GB1591237A

GB1591237A - Magnetic recording/reproducing head

Info

Publication number: GB1591237A
Application number: GB4523677A
Authority: GB
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1976-12-13
Filing date: 1977-10-31
Publication date: 1981-06-17
Also published as: JPS5374411A; NL7712685A; FR2373850A1; DE2755513A1

Description

(54) MAGNETIC RECORDING/REPRODUCING HEAD (71) We, TEXAS INSTRUMENTS INCORPORATED, a Corporation organized according to the laws of the State of Delaware, United States of America, of 13500 North Central Expressway, Dallas, Texas, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to magnetic recording and/or reproduction heads, and more particularly to an improved metal alloy magnetic recording and reproduction head.

In some applications of recording and reproducing information on a magnetic recording media, it is desirable to utilize a metal alloy recording and reproduction head. The advantages of using such metal alloy (non-ferrite) recording and reproduction heads, comprised, for example, of a well-known alloy such as Alfesil, Alfenol, Sendust or Duraperm, include long wear, the ability to provide excellent gap definition, immunity from gap erosion and good magnetic properties. A major disadvantage of present metal alloy magnetic recording heads is that the metal, being very hard, is alsci very brittle and cannot be conventionally machined, but must be carefully ground or lapped. Previous attempts to use such metal alloy to form the pole pieces or core halves of magnetic recording heads have resulted in low yield, poor efficiency and poor RF response caused by degradation of the permeability of the material during manufacturing. Accordingly, metal recording and reproduction heads are infrequently used, particularly, in magnetic tape or other flexible magnetic recording media systems which require high performance such as video and high-density digital recording systems.

It is therefore an object of the present invention to provide improved metal magnetic recording and reproduction heads.

According to the present invention there is provided a magnetic recording and/or reproduction head comprising first and second magnetizable metal members bonded together with a gap of predetermined thickness formed between said metal members and extending to a media-engaging end thereof, said metal members being bevelled at said media-engaging end with said one end being of reduced thickness corresponding to the track width of a magnetic-type information storage media as determined by the slope and extent of said bevelled surface.

The advantages that may be obtained from the invention are higher yield, a simplified manufacturing process, excellent and stable gap definition; and, the synergistic effects of improved reluctance ratio between the front gap and the back gap, improved RF response and greater RF output level.

Still further objects and advantages of the invention will become apparent from the detailed description and claims when read in conjunction with the accompanying drawings wherein: Figure 1 is a perspective view of an embodiment of a metal magnetic recording and reproduction head in accordance with the invention; Figure 2a is a top view of the magnetic recording and reproduction head of Figure 1; Figure 2b is an end view of the magnetic recording and reproduction head of Figure 1; and Figure 2c is a front elevation of the magnetic recording and reproduction head of Figure 1.

Referring then to the Figures, it is seen that two matching core halves 1 0a and 10b are joined together as shown by a bonding material 15 formed within the opening 14.

The separation g between the poles or core halves 10a and 10b is commonly referred to as the "gap" and forms a high reluctance path in the magnetic circuit. The most critical aspect of any magnetic recording and reproduction head is the "gap", and it is essential to have a well-defined gap of an exact predetermined length g. Gap length g is defined and maintained by a non magnetic material 13a, 13h and 13e of the exact predetermined thickness which serves as a spacer between core halves ionic and 100.

Another critical parameter of the magnetic recording and reproduction head is the "track width" tw which must be produced within a small tolerance such as, for example, -tl mil. In prior art metal recording beads, the "track width" thickness is merely the thickness of the head itself. Since most high performance heads require very narrow track widths, usually in the range of 4-6 mils, and the track width and thickness of the base portion of the head are the same, this results in a very thin-bodied, fragile head. The weakest point of the prior art head is the fragility caused by having reduced the thickness of the bonding material which hold the two core halves together; the bonding material is reduced to such a thinness that it loses most of its tensile strength. Since the definition and maintenance of the "gap" is largely dependent upon the ability of the bonding material to hold the core halves tightly together, a bonding section, weakened by making it too thin, results in gap separation which is a serious production problem.

The illustrated wedge-shaped head of the present invention, on the other hand, includes a larger base or body thickness bt which is considerably thicker than the track width tw of 3-10 mils and a body thickness bt of from 12-25 mils or more.

A synergistic effect of the wedge shape is that it also improves the reluctance ratio between the front gap 13a and the back gap 13b; this favourably affects the performance of the head.

The illustrated metal magnetic recording and reproduction head is manufactured by providing two matching core halves 1 0a and 10b of a magnetic alloy such as Alfesil, Sendust, Alfenol or Duraperm which are metal alloys consisting of approximately 84.5% Fe, 9.5% Si and 6.0% Al. A layer of nonmagnetic material such as aluminium oxide (Al2O3) is deposited by evaporation, for example, on one end of each core half to 1/2 the gap thickness (g/2). The two core halves are then placed together so that the end grooves fit together to form the opening 14 which is then filled with a bonding material such as a brazing alloy comprised of Ag Cu-Pd to hold the two halves together. One edge of the assembly is then lapped to form the bevel. A thin insulated copper wire 1.5 mils in diameter (49 gauge), for example, is wrapped in a "figure 8" configuration through the opening 12 around the groove gila, back through the opening 12, around the groove lib, back through the opening 12, etc, until, for example, a total of four turns is made on each core half.

In one embodiment of the above metal magnetic recording and reproduction head, the body thickness bt is between 12 and 15 mils in thickness, and the "track width" tw between 4 and 6 mils in thickness. The gap g is about 40 IL inches. The overall length is between .14 and .18 inches, and the overall height is between .12 and .17 inches. The bevelled portion is cut to precisely define the "track width" (tw); the length s is not critical, but may be, for example, between 25-40% of the total height, or in the above example, between .03 and .07 inches.

An embodiment of a metal magnetic recording and reproduction head in accordance with the present invention has now been described in detail along with the method of making the same. This tape head has been found particularly useful in high performance flexible disc video and highdensity digital recording systems such as those described in United States of America patent specification no. 4,079,427.

Various modifications may be made to the above-described embodiments such as utilizing materials of different constitution, changing the shape or size of the metal core halves, etc. Since it is obvious that these and many additional changes and modifications can be made in the above-described details without departing from the scope of the invention, it is understood that the invention is not to be limited to said details except as set forth in the appended claims.

WHAT WE CLAIM IS: 1. A magnetic recording and/or reproduction head comprising first and second magnetizable metal members bonded together with a gap of predetermined thickness formed between said metal members and extending to a media-engaging end thereof, said metal members being bevelled at said media-engaging end with said one end being of reduced thickness corresponding to the track width of a magnetic-type information storage media as determined by the slope and extent of said bevelled surface.

2. The recording and/or reproduction head according to Claim 1, wherein said magnetizable metal is an alloy of iron, silicon and aluminium.

3. The recording and/or reproduction head according to Claim 2, wherein said alloy consists of approximately 84.5% iron, 9.5% silicon and 6% aluminium.

4. The recording and/or reproduction head according to Claim 1, wherein said metal members are between 12-25 mils thick in the region forming the body of said recording and/or reproduction head, and wherein said members are bevelled to a media-engaging end thickness of between 3-10 mils.

5. The recording and/or reproduction

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. magnetic material 13a, 13h and 13e of the exact predetermined thickness which serves as a spacer between core halves ionic and 100. Another critical parameter of the magnetic recording and reproduction head is the "track width" tw which must be produced within a small tolerance such as, for example, -tl mil. In prior art metal recording beads, the "track width" thickness is merely the thickness of the head itself. Since most high performance heads require very narrow track widths, usually in the range of 4-6 mils, and the track width and thickness of the base portion of the head are the same, this results in a very thin-bodied, fragile head. The weakest point of the prior art head is the fragility caused by having reduced the thickness of the bonding material which hold the two core halves together; the bonding material is reduced to such a thinness that it loses most of its tensile strength. Since the definition and maintenance of the "gap" is largely dependent upon the ability of the bonding material to hold the core halves tightly together, a bonding section, weakened by making it too thin, results in gap separation which is a serious production problem. The illustrated wedge-shaped head of the present invention, on the other hand, includes a larger base or body thickness bt which is considerably thicker than the track width tw of 3-10 mils and a body thickness bt of from 12-25 mils or more. A synergistic effect of the wedge shape is that it also improves the reluctance ratio between the front gap 13a and the back gap 13b; this favourably affects the performance of the head. The illustrated metal magnetic recording and reproduction head is manufactured by providing two matching core halves 1 0a and 10b of a magnetic alloy such as Alfesil, Sendust, Alfenol or Duraperm which are metal alloys consisting of approximately 84.5% Fe, 9.5% Si and 6.0% Al. A layer of nonmagnetic material such as aluminium oxide (Al2O3) is deposited by evaporation, for example, on one end of each core half to 1/2 the gap thickness (g/2). The two core halves are then placed together so that the end grooves fit together to form the opening 14 which is then filled with a bonding material such as a brazing alloy comprised of Ag Cu-Pd to hold the two halves together. One edge of the assembly is then lapped to form the bevel. A thin insulated copper wire 1.5 mils in diameter (49 gauge), for example, is wrapped in a "figure 8" configuration through the opening 12 around the groove gila, back through the opening 12, around the groove lib, back through the opening 12, etc, until, for example, a total of four turns is made on each core half. In one embodiment of the above metal magnetic recording and reproduction head, the body thickness bt is between 12 and 15 mils in thickness, and the "track width" tw between 4 and 6 mils in thickness. The gap g is about 40 IL inches. The overall length is between .14 and .18 inches, and the overall height is between .12 and .17 inches. The bevelled portion is cut to precisely define the "track width" (tw); the length s is not critical, but may be, for example, between 25-40% of the total height, or in the above example, between .03 and .07 inches. An embodiment of a metal magnetic recording and reproduction head in accordance with the present invention has now been described in detail along with the method of making the same. This tape head has been found particularly useful in high performance flexible disc video and highdensity digital recording systems such as those described in United States of America patent specification no. 4,079,427. Various modifications may be made to the above-described embodiments such as utilizing materials of different constitution, changing the shape or size of the metal core halves, etc. Since it is obvious that these and many additional changes and modifications can be made in the above-described details without departing from the scope of the invention, it is understood that the invention is not to be limited to said details except as set forth in the appended claims. WHAT WE CLAIM IS:

1. A magnetic recording and/or reproduction head comprising first and second magnetizable metal members bonded together with a gap of predetermined thickness formed between said metal members and extending to a media-engaging end thereof, said metal members being bevelled at said media-engaging end with said one end being of reduced thickness corresponding to the track width of a magnetic-type information storage media as determined by the slope and extent of said bevelled surface.

5. The recording and/or reproduction

-head according to Claim 1 including a layer of non-magnetic material formed within said gap.

6. The recording and/or reproduction head according to Claim 5, wherein said non-magnetic material is comprised of aluminium oxide.

7. The recording and/or reproduction head according to Claim 1 including a brazing alloy bonding said first and second metal members.

8. The recording and/or reproduction head according to Claim 7, wherein said brazing alloy is comprised of silver, copper and palladium.

9. The recording and/or reproduction head according to Claim 1, wherein the thickness of said gap is on the order of 40 CL inches.

10. The recording and/or reproduction head according to Claim 1 including insulated conductive wire coiled around said first and second members for generating and/or receiving electromagnetic energy to respectively write and/or read information from said storage media.

11. The recording and/or reproduction head according to Claim 10, wherein said insulated wire is insulated copper wire on the order of 1.5 mils in diameter.

12. A magnetic recording and/or reproduction head comprising: (a) first and second magnetizable metal members bonded together with a gap of predetermined thickness formed between said metal members to form a block having opposite major planar surfaces disposed in parallel relationship to each other, said block having: (i) a media-engaging end surface contiguous to one of said major planar surfaces and extending substantially perpendicularly with respect thereto, said gap extending to said media-engaging end surface with said media-engaging end surface having a lateral dimension corresponding to the track width of a magnetic information storage medium; (b) a bevelled surface adjoining said media-engaging surface, and having a slope extending outwardly therefrom into merging relationship with the other of said major planar surfaces; and (c) a second end surface connecting said major planar surfaces and disposed substantially perpendicular with respect thereto, said second end surface having a lateral dimension of increased magnitude compared to the lateral dimension of said media-engaging end surface as determined by the slope and extent of said bevelled surface.

13. The recording and/or reproduction head according to Claim 12, wherein said magnetizable metal is an alloy of iron, silicon and aluminium.

14. The recording and/or reproduction head according to Claim 13, wherein said alloy consists of approximately 84.5% iron, 9.5% silicon and 6% aluminium.

15. The recording and/or reproduction head according to Claim 12, wherein the lateral dimension of said second end surface is between 12-25 mils, and wherein the lateral dimension of said media-engaging end surface is between 3-10 mils.

16. The recording and/or reproduction head according to Claim 12 including a layer of non-magnetic material formed within said gap.

17. The recording and/or reproduction head according to Claim 16, wherein said non-magnetic material is comprised of aluminium oxide.

18. The recording and/or reproduction head according to Claim 12 including a brazing alloy bonding said first and second metal members.

19. The recording and/or reproduction head according to Claim 18, wherein said brazing alloy is comprised of silver, copper and palladium.

20. The recording and/or reproduction head according to Cliam 12, wherein the thickness of said gap is on the order of 40 it inches.

21. The recording and/or reproduction head according to Claim 12 including insulated conductive wire coiled around said first and second members for generating and/or receiving electromagnetic energy to respectively write and/or read information from said storage media.

22. The recording and/or reproduction head according to Claim 21, wherein said insulated wire is insulated copper wire on the order of 1.5 mils in diameter.

23. A method of manufacturing a magnetic recording and/or reproduction head comprising: (a) providing first and second magnetizable metal members; (b) bonding said first and second metal members together leaving a gap of predetermined thickness between portions of said metal members extending to a mediaengaging end thereof; and (c) beveling both of said members at said media-engaging end to reduce the thickness of said media-engaging end to the track width of a magnetic information storage medium.

24. The method according to Claim 23, wherein said magnetizable metal is an alloy of iron, silicon and aluminium.

25. The method according to Claim 24, wherein said alloy consists of approximately 84.5% iron, 9.5% silicon and 6% aluminium.

26. The method according to Claim 25, wherein said metal members are between 12-25 mils in thickness, and wherein said members are bevelled such that said media-engaging end is reduced to a thickness of 3-10 mils.

27. The method according to Claim 26 including the steps of forming a spacer layer of non-magnetic material on an end of said metal members adjacent to said mediaengaging end prior to bonding the two metal members together to form said gap.

28. The method according to Claim 27, wherein said non-magnetic material is comprised of aluminium oxide.

29. The method according to Claim 27, wherein said layer of non-magnetic material is formed by evaporation techniques.

30. The method according to Claim 23, wherein the step of bonding said first and second metal members together includes the step of brazing said first and second metal members with a brazing alloy.

31. The method according to Claim 30, wherein said brazing alloy is comprised of silver, copper and palladium.

32. The method according to Claim 27, wherein said layer of non-magnetic material is formed on each of said metal members to a thickness of on the order 20 CL inches to provide a gap width of 40 it inches.

33. Ihe method according to Claim 23 including the steps of providing an opening between said first and second metal members and coiling insulated conductive wire around said first and second members.

34. A magnetic recording and/or reproduction head substantially as described herein with reference to the accompanying drawings.