JPS605550A - Electronic parts - Google Patents

Abstract

PURPOSE:To obtain an alloy composition adapted for a lead frame and lead wirings having less production intermetallic compound having weak bonding strength at the bonding to a solder by containing Zn as the third additive to Ni or Fe and Sn. CONSTITUTION:When an alloy which contains 0.05-5wt% of Ni or Fe, 0.05-4 wt% of Zn and the residue of Cu is used for an Sn solder electronic part, a preferable result can be obtained. When Ni, Sn and Zn are used as the additives of the alloy, the relationship of Zn >=1/20 (Ni, Sn) by weight to Ni (or Fe) and Sn to Zn is preferable in addition to the above condition. Part of Ni may be replaced by Fe. In this case, the relationship of Zn >=1/20 (Ni, Fe, Sn) is preferably satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to electronic components, and more particularly to electronic components suitable for use in consumer products.

[Technical background of the invention and its problems]

Consumer products, such as semiconductor devices, are required to have high output and multifunctionality, and these products also require high productivity and low cost.

Various developments are underway to fully satisfy these conditions. Among these, resin molds and the like are effective in meeting the above requirements, but these also have the following drawbacks, and their development is required.

That is, there are unavoidable mounting steps in the manufacturing process, bonding steps between semiconductor elements and lead wires, and the lead frame, which is the lead element used in these steps, is an important component. If this lead frame satisfies the following severe conditions, it is extremely advantageous in terms of manufacturing process, cost, and characteristics. In other words, it must have low electrical resistance, little surface oxidation, high tensile strength, sufficient ductility and resistance to bending, high-temperature properties such as sufficient mechanical strength at temperatures above 250°C, and wettability with solder. These include sufficient durability and weather resistance.

Although it is difficult to obtain a material that satisfies all of these various conditions, it is known that a copper (Cu)M alloy with low electrical resistance has characteristics that are close to the above conditions. This Cu is a metal that is advantageous in meeting the above conditions such as having high electrical conductivity and easy workability, but is insufficient in terms of heat resistance strength, oxidation resistance, mechanical strength, etc. Therefore, since there is no metal that satisfies all of the above conditions, an alloy is used in which a metal that exhibits as many properties as possible is selected as the main component, and a number of additional components are mixed with this metal.

However, for example, alloys containing Cu as the main component and to which Sn and P are added have insufficient strength, and
Alloys in which Fe is added instead of n do not yet satisfy the above requirements.

Furthermore, in the case of conventional Cu-based alloys, ICs using this
When Sn solder is used to secure lead wires, etc. to a lead frame, the following inconvenient phenomena occur. FIG. 1 is an enlarged cross-sectional view of a joint portion taken by a scanning electron microscope when a lead frame 1 is joined with Sn--Pb solder 2. As shown in FIG. The structure of this layer is shown after 300 hours at 150°C, and the structure changes due to harsh conditions such as heat loads during IC operation, and the 3n forming the solder bonds with the Cu of the lead frame. to form several layers. The first layer is an a layer made of ε-Cu3Sn,
The second layer is a b layer made of 1-Cua Sn5, and the third layer is a zero layer made of only Pb or very high density Pb.

If this phenomenon is significant, it is not desirable for maintaining the reliability of soldering of IC elements.To prevent this phenomenon, it is necessary to reduce the amount of Sn added, which causes a decrease in gold bonding properties, and In order to prevent the strength of the lead frame from decreasing due to this, it is possible to add Ni or Fe. However, as shown in Figure 2,
When Ni or Fe is added, Ni and Fe are combined with Sn, and about 0.0% is added to the bonding surface between the lead frame 1 and the solder 2.
An intermetallic compound M3 consisting of N1(Fe)-8n with a thickness of 5 μm or less is formed (use conditions are the same as above)0 This metal compound layer is microscopically formed as a honeycomb of N1(Fe) and Sn. The formation of this layer 3, which exhibits a state of This can be a disadvantage.

This phenomenon is caused by Sn and Ni compared to the case where Sn is not included.
Alternatively, when F''e coexists in the alloy, the growth of the intermetallic compound layer is significantly promoted and peeling easily occurs.

The cause of the peeling as described above is estimated as follows. In other words, Cu strengthens the bond between the lead frame and solder.
It is thought that the solid solution state portion of -Sn decreases due to the formation of a barrier of the N1(Fe)-Sn intermetallic compound layer, and the mutual diffusion of Cu and Sn becomes insufficient, resulting in peeling.

From the above, it is necessary to reduce the amount of Ni, Fe, and Sn added to prevent peeling, but the strength will not improve unless Ni or Fe is added, and in this case, Ni-Sn
-In order to obtain the same strength as the Cu alloy, it is necessary to add 3% or more of Sn. However, increasing the amount of Sn adversely affects the isobaric properties of gold bonding, as described above. On the other hand, N
Increasing the amount of i or Fe easily causes peeling.

[Purpose of the invention]

The present invention provides an electronic component that has sufficient characteristics required as an electronic component, has extremely little generation of intermetallic compounds that have weak bonding strength when bonded with solder, and has excellent bonding strength. The purpose is to

[Summary of the invention]

The present inventors have completed the present invention by incorporating Zn as a third additive component to Ni or Fe and Sn into the alloy.

That is, in the electronic component of the present invention, the main component is Cu, and the first
0.05 to 5% of one or more of Ni or Fe as an additive component, and 0% of Sn as a second additive component.
．． 05-4fold fA%, 0.1 zn as the third added component
It is characterized by being formed from an alloy having ~3% N.

The present invention will be explained in more detail below.

Examples of the electronic component of the present invention include a lead frame and a lead wire.

The composition of the alloy used in the electronic component is such that Nl or Fe is in a range of 0.05 to 5% by weight, and Sn is in a range of 0.05 to 5% by weight.
4% by weight, zn fJ'-0, 1 to 3% by weight, and the remainder consists of Cu. In addition, when using Ni, Sn and Zn as additive components of the alloy, in addition to the above conditions, Zn for Ni (or Fe) and Sn
It is preferable that the weight ratio of Zn≧20 (Nl, Sn) is satisfied. Note that it is also possible to replace Nl with Fe, which is a part of Nl, and in this case, Zn≧earth(N
It is preferable to satisfy the relationship: i, Fe, Sn)0.

In the alloy composition according to the present invention, Ni, Fe and Sn
If the amount of each added is less than 0.05% by weight,
The strength of electronic components becomes insufficient, leading to inconvenient situations such as difficulty in inserting lead frames into sockets and deformation.
Alternatively, if the amount of Sn added exceeds 4% by weight, the electrical conductivity decreases and the heat conduction effect becomes insufficient. In addition, when the amount of Zn added is less than 0.1% by weight, N1(Fe) described below
Only a few concentrated diffusion-reducing layers are formed, and Ni (Fe
) An intermetallic compound is generated due to diffusion bonding of -Sn, and if the amount exceeds 3% by weight, the gold bonding property is decreased, the reliability of the IC device is impaired, and the yield is decreased.

Furthermore, if a large amount of Zn is added, Zn will instantly diffuse into the solder during soldering, causing the solder surface to become rough or
Various problems occur, such as a decrease in bonding strength.

The electronic component of the present invention is manufactured from the alloy as follows. For example, in the case of a lead frame, according to a conventional method,
After manufacturing an ingot made of the above alloy and rolling it,
It is obtained by coiling and subjecting it to pressing or etching processing.

The reason why the above problems are solved when the alloy according to the present invention is used will be explained based on FIG. 3.

Figure 3 shows a lead frame made of a Cu-Ni-Sn-Zn alloy, and a part of the frame is coated with Sn-P・b.
This is an enlarged cross-sectional view of the joint when the solder is welded and then intensely heated at about 150°C for 300 hours.
is a Ni concentrated diffusion mitigation layer. That is, Sn −p・
When bonded with b solder, almost no Ni-Sn intermetallic compound layer is formed, and instead, Zn-C
An N1 concentration diffusion reduction layer 4 is formed due to the Zn concentration of the U solid solution. Since the layer 4 has the effect of efficiently reducing or suppressing the diffusion bond between Ni dispersed in Cu and Sn in the solder, the movement of Ni in Cu is restricted and stable dispersion of Nl is achieved. The condition will be maintained for a long time.

Therefore, since almost no Ni-Sn intermetallic compound is generated, no peeling phenomenon occurs at the interface. In addition, when Ni is partially replaced with Fe and Ni0
Even when Fe is used instead, Fe and S
Diffusion coupling with n is suppressed.

〔Effect of the invention〕

As is clear from the above description, suitable results can be obtained when the alloy according to the present invention is used in electronic components for Sn soldering. That is, with the elimination of the peeling phenomenon at the interface based on the Ni(Fe)-Sn bond described above, the solder resistance and solder weather resistance are improved. Also, N in Cu
Since it is possible to add the maximum amount of i or Fe, there is an effect that the strength of the electronic component can be increased accordingly.

Furthermore, since concentrated diffusion of Ni and Fe in Cu is suppressed, a stable dispersion state is obtained, and a partial decrease in mechanical strength at the bonded portion is avoided. Further, even with the addition of these elements, the characteristics based on Cu such as high electrical conductivity and ease of processing are maintained.

[Embodiments of the invention]

Twelve types of lead frames of the present invention were manufactured by the following method.

After each element shown in the table was loaded into a ball mill, Ar gas was filled and mixed by stirring. The resulting composite was loaded into a deaerated container, heated and melted, and then hot extruded to form an ingot. Next, this ingot was hot-rolled and cold-rolled, and then cut to obtain a coil. Thereafter, this coil was pressed to produce a lead frame. In addition, the lead frames of sample numbers 1 and 2 in the table have an added amount of Nl or Fe in a range of 0.05 to 5% by weight, an sn of 0.05 to 4% by weight, and a zn of 0.1. ~
The lead frames of sample numbers 3 to 10 are made of alloys in the range of Miesha%, and in addition to the above conditions,
The weighting of Zn with respect to i, Fe and Sn is Zn≧
An alloy having the above relationship (Ni, Fe, Sn)0 is used.

On the other hand, for comparison, five types of lead frames made of alloy compositions other than those of the present invention shown in the table were prepared.

Sn--Pb solder was welded to the above lead frame sample, and the tests shown in the table were conducted. The criteria for each test item are approximately as follows.

Solderability: Determined by visual observation and observation.

〇-Excellent △-Good ×-Poor[]" Weather resistance: After intense heating at approximately 150°C for 300 hours, repeated bending at 90° was performed three times, and judgment was made based on the presence or absence of peeling.○ 〇 - No peeling △ - Peeling after 2 times x - Peeling once after 1 time Mechanical strength: Determined by micro Vickers hardness Nt.

○-130 MI (V or more X -130 MHv or less Conductivity...Judged by what percentage of conductivity it has when the conductivity of a lead frame made of pure copper is taken as 100 0-30 % or more △ -30 to 20% × -20% or less Ni concentrated diffusion reducing layer... After intense heating at about 150°C for 300 hours, determine whether the layer is formed or not by the XMA method. 0 Yes... Generated No... Not generated Regarding the above test results, ◎ indicates excellent in all aspects, ○ indicates excellent in almost all, and there are test items that are considered poor. Items were evaluated as ×.

The test results are summarized in the table.

[Brief explanation of drawings]

Figure 1 is an enlarged cross-sectional view showing the structure of a joint between a conventional lead frame and Pb-Sn solder after changes over time, and Figure 2 is an enlarged cross-sectional view of the joint between a conventional lead frame and Pb-Sn solder, and Figure 2 shows a case where Ni or Fe is increased in the alloy composition of the lead frame. FIG. 3 is an enlarged sectional view showing the structure of the joint of the lead frame of the present invention and 3n-
FIG. 2 is an enlarged cross-sectional view showing the state of the structure of a joint with PB solder after changes over time. 1...Lead frame, 2...811-Pb solder, a...e-Cu, Sn layer, b-1-Cu,,
Sn, layer, c・”P b hl, 3---Ni
(Fe) -8n intermetallic compound layer, 4 ・Ni (F
e) Concentrated diffusion mitigation layer.

Claims (2)

[Claims] (1) The main component is Cu, and the first additional component is Ni or F.
0.05 to 5% by weight of any one or more of e,
An electronic component characterized in that it is formed from an alloy containing 0.05 to 4% by weight of 3N as a second additive component and 0.1 to 3% by weight of ZN as a third additive component. (2) The weight ratio of Zn to Ni, Fe, and Sn is z
1-! in the relationship n≧±(Ni, Fe, Sn) 0! An electronic component according to claim 1.