JP4197718B2 - High strength copper alloy sheet with excellent oxide film adhesion - Google Patents

Description

  The present invention relates to a Cu-Fe-P-based copper alloy plate having high strength and improved oxide film adhesion in order to cope with package cracking and peeling problems. The copper alloy plate of the present invention is suitable as a material for a lead frame for a semiconductor device. In addition to the lead frame for a semiconductor device, other semiconductor components, electrical / electronic component materials such as a printed wiring board, switch parts, bus bars, It is suitably used for various electrical and electronic parts such as mechanical parts such as terminals and connectors. However, in the following description, as a typical application example, the description will be focused on the case where it is used for a lead frame which is a semiconductor component.

  Conventionally, as a copper alloy for a semiconductor lead frame, a Cu—Fe—P-based copper alloy containing Fe and P has been generally used. Examples of these Cu-Fe-P-based copper alloys include, for example, a copper alloy containing Fe: 0.05 to 0.15% and P: 0.025 to 0.040% (C19210 alloy), Fe: 2 An example is a copper alloy (CDA194 alloy) containing 0.1 to 2.6%, P: 0.015 to 0.15%, and Zn: 0.05 to 0.20%. These Cu-Fe-P-based copper alloys are excellent in strength, conductivity and thermal conductivity among copper alloys when an intermetallic compound such as Fe or Fe-P is precipitated in the copper matrix. Therefore, it is widely used as an international standard alloy.

  In recent years, along with the increase in capacity, size, and functionality of semiconductor devices used in electronic devices, lead frames used in semiconductor devices have become smaller in cross-sectional area, resulting in greater strength, conductivity, and thermal conductivity. Is required. Accordingly, copper alloy plates used for lead frames used in these semiconductor devices are required to have higher strength and thermal conductivity.

  On the other hand, plastic packages for semiconductor devices have become mainstream because packages in which a semiconductor chip is sealed with a thermosetting resin are excellent in economy and mass productivity. These packages are becoming thinner with the recent demand for miniaturization of electronic components.

  In assembling these packages, the semiconductor chip is heat bonded to the lead frame using Ag paste or the like, or soldered or brazed via a plating layer of Au, Ag or the like. Then, after resin sealing is performed and the resin sealing is performed, an outer lead is generally subjected to exterior plating by electroplating.

  The biggest problem related to the reliability of these packages is the problem of package cracks and peeling that occur during surface mounting. When the semiconductor package is assembled and the adhesion between the resin and the die pad (portion where the semiconductor chip of the lead frame is placed) is low, the package is peeled off due to thermal stress during the subsequent heat treatment.

  On the other hand, since the mold resin absorbs moisture from the atmosphere after the semiconductor package is assembled, moisture is vaporized in the subsequent heating in surface mounting. Is applied and acts as an internal pressure. This internal pressure causes the package to swell, or the resin cannot withstand the internal pressure and causes cracks. When cracks occur in a package after surface mounting, moisture and impurities enter and corrode the chip, which impairs the function as a semiconductor. In addition, the appearance of the package swells and the product value is lost. Such a problem of package cracking and peeling has become remarkable in recent years with the progress of thinning of the package.

  Here, the problem of package cracks and peeling is caused by poor adhesion between the resin and the die pad, but the oxide film of the lead frame base material has the greatest influence on the adhesion between the resin and the die pad. is there. The lead frame base material is subjected to various heating processes in order to manufacture plates and lead frames. For this reason, an oxide film having a thickness of several tens to several hundreds nm is formed on the surface of the base material before plating with Ag or the like. Since the copper alloy and the resin are in contact with each other through the oxide film on the surface of the die pad, the separation of the oxide film from the lead frame base material leads to the separation of the resin and the die pad, and the lead frame base material. The adhesion of the resin to the resin is significantly reduced.

  Therefore, the problem of package cracking and peeling depends on the adhesion of the oxide film to the lead frame base material. For this reason, the strengthened Cu-Fe-P copper alloy plate as a lead frame base material is required to have high adhesion of an oxide film formed on the surface through various heating processes. The

  In addition, the heating temperature in the various heating processes for manufacturing the copper alloy plate and the lead frame is increasing more and more in order to improve productivity and efficiency. For example, in the lead frame manufacturing process, it is required to perform heat treatment after press working or the like at a higher temperature and in a shorter time. As the heating temperature becomes higher, the oxide film formed on the lead frame base material has a higher density than the previous oxide film generated by low temperature heating due to problems such as densification. It has a new problem that it is easier to peel off.

  Improvements in oxide film adhesion have been proposed for a long time, though few. For example, Patent Document 1 proposes by controlling the crystal orientation of the copper alloy electrode surface layer. That is, in Patent Document 1, in the crystal orientation of the extreme surface evaluated by the XRD thin film method of the lead frame base copper alloy, the {100} peak intensity ratio with respect to the {111} peak intensity is set to 0.04 or less. It has been proposed to improve film adhesion. In addition, in this patent document 1, although all lead frame base material copper alloys are included, Cu-Fe-P-type copper alloys which are illustrated substantially are Cu- having a large Fe content of 2.4% or more. Only Fe-P-based copper alloys.

In Patent Documents 2 and 3, focusing on the surface roughness of the Cu—Fe—P-based copper alloy plate, the center line average roughness Ra in the surface roughness measurement is 0.2 μm or less, and the maximum height Rmax is 1. It has been proposed to improve the oxide film adhesion by setting the thickness to 5 μm or less. More specifically, in Patent Documents 2 and 3, the control of the surface roughness is controlled by the type (surface roughness) of a cold rolling mill roll.
JP 2001-244400 A Japanese Patent Laid-Open No. 2-122035 Japanese Patent Laid-Open No. 2-145734

  However, these conventional techniques do not reach the high level of oxide film adhesion intended by the present invention. That is, the new problem that the oxide film on the surface of the lead frame base material generated at a high heating temperature is more likely to be separated from the lead frame base material cannot be generally addressed.

  First, the substantial Fe content of the Cu—Fe—P-based copper alloy in Patent Document 1 exceeds 2.4% by mass as described above. In this regard, the technique of Patent Document 1 may be effective for improving the oxide film adhesion of a Cu—Fe—P copper alloy having a large Fe content. In fact, in Patent Document 1, the adhesion of the oxide film of the Cu—Fe—P-based copper alloy of Example 1 in which the Fe content is 2.41% is up to 633 K (360 ° C.) at the separation limit temperature of the oxide film. It has improved.

  However, when the Fe content exceeds 2.4% by mass, the oxide film on the surface of the lead frame base material generated at a high heating temperature becomes more easily separated from the lead frame base material. In addition, there is another problem that not only material properties such as conductivity but also productivity such as castability is significantly reduced.

  Further, for example, if the amount of the precipitated particles is increased in order to forcibly increase the electrical conductivity, there is a problem in that the strength and heat resistance are lowered due to growth and coarsening of the precipitated particles. In other words, the technique of Patent Document 1 cannot combine the high strength and oxide film adhesion required for a Cu—Fe—P-based copper alloy.

  Therefore, even if the technique of Patent Document 1 is applied as it is to a Cu-Fe-P-based copper alloy whose strength has been increased by a composition in which the Fe content is substantially reduced to 0.5% or less, it has been described above. The oxide film adhesion required for a lead frame or the like cannot be obtained.

  Further, as in Patent Documents 2 and 3, when the center line average roughness Ra is 0.2 μm or less and the maximum height Rmax is 1.5 μm or less, the surface roughness is certainly rougher than this. Compared to a Cu—Fe—P copper alloy plate, the oxide film adhesion is improved.

  However, according to the findings of the present inventors, the oxide film adhesion of the oxide film generated by heating at a higher temperature than the object of the present invention is the same (equally) as described later. Even when the center line average roughness Ra was 0.2 μm or less and the maximum height Rmax was 1.5 μm or less, a large difference was unexpectedly produced in the oxide film adhesion performance.

  This indicates that elements (factors) other than the center line average roughness Ra and the maximum height Rmax are greatly involved. This means that unless this element (factor) is controlled, the oxide film adhesion of the oxide film generated by heating at a higher temperature than the object of the present invention cannot be improved.

  The present invention has been made to solve such problems, and the object is to achieve both high strength and excellent oxide film adhesion of an oxide film generated by heating at a higher temperature. It is to provide a Cu—Fe—P based copper alloy sheet.

In order to achieve this object, the gist of the high-strength copper alloy sheet excellent in adhesion to the oxide film of the present invention is mass%, Fe: 0.01 to 0.50%, P: 0.01 to 0.15%. In the surface roughness measurement of the copper alloy plate according to JIS B0601 method, which has a tensile strength of 500 MPa or more and a hardness of 150 Hv or more. The center line average roughness Ra is 0.050 μm or less , the maximum height Rmax is 1.5 μm or less, and the kurtosis (kurtosis) Rku of the roughness curve is 3.1 or less .

The copper alloy plate of the present invention further comprises 0.005 to 3.0% Zn in mass% for improving the heat-resistant peelability of solder and Sn plating, or further mass to achieve high strength. % 0.005-5.0% Sn may be contained together with Zn.

The copper alloy plate of the present invention may further contain 0.001 to 1.0% of Co together with Zn in mass%.

The copper alloy plate of the present invention may further contain 0.001 to 1.0% of Mn and 0.001 to 1.0% of Ni, together with Zn and Sn.

  The copper alloy plate of the present invention further includes Hf, Th, Li, Na, K, Sr, Pd, W, S, Si, C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As. , Sb, Bi, Te, B, misch metal content is preferably 0.1% by mass or less in total of these elements.

  The copper alloy plate of the present invention can be applied to various electric and electronic parts, but is particularly preferably used for a semiconductor lead frame which is a semiconductor part.

  The copper alloy sheet of the present invention has a tensile strength of 500 MPa or more and a hardness of 150 Hv or more as a standard for increasing the strength. The electrical conductivity in the copper alloy plate correlates with the strength of the plate. Even in the present invention, the electrical conductivity is inevitably lowered as the strength becomes higher, but there is no problem in practical use. Therefore, the high conductivity referred to in the present invention means that the conductivity is relatively high for high strength.

  In the present invention, the oxide film adhesion is controlled by controlling the kurtosis (kurtosis) Rku of the roughness curve of the Cu-Fe-P-based copper alloy plate having an oxide film formed by heating at a higher temperature and higher strength. Improve.

  The kurtosis (kurtosis) Rku of the roughness curve is a well-known one defined in JIS B0601 for measuring the surface roughness, as shown in the following formula, and the roughness of the surface roughness (rolling waviness curve Z ( The sharpness of the curve x) is shown.

  For example, as shown in FIG. 1A, when Rku is larger than 5.0, the surface roughness unevenness curve (curve of rolling circle waviness curve Z (x)) is sharp or steep. It is a simple curve. On the other hand, as shown in FIG. 1B, when the Rku is as small as 5.0 or less as in the present invention, the surface roughness unevenness curve (curve of rolling circle waviness curve Z (x)). Is a relatively rounded or smooth curve.

  According to the knowledge of the present inventors, the roughness curve of the surface roughness (curve of rolling circle waviness curve Z (x)) is relatively rounded or smooth as described above, with Rku being 5.0 or less. The curved line can improve the oxide film adhesion of the oxide film generated by heating the Cu-Fe-P-based copper alloy plate at a higher temperature.

  Rather, the anchor effect is exhibited when the roughness of the surface roughness is pointed or a sharp curve as shown in FIG. 1A where Rku exceeds 5.0. It seems to improve the oxide film adhesion. In this respect, why, as shown in FIG. 1 (b), the surface roughness unevenness is relatively rounded or has a smooth curve at a higher temperature than that of the Cu—Fe—P based copper alloy plate. It is unclear at this time whether the oxide film adhesion of the oxide film produced by heating can be improved.

  However, in the present invention, the kurtosis (kurtosis) of the roughness curve of a copper alloy plate having a Cu-Fe-P-based composition can be achieved without increasing the Fe content and causing other problems as in the prior art. ) With the simple means of controlling Rku, the oxide film adhesion of the oxide film generated by heating the Cu—Fe—P based copper alloy plate at a higher temperature can be improved.

  In the present invention, the kurtosis (kurtosis) Rku of the roughness curve of the copper alloy plate is a technical element independent of the center line average roughness Ra and the maximum height Rmax. That is, as in the above-described conventional Patent Documents 2 and 3, even when the center line average roughness Ra is 0.2 μm or less and the maximum height Rmax is 1.5 μm or less and the copper alloy plate surface is smoothed, the Rku is In some cases, it may exceed 5.0, and in some cases, Rku may be 5.0 or less.

  In other words, even when the center line average roughness Ra is 0.2 μm or less, the maximum height Rmax is 1.5 μm or less, and the copper alloy plate surface is smoothed, Rku is inevitably less than 5.0. In addition, there is a high possibility that it will come off or become larger. Therefore, even when the center line average roughness Ra is 0.2 μm or less and the maximum height Rmax is 1.5 μm or less, whether or not the Rku of the copper alloy plate surface is 5.0 or less is actually determined by Rku. If it is not measured, it is unclear at all.

  As will be described later, even if the centerline average roughness Ra and the maximum height Rmax are the same, the fact that the Cu-Fe-P-based copper alloy plate is under a higher temperature is affected by the kurtosis (kurtosis) Rku of the roughness curve. This is supported by the fact that a large difference occurs in the oxide film adhesion of the oxide film generated by heating. Further, as will be described later, Rku cannot be controlled to 5.0 or less at the physical processing level such as the surface roughness control of the rolling roll as described in Patent Documents 2 and 3 above, and chemical etching is not performed. This is also supported by the fact that control is possible only after a cleaning process involving the above.

  In the following, the significance and embodiments of each requirement in the Cu—Fe—P based copper alloy sheet of the present invention for satisfying the required characteristics, such as for semiconductor lead frames, will be specifically described.

(Surface roughness)
In the present invention, as a prerequisite for the surface roughness of the Cu—Fe—P-based copper alloy plate, the center line average roughness Ra in the surface roughness measurement according to JIS B0601 method is 0.050 μm or less , and the maximum The height Rmax is 1.5 μm or less.

When the center line average roughness Ra exceeds 0.050 μm or the maximum height Rmax exceeds 1.5 μm, the surface of the Cu—Fe—P-based copper alloy plate is not smooth and is too rough, which is required for the lead frame. Impairs basic properties. That is, it inhibits heat bonding such as Ag paste to the lead frame semiconductor chip, plating treatment such as Au and Ag, soldering or Ag brazing. In addition, it becomes difficult to control the Rku of the Cu—Fe—P-based copper alloy plate surface to be 3.1 or less even by a cleaning process involving chemical etching.

(Rku)
In the present invention, based on the above premise, in order to improve the oxide film adhesion of the oxide film generated by heating the Cu—Fe—P based copper alloy plate at a higher temperature, the surface roughness according to JIS B0601 method is used. In the roughness measurement, the kurtosis (kurtosis) Rku of the roughness curve is 3.1 or less . When Rku exceeds 3.1 , the oxide film adhesion of the oxide film generated by heating the Cu—Fe—P based copper alloy plate at a higher temperature cannot be further improved.

The kurtosis (kurtosis) Rku of the roughness curve is the square mean of the rolling meander curve Z (x) at the reference length lr of the surface of the measurement object in JIS B0601, as shown in the following formula. It is defined as the square root Rq divided by the fourth power.

   As shown in FIG. 1, Rku represents an average parameter of features in the height direction of the surface roughness unevenness curve (rolling circular waviness curve Z (x)).

  When the characteristic in the height direction is kurtosis and Rku is larger than 5.0, as shown in FIG. 1 (a), the surface roughness uneven curve (rolling swell curve Z (x) The curve is sharp or steep. On the other hand, as shown in FIG. 1B, when the Rku is as small as 5.0 or less as in the present invention, the uneven roughness curve of the surface roughness is relatively rounded or a smooth curve. It has become.

  On the other hand, the centerline average roughness Ra, which is widely used as an index of surface roughness, is the average parameter of the height of amplitude in the height direction, in terms of the roughness curve of the surface roughness in FIG. The maximum height Rmax is a parameter of the maximum height of the amplitude in the height direction. Therefore, Rku of the present invention is an independent value regardless of the centerline average roughness Ra and the maximum height Rmax, and as shown in FIGS. 1A and 1B, even if Ra and Rmax are the same, It is understood that Rku differs greatly.

  Further, in JIS B0601, the average parameters of the feature in the height direction include, in addition to Rku, Pku: cross-curve kurtosis (kurtosis), Wku: undulation curve kurtosis (kurtosis), and the like. However, these Pku and Wku are not as highly correlated with the oxide film adhesion of the oxide film produced by heating the Cu-Fe-P-based copper alloy plate at a higher temperature than the Rku of the present invention. For this reason, in the present invention, Rku is selected and defined from the average parameters of the features in the height direction of the surface roughness (curve).

In the present invention, the control of the Cu—Fe—P-based copper alloy sheet surface is first performed at a physical treatment level such as the surface roughness control of the rolling roll, with a center line average roughness Ra of 0.050 μm or less and a maximum. The height Rmax is controlled to 1.5 μm or less. In addition, as will be described later, Rku is set to 3.1 or less by a cleaning process involving chemical etching.

(Component composition of copper alloy sheet)
In the present invention, it is necessary to have basic characteristics such as high strength with a tensile strength of 500 MPa or more and hardness of 150 Hv or more for a semiconductor lead frame. And it has the outstanding plating property which prevents abnormal precipitation of plating, on the assumption that these basic characteristics are not deteriorated while satisfying these basic characteristics. For this reason, the Cu-Fe-P-based copper alloy sheet is in mass%, the Fe content is in the range of 0.01 to 0.50%, and the P content is in the range of 0.01 to 0.15%. The basic composition consisting of the remaining Cu and inevitable impurities.

  You may further selectively contain elements, such as Zn and Sn mentioned later, with respect to this basic composition. Further, elements other than those described (impurity elements) are allowed to be contained within a range that does not impair the characteristics of the present invention. In addition, all the indication% of content of these alloy elements and impurity elements means the mass%.

(Fe)
Fe is a main element that precipitates as Fe or an Fe-based intermetallic compound and improves the strength and heat resistance of the copper alloy. If the Fe content is too small, the precipitation of the compound is insufficient, so the contribution to strength improvement is insufficient, and the improvement in conductivity is satisfied, but even if the final cold rolling is performed on the strong working side, Insufficient strength. On the other hand, if the Fe content is too large, the electrical conductivity is lowered. Furthermore, both strength and heat resistance are reduced. Therefore, the Fe content is 0.01 to 0.50%, preferably 0.15 to 0.35%.

(P)
In addition to deoxidizing action, P is a main element that forms a compound with Fe to increase the strength of the copper alloy. If the P content is too small, the precipitation of the compound is insufficient, so that the contribution to strength improvement is insufficient and the improvement in conductivity is satisfied, but even if the final cold rolling is performed on the strong working side, the strength Is lacking. On the other hand, when there is too much P content, not only electrical conductivity will fall, but hot workability will fall and it will become easy to produce a crack. Therefore, the P content is in the range of 0.01 to 0.15%, preferably 0.05 to 0.12%.

(Zn)
Zn is a selective additive element for improving the heat-resistant peelability of the copper alloy solder and Sn plating necessary for the lead frame and the like, and when these effects are required. If the Zn content is less than 0.005%, the desired effect cannot be obtained. On the other hand, if it exceeds 3.0%, not only the solder wettability is lowered but also the conductivity is greatly lowered. Therefore, the Zn content in the case of selective inclusion is 0.005 to 3 depending on the balance between the electrical conductivity required for the application and the heat resistance peelability of the solder and Sn plating (in consideration of the balance). It is supposed to be contained selectively from the range of 0.0%.

(Sn)
Sn contributes to improving the strength of the copper alloy, and is a selective additive element when these effects are necessary. When the Sn content is less than 0.001%, it does not contribute to high strength. On the other hand, when the Sn content is increased, the effect is saturated, and conversely, the conductivity is lowered. Accordingly, the Sn content in the case of selective inclusion is in the range of 0.001 to 5.0% depending on the balance between strength (hardness) and conductivity required for the application (in consideration of the balance). To be selectively contained.

(Mn)
Since Mn contributes to the improvement of the hot workability of the copper alloy, it is selectively contained when these effects are required. The Mn content is 0 . If it is less than 0001%, the desired effect cannot be obtained. On the other hand, the content is 1 . If it exceeds 0%, coarse crystallized products and oxides are generated to reduce the strength and heat resistance, and the electrical conductivity is also greatly reduced. Therefore, the Mn content is 0 . It is contained selectively in the range of 0001 to 1.0%.

(Co, Ni)
Since these components have an effect of improving the strength of the copper alloy, they are selectively contained when these effects are required. The content of these components is 0 . If it is less than 001%, the desired effect cannot be obtained. On the other hand, the content is 1 . If it exceeds 0%, coarse crystallized products and oxides are produced, which not only lowers the strength and heat resistance but also causes a significant decrease in conductivity, which is not preferable. Therefore, the content of these elements is 0 . It is contained selectively in the range of 001 to 1.0%. Incidentally, these components, when containing both the above M n, the total content of elements such content is 1.0% or less.

(Hf, Th, Li, Na, K, Sr, Pd, W, Si, Nb, Al, V, Y, Mo, In, Ga, Ge, As, Sb, Bi, Te, B, Misch metal)
These components are impurity elements, and when the total content of these elements exceeds 0.1%, coarse crystallized products and oxides are formed, and the strength and heat resistance are lowered. Therefore, the total content of these elements is preferably 0.1% or less.

(Production conditions)
Next, preferable manufacturing conditions for making the copper alloy sheet structure the structure defined in the present invention will be described below. The copper alloy sheet of the present invention is the same as the usual method, except that the usual manufacturing process itself is not greatly changed except for the preferred cold rolling and cleaning conditions described later for controlling Ra, Rmax, and Rku of the surface. Can be manufactured.

  That is, first, a molten copper alloy adjusted to the preferred component composition is cast. Then, after chamfering the ingot, it is heated or homogenized and then hot-rolled, and the hot-rolled plate is water-cooled. This hot rolling may be performed under normal conditions.

  After that, the first cold rolling, which is said to be intermediate, is annealed, washed, and then finished (final) cold rolled and low-temperature annealed (final annealing, final annealing) to obtain a copper alloy sheet having a product thickness. . These annealing and cold rolling may be repeated. For example, in the case of a copper alloy plate used for a semiconductor material such as a lead frame, the product plate thickness is about 0.1 to 0.4 mm.

  In addition, you may perform the solution treatment of a copper alloy plate, and the quenching process by water cooling before primary cold rolling. At this time, the solution treatment temperature is selected from a range of 750 to 1000 ° C., for example.

(Final cold rolling)
Final cold rolling is also according to conventional methods. In order to obtain a high strength with a tensile strength of 500 MPa or more and a hardness of 150 Hv or more in a Cu—Fe—P based copper alloy plate having a large limit in the content of the solid solution strengthening element, In relation to the processing rate, the processing rate of the final cold rolling is determined on the strong processing side.

  In addition, it is preferable that the minimum rolling reduction (cold rolling ratio) per pass of final cold rolling shall be 20% or more. If the minimum reduction rate per pass of final cold rolling is lower than 20%, the plate thickness distortion becomes large and bending workability deteriorates.

However, during this final cold rolling, it is used to control the center line average roughness Ra of the Cu—Fe—P based copper alloy sheet surface to 0.050 μm or less and the maximum height Rmax to 1.5 μm or less. The surface roughness of the rolling roll is controlled.

Specifically, a bright roll (with a roll roll surface roughness finely divided into a center line average roughness Ra: 0.050 μm or less and a maximum height Rmax: 1.5 μm or less in the same manner as the surface of the rolled copper alloy sheet. Use a surface polishing roll).

(Final annealing)
Cu-Fe-P copper alloy sheets whose surface is controlled to a center line average roughness Ra of 0.050 μm or less and a maximum height Rmax of 1.5 μm or less by final cold rolling are subjected to final annealing at a low temperature. It is preferable to carry out in a continuous heat treatment furnace. The final annealing condition in this continuous heat treatment furnace is preferably a low temperature condition of 0.2 to 300 minutes at 100 to 400 ° C. In the manufacturing method of the copper alloy plate used for a normal lead frame, since the strength is lowered, the final annealing is not performed after the final cold rolling except for annealing for removing strain (about 350 ° C. × 20 seconds). However, in the present invention, this strength reduction is suppressed by the cold rolling conditions and by lowering the final annealing. And bending workability etc. improve by performing final annealing at low temperature.

  Under conditions where the annealing temperature is lower than 100 ° C, the annealing time is less than 0.2 minutes, or the conditions where this annealing is not performed, the structure and properties of the copper alloy sheet are almost the same as those after the final cold rolling. It is likely that it will not change. Conversely, if annealing is performed at a temperature exceeding 400 ° C. or annealing time exceeding 300 minutes, recrystallization occurs, rearrangement of dislocations and recovery phenomenon occur excessively, and precipitates also become coarse. For this reason, there is a high possibility that the press punchability and the strength are lowered.

(Cleaning process)
After this final annealing, the surface of the Cu—Fe—P-based copper alloy plate is controlled to have a Rku of 3.1 or less by a cleaning process involving chemical etching. For this cleaning treatment, a commercially available cleaning agent can be appropriately used as long as the Rku can be 3.1 or less and the cleaning treatment involves chemical etching.

However, as a means to ensure that Rku is 3.1 or less , a cleaning process involving acid etching, in which a copper alloy plate is immersed in a sulfuric acid aqueous solution (room temperature) having a concentration of 5 to 50% by mass for 1 to 60 seconds. preferable. If the sulfuric acid concentration is less than 5% by mass and the immersion time is less than 1 second, cleaning or etching of the surface of the mother phase is insufficient, and there is a high possibility that Rku cannot be made 3.1 or less . On the other hand, even if the sulfuric acid concentration is 50% by mass and the immersion time exceeds 60 seconds, it is highly possible that the cleaning or etching of the surface of the mother phase is not uniform, and that Rku cannot be reduced to 3.1 or less .

  Examples of the present invention will be described below. As shown in Table 2, Cu—Fe—P-based copper alloy thin plates having respective chemical component compositions shown in Table 1 were produced by changing only the cleaning treatment conditions involving chemical etching after the final annealing. And the adhesiveness (peeling temperature of an oxide film) of the oxide film of each copper alloy thin plate was evaluated. These results are shown in Table 2.

  Specifically, after each copper alloy having the chemical composition shown in Table 1 was melted in a coreless furnace, it was ingoted by a semi-continuous casting method, and the ingot was 70 mm thick × 200 mm wide × 500 mm long. Got. Each ingot was chamfered on the surface and heated, and then hot rolled at a temperature of 950 ° C. to form a plate having a thickness of 16 mm, and rapidly cooled into water from a temperature of 750 ° C. or higher. Next, after removing the oxide scale, primary cold rolling (intermediate rolling) was performed. After this plate is cut, it is subjected to final cold rolling with 4 passes of cold rolling with intermediate annealing, followed by final continuous annealing at 350 ° C for 20 seconds at low temperature to support thinning of the lead frame. A copper alloy plate having a thickness of 0.15 mm was obtained.

  At this time, the final cold rolling is common to each example, the minimum rolling reduction per pass is set to 30%, the roll surface has a center line average roughness Ra: 0.2 μm or less, and a maximum height Rmax: A bright roll (surface polishing roll) made finer to 1.5 μm or less was used.

  In addition, after the final continuous annealing, a Cu—Fe—P-based copper alloy plate is immersed in a sulfuric acid aqueous solution (room temperature) under the conditions shown in Table 2, and is subjected to a cleaning process with acid etching, and Cu—Fe— Rku on the surface of the P-based copper alloy plate was controlled.

  In each of the copper alloys shown in Table 1, the remaining composition excluding the described element amount is Cu, and other impurity elements are Hf, Th, Li, Na, K, Sr, Pd, W, S, Si, The content of C, Nb, Al, V, Y, Mo, Pb, In, Ga, Ge, As, Sb, Bi, Te, B, and misch metal is 0.1% by mass or less in total of these elements. Met.

When Mn is included, 0 . In the case of containing Co and Ni , the range of 0 . The total amount of these elements was also set to 1.0% by mass or less.

  For each copper alloy plate obtained as described above, in each example, a sample was cut out from the copper alloy plate, and the characteristics such as tensile strength, hardness, conductivity, etc. of each copper alloy thin plate, JIS B0601 The center line average roughness Ra, the maximum height Rmax, and the kurtosis (kurtosis) Rku of the roughness curve in the surface roughness measurement according to the method were measured. These results are shown in Table 2, respectively.

(Measurement of surface roughness)
Using a surface roughness measuring instrument (product name: Surfcom 1400D) manufactured by Tokyo Seimitsu Co., Ltd., the center line average roughness Ra (μm) and maximum height Rmax (μm) of the surface of the test piece of the obtained copper alloy plate ), Kurtosis (kurtosis) Rku of the roughness curve was measured according to JIS B0601 method. The measurement was performed 4.0 mm in length at three arbitrary points (three places) on the test piece, and the results were averaged.

(Hardness measurement)
A 10 × 10 mm test piece was cut out from the obtained copper alloy plate, and a load of 0.5 kg was applied using a micro Vickers hardness meter (trade name “micro hardness meter”) manufactured by Matsuzawa Seiki Co., Ltd. Measurement was performed, and the hardness was an average value thereof.

(Conductivity measurement)
The electrical conductivity of the copper alloy plate sample was calculated by an average cross-sectional area method by processing a strip-shaped test piece having a width of 10 mm and a length of 30 mm by milling, measuring the electrical resistance with a double bridge resistance measuring device.

(Oxide film adhesion)
Further, the oxide film adhesion test of each test material was evaluated by a tape peeling test at a limit temperature at which the oxide film peeled off. In the tape peeling test, a 10 × 30 mm test piece is cut out from the copper alloy plate obtained as described above, heated at a predetermined temperature in the atmosphere for 5 minutes, and then a commercially available tape is formed on the surface of the test piece on which the oxide film is formed. (Product name: Sumitomo 3M Mending Tape) was applied and peeled off. At this time, when the heating temperature was changed in increments of 10 ° C., the lowest predetermined temperature at which the oxide film was peeled off was obtained, and this was set as the oxide film peeling temperature.

  When the oxide film peeling temperature is 350 ° C. or higher, it can be said that the oxide film adhesion is necessary (sufficient) for increasing the heating temperature in the heating process for manufacturing a copper alloy plate or a lead frame.

  In addition, the heating for 5 minutes in the atmosphere of the present invention is a relatively long heating time, as in Patent Documents 2 and 3, oxidation is performed at 200 to 500 ° C. for a relatively short time of 3 minutes. It can be said that it is severer than the film adhesion evaluation test conditions. In other words, the oxide film adhesion test of the present invention, which has a relatively long heating time, corresponds to (correlates with) the oxide film adhesion at a higher heating temperature in the heating process for the production of copper alloy plates and lead frames. ing.

  On the other hand, in the oxide film adhesion evaluation test conditions for performing heating for a relatively short time of 3 minutes as in Patent Documents 2 and 3, in the heating process for manufacturing a copper alloy plate or a lead frame. It can be said that the correspondence (correlation) to the oxide film adhesion with the heating temperature is insufficient. In other words, even if the results of the evaluation test conditions for oxide film adhesion in Patent Documents 2 and 3 are good, the oxide film adhesion is good when the heating temperature is increased in the heating process for manufacturing a copper alloy plate or a lead frame. Not necessarily.

Tables 1 and 2 is apparent from Examples Ru copper alloy der in the present invention compositions 1 to 13, a tensile strength of at least 500 MPa, hardness is high strength of at least 150 Hv. Moreover, the center line average roughness Ra in the surface roughness measurement according to JIS B0601 method of this copper alloy plate is 0.2 μm or less, and the maximum height Rmax is 1.5 μm or less. However, in Tables 1 and 2, the inventive examples are only the inventive examples 4, 6, 8, 10, and 11 in which Ra is 0.050 μm or less, Rmax: 1.5 μm or less, and Rku is 3.1 or less. The other examples 1, 2, 3, 5, 7, 9, 12, and 13 described in Tables 1 and 2 are all reference examples.

Invention Examples 4, 5, 8, 10, and 11 are in comparison with other reference examples 2, 3, 5, 7, 9, 12, and 13 in which Ra exceeds 0.050 μm and Rku exceeds 3.1. In addition, the oxide film peeling temperature is 390 ° C. to 410 ° C. , which has better oxide film adhesion. Therefore, the invention example has high adhesiveness between the resin and the die pad when assembling the semiconductor package as a semiconductor base material, and the reliability of the package is high.

  On the other hand, Comparative Examples 14 and 15 do not perform the cleaning treatment with the sulfuric acid aqueous solution under the preferable conditions after the final continuous annealing. In Comparative Example 16, the sulfuric acid concentration in the washing treatment with the sulfuric acid aqueous solution is too low. In Comparative Example 17, the sulfuric acid concentration in the washing treatment with the sulfuric acid aqueous solution is too high. In Comparative Example 18, the immersion time of the cleaning treatment with this sulfuric acid aqueous solution is too long. As a result, in Comparative Examples 14 to 18, the kurtosis (kurtosis) Rku of the roughness curve exceeds 5.0.

  On the other hand, Comparative Examples 14 to 18 are copper alloys within the composition of the present invention, which have a high strength with a tensile strength of 500 MPa or more and a hardness of 150 Hv or more, and a centerline average roughness Ra in surface roughness measurement of 0. .2 μm or less and the maximum height Rmax is 1.5 μm or less. Nevertheless, since Comparative Examples 14 to 18 have a kurtosis (kurtosis) Rku of the roughness curve exceeding 5.0, the oxide film peeling temperature is less than 350 ° C. and the oxide film adhesion is poor. Therefore, Comparative Examples 14 to 18 have a low adhesiveness between the resin and the die pad when the semiconductor package is assembled as a semiconductor base material, and the reliability of the package is also low.

  Since Comparative Examples 19-22 performed the washing process by sulfuric acid aqueous solution on the preferable conditions after the last continuous annealing, the kurtosis (kurtosis) Rku of the roughness curve is 5.0 or less, and excellent oxide film adhesion Have.

  Nevertheless, in Comparative Example 19, the Fe content falls below the lower limit of 0.01%, the strength level is low, and it cannot be used as a semiconductor base material.

  In Comparative Example 20, the Fe content deviates from the upper limit of 5.0%, the conductivity is extremely low, and it cannot be used as a semiconductor base material.

  In Comparative Example 21, the P content deviates slightly from the lower limit of 0.01%, the strength level is low, and it cannot be used as a semiconductor base material.

  In Comparative Example 22, since the P content was higher than the upper limit of 0.15% and cracking occurred during hot rolling, the trial production was stopped at that time.

  Based on the above results, the component composition of the copper alloy sheet of the present invention, the critical significance of the surface roughness definition, and the surface roughness are obtained in order to have excellent oxide film adhesion after increasing the strength. Therefore, the significance of preferable production conditions for the above is supported.

  As described above, according to the present invention, it is possible to provide a Cu—Fe—P-based copper alloy plate that is excellent in oxide film adhesion and has both of these characteristics (combined) while having high strength. Can do. As a result, it is possible to provide a semiconductor base material having high adhesion between the resin and the die pad during assembly of the semiconductor package and high package reliability. Therefore, for electrical and electronic parts that are reduced in size and weight, in addition to lead frames for semiconductor devices, lead frames, connectors, terminals, switches, relays, etc. have increased strength and oxide film adhesion = package reliability. Can be applied to applications that require.

It is explanatory drawing which shows the kurtosis (kurtosis degree) Rku of the roughness curve in the copper alloy board surface roughness prescribed | regulated by this invention.

Claims (6)

  It is a copper alloy plate containing Fe: 0.01 to 0.50%, P: 0.01 to 0.15%, and the balance Cu and unavoidable impurities, and has a tensile strength of 500 MPa or more. The hardness is 150 Hv or more, the center line average roughness Ra in the surface roughness measurement according to JIS B0601 method of this copper alloy plate is 0.050 μm or less, and the maximum height Rmax is 1.5 μm or less, and A high-strength copper alloy plate excellent in oxide film adhesion, characterized in that the kurtosis (kurtosis) Rku of the roughness curve is 3.1 or less. The high-strength copper alloy plate according to claim 1 , wherein the copper alloy plate further contains Zn: 0.005 to 3.0% by mass . The high-strength copper alloy plate according to claim 2 , wherein the copper alloy plate further contains Sn: 0.005 to 5.0% by mass . The high-strength copper alloy plate according to claim 2 , wherein the copper alloy plate further contains Co: 0.001 to 1.0% by mass% . The high-strength copper alloy plate according to claim 3 , wherein the copper alloy plate further contains, by mass%, Mn: 0.0001 to 1.0% and Ni: 0.001 to 1.0% . The high-strength copper alloy plate according to any one of claims 1 to 5 , wherein the copper alloy plate is for a semiconductor lead frame .

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