Disk drive load arm structure having a strain sensor and method of its fabrication

1. A load arm for a disk drive comprising:

a base section having hinge arms terminating in tabs;

an arm section affixed to the tabs of the hinge arms of the base section;

a head suspension assembly affixed to a distal end of the arm section; and

a sensor formed on a selected hinge arm of the base section adapted to provide a strain measurement signal responsive to mechanical deflection of the selected hinge arm, the base section and the selected hinge arm being electrically conductive to form a first signal path for the sensor, the sensor being formed of a continuously extending first layer of piezoelectric polymer sensing material which extends along the base section, and an electrode being formed as a continuously extending second layer of conductive material that contactingly extends along the first layer to provide a second signal path for the sensor.

2. The load arm claimed in claim 1 , wherein the hinge arms comprise first and second arms which extend in spaced apart relation from the base section, the sensor is characterized as a first sensor attached to the first arm, and the load arm further comprises a second sensor nominally identical to the first sensor and attached to the second arm.

3. The load arm claimed in claim 1 , wherein the sensor is formed from a single piezoelectric polymer sensing layer which extends in contacting abutment against a selected surface of the selected hinge arm along an entire length of the sensor.

4. The load arm claimed in claim 1 , wherein the hinge arms provide a point of relatively high strain in relation to remaining portions of the load arm so that the sensor detects resonant modes of the load beam responsive to said deflection.

5. The load arm claimed in claim 1 , wherein the base section comprises a base plate portion that extends along a first plane, the hinge arms extend from the base plate portion at a second plane non-normal to the first plane, and the base plate portion comprises an opening for receiving a spindle of a voice coil motor.

6. A method of forming a load arm for a disk drive comprising;

providing a substrate comprising a sheet of a structural material and a piezoelectric polymer film formed on a surface of the structural material;

forming sensors on the structural material, the sensors comprising electrodes overlying portions of the piezoelectric polymer film;

masking said sensors and portions of the substrate with a mask defining a base section of a load arm, the mask defining hinge arms of the base section beneath said sensors, the base section being electrically conductive to form a first signal path for the sensor, the electrode providing a second signal path that continuously extends along the piezoelectric polymer film;

etching the structural material to form a base section corresponding in shape to the mask;

removing the mask from the base section;

affixing an arm section to the base section at tabs extending from the hinge arms of the base section; and

affixing a head suspension assembly to a distal end of the arm section.

7. The method claimed in claim 6 , wherein providing a substrate comprises laminating a polyvinylidene fluoride (PVDF) film to a sheet of steel.

8. The method claimed in claim 7 , wherein forming sensors comprises:

forming electrodes on the PVDF film; and

etching to remove portions of the PVDF film using the electrodes as etch masks.

9. The method claimed in claim 8 , wherein the electrodes are formed by printing a conductive ink on the PVDF film.

10. The method claimed in claim 7 , wherein forming sensors comprises:

forming electrodes on the PVDF film;

forming a mask over the PBDF film and the electrodes, the mask defining shapes of the sensors; and

etching to remove portions of the PVDF film unprotected by the mask.

11. The method claimed in claim 10 , wherein the mask defining a base section is formed over the mask defining shapes of the sensors after etching to remove portions of the PVDF film.

12. The method claimed in claim 10 , wherein the mask defining shapes of the sensors is removed after etching to remove portions of the PBDF film and before forming the mask defining a base section.

13. The method claimed in claim 7 , wherein forming sensors comprises forming conductive structures on the PVDF film, the conductive structures comprising sensor electrodes, conductive pads, and conductive traces connecting the sensor electrodes to the conductive pads.

14. The method claimed in claim 13 , wherein the sensor electrodes, conductive pads, and conductive traces are formed by printing a conductive ink on the PVDF film.

15. The method claimed in claim 6 , wherein affixing the arm section is preceded by bending the hinge arms.

16. The method claimed in claim 6 , wherein affixing the arm section is followed by bending the hinge arms.

17. The method claimed in claim 6 , wherein the arm section comprises spot welding an end of the arm section to the tabs of the hinge arms of the base section.

18. An apparatus comprising:

a base section comprising a base plate portion extending along a first plane and spaced apart first and second hinge arms which linearly extend from the base plate portion along a second plane non-normal to the first plane;

an arm section connected to the first and second hinge arms and extending along said second plane; and

a continuous layer of piezoelectric material which contactingly extends along the base plate portion and a selected one of the first or second hinge arms, a distal end of said layer of piezoelectric material adapted to generate a strain measurement signal responsive to mechanical deflection of the selected hinge arm, the base section and the selected hinge arm being electrically conductive to form a first signal path for the sensor, the sensor being formed of a continuously extending first layer of piezoelectric polymer sensing material which extends along the base section, and an electrode being formed as a continuously extending second layer of conductive material that contactingly extends along the first layer to provide a second signal path for the sensor.

19. The apparatus of claim 18 , further comprising a continuous layer of conductive material which contactingly extends along the layer of piezoelectric material to conduct said strain measurement signal.