BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects and features of the invention would be apparent from the detailed description, which is made with reference to the following drawings. It should be appreciated that the detailed description and the drawings provide various non-limiting examples of various embodiments of the invention, which is defined by the appended claims.
FIG. 1 is reproduction of FIG. 1 of U.S. Pat. No. 6,784,536.
FIG. 2 illustrates the same arrangement as disclosed in the '536 patent, except that the solder bumps 70 are shown soldered to PCB 200, which was omitted in the '536 patent.
FIGS. 3
a and 3b depict a hard drive suitable for implementing embodiments of the subject invention.
FIG. 4 depicts an arrangement of carrier plate, substrate, and wire-bond preamp according to an embodiment of the invention.
FIG. 5 is a cross section depicting an embodiment of the invention.
FIG. 6 depicts another embodiment of the invention.
FIG. 7 a sheet of substrates according to an embodiment of the invention.
DETAILED DESCRIPTION
FIGS. 3
a and 3b depict a hard drive suitable for implementing embodiments of the subject invention. FIG. 3a depicts the hard drive 300 with the cover removed, while FIG. 3b depicts an enlarged image of the preamp area of the hard drive. The hard drive 300 uses rotating platters (disks) 310 to store data. Each platter is rotated by a spindle (not shown) and has a smooth magnetic surface on which digital data is stored. Information is written to the disk by applying a magnetic field from a read-write head (not shown) that is attached to an actuator arm 320. For reading, the read-write head detects the magnetic flux emanating from the magnetic bits that were written onto the platter. Since the signals from the read/write head is very faint, a preamp 330 is provided in close proximity to the head. The preamp 330 is a chip that is mounted on a substrate 340. The substrate 340 is mounted onto a carrier plate 350, that connects to the actuator arm assembly 320. The flexible circuit loop 360 is connected to the substrate 340, to transfer signals between the preamp 330 and the associated electronics (not shown). The associated electronics control the movement of the actuator and the rotation of the disk, and perform reads and writes on demand from the disk controller.
FIG. 4 depicts an arrangement of carrier plate, substrate, and wire-bond preamp according to an embodiment of the invention. In FIG. 4, the substrate 440 is mounted onto carrier plate 450. As shown in the cross-section inside the broken-line callout, the substrate is generally made of a stainless steel or aluminum backing, generally referred to as a stiffener, 415, an insulating layer, e.g., polyimide, 425, and copper conducting contacts and lines 435. The preamp 430 is attached to the stiffener 415 of the substrate 440 via cutout or window 405 in the insulating layer 440. The contact pads 445 of the preamp chip 430 are connected to the copper contacts 435 via conductive wires 455. An insulative epoxy may be provided on top of preamp 430, wires 455 and contacts 435, but is not shown herein for clarity. In the case depicted, substrate 440, having its own stiffener 415, folds back over carrier plate 450. Carrier plate 450 and stiffener 415 can be made from a common metal layer. Alternate designs integrate the function of the carrier plate 450 into the stiffener 415, eliminating the need for the carrier plate 450.
FIG. 5 is a cross section depicting an embodiment of the invention. In FIG. 5, the carrier plate 550 is bolted onto protrusion 522 (shown as 322 in FIG. 3b) of actuator arm assembly 320, thereby making a heat conductive path. While in this embodiment a bolt 524 is used as the fastening means, other methods may be used, but heat conductive methods would provide improved results. Also, the carrier plate 550 is connected to other sections of the actuator arm assembly, but it is not shown in FIG. 5. The stiffener 515 is bonded to the carrier plate 550 using heat conductive adhesive 575. One type of adhesive that is suitable for use with the embodiments described herein is TIGA HTR-815 epoxy, available from Resin Technology Group of South Easton, Mass. This epoxy has thermal conductivity of 1.15 W/m-K. This enables good thermal conductivity between the stiffener 515 and the carrier plate 550. The preamp chip 530 is also bonded to the stiffener 515 in a window 505 formed in the insulating layer 540. Again, a thermally conductive adhesive should be used. In this manner, good thermal conductivity is provided from the preamp chip 530, via the stiffener 515, the carrier arm 550, to the actuator arm assembly 320, forming a relatively large heat sink for the preamp chip 530.
The preamp 530 receives and sends signals via the wires 555 that are connected to contact pads 535 provided on the insulating layer 540. The contact pads 535 are connected to wiring circuitry that is also formed on the insulating layer 540, and provides contact to flexible circuit loop 560. The flexible circuit loop 560 is connected at its other end (see FIG. 3a) to a connector provided on metal bracket 362 (the complete arrangement can be seen in the '362 patent). In this manner, the chip 530 is mounted onto the stiffener 515 which is bonded to the carrier plate 550, which in turns is mounted onto the actuator arm assembly 520, to provide improved heat removal. The PCB is mounted remotely from the preamp 530 and is connected to the preamp 530 via the flexible circuit loop 560. In this embodiment, insulating adhesive 585 is provided over the preamp 530 and wires 555 for protection.
FIG. 6 depicts another embodiment of the invention. The embodiment of FIG. 6 is very similar to that of FIG. 5, except that in the embodiment of FIG. 6 a conductive layer 533, such as a conductive paint, is provided over the insulating adhesive 685. This conductive layer assists in preventing electromagnetic interference (EMI) with the preamp. To improve this protection, contact pads 637 are provided over the insulative layer 640 so as to contact the conductive layer 633. The contact pads 637 are grounded so as to also ground the conductive layer 633. In this embodiment, it would be advantageous to use a heat conductive adhesive for insulation adhesive 685. This embodiment is especially beneficial for high frequency integrated circuit applications, as such application generate a relatively large amount of heat and may require enhanced EMI protection.
FIG. 7 depicts a sheet of substrates according to an embodiment of the invention. The substrates are generally made using a sheet of stiffener material 715, upon which an insulation layer and conductive circuit layer are formed. As depicted in FIG. 7, a sheet of stiffener material, such as stainless steel or aluminum, 715, serves as a starting material for fabricating the substrates 745. For each substrate 745, an insulation layer, such as a polyimide layer, 725 is deposited on top of the stiffener 715 to serve as an electrical insulator. The insulation layer 725 is deposited according to a predetermined design, so that it does not cover the entire surface of the stiffener layer 715. Notably, a window 727 is provided at the location where the preamp chip would be bonded to the stiffener 715. On top of the insulation layer 725, various conductive elements 735 are deposited to form conductive circuitry of contacts and transmission lines. The fabrication of these layers is done using conventional photolithography techniques. Both subtractive and additive flexible circuit fabrication processes are commonly employed in hard disk drives manufacturing. To maximize the available real estate, the substrates 745 are fabricated so as to “nest” with each other, and after the fabrication is completed the substrates 745 are cut out of the stiffener sheet 715.
Thus, while only certain embodiments of the invention have been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention. Further, certain terms have been used interchangeably merely to enhance the readability of the specification and claims. It should be noted that this is not intended to lessen the generality of the terms used and they should not be construed to restrict the scope of the claims to the embodiments described therein.
Patent Application
20080088978
