Method for manufacturing disk drive head suspension structures having improved gold-dielectric joint reliability

0001[Cross-reference of related applications] This application gives priority to US Provisional Patent Application No. 62 / 186,721, which was filed on June 30, 2015 and has the title of the invention "Disc drive head suspension structure with improved reliability of gold dielectric joint". Alleged and incorporated herein by reference in its entirety for all purposes.

0002The present invention generally relates to disc drive head suspensions and flexors. Embodiments of the present invention relate to structures and manufacturing methods having a gold (and other corrosion resistant material) dielectric interface.

0003Integrated lead or wireless disc drive head suspensions and flexors are relatively non-corrosive, such as gold and / or nickel, plated or applied to the surface of relatively more corrosive conductors, such as copper or copper alloys. Generally includes structures with materials. Gold may be plated onto a conductor via an opening in a polyimide or other dielectric layer. In these types of structures, the gold-plated edges can form a junction or interface with the dielectric. Patent Document 1 of Yonekura et al. Discloses, for example, in FIG. 19C, a "backside access" flexure terminal having this type of structure. The terminal surface on the wiring layer is exposed by through holes in the metal layer and the insulating layer, and the terminal surface is gold-plated.

0004Unfortunately, the junction between the gold plating and the dielectric layer in these types of structures is easy to separate. Any voids or gaps formed between the gold plating and the dielectric allow access to the conductor by moisture or other material, making the conductor susceptible to unwanted corrosion. Therefore, there is still a need for an improved structure that improves the reliability of the joint between gold and the dielectric. These types of structures that can be manufactured efficiently are particularly desirable.

<p num="0005"><patcit num="1"><text>U.S. Patent Application Publication No. 2013/0242436</text></patcit></p>

0006Embodiments of the present invention include a dielectric layer, a conductor layer, a seed layer between the dielectric layer and the conductor layer, and a non-corrosive layer on the seed layer side of the conductor layer, such as a terminal pad or a flying trace. Includes a disc drive head suspension or flexure. The seed layer has strips that extend beyond the edges of the dielectric layer. The non-corrosive layer extends over the strips of the seed layer and contacts the edges of the dielectric layer. In another embodiment, the base layer is included on the side of the dielectric layer opposite the seed layer.

0007<figref num="1">FIG. 1 is a detailed view of a flexible portion having a dielectric junction of a non-corrosive material according to an embodiment of the present invention.</figref><figref num="2a">FIG. 2a is a detailed view of the structure in the sequence of process steps during partial manufacturing of the flexure shown in FIG. 1 according to an embodiment of the present invention.</figref><figref num="2b">FIG. 2b is a detailed view of the structure in the sequence of process steps during partial manufacturing of the flexure shown in FIG. 1 according to an embodiment of the present invention.</figref><figref num="2c">FIG. 2c is a detailed view of the structure in the sequence of process steps during partial manufacturing of the flexure shown in FIG. 1 according to an embodiment of the present invention.</figref><figref num="2d">FIG. 2d is a detailed view of the structure in the sequence of process steps during partial manufacturing of the flexure shown in FIG. 1 according to an embodiment of the present invention.</figref><figref num="2e">FIG. 2e is a detailed view of the structure in the sequence of process steps during partial manufacturing of the flexure shown in FIG. 1 according to an embodiment of the present invention.</figref>

0008FIG. 1 is a view of portion 10 of an integrated reed suspension or flexor 8 having a dielectric interface or joint of non-corrosive material according to an embodiment of the present invention. As shown, the portion 10 includes a base layer 12, which can be a spring metal such as stainless steel, and a polyimide or other dielectric layer 14 on the surface of the base layer. The conductor layer 16 is on the side of the dielectric layer 14 opposite to the base layer 12. In embodiments, the conductor layer 16 comprises copper or a copper alloy, which is a metal that is relatively corrosive when exposed to moisture and other substances. In the embodiment, the seed layer 18 containing chromium is arranged between the dielectric layer 14 and the conductor layer 16. In the illustrated embodiment, at least a portion of the dielectric layer 14 and a portion of the base layer 12 form the edge portion 20. The section or strip 22 of the seed layer 18 extends beyond the edge 20 of the dielectric layer 14. The non-corrosive layer 24 is arranged on the surface of the conductor layer 16 facing the seed layer 18. The non-corrosive layer 24 also includes a portion 26 that overlays the strip 22 of the seed layer and contacts the dielectric layer 14 to form a junction or interface with the dielectric layer at the edge portion 20. In embodiments, the non-corrosive layer 24 comprises gold and / or nickel, which are metals that are relatively non-corrosive to the conductor layer 16 when exposed to moisture and other substances.

0009Part 10 can be one of several different structures in Flexia 8. In embodiments, for example, adjacent portions of the non-corrosive layer 24 and the conductor layer 16 are for connecting to a backside access terminal pad (eg, a second stage actuator motor (not shown) on the flexure) of the integrated reed, or At the tail of the flexure, it may be for connection to other connectors (not shown) to disk drive electronics. In these and other embodiments, the adjacent portions of the non-corrosive layer 24 and the conductor layer 16 may also be base layer unsupported leads or flying leads on the flexure 8. These and other embodiments of Flexia 8 may include other structures with portions such as 10 having a non-corrosive material dielectric interface according to embodiments of the present invention.

0010The section or strip 22 of the seed layer 18 provides a surface to which the non-corrosive layer 24 adheres, thereby increasing the strength and integrity of the non-corrosive material dielectric interface. Therefore, the non-corrosive material dielectric interface is difficult to separate and reduces the potential for corrosion of the conductor layer 16 at the interface. In embodiments, the strip 22 can have a depth of about 300 nm (eg, the distance between the edge of the strip and the dielectric layer 14). The depth of strip 22 may be longer or shorter distances in other embodiments. The depth and other dimensions of strip 22 are many, such as the properties and / or dimensions of the dielectric layer 14, the conductor layer 16, the seed layer 18 and / or the non-corrosive layer 24, and / or the properties of the portion 10. It can be determined based on any of the factors (eg, the degree to which part 10 is stressed that can impair the integrity of the interface).

0011An embodiment of a method comprising a series of steps for forming a flexure 8 having a portion 10 is described with respect to FIGS. 2a-2e. FIG. 2a is a diagram of flexure 8'and portion 10'in the intermediate stages of manufacturing, including a structure having an overlay base layer 12, a dielectric layer 14, a seed layer 18 and a conductor layer 16. Wet etching (eg, chemical) and dry etching (eg, plasma) etching, electrolytic and electroless plating, and sputtering processes associated with photolithography (eg, the use of patterned and / or non-patterned photoresist masks). Conventional additive deposition and / or subtractive processes such as, can be used to produce the intermediate structure of the flexure 8 and the flexure 8'. These types of additive and subtractive processes include, for example, "Low Resistance Ground Joints for Dual Stage Actuation Disks". Bennin et al., US Pat. No. 8,885,299, entitled "Drive Suspensions")), Rice et al., US, etc., entitled "Integrated Lead Suspension with Multiple Trace Configurations" US Pat. No. 8,169,746, US Pat. No. 8,144,430, US Pat. No. 8,144,430, such as Hentges, entitled "Multi-Layer Ground Plane Structures for Integrated Lead Suspensions", "Integrated Lead" US Pat. No. 7,929,252, US Pat. No. 7,929,252, such as Hentges, entitled Multi-Layer Ground Plane Structures for Integrated Lead Suspensions, "Method for Making Noble. Metal Conductive Leads for Suspension Assembly) "), Swanson et al., U.S. Pat. No. 7,388,733," Plated Ground Features for Integrated Lead Suspensions, "Peltoma, et al. U.S. Pat. No. 7,384,531 is generally published in U.S. Patent Documents, all of which are incorporated herein by reference for all purposes.

0012As shown in FIG. 2b, a portion of the base layer 12 can be removed from the structure of the flexure 8'at portion 10'(eg, using a patterned photoresist mask and chemical etching). After a portion of the base layer 12 has been removed, a portion of the dielectric layer 14 at portion 10'can be removed (eg, by laser etching via a pattern mask), as shown in FIG. 2c. Unwanted portions of seed 18 can be removed (eg, by chemical etching), as shown in FIG. 2d. The strip 22 can then be formed by removing some of the exposed edges of the dielectric layer 14 above the seed layer 18 (eg, by atmospheric plasma etching), as shown in FIG. 2e. .. Following the formation of the portion 10'with the strip 22, the non-corrosive layer 24 can be applied (ie, plated) to create the structure shown in FIG.

0013These types of manufacturing methods have significant advantages. These types of manufacturing methods allow efficient production of part 10.

0014Although the present invention has been described with respect to preferred embodiments, one of ordinary skill in the art will recognize that modifications of form and detail can be made without departing from the intent and scope of the invention. For example, other methods can be used to produce part 10 of flexha 8.