Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/02—Alloys based on copper with tin as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B15/00—Obtaining copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/04—Alloys based on copper with zinc as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
  • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
  • H01L23/495—Lead-frames or other flat leads
  • H01L23/49579—Lead-frames or other flat leads characterised by the materials of the lead frames or layers thereon
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

• the invention relates to a copper alloy having high strength and high softening resistance, such as a copper alloy suitable for use as a constituent material of a lead frame for a semiconductor device.
• the copper alloy according to the invention is for use not only as the constituent material of the lead frame, but also as constituent materials of electrical and electronic parts such as semiconductor parts, other than the lead frame for the semiconductor device, a printed wiring board, and so forth, constituent materials of other electrical and electronic parts such as mechanical parts including a switch, bus bar, terminal, connector, and the like.
• the copper alloy being used for a lead frame as a semiconductor part, in particular, will be primarily described as a representative application example.
• a Cu—Fe—P alloy As a copper alloy for use in an IC lead frame, a Cu—Fe—P alloy has been commonly employed in the past.
• the Cu—Fe—P alloy include a copper alloy containing 0.05 to 0.15% Fe, and 0.025 to 0.04% P (C19210 alloy), and a copper alloy containing 2.1 to 2.6% Fe, 0.015 to 0.15% P, and 0.05 to 0.20% Zn (CDA194 alloy). If Fe or an inter-metallic compound such as Fe—P or the like is precipitated in a copper matrix phase, those Cu—Fe—P alloys are found superior among copper alloys in terms of strength, electrical conductivity, and thermal conductivity, so that those Cu—Fe—P alloys are commonly used as the international standard alloys.
• Cu—Fe—P alloy sheets having higher strength, and higher electrical conductivity are required to have excellent softening resistance hardly causing deterioration in strength even after application of heat treatment such as stress relief annealing or the like.
• Patent Document 2 it has been proposed to obtain a high softening resistance by controlling structures themselves of crystals and precipitates, in a Cu—Fe—P alloy with effective Fe content as high as not lower than 0.7%. Further, in Patent Documents 3, and 4, it has been proposed to obtain a high softening resistance by controlling aggregate structures.
• Patent Document 1 JP-B No. 3725506
• Patent Document 2 JP-A No. 91895/2004
• Patent Document 3 JP-A No. 139501/2005
• the softening resistance of a copper alloy can be enhanced if the additive elements such as Sn, and so forth, in relatively large amounts, are contained in the copper alloy.
• the Cu—Fe—P alloy contains the additive elements such as Sn, and so forth, in large amounts, the Cu—Fe—P alloy will be prone to undergo cracking at the time of forging and hot rolling, due to excessive segregation (presence) of a large amount Sn, on grain boundaries.
• the invention has been developed to resolve such problems as described in the foregoing, and it is therefore an object of the invention to provide a Cu—Fe—P alloy having both high strength and high softening resistance.
• the invention provides a copper alloy having both high strength and high softening resistance, essentially containing Fe in a range of 0.01 to 4.0 mass %, P in a range of 0.01 to 0.15 mass %, Sn in excess of 0.5 mass %, not higher than 5.0 mass %, and at least one element selected from the group consisting of Ni, Mg, Ca, Al, Si, and Cr, in a range of 0.001 to 0.02 mass %, in total, the remainder being Cu and unavoidable impurities, wherein a ratio of an amount of Fe in extracted residue that is extracted and separated over a filter 0.1 ⁇ m in opening size by an extracted residue method to an amount of Fe contained in the copper alloy is more than 80%.
• the extracted residue method described as above comprises the steps of:
• the amount of Fe in the extracted residue is found by dissolving the undissolved residue on the filter into a solution prepared by mixing aqua regia with water at a ratio of 1 to 1 to be subsequently analyzed by the ICP emission spectroscopy.
• Fe content is preferably in a range of 0.01 to 0.5% in the case of the chemical composition of the copper alloy having both high strength and high softening resistance, in particular, including the Fe content in a relative low region.
• a Cu—Fe—(P, Zn) alloy in particular, preferably further contains Zn in a range of 0.005 to 3.0%.
• those copper alloys each are preferably in the form of a copper alloy sheet for use as an IC lead frame.
• the copper alloy according to the invention has a feature in that a relatively large amount of Sn is contained therein in order to enhance softening resistance.
• Patent Document 1 has disclosed that if a Cu—Fe—P alloy contains an excessively large amount of Sn, this will cause formation of coarse compounds at the time of forging, due to macro-segregation of Sn while causing deterioration in electrical conductivity.
• Sn is large in atomic radius as compared with Cu and is also faster in diffusion, so that Sn has difficulty in being present within Cu matrix and Cu grains, but is prone to be present on the grain boundaries. Accordingly, it is presumed that if a Cu—Fe—P alloy contains a large amount of Sn, this will reinforce the excessive segregation of Sn, on the grain boundaries, thereby rendering the Cu—Fe—P alloy susceptible to cracking at the time of forging and hot rolling.
• the invention has another feature in that the Cu—Fe—P alloy containing a relatively large amount of Sn is caused to further contain Ni, Mg, Ca, Al, Si, and Cr, in trace amounts.
• Those elements Ni, Mg, Ca, Al, Si, and Cr, contained in trace amounts will be present on the grain boundaries, in more preference to Sn or in preference to Sn to an equivalent degree thereto. Consequently, the excessive segregation (presence) of the large amount of Sn, on the grain boundaries, can be suppressed. Meanwhile, as those elements, in small amounts, are contained in the copper alloy, even if those elements are present on the grain boundaries, this will not foster cracking at the time of forging and hot rolling.
• the copper alloy according to the invention is capable of containing a relatively large amount of Sn, in addition to checking cracking at the time of forging, and hot rolling, and of enhancing softening resistance. Furthermore, such an advantageous effect of enhanced softening resistance will not be dependent on Fe content unlike the case of the conventional technology for enhancing softening resistance, and can be exhibited even in the case of the Cu—Fe—P alloy with Fe content in a relative low region not higher than 0.5%
• the copper alloy according to the embodiment of the invention is a copper alloy having composition of Fe in a range of 0.01 to 4.0 mass %, P in a range of 0.01 to 0.15 mass %, Sn in excess of 0.5 mass %, not higher than 5.0 mass %, and at least one element selected from the group consisting of Ni, Mg, Ca, Al, Si, and Cr, in a range of 0.001 to 0.02 mass %, in total, the remainder being Cu and unavoidable impurities, in order to meet strength, and electrical conductivity, representing basic properties necessary for use in an IC lead frame, and so forth, together with softening resistance.
• the copper alloy needs to have tensile strength not less than 600 MPa, and electrical conductivity not less than 20% IACS.
• the copper alloy may contain selective additive elements and impurity elements, other than that, within a range where the basic properties as described are not adversely affected. Further, the following element contents are all expressed in terms of mass %.
• Fe is precipitated as Fe or a Fe-group intermetallic compound, and is a primary element for enhancing the strength and softening resistance of a copper alloy. If Fe content is less than 0.1%, a formation mount of Fe precipitate grains is less, so that contribution thereof, to enhancement of strength, is insufficient although the need for enhancement of electrical conductivity is met, resulting in insufficient strength.
• the upper limit of Fe content is preferably 0.5% as composition in a low Fe content region of the copper alloy according to the invention, particularly having high strength and high softening resistance.
• the upper limit of Fe content is set to not higher than 3.0%, preferably not higher than 0.5% while essential Fe content is in a range of 0.01 to 3.0%, preferably in a range of 0.01 to 0.5%.
• Sn is an element contributing to enhancement in the strength and softening resistance of the copper alloy. If Sn content is not higher than 0.5%, Sn does not contribute to higher strength and higher softening resistance. Meanwhile, if Sn content is in excess of 5%, being excessively high, it becomes impossible to suppress excessive segregation (presence) of contained Sn, on grain boundaries, because of an excessive amount of Sn even when Ni, Mg, Ca, Al, Si, and Cr, in trace amounts, are contained. Accordingly, essential Sn content is set to fall in a relatively wide range exceeding 0.5%, not higher than 5.0%.
• elements Ni, Mg, Ca, Al, Si, and Cr, in small amounts, are contained, the elements will be present on grain boundaries in more preference to Sn or in preference to Sn to an equivalent degree thereto. Consequently, the excessive segregation (presence) of the large amount of Sn, on the grain boundaries, as previously described, can be suppressed, and cracking can thereby be suppressed at the time of forging and hot rolling. Since a series of those elements, in small amounts, are contained in the copper alloy, even if those elements are present on the grain boundaries, this will not foster cracking at the time of forging and hot rolling.
• P is an essential element for increasing the strength of a copper alloy by reacting with Fe to thereby form a compound besides having the function of deoxidizing the copper alloy in molten state. If P content is lower than 0.01%, the compound is insufficiently precipitated depending on a production condition, so that a desired strength cannot be obtained, and an advantageous effect of the copper alloy containing P will be lost. On the other hand, if P content becomes higher, exceeding 0.3%, this will cause not only electrical conductivity but also rolling workability to deteriorate. Accordingly, P content is set to a range of 0.01 to 0.3%.
• Zn is an element for improving resistance to thermal releasability of solder and Sn plating of the copper alloy, necessary for the lead frame or the like. If Zn content when Zn is selectively contained is lower than 0.005%, a desired advantageous effect cannot be obtained. On the other hand, if Zn content is in excess of 3.0%, not only wettability will deteriorate but also deterioration in electrical conductivity will increase. Accordingly, Zn content when Zn is selectively contained is set to a range of 0.005 to 3.0%.
• metal elements other than the above-described are basically impurities. However, not only pure copper ingot but also scrap of electronic part material is nowadays used as raw material to be melted. In such cases, there are times when other metal materials resulting from combination of plating components with the copper alloy components are unavoidably mixed into the copper alloy (in molten state) according to the invention. Accordingly, with the invention, the content of the other metal elements prone to be mixed, other than the above-described, is specified as tolerance (the upper limit value) below which the advantageous effects of the invention are not adversely affected.
• Those elements even have an advantageous effect of enhancing the strength of the copper alloy.
• the content thereof is excessively high, this also will cause coarse crystals and oxides to be prone to occur, and deterioration in electrical conductivity also will be considerable.
• an Fe-base compound such as an Fe-base oxide, a Fe-base precipitate, and so forth, produced due to Fe contained in the copper alloy, is controlled in size. More specifically, while a ratio of a coarse Fe-base compound (referred to also as a coarse product), making no contribution to enhancement in the strength of the copper alloy, is lowered as much as possible, a ratio of a fine Fe-base compound (referred to also as a fine product), making effective contribution to enhancement in the strength of the copper alloy, is raised as much as possible.
• a ratio of a coarse Fe-base compound referred to also as a coarse product
• a fine Fe-base compound referred to also as a fine product
• the Fe-base oxide, and the Fe-base precipitate refer to an Fe-containing oxide, and Fe-containing precipitate or mixtures thereof, respectively, regardless of chemical composition thereof.
• the Fe-containing precipitate includes, for example, an Fe particle, and a compound including Fe and P (Fe 3 P, F 2 P, and so forth).
• a size boundary of the Fe-base compound is 0.1 ⁇ m. More specifically, the Fe-base compound not less than 0.1 ⁇ m in size, separated by an extracted residue method described below, using a filter 0.1 ⁇ m in opening size, is defined as the coarse Fe-base compound. And, an amount of the Fe-base compound not less than 0.1 ⁇ m in size, as the coarse Fe-base compound, is defined as an amount of Fe in extracted residue that is extracted and separated over the filter 0.1 ⁇ m in opening size. Then, a ratio of the amount of Fe in the extracted residue to an amount of Fe contained in the copper alloy is found, which is defined the ratio of the coarse Fe-base compound (the coarse product).
• the ratio (percentage) of the amount of Fe in the extracted residue that is extracted and separated over the filter 0.1 ⁇ m in opening size by the extracted residue method described below to the amount of Fe contained in the copper alloy is specified to be not more than 80%.
• a level of electrical conductivity is substantially dependent on Cu purity, that is, an amount of the additive elements and the alloying elements, contained in the copper alloy, however, the level of electrical conductivity is largely affected by respective solid solution amounts of the alloying elements, and an amount of work strain due to cold rolling, even in the case of an identical chemical composition.
• a finished sheet is obtained by repeatedly applying cold rolling, and annealing after execution of forging, soaking, and hot rolling.
• Control of mechanical properties such as strength level, and so forth is implemented primarily by controlling precipitation of fine precipitates not more than 0.1 ⁇ m through adjustment of a hot rolling condition, and an annealing condition.
• a solid solution amount of Fe, and so forth, and a precipitation amount of the fine precipitates can be stabilized by diffusion of the alloying elements, such as Fe, and so forth, into adequately dispersed intermetallic compounds.
• the undissolved residue (extracted residue) on the filter is dissolved into a solution prepared by mixing aqua regia with water at a ratio of 1 to 1 to be subsequently analyzed by the ICP emission spectroscopy, thereby finding the amount of Fe in the extracted residue.
• a molten copper alloy adjusted so as to have the chemical composition described as above is cast.
• Forging is executed by a common method such as a continuous forging method, a semicontinuous forging method, and so forth, and the forging is preferably executed at an average cooling rate (solidifying rate) in excess of 5.0° C./sec for a period from the start of the forging up to a time when 600° C. is reached.
• an average cooling rate solidifying rate
• the average cooling rate does not normally exceed 5.0° C./sec during the period from the start of the forging up to the time when 600° C. is reached. If the average cooling rate (solidifying rate) is as slow as less than 5.0° C./sec, oxides are generated on the grain boundaries to thereby turn coarser, and crystals also turn coarser, which is not preferable. From the viewpoint of checking the generation of the oxides, it is more preferable to execute vacuum melting•forging, or melting•forging in an atmosphere of a low partial pressure of oxygen.
• the ingot After the ingot is heated in a heating furnace, the ingot is taken out of the furnace, and is subjected to roughing to be subsequently heated or heat treated for homogenization, followed by hot rolling, whereupon a hot-rolled sheet is water-cooled.
• the hot rolling may be executed according to the common method with a start temperature on the order of 1000 to 600° C., and a completion temperature on the order of 600 to 850° C.
• the hot-rolled sheet is subjected to a primary cold rolling called intermediate rolling before annealing and cleaning, and is further subjected to a finishing (final) cold rolling, and a low temperature annealing (final annealing, finish annealing), thereby being worked into a copper alloy sheet with a product sheet-thickness.
• a primary cold rolling called intermediate rolling before annealing and cleaning
• finishing (final) cold rolling and a low temperature annealing (final annealing, finish annealing)
• final annealing, finish annealing final annealing, finish annealing
• the product sheet-thickness is on the order of 0.1 to 0.4 mm.
• a solution heat treatment, and a hardening treatment by water-cooling may be applied to the copper alloy sheet.
• a temperature for the solution heat treatment is selected within a range of 750 to 1000° C.
• Cu—Fe—P alloys of respective chemical compositions shown in Table 1 were melted in a core-less furnace, respectively, to be subsequently subjected to ingot forging by the semicontinuous forging method, whereupon ingots each 70 mm (thickness) ⁇ 200 mm (width) ⁇ 500 mm (length) were obtained.
• ingots each 70 mm (thickness) ⁇ 200 mm (width) ⁇ 500 mm (length) were obtained.
• hot rolling at 950° C. were applied to the respective ingots to be reduced into a hot rolled sheet 16 mm thick, respectively, and the respective hot rolled sheets were quenched in water from a temperature not lower than 750° C.
• chemical composition of the remainder thereof, after removing elements described in Table 1, include Cu and unavoidable impurities, and elements Mn, Zr, Ag, Cd, Be, Ti, Co, S, Au, Pt, Pb, Bi, and Sb, measured as the unavoidable impurities, were found at 0.003 mass % in total.
• a test specimen was sampled from respective Cu—Fe—P alloy sheets obtained, and a ratio (percentage: %) of an amount of Fe contained in extracted residue to an amount of Fe contained in the respective copper alloys was found by the extracted residue method, and the method of measuring the amount of Fe in the extracted residue, as previously described.
• test specimen was sampled from the respective Cu—Fe—P alloy sheets obtained, and was subjected to a tensile test, hardness measurement, and electrical conductivity measurement.
• Hardness measurement on the test specimens of the respective Cu—Fe—P alloy sheets was conducted by applying a load of 0.5 kg at three spots with the use of a micro-Vickers hardness tester (trade name: micro hardness tester) manufactured by Matsuzawa Precision Machinery Co., Ltd, and a mean value of hardness values obtained was defined as hardness.
• test specimens of the respective Cu—Fe—P alloy sheets were reduced into a short-strip-like shape 10 mm (width) ⁇ 300 mm (length), respectively, by milling, and electrical resistance of the test specimen was measured by use a double-bridge type resistance measurement meter, whereupon electrical conductivity was worked out by the average sectional area method.
• Softening resistance of respective test specimens was evaluated on the basis of a degree of deterioration in hardness, due to annealing.
• the respective test specimens ⁇ 10 mm (width) ⁇ 10 mm (length) ⁇ were optionally sampled from respective sheets obtained by annealing respective product copper alloy sheets after the final cold rolling and after the final low-temperature annealing, at 500° C. for one minute, before water cooled.
• Hardness measurement on the respective test specimens was conducted by applying a load of 0.5 kg with the use of a micro-Vickers hardness tester (trade name: micro hardness tester) manufactured by Matsuzawa Precision Machinery Co., Ltd.
• comparative examples 9 to 11 each had prerequisite composition of Fe, Sn, P, Zn, falling within respective ranges according to the invention, however, did not contain at least one element selected from the group consisting of Ni, Mg, Ca, Al, Si, and Cr. Consequently, many cracks occurred thereto at the time of forging and hot rolling during the production process for those copper alloys.
• the invention can provide a Cu—Fe—P alloy wherein high strength, and excellent softening resistance can coexist.
• the invention is applicable to various usage requiring high strength, high electrical conductivity, and high softening resistance, including electrical and electronic parts reduced in size and weight, such as an IC lead frame, and parts other than the lead frame, including a connector, terminal, switch, relay, and the like.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Conductive Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=38294110

Family Applications (1)

Country Status (5)

Cited By (11)

Families Citing this family (14)

Citations (4)

Family Cites Families (11)

• 2006
  • 2006-07-28 JP JP2006206672A patent/JP4950584B2/ja not_active Expired - Fee Related
• 2007
  • 2007-05-31 US US11/756,117 patent/US20080025867A1/en not_active Abandoned
  • 2007-06-13 EP EP07011610A patent/EP1882751A1/en not_active Withdrawn
  • 2007-06-26 CN CNA2007101262374A patent/CN101113499A/zh active Pending
  • 2007-07-27 KR KR1020070075530A patent/KR100997287B1/ko active IP Right Grant

Patent Citations (4)

Also Published As

Similar Documents

Legal Events