Metal fusion bonding – Solder form
Reexamination Certificate
1999-12-20
2001-11-20
Dunn, Tom (Department: 1725)
Metal fusion bonding
Solder form
C228S246000, C228S254000
Reexamination Certificate
active
06318624
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for attaching a magnetic read/write transducer to an electrical lead and more specifically to a method that includes using a solder balltape and a laser to make the electrical connection between the transducer and a lead which is incorporated in an integrated suspension.
BACKGROUND ART
In conventional head gimbal assembly (HGA) technology utilized in magnetic disk drives, the slider is mechanically attached to the flexure of the suspension by epoxy bonding. The electrical connection between the thin film magnetic head transducer and the read/write electronics is made by twisted pairs of wires which run the length of the suspension. The ends of these wires are bonded to the gold transducer termination pads on the slider.
In a new generation of HGA technology, the suspension is comprised of a laminated structure. The twisted pairs of wires of the old technology are replaced by conductors that are etched into one of the layers of the laminated suspension. For example, U.S. Pat. No. 4,996,623 illustrates the use of a suspension having etched copper lead structures. In another variation of this technology, the conductors are formed by vapor deposition plating. The electrical connections between the head transducer and the conductors are achieved by soldering. Generally, a solder joint is established between a reflowed solder bump on the slider and either the copper lead pads or to solder bumps applied to the lead pads. In this methodology, the solder bump is applied to the slider at the wafer level. Application of the solder at this level leads to many problems, such as oxidation of the solder bump which inhibits good joint formation.
In general, the use of solder balls for attaching the slider to a slider support means is known in the art. For example, Ainslie et al., in U.S. Pat. No. 4,761,699, disclose the use of reflowed solder balls for making both the mechanical attachment of the slider to the suspension and the electrical connection of the transducer to the disk file read/write electronics. Additionally, Ainslie et al., in U.S. Pat. No. 4,789,914, disclose a soldering technique for making an electrical attachment of a cable to a transducer on the backside of a slider. In the semiconductor industry, electrical connections within a semiconductor device have long been made using Tape Automated Bonding (TAB) techniques. For example U.S. Pat. No. 4,814,855 illustrates the use of a laser technique to produce ball-like areas on the ends of leads that are used to make electrical connections in the semiconductor device.
SUMMARY OF THE PRESENT INVENTION
The present invention utilizes a laser technique to form solder balltapes which allow the soldering connections between the transducer and the etched leads to be formed entirely after the slider has been manufactured. Briefly, the preferred embodiment of the present invention is a solder balltape formed by directing a pulse of focused laser radiation at an end of a rectangular strip of Sn/Pb solder. The laser radiation causes a spherical head of solder to form on one end of the balltape with an elongated tail extending away from the head. The balltape is then positioned with the solder head in contact with the electrical pad of the read/write transducer and an electrical lead positioned on the flexure or slider support region of the suspension. A second pulse of laser radiation is used to melt the solder head. When the solder cools, the solder head forms a right angle fillet joint which electrically connects the electrical pad of the read/write transducer and the electrical lead. The tail is then removed from the balltape leaving a relatively smooth right angle fillet joint.
In the preferred embodiment the electrical lead is formed in the upper layer of a laminated material from which the suspension is formed. In some applications a second solder bump is positioned between the electrical lead and the solder ball tape before the right angle fillet joint is formed. In another application, the balltape is used to form a solder bump directly on the electrical pad of the read/write transducer before the slider is mounted on the suspension.
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U.S. application No. 08/678,654, Pattanaik et al., filed Jul. 11, 1996.
Pattanaik Surya
Reiley Timothy C.
Simmons Randall G.
Cooke Colleen P.
Dunn Tom
International Business Machines - Corporation
Pagel Donald J.
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