Flexible printed circuit offset finger stiffener
A hard disk drive flexible printed circuit (FPC) includes a plurality of fingers extending from a main portion, with each finger having a thermally-conductive stiffener, at least one wiring layer over the stiffener, and a cover film over the at least one wiring layer, where the centroid of the stiffener is offset from the centerline of the cover film. Thus, utilizing the heat-sink characteristics of the stiffener, temperature differences among the upper and lower electrical pads of the FPC resulting from a heat-based interconnection procedure can be reduced and the temperatures across the FPC finger made more uniform, damage to the FPC prevented, and soldering yields improved.
1. A flexible printed circuit (FPC) comprising:
a plurality of fingers extending from a main portion, each finger comprising:
a thermally-conductive stiffener having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end,
at least one wiring layer over the stiffener, and
a cover film over the at least one wiring layer and having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end;
wherein the centroid of the stiffener is offset from the centerline of the cover film.
2. The FPC of claim 1 , wherein the centroid of the stiffener is offset from the centerline of the cover film in a direction transverse to the upper and lower sides of the cover film.
3. The FPC of claim 2 , wherein at least one of the top edge and the bottom edge of the stiffener is formed non-parallel with a corresponding at least one of the top edge or the bottom edge of the cover film.
4. The FPC of claim 3 , wherein at least one of the top edge and the bottom edge of the stiffener comprises a material void forming a non-linear shape to the at least one edge.
5. The FPC of claim 1 , wherein at least one of the top edge and the bottom edge of the stiffener is formed non-parallel with a corresponding at least one of the top edge or the bottom edge of the cover film.
6. The FPC of claim 1 , wherein at least one of the top edge and the bottom edge of the stiffener comprises a material void forming a non-linear shape to the at least one edge.
7. The FPC of claim 1 , wherein at least one of the top edge and the bottom edge of the stiffener is formed having a material void in an area closest to the cover film and extending in a direction away from the cover film through only a portion of a thickness of the stiffener.
8. The FPC of claim 1 , wherein the stiffener further comprises a hole to inhibit heat transfer to the stiffener at the location of the hole.
9. A hard disk drive comprising the FPC of claim 1 .
10. A method for manufacturing a flexible printed circuit (FPC) laminate composition having a plurality of fingers, the method comprising:
forming a thermally-conductive stiffener having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end;
forming at least one wiring layer over the stiffener;
forming a cover film over the at least one wiring layer and having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end; and
positioning the centroid of the stiffener offset from the centerline of the cover film.
11. The method of claim 10 , wherein the positioning includes positioning the centroid of the stiffener offset from the centerline of the cover film in a direction transverse to the upper and lower sides of the cover film.
12. The method of claim 11 , wherein forming the stiffener includes forming at least one of the top edge and the bottom edge of the stiffener non-parallel to the other of the top edge and the bottom edge of the stiffener and non-parallel with a corresponding at least one of the top edge or the bottom edge of the cover film.
13. The method of claim 12 , wherein forming the stiffener includes forming at least one of the top edge and the bottom edge of the stiffener with a material void forming a non-linear shape to the at least one edge.
14. The method of claim 10 , wherein forming the stiffener includes forming at least one of the top edge and the bottom edge of the stiffener non-parallel to the other of the top edge and the bottom edge of the stiffener and non-parallel with a corresponding at least one of the top edge or the bottom edge of the cover film.
15. The method of claim 10 , wherein forming the stiffener includes forming at least one of the top edge and the bottom edge of the stiffener with a material void forming a non-linear shape to the at least one edge.
16. The method of claim 10 , wherein forming the stiffener includes forming at least one of the top edge and the bottom edge of the stiffener having a material void in an area closest to the cover film and extending in a direction away from the cover film through only a portion of a thickness of the stiffener.
17. The method of claim 10 , wherein forming the stiffener includes forming the stiffener further comprising a hole to inhibit heat conductivity to the stiffener at the location of the hole.
18. A hard disk drive (HDD) comprising:
a plurality of recording media rotatably mounted on a spindle;
a plurality of head sliders each housing a respective read-write transducer configured to read from and to write to at least one recording media of the plurality of recording media;
an actuator configured to move the plurality of head sliders to access portions of the at least one recording media;
means for transmitting electrical signals to and from a respective head slider of the plurality of head sliders; and
a flexible printed circuit (FPC) electrically connected to the means for transmitting electrical signals, the FPC comprising:
a plurality of fingers extending from a main portion, each finger comprising:
a thermally-conductive stiffener having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end,
at least one wiring layer over the stiffener, and
a cover film over the at least one wiring layer and having an upper side having a top edge, a lower side having a bottom edge, a proximal end, and a distal end that is narrower than the proximal end,
wherein the centroid of the stiffener is offset from the centerline of the cover film in a direction transverse to the upper and lower sides of the cover film.
19. The HDD of claim 18 , wherein at least one of the top edge and the bottom edge of the stiffener is formed non-parallel with a corresponding at least one of the top edge or the bottom edge of the cover film.
20. The HDD of claim 18 , wherein at least one of the top edge and the bottom edge of the stiffener is formed having a material void in an area closest to the cover film and extending in a direction away from the cover film through at least a portion of a thickness of the stiffener.