Pre-solder bump preventive overcoating
A hard disk drive flexure assembly includes an insulative base layer over a metal substrate, a first conductive layer over the base layer, a plurality of electrical pads each comprising a second conductive layer over the first conductive layer, a pre-formed bump of solder material positioned over each pad, and a conductive cover layer over at least a portion of each pre-solder bump. With the conductive cover layer, e.g., gold, solder material from each pre-solder bump is inhibited from transferring to a probe during electrical check of the flexure, the solder material is inhibited from oxidizing, and solder splash is inhibited. These techniques are especially relevant with narrow, high-density, small pitch electrical pads.
1. A flexure for a suspension assembly for a hard disk drive (HDD), the flexure comprising:
a metal substrate;
an insulative base layer over at least a portion of the substrate;
a first conductive layer over at least a portion of the base layer;
a plurality of electrical pads, each electrical pad comprising a second conductive layer over the first conductive layer and configured for electrical connectivity with a corresponding electrical pad of a head slider;
a pre-formed bump of solder material pre-positioned over at least a portion of each electrical pad of the plurality of electrical pads of the flexure; and
a conductive cover layer over and in contact with the entire exposed portion of each pre-formed bump of solder material.
2. The flexure of claim 1 , wherein each conductive cover layer comprises gold.
3. The flexure of claim 1 , wherein each conductive cover layer is positioned over and in contact with at least a portion of each electrical pad, of the plurality of electrical pads of the flexure, not covered by the pre-formed bump of solder material.
4. The flexure of claim 1 , wherein the second conductive layer of each electrical pad of the plurality of electrical pads of the flexure comprises nickel.
5. The flexure of claim 1 , wherein:
the second conductive layer of each electrical pad of the plurality of electrical pads of the flexure comprises nickel; and
each conductive cover layer is positioned over and in contact with only a portion of each second conductive layer.
6. The flexure of claim 1 , further comprising:
a third conductive layer between the second conductive layer and the pre-formed bump of solder material.
7. The flexure of claim 6 , wherein the third conductive layer comprises gold.
8. The flexure of claim 7 , wherein each conductive cover layer is positioned over and in contact with at least a portion of each third conductive layer not covered by the pre-formed bump of solder material.
9. A method for manufacturing a flexure assembly for a hard disk drive, the method comprising:
forming an insulative base layer over at least a portion of a metal substrate;
forming a first conductive layer over at least a portion of the base layer;
forming a plurality of electrical pads, each electrical pad comprising a second conductive layer over the first conductive layer and configured for electrical connectivity with a corresponding electrical pad of a head slider;
forming a pre-formed bump of solder material pre-positioned over at least a portion of and in contact with each of the electrical pads of the plurality of electrical pads of the flexure assembly; and
forming a conductive cover layer over the entire exposed portion of each pre-formed bump of solder material.
10. The method of claim 9 , further comprising:
prior to forming the second conductive layer, applying a first mask over the first conductive layer for forming each second conductive layer;
prior to forming the pre-formed bump of solder material, removing the first mask and applying a second mask over the second conductive layer for forming each pre-formed bump of solder material; and
prior to forming the conductive cover layer, applying a third mask for forming each conductive cover layer;
wherein the first mask and the third mask have the same pattern.
11. The method of claim 9 , further comprising:
prior to forming the second conductive layer, applying a first mask over the first conductive layer for forming each second conductive layer;
forming a third conductive layer between the second conductive layer and the pre-formed bump of solder material; and
prior to forming the pre-formed bump of solder material, removing the first mask and applying a second mask over the third conductive layer for forming each pre-formed bump of solder material.
12. The method of claim 9 , further comprising:
prior to forming the second conductive layer, applying a first mask over the first conductive layer for forming each second conductive layer;
forming a third conductive layer between the second conductive layer and the pre-formed bump of solder material;
prior to forming the pre-formed bump of solder material, removing the first mask and applying a second mask for forming each pre-formed bump of solder material; and
prior to forming the conductive cover layer, applying a third mask for forming each conductive cover layer;
wherein the first mask and the third mask have the same pattern.
13. The method of claim 9 , further comprising:
prior to forming the second conductive layer, applying a first mask over the first conductive layer for forming each second conductive layer comprising nickel;
prior to forming the pre-formed bump of solder material, removing the first mask and applying a second mask over the second conductive layer for forming each pre-formed bump of solder material; and
prior to forming the conductive cover layer, applying a third mask over the second conductive layer for forming each conductive cover layer;
wherein the third mask is patterned such that each conductive cover layer is positioned over only a portion of each second conductive layer.
14. The method of claim 9 , further comprising:
electrically connecting the plurality of electrical pads of the flexure assembly to the corresponding electrical pads of the head slider employing laser irradiation of each pre-formed bump of solder material.
15. A hard disk drive (HDD) comprising:
a disk medium rotatably mounted on a spindle;
a suspension assembly comprising a flexure comprising:
a metal substrate,
an insulative base layer over at least a portion of the substrate,
a copper layer over at least a portion of the base layer,
a plurality of electrical pads, each electrical pad comprising a nickel layer over the copper layer,
a pre-formed bump of solder material pre-positioned over at least a portion of each electrical pad of the plurality of electrical pads, and
a gold cover layer over and in contact with the entire exposed portion of each pre-formed bump of solder material;
a head slider housing a read-write transducer configured to read from and to write to the disk medium, the head slider mounted on the suspension assembly and electrically connected to the plurality of electrical pads of the flexure via the pre-formed bump of solder material; and
means for moving the head slider to access portions of the disk medium.
16. The HDD of claim 15 , wherein each gold cover layer is positioned over and in contact with at least a portion of each electrical pad, of the plurality of electrical pads, not covered by the pre-formed bump of solder material.
17. The HDD of claim 15 , wherein each gold cover layer is positioned over and in contact with only a portion of each nickel layer.
18. The HDD of claim 15 , wherein the flexure further comprises a second gold layer between the nickel layer and the pre-formed bump of solder material.
19. The HDD of claim 18 , wherein each gold cover layer is positioned over and in contact with at least a portion of each second gold layer not covered by the pre-formed bump of solder material.