1. Field of the Invention
The present invention relates to a head suspension, a method of manufacturing a base plate of the head suspension, and a method of manufacturing the head suspension, the head suspension being a device to support a read/write head to write and read data to and from a magnetic disk or a hard disk in a disk drive of for example, a personal computer.
2. Description of Related Art
A base plate for a head suspension is manufactured as illustrated in FIG. 12, for example. FIG. 12 illustrates a method of manufacturing a head suspension according to a related art (Japanese Unexamined Patent Application Publication No. 2012-14812). In FIG. 12, a base plate chain 101 is processed into a head suspension chain 103, and from the head suspension chain 103, individual head suspensions 105 are cut off.
The base plate chain 101 includes base plates 107 each of which is fabricated into the head suspension 105. The head suspension 105 is of a dual actuator system that uses, in addition to a voice coil motor to turn the head suspension 105 as a whole in a sway direction or a width direction, a piezoelectric element to minutely turn a head of the head suspension 105 in the sway direction. The base plate 107 includes a boss 111 and an actuator base 113. In the base plate chain 101, a plurality of the base plates 107 are joined to a frame 112.
The actuator base 113 has a rear end 115 and a front end 117. The rear and front ends 115 and 117 are spaced from each other in a direction of a rotation radius of the head suspension 105 and are connected to each other through a link 119 that is present at a widthwise center of the base plate 107. On each side of the link 119, there are a pair of actuator attaching areas 121a and 121b that are openings in each of which the piezoelectric element is attached.
In this specification, a “longitudinal direction” corresponds to the direction of the turning radius of the head suspension and a “width direction” to a direction orthogonal to the longitudinal direction.
Along each side of the rear end 115, there are side segments 123b and 125b, and along each side of the front end 117, there are side segments 123a and 125a. The side segments 123a (125a) and 123b (125b) extend in the longitudinal direction, are spaced from each other, and face each other, so that the front end 117 is movable relative to the rear end 115.
The base plate chain 101 is deburred by, for example, chemical polishing, electrolytic polishing, or barrel polishing, and load beams 125 are connected to the respective base plates 107 in the base plate chain 101. Thereafter, piezoelectric elements 127a and 127b each made of, for example, PZT (lead zirconate titanate) are attached in the respective actuator attaching areas 121a and 121b of each base plate 107 with a nonconductive adhesive. Thereafter, a flexure having a head and wiring is attached to each head suspension 105, thereby forming the head suspension chain 103. The head suspension chain 103 is cut into individual head suspensions 105.
In the base plate chain 101 to be subjected to the above-mentioned processes, each base plate 107 has the actuator attaching areas 121a and 121b and separated side segments 123a, 123b, 125a, and 125b. These parts may entangle among a plurality of base plate chains 101 during the transportation of the base plate chains 101 between processes and may be deformed by receiving external force. The deformation causes material and product losses and increase costs. To avoid the entanglement and deformation, the base plate chains 101 may be aligned before deburring or heat treatment. This, however, deteriorates productivity.
If the base plates 107 are thinner to reduce their weight, the above-mentioned problem will become more serious.
FIG. 13A is a plan view illustrating a base plate 107A with outer frames according to the related art and FIG. 13B is a plan view illustrating a base plate 107B without outer frames according to the related art. These base plates 107A and 107B are individually manufactured. Namely, they are not chained.
In FIG. 13A, the base plate 107A has a single actuator attaching area 121 being an opening and outer frames 129a and 129b that outwardly protrude with respect to the actuator attaching area 121 in the width direction. The actuator attaching area 121 receives a single piezoelectric element.
In FIG. 13B, the base plate 107B is similar to the base plate 107 of FIG. 12, and therefore, is illustrated with the same reference numerals as those of FIG. 12.
When a plurality of the base plates 107A (107B) are simultaneously processed through deburring, heat treatment, and head suspension assembling, the actuator attaching areas 121 (121a, 121b) may entangle among the base plates 107A (107B), to deform front ends 117A (117) and the like.
The barrel polishing, in particular, is speedier for the deburring of the base plates 107A (107B). It, however, frequently causes the entanglement and deformation of the base plates 107A (107).
Compared with the base plate 107A of FIG. 13A, the base plate 107B of FIG. 13B has no outer frames, and therefore, has low rigidity and easily entangles with others to increase material and product losses and decrease productivity.
To solve the problem, the base plate 107B without frames may be provided with a scrap section in a half-finished stage.
FIG. 14 is a view illustrating Step S101 to form a half-finished base plate 107BA and Step S102 to form the base plate 107B.
Step S101 of FIG. 14 forms the half-finished base plate 107BA by pressing a stainless steel thin plate of 100 to 250 micrometers thick. The half-finished base plate 107BA has scrap sections 131a and 131b which are black-colored in FIG. 14 for the sake of explanation. In practice, the scrap sections 131a and 131b are made of the same material as the half-finished base plate 107BA and are integral therewith with no boundaries.
A plurality of the half-finished base plates 107BA are collectively deburred by, for example, barrel polishing, are heat-treated, and are subjected to Step S102. The deburring and heat treatment are carried out to the half-finished base plates 107BA each having the scrap sections 131a and 131b that increase the rigidity of the actuator attaching areas 121a and 121b. Even if many half-finished base plates 107BA are simultaneously processed by, for example, barrel polishing, the actuator attaching areas 121a and 121b of each half-finished base plate 107BA will not entangle with others.
Step S102 of FIG. 14 cuts off the scrap sections 131a and 131b by pressing from the half-finished base plate 107BA, to form the base plate 107B that integrally has the actuator attaching areas 121a and 121b and the boss 111.
The related art of FIG. 14 is capable of suppressing the deformation of the half-finished base plate 107BA during the deburring, heat treatment and the like and realizing easy handling of the half-finished base plate 107BA for the deburring, heat treatment and the like.
The related art, however, has a problem that Step S102 carried out after the deburring process of Step S101 leaves burrs or cut burrs on cutting surfaces at which the scrap sections 131a and 131b are cut off from the half-finished base plate 107BA. These cut burrs may drop off in a completed hard disk drive into which a head suspension having the base plate 107B is installed.
If many half-finished base plates 107BA are processed with a metal mold for cutting off the scrap sections 131a and 131b, blades of the metal mold will become dull to enlarge the cut burrs. The large cut burrs are likely to drop off in hard disk drives.
To minimize the cut burrs, the blades of the metal mold must frequently be maintained. This, however, deteriorates productivity due to intermittence of the manufacturing process.