Method and apparatus for plating substrates

Abstract

Plating apparatus comprises a gear mechanism for imparting planetary motion to a set of holders for holding substrates in a plating bath. The holders are typically a non-conductive material such as plastic. The holders are coupled to a bearing comprising first and second plastic races and metallic balls therebetween. This embodiment reduces the amount of plastic moving against plastic, and therefore reduces the amount of wear, friction, and generation of contaminant parts. The holders comprise a central mandrel and outer mandrels connected to end pieces. The substrates are held at their outer edges between the outer mandrels and the central mandrels.

Description

BACKGROUND OF THE INVENTION

This invention relates to methods and apparatus for plating substrates.

There are various manufacturing processes during which one plates substrates. For example, during some processes for making magnetic disks, one places an aluminum alloy substrate in a plating bath to electroless plate a nickel-phosphorus alloy layer onto the substrate. Thereafter, the plated substrate is polished and textured, and one or more underlayers, one or more magnetic layers, and one or more protective overcoats are deposited (e.g. by sputtering) onto the plated substrate. (During some manufacturing processes, other layers are deposited onto the substrate as well.) Merely by way of example, one method for polishing a substrate is discussed in U.S. Pat. No. 6,149,696, issued to Jia on Nov. 21, 2000. A method for texturing a substrate is discussed in U.S. patent application Ser. No. 10/299,029, filed by Homola on Nov. 18, 2002. A method for depositing various layers onto a plated substrate is discussed in U.S. patent application Ser. No. 10/075,123, filed by Bertero et al. on Feb. 12, 2002. Jia, Homola and Bertero are incorporated by reference.

Apparatus for plating magnetic disk substrates is discussed in U.S. Pat. No. 4,581,260, issued to Mawla on Apr. 8, 1986; U.S. Pat. No. 4,516,523 issued to Knox on May 14, 1985; and U.S. Pat. No. 5,951,763, issued to Knox on Sep. 14, 1999. In these devices the substrates are held by a dowel extending through the central opening in the substrates. The substrates are then moved through a plating bath. During plating, the substrates can wobble. Imperfections may result if they touch one another. One could try to prevent the substrates from touching one another by increasing the distance between adjacent substrates, but that would reduce the number of substrates that could be plated at one time.

SUMMARY

Apparatus in accordance with one embodiment of our invention comprises a novel structure for holding substrates during plating. The substrates are typically planar and disk-shaped. The novel holding structure comprises a set of mandrels. (As used herein, mandrels are elongated members.) The mandrels are typically cylindrical, and typically comprise notches for receiving the outer edges of the substrates. However, in other embodiments, the mandrels are not cylindrical, and do not have circular cross sections. Also, in other embodiments, the mandrels do not have notches.

In one embodiment, the holding structure holds one or more sets of substrates, each substrate within a set being generally parallel to the other substrates within that set. In one embodiment, each substrate is held at its outer edge by the mandrels. Because of this, the substrates do not wobble during plating, and therefore do not touch each other during plating.

At least one of the mandrels is removable to facilitate loading and unloading of the substrates from the holding structure. The substrates can be magnetic disk substrates having a central opening therein. Because of the manner in which the substrates are held at their outer edges, it is easier to load and unload the substrates compared to earlier substrate plating apparatus in which the substrates were held by a dowel extending through their central opening.

In one embodiment, each set is held by one side of the central mandrel and an associated set of one or more outer mandrels. (The mandrels hold the set of substrates at the outer edges of the substrates.) Thus, a plurality of sets of substrates abuts the central mandrel. In one exemplary embodiment, three sets of substrates abut the central mandrel. The first, second and third set of substrates abut a top, lower left and lower right side of the central mandrel, respectively. This arrangement of substrates permits a larger number of substrates to be held in a given volume than if the plurality of sets of substrates did not abut a common central mandrel.

In one embodiment, a gear mechanism imparts planetary motion to the substrates during plating. This gear mechanism is mechanically coupled to the holding structure.

The mandrels are typically held on their left and right ends by a left plate and a right plate, respectively. (In one embodiment, the mandrels are parallel.) At least some of the mandrels are removable to permit one to load and unload substrates into and from the holding structure. The plates comprise a slot that permits use of a tool to load and unload the holding structure. The tool comprises a mandrel for extending through an opening in the substrates. Thus, during loading and unloading, the tool mandrel is placed in the inner opening of the substrates, and lifts the substrates out of the holding structure.

A method in accordance with the invention includes the act of placing one or more substrates in a holding structure as described above. The holding structure is coupled to apparatus for moving the substrates (typically in a planetary manner). The apparatus, holding structure, and substrates are placed in a bath where a layer of material is plated onto the substrates. In one embodiment, the substrates are metallic (e.g. aluminum or an aluminum alloy), and a metallic layer (e.g. a nickel phosphorus alloy) is plated onto the substrates. After plating, the apparatus is removed from the bath, and the substrates are removed from the holding structure.

An apparatus in accordance with another embodiment of the invention comprises a holder for holding one or more substrates during plating. The holder typically has a plastic exterior, and includes a plastic member for coupling with a first race of a bearing. A second race of the bearing is also plastic, and is coupled to a rotating structure that imparts motion to the holder (and therefore to the one or more substrates held by that holder). A metallic interface (typically comprising balls or rollers) is provided between the first and second races. (The metallic interface is typically passivated to prevent the interface from becoming plated during use). Of importance, the bearing permits one to avoid or minimize the motion of plastic against plastic. This reduces the amount of friction, mechanical wear, and most importantly, generation of contaminant particles in the plating bath.

In one embodiment, a bearing with metallic races (e.g. stainless steel) as well as a metallic interface is employed. In such an embodiment, the races are typically passivated. Although this embodiment may be acceptable, metal-on-metal wearing of the races and the interface may grind away the passivation, thereby exposing metallic surfaces to the plating bath and permitting the bearing to be plated. Further, contamination particles (e.g. plated material on the bearing) may be generated. Accordingly, the embodiment using plastic races may be more desirable.

In one embodiment, a gear mechanism imparts planetary motion to the one or more substrates within the holder.

A method in accordance with another embodiment of the invention comprises the act of providing one or more substrates in a holder. The holder is mechanically coupled via a bearing to apparatus for imparting motion to the holder. The holder, one or more substrates and apparatus are placed in a plating bath, and the apparatus imparts motion to the holder. In one embodiment, the holder comprises first and second plastic races, and a metallic mechanical interface (typically a set of metal balls) therebetween. As mentioned above, this reduces the amount of friction, mechanical wear and generation of contaminant particles in the plating bath.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically illustrates a plating bath containing apparatus that imparts motion to substrates during plating.

FIGS. 1B and 1C illustrate portions of the apparatus that impart motion to substrates.

FIGS. 2A and 2C illustrate a holder that holds substrates in the apparatus of FIG. 1. FIG. 2B shows the holder with two of its mandrels removed.

FIGS. 3A and 3B illustrate a portion of removable mandrels used in conjunction with the holder of FIGS. 2A to 2C.

FIG. 4 illustrates a tool for removing substrates from the holder of FIG. 2.

FIG. 5 illustrates in cross section the apparatus of FIG. 1.

FIG. 6 illustrates in cross section the apparatus of FIG. 5 along lines 6-6.

FIG. 7 illustrates in cross section the apparatus of FIG. 5 along lines 7-7.

FIG. 8 illustrates in cross section the apparatus of FIG. 5 along lines 8-8.

FIGS. 9A and 9B illustrate the manner in which a holder is placed into position for loading and unloading.

FIG. 10 illustrates a second embodiment of apparatus for plating substrates in which the substrates are held at their outer edges.

FIG. 11 illustrates a holder used in conjunction with the apparatus of FIG. 10.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 5, a plating bath 8 contains apparatus 10 for holding and moving substrates S during a plating process. (FIGS. 1B and 1C only show one substrate S. However, typically many substrates are plated simultaneously.) In one embodiment, the substrates comprise an aluminum alloy, and during plating, a layer (typically a metallic layer such as a nickel-phosphorus alloy) is deposited on substrates S. However, in other embodiments, substrates S can comprise other materials, and other types of layers can plated onto substrates S.

In one embodiment, substrates S are disk-shaped, and can include a centrally defined opening O therein. However, in other embodiments, substrates S have other shapes.

The plating process can be electroless plating or electroplating. Optionally, in the case of electroless plating one can apply a strike voltage to substrates S to facilitate initiation of plating. Alternatively, in some embodiments, a strike voltage is not applied to substrates S. During plating, substrates S are held by four holders 12, and a drive mechanism imparts planetary motion to these holders (and therefore to the substrates S held by the holders). (Only a part of one holder 12 is shown in FIGS. 1B, 1C and 5 for ease of illustration.)

Prior to plating, apparatus 10 is removed from bath 8, and substrates S are loaded into the apparatus. Apparatus 10 is then placed in bath 8 for plating. After plating, apparatus 10 is again removed from bath 8, and substrates S are removed from apparatus 10.

Holders 12

Referring to FIGS. 1B, 1C and 2A-2C, each holder 12 typically comprises a central mandrel MC, a set of intermediate mandrels MI, and a set of outer mandrels MO, each connected to left and right end pieces EL and ER, respectively. Mandrels MC, MI and MO and end pieces EL, ER are typically made from a plastic such as PVDF, polypropylene, PFA, PTFE (Teflon) or PEEK. Mandrels MC, MI and MO and end pieces EL, ER are generally not metallic or electrically conductive. Using plastic material for holders 12 has the advantage that when the holders are placed in a plating bath, holders 12 are not plated. However, in an alternative embodiment, end pieces EL and ER are metallic for reasons discussed below.

As described below, outer mandrels MO are removable to facilitate loading or unloading holders 12 with substrates S. Also, mandrels MC, MI and MO typically comprise notches N for holding substrates S. Mandrels MC, MI and MO cooperate to hold three sets of substrates S. Substrates S are typically generally parallel, each set abutting an associated side of central mandrel MC.

In the illustrated embodiment, mandrel MC, two mandrels MI and two mandrels MO cooperate to hold one set of parallel substrates S. (Mandrels MO are removable; mandrels MC and MI are not removable.) Holder 12 comprises six removable outer mandrels MO and six non-removable mandrels MI to hold the above-mentioned three sets of substrates S. Although FIGS. 2A, 2B, 2C and 5 only show central mandrel MC, two removable mandrels MO and two non-removable mandrels MI, the side views shown in FIGS. 6, 7 and 8 show the arrangement of all thirteen mandrels in a holder. In addition, in FIG. 7 shows the manner in which one of the holders 12 holds three sets of substrates (sets SA, SB and SC). (FIGS. 6, 7 and 8 also illustrate the manner in which apparatus 10 contains four different holders 12.)

Mandrels MC include portions PL, PR (FIG. 5) extending through and past end pieces EL, ER. As explained below, a set of wheels and gears engage portions PL, PR of mandrels MC to impart motion to mandrels MC and therefore to holders 12. (In lieu of having mandrels MC including portions PL, PR extending through and past end pieces EL, ER, in an alternative embodiment, mandrels MC stop at end pieces EL, ER and a separate post is mounted on end pieces EL, ER to engage with the set of wheels and gears.)

Drive Mechanism for Imparting Motion to Holders 12

Referring to FIGS. 1A, 1B and 5, a drive shaft DS of a motor M (typically an electric motor) rotates a drive gear DG, which in turn drives a right drive gear GR1, which in turn drives an idler shaft IS, which in turn drives a left drive gear GL1. Drive gears GR1 and GL1 in turn drive second gears GR2 and GL2. Gears GR2 and GL2 are affixed to wheels WR (FIG. 1B) and WL (FIG. 1C), respectively. As described below, wheels WR and WL indirectly engage with central mandrels MC to cause central mandrels MC to rotate about a central axis A (FIGS. 1C and 5) of wheels WR and WL. (Wheels WR and WL synchronously rotate about the same axis A.)

Portion PR of central mandrel MC is rigidly connected to an inner race 16R of a bearing BR (FIG. 2C). Bearing BR is typically a ball bearing, and can include nine metal balls, e.g. made of stainless steel (not shown). (Alternatively, other materials can be used to construct the bearing, and different numbers of balls can be used. In addition, rollers can be used in lieu of balls.) An outer race 18R of bearing BR rides in an opening 22R of wheel WR (FIG. 1B). As mentioned above, during use of apparatus 10, wheel WR rotates about its central axis A, thereby causing central mandrel MC, holder 12 and the substrates held by holder 12 to rotate about axis A. (Wheel WR is surrounded by a stationary ring 24R, which prevents bearing BR from falling out of opening 22R.) As mentioned above, in one embodiment, first and second races 16R, 18R are plastic, while the balls are metallic. This reduces the friction, wear and generation of contaminant particles during use of apparatus 10.

As shown in FIG. 1B, wheel WR includes additional openings 22R′ (identical to opening 22R). These openings accommodate other holders 12 that are not shown in FIG. 1B for ease of illustration.

Ring 24R contains an opening 25R (FIG. 1B) for permitting one to place holder 12 into or remove holder 12 from apparatus 10. During use, a locking piece 26R (FIG. 1C) is placed in opening 25R to prevent holder 12 from falling out of apparatus 10.

Portion PL of central mandrel MC is rigidly connected to a gear GL and an inner race 16L of bearing BL (FIG. 2A). Bearing BL is identical to bearing BR, and rides in an opening in wheel WL (FIG. 1C) in the same manner as bearing BR rides in opening 22R. Ring 24R surrounds wheel WR and prevents bearing BR from falling out of opening 22R.

FIG. 1C shows three openings 22L′ in wheel WL for accommodating additional holders, not shown in FIG. 1C for ease of illustration. Ring 24L includes an opening 25L (FIG. 1B) for permitting one to place holder 12 in or remove holder 12 from apparatus 10. During use a locking piece 26L (FIG. 1C) is placed in opening 25L to prevent holder 12 from falling out of apparatus 10.

Referring to FIG. 1C and FIG. 5, Gear GL (rigidly connected to portion PL of mandrel MC) engages with a stationary gear GL4 to cause holder 12 to rotate about mandrel MC, and thereby impart planetary motion to holder 12 and substrates S. The other holders 12 (not shown in FIGS. 1A-1C and 5) are similarly coupled to the gear mechanism of apparatus 10.

The major difference between the drive mechanism on the right and left sides of apparatus 10 is that in the illustrated embodiment, there are no gears analogous to gear GL and GL4 on the right side of apparatus 10 for causing holder 12 to rotate about the central axis of gear GL. However, in alternate embodiments, gears analogous to gear GL and GL4 are provided on the right side of apparatus 10, either in addition to or in lieu of gear GL.

Loading and Unloading Substrates From Apparatus 10

As mentioned above, before plating, one loads substrates S into apparatus 10. After plating one removes substrates S from apparatus 10. Typically, one loads and unloads one holder 12 at a time. This is accomplished by a) moving holder 12 into a position where it can be loaded and unloaded; and then b) removing mandrels MO to load or unload holder 12.

To move one of holders 12 into a position where it may be loaded or unloaded, one first rotates wheels WL, WR until openings 22L, 22R are aligned with openings 25L, 25R (e.g. the position as shown in FIGS. 1B and 9A). One then removes locking pieces 26 from rings 24L, 24R. (Typically, pins 50L, 50R are inserted through walls 10L, 10R of apparatus 10 and through an opening in locking pieces 26L, 26R to keep the locking pieces in place. Accordingly, one must remove pins 50L, 50R before removing locking pieces 26L, 26R. Pins 50 and locking pieces 26 are shown in exploded view form in FIG. 1B.) Thereafter, one pushes bearings BL, BR into an indentation 54L, 54R in the bottom of openings 25L, 25R. (FIGS. 9A and 9B illustrate indentation 54R at the bottom of opening 25R.)

One then rotates holder 12 so that one can access a desired portion of holder 12. A second pin 56 (FIG. 1B) is inserted through wall 10L to engage with the teeth of gear GL to thereby prevent holder 12 from rotating during loading or unloading. (In an alternative embodiment, instead of engaging with the teeth of gear GL, an opening can be provided in gear GL, and pin 56 is inserted through wall 10L and the opening in gear GL.)

Thereafter, one removes the mandrels MO associated with the portion of holder 12 being accessed. As shown in FIGS. 2A-2C, mandrels MO are removable. When mandrels MO are removed (e.g. as shown in FIG. 2B), one can remove substrates S from holder 12, or load substrates S into holders 12.

In one embodiment, mandrels MO extend through left and right locking plates 30L, 30R (FIGS. 3A, 3B). Springs 32 are coupled to an end of mandrels MO, and urge plates 30L, 30R against end pieces EL, ER. A set of pins 34 extends through openings 35 of plates 30L, 30R to hold plates 30L, 30R in place. One removes mandrels MO by pushing plates 30L, 30R away from end pieces EL, ER, past the end of pins 34. One can then remove mandrels MO and load substrates S into holder 12.

Thereafter, one reattaches mandrels MO to holder 12. Pin 56 is removed, and holder 12 is rotated so that a second portion of the holder can be accessed. Mandrels MO associated with that second portion are removed, substrates are loaded therein, and mandrels MO are reattached. The third portion of holder 12 is similarly loaded. Holder 12 is then placed back into openings 25L, 25R, and wheels WL, WR are rotated so that one can access a second one of holders 12. The second, third and fourth holders are then loaded, and locking pieces 26L, 26R are re-inserted into rings 24L, 24R. Apparatus 10 is then placed into bath 8, and motor 10 is turned on to impart motion to substrates S. After plating, apparatus 10 is removed from bath 8, mandrels MO are removed, and substrates S are removed from holders 12. (As shown in FIGS. 2 and 3, mandrels MO are typically removed and replaced two at a time, although in other embodiments this is not necessary.)

In one embodiment, slots 60 are provided in the end plate ER of holders 12 to facilitate loading substrates S into and removing substrates S from holder 12. In particular, during loading a U-shaped tool 62 (FIG. 4) is passed through openings 0 in substrates S. Tool 62 is passed through slot 60 so that substrates S are positioned so as to rest against mandrels MC and MI (direction 64). Tool 62 is then withdrawn (direction 66) so that it no longer extends through openings 0 and slot 60. Mandrels MO are then attached to holder 12. During unloading, tool 62 is passed through slot 60 and openings O of substrates S (direction 68). Tool 62 is then lifted and through the inner diameter of substrates S (direction 70). One can then pull tool 62 through slot 60 to remove the substrates.

Embodiment in Which End Pieces EL and ER are Metallic

As mentioned above, in some embodiments end pieces EL and ER are metallic (e.g. electropolished stainless steel). Advantageously, such end plates have improved dimensional stability compared, for example, to plastics such as PVDF, which can shrink as a result of exposure to the plating environment. Optionally, the end pieces can be passivated.

In another embodiment, metallic end pieces have the additional advantage that during plating, the electrochemical environment of the surfaces of the outer substrates S directly adjacent end pieces EL and ER is similar to the electrochemical environment of the other substrates. If end pieces EL and ER were plastic, the electrochemical environment of the substrates directly adjacent to end pieces EL and ER would differ from the electrochemical environment of the other substrates, and thus the plated surfaces of the substrates directly adjacent end pieces EL and ER might not be sufficiently identical to those of the other surfaces. (This can occur because a different concentration of atoms to be plated would diffuse to the interior substrates compared to the substrates directly adjacent plates EL and ER.) Accordingly, there is a novel advantage to using metallic end pieces EL and ER.

At least some of the above-mentioned advantage concerning the electrochemical environment for the outer substrates is present even if end plates EL, ER are passivated. However, in lieu of using metallic end plates EL, ER, one could use “dummy substrates” adjacent end pieces EL and ER to achieve this result.

In embodiments in which portions of the apparatus subject to the plating bath are metal, optionally, one may subject the apparatus to a stripping and re-passivating operation between plating steps or as desired.

Alternative Embodiment of Apparatus for Holding Substrates

FIG. 10 illustrates an alternative embodiment of apparatus 100 for holding and moving substrates such as substrate S during plating. Apparatus 100 comprises four holders 102 (FIG. 11), each holder 102 comprising four mandrels M. One of the mandrels M′ is removable from holder 102 to facilitate loading and unloading of substrates S into and from holder 102. (Mandrel M′ is held in place by screws 104a, 104b that are removed when loading or unloading holder 102.)

Holder 102 also includes left and right end pieces EL′, ER′ for holding mandrels M. Each holder coupled to a gear mechanism (similar to the gear mechanism described above) for imparting planetary motion to the substrates.

While the invention has been described with respect to specific embodiments, those skilled in the art will appreciate that changes can be made in form and detail. For example, a method and apparatus in accordance with our invention can be used to plate various types of materials, e.g. nickel phosphorus alloys, other metals, or non-metallic materials. The method and apparatus can be used to plate workpieces other than magnetic disk substrates. As used herein, “workpieces” encompasses articles to be plated. When practicing the invention, one can either a) place the plating solution in the bath prior to placing substrates in the bath; b) place the substrates in the bath prior to placing the plating solution in the bath; or c) place the plating solution and substrates in the bath simultaneously.

In some embodiments, the mandrels may comprise concave regions for holding a portion of the arc of the outer edge of the substrates being plated. Also, in some embodiments, there may be sufficient clearance for the substrates to have some degree of movement while being held by the mandrels, whereas in other embodiments, the substrates may be firmly held by the mandrels.

Pins 50 and 56 and locking pieces 26 can be tied to strings (not shown) so that they can easily be retrieved if they accidentally fall into bath 8. In lieu of engaging with gear GL, pin 56 can be pushed through wall 10R and engage with end piece ER.

It is also noted that one aspect of the invention as described above may be practiced without practicing other aspects of the invention. Accordingly, all such changes come within our invention.

Claims

1. Apparatus comprising: a holder for holding workpieces in a plating bath; a bearing having a first race and a second race, said first race being coupled to said holder, said second race being rotatable with respect to said first race, said first and second races being non-metallic, a metal mechanical interface between said first and second races; and a rotating member coupled to said second race of said bearing for imparting motion to said holder.

2. Apparatus of claim 1 wherein the metal mechanical interface reduces the amount of contaminant particle generation that would occur if said holder slid against said member.

3. Apparatus of claim 2 wherein said metal mechanical interface comprises a set of balls or rollers.

4. Apparatus of claim 3 wherein said workpieces are magnetic disk substrates, said apparatus comprising a set of gears for imparting planetary motion to said substrates.

5. Method for plating comprising: placing one or more workpieces within a holder; placing said holder in a plating bath; and imparting motion to a mechanical member, said mechanical member being coupled to a first race of a bearing, said holder being coupled to a second race of said bearing, said first and second races being plastic, a metallic interface being provided between said first and second races, said mechanical member imparting motion to said holder via said bearing.

6. Method of claim 5 wherein said mechanical member comprises a rotating wheel, said first race being coupled to said wheel, and said metallic interface comprises balls or rollers.

7. Method of claim 6 wherein planetary motion is imparted to said one or more workpieces, and said workpieces are magnetic disk substrates.

8. Apparatus comprising: a plating bath; a holder comprising a central mandrel and a plurality of other mandrels, said holder for holding a plurality of sets of workpieces such that each set of said workpieces is held by at least one of said other mandrels and against an associated side of said central mandrel, said holder holding said workpieces in said plating bath; and a mechanical member imparting motion to said holder.

9. Apparatus of claim 8 wherein said workpieces are magnetic disk substrates and said mechanical member comprises a wheel for rotating said holder.

10. Apparatus of claim 9 further comprising a set of gears for imparting planetary motion to said holder.

11. Apparatus of claim 10 wherein at least one of said other mandrels is removable to facilitate loading and unloading of said substrates into said holder.

12. Method for plating comprising: placing a plurality of sets of workpieces in a holder, said holder comprising a central mandrel and a plurality of other mandrels, each set of said workpieces being held against an associated side of said central mandrel and against an associated plurality of said other mandrels; placing said holder in a plating bath; and applying motion to said holder.

13. Method of claim 12 wherein said applying motion to said holder comprises applying planetary motion to said holder.

14. Method of claim 13 wherein said workpieces are magnetic disk substrates, said substrates have an opening, and said placing of said substrates in said holder comprises: providing a tool having a tool mandrel extending through the openings of said set of substrates; manipulating said tool mandrel so that said set of substrates rests against said central mandrel and at least one of said other mandrels; and removing said tool mandrel from said openings of said set of substrates.

15. Method of claim 14 further comprising removing said substrates from said holder, said removing comprising: removing said holder from said bath; placing said tool mandrel into said openings of said substrates; and lifting said substrates out of said holder.

16. Plating apparatus comprising: a container for holding a plating solution; one or more elongated members for holding a plurality of workpieces in said plating solution; and first and second metallic plates adjacent first and second sides of said plurality of workpieces.

17. Apparatus of claim 16 wherein the presence of said metallic plates increases the similarity of the plating conditions of the workpieces adjacent to said metallic plates to the plating conditions of the workpieces that are surrounded by other workpieces.

18. Method comprising: placing a plurality of workpieces in a holder, said holder comprising first and second metallic plates adjacent first and second sides of said plurality of workpieces; placing said holder and plurality of workpieces in a plating solution.

19. Method of claim 18 wherein the presence of said metallic plates increases the similarity of the plating conditions of the workpieces adjacent to said metallic plates to the plating conditions of the workpieces that are surrounded by other workpieces.

20. Method comprising: providing a substrate holder having one or more mandrels for holding a set of workpieces at an outer edge of said workpieces, said workpieces having an inner opening, said one or more mandrels being held at least at one end by an end piece; holding said set of workpieces by inserting an elongated tool through said inner openings of said set of workpieces; and moving said set of workpieces with said elongated tool so that said workpieces rest against said one or more mandrels, said end piece having a slot therein, said act of moving comprising moving said tool through said slot.

21. Method of claim 20 further comprising coupling one or more removable mandrels to said end piece, said removable mandrels holding said workpieces in place.

22. Method of claim 20 further comprising placing said holder into a plating bath and plating material onto said workpieces.

23. Method of claim 22 further comprising removing said holder from said plating bath and removing said workpieces from said holder.

24. Method of claim 23 wherein said workpieces are magnetic disk substrates and said holder comprises two end pieces, each end piece being coupled to an associated end of said mandrels.

25. Method comprising: providing a set of workpieces in a holder in a plating bath, said holder comprising a set of mandrels coupled to an end piece, said workpieces being held at their outer edges by said mandrels, said workpieces having an inner opening, said end piece comprising a slot for accommodating a tool; removing said holder and workpieces from said plating bath; passing an elongated tool into said inner opening of said workpieces; and withdrawing said workpieces from said holder with said tool, said method comprising passing said tool through said slot.

26. Method of claim 25 wherein said workpieces are magnetic disk substrates, and said holder comprises two end pieces, each of said mandrels being coupled to said two end pieces.

27. Method of claim 25 wherein at least one of said mandrels is removable, said method further comprising removing said at least one removable mandrel from said holder prior to withdrawing said elongated tool into said inner opening of said workpieces.

28. Apparatus comprising: a set of mandrels for holding a set of workpieces at an outer edge of said workpieces, wherein said workpieces each have a central opening; a first end piece coupled to a first end of said mandrels; a second end piece coupled to a second end of said mandrels, said second end piece having a slot therein for accommodating a tool, wherein said workpieces are loaded into said apparatus by inserting said tool through said inner openings and sliding said tool through said slot so that said workpieces rest against said mandrels.

29. Apparatus of claim 28 wherein at least one of said mandrels is removable from said apparatus.

30. Apparatus of claim 28 further comprising a gear system for imparting planetary motion to said workpieces.

31. Apparatus comprising: a holder comprising one or more elongated members for holding workpieces; a stationary member having an opening; a pin for extending through said opening in said stationary member and engaging with said holder to prevent said holder from moving during loading and unloading of said holder.

32. Apparatus of claim 31 wherein said stationary member is a wall of said apparatus, said apparatus further comprising a second wall, said first and second walls holding a gear mechanism for imparting motion to said holder.

33. Apparatus of claim 31 further comprising a gear coupled to said holder, wherein said pin engages with teeth of said gear.

34. Apparatus of claim 31 further comprising a gear coupled to said holder, wherein said pin engages with an opening in said gear.

35. Method comprising: placing a pin through a stationary member so that said pin engages with a holder for holding workpieces; loading workpieces into said holder, said pin preventing said holder from moving during loading.

36. Method of claim 35 further comprising; removing said pin from said holder; and placing said holder and said workpieces in a plating solution to plate said workpieces.

37. Method of claim 36 further comprising: removing said holder from said plating solution; causing said pin to engage with said holder; and unloading said workpieces from said holder.

38. Method of claim 35 wherein said holder is coupled to a gear and said pin engages with teeth of said gear.

39. Method of claim 35 wherein said holder is coupled to a gear and said pin engages with an opening in said gear.

40. Method comprising: providing a holder containing workpieces; placing a pin through a stationary member to engage with said holder to thereby prevent said holder from moving; and removing said workpieces from said holder.

41. Method of claim 40 wherein said holder is coupled to a gear and said pin engages with teeth of said gear.

42. Method of claim 40 wherein said holder is coupled to a gear and said pin engages with an opening in said gear.

43. Apparatus for plating substrates, said substrates being planar and having a centrally defined opening, said apparatus comprising: a plating bath; and a holder comprising a plurality of mandrels for holding said substrates at their outer edges in said plating bath.

44. Apparatus of claim 43 wherein at least one of said mandrels is removable for facilitating the loading and unloading of said substrates from said holder.

45. Apparatus of claim 43 further comprising a gear mechanism for imparting planetary motion to said holder.

46. Method comprising: placing substrates in a holder, said substrates being generally planar and having an opening therein, said holder comprising a plurality of mandrels for holding said substrates at outer edges of said substrates; placing said holder and said substrates in a plating bath; and plating said substrates.

47. Method of claim 46 further comprising: removing at least one of said mandrels from said holder prior to placing said substrates in said holder; and placing said at least one mandrel back onto said holder after placing said substrates in said holder.

48. Method of claim 46 further comprising imparting planetary motion to said substrates during plating.

49. Method comprising: removing a holder from a plating bath, said holder comprising a plurality of mandrels for holding a set of generally planar substrates at outer edges of said substrates, said substrates having an opening therein; removing at least one of said mandrels from said holder; and removing said substrates from said holder.