Electrical interconnect scheme

A connector that can couple a flexible circuit board of a head gimbal assembly to driving circuits of an apparatus coupled to a hard disk. The connector includes a pair of spring biased plates that push the flexible circuit into contact with a printed circuit board. The circuit board is coupled to the driving circuits. The pressure plates can be manually pushed into an open position to allow an operator to insert or remove the flexible circuit board from the connector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter disclosed generally relates to the field of servo writers and disk certifiers for the disks of hard disk drives.

2. Background Information

Hard disk drives contain a plurality of heads that are magnetically coupled to one or more disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disks. The information is typically stored within annular tracks that extend radially across the disks.

The heads are typically mounted to flexure arms that are attached to an actuator arm. The actuator arm includes a voice coil that can move the heads across the disks to access the annular tracks. It is desirable to position the heads at the center of the annular tracks. Deviations from the track centerlines may cause errors in reading and writing data. The heads are centered with a servo routine that utilizes servo bits embedded into the annular tracks.

The servo bits are typically written at the manufacturing facility of a disk drive manufacturer by a system commonly referred to as a servo writer. The servo writer contains electrical circuits that are coupled to the heads of a disk drive. The servo writer causes the heads to write servo bits onto the disks in accordance with a servo writing routine.

Historically, the process of “servowriting” has been performed at the HDA (head-disk-assembly) level of the Hard Disk Drive. Because earlier drives utilized multiple disks and heads, and with fewer servo tracks to write, (due to lower disk data density), servo write time was accomplished in a few minutes. However, the number of servo tracks has continued to increase along with disk data density, and the time required to write and verify all the servo tracks has increased dramatically. Also, because of the data density increases, many hard disk drives today only have a single disk, whereas previously, multiple disks were required. Therefore, for economy of manufacturing, servowriting of multiple disks prior to assembly into the HDA is fast becoming desirable. One manifestation of writing at the disk level, however, is that the same bank of heads is used to write many disks, rather than at the HDA level, where the drive's own heads were used only once to write the servo tracks. Due to wear and tear, the servo-writer heads must be changed periodically.

The heads of a disk drive were historically coupled to a pre-amplifier circuit by soldering two or more twisted wires directly to the flexcircuit. To improve manufacturing efficiencies and high frequency electrical performance, some disk drives utilize flexible circuit boards to couple the heads to the pre-amplifier. A flexible circuit board includes metal traces that are located between a pair of flexible dielectric strips. The traces terminate at contact pads located at the end of the flex circuit. In a hard disk drive, termination to drive electronics is typically done via ultrasonic or laser bonding.

Soldering, ultrasonic or laser bonding of head terminations, however, is simply not acceptable for use at the multiple disk servowriter level due to logistical, cost, and contamination issues. Therefore, in a multiple disk servowriter, it is desirable to couple the heads to servo writer circuits via some sort of electrical connector. Due to severe space limitation, as well as the high number of electrical connections, typically 4 or 5 per head, most commercially available connectors are not applicable. Some prior applications have used spring-biased “pogo” pins for termination to the head flex circuit pads.

However, pogo pins are susceptible to bending and must sometimes be replaced. Additionally, pogo-pin connectors are bulky and difficult to solder onto a corresponding printed circuit board.

BRIEF SUMMARY OF THE INVENTION

A connector for an apparatus coupled to a hard disk. The connector includes a spring coupled to a pair of pressure plates. The connector further includes a printed circuit board located between the pressure plates.

DETAILED DESCRIPTION

Disclosed is a connector that can couple a flexible circuit board of a head gimbal assembly to driving circuits of an apparatus coupled to a hard disk. The connector includes a pair of spring biased plates that push the flexible circuit into contact with a printed circuit board. The circuit board is coupled to the driving circuits. The pressure plates can be manually pushed into an open position to allow an operator to insert or remove the flexible circuit board from the connector. The apparatus described herein is for a very compact, rugged, easily modifiable, and scalable electrical interconnect scheme which allows quick head changes with no secondary termination process, such as solder, ultrasonic bonding, etc.

The printed circuit board has gold plated pads on each side which match the pad locations on the head termination flexcircuits. One PCB can terminate two heads, one on each side. Typically, 4 pads per side are provided for use with modern MR or GMR type read write heads. The PCB also has one or more locating pins, to provide accurate registration of the head flexcircuit on each side of the PCB. Each pressure plate has small protrusions to provide point contact pressure over the center of each termination pad. Therefore, when the head flexcircuit(s) are positioned onto the PCB and the springloaded pressure plates installed over the flexcircuits, the pads on the head flexcircuit are forced against the gold plated pads on PCB at the protrusion points on the pressure plates. Additionally, the pressure plates are designed with an integral spring “finger”, to allow for normal manufacturing thickness variations.

Referring to the drawings more particularly by reference numbers,FIG. 1shows a servo writer10used to write servo bits onto disks12(only one disk is shown), which will subsequently be installed into a hard disk drive (not shown) after completion of the servowriting process. The disks12are magnetically coupled to a plurality of heads16. Each head16is mounted to a flexure arm18that is attached to an actuator structure which is typically called an “E-block” assembly28. The actuator accurately positions heads16on disks12. Each head16is also connected to a flexible circuit board22, which provides electrical terminations to the read and write elements of each head16. When the servowriter is fully assembled, the flexible circuit boards22are attached to a pre-amplifier flex circuit24, which typically contains servo writer circuits26of the actuator.

The servo writing circuits26may include a R/W preamplifier, microprocessor, memory, digital to analog converters, amplifiers, etc. (not shown) that cause the heads16to magnetize and write servo bits onto the disks12.

The E-block assembly28includes a flexible printed circuit board24that contains routing traces, pads, etc. that can provide an electrical path from the servo circuits26to the heads16. The routing traces, pads, etc. are typically attached to a dielectric substrate as is known in the art. The E-block assembly28further has a plurality of connector assemblies30that couple the flexible circuit boards22to the flexible printed circuit board24.

As shown inFIG. 2, each connector assembly30includes a printed circuit board32that is soldered to the circuit board24of the E-block assembly28. Each printed circuit board32may includes a plurality of contact pads34that are electrically connected to corresponding pads36of the circuit board24. The contact pads34may be configured to match corresponding pads (not shown) of the flexible circuit boards22. One or more of the circuit boards32may have contact pads34located on both sides of the board32so that a single connector assembly30can couple two flexible circuit boards22to the servo writer circuits26. Each circuit board32may also have one or two alignment pins38.

Referring toFIG. 1, each connector30may include a clamp40that presses a flexible circuit board22into the printed circuit board32so that the contact pads of the flex circuit22electrically connect to the contact pads of the circuit board32. It should be noted that the flex circuits22are typically insulated on the side opposite the contact pads. Therefore the clamps40do not necessarily have to have electrical insulation qualities.

As shown inFIGS. 3 and 4, each clamp40includes a first pressure plate42and a second pressure plate44. The pressure plates42and44pivot about corresponding mounts46of the plates42and44. The pressure plates42and44are coupled together by a metal wire48that is attached to the mounts46, such that a hinge-like action is obtained.

Each clamp40includes a plurality of springs50that bias the plates42and44into a closed position. The pressure plates42and44can be rotated by pressing the plates42and44at or near the notches52. When released the springs50move the plates42and44back to the closed position. The pressure plates42and44may be constructed from a relatively inexpensive molded plastic material, which also has the advantage of being an electrical insulator.

Each pressure plate42and44may have a plurality of fingers54. The outer fingers54include alignment holes56that are configured to receive the alignment pins38of the printed circuit board32shown in FIG.2. Balls58may be pressed into corresponding depressions60in the middle fingers54of the plates42and44. The balls58focus the spring forces exerted by the plates42and44onto the contact pads of the flex circuit22and circuit board32. Use of hard metal balls provides superior wear resistance. However it may also be possible to mold the ball shape into the pressure plates42and44. The fingers54provide flexibility in the plates42and44to compensate for variations in the thickness of both the flex circuit22and the circuit board32.

In operation, the clamp40of each connector30is pushed to move the pressure plates42and44into an open position. One or more flexible circuit boards22are then placed onto the circuit board32so that the contact pads of the boards22and32are aligned. The pressure plates42and44are then released so that the springs50apply a spring force through the plates42and44, and balls56onto the flex circuit22. The spring force presses together the corresponding contact pads of the flex circuit22and the circuit board32. The process is repeated for each connector30and corresponding flex circuit(s)22.

After all of the flexible circuit boards22are attached to the connectors30the servo writer circuits26cause the heads16to write servo bits onto the disks12. When the servowriting process is completed, the heads16are withdrawn from the disks12, new disks are installed and the process is repeated. When the heads wear out, or are damaged, one or more clamps40are opened and the flexible circuit boards22are removed from the connectors30, which then allows the head assemblies18to be removed.

Although a servo writer has been shown and described, it is to be understood that the connector assembly may be used in other apparatuses such as a disk certifier, or a system that contains both a servo writer and a disk certifier. A disk certifier typically detects magnetic and/or surface defects in the surfaces of a hard disk. It may be desirable to test multiple hard disks. The stylus/heads used in some disk certifiers wear out and must be replaced. The connector assembly of the present invention allows for rapid replacement of the worn out heads.