METHOD OF MANUFACTURE INTEGRATED CIRCUIT PACKAGE
An integrated circuit package may be formed using a leadframe having an open space extending therethrough. A shunt is located within the open space such that it is not in contact with any portion of the leadframe. Tape may be applied to the lower surface of the leadframe to support the shunt and hold it in place relative to the leadframe until wirebonding and encapsulation have been completed. Thereafter, the tape may be removed.
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An integrated circuit package serves to physically and electrically connect an integrated circuit device (housed within the integrated circuit package) to a printed circuit board. One type of integrated circuit package is known as a “flat no-leads package”. This type of package is a surface-mount technology that connects an integrated circuit device to surfaces of the printed circuit board without the use of through-holes. Perimeter lands on the package bottom provide electrical connections to the printed circuit board. Flat no-leads packages typically include a planar copper leadframe substrate upon which the integrated circuit device is mounted. The leadframe and the integrated circuit device are typically encapsulated within a molding material. Flat no-lead packages generally include an exposed thermal pad to improve heat transfer out of the integrated circuit device (and into the printed circuit board). There are various types of flat no-leads packages in use, including QFN (quad-flat no-leads) and DFN (dual-flat no-leads) variations.
For certain integrated circuit package applications, it is required that a rectangular copper alloy slug or shunt be included in the package with one surface exposed for soldering.
As discussed previously, for certain integrated circuit package applications, it is required that a rectangular copper alloy slug or shunt be included in the package with one surface exposed for soldering. The copper alloy used in the shunt may, for example, be of the type sold under the trademark MANGANIN®, and may, for example, have a composition of about 86% copper, 12% manganese, and 2% nickel. Because of the relatively high cost of this alloy, it is advantageous to have the leadframe formed from a less expensive leadframe alloy, for example, the alloy sold under the trade designation “CDA194”. CDA194 is well suited and characterized both thermally and mechanically for use in leadframes. It is also formulated to facilitate stamping and etching of leadframes.
In general terms, an integrated circuit package, along with a method of manufacturing the package, are disclosed herein. The disclosed package and method of manufacture provide the ability, for example, to incorporate a slug or shunt made of a more expensive copper alloy (e.g., MANGANIN®) into a package having its leadframe manufactured from a less expensive leadframe alloy. The alloy CDA194, as mentioned above, is widely used for leadframes and is readily available from rolling mills. MANGANIN®, however, is generally less widely used and available.
The process of manufacturing the package disclosed herein begins by providing a leadframe, e.g., the leadframe 40,
With reference now to
The leadframe 40 may be constructed from a relatively inexpensive leadframe alloy, for example, the alloy sold under the trade designation “CDA194”. Alternatively, the leadframe 40 may be constructed of copper or another copper alloy, other metal or metal alloy.
Continuing with the description of the methodology, and with reference now to
With reference to
With further reference to
Next, with continued reference to
After wire bonding has been completed, in a manner as described above, the leadframe 40, integrated circuit device 110 and shunt 100 may be encapsulated within a molding material (e.g., the molding material 122,
Once the molding material has been applied and it has hardened, it serves to secure the location of the shunt 100 relative to the leadframe 40. Accordingly, after the encapsulation step has been completed, the tape 90 may be removed from the leadframe 40. Thereafter, the individual leadframes in the leadframe sheet 22 may be separated into individual integrated circuit packages, such as the integrated circuit package 120,
The bottoms of the tabs 50 (e.g., the bottoms 156, 158, and 162 of the tabs 56, 58, and 62, respectively) facilitate later solder connection of the integrated circuit package 120 to corresponding pads on an underlying printed circuit board or the like. As can be appreciated, once the integrated circuit package 120 has been attached, for example, to an underlying printed circuit board, a distinct electrical pathway will be established from each pad on the integrated circuit device 110 (e.g., one of the integrated circuit device pads 112, 114, 116, 118,
As can be appreciated, the package and method described herein provide many advantages. The present method, for example, uses a relatively inexpensive tape 90 to hold the shunt 100 in place within the leadframe. Other applications use rivets to hold the shunt in place or tape which ultimately becomes encapsulated and incorporated in the finished device to secure the shunt on the leadframe. This type of tape is expensive as it must be die cut to a picture frame form. Further, the use of tape in this manner provides additional interfaces where later delamination might occur within the finished package. The use of rivets is disadvantageous for several reasons. Riveted attachments, for example, tend to take up more space—particularly since the rivets generally require tie straps extending from the leadframe. Further, a more complex leadframe and shunt result when rivets are used. Most significantly, the use of rivets negatively impacts the hermeticity of the overall package since additional paths for moisture ingress are created (i.e., the tie straps to which the rivets attach, one located at each end of the shunt). In the present process using the tape 90, the shunt 100 is fully encapsulated on five sides with only the bottom surface 101 exposed.
Another advantage provided by the package and method described herein is that, since the tape 90 is removed after encapsulation, it does not become part of the final package and, thus, does not pose a risk of causing delamination between the mold compound and the tape. The present package and method also allow customization of the shunt 100; the shunt, for example, can be formed from a different alloy than the leadframe 40 and/or the shunt 100 can be selectively plated with any desired material without the need to also plate the leadframe 40. Further, the size and shape of the shunt 100 can be easily changed with no need to change the configuration of the leadframe 40 (as long as the shunt 100 fits in the leadframe open space 80).
The foregoing description of specific embodiments has been presented for purposes of illustration and description. The specific embodiments described are not intended to be exhaustive or to suggest a constraint to the precise forms disclosed, and many modifications and variations are possible in light of the above teaching. The illustrated embodiments were chosen and described in order to best explain principles and practical application, to thereby enable others skilled in the art to best utilize the various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure herein be defined only by the claims appended hereto and their equivalents, except as limited by the prior art.
Claims
1. A method of manufacturing an integrated circuit package, comprising:
- providing at least one lead frame having an upper surface, an oppositely disposed lower surface and at least one open space extending through the at least one leadframe from said upper surface to said lower surface;
- attaching an integrated circuit device to a portion of said upper surface of said at least one leadframe;
- applying tape to the lower surface of said at least one leadframe;
- placing a shunt at least partially in said open space such that it is in contact with said tape;
- electrically connecting said integrated circuit device to said shunt and to said at least one leadframe;
- encompassing at least portions of said at least one leadframe, said integrated circuit device and said shunt with a molding material; and
- thereafter, removing said tape from said lower surface of said at least one leadframe.
2. The method of claim 1 and further wherein:
- said shunt is formed from an alloy comprising copper, manganese, and nickel.
3. The method of claim 1 and further wherein:
- said applying tape to the lower surface of said at least one leadframe comprises applying a pressure sensitive adhesive tape to said lower surface of said at least one leadframe.
4. The method of claim 1 and further wherein:
- said applying tape to the lower surface of said at least one leadframe comprises applying a thermoplastic tape to said lower surface of said at least one leadframe.
5. The method of claim 1 and further wherein:
- said shunt is not in contact with any portion of said at least one leadframe.
6. The method of claim 1 and further wherein:
- said placing a shunt at least partially in said open space such that it is in contact with said tape comprises fully supporting said shunt on said tape.
7. The method of claim 1 and further wherein:
- said providing at least one lead frame comprises providing a plurality of leadframes interconnected in a sheet; and
- said applying tape to the lower surface of said at least one leadframe comprises applying tape to lower surfaces of said plurality of leadframes.
8. An integrated circuit package comprising:
- a lead frame having an upper surface, an oppositely disposed lower surface and at least one opening extending through the leadframe from said upper surface to said lower surface;
- an integrated circuit device attached to a portion of said upper surface of said leadframe;
- a shunt positioned at least partially in said opening; and
- wherein, said shunt is not in contact with any portion of said leadframe.
9. The integrated circuit package of claim 8 and further wherein:
- said integrated circuit device is electrically connected to said shunt and to said leadframe.
10. The integrated circuit device of claim 9 and further wherein:
- said integrated circuit device is electrically connected to said shunt and to said leadframe by wire bonds.
11. The integrated circuit package of claim 8 and further comprising:
- a molding material encompassing at least portions of said leadframe, said integrated circuit device and said shunt.
12. The integrated circuit package of claim 8 and further wherein:
- said shunt is formed from an alloy comprising copper, manganese, and nickel.
13. A method of manufacturing an integrated circuit package, comprising:
- providing at least one lead frame having an upper surface, an oppositely disposed lower surface and at least one open space extending through the at least one leadframe from said upper surface to said lower surface;
- attaching an integrated circuit device to a portion of said upper surface of said at least one leadframe;
- placing a shunt at least partially in said open space such that it is not in contact with any portion of said at least one leadframe;
- electrically connecting said integrated circuit device to said shunt and to said at least one leadframe; and
- while maintaining said shunt not in contact with any portion of said at least one leadframe, encompassing at least portions of said at least one leadframe, said integrated circuit device and said shunt with a molding material.
14. The method of claim 13 and further comprising:
- applying tape to the lower surface of said at least one leadframe prior to said electrically connecting said integrated circuit device to said shunt and to said at least one leadframe; and
- wherein, said placing a shunt at least partially in said open space such that it is not in contact with any portion of said at least one leadframe comprises supporting said shunt on said tape.
15. The method of claim 14 and further comprising:
- removing said tape from said lower surface of said at least one leadframe after said encompassing at least portions of said at least one leadframe, said integrated circuit device and said shunt with a molding material.
16. The method of claim 13 and further wherein:
- said shunt is formed from an alloy comprising copper, manganese, and nickel.
17. The method of claim 14 and further wherein:
- said applying tape to the lower surface of said at least one leadframe comprises applying a pressure sensitive adhesive tape to said lower surface of said at least one leadframe.
18. The method of claim 14 and further wherein:
- said applying tape to the lower surface of said at least one leadframe comprises applying a thermoplastic tape to said lower surface of said at least one leadframe.
19. The method of claim 14 and further wherein:
- said supporting said shunt on said tape comprises supporting said shunt only with said tape.
20. The method of claim 13 and further wherein:
- said providing at least one lead frame comprises providing a plurality of leadframes interconnected in a sheet.
Type: Application
Filed: Oct 4, 2012
Publication Date: Apr 10, 2014
Applicant: TEXAS INSTRUMENTS INCORPORATED (Dallas, TX)
Inventors: Donald Charles Abbott (Norton, MA), Ubol Annie Udompanyavit (Dallas, TX), Brian Eugene Parks (Sherman, TX)
Application Number: 13/644,647
International Classification: H01L 23/495 (20060101); H01L 21/56 (20060101);