Insulated bonding wire tool for microelectronic packaging

A method for insulating a bonding wire that includes the steps of attaching a bonding wire to a bond pad and coating the bonding wire with an insulating liquid while drawing the bonding wire through a bond tool from the bond pad to a package lead.

BACKGROUND OF THE INVENTION

The present invention relates generally to microelectronic packaging. More specifically, but without limitation thereto, the present invention relates to insulating bonding wires to avoid package defects resulting from short circuits between adjacent bonding wires.

Bonding wires are used in microelectronic packaging to connect bond pads of a chip or die to package leads. The bonding wires are typically made of gold or aluminum and have a thin diameter of only about 30 microns.

As chip size becomes smaller as a result of improvements in manufacturing and chip density, and as the size of the microelectronic package increases, the bonding wires have to be made longer and spaced more closely together. The increased length and closer spacing increases the probability that adjacent bonding wires will deviate from their intended position and come into electrical contact with one another, resulting in a defective package.

Another problem with current techniques for attaching bonding wires is that wires may not cross each other to avoid coming into electrical contact with one another and have to be attached in an array, one after another, restricting the versatility of the microelectronic package.

SUMMARY OF THE INVENTION

The present invention advantageously addresses the needs above as well as other needs by providing a method and apparatus for insulating a bonding wire.

In one embodiment, the invention may be characterized as a method for insulating a bonding wire that includes the steps of attaching a bonding wire to a bond pad; coating the bonding wire with an insulating liquid while drawing the bonding wire through a bond tool from the bond pad to a package lead; and attaching the bonding wire to the package lead.

In another embodiment, the invention may be characterized as an apparatus for insulating a bonding wire that includes a dispensing tool coupled to a bond tool for forming a coating of an insulating liquid on a bonding wire after the bond tool attaches the bonding wire to a bond pad.

The features and advantages summarized above in addition to other aspects of the present invention will become more apparent from the description, presented in conjunction with the following drawings.

Corresponding reference characters indicate corresponding elements throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description is presented to disclose the currently known best mode for making and using the present invention. The scope of the invention is defined by the claims.

FIG. 1is a magnified diagram illustrating a dispensing tool for insulating a bonding wire. Shown are a dispensing tool102, a bond tool104, a bonding wire106, a die107, a bond pad108, a nozzle orifice110, an insulating liquid112, a microelectronic package113, and a package lead114.

The die107is mounted on the microelectronic package113according to standard techniques well known in the art. The microelectronic package113has a plurality of package leads such as the package lead114that are connected by bonding wires to each bond pad108. Current methods connect each bond pad108to each corresponding package lead114by an uninsulated bonding wire as explained above. In contrast to these methods, the following embodiments of the present invention connect each bond pad108to each corresponding package lead114by an insulated bonding wire.

Still referring toFIG. 1, the dispensing tool102has moved to a non-coating position away from the bond tool104to avoid mechanical interference while the bond tool104attaches the bonding wire106to the bond pad108according to standard techniques well known in the art.

The dispensing tool102includes the nozzle orifice110for dispensing the insulating liquid112. Examples of the insulating liquid112are heat-cured epoxies and ultra-violet light-cured epoxies and polymers. The insulated liquid112may be pumped through the nozzle orifice110according to well known techniques for pumping liquids. In this example, the nozzle orifice110has a shape that is relatively narrow in the dimension parallel to the bonding wire106near the end of the bond tool104and relatively wide in the dimension perpendicular to the bonding wire106. Typical dimensions for the nozzle orifice110are 100 microns in the dimension perpendicular to the bonding wire106and 50 microns in the dimension parallel to the bonding wire106. The nozzle orifice110also has an arcuate shape that partially surrounds the bonding wire106in the coating position to apply a uniform thickness of the insulating liquid112to the bonding wire106. Other shapes for the nozzle orifice110may be used to suit specific applications and materials used for the insulating liquid112.

FIG. 2is a magnified diagram illustrating the dispensing tool102moved to a coating position for applying the insulating liquid112to the bonding wire106after the bond tool102has begun drawing the bonding wire106. In the coating position, the bonding wire106is partially surrounded by the nozzle orifice110of the dispensing tool102to apply a uniform thickness of the insulating liquid112to the bonding wire106.

FIG. 3is a magnified diagram illustrating the dispensing tool102coating the bonding wire106. The insulating liquid112flows from the nozzle orifice110of the dispensing tool102around the bonding wire106as the bonding wire106is drawn through the bond tool104from the bond pad108toward the package lead114. The dispensing tool102is coupled to the bond tool104so that the nozzle orifice110follows the end of the bonding wire106being drawn through the bond tool104.

FIG. 4is a magnified diagram illustrating the dispensing tool102after coating the bonding wire106. When the bond tool104has drawn the bonding wire106from the bond pad108to the package lead114, the flow of the insulating liquid112is stopped, and the dispenser tool102moves to the non-coating position to avoid mechanical interference with the bond tool104.

FIG. 5is a magnified diagram illustrating the attachment of the coated bonding wire106to the package lead114. The bond tool104terminates and attaches the bonding wire106to the package lead114according to standard techniques well known in the art. An energy source116such as a heat gun or an ultraviolet light may be used to solidify the insulating liquid112coating the bonding wire106. Alternatively, the insulating liquid112may be a self-curing material.

Additional bonding wires may be added and insulated in the same manner as the bonding wire106to complete the microelectronic package113. Because each bonding wire106has been electrically insulated, bonding wires may cross over one another, have any desired length, and may be attached in any desired sequence without causing package defects. Insulating the bonding wires thus lowers the package cost, increases the pin density of the package, and improves the versatility of the package.

Other modifications, variations, and arrangements of the present invention may be made in accordance with the above teachings other than as specifically described to practice the invention within the spirit and scope defined by the following claims.