds 0ffiQ%, the conductivity of low conductivity and semi-Ill conductivity will be significantly reduced.

Also, the reason why the oxygen content was set to 10 ppn+ or more is that 10
This is because if the amount exceeds ppm, the plating adhesion will decrease.

The reason why the amount of precipitated particles is set to be 5 μl or less is that if it exceeds 5 μl, soldering performance and plating adhesion will deteriorate.

The reason why the surface roughness was set to Ilv 150 or more is because Hv15
This is because if it is less than 0, the bonding strength of the bonding wire after direct bonding is low, and peeling may occur during the resin sealing process or the like.

The reason why the surface roughness was set to be 0.15μ or less in center line average roughness (Ra) and 0.8μ or less in maximum height (Rmax) is that in order to obtain a stable and strong contact, it is necessary to This is because it is necessary that the uniformity level is low and that there is no harmful roughness even in parts.

That is, in this alloy system, when Ra exceeds 0.15 μm, the fl' E strength decreases, and even if Ra is 0.15 μm or less, when R1,, exceeds 0.8 μm, the adhesion strength of that part decreases. This is because, as mentioned above, the resin may peel off due to stress in the resin step 11, etc., which impairs reliability.

[Example] The alloy of the present invention shown in Table 1 was made into a plate with a thickness of 0.25 mm by repeatedly hot rolling, cold rolling, and annealing (including solution annealing and aging heat treatment) from an ingot. At this time, differences in surface hardness were created using methods such as rolling after aging heat treatment, further heat treatment, overaging, and solution treatment.

Moreover, the surface roughness was prepared by using rolling rolls with various surface roughnesses, or by surface polishing with various roughnesses after reaching the final plate thickness.

Wire bonding was performed on the various samples manufactured in this manner, and the apparent bonding state was observed, the bonding strength was measured by a pull test, and the fracture location was observed.

Note that wire bonding was performed using the thermosonic method under the bonding conditions shown below.

Bonding wire material and wire diameter = Cu wire 25μ
iφ, Atmosphere: 10 Vo1%H2-Ar, Ultrasonic output crab 0.1WS Substrate temperature: 300℃, Pressure crab 8
0g, time: 25m5ec.

The results are shown in Table 1. As can be seen from this result, the surface hardness is Hv150 or higher and the surface roughness is Ra 0.15.
It can be seen that the bonding performance of conventional plating is improved only when all the conditions of 11 m or more, Rmm, and 0.8 μm or less are met.

Table 1 Note: In the composition of No. 5, "MM" is "Mitsushmetal".

[Effects of the Invention] The present invention provides a copper alloy with a specific component system, by making the surface hardness, surface roughness, etc. within a specific range.
This product has improved direct bonding properties and can be used reliably for IC applications. Moreover, it has extremely high practical value as it eliminates the plating process and reduces the cost to 111 people. be.

Claims (4)

[Claims] (1) Ni0.5-10.0% by weight, Sn0.3-3.
0% by weight, the balance being Cu and unavoidable impurities, the material surface has a surface hardness of Hv150 or more, a center line average roughness (Ra) of 0.15 μm or less, and a maximum height (R_m_a_x ) A copper alloy with good direct bondability, which enables direct bonding of lead wires for wire bonding by adjusting the diameter so that the diameter is 0.8 μm or less. (2) Ni0.5-10.0% by weight, Sn0.3-3.
P, As, Sb, Fe, Co, Cr, Si, Al, Ti, Zr, Mg, B as subcomponents in an alloy consisting of 0% by weight and the balance consisting of Cu and unavoidable impurities.
e, Mn, Zn, In, B, Hf, and one or more selected from the group consisting of rare earth elements in a total amount of 0.001
The material surface of the alloy containing ~2.0% by weight has a surface hardness of H.
v150 or more, and the surface roughness is center line average roughness (R
a) 0.15 μm or less, maximum height (R_m_a_x)
A copper alloy with good direct bondability, which is characterized in that a lead wire for wire bonding can be directly bonded by adjusting the thickness to be 0.8 μm or less. (3) Claim (1) in which the precipitated particles are 5 μm or less
Or the copper alloy described in (2). (4) The copper alloy according to claim (1), (2) or (3), which has an oxygen content of 10 ppm or less.