US3189532A

US3189532A - Process for making conductive-core magnetic device

Info

Publication number: US3189532A
Application number: US30362A
Authority: US
Inventors: Eric T K Chow; Harry L Watkins
Original assignee: NCR Corp
Current assignee: NCR Voyix Corp; National Cash Register Co
Priority date: 1960-05-19
Filing date: 1960-05-19
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15
Also published as: NL265014A; CH394299A; BE603829A; GB905476A

Description

June 15,1965

E- T. K- CHOW ETAL PROCESS FOR MAKING CONDUCTIVE-CORE MAGNETIC DEVICE Filed' May 19, 1960 2 u. .1; t 91:: 3: 5: f 't. I I c! in; 'gg u; 5 55: 1 20 k0 PROCEDURE OUTLINE I 1. Clean wire with alkaline cleaner.

2. Rinse with distilled water.

3 Remove thin surface layer with conc. HNO sat. 4 Rinse with distilled water.

5- Electroplate on iron-nickel thin layer. 6. Rinse with distilled water. 7. Dry with acetone.

6. Apply protective urethane resin coat.

INVENTORS Eric T.K. Chow Harry L. Watkins ATTORNEYS United I States Patent 3,189,532 PROCESS FOR MAKING CONDUCTIVE CORE' MAGNETIC DEVICE Eric T. K. .Chow and HarryL. Watkins, Califl, assignors to The National CashRegister Company, Dayton, Ohio, a corporation of Maryland I Filed May 19, 1960,'Ser. No. 30,362

3 Claims. ((1204-28) The present invention is in the field of magnetic devices used, for example, as logical elements and/or informationstore devices in information-processing systems such as digital computers. More particularly, the invention relates to an improved process of producing slender rod-like bistable magnetic devices having as a core a small gauge stiti resilient non-magnetic electric conductor with an bistable. magnetic devices having as a core a small-gauge herent thin electroplated layer of iron-nickel composition, and the improved product produced by the process.

As indicated foriexample, incopending application Serial No. 791,695, of Tsu, and in copending application Serial No. 827,412, now US. Patent No. 2,94s,2 17 of Fisher et al., prior investigations have proven the merits of fine-gauge rod-like bistable magnetic devices having oriented magnetic films, employed as binary informationstore or memory elements and as logical elements in computer systems. A first type of device of this nature comprises a resilient base of an electrically non-conductive material such as glass, with an oriented thin film of adherent bistable'magnetic materiaL' A second type of such device comprises a resilient base formed of electrically conductive material such as a copper alloy wire and an electrolytically applied layer or film of bistable magnetic material which in the finished devices has been so applied or so disposed that there is an easy direction of magnetization which is oriented at an angle to the longitudinal axis of the device. Orientation of the direction of easiest magnetization may be attained either by deposition of the magnetic material under the influence of a properly oriented magnetic field (as in Fisher et al., supra), or, in some cases, by mechanical operations such as by mechanically twisting the base wire before or after applicat on of the magnetic material, or by scratching or grooving the wire to provide spirally oriented deformations or alterations of the surface of the wire (as in Tsu, supra), and

which deformations cause the magnetic material to have a similarly oriented'easy direction of magnetization. The orientation of the magnetization characteristic of the material as just briefiy described is for the purposeof permitting reversal of the direction of the magnetization, that is, reversal of the remanent state of the bistable magnetic material, by a current in one direction or the other through the conductive core or'base concurrently aided by one or more currents passed through coils encircling the rod-like device. In general it has not been contemplated that this second'type or class of magnetic devices would be useful in the absence of the spiral orientation of the magnetic axis of the magnetic material. I i

It is to a typeof device somewhat similar to the men- Los Angeles,

in respect to different devices produced in ditferent v batches or production lots.

Briefly, in accordance with the invention a stiff resilient wire or fine-gauge rod of copper-beryllium alloy is thoroughly cleaned and rinsed in or with distilled water in accord with a special procedure, and is immediately electroplated in a special electrolytic bath to produce a thin film of bistable magnetic material comprising a high percentage' of iron and a minor proportion of nickel on the peripheral surface of the wire or fine-gauge rod, along the length thereof. The preferred composition of magnetic material is about 97% to 98% iron and 3% to 2% nickel, by weight, although acceptable devices may be produced with the composition ranging from about 93% to 99% iron and the remainder nickel. In general the switching time (time for reversal of stable state) of the material is shortened as the percentage of nickel in the composition is decreased. While the magnetic materialmay be and preferably is electroplated onto the wire while the latter I is disposed in a magnetic field so directed relative to the wire that the magnetic material is oriented along the Wire similar tovv that disclosed in copending application for US.

patent, Serial No. 802,494, now abandoned, filed March 27, 1959, by Richard M. Clinehens and Donal A. Meier; or the electrolyte may be that hereinafter specifically described.

Previous efforts to prepare bistable magnetic rod-like devices of the general type forming the subject of the present invention met with indifferent and extremely variable results. The magnetic characteristics of the material, such as the coercivity and rectangularity" of the magnetization or hysteresis characteristic curve, varied considerably along the length of the wire or rod-like device. Since the devicesare intended to be used as long lengths and in large numbers in magnetic data-store matrices, rather than as very short individual portions, it

is extremely desirable that the magnetic characteristics be as uniform as possible throughout'the entire length of each rod-like device and from device to device among a large number of the devices. Prior to the present invention, no reasonable or acceptable degree of uniformity of the magnetic characteristics could be attained when electrically conductive wires or rod-like cores were used. The previously acceptable rod-like bistable magnetic devices of the general character of those provided by the present invention were ofa type using a slender glass (non-conductor) filament as a base structure for supporting the magnetic material. The devices using glass filament as a base, are, however, relatively expensive because of the high cost of uniform filaments and due to the relatively complicated procedurere quired to produce acceptable and uniform magnetic devices. The stiff resilient copper-beryllium wire base usedaccording to the present invention is relatively inexpensive and, when prepared and electroplated according to the invention, provides long lengths, of. magnetic 'rod-likex bistable' dc.-

Patented Jime 15, 1965 vices possessing exceptionally superior magnetic charac-' teristics and of excellent uniformity. Further, the process steps required in production of the devices are by the invention greatly simplified and reduced in number, thus both improving the device from the engineering standpoint and considerably reducing the cost per unit length of the devices.

From the preceding general description of the nature of the invention it is evident that a principal object of the invention is to provide an improved bistable magnetic rodlike device having a resilient rod-like electrically conductive base supporting a magnetic film or plate of excellent magnetic characteristics and improved uniformity, the magnetic material having either no easiest direction of magnetization (unoriented), or oriented to have an easiest direction of magnetization longitudinally of the conductive base. Another object is to provide a simpler and less expensive process for production of slender rodlike devices having a thin film or layer of bistable magnetic material supported by a stiff resilient electrically conductive rod-like (wire) base.

Another object is to provide a stiff, resilient, very slender rod-like magnetic device having a surface layer of bistable magnetic material of uniform characteristics and which device is not brittle.

Another object of the present invention is to provide improvements in slender rod-like magnetic devices suit able for use as core-stock or cores for magnetic information-store or magnetic switch devices.

Other objects and advantages of the invention will become evident or made so in connection with the appended claims and the following explanation of the process and description of.the product comprised in theinvention. The product is illustrated in the drawings, in which:

FIG. 1 is a view, greatly magnified, of a magnetic device comprisinga stiff resilient conductive core and a thin adherent layer of magnetic material possessing a substantially rectangular magnetic hysteresis characteristic as plotted on Cartesian coordinates, the proportions being distorted to facilitate illustration and an intermediate portion of the device having been broken away;

FIG. 2 is a partly diagrammatic and grossly enlarged view depicting a length of a magnetic device such as is illustrated in FIG. 1, with exemplary windings units comprising plural-turns coils, encircling respective assigned portions of the device, with one of the windings units shown in the section and with an intermediate portion of the device broken out to facilitate illustration;

FIG. 3 is a procedure table outlining the major procedural steps of the process of producing the device depicted in FIG. 1.

Referring first to FIG. I, the stiffresilient rod-like magnetic device is denoted generally by the ordinal 10, and comprises essentially a stiff resilient or spring-like filament or wire 20 of an alloy of copper and beryllium, and a very thin adherent film or coating 30 of magnetic material. The rod-like alloy filament or wire. 20, may be of the type which has been heat-treated to give it stiffness and resilience. The magnetic material, which is electrolytically deposited on the wire in accord with a procedure and by means hereinafter described, i com posed essentially of a large major proportion of iron and a small minor proportion of nickel, and is such asv to possess a substantially rectangular magnetization hysteresis characteristic curve. The preferred proportions of iron to nickel are of the order of 97 parts iron to 3 parts nickel, by weight; however, usable devices are producible with the percentage of iron in the range from 93 to 99 and the percentage of nickel in the range from 7 to 1, all by weight. The relative percentages of iron and nickel may be varied by variation of the proportion of iron and nickel salts in the electrolyte bath in which the magnetic material is electro-plated onto the rod-like base. The copper-beryllium rod or wire base is of fine gauge, that is, of the order of from five to fifty mils in maximum 4 cross-sectional dimension (diameter, in the case of a wire circular cross-section); and a preferred examplary form is a very springy straight wire of twelve mils diameter. A preferred exemplary magnetic film or layer is one of 97 parts iron and 3 parts nickel by weight, of the order of 3000 angstroms thick (as computed by indirect meth- ,ods), and is possessed of a very rectangular hysteresis characteristic curve as plotted in Cartesian coordinates, and is preferably unoriented. While the rod-like base member may be as small as five mils or as large as fifty mils in diameter in special cases, and the magnetic coating as thick as 10000 angstroms or as thin as 500 angstroms for certain special applications, the above given preferred dimensions have been found to provide devices having sufficient strength and rigidity to permit handling without necessity for exercise of unusual care, and having excellent magnetic characteristics for use in data-store arrays and matrices.

In use in an information-store apparatus, a suitably long length of the coated rod-like device is used in conjunction with a series of spaced-apart coil units, such ascoil units 40 illustrated in FIG. 2 of the drawings. The coil units 40 are there shown disposed on a magnetic device 10 which comprises a stiff resilient copperberyllium wire base 20' and an adherent thin layer or film of bistable magnetic material. Each coil unit comprises a plurality of plural-turns single-layer solenoidcoils arranged in generally concentric relationship and encircling a respective small length or portion of the magnetic thin film 30. An exemplary coil unit as shown comprises three superposed coils such as 40a, 40b, and 400, each of ten turns of conductor, and each having a respective pair of coil leads such as 40a'-40a, 40b- 40b", and 406-400". The conductors are insulated, and

' may be in the form of fiat wires, stranded wires, parallellaid fiat wires, or other suitable forms. The coil units are in use spaced along the magnetic rod-like device 10 sufficiently far apart to obviate undesirable mutual magnetic interactions; and this spacing may alternatively be effected by winding the coil units on the rod-like magnetic device or, and preferably, by the coil units being disposed in arrays or matrices in coaxial relationship along bores in an embedment (not shown). In the latter arrangement coil units are relatively fixed in coaxial disposition with respect to each other by the embedding compound and they and bores coaxial with the coil units and extending through the embedding material are of internal diameter suitable for easy insetrion of the magnetic rodlike devices into the bores and thrugh the coil units. As many coil units as may be desired are arranged or disposed in spaced-apart relationship along a magnetic rod-like device, in either of the described modes; and for example, the number of coil units arranged for cooperation with respective portions of a magnetic rod-like device may be forty, or more, or less. Each coil unit thus cooperates with its own respective portion of the long magnetic film. Examplary ten-turn coils may be of the order of one sixteenth of an inch in length. The general nature of the bistable magnetic film, the coils of the units, and the interactions therebetween are like or similar to those described and explained in copending application of Donal A. Meier, Serial No. 728,739, filed April 15, 1958, now abandoned, to which reference may be had forfurther details in respect to these matters. The present invention provides and presents improvements over the'procedures and devices disclosed in the aid application Serial No.'728,739.

With reference to FIG.'3, the preferred electrolyte plating bath and procedure for producing the improved device will next be disclosed and explained. Prior to being subjected to electroplating action in the electrolytic bath, the copper-beryllium alloy wire is subjected to a thorough cleaning in a suitable alkaline cleaning bath (step 1). As an example, a solution of the commercially available product named Shipleys Alkaline Cleaner I (step 2).

isf'found to give excellent results. Immediately follow: ing the alkaline" bath treatment, the copper-beryllium base rod or wire is thoroughly rinsed with distilled water thinsurface layer of the, copper-beryllium alloy (step 3);

and the acid treatment is immediately followed by a tion made up from 290 grams of FcCl -4H O, 12 grams of NiCI -6H O and 238 grams of CaCl per liter of solution, with addition of dilute l-lCl. if necessary, to bring the pH to a value of 1001005. Enough iron powder or iron wool to make certain that the solution is ferrous rather than ferric may be added to the electrolyte bath. An acceptable procedure for effecting the electroplating is to progressively pass or draw the wire or rod" downwardly through a three-inch long zone of contact with the electrolyte at a speed of about five inches per minute, using a plating current of from 12 to 25 milliamperes, at room temperature. Care should be exercised to apply the plating current uniformly over the exposed length and periphery of the base or wire; and this may be effectively accomplished by employing a tubular or spiral anode electrode through and along the axis of which the wire is traversed or'drawn. The wire is connected to the current source as the cathode of the system. The exposure time and current density may be varied somewhat, depending upon the thickness of plating desired, and the size of wire. The preceding data relate to plating of an exemplary copper-beryllium wire of ten mils diameter. Analysis of the plating deposited on the exemplary wire indicates a content of approximately 97% iron and 3% nickel by weight, with permissible variation of +-3% in the iron content. It may be noted that if more rapid switching of the produced magnetic devices is desired, the switching time may be lowered by using a somewhat lower concentration of NiCl -tSH O in the electrolyte; for example, 8 to 10 grams per liter of solution. Using concentrations of the order of that just noted, switching times faster than 25 millimicroseconds are attainable.

Immediately following electroplating, the plated wire is thoroughly rinsed with water (step 6) and immediately dried as by means of an acetone bath or spray (step 7); and the dried device is then immediately given a protective coating to avoid oxidation or other degradation of the iron-nickel magnetic film or coat. The protective coating may be applied by dipping the dried device in a suitable moisture proof self-curing resin; and satisfactory protection has been secured using a commercially available resin. As soon as the resin or other protective coating has cured or dried, the magnetic device is ready for association with coil units as a data-store unit element.

While previous efforts to produce a bistable magnetic coating of unstressed and/or unoriented magnetic material on a stiff resilient wire have failed to provide devices The wire is then immersed in a concentrated nitric acid solution for aperiod sufficient to remove a having acceptably uniform magnetic characteristics along long lengths of the wire and have failed to produce magnetic rod-like. devices capable of providing as high output voltage and as large signal-to-noise ratio as characterize the now well known glass-filament type of rod-' like magnetic thin-film device, the procedure of the present invention provides long lengths of resilient conductivebase bistable magneticrod-likedevices of eminently uni-.

form magnetic characteristics not only along the length of any such long device but from device to device of. a batch thereof, and from'batch to bath, and also produces devices having as high output potentials and equally good signal-to-noise ratios as characterize the glass-filament type of device when both are tested under identical conditions with the same apparatus. The simplification in the gen-excluding protecting film over the deposited. magnetic.

procedure of producing the deyice's'i's of greate merit, eliminating" among other things'the steps of applying a thin-film silver substrate layer as a base for the magnetic material and the difficulties attending that operation. Furher by permitting the successful production of uniformly-alike magnetic devices with a base material much cheaper than the previously used glass filament base material, a considerable cost saving is effected in the production of bistable magnetic devices of the type under consideration. Since the rod-like devices are of the order of from about ten mils to as much as fifty mils in diameter (preferably about fifteen mils forthe usual informationstore or memory applications) it is seen that they also possess equally with the better-known glass-filament rod-' like magnetic devices the distinct and meritorious advan-' tages over toroidal and slotted tubular magnetic devices of much simpler winding, much greater packin'g'density (bits per unit of space in a memory device), much smaller driving energy and much faster operation. When the relatively higher cost and complicated and painstaking process of producing the similar glass-rod type of device is considered, the considerable advantages of the process and device of the present invention become apparent.

While the procedure and the resulting product of theinvention have been disclosed in detail it is evident from the disclosure that some latitude in specific details is permissible, and accordingly it is desired that the scope of a the invention be restricted. only in accord with the definition of the invention as portrayed in the appended claims.

What is claimed is: 1. A process of producing a slender 'od-like bistable magnetic device'having a thin iron-nickel film-like coatingexhibiting a uniform substantially rectangular magnetic hysteresis characteristic throughout a long length of the device, said process consisting essentially of: providing a long length of a stiff resilient copper-beryllium wire having a diameter of the order of 5 to mils to serve as the core of said magnetic device, cleaning said copper-beryllium wire in an alkaline cleaning solution, immediately rinsing the cleaned wire with distilled water,

then immersing the wire in a nitric acid bath for a period each portion of the wire in the plating bath being chosen so as to produce on the wire an adherent uniform bistable magnetic layer having a thickness ranging from 500 to 10,000 angstroms and composed of from about 93% to about 99% iron and from about 7% to about 1% nickel over the surface of a long length of the wire.

2. A process according to claim 1, including thestep of providing a longitudinally oriented magnetic field in which the electroplating is accomplished, whereby to produce a corresponding orientation of an easy direction of magnetization of the magnetic plated onto the wire core. 3. A process according to claim 1, including the steps of providing a longitudinally oriented magnetic field in the region in whichthe electroplating is effected whereby to produce a longitudinally oriented magnetic layer, washing anddrying the resulting product, and applying an oxylayer,

References Cited by the Examiner UNtrED STATES PATENTS. J 1,791,642 2/31 Schulte 20'443 1,965,399 7/34 Wehe 2041.5 2,507,400 5/50 De Marinis 204 -43 .(Otherreferences on following page) UNITED STATES PATENTS OTHER REFERENCES Znpponi 204-43 Naw Advances in Printed Circuits, US. Dept. o Sukaccv 29-1S5.5 Commercc Publication 192, Nov. 22, 1948, pp. 25 and 2 Beach et a1 20432 relicd on.

Austen 29--155.5 5

A t 34() 174 WINSTON A. DOUGLAS, Primary Examiner. Robinson 204-15 Fisher at a! 340 174 figk g ng lf ggg ns, JOSEPH REBOLD, 10m Mitchell.

Eggenberger ct a1 20443 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,189,532 June 15, 1965 Eric T. K. Chow et 211.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 15, for "small gauge-" read small-gauge line 17, strike out "bistable magnetic devices having as a core a small-gauge"; line 18, for "herent" read adherent line 27, for "this" read that line 64, for "iron-neckel" read ironnickel column 4, line 2, for "examplary" read exemplary line 48, for "insetrion" "read insertion line 49, for "thrugh" read through column 5, line 71, for "bath" read batch column 6, line 1, for "greate" read great line 5, forj'Furher" read Further Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A PROCESS OF PRODUCING A SLENDER ROD-LIKE BISTABLE MAGNETIC DEVEICE HAVING A THIN IRON-NICKEL FILM-LIKE COATING EXHIBITING A UNIFROM SUBSTANTIALLY RECTANGULAR MAGNETIC HYSTERESIS CHARACTERISTIC THROUGHOUT A LONG LENGTH OF THE DEVICE, SAID PROCESS CONSISTING ESSENTIALLY OF: PROVIDING A LONG LENGTH OF A STIFF RESILIENT COPPER-BERYLLIUM WIRE HAVING A DIAMETER OF THE ORDER OF 5 TO 50 MILS TO SERVE AS THE CORE OF SAID MAGNETIC DEVICE, CLEANING SAID COPPER-BERYLLLIUM WIRE IN AN ALKALINE CLEANING SOLUTION, IMMEDIATELY RINSING THE CLEANED WIRE WITH DISTILLED WATER, THEN IMMERSING THE WIRE IN A NITRIC ACID BATH FOR A PERIOD OF TIME SUFFICIENT TO ETCH ONLY A SUBSTANTIALLY COMPLETE SURFACE LAYER OF THE WIRE, IMMEDIATELY RINSING THE ETCHED WIRE WITH DISTILLED WATER, AND THEN PRIOR TO APPRICIABLE CHEMICAL DEGRADATION OF THE WIRE SURFACE, ELECTROPLATING THE WIRE IN A NICKEL CHLORIDE-IRON CHLORIDE AQUEOUS SOLUTION HAVING A PH OF THE ORDER OF 1.00$0.05 BY CONNECTING THE WIRE AS THE CATHODE OF THE SYSTEM AND PASSING THE WIRE THROUGH A SPIRAL ANODE ELECTRODE ALONG THE AXIS OF THE WIRE, THE PLATING CURRENT AND THE TIME OF EXPOSURE OF EACH PORTION OF THE WIRE IN THE PLATING BATH BEING CHOSEN SO AS TO PRODUCE ON THE WIRE AN ADHERENT UNIFORM BISTABLE MAGNETIC LAYER HAVING A THICKNESS RANGING FROM 500 TO 10,000 ANGSTROMS AND COMPOSED OF FROM ABOUT 93% TO ABOUT 99% IRON AND FROM ABOUT 7% TO ABOUT 1% NICKEL OVER THE SURFACE OF A LONG LENGTH OF THE WIRE.