Solder bump height stabilization for micro and fine pitch electrode pads
Approaches to pre-forming solder bumps, such as for use in electrically connecting a head slider and a suspension assembly for a hard disk drive, involves applying a height stabilizer plate over a shared solder paste applied over a substrate housing electrode pads, and reflowing the solder paste with the plate applied to create solder bumps electrically coupled to the pads. Use of such a plate functions to stabilize and contain the solder paste and create uniform solder bumps across the series of pads, where the plate may be composed of a heat-resistant and anti-solder-wetting material. The solder bump pre-forming techniques generally enable solder bonding of extremely small electrical interconnection pads.
1. A method of manufacturing, the method comprising:
applying a shared solder paste over a substrate comprising a plurality of electrode pads;
applying a height stabilizer plate over the solder paste, comprising:
applying a planar plate applied at an angle to the substrate to produce solder bumps having a tapered height across a respective electrode pad, or
applying a multi-planar shaped plate applied to produce solder bumps having a first raised height along a first portion of a respective electrode pad and a second lower height along a second portion of the respective electrode pad;
reflowing the solder paste with the height stabilizer plate applied, creating the solder bumps electrically coupled to the electrode pads;
removing the height stabilizer plate; and
removing excess solder paste in respective gaps between the electrode pads and the solder bumps.
2. The method of claim 1 , wherein the substrate is coupled with a suspension, the method further comprising:
reflowing the solder bumps to electrically couple the electrode pads with corresponding electrode pads of a head slider.
3. The method of claim 2 , wherein a number of the electrode pads electrically coupling the head slider to the suspension is greater than or equal to sixteen (16).
4. The method of claim 1 , wherein a diameter of the solder bumps is less than or equal to 25 micrometers (μm).
5. The method of claim 4 , further comprising:
wherein the solder bumps have a pitch according to which the gaps between the solder bumps constituent to the substrate are less than or equal to 17.5 micrometers (μm).
6. The method of claim 1 , wherein applying the height stabilizer plate includes applying the plate composed of a material from a group consisting of glass, ceramic, titanium, and stainless steel.
7. The method of claim 1 , wherein applying the height stabilizer plate includes applying the height stabilizer plate directly over the solder paste.
8. A head gimbal assembly (HGA) of a hard disk drive (HDD), the HGA comprising:
a head slider; and
a suspension produced according to the method of claim 1 ,
wherein:
the solder bumps comprise a plurality of substantially uniform solder bumps of the suspension over the plurality of electrode pads of the suspension, and
the solder bumps have a tapered height across a majority of a corresponding electrode pad or have a first raised height along a first portion of a corresponding electrode pad and a second lower height along a second portion of the corresponding electrode pad.
9. The HGA of claim 8 , wherein a number of the electrode pads of the suspension is greater than or equal to sixteen (16).
10. The HGA of claim 8 , wherein a diameter of the solder bumps is less than or equal to 25 micrometers (μm).
11. The HGA of claim 10 , further comprising:
wherein the solder bumps have a pitch according to which the gaps between the solder bumps are less than or equal to 17.5 micrometers (μm).
12. A hard disk drive suspension produced according to the method of claim 1 , wherein:
the solder bumps comprise a plurality of substantially uniform solder bumps of the suspension over the plurality of electrode pads of the suspension, and
the solder bumps have a tapered height across a majority of a corresponding electrode pad or have a first raised height along a first portion of a corresponding electrode pad and a second lower height along a second portion of the corresponding electrode pad.
13. A system for forming a plurality of uniform solder bumps on a workpiece, the system comprising:
means for reflowing a shared solder paste applied over a substrate comprising a plurality of electrode pads; and
means for controlling a height of a plurality of solder bumps made from the shared solder paste and each electrically connected to one of the plurality of electrode pads, while inhibiting electrical bridging among adjacent solder bumps of the plurality of solder bumps, wherein the means for controlling a height of the plurality of solder bumps produces the solder bumps having a tapered height across a respective electrode pad, or produces the solder bumps having a first raised height along a first portion of a respective electrode pad and a second lower height along a second portion of the respective electrode pad.
14. The system of claim 13 , wherein the means for controlling comprises a material from a group consisting of glass, ceramic, titanium, and stainless steel.