JP5128152B2 - Copper alloy for lead frame excellent in bare bonding property and manufacturing method thereof - Google Patents

Description

The present invention relates to a copper alloy excellent in bare bonding property in which a lead wire for wire bonding (bonding wire) is directly bonded to an inner lead portion of a lead frame forming a semiconductor element without plating, and a manufacturing method thereof.

Conventionally, a semiconductor element is manufactured by forming a strip made of copper, a copper alloy, or a Fe—Ni alloy into a lead frame having a predetermined shape by press punching or etching, and then bonding the semiconductor chip and the lead frame to a gold wire or the like. Plating is applied to a predetermined portion of the lead frame for bonding using a wire. Next, the semiconductor chip is die bonded to the die pad portion of the lead frame, the semiconductor chip and the lead frame are bonded with a bonding wire, and then sealed to obtain a semiconductor element product.

As can be seen, plating is indispensable for joining the lead frame and the semiconductor chip and between the lead frame and the bonding wire.
However, since the plating operation is an operation on a minute portion of the lead frame, very high accuracy is required, and the quality of the plating has a great influence on the die bonding and wire bonding. In some cases, the defect rate of the semiconductor element is increased.

Furthermore, the plating on the lead frame uses gold plating or silver plating from the viewpoint of the material relationship between the semiconductor chip or bonding wire and the lead frame, durability, and electrical conductivity. It is also a cause.
In response to this situation, many proposals have been made on a method of directly bonding a lead frame and a bonding wire, ie, bare bonding, without plating on the lead frame (see Patent Documents 1 to 4). .

  Patent Documents 1 to 3 describe that surface roughness is appropriate for bare bonding properties. Further, Patent Document 3 and Patent Document 4 describe that the thickness of the oxide film existing on the surface layer is also defined to improve the bare bonding property. Furthermore, it is stated that the size of the precipitates or inclusions (Patent Document 1), the surface hardness (Patent Document 2), the size of crystal grains (Patent Document 4), and the like also contribute to the bare bonding property.

Japanese Examined Patent Publication No. 62-46071 Japanese Patent Laid-Open No. 2-170937 Japanese Patent Laid-Open No. 11-12714 JP 2000-273560 A

However, even with the above-described conventional technique, when several hundred or more wire bondings are performed, the wire breaking rate (which gives an indication of bonding reliability) In the test, the rate of breakage at the wire portion, not at the bonding portion) was improved only to about 95%, and it was difficult to say that it had practically sufficient reliability.
The present invention solves the above-mentioned problems and provides a copper alloy excellent in bare bondability for directly bonding bonding wires without plating the inner lead portion of the lead frame, and is excellent in such bare bondability. It aims at providing the manufacturing method of a copper alloy.

According to the present invention, the following means are provided:
(1) free energy of oxide formation at 300 ° C. from 0.99 ° C. which is a temperature range of wire bonding of the semiconductor element unrealized less than 1 mass% beyond 0.1mass% by total weight of the lower element group than Cu, the balance A copper alloy comprising Cu and unavoidable impurities , comprising 0.03 mass% to 0.8 mass% Fe as the element group and 0.001 mass% to 0.1 mass% P as the element group, and processing the surface layer of the copper alloy A lead frame copper alloy having a deteriorated layer thickness of 0.2 μm or less (including 0 μm), a wire breakage ratio of 99% or more and excellent bare bondability.
(2) An element group in which the free energy of formation of oxide at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of a semiconductor element, is lower than Cu element is included in a total mass of more than 0.1 mass% and less than 1 mass%, and the balance Cu And an inevitable impurity copper alloy, wherein the element group includes Fe of 0.03 mass% to 0.8 mass%, P of 0.001 mass% to 0.1 mass%, and 0.1 mass% to 0.4 mass. % Of Zn and 0.05 mass% to 0.4 mass% of Sn or 2 kinds, the thickness of the work-affected layer on the surface layer of the copper alloy is 0.2 μm or less (including 0 μm), and the wire breaking rate Is a copper alloy for lead frames that has 99% or more and excellent bare bondability.
(3) The element formation free energy of the oxide at 150 ° C. to 300 ° C. which is the temperature range of wire bonding of the semiconductor element is lower than the Cu element, and the total mass is more than 0.1 mass% and less than 1 mass%, and the remaining Cu And an inevitable impurity copper alloy containing 0.1 mass% to 0.4 mass% of Cr and 0.05 mass% to 0.4 mass% of Zr as the element group, and processing alteration of the surface layer of the copper alloy A copper alloy for lead frames having a layer thickness of 0.2 μm or less (including 0 μm), a wire breakage rate of 99% or more and excellent bare bondability.
(4) An element group in which the free energy of formation of an oxide at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of a semiconductor element, is lower than Cu element is included in a total mass of more than 0.1 mass% and less than 1 mass%, and the balance Cu And 0.1 mass% to 0.4 mass%, Zr from 0.05 mass% to 0.4 mass%, and 0.01 mass% to 0.3 mass as the element group. % Of Si and 0.1 mass% to 0.4 mass% of Zn, or 2 or more kinds of Zn, the thickness of the work-affected layer on the surface of the copper alloy is 0.2 μm or less (including 0 μm), and the wire breaking rate Is a copper alloy for lead frames that has 99% or more and excellent bare bondability.

(5) A lead frame for bare bonding formed by molding a strip made of the copper alloy for lead frames according to any one of ( 1 ) to (4) .

(6) An element group in which the free energy of formation of oxide at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of a semiconductor element, is lower than Cu element is included in a total mass of more than 0.1 mass% and less than 1 mass% (1) consisting essentially has a composition according to any one of (4) with respect to the copper alloy, and damaged layer by the thickness control below 0.2μm thickness of the surface layer of the work-affected layer (including 0 .mu.m) ( producing how the lead frame copper alloy having excellent bare bondability according to any one of 1) (4).

(7) the process-induced degradation layer thickness control is a process comprising at least a chemical dissolution treatment (6) producing how the lead frame copper alloy having excellent bare bondability according.

(8) the process-induced degradation layer thickness control is a process comprising at least electrochemical dissolution process (6) producing how the lead frame copper alloy having excellent bare bondability according.

(9) the process-induced degradation layer thickness control is a method including a heat treatment under at least a non-oxidizing atmosphere (6) producing how the lead frame copper alloy having excellent bare bondability according.

(10) the process-induced degradation layer thickness control is chemical dissolution treatment, after this, the damaged layer is a method of applying a non finish rolling form (6) of the bare bondability to excellent leadframe copper alloy according production how.

(11) the process-induced degradation layer thickness control is electrochemical dissolution process, after this, a method of applying a finish rolling that does not form a damaged layer (6), wherein the bare bonding property to the excellent lead frame for Copper Alloy of production how.

(12) the process-induced degradation layer thickness control is a heat treatment under a non-oxidizing atmosphere, after this, a method of applying a finish rolling that does not form a damaged layer (6) lead frame excellent bare bondability according production how to use copper alloy.
(13) Hot and cold rough rolling, aging annealing, buff polishing on an ingot cast from a copper alloy material having the composition described in any one of (1) to (4) The bare bonding property according to any one of (6) to (12), wherein the steps of thickness change of the work-affected layer, finish cold rolling without forming the work-affected layer, and low-temperature annealing are performed in this order. A method for producing a copper alloy for a lead frame.

The copper alloy for lead frames excellent in bare bonding property of the present invention has excellent connection reliability in bare bonding by suppressing the thickness of the non-uniform and fine work-affected layer existing in the surface layer of the copper alloy to 0.2 μm or less. Is. Furthermore, the lead frame that is bare-bonded using the copper alloy according to the present invention does not cause a defect due to bonding failure, and thus has a high yield and high reliability.

In general, a copper alloy is produced by appropriately combining processes such as casting, rolling, buffing, and annealing. As a result of the various plastic workings during the manufacturing process, as a result, a work-affected layer 1 and a plastically deformed layer 2 having a finer structure than the inside of the copper alloy as shown in FIG. 1 are formed on the surface of the copper alloy. The

Here, the “work-affected layer” means an amorphous structure called a Bailby layer (upper layer) generated in the surface layer of a copper alloy as a result of the various plastic workings, and a fine crystalline layer ( A non-uniform microstructure comprising a lower layer).
The “plastic deformation layer” is a crystal texture in which the crystal grains are coarser than the fine crystal layer and move away from the surface layer, and approach the size of the crystal grains inside the copper alloy.
The size of the crystal grains in the plastic deformation layer and the copper alloy is not limited because it varies depending on the composition of the copper alloy, the manufacturing conditions, etc., but for example, the size of the crystal grains in the plastic deformation layer is About 0.2 to 3.0 μm, and the size of crystal grains inside the copper alloy is about 3.0 μm to 10 μm, and can be easily distinguished from the work-affected layer.

In such a surface layer structure, when wire bonding is performed on a work-affected layer that is a non-uniform microstructure, the bonding surface is broken at the portion where the bonding force between the wire and the surface layer is weak, and the connection reliability is reduced. It will decrease.
Therefore, the thickness of the work-affected layer is preferably 0.2 μm or less, and more preferably 0.05 μm or less. If the work-affected layer is thicker than 0.2 μm, the connection reliability of wire bonding decreases.

Next, when a copper alloy is manufactured by appropriately combining processes such as casting, rolling, buffing, and annealing, an oxide film of about 1 to 5 nm is usually formed on the surface. Although it is well known that when the oxide film on the surface of the copper alloy is thick, bonding failure is caused and connection reliability is lowered, the wire bonding process is performed in a reducing atmosphere represented by 150 to 300 ° C. and 10 vol% H ₂ -N _2. Therefore, when the thickness of the oxide film, the oxide film is reduced and removed at the time of wire bonding, and there is no risk of impairing connection reliability. However, the oxide generation free energy contains an element lower than the Cu element. The oxide film is difficult to be reduced during the reduction and removal of the oxide film, and remains as an oxide on the surface of the copper alloy, causing bonding failure.

Thus, S i free energy of formation Ru lower element der than Cu element of the oxide at 300 ° C. from 0.99 ° C. which is the temperature range of the wire bonding process, P, C r, F e , Z n, Zr, S n is the total mass of the content, that be less than 1 mass%.
On the other hand, many of these elements are often contained for the purpose of improving the strength of the copper alloy, and if the content is extremely small, the material strength is lowered, which makes it unsuitable as a copper alloy for lead frames. from the total mass of the element, including beyond 0.1mass%.
These conditions are satisfied copper alloy, C u-Cr-Zr-based, there is a Cu-Fe-P system.

In the Cu-Fe-P alloy, Fe is dissolved in Cu to increase the strength and forms a compound with P to precipitate, and acts to increase the strength without impairing the conductivity. If the content is less than 03 mass%, the effect is small, and if the content exceeds 0.8 mass%, the conductivity is lowered.
P forms a precipitate with Fe and works to increase the strength, and if it is less than 0.001 mass%, there is no effect, and if it exceeds 0.1 mass%, the productivity is lowered.
Further, if necessary, one or both of Zn of 0.1 mass% to 0.4 mass% and Sn of 0.05 mass% to 0.4 mass% may be contained. Both Zn and Sn are dissolved to show a function of greatly improving their strength, and Zn shows a function of improving the bonding property with solder containing Sn.

As for a Cu-Zr-Cr type alloy, it is desirable that the component composition for obtaining good strength and conductivity as a lead frame is in the following range.
Cr acts to greatly increase the strength by precipitating in copper without losing conductivity, and its effect is small when it is less than 0.1 mass%, and the effect is saturated when it exceeds 0.4 mass%. At the same time, an oxide is easily generated and adversely affects the bare bonding property. Therefore, the content is set to 0.1 mass% to 0.4 mass%.
Zr also functions to greatly increase the strength without deteriorating the conductivity by precipitating in copper like Cr, and its effect is small when it is less than 0.05 mass%, and it exceeds 0.4 mass%. The effect is saturated, and coarse crystallized substances and oxides are easily generated, which adversely affects the bare bonding property. From 0.05 mass% to 0.4 mass%.

Furthermore, 0.01 mass% to 0.3 mass% Si may be included. Si forms Cr and Cr—Si precipitates, and functions to increase the strength of the copper alloy by composite precipitation of Cr and Cr—Si. If it is less than 0.01 mass%, the effect is not observed, and if it exceeds 0.3 mass%, the conductivity is impaired.
These Cu—Zr—Cr alloys further contain 0.1 mass% to 0.4 mass% of Zn as required. The inclusion of Zn serves to increase the strength by solid solution hardening and cold working, and also improves the bondability with the solder containing Sn.

The thickness of the work-affected layer can be controlled by removing the work-affected layer in a timely manner during the manufacturing process, and the removal of the work-affected layer in the final process is the most reliable. The thickness of the work-affected layer can be controlled.
However, since it becomes difficult to obtain dimensional accuracy such as the thickness of the sheet, control of the work-affected layer, usually the removal process, is performed immediately before finish rolling, and then finish rolling is performed so as not to form the work-affected layer as much as possible. A method of performing a predetermined plate thickness is desirable.

As the method for removing the work-affected layer, the first is chemical dissolution treatment, the second is electrochemical dissolution treatment, the third is physical treatment such as sputtering, and the fourth is heat treatment in a non-oxidizing atmosphere. There is a method in which the work-affected layer is lost by applying it to recover the crystallinity of the amorphous or fine crystal structure so as to have the same structure as the crystal structure of the plastic deformation layer or the copper alloy.
Among these methods, in the case of physical processing such as sputtering, since there are restrictions in terms of applicable dimensions or processing time, industrial methods include chemical dissolution processing, electrochemical dissolution processing, and It is desirable to adopt a removal method by heat treatment.

The chemical dissolution treatment is a method of dissolving a work-affected layer using an acid solution in which an acid and an oxidant are combined. An acid such as sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, hydrogen peroxide, chromium An oxidizing agent such as acid salt or persulfate is used in combination, but a combination of sulfuric acid and hydrogen peroxide is preferable from the viewpoint of dissolution rate, environmental aspect and workability.

The electrochemical dissolution treatment includes an anodic electrolysis method in an acidic solution. The electrolyte used is an acid such as phosphoric acid or sulfuric acid with an inorganic acid such as chromic acid added. However, for copper alloys, phosphoric acid electrolytes with a long track record and excellent polishing effect are available. Is preferred.

The heat treatment method includes heat treatment in a heating furnace in a non-oxidizing atmosphere such as a reducing atmosphere or an inert atmosphere. By combining the atmosphere, heating temperature and heating time as appropriate, batch-type heating in an annealing furnace and running heating in a running annealing furnace can also be applied, but to prevent oxidation of the surface layer during removal processing of the work-affected layer. Is preferably heated in a reducing atmosphere such as hydrogen, and batch-type heating in a bell furnace or the like is preferable from the viewpoint of stability of oxygen concentration during heat treatment.

The work-affected layer is observed by observing the surface layer portion in the cross section in the plate thickness direction as shown in FIGS. In order to clearly identify the tissue, the tissue observation is preferably performed by magnifying it about 10,000 times using an electron microscope, and the observation device such as SIM or FE-SEM is used together for more detailed observation. Is possible. Furthermore, in the preparation of the observation sample, a method in which a work-affected layer is not formed in cross-section processing is desirable, and an apparatus such as FIB may be used.

The cross-sectional structure of the copper alloy according to the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional photograph of a copper alloy by SIM observation. FIG. 2 is a schematic explanatory view of a cross section of a copper alloy composed of a work-affected layer 1 and a plastically deformable layer 2.
As apparent from FIG. 2, the work-affected layer 1 is composed of a Bailby layer 1a (upper layer) and a fine crystal layer 1b (lower layer). The Bailby layer 1a has an amorphous structure, and the fine crystal layer 1b has an extremely fine structure. It is a crystal texture. The plastic deformation layer 2 existing further below the work-affected layer 1 has crystal grains that are coarser than the fine crystal layer, and the work-affected layer 1 and the plastic deformation layer 2 are clearly different in crystal structure as shown in FIG. The boundary portion (broken line portion) is clear and both can be easily identified.

  Since the formation amount of the work-affected layer 1 changes depending on the degree of plastic working, the thickness may change in the field of view or the comparison of a plurality of observation places in which the enlarged observation is performed by electron microscope observation. Therefore, the thickness at the position where the work-affected layer is the thickest is measured in the field of magnification observation, such thickness is observed at five places, and the average of the measured values is defined as the thickness of the work-affected layer.

  Hereinafter, the present invention will be described in detail with reference to examples.

[Example 1]
A copper alloy comprising the component composition shown in Table 1 and comprising the remainder Cu and inevitable impurities is cast, followed by hot and cold rough rolling, aging annealing, buffing, chemical dissolution treatment, finish rolling, and low temperature annealing. To produce a copper alloy strip having a thickness of 0.15 mm.
The chemical dissolution treatment is performed by immersing in an aqueous solution containing sulfuric acid 100 g / l and hydrogen peroxide 15 g / l at the same temperature as the room temperature, and the final work-affected layer thickness is 0 It is adjusted to be 0.05, 0.2, 0.3, 0.5, and 1.0 μm.

When the surface roughness of the prepared sample and the thickness of the oxide film were measured, the maximum surface height (Rmax) was 0.6 to 1.0 μm, and the centerline surface average roughness (Ra) was 0.07 to 0.12 μm. The thickness of the oxide film is 1 to 5 nm, and it has been confirmed that it is almost the same value as the copper alloy for lead frames currently in general distribution.
The surface roughness was measured using a universal surface roughness measuring instrument, and the thickness of the oxide film was calculated from the amount of reduced electricity of cathode electrolysis in a 0.1N-KCl solution.

For the evaluation of the bare bonding property, using the sample prepared as described above, bare bonding was performed under the bonding conditions shown in Table 2, and the wire breaking rate (%) was calculated by the pull test and the wire breaking rate (%) = (wire The number of ruptured by the number of all tests) × 100. The results are shown in Table 3.

As apparent from Table 3, in the present invention example 4 c from the present invention Example 3 a, the thickness of the damaged layer becomes 0.2μm or less, at the wire breakage rate every 99%, excellent connection reliability (All examples in Table 3 have a wire breakage rate of 99.4% or more).
In particular, when the thickness of the work-affected layer is 0.05 μm or less, the wire breakage rate is 99.9% or more, which is particularly excellent. On the other hand, Comparative Example 2 4 b from Comparative Example 2 3 a, Comparative Example 26b, Comparative Example 2 7 b and Comparative Example 2, 8 b, the wire breakage rate the thickness of the damaged layer is for thicker than 0.2μm 97% It can be seen that the connection reliability is inferior. Further, in Comparative Example 26a, Comparative Example 27a, and Comparative Example 28a, the total mass of the elements whose oxide free energy of formation at 250 ° C. is lower than Cu is larger than 1.0 mass%. However, it can be seen that the wire breakage rate is less than 81% and is greatly inferior in connection reliability.

[Example 2]
Next, except that the thickness of the work-affected layer was controlled by electrochemical dissolution, a sample was prepared by the same method as in Example 1, bare bonding was performed under the same conditions, and the wire breaking rate was obtained by a pull test, The results are shown in Table 4.
The electrochemical dissolution treatment used here is anodic electrolysis in an aqueous solution containing 700 g / l phosphoric acid at room temperature and a current density of 10 A / dm ² , and the final processing-affected layer thickness is changed by changing the energization time. Is adjusted to be 0, 0.05, 0.2, 0.3, 0.5, and 1.0 μm.
The prepared sample has a maximum surface height (Rmax) of 0.6 to 1.0 μm, a center line surface average roughness (Ra) of 0.07 to 0.12 μm, and an oxide film thickness of 1 to 5 nm.

As is clear from Table 4, invention sample 9 c thickness of the damaged layer from the present invention Example 8 a which is 0.2μm or less, wire breakage rate becomes 99% or more, shows excellent connection reliability it is (examples in Table 4 are all wire breakage rate 99.5% or higher).
In particular, when the thickness of the work-affected layer is 0.05 μm or less, the wire breakage rate is 99.9% or more, indicating that the connection reliability is particularly excellent. On the other hand, processing thick Comparative Example thickness than 0.2μm deteriorated layer 3 Comparative Example from 2 a 3 3 b, Comparative Example 35b, Comparative Examples 36b and Comparative Example 37b, the connection reliability wire breakage rate is less than 96% You can see that it is inferior.
Further, in Comparative Example 35a, Comparative Example 36a, and Comparative Example 37a, the total mass of elements whose oxide formation free energy at 250 ° C. in the alloy is lower than Cu is larger than 1.0 mass%, so that a work-affected layer exists. Even when not, the wire breakage rate is less than 82%, indicating that the connection reliability is greatly inferior.

Example 3
A sample was prepared under the same conditions as in Example 1 except that the work-affected layer thickness was controlled using heat treatment, bare bonding was performed under the conditions shown in Table 2, and the wire breakage rate in the pull test was obtained. The results are shown in Table 5.
The heat treatment is performed in a heating furnace in a hydrogen reduction atmosphere, and the final work-affected layer thickness is changed to 0, 0.05, 0.2, 0.3, 0.5, 1. Adjustment is made to be 0 μm.
The prepared sample has a maximum surface height (Rmax) of 0.6 to 1.0 μm, a centerline surface average roughness (Ra) of 0.07 to 0.12 μm, and an oxide film thickness of 1 to 5 nm.

In Invention Examples 1 3 a to 1 4 c in which the thickness of the work-affected layer is 0.2 μm or less, it can be seen that the wire breakage ratio is 99% or more and the connection reliability is excellent (invention examples in Table 5). All show a wire breakage rate of 99.4% or more).
In particular, when the thickness of the work-affected layer is 0.05 μm or less, the wire breakage rate is 99.9% or more, and the connection reliability is further improved.
On the other hand, process-induced degradation layer of a thickness comparison of thick Comparative Example 4 2 a than 0.2μm Example 4 3 b and Comparative Examples 45b, Comparative Example 46b, in Comparative Example 47b is connected reliability wire breakage rate is less than 96% It is inferior to. In Comparative Example 45a, Comparative Example 46a, and Comparative Example 47a, the total mass of elements whose oxide free formation energy at 250 ° C. in the alloy is lower than Cu exceeds 1.0 mass%. Even in the absence of the wire, it shows a wire breakage rate of less than 81%, indicating that the connection reliability is greatly inferior.

It is a cross-sectional photograph of the copper alloy by SIM observation. It is a model explanatory drawing of the copper alloy cross section which consists of a work-affected layer and a plastic deformation layer.

Explanation of symbols

1 Work-affected layer 1a Bailby layer 1b Microcrystalline layer 2 Plastic deformation layer

Claims (13)

Free energy of oxide formation is unrealized less than 1 mass% beyond 0.1mass% by total weight of the lower element group of Cu element in the 300 ° C. from 0.99 ° C. which is a temperature range of wire bonding of the semiconductor element, balance Cu and incidental a copper alloy consisting of impurities, a 0.8 mass% and P from 0.001% from 0.03 mass% of Fe as the element group includes 0.1mass%, the surface layer of the work-affected layer of the copper alloy A copper alloy for lead frames having a thickness of 0.2 μm or less (including 0 μm), a wire breakage rate of 99% or more and excellent bare bondability.   Contains a group of elements whose free energy of formation of oxide is lower than Cu element at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of semiconductor elements, with a total mass of more than 0.1 mass% and less than 1 mass%, with the remainder being Cu and inevitable A copper alloy comprising impurities, wherein the element group includes Fe of 0.03 mass% to 0.8 mass%, P of 0.001 mass% to 0.1 mass%, and 0.1 mass% to 0.4 mass% of Zn. 1 or 2 of 0.05 mass% to 0.4 mass% of Sn, the thickness of the work-affected layer of the surface layer of the copper alloy is 0.2 μm or less (including 0 μm), and the wire breakage rate is 99% This is a copper alloy for lead frames that has excellent bare bondability.   Contains a group of elements whose free energy of formation of oxide is lower than Cu element at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of semiconductor elements, with a total mass of more than 0.1 mass% and less than 1 mass%, with the remainder being Cu and inevitable A copper alloy comprising impurities, the element group containing 0.1 mass% to 0.4 mass% of Cr and 0.05 mass% to 0.4 mass% of Zr, and the thickness of the work-affected layer on the surface layer of the copper alloy 0.2 μm or less (including 0 μm), the wire fracture rate is 99% or more, and the copper alloy for lead frames having excellent bare bonding properties.   Contains a group of elements whose free energy of formation of oxide is lower than Cu element at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of semiconductor elements, with a total mass of more than 0.1 mass% and less than 1 mass%, with the remainder being Cu and inevitable A copper alloy comprising impurities, wherein the element group includes Cr of 0.1 mass% to 0.4 mass%, Zr of 0.05 mass% to 0.4 mass%, and 0.01 mass% to 0.3 mass% of Si. And 0.1 to 0.4 mass% of Zn in one or two types, the thickness of the work-affected layer on the surface of the copper alloy is 0.2 μm or less (including 0 μm), and the wire breaking rate is 99% This is a copper alloy for lead frames that has excellent bare bondability. 請 Motomeko bare bonding lead frame formed by molding a strip material made of lead frame copper alloy according to any one of claims 1 to 4. 2. The element group in which the free energy of formation of an oxide at 150 ° C. to 300 ° C., which is a temperature range for wire bonding of a semiconductor element, is lower than Cu element is included in a total mass of more than 0.1 mass% and less than 1 mass%. the copper alloy consisting had a composition according to any one of 4, the thickness of the surface layer of the damaged layer by process-induced degradation layer thickness control of claims 1 to 0.2μm or less (including 0 .mu.m) The manufacturing method of the copper alloy for lead frames which is excellent in the bare bondability of any one of Claim 4 . Manufacturing method of the process-induced degradation layer thickness control lead frame copper alloy having excellent bare bondability methods der Ru請 Motomeko 6 further comprising at least a chemical lysis treatment. Manufacturing method of the process-induced degradation layer thickness control lead frame copper alloy having excellent bare bondability methods der Ru請 Motomeko 6 further comprising at least electrochemical dissolution process. Manufacturing method of the process-induced degradation layer thickness control lead frame copper alloy having excellent bare bondability methods der Ru請 Motomeko 6 further comprising a heat treatment under at least a non-oxidizing atmosphere. Wherein a damaged layer thickness control chemical dissolution treatment, after this, the process-damaged layer Ru method der performing non finish rolling form 請 Motomeko 6 wherein bare bonding property to the excellent lead frame copper alloy for manufacturing Method. Wherein a damaged layer thickness control electrochemical dissolution process, after this, the process-damaged layer Ru method der performing non finish rolling form 請 Motomeko 6 wherein bare bonding property to the excellent lead frame for Copper Alloy Production method. The process-induced degradation layer thickness control is a heat treatment under a non-oxidizing atmosphere, after this, lead frame excellent in bare bondability methods der Ru請 Motomeko 6 wherein performing finish rolling that does not form a damaged layer A method for producing a copper alloy.   An ingot formed by casting a copper alloy material having the composition according to any one of claims 1 to 4, to hot and cold rough rolling, aging annealing, buffing, and the processing The leadframe excellent in bare bondability according to any one of claims 6 to 12, wherein the steps of thickness change control, finish cold rolling without forming a work affected layer, and low temperature annealing are performed in this order. A method for producing a copper alloy.