Inverted pocket welding for disk drive head suspensions

[0001] The invention generally relates to head suspensions for disk drives. In particular, the invention includes methods for welding together two or more components of a head suspension.

[0002] Head suspensions, as used to suspend magnetic read/write heads over rotating disks in disk drive units, are well known and in widespread use. A head suspension is typically constructed from multiple components of varying thicknesses such as a load beam, a spring/hinge, a flexure, a base plate, and an actuator arm. The head suspension is manufactured by welding together two or more of these components by a series of spot welds. Lasers are often used to form the welds. Methods for welding together components of a head suspension are disclosed, for example, in U.S. Pat. No. 6,417,995 to Wu et al. and U.S. Pat. No. 6,900,966 to Xu.

[0003] Variations in thicknesses between components can present complications because the amount and/or duration of energy required for melting an area on a relatively thick component will be more than that required for melting an equivalent area on a relatively thin component. As such, welding thin component(s) to relatively thick component(s) requires increased laser energy per pulse delivered to the work piece for ensuring a proper weld. In general, the greater the amount of energy needed to form the weld, the greater the likelihood of detrimental consequences such as heat-induced deformation in the relatively thinner components, edge warping, dielectric and/or coverlay burning, increased levels of soot and splatter requiring more frequent cleaning of the welding system, increased molten weld pool resulting in larger weld diameter and material flow, and weld inconsistencies. Larger weld diameters reduce the real estate available for clamping and routing traces, and decrease product and flexure design flexibility

[0004] There remains, therefore, a continuing need for methods utilizing less welding energy for welding together head suspension components. A method capable of producing weld spots of smaller size, especially in applications involving the welding of a relatively thin component to a relatively thick component, would be advantageous.

[0005] The present invention is a method for welding together two or more components of a head suspension for disk drives. The method can produce a relatively small diameter weld and improved penetration of the weld nugget.

[0006] In one embodiment of the present invention, the method includes the step of providing at least two metal components, each having opposite sides. The first component has a weld pocket in one of its sides. The second component is positioned on the side of the first component opposite the side with the weld pocket. A weld site on the second component is aligned with the weld pocket on the first component. A weld nugget is formed between the first and second components by applying welding energy to the weld site on the second component from the side of the second component opposite the weld pocket.

[0009] FIG. 1 is a cross-sectional view of a portion of a head suspension 10 having weld joint 12, in accordance with one embodiment of the present invention. As shown, weld joint 12 is a 2-layer weld joint, such as a flexure weld joint, securing together a first component 14 and a second component 16 of head suspension 10. In the embodiment shown, first component 14 is thicker than second component 16. In an exemplary head suspension 10, first component 14 has a thickness greater than or equal to about 50 nm and second component 16 has a thickness less than or equal to about 25 μm. In other embodiments (not shown), the first component can be thinner than the second component. In still other embodiments (also not shown), both the first and second components have the same thickness. First and second components 14 and 16 can, for example, be one or more of a load beam, a hinge, a flexure, a base plate, or an actuator arm. Using conventional methods such as etching or punching, weld pocket 20 is formed on a surface of the first component 14. Weld pocket 20 is formed such that the thickness of first component 14 within weld pocket 20 is relatively less than the thickness of first component 14 outside weld pocket 20. One side of the second component 16 is positioned against the side of first component 14 opposite the side with weld pocket 20. A weld site 22 on second component 16 is aligned with weld pocket 20 on first component 14. Components 14 and 16 are welded together by applying welding energy 24, such as from a laser (not shown), to the weld site 22 on the side of second component 16 opposite the side of the first component 14 with weld pocket 20. The welding energy 24 melts a portion of both components 14 and 16 forming weld nugget 26 which fixedly attaches the components to one another.

[0010] The method of the invention offers particular advantages when the second component 16 is thinner than the first component 14 as shown in the embodiment described in connection with FIG. 1. Because the thickness of first component 14 at the weld pocket 20 is relatively less than the thickness of first component 14 outside weld pocket 20, the amount and/or duration of welding energy 24 required for melting an area of first component 14 adjacent to weld pocket 20 will be less than that required for melting an equivalent area of first component 14 outside weld pocket 20. As such, the level of welding energy 24 required for forming weld nugget 26 in an embodiment of the present invention will be relatively less than the level of welding energy required for forming a weld nugget in the absence of a weld pocket in the first component. Consequently, the amount of molten material in the weld pool can be decreased, thereby increasing the penetration of weld nugget 26 and resulting in a relatively smaller weld diameter 28. Certain advantages attributable to a smaller weld diameter include: an increase in the real estate available for tool clamping, and trace routings and margins; more flexibility in product design by minimizing the distances between the weld joint and critical features such as component locating features, formed features, or edge features; a decrease in the number of false calls at the vision module resulting from an increase in the area surrounding the weld joint for improved inspection; a reduction in the mass of component(s) from creating the weld pockets; an inherent decrease in the number of defects associated with welding thin components; and improved resonance and shock performance of the product.

[0011] FIG. 2 is a cross-sectional view of a portion of head suspension 30 having weld joint 32 in accordance with another embodiment of the present invention. As shown, weld joint 32 is a 3-layer weld joint for securing together three components: first component 34, second component 36, and third component 38. In the illustrated embodiment, first component 34 is relatively thicker than both second and third components 36 and 38, respectively; second component 36 is relatively thinner than both first and third components 34 and 38, respectively; and third component 38 is relatively thinner than first component 34 and relatively thicker than second component 36. In other embodiments (not shown), first component 34 has a thickness greater than or equal to about 50 μm, second component 36 has a thickness between about 25 μm and 50 μm, and third component 38 has a thickness less than or equal to about 25 μm. In still other embodiments (not shown), the first component can be thinner than the second and/or third components. In alternate embodiments (also not shown), the first, second, and third components have the same thickness. First, second, and third components 34, 36, and 38 can, for example, be one or more of a load beam, a hinge, a flexure, a base plate, or an actuator arm.

[0012] Using conventional methods such as etching or punching, weld pocket 40 is formed on a surface of the first component 34. Weld pocket 40 is formed such that the thickness of first component 34 within weld pocket 40 is relatively less than the thickness of first component 34 outside weld pocket 40. One side of second component 36 is positioned against the side of first component 34 opposite the side with weld pocket 40. A weld site 42 on second component 36 is aligned with weld pocket 40 on first component 34. And, one side of third component 38 is positioned against the side of second component 36 opposite the side with weld pocket 40 on first component 34. A weld site 43 on third component 38 is aligned with both weld pocket 40 on first component 34 and the weld site 42 on second component 36. First, second, and third components 34, 36, and 38, respectively, are welded together by applying welding energy 44, such as from a laser (not shown), to the weld site 43 on the side of third component 38 opposite the side of first component 34 with weld pocket 40. The welding energy 44 melts a portion of each component 34, 36, and 38, forming weld nugget 46 which fixedly attaches the three components to one another.

[0013] The method of the invention for securing together three components as described in connection with the embodiment shown in FIG. 2 offers advantages similar to those previously described in connection with the embodiment shown in FIG. 1. As with the embodiment of FIG. 1, the level of welding energy 44 required for forming weld nugget 46 in an embodiment of the present invention will be relatively less than the level of welding energy required for forming a weld nugget in absence of a weld pocket. Consequently, the amount of molten material in the weld pool will be decreased, thereby increasing the penetration of weld nugget 46 and resulting in a relatively smaller weld diameter 48. As previously discussed, there is a preference for smaller weld diameters because of the resultant advantages.

[0014] As discussed in the foregoing, the level of welding energy applied to the components effects the amount of molten material in the weld pool with consequential effect on the weld nugget and the weld diameter. In accordance with an embodiment of the present invention, the level of welding energy is adjusted to provide a weld diameter less than or equal to the diameter of the weld pocket. In accordance with another embodiment of the present invention, the level of welding energy is adjusted to ensure that the weld nugget extends into the material of the component having the weld pocket to a depth less than or equal to the thickness of the component at the location of the weld pocket. In one embodiment, the weld pocket can have diameters of about 200 μm and greater, and depths of about 25 μm and greater as dictated by the thickness of the component having the weld pocket. However, the diameters and depths of the weld pockets can be greater and/or smaller in other embodiments. The weld nugget can also be greater in diameter than the diameter of the weld pocket. The weld nugget also extends to a depth equal to and beyond the bottom of the weld pocket in other embodiments.

[0015] Although the invention has been described with reference to certain embodiments, those skilled in the art will recognize that modifications can be made to the form and detail without departing from the spirit and scope of the invention. In particular, although described in connection with welding together thick and thin components, the method is equally applicable for welding together two or more equally thin or equally thick components.