US 20120145770 A1
A main body of an apparatus for delivering shielding gas during wire bonding of an electronic device has a through-hole in the main body which is sized for allowing a capillary tip of a bonding tool to be insertable through the main body when performing wire bonding. At least one gas outlet located on a bottom surface of the main body adjacent to the through-hole is operative to direct an inert gas in a direction towards the electronic device. At least one gas inlet in the main body is operative to supply the inert gas to the through-hole and to the gas outlet.
1. An apparatus for delivering shielding gas during wire bonding of an electronic device, the apparatus comprising:
a main body;
a through-hole in the main body which is sized for allowing a capillary tip of a bonding tool to be insertable through the main body when performing wire bonding;
at least one gas inlet for receiving an inert gas into the main body, and at least one gas outlet for discharging the inert gas from the main body, the at least one gas inlet and the at least one gas outlet defining a plurality of gas paths along which the inert gas flows, the plurality of gas paths comprising an inner gas path within the main body extending along the through-hole and an outer gas path external to the main body extending towards the electronic device on which the capillary tip performs wire bonding; and
a secondary gas conduit formed separately in the main body from the gas inlet and formed on top of the gas inlet for increasing a supply of inert gas towards the top of the through-hole.
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The invention relates to the forming of electrical connections on electronic components, and in particular to the connection of wires to electronic components during wire bonding.
Wire bonding is used to connect electrical contact points of different devices, or different electrical contact points of the same device. When bonding wires made of reactive materials such as copper or aluminum are used for wire bonding, there is a tendency for oxidation of the wire to occur when the heated material reacts with oxygen in the atmosphere. Oxidation of the wire deteriorates the quality of the subsequent wire bonds that are formed. Therefore, it is necessary to provide a shielding gas comprised of a relatively inert gas such as nitrogen, hydrogen or argon gas to cover and protect the wire during ball formation of a wire ball-bonding process.
The continuing emphasis on better shielding of copper wire during bonding by providing nitrogen and/or hydrogen gas to shield the wire is driving the development of systems that ensure that the gas is captured within the sparking region of the wire, where a molten ball is formed from the wire for copper ball bonding.
An apparatus for containing shielding gas when supplying the inert gas to bonding wire is disclosed in U.S. Pat. No. 6,234,376 entitled “Supplying a Cover Gas for Wire Ball Bonding”. The apparatus includes a gas-containment tube to direct shielding gas to the bonding wire. Transverse in-line orifices are made in the tube to allow the capillary of the bonding tool to enter the gas-containing tube for ball formation, and then to pass through the tube to bond the ball onto a bonding surface.
Another prior art apparatus for containing shield gas is disclosed in U.S. Pat. No. 7,628,307 entitled “Apparatus for Delivering Shielding Gas During Wire Bonding”. Shielding gas is supplied during the bonding of wires to electronic components by way of an apparatus comprising a main body with an elongated slot having a width that extends into the main body from a side of the main body generally in a first direction, and the slot also extends from a top surface to a bottom surface of the main body in a second direction perpendicular to the first direction for the width of the slot. A tip of the capillary is operable to pass through the slot in the second direction while a gas outlet supplies shielding gas into the slot.
A shortcoming of conventional approaches to deliver shielding gas to the capillary is that prior art systems focus on preventing the wire from native oxidation mainly during the sparking of the wire to form a molten ball. There is loss of gas at the openings of the tubes or apparatus such that oxidation protection is not possible outside these openings. Thus, they do not effectively provide gas coverage to prevent oxidation when wire bonding is being performed, or when moving the capillary sideways to various locations unless the capillary is always located inside the gas containment tube during such movement. This limits the versatility of such systems.
It would therefore be desirable to develop an apparatus for supplying shielding gas to a bonding wire that ensures that the wire is protected by shielding gas not only within the sparking range but also along the travelling path of the capillary to the bonding pad, and thus ensuring the quality of the molten ball both before and during bonding of the same is achieved.
It is thus an object of the invention to seek to provide improved gas coverage to bonding wire in order to prevent oxidation of the wire not only during sparking, but also during movement of the capillary and in particular during bonding.
Accordingly, the invention provides an apparatus for delivering shielding gas during wire bonding of an electronic device, comprising: a main body; a through-hole in the main body which is sized for allowing a capillary tip of a bonding tool to be insertable through the main body when performing wire bonding; at least one gas outlet on a bottom surface of the main body and located adjacent to the through-hole, the gas outlet being operative to direct an inert gas in a direction towards the electronic device; and at least one gas inlet in the main body operative to supply the inert gas to the through-hole and the gas outlet.
It would be convenient hereinafter to describe the invention in greater detail by reference to the accompanying drawings which illustrate preferred embodiments of the invention. The particularity of the drawings and the related description is not to be understood as superseding the generality of the broad identification of the invention as defined by the claims.
Examples of preferred embodiments of a gas supplying apparatus in accordance with the invention will now be described with reference to the accompanying drawings, in which:
When the capillary tip is in the sparking position inside the through-hole 12, the capillary tip primarily receives inert gas 20 which is introduced from the gas channels 14 and fed into the through-hole 12 to protect the bonding wire from oxidation during sparking. As illustrated in
Inert gas 20 introduced from the gas channels 14 is also fed to the nozzles 18 located at the bottom surface of the main body 10. The nozzles 18 direct the inert gas 20 towards and onto the die 24. Therefore, the tip of the capillary 22 primarily receives the inert gas 20 supplied from the nozzles 18 at its bonding position 22 b outside the through-hole so that the inert gas 20 protects the bonding wire from oxidation during wire bonding. Multiple nozzles 18 connected to the gas channels 14 may be formed surrounding the through-hole 12 to increase gas coverage at the tip of the capillary 22 at its bonding position 22 b. Hence, the tip of the capillary 22 can be protected by the inert gas 20 even when it is moving from one die to another while the tip of the capillary 22 is protruding from the bottom surface of the main body 10. In prior art gas supplying apparatus, the capillary 22 would be protected by inert gas 20 only when its tip is located inside a main body of the gas supplying apparatus, thereby limiting the degree of anti-oxidation protection provided to the bonding wire.
Inert gas 20 also flows towards the nozzles 18 at the bottom surface of the main body 10 through connectors such as slots 26 formed in the main body 10 leading from the gas channels 14 to the nozzles 18. When the capillary 22 is lowered towards the die 24, the bonding wire at the tip of the capillary 22 continues to be protected by inert gas 20 ejected from the nozzles 18.
Inert gas 20 also flows towards the shower holes 36 at the bottom surface of the main body 28 via the shower ring 34 which is formed inside the main body 28. The shower ring 34 receives its supply of inert gas 20 from the second internal gas channel 32. When the capillary 22 is lowered towards the die 24, the bonding wire at the tip of the capillary 22 continues to be protected by the shower of inert gas 20 ejected from the shower holes 36.
Alternatively, the outer ring outlet 52 may comprise multiple holes, nozzles or slots instead of the single uninterrupted slot. The outer ring 50 is connected to a supply of inert gas 20 through outer gas channels 46 which run parallel to the internal gas channels 14 along the main body 48.
It should be appreciated that the gas supplying apparatus according to the preferred embodiments of the invention improve the efficiency of shielding of bonding wire that is made of an oxidizable material by an inert gas 20. Oxidation protection may take place not only during sparking when the bonding wire is located within the main body 10, but also when the tip of the capillary 22 and the bonding wire exits the main body 10 during the time the capillary 22 is making wire connections, and when the capillary 22 moves between different bonding locations. By extending inert gas 20 coverage along the travelling path of the capillary 22, the quality of the ball bonds made to form wire connections with surfaces can generally be improved by greater protection of the bonding wire from oxidation. Moreover, better control of the inert gas flow is possible by introducing multiple gas channels 14, secondary gas conduits 40 and other gas paths.
The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the above description.