Patent Application
20200038982
Data-storage devices using various kinds of media, such as optical disks, magnetic-recording disks, magneto-optical disks, and similar disks for data-storage devices are known in the art. In particular, hard disk drives (HDDs) have been widely used as data-storage devices that have proven to be indispensable for contemporary computer systems. Moreover, HDDs have found widespread application to motion picture recording and reproducing apparatuses, car navigation systems, digital cameras, cellular phones, and similar devices, in addition to computers, due to their outstanding information-storage characteristics. An HDD includes a head-slider for accessing a magnetic-recording disk and an actuator for supporting the head-slider and rotating the head-slider in proximity to the recording surface of the magnetic-recording disk. The actuator includes a suspension to which the head-slider is affixed. The lift generated by the airflow between the head-slider and the spinning magnetic-recording disk balances the force applied to the head-slider by the suspension to allow the head-slider to fly in proximity to the recording surface of the magnetic-recording disk.
Solder-ball bonding (SBB) (or solder-sphere bonding) is a method for electrically interconnecting a slider with the transmission lines of the suspension. An SBB method disposes solder balls between connection pads of a head-slider and connection pads of a suspension and performs a reflow process with a laser beam to electrically interconnect the connection pads of the head-slider and the connection pads of the suspension. The solder balls undergo a reflow process within an atmosphere of an inert gas such as nitrogen to prevent the solder surfaces from being oxidized. To melt a solder ball disposed between two connection pads by a reflow process with a laser beam, the solder ball must be correctly disposed between the pads. However, a head-slider is a tiny component and further miniaturization of the head-slider is under development. Consequently, connection pads and solder balls disposed on the head-slider are becoming smaller so that disposing solder balls at the proper locations for soldering is becoming progressively more difficult.
Implementations described and claimed herein address the foregoing problems by providing a soldering method including mixing a plurality of spheres wherein a first number of the plurality of the spheres have a diameter that is at least fifty (50) percent larger than the rest of the plurality of spheres.
These and various other features and advantages will be apparent from a reading of the following detailed description.
A further understanding of the nature and advantages of the various implementation disclosed herein may be realized by reference to the figures, which are described in the remaining portion of the specification.
Reference will now be made in detail to the alternative embodiments of the present technology disclosed herein. While the technology will be described in conjunction with the alternative embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
A singulation disk 110 may be configured at the bottom of the bond-head hopper 102 such that the solder spheres 104 and larger spheres 106 are constantly in contact with the singulation disk 110 and the solder spheres 104 tumble into the holes 112 of the singulation disc 110. This is illustrated by a solder sphere 114 dropping on the singulation disk 110. The singulation disk 110 is used for singulating the solder spheres from the bond-head hopper 102 into the capillary 150. The singulation disk rotates around its axis with the solder spheres in the openings 112. The singulation disk 112 is also configured to drop the solder spheres from the openings 112 into a drop chute 146 into the capillary 150.
A laser 140 is configured above the capillary 150 such that a laser signal is directed onto the solder sphere 114 when it is in the capillary 150. The laser signal melts the solder sphere 114 at a desired location to create a soldered bond between a suspension circuit of a head-gimbal assembly (HGA) and a slider. In one implementation, the solder sphere 114 may be pressurized through the capillary 150 via a nitrogen (N2) supply 160. The solder sphere 114 falls via the drop chute 146 into the capillary 150. Once the pressure from the nitrogen supply 160 reaches a predetermined threshold, it initiates the laser to be targeted on the solder sphere 114 at the end of the capillary 150. The laser energy results in melting of the solder sphere 114 and the melted solder sphere 114 jets out where the solder join between the suspension circuit of a head-gimbal assembly (HGA) and a slider is to be formed.
As the size of the HGA assembly gets smaller and smaller, the solder spheres used to form the solder joint also gets smaller. Using solder spheres of increasingly smaller diameter results in the solder spheres bridging and clumping in the bond-head hopper 102. Solder bridging results from the smaller solder spheres causing a bridge or arch on top of the hole at the bottom where the solder sphere exits towards the singulating disk. Such bridging and clumping results in significant downtime for the soldering apparatus 100.
For example, when the diameter of the solder spheres is in the range of 40 um or 45 um, the soldering apparatus 100 may not maintain its units per hours (UPH) requirement through a complete work day. Furthermore, such bridging and clumping of the solder-spheres in the bond-head hopper 102 also results in more bond-head service calls and therefore reducing the bond-head life (time between bond-head service calls).
In one implementation disclosed herein, the bond-head hopper 102 is configured to include some solder spheres that have a diameter that is significantly higher than diameter of the rest of the plurality of solder spheres. For example,
Providing the combination of solder spheres 104 and larger spheres 106 in the bond-head hopper 102 results in reduced amount of clumping and bridging between the smaller solder spheres 104 in the bond-head hopper 102, which results in increased bond-head life and increased UPH. In one implementation, the combination of solder spheres 104 and larger spheres 106 is maintained such that approximately half of the volume of the solder spheres in the bond-head hopper is made of larger spheres 106.
The solder spheres 104 and the larger spheres 106 may be made of a combination of metals. In one implementation, the larger spheres 106 may be made of material other than the solder material. Examples of such alternative material are nickel, tungsten carbide, tungsten, etc. In one implementation, the material of the larger spheres 106 is made of a material that is of equal or greater density than the density of the solder spheres 104. In one implementation, the solder spheres 104 and larger spheres 106 may be made of combination of tin, silver, and copper. In one implementation, the larger spheres 106 are not harder than the solder spheres 104.
The graph 304 discloses average bonding cycle times in milli-seconds (ms) on the y-axis for a soldering apparatus where the bond-head hopper has solder spheres with diameter of 40 um mixed with solder spheres having significantly higher diameter. As seen therein, the bonding cycle times are about 100 ms for as much as up to 60,000 solder spheres bonded with only a few variations or spikes in the average overall bonding cycle times. In this implementation, the number of solder spheres with larger diameter makes up about half of the volume of the total volume of the solder spheres in the bond-head hopper.
In one implementation, the bond-head hopper has about 16,000 solder spheres with a diameter that is substantially higher than the remaining solder spheres being approximately 250,000. In such an implementation, the solder spheres with the higher diameter may have diameter of approximately at least fifty (50) percent higher than diameter of rest of the plurality of solder spheres. For example, the larger solder spheres may have a diameter of 200 μm whereas the smaller solder spheres may have a diameter of 50 μm. Alternatively, the larger solder spheres may have a diameter of 250 μm whereas the smaller solder spheres may have a diameter of 40 μm. In one implementation, the solder spheres with larger diameter form approximately half the volume of the total volume of the solder spheres in the bond-head hopper.
The above specification, examples, and data provide a complete description of the structure and use of example implementations. Since many implementations of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Furthermore, structural features of the different implementations may be combined in yet another implementation without departing from the recited claims. The implementations described above, and other implementations are within the scope of the following claims.
