Patent Application
20110018135
This application claims priority from French Application for patent No. 09-55237 filed Jul. 27, 2009, the disclosure of which is hereby incorporated by reference.
The present invention relates to the field of integrated circuit chips and packages comprising such chips, and more particularly to the wire means used to electrically link such chips to other means or devices.
A method of electrically connecting a wire to an electrical bonding pad of an integrated circuit chip is proposed.
An electrical connection method may comprise the placing of an intermediate electrical interconnect block on said electrical bonding pad and the placing of one end of the electrical lead wire on the intermediate interconnect block.
The method may comprise the choice, for the interconnect block, of a material more malleable or ductile than that of the electrical lead wire and/or of the electrical bonding pad.
The method may comprise the formation of a ball at the end of a secondary wire, the placing of this ball on the electrical bonding pad in order to form the interconnect block and the breaking of the secondary wire at a point adjacent or close to the interconnect block.
The method may comprise the formation of a ball at the end of the electrical lead wire and the placing of this ball on the interconnect block.
Before the placing of the end of the electrical lead wire, the interconnect block may have a front face approximately parallel to that of the electrical bonding pad.
The interconnect block may be soldered to the electrical bonding pad.
The electrical lead wire may be soldered to the interconnect block.
The electrical bonding pad may be chosen to be made of aluminum, the interconnect block may be chosen to be made of gold and the electrical lead wire may be chosen to be made of copper, or alternatively alloys of such materials.
An electronic device comprising an integrated circuit chip is also proposed, that comprises at least one electrical bonding pad, an intermediate electrical interconnect block soldered to the electrical bonding pad, and an electrical lead wire, one end of which is soldered to the interconnect block.
The interface between the interconnect block and the end of the electrical lead wire may be approximately parallel to the face of the electrical bonding pad.
The electrical lead wire may comprise a ball soldered to the interconnect block.
The diameter of the interconnect block and that of the end of the electrical lead wire may be between 1.5 and 3 times the diameter of the electrical lead wire.
The interconnect block may be made of a material more malleable or ductile than that of the electrical lead wire and/or of the electrical bonding pad.
The pad may be made of aluminum or an aluminum-based alloy, the interconnect block may be made of gold or a gold-based alloy and the electrical lead wire may be made of copper or a copper-based alloy.
An electronic package comprising at least one device as described hereinabove is also proposed.
An electronic device comprising an integrated circuit chip and an electrical lead wire will now be described by way of non-limiting example, and illustrated by the drawing in which:
An electronic device 1, represented in
The semiconductor device 1 also comprises, on each pad 3, an intermediate electrical interconnect block 4 soldered to an external flat face 5 of the pad 3.
The semiconductor device 1 also comprises a plurality of electrical lead wires 6, each wire 6 having an enlarged end 7 soldered to an interconnect block 4.
The interface 8 between the electrical interconnect block 4 and the end 7 of the electrical lead wire 6 may be approximately parallel to the face 5 of the pad 3.
The link between the intermediate interconnect block 4 and the pad 3 and the link between the end 7 of the electrical lead wire 6 and the intermediate interconnect block 4 may be made by a eutectic solder joint.
In a first step, the intermediate interconnect block 4 may be placed on the pad 3, then, in a second step, the end 7 of the electrical lead wire 6 may be placed on the intermediate interconnect block 4.
By way of example, these placing operations may be carried out as follows.
As shown in
As shown in
Thereafter, as shown in
The ball 11a is thus transformed in order to form the interconnect block 4, which is approximately in the form of a cylinder or a truncated cone whose large base is on the pad 3, the front face 4a of the interconnect block 4 being approximately parallel to the face 5 of the pad 3.
That having been done, as shown in
As shown in
Thereafter, the head 14 of the tool 13 may be moved along the electrical lead wire 6 and used to solder another point of this wire onto a pad, for example of another means that is not represented.
The above operations may be carried out on the other interconnect blocks 5 of the chip 2.
The diameter of the secondary wire 11 may be greater than the diameter of the electrical lead wire 6. The ball 11a that is formed at the end of the secondary wire 11 may be larger than the ball 6a that is formed at the end of the electrical lead wire 6. This may make it possible for the enlarged end 7 of the lead wire 6 to be correctly formed on the interconnect block 4. The diameter of the secondary wire 11 may be equal to or greater than the diameter of the electrical lead wire 6.
The result of the above is that providing an interconnect block 4 between the pad 3 of the integrated circuit chip 2 and the electrical lead wire 6 makes it possible to choose materials which normally do not allow a strong and stable direct bond between one another to form the pad 3 and the lead wire 6.
It is in fact made possible to choose materials that are able to create a strong stable bond between one another for the pad 3 and the interconnect block 4, and also materials that are able to create a strong stable bond between one another to form the interconnect block 4 and the lead wire 6.
Moreover, it is also made possible to choose a material more malleable or ductile than that of the pad 3 and/or of the electrical lead wire 6 for the interconnect block 4. This makes it possible to limit the compressive stresses on the chip 2.
Furthermore, the pitch between the electrical bonding pads 3 of a chip 2 may be reduced.
By way of example, the electrical bonding pad 3 may be made of aluminum, the electrical interconnect block 4 may be made of gold and the electrical lead wire 6 may be made of copper. Alloys may also be used. The existence of a gold electrical interconnect block makes it possible to obviate the difficulties associated with directly soldering a copper electrical lead wire onto an aluminum electrical bonding pad.
According to one embodiment, the diameter of the interconnect block 4 and the diameter of the end 7 of the electrical lead wire 6 may be approximately between 1.5 and 3 times the current diameter of the electrical lead wire 6. The diameter of the interconnect block 4 may be smaller than the diameter of the end 7 of the electrical lead wire 6. The height of the interconnect block 4 and the height of the end 7 of the electrical lead wire 6 may be approximately between 0.75 and 2 times the current diameter of the electrical lead wire 6.
In particular, the current diameter of the electrical lead wire 6 may be between 20 and 25 microns, the diameter of the interconnect block 4 may be between 40 and 45 microns, the height of the interconnect block 4 may be between 20 and 25 microns, and the diameter of the end 7 of the electrical lead wire 6 may be between 35 and 40 microns.
Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0955237 | Jul 2009 | FR | national |
