Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/1601—Process or apparatus
  • C23C18/1633—Process of electroless plating
  • C23C18/1646—Characteristics of the product obtained
  • C23C18/165—Multilayered product
  • C23C18/1651—Two or more layers only obtained by electroless plating
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/42—Coating with noble metals
  • C23C18/44—Coating with noble metals using reducing agents

Definitions

• the present invention relates to an electroless palladium plating solution and an electroless palladium plating film.
• electroless nickel electroless palladium immersion gold which can add an effect of being excellent in plating film properties such as solder bondability and wire bondability, is commonly used as a method for treating a surface of a circuit of a printed board, or a mounting portion or a terminal portion of an IC package.
• Ni plating film an electroless nickel plating film
• Pd plating film electroless palladium plating film
• Ad plating film an immersion gold plating film
• plating film properties are improved by, for example, modifying an electroless palladium plating solution (hereinafter, sometimes referred to as an "electroless Pd plating solution") in order to secure plating film properties required with miniaturization and enhanced density of electronic components.
• electroless Pd plating solution an electroless palladium plating solution
• Patent Document 1 discloses an electroless Pd plating solution in which as a stabilizer, bismuth or a bismuth compound is used instead of a sulfur compound, resulting in formation of an electroless Pd plating film which has bath stability as high as that achieved with a sulfur compound, and is excellent in corrosion resistance, solder bondability and wire bondability.
• Patent Document 1 JP4596553B1
• Electroless Ni/Pd/Au plating films which are commonly used exhibit excellent wire bondability before being exposed to a high-temperature thermal history in reflow treatment or the like, but has the problem that wire bondability is significantly deteriorated after the high-temperature thermal history.
• the present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide an electroless Pd plating solution which enables formation of a Pd plating film forming a plating film having excellent wire bondability even after a high-temperature thermal history; and a Pd plating film.
• Preferable embodiment of the present inventive electroless Pd plating solution includes any combination of the following options (i) to (iii).
• the present invention includes an electroless Pd plating film containing phosphorus; and boron.
• Preferable embodiment of the present invention includes a laminated film including the electroless Pd plating film and a gold plating film formed on a surface of the electroless Pd plating film.
• the present invention includes an electronic equipment component including the electroless Pd plating film of the present invention.
• a Pd plating film forming a plating film having excellent wire bondability even after a high-temperature thermal history in reflow treatment or the like can be obtained.
• the present inventors have extensively conducted studies on a cause of a phenomenon in which when a layered plating film with a Au plating film formed on a Pd plating film (hereinafter, sometimes referred to as a "Pd/Au layered plating film”) is exposed to a high-temperature thermal history in reflow or the like, the connection success rate in subsequent wire bonding is significantly reduced. Resultantly, it has been considered that exposure to a high-temperature thermal history causes Pd to diffuse to a Au plating film surface, so that a Pd-Au solid solution is formed on the Au plating film surface, resulting in reduction of the connection success rate in wire bonding.
• One solution for such a problem may be formation of a Au plating film with a large thickness, but this solution leads to a significant increase in cost.
• the present inventors have further conducted studies, and resultantly found that when a Pd plating film containing both P and B (hereinafter, sometimes referred to as a "P-B-Pd ternary alloy film") is formed as an under-layer of the Au plating film, wire bondability after a high-temperature thermal history can be improved. That is, when the Pd plating film contains both P and B, formation of a Pd-Au solid solution on the Au plating film surface can be suppressed even when the film is exposed to a high-temperature thermal history, and as a result, wire bondability more excellent than ever before can be obtained even when the thickness of the film is equivalent to or less than that of a conventional Au plating film.
• the electroless Pd plating solution of the present invention is an electroless Pd plating solution containing a palladium compound; at least one selected from the group consisting of a hypophosphorous acid compound and a phosphorus acid compound; at least one selected from the group consisting of an amine borane compound and a hydroboron compound; and a complexing agent.
• a plurality of reducing agents used in the electroless Pd plating solution is known, and these reducing agents include hypophosphorous acid compounds, phosphorous acid compounds, amine borane compounds and hydroboron compounds used for the electroless Pd plating solution of the present invention.
• reducing agents have not used in combination heretofore because when a plurality of reducing agents having different reducing capacities is used, the plating solution has poor stability, so that abnormal precipitation or the like occurs, leading to deterioration of plating film properties.
• a hypophosphorous acid compound or a phosphorous acid compound has a sufficient reducing capacity on its own, and does not need to be combined with other reducing agents.
• the palladium compound is a source of palladium ions for obtaining palladium plating.
• the palladium compound is not limited as long as it is soluble in water, and examples of the palladium compound that can be used include inorganic water-soluble palladium salts such as palladium chloride, palladium sulfate and palladium acetate; and organic water-soluble palladium salts such as tetraaminepalladium hydrochloride, tetraaminepalladium sulfate, tetraaminepalladium acetate, tetraaminepalladium nitrate and dichlorodiethylene diaminepalladium. These palladium compounds may be used alone, or in combination of two or more thereof.
• the Pd ion concentration in the electroless Pd plating solution is not limited, and when the Pd ion concentration is excessively low, the deposition rate of the plating film may be significantly reduced. On the other hand, when the Pd ion concentration is excessively high, the physical properties of the film may be deteriorated due to abnormal deposition or the like.
• the content of the palladium compound in the plating solution is preferably 0.01 g/L or more, more preferably 0.1 g/L or more, still more preferably 0.3 g/L or more, and even more preferably 0.5 g/L or more, and preferably 10 g/L or less, more preferably 5 g/L or less, still more preferably 3 g/L or less in Pd ion concentration.
• Pd ions are measured by atomic absorption spectrometry (AAS) using an atomic absorption spectrophotometer.
• the electroless Pd plating solution of the present invention in order to exhibit an inhibitory effect on solid-dissolution of Pd, it is necessary that (1) at least one selected from the group consisting of a hypophosphorous acid compound and a phosphorus acid compound (hereinafter, sometimes referred to as a "phosphoric acid compound) be used in combination with (2) at least one selected from the group consisting of an amine borane compound and a hydroboron compound (hereinafter, sometimes referred to as a "boron compound").
• a hypophosphorous acid compound and a phosphorus acid compound hereinafter, sometimes referred to as a "phosphoric acid compound
• boron compound a hydroboron compound
• hypophosphorous acid compound examples include hypophosphorous acid and hypophosphites such as sodium hypophosphite, and examples of the phosphite compound include phosphorous acid and phosphites such as sodium phosphite.
• the hypophosphorous acid compounds and the phosphorous acid compounds may be used alone, or in combination of two or more thereof.
• the content of the hypophosphorous acid compound and/or the phosphorous acid compound in the electroless Pd plating solution is excessively low, the deposition rate during the plating process is reduced, and it may be impossible to obtain a sufficient inhibitory effect on solid-dissolution of Pd in the Au plating film due to a high-temperature thermal history, leading to deterioration of wire bondability.
• the inhibitory effect on solid-dissolution is improved, but the stability of the electroless Pd plating solution may be deteriorated.
• the content of the hypophosphorous acid compound and the phosphorous acid compound in the electroless Pd plating solution is preferably 0.1 g/L or more, more preferably 0.5 g/L or more, still more preferably 1 g/L or more, even more preferably 2 g/L or more, and preferably 100 g/L or less, more preferably 50 g/L or less, still more preferably 20 g/L or less, even more preferably 15 g/L or less.
• amine borane compounds serve as a source of boron to the Pd plating film, and act as a reducing agent for depositing palladium in the electroless Pd plating solution.
• amine borane compound examples include dimethylamine borane (DMAB) and trimethylamine borane (TMAB)
• hydroboron compound include alkali metal borohydrides such as sodium borohydride (SBH) and potassium borohydride (KBH).
• SBH sodium borohydride
• KH potassium borohydride
• the content of the boron compound in the electroless Pd plating solution is excessively low, the deposition rate during the plating process is reduced, and it may be impossible to obtain a sufficient inhibitory effect on solid-dissolution of Pd in the Au plating film due to a high-temperature thermal history, leading to deterioration of wire bondability.
• the inhibitory effect on solid-dissolution is improved, but the stability of the electroless Pd plating solution may be deteriorated.
• the content of the boron compound in the electroless Pd plating solution is preferably 0.01 g/L or more, more preferably 0.1 g/L or more, still more preferably 0.5 g/L or more, even more preferably 1 g/L or more, and preferably 100 g/L or less, more preferably 50 g/L or less, still more preferably 30 g/L or less, even more preferably 20 g/L or less.
• the complexing agent has mainly a stabilizing action on the solubility of Pd in the electroless Pd plating solution.
• the complexing agent may be any of various known complexing agents, and is preferably at least one selected from the group consisting of ammonia and an amine compound, more preferably an amine compound.
• the amine compound methylamine, dimethylamine, trimethylamine, benzylamine, methylenediamine, ethylenediamine, ethylenediamine derivative, tetramethylenediamine, diethylenetriamine, ethylenediaminetetraacetic acid (EDTA), alkali metal salts thereof, EDTA derivatives and glycine.
• the complexing agents can be used alone, or in combination of two or more thereof.
• the content of the complexing agent in the electroless Pd plating solution may be approximately adjusted so as to obtain the above-described action, and is preferably 0.5 g/L or more, more preferably 1 g/L or more, still more preferably 3 g/L or more, even more preferably 5 g/L or more, and preferably 50 g/L or less, more preferably 30 g/L or less.
• the electroless Pd plating solution of the present invention exhibits the above-described effects as long as it has the above-described component composition
• the electroless Pd plating solution may have only the component composition.
• the electroless Pd plating solution may contain various additives such as a pH adjuster and a stabilizer may be added.
• the pH of the electroless Pd plating solution of the present invention is excessively low, the deposition rate of Pd easily decreases, and when the pH is excessively high, the stability of the electroless Pd plating solution may be deteriorated.
• the pH is preferably 4 to 10, more preferably 6 to 8.
• the pH of the electroless Pd plating solution can be adjusted by adding a known pH adjuster.
• the pH adjuster include acids such as hydrochloric acid, sulfuric acid, nitric acid, citric acid, malonic acid, malic acid, tartaric acid and phosphoric acid, and alkalis such as sodium hydroxide, potassium hydroxide and ammonia water. These pH adjusters can be used alone, or in combination of two or more thereof.
• the stabilizer is optionally added for the purpose of, for example, securing plating stability, improving the appearance after plating, and adjusting the plating film formation rate.
• the electroless Pd plating solution of the present invention may further contain a known sulfur-containing compound.
• the sulfur-containing compound is preferably one or more selected from, for example, a thioether compound, a thiocyan compound, a thiocarbonyl compound, a thiol compound, thiosulfuric acid and a thiosulfate.
• thioether compounds such as methionine, dimethylsulfoxide, thiodiglycolic acid and benzothiazole
• thiocyan compounds such as thiocyanic acid, potassium thiocyanate, sodium thiocyanate and ammonium thiocyanate
• thiocarbonyl compounds such as thiourea and derivatives thereof
• thiol compounds such as cysteine, thiolactic acid, thioglycolic acid, mercaptoethanol and butanethiol
• thiosulfates such as sodium thiosulfate.
• the content of the stabilizer in the electroless Pd plating solution may be approximately adjusted so as to obtain an effect such as plating stability, and is preferably 0.1 mg/L or more, more preferably 0.5 mg/L or more, and preferably 500 mg/L or less, more preferably 100 mg/L or less.
• the electroless Pd plating solution of the present invention does not contain a surfactant.
• a surfactant is added to the electroless Pd plating solution of the present invention, the surfactant is adsorbed to a surface of the resulting Pd plating film, so that formability of the Au plating film is deteriorated. As a result, wire bondability is deteriorated.
• the surfactant is any of various known nonionic, cationic, anionic and amphoteric surfactants.
• the present invention includes a Pd plating film which is obtained using the electroless Pd plating solution, and contains P and B. Since the inhibitory effect on solid-dissolution of Pd is obtained as long as the Pd plating film contains both P and B, the content of each of P and B is not limited, and when the content of P or B contained in the Pd plating film increases, the inhibitory effect on solid-dissolution of Pd is further improved.
• the content of P in the Pd plating film is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less.
• the content of B in the Pd plating film is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and preferably 15% by mass or less, more preferably 10% by mass or less.
• the mass ratio (P : B) of the content of P and B in the electroless Pd plating film is preferably 10 : 1 to 1 : 10, and more preferably 5 : 1 to 1 : 5.
• the Pd plating film of the present invention may contain P and B, and further contain components derived from the above-described various additives. The balance consists of Pd and unavoidable impurities.
• the electroless Pd plating solution of the present invention is also suitable for a Pd/Au layered plating film with an Au plating film stacked on a Pd plating film, which is preferably used for plating for bonding of electronic components, etc. Therefore, a layered plating film having the Pd plating film of the present invention and the Au plating film is also a preferred embodiment.
• the Pd plating film of the present invention can be confirmed to have an inhibitory effect on solid-dissolution of Pd in a Pd/Au layered plating film in which at least a Au plating film is stacked.
• the base that forms the Pd plating film is not limited, and examples thereof include various known base materials such as Al, Al-based alloys, Cu and Cu-based alloys, and plating films in which a base material is covered with a metal catalytic for reduction and deposition of the Pd plating film, such as Fe, Co, Ni, Cu, Zn, Ag, Au, Pt and alloys thereof. Even a noncatalytic metal can be used as an object to be plated in various methods.
• the electroless Pd plating solution of the present invention can be applied to the ENEPIG process.
• an electroless Ni/Pd/Au plating film including the Pd plating film of the present invention can be obtained by forming a Ni plating film, then a Pd plating film, and then a Au plating film on, for example, Al, anAl-based alloy, Cu or a Cu-based alloy that forms an electrode.
• a common method may be employed for the formation of each plating film.
• the plating conditions and plating apparatus at the time of performing electroless Ni plating using an electroless Ni plating solution are not particularly limited, and any of various known methods can be appropriately selected.
• an object to be plated may be brought into contact with the electroless Ni plating solution at a temperature of 50 to 95°C for about 15 to 60 minutes.
• the thickness of the Ni plating film may be appropriately set according to the required properties, and is typically about 3 to 7 ⁇ m. Any of various known compositions such as Ni-P alloys and Ni-B alloys can be used for the electroless Ni plating solution.
• the plating conditions and plating apparatus at the time of performing electroless Pd plating using the electroless Pd plating solution of the present invention are not particularly limited, and any of various known methods can be appropriately selected.
• an object to be plated, on which a Ni plating film is formed may be brought into contact with the electroless Pd plating solution at a temperature of 50 to 95°C for about 15 to 60 minutes.
• the thickness of the Pd plating film may be appropriately set according to the required properties, and is typically about 0.001 to 0.5 ⁇ m.
• the plating conditions and plating apparatus at the time of performing electroless gold plating using an electroless gold plating solution are not particularly limited, and any of various known methods can be appropriately selected.
• an object to be plated, on which a Pd plating film is formed may be brought into contact with the electroless gold plating solution at a temperature of 40 to 90°C for about 3 to 20 minutes.
• the thickness of the gold plating film may be appropriately set according to the required properties, and is typically about 0.01 to 2 ⁇ m.
• the Pd plating film of the present invention When the Pd plating film of the present invention is used, palladium can be inhibited from being diffused to and solid-dissolved in the Au plating film from the Pd plating film due to a thermal history in a mounting process after formation of the film, such as reflow treatment, and therefore excellent wire bondability can be achieved even after the thermal history.
• the temperature in the thermal history is a temperature at which the mounting process is carried out, and the temperature is not particularly limited.
• excellent wire bondability can be achieved even after a thermal history at a high temperature of, for example, 50°C or higher, more preferably 100°C or higher.
• the present invention also includes an electronic equipment component having the plating film.
• the electronic equipment component include components that form electronic equipment, such as chip components, crystal oscillators, bumps, connectors, lead frames, hoop materials, semiconductor packages and printed circuit boards.
• the plating film is suitably used for a technique for forming UBM (Under Barrier Metal) for solder bonding and wire bonding (W/B) to an A1 electrode or a Cu electrode on a wafer.
• UBM Under Barrier Metal
• a BGA substrate (Ball Grid Array: Uyemura & Co., Ltd., 5 cm x 5 cm) was sequentially subjected to the pretreatment and plating treatment shown in Table 1, thereby producing test pieces 1 to 20 in which a Ni plating film, a Pd plating film and a Au plating film are formed in this order from the substrate side. The wire bondability of each of the obtained test pieces was examined.
• Wire bonding was performed using a test apparatus (SemiAutomatic Wire Bonder HB16 manufactured by TPT K.K.), and wire bondability was evaluated at each of 20 points under the following measurement conditions using Bond Tester SERIES 4000 manufactured by Dage Ltd. The measurement was performed before and after the heat treatment (in which the test piece was held at 175°C for 16 hours).
• a test piece having an average wire bonding strength of 9.0 g or more after heat treatment was rated "Excellent”
• a test piece having an average wire bonding strength of 8.5 g or more and less than 9.0 g after heat treatment was rated "Good”
• a test piece having an average wire bonding strength of 7.5 g or more and less than 8.5 g after heat treatment was rated "Acceptable”
• a test piece having an average wire bonding strength of less than 7.5 g after heat treatment was rated "Poor”.
• Capillary B1014-51-18-12 (manufactured by PECO Ltd.) Wire: 1mil-Au wire (SPM Ltd.) Stage temperature: 150°C Ultrasonic wave (mW): 250 (1st), 250 (2nd) Bonding time (ms): 200 (1st), 50 (2nd) Tensile force (gf):25 (1st), 50 (2nd) Step (1st to 2nd length): 0.7mm Measurement method: Wire pull test Equipment: Universal Bond Tester #4000 (manufactured by Nordson Advanced Technology K.K.) Test speed: 170 ⁇ m/sec [Table 1] Steps Name of chemicals Treatment temperature Treatment time (min.) Target film thickness Pretreatment Cleaner ACL- 50°C 5 - Soft etching SP 25°C 1 - Pickling 10% H 2 SO 4 room temperature 1 - Predip 3% H 2 SO 4 room temperature 1 - activator MNK- 30°C 2 - plating treatment electroless Ni plating NPR- 80°C 30 6um electroless Pd plating see
• test pieces Nos. 1 to 9 obtained using the electroless Pd plating solution containing a complexing agent, a hypophosphorous acid compound and/or a phosphorous acid compound, and an amine borane compound and/or a hydroboron compound as defined in the present invention were each rated “Good” or "Excellent” in evaluation of wire bondability after heat treatment.
• test pieces Nos. 10 to 18 obtained using a Pd plating solution that did not satisfy the requirements of the present invention were each rated "Poor” in evaluation of wire bondability after heat treatment.
• Test pieces Nos. 19 and 20 were each rated "Poor” in evaluation of wire bondability after heat treatment because they contained a surfactant.

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• 2017
  • 2017-10-06 JP JP2017195651A patent/JP7149061B2/ja active Active
• 2018
  • 2018-10-03 EP EP18864662.4A patent/EP3693495A4/fr active Pending
  • 2018-10-03 US US16/753,417 patent/US20200248312A1/en not_active Abandoned
  • 2018-10-03 KR KR1020207011967A patent/KR20200062265A/ko not_active Application Discontinuation
  • 2018-10-03 WO PCT/JP2018/036970 patent/WO2019069964A1/fr unknown
  • 2018-10-03 CN CN201880064756.9A patent/CN111164236A/zh active Pending
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