US3853714A - Process for electroforming microparts having hollow interiors - Google Patents

Process for electroforming microparts having hollow interiors Download PDF

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Publication number
US3853714A
US3853714A US00263094A US26309472A US3853714A US 3853714 A US3853714 A US 3853714A US 00263094 A US00263094 A US 00263094A US 26309472 A US26309472 A US 26309472A US 3853714 A US3853714 A US 3853714A
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United States
Prior art keywords
mold cavity
plate
process according
electrically conductive
lead wire
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Expired - Lifetime
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US00263094A
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English (en)
Inventor
K Shimada
H Hotoda
S Funayama
T Yamamoto
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Seiko Instruments Inc
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Seiko Instruments Inc
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/02—Tubes; Rings; Hollow bodies

Definitions

  • An electroforming process for manufacturing microparts comprises forming a mold cavity having the configuration of the desired micropart in a resin plate, lining the interior of the mold cavity with an electrically conductive material, attaching a lead wire to the electrically conductive material, immersing the mold cavity in an electrolytic bath, supplying dc electric energy to the lead wire to electrodeposit a metal layer of substantially uniform thickness and which comprises the micropart within the mold cavity, removing the electroformed micropart from the mold cavity, and finally removing excess portions of the electrodeposited material to obtain a finished micropart.
  • the ratio of the height of the side wall to the width of the bottom wall of the mold cavity is preferably maintained at a value less than 3:1.
  • Another object of the present invention is to provide a process of electroforming microparts which may be commercially carried out on a mass production basis.
  • a further object of the present invention is to provide a process of electroforming microparts wherein the amount of electrodeposition which does not actually constitute part of the final product is held to a minimum thereby increasing the efficiency of electrodeposition.
  • a still further object of the present invention is to provide a process of electroforming microparts which are substantially free of internal warping caused by compressive and tensile stresses developed during the electroforming process.
  • FIG. 2 is a graph showing the relationship between the thickness ratio of electrodeposition vs. both current density and the duration of electroforming;
  • FIG. 3 is a perspective view showing the directions of electrodeposition growth
  • FIG. 4A is a plan view of a mold cavity used in the process of the present invention for electroforming a pallet fork and FIG. 4B is a cross-sectional view taken aiong the line 4B-4B in FIG. 4A;
  • FIG. 5A is a plan view of a pallet fork made by the electro-forming process of the present invention and FIG. 5B is a cross-sectional view taken along the line 5B--5B in FIG. 5A;
  • FIG. 6A is a plan view of a plurality of mold cavities used for electroforming pallet forks in accordance with the present invention and FIG. 6B is a cross-sectional view taken along line 68-63 in FIG. 6A;
  • FIG. 7 is an explanatory view of one technique for attaching lead wires to the mold cavities.
  • FIG. 8 is a plan view of a portion of an escape wheel madein accordance with the electroforming process of the present invention.
  • FIGS. 1A, 1B and 1C are cross-sectional views showing various molds containing electroformed products for three different size products.
  • the mold comprises a resin plate 1 having a mold cavity 2 formed therein having steep side walls termi nating at their base in a bottom wall and having the shape and configuration of the desired part or article.
  • the mold cavity 2 is formed by casting a metal block into the configuration of the desired part and then heating the metal casting and transferring same to the resin plate while in a hot state to impress in the resin plate a mold cavity having a shape complementary to that of the metal casting.
  • the metal casting comprises a male member and forms in the resin plate a female member which exactly complements the male member.
  • FIG. IA shows a mold cavity 2 having a dimension ratio h/d equal to the height of depth h of the cavity relative to the width (1' of the cavity of l:l.
  • FIGS. 18 and 1C show dimension ratios of 2:1 and 3:1, respectively.
  • the entire inner surface of the mold cavity is coated with a layer 4 of silver or some other electrically conductive material and this layer subsequently functions as a cathodic electrode during the electroforming process.
  • a lead wire 3 is attached to the base of the resin plate in electrical contact with the layer 4 and. thus the mold cavity is lined with an electrically conductive layer which may be connected through the lead wire 3 to a source of electric power.
  • the mold is then immersed in an appropriate electrolytic solution which contains dissolved salts of the metal to be deposited.
  • the lead wire 3 is connected to the negative terminal of a dc voltage source thereby making the electrode 4 a cathode and a metal to be deposited onto the metallic layer 4 is inserted into the electrolytic solution and connected to the positive terminal of the dc voltage source and made the anode. Since the anode and cathode are connected to respective terminals of the dc voltage source, metallic ions begin to migrate and deposit upon the cathode to electroform a hollow micropart 9 having an outer configuration corresponding to that of the mold cavity 2.
  • the experiment comprised electroforming three different size parts having dimension ratios of l:l. 2:l and 3:1 such as shown in FIG. 1.
  • the composition of the electrolytic solution was:
  • the thickness ratio of the electrodeposited material decreases both with increasing current densities and increasing durations of electroforming.
  • the current density When the current density is 5A/dm the electrode position near the top opening of the mold cavity increases while the quantity of material deposited on the side walls and bottom of the mold cavity remains quite thin. As may he clearly seen from examining FIG. 2, the thickness ratio of electrodeposition decreases with an increase in the dimension ratio and this is primarily because it is more difficult for the metallic ions in the electrolytic bath to move into the mold cavity as the cavity becomes thinner. In addition, as the mold cavity becomes thinner, greater amounts of excess material 9a is deposited and accummulated near the opening of the mold cavity thereby reducing the size of the opening and further hindering the influx of metallic ions to the remainder of the mold cavity. Thus, in order to obtain a uniform thickness of the electroformed parts, the current density should preferably be less than SA/dm when the dimension ratio is less than 1:1 and less than 4A,!dm when the dimension ratio is 2:].
  • the resulting electroformed part 9 is removed from the mold cavity and is appropriately finished to obtain a workpiece having uniform thickness. As seen in FIGS. 1AlC, the part 9 is cut along the chain line to remove the useless excess portion 9a and then the part is ground or otherwise machined to uniformize the thickness of the part.
  • each part 9 except for the portions 9a is substantially uniform. Since the entire inner surface of the mold cavity 2 is lined with an electrically conductive material. the electrodeposited material accummulates and grows upon the lining simultaneously in three directions such as shown by the arrows in FIG. 3. Since the electrode posited material is simultaneously deposited in three directions, internal stresses in the workpieces are greatly reduced since the stresses complement and offset one another and cancel each other out. (Somequently, the workpieces formed according to the process of the present invention have a long useful life since they do not have areas of localized stress.
  • a metal casting is made having the configuration of the pallet fork and the dimension ratio of the height of the pallet fork relative to its width in any cross-section thereof is preferably less than 3:1.
  • the metal casting is then heated and impressed upon the surface of a resin plate I as shown in FIG. 4A to form in the resin plate a mold cavity 2 having the configuration of the pallet fork.
  • the resin plate is composed of thermal plastic resin such as vinylchloride resin, so called A, B, C resin, acrylic resin, polyvinyle acetate resin, polyethylene resin, polypropylene resin, etc.
  • a lead wire 3 is embedded in the resin plate beneath the mold cavity and exposed to the bottom of the mold cavity. Then a thin electric conductor is disposed around the entire interior of the mold cavity and in this example, the electric conductor comprises a silver coating. As seen in FIG. 4A, the conductor 4 completely covers the exposed surfaces of the mold cavity and is in electrical contact with the lead wire 3. Those portions of the electric conductor 4 which extend away from the mold cavity opening are then removed by grinding or another suitable method in order to prevent the formation of excessively deposited material adjacent the mold cavity which would hinder the electroformation of a uniform part.
  • FIGS. 5A and 5B are respectively plan views and longitudinal cross-sectional views of a pallet fork made by the process of the present invention.
  • the pallet fork 5 is provided with a substantially hollow interior 6 which greatly reduces the mass of the pallet fork and the pallet fork has a substantially uniform wall thickness and therefore does not have areas of localized stress which would decrease the strength of the pallet fork.
  • FIG. 6A discloses a type of resin plate 1' having thereon a plurality of mold cavities 2' each ofwhich is similar to the individual mold cavity 2 disclosed in FIG. 4A.
  • the mold cavities 2' are alternately inverted in order to minimize the space required and in this embodiment, the lead wire is formed by depositing a strip of electrically conductive material into a channel or groove formed in the resin plate 1' interconnecting the various mold cavities 2'.
  • the channel is formed in a manner similar to the formation of the mold cavities 2' and then the channel is lined with a film of silver or other appropriate electrically conductive material.
  • the plurality of mold cavities and the interconnecting channel may be simultaneously formed with a single metal casting.
  • FIG. 7 Another technique for attaching the lead wires to the mold cavities is shown in FIG. 7.
  • a resinplate 1' has a plurality of mold cavities 2' formed therein each of which has a configuration of the desired pallet fork. For the sake of simplicity and clarity, the individual mold cavities 2' have been shown as circules rather than the more intricate pallet-shape.
  • a screen 10 is then superposed over the resin plate 1 and the screen 10 contains therein a plurality of slots 10a which are each located to overlie and interconnect one row of mold cavitiesZ' when the screen is superposed over the resin plate 1'.
  • an electrically conductive material is vacuumdeposited through the slots 10a by vacuum-evaporation whereby the individual mold cavities 2' are electrically connected by thin electric leads or conductors 3'.
  • the unnecessary remaining portions of the electric conductors 3' are ground away.
  • the composition of the electrolytic bath was:
  • the Parameters of clectroforming were:
  • the individual pallet forks were removed from the resin plates and the electroformed pallet forks were then finished by cutting off the useless upper portions 9a and then the pallet forks were ground into a uniform thickness.
  • the resulting pallet forks 5 had the configuration shown in FIGS. 5A and 5B.
  • the pallet forks constructed in accordance with the process of the present invention have commercially acceptable mechanical strength yet have a light weight due to the hollow interior 6 and compare quite favorably with pallet forks formed by the conventional pressing technique.
  • the arcuate tip. portion 5a cooperates with a pallet jewel and the mechanical strength of the part 50 compares with the mechanical strength of corresponding parts of conventional pallet forks as follows:
  • the steel pallet fork has the greatest strength and the electroformed pallet fork constructed in accordance with the process of the present invention has a lower strength than the steel pallet fork but is much superior in strength than the nickel-silver pallet fork. As a practical matter, the electroformed pallet fork has sufficient strength to enable its use in watches.
  • FIG. 8 discloses a portion of an electroformed escape wheel manufactured in accordance with the present invention.
  • the escape wheel 8 has a hollow interior 7 and is formed by first constructing ametal casting having the configuration of the escape wheel and then the metal casting is transferred while in a hot state to a resin plate to form a mold cavity in the resin plate corresponding to the shape of the metal casting. Then a thin electric conductor is formed on the interior surface of the mold cavity and then the escape wheel is electroformed in a manner similar to that used in electroforming the pallet forks.
  • the process of the invention is not limited to the formation of watch parts and is applicable to the form ation of any other microparts.
  • the electrolytic solution has been described as comprising a nickel-bath, it is understood that other metal baths may be used depending upon the desired composition of the electroformed article.
  • a process for electroforming articles such as watch pallet forks and the like having hollow deep-bottomed interiors comprising: forming in a plate of electrically nonconductive material a plurality of mold cavities each having steep side walls terminating at their base in a bottom wall and having a depth to width ratio no greater than 3:] and having a configuration complementary to that of the exterior of an article to be formed; lining each said mold cavity with a layer of electrically conductive material while leaving the intervening spaces which remain on the plate between the cavities free of electrically conductive material; electrically connecting together each layer of electrically conductive material with a common lead wire which comprises a first electrode; then immersing the plate in an electrolytic solution containing dissolved salts of the metal to be deposited; placing a second electrode in said electrolytic solution; and applying dc electrical energy to said first and second electrodes to obtain a current density less than SA/dm for a time period sufficient to effect substantially uniform electrodeposition of metallic ions from within said electrolytic solution onto each said layer of electrically conductive material to
  • a process according to claim 1; wherein said forming step comprises producing a plurality of metal castings each having a configuration similar to that of one article to be formed, and impressing said metal castings while in a heated state onto said plate to form therein said mold cavities.
  • a process according to claim 1 wherein said im mersing step comprises immersing said plate in an electrolytic solution composed of Nickel sulphamate 250 g/litre Boronic acid 30 g/litre Nickel chroride 5 gilitre Sodium dodecyl-sulfonate 2.5 g/litre Sodium Lib-naphthalene trisuffonate 2.5 g/litre and maintained at a temperature of from 45 to 50 C.
  • said electrically connecting together step comprises superposing a cover member having a plurality of slots therein over said plate so that said slots collectively overlie and interconnect all of said mold cavities. and depositing on said plate through said slots an electrically conductive material comprising said common lead wire.
  • a process according to claim 1 including attaching said common lead wire to said plate such that said lead wire extends along each mold cavity bottom wall and is exposed to the interior of said mold cavity; and wherein said lining step comprises lining each mold cavity and the exposed portion of said lead wire with a layer of electrically conductive material.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physical Vapour Deposition (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
US00263094A 1971-06-15 1972-06-15 Process for electroforming microparts having hollow interiors Expired - Lifetime US3853714A (en)

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JP46042689A JPS4844138A (fr) 1971-06-15 1971-06-15

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JP (1) JPS4844138A (fr)
CH (2) CH872572A4 (fr)
GB (1) GB1336057A (fr)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4170524A (en) * 1976-06-25 1979-10-09 Nissan Motor Company, Ltd. Method of partially plating article or synthetic resin
DE3210861A1 (de) * 1981-03-24 1982-11-11 Citizen Watch Co., Ltd., Tokyo Verfahren zur herstellung von bauteilen fuer uhren
US4371429A (en) * 1980-08-25 1983-02-01 Citizen Watch Company Limited Timepiece hand manufacturing method
US4547267A (en) * 1981-12-24 1985-10-15 Ernst Leitz Wetzlar Gmbh Process for producing a photooptical shutter blade for an optical instrument
US5172568A (en) * 1988-09-09 1992-12-22 Senanayake Daya R Hollow jewelry objects and method
US5632878A (en) * 1994-02-01 1997-05-27 Fet Engineering, Inc. Method for manufacturing an electroforming mold
US6242163B1 (en) * 1998-08-31 2001-06-05 Board Of Trustees Of The Leland Stanford Junior University Shape deposition manufacturing of microscopic ceramic and metallic parts using silicon molds
US6736983B1 (en) * 1999-05-28 2004-05-18 Atotech Deutschland Gmbh Method for producing microcomponents
CN100378159C (zh) * 2003-12-19 2008-04-02 株式会社利其尔 微型部件、采用该部件的微孔阵列板或树脂制吸移管尖管
US9015921B2 (en) 2011-08-12 2015-04-28 Nivarox-Far S.A. Metal pallets with polymer horns
US20170146954A1 (en) * 2015-11-19 2017-05-25 Nivarox-Far S.A. Timepiece component
US20180363159A1 (en) * 2015-12-18 2018-12-20 Rolex Sa Method for producing a timepiece component
US20210191338A1 (en) * 2019-12-18 2021-06-24 Nivarox-Far S.A. Method of fabricating a timepiece component and component obtained from this method
EP4290314A1 (fr) * 2022-06-08 2023-12-13 Nivarox-FAR S.A. Roue pour un système d'échappement a inertie réduite
US12124223B2 (en) * 2019-12-18 2024-10-22 Nivarox-Far S.A. Method of fabricating a timepiece component and component obtained from this method

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5416044B2 (fr) * 1974-02-15 1979-06-19
IT1118356B (it) * 1979-02-15 1986-02-24 Cselt Centro Studii & Lab Tele Perfezionamenti ai processi di elettroformatura
JP4530262B2 (ja) * 2004-03-31 2010-08-25 セイコーインスツル株式会社 低融点金属を用いた電鋳部品の製造方法
EP2400352A1 (fr) * 2010-06-22 2011-12-28 The Swatch Group Research and Development Ltd. Système d'échappement pour pièce d'horlogerie

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1206881A (en) * 1913-06-02 1916-12-05 Henry C Miller Method of making diaphragms.
US1570634A (en) * 1922-05-24 1926-01-26 Arthur K Laukel Deposited-metal pattern and method of making it
US2335774A (en) * 1941-10-03 1943-11-30 Charles A J Landry Process for making prosthetic articles by electrodeposition of metals
US2841548A (en) * 1953-12-11 1958-07-01 Perlman David Electrode holder
US3441487A (en) * 1966-05-13 1969-04-29 Champion Spark Plug Co Method of accurately producing an abrasive surface of revolution

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1206881A (en) * 1913-06-02 1916-12-05 Henry C Miller Method of making diaphragms.
US1570634A (en) * 1922-05-24 1926-01-26 Arthur K Laukel Deposited-metal pattern and method of making it
US2335774A (en) * 1941-10-03 1943-11-30 Charles A J Landry Process for making prosthetic articles by electrodeposition of metals
US2841548A (en) * 1953-12-11 1958-07-01 Perlman David Electrode holder
US3441487A (en) * 1966-05-13 1969-04-29 Champion Spark Plug Co Method of accurately producing an abrasive surface of revolution

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Modern Electroplating, 2nd Edition, (1963), Fred Lowenheim, John Wiley & Sons, Inc., pgs. 272, 273, 282, 283, 285, 286. *

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4170524A (en) * 1976-06-25 1979-10-09 Nissan Motor Company, Ltd. Method of partially plating article or synthetic resin
US4371429A (en) * 1980-08-25 1983-02-01 Citizen Watch Company Limited Timepiece hand manufacturing method
DE3210861A1 (de) * 1981-03-24 1982-11-11 Citizen Watch Co., Ltd., Tokyo Verfahren zur herstellung von bauteilen fuer uhren
US4404067A (en) * 1981-03-24 1983-09-13 Citizen Watch Company Limited Method of manufacturing a timepiece component
US4455199A (en) * 1981-03-24 1984-06-19 Citizen Watch Company Limited Method of manufacturing a timepiece component
US4547267A (en) * 1981-12-24 1985-10-15 Ernst Leitz Wetzlar Gmbh Process for producing a photooptical shutter blade for an optical instrument
US5172568A (en) * 1988-09-09 1992-12-22 Senanayake Daya R Hollow jewelry objects and method
US5632878A (en) * 1994-02-01 1997-05-27 Fet Engineering, Inc. Method for manufacturing an electroforming mold
US6242163B1 (en) * 1998-08-31 2001-06-05 Board Of Trustees Of The Leland Stanford Junior University Shape deposition manufacturing of microscopic ceramic and metallic parts using silicon molds
US6736983B1 (en) * 1999-05-28 2004-05-18 Atotech Deutschland Gmbh Method for producing microcomponents
CN100378159C (zh) * 2003-12-19 2008-04-02 株式会社利其尔 微型部件、采用该部件的微孔阵列板或树脂制吸移管尖管
US9015921B2 (en) 2011-08-12 2015-04-28 Nivarox-Far S.A. Metal pallets with polymer horns
US20170146954A1 (en) * 2015-11-19 2017-05-25 Nivarox-Far S.A. Timepiece component
US20180363159A1 (en) * 2015-12-18 2018-12-20 Rolex Sa Method for producing a timepiece component
US20210191338A1 (en) * 2019-12-18 2021-06-24 Nivarox-Far S.A. Method of fabricating a timepiece component and component obtained from this method
US12124223B2 (en) * 2019-12-18 2024-10-22 Nivarox-Far S.A. Method of fabricating a timepiece component and component obtained from this method
EP4290314A1 (fr) * 2022-06-08 2023-12-13 Nivarox-FAR S.A. Roue pour un système d'échappement a inertie réduite

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Publication number Publication date
GB1336057A (en) 1973-11-07
CH872572A4 (fr) 1977-07-29
CH604266B5 (fr) 1978-08-31
JPS4844138A (fr) 1973-06-25

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