Digital systems often include one or more integrated circuits (also referred to as “chips” or “dies”) that are coupled to a printed circuit board, using one or more packages. Typically, these packages are used to electrically and mechanically connect the integrated circuit to the printed circuit board.
One type of package is a flat, no-lead package. Unfortunately, existing flat, no-lead packages are not entirely satisfactory due to the coefficient of thermal expansion mismatch between the components of the flat, no-lead package and the integrated circuit. This mismatch can cause significant stress on the integrated circuit and deformation of the integrated circuit.
The present invention is directed to a package that electrically connects an integrated circuit to a printed circuit board. In one embodiment, the package includes a first frame and a package body that encases at least a portion of the first frame and the integrated circuit. The first frame includes a first mounting region that is electrically connected to the printed circuit board, and a first cantilevering region that cantilevers away from the first mounting region. Moreover, the package can include a first connector that connects the integrated circuit to the first cantilevering region so that the integrated circuit cantilevers away from the first frame. With this design, the integrated circuit is supported in a fashion that inhibits significant deformation of the integrated circuit.
Additionally, the package can include (i) a second frame having a second cantilevering region, and a second mounting region; (ii) a third frame having a third cantilevering region, and a third mounting region; and (iv) a fourth frame having a fourth cantilevering region, and a fourth mounting region. In this embodiment, the frames are spaced apart, encased by the package body, and support the integrated circuit in a fashion that inhibits significant deformation of the integrated circuit.
In one embodiment, each frame is made of electrically conductive material, and the frames independently electrically connect the integrated circuit to the printed circuit board.
In another embodiment, the package includes (i) one or more spaced apart frames, each having a mounting region that is connected to the printed circuit board, and a cantilevering region that engages the integrated circuit to retain the integrated circuit cantilevering away from the mounting region; and (ii) a package body that encases at least a portion of the one or more frame and the integrated circuit, the package body being made of an electrically isolating material.
In this embodiment, the package can include one or more separate connector wires that electrically connect the integrated circuit to the printed circuit board.
The present invention is also directed to an assembly that includes an integrated circuit and the package provided herein. Additionally, the assembly can include a printed circuit board that is electrically connected to the integrated circuit with the package.
In yet another embodiment, the present invention is directed to a method for electrically connecting an integrated circuit to a printed circuit board. In this embodiment, the method includes the steps of: (i) supporting the integrated circuit with a first frame that includes a first mounting region that engages the printed circuit board, and a first cantilevering region that cantilevers away from the first mounting region, the first cantilevering region engaging the integrated circuit to support the integrated circuit; and (ii) encasing at least a portion of the first frame and the integrated circuit with a package body that is made of an electrically isolating material.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
As an overview, the package 16 is uniquely designed to support the integrated circuit 14 in a fashion that inhibits significant deformation of the integrated circuit 14.
In one embodiment, the printed circuit board 12 is a flat board that is made of non-conducting material (e.g. an insulating material), and a plurality of predefined conductive metal pathways (not shown) that are printed on the surface of the board. In one embodiment, the printed circuit board 12 also includes a plurality of spaced apart, electrically conductive board contacts 12A (illustrated in phantom and sometimes referred to as board pads) that are electrically connected to the one or more integrated circuits 14 with one or more packages 16. In
Additionally, in
Each integrated circuit 14 (only one is illustrated in
Additionally, in
In one non-exclusive embodiment, the integrated circuit 14 can include a parylene side 14C on the top of the circuit body 14A, and a back metal EMI shield 14D on the bottom of the circuit body 14A. The parylene side 14C includes a variety of chemical vapor deposited on the circuit body 14A as a moisture and dielectric barrier. It should be noted that the integrated circuit 14 can be designed without one or both of the parylene side 14C and the EMI shield 14D.
The package 16 electrically and independently connects each of the chip contacts 14B on the integrated circuit 14 to a corresponding board contact 12A on the printed circuit board 12. Additionally, the package 16 can also fixedly secure the integrated circuit 14 to the printed circuit board 12 and provide mechanical support to the integrated circuit 14. The design of the package 16 can vary. For example, in
The size and shape of the package 16 will vary according to the size and shape of the integrated circuit 14. As non-exclusive examples, the package 16 can be generally rectangular in shape and can have (i) a height of between approximately 0.55 to 0.85 millimeters; (ii) a width of between approximately 1.62 to 5 millimeters; and (iii) a length of between approximately 2.5 to 7 millimeters. Alternatively, the package 16 can have dimensions different than that provided herein.
In
In one embodiment, each frame 18-28 is electrically conductive and can include a mounting region 34A and a cantilevering region 36A that cantilevers away from the mounting region 34A. In this embodiment, for each frame 18-28, (i) the mounting region 34A includes a mounting pad 34B that is electrically connected to one of the board contacts 12A of the printed circuit board 12, and (ii) the cantilevering region 36A includes a cantilevering pad 36B that is electrically connected to one of the chip contacts 14B of the integrated circuit 14. For example, each frame 18-28 can be made of copper or another electrically conductive material. In this embodiment, the mounting region 34A is rigid and the cantilevering region 36A is flexible, and the regions 34A, 34B can be made as a unitary structure. Further, in this embodiment, the cantilevering regions 36A of of the frames 18-28 extend inward towards the integrated circuit 14.
In
The package body 30 encases, encircles and encloses the integrated circuit 14. Additionally, the package body 30 encases, encircles and encloses the majority of each frame 18-28. With this design, the package body 30 fixedly retains the frames 18-28 and the integrated circuit 14. Further, the package body 30 electrically isolates the frames 16-28 from each other. For example, the package body can be made of an electrically non-conductive (isolating) mold compound that is molded around the frames 18-28 and integrated circuit 14 after the frames 18-28 have been connected and fixedly secured to the integrated circuit 14. Suitable materials for the package body 30 include, but are not limited to, G700, and G770. In one non-exclusive embodiment, the package body 30 is generally rectangular shaped.
The plurality of electrical connectors 32A-32F mechanically and electrically connect the frames 18-28 to the chip contacts 14B of the integrated circuit 14. With this design, the number of electrical connectors 32A-32F is equal to the number of frames 18-28. Thus, in
For example, each connector 32A-32F can be an electrically conductive, gold stud, solder, epoxy, or copper pillar bump that extends between the respective cantilevering pad and the respective chip contact. Each connector 32A-32F can include Anisotropic conductive epoxy, or Solder paste e.g. SnIn, SnSb, or SnAgCu paste but not limited to these materials of electrical connection.
With this design, (i) there is very small mechanical connection area between frames 18, 28 and the integrated circuit 14, and (ii) the connectors 32A-32F allow for relative movement between the frames 18, 28 and the integrated circuit 14. For example, in alternative, non-exclusive embodiments, the connection area between each frame 18-28 and the integrated circuit 14 can be less than approximately 500 um sq to 150000 sq um. As a result thereof, as the temperature of the assembly 10 changes, the amount of stress on the integrated circuit 14 and the amount of deformation on the integrated circuit caused by the different coefficients of thermal expansion of the frames 18, 28 and the integrated circuit 14 will be less.
It should be noted that the connection area between the first frame 18 and the integrated circuit 14 is relatively small because of the relatively small size of the first connector 32A. As a result thereof, as the temperature changes, the amount of stress on the integrated circuit 14 and the amount of deformation on the integrated circuit 14 caused by the different coefficients of thermal expansion of the frame 18 and the integrated circuit 14 will be less.
The design of each frame 18 (only the first frame is illustrated in
As provided herein, in one embodiment, the first frame 18 includes the mounting region 34A and the cantilevering region 36A that are made of a unitary, electrically conductive material. In this embodiment, the mounting region 34A is generally rectangular block shape and the bottom of the mounting region 34A defines the generally flat mounting pad 34B that is electrically connected to one of the board contacts 12A. In one non-exclusive example, the mounting region 34A has (i) a width 34C (along the X axis) of between approximately 200 um and 350 um; (ii) a height 34D (along the Z axis) of between approximately 75 um and 200 um; and (iii) a length 34E (along the Y axis) of between approximately 300 um and 500 um.
The cantilevering region 36A is resilient, flexible and cantilevers at an angle away from the mounting region 34A. This design allows the cantilevering region 36A to deform slightly to reduce the stress applied to the integrated circuit 14 caused by temperature changes and the differences in coefficients of thermal expansions between the frames 18 and the integrated circuit 14.
In one embodiment, the cantilevering region 36A can be divided into three, relatively thin, rectangular shaped segments, namely a first cantilevering segment 36C, a second cantilevering segment 36D, and a third cantilevering segment 36E. In this embodiment, (i) the first cantilevering segment 36C is connected to and cantilevers generally horizontally away from the top of the mounting region 34A; (ii) the second cantilevering segment 36D (sometimes referred to as “an angled segment”) is connected to and cantilevers at an angle 38 (relative to horizontal, the mounting pad 34B, the top and bottom of the integrated circuit 14, and the top of the circuit board 12) away from a distal end of the first cantilevering segment 36, and (iii) the third cantilevering segment 36E is connected to and cantilevers generally horizontally away from a distal end of the second cantilevering segment 36D. With this design, a portion of the cantilevering region 36A cantilevers at the angle 38 away from the mounting region 34A.
Further, in this embodiment, the bottom of the cantilevering segment 36E defines the cantilevering pad 36B. With the present design, in certain embodiments, the cantilevering pad 36B is substantially parallel to and spaced apart (displaced) along the Z axis from the mounting region 34A.
The size of the angle 38 can be varied to suit the design of the integrated circuit 14. As a non-exclusive example, to achieve the same form factor for a package 16, a thicker integrated circuit 14 may require a steeper angle 38 than a thinner integrated circuit 14. Alternatively, a mounting on the bottom instead of the top of the integrated circuit 14 can require a less steep angle 38 to maintain the same form factor. In alternative, non-exclusive examples, the angle 38 can be between approximately 30 and 60 degrees, 40 and 50 degrees, 42 and 48 degrees, or 44 and 46 degrees. Alternatively, other angles 38 are possible.
In one non-exclusive example, (i) the first cantilevering segment 36C has a width (along the X axis) of between approximately 200 um and 350 um, a thickness (along the Z axis) of between approximately 50 um and 150 um, and a length (along the Y axis) of between approximately 50 um and 350 um; (ii) the second cantilevering segment 36D has a width (along the X axis) of between approximately 200 um and 300 um, a thickness of between approximately 50 um and 150 um, and (iii) a length of between approximately 50 and 350 um; and (iii) the third cantilevering segment 36E has a width (along the X axis) of between approximately 200 um and 300 um, a thickness of between approximately 50 um and 150 um, and (iii) a length of between approximately 50 and 350 um. Alternatively, other dimensions are possible.
Also, as provided above, in certain embodiments, the integrated circuit 14 is fully encased and completely enclosed with the package body 30. As a result thereof, the package body 30 includes an upper portion 30A that is positioned above the integrated circuit 14, and a lower portion 30B that is positioned below the package body 30. In certain embodiments, the sizes of the portions 30A, 30B are designed to minimize the deformation to the integrated circuit 14 caused by the different coefficients of thermal expansion of the package body 30 materials, frame 26, and the integrated circuit 14. For example, the size of the portions 30A, 30B can be designed so that each portion 30A, 30B imparts an approximately equal in magnitude force on the integrated circuit 14 during thermal changes. For example, the package body 30 can be designed so that the integrated circuit 14 is positioned approximately near a center of the package body 30. Stated in another fashion, in one embodiment, the integrated circuit 14 is approximately centered in the middle of the package body 30, with the upper portion 30A and the lower portion 30B being approximately equal in size.
The frames 218-228 mechanically and electrically connect the integrated circuit 214 to the printed circuit board 212. In
In this embodiment, each frame 218-228 is again electrically conductive and can include the mounting region 234A and the cantilevering region 236A that cantilevers away from the mounting region 234A. Again in this embodiment, the mounting region 234A is rigid and the cantilevering region 236A is flexible, and the regions 234A, 234B can be made as a unitary structure. Further, in this embodiment, the cantilevering regions 236A of the frames 218-228 extend inward towards the integrated circuit 214 to support the circuit 214 from the bottom of the circuit 214.
More specifically, in this embodiment, for each frame 218-228, the mounting region 234A includes a mounting pad 234B that is electrically connected to one of the board contacts 212A of the printed circuit board 212. However, in this embodiment, the cantilevering region 236A of each frame 218, 220 is positioned below the integrated circuit 214 to flexibly support the integrated circuit 214. In certain embodiments, a retainer 237 is used to secure the cantilevering pad 236B of the cantilevering region 236A to the bottom of the integrated circuit 214. As non-exclusive examples, the retainer 237 can be a non-conductive paste, epoxy, an adhesive, or film material.
Further, in this embodiment, (i) the first connector 232A is a wire that extends between the integrated circuit 214 and the mounting region 234A of the first frame 218, (ii) the second connector 232B is a wire that extends between the integrated circuit 214 and the mounting region 234A of the second frame 220; (iii) the third connector 232C is a wire that extends between the integrated circuit 214 and the mounting region 234A of the third frame 222, (iv) the fourth connector 232D is a wire that extends between the integrated circuit 214 and the mounting region 234A of the fourth frame 224; (v) the fifth connector 232E is a wire that extends between the integrated circuit 214 and the mounting region 234A of the fifth frame 226, and (vi) the sixth connector 232F is a wire that extends between the integrated circuit 214 and the mounting region 234A of the sixth frame 228. In this a separate frame 218-228 is used for each wire connector 232A-232F. Alternatively, for example, more than one wire connector can be used for the same frame.
It should be noted that the number of frames 218-228 and the number of wire connectors 232A-232F can be varied to suit the design of the integrated circuit 214.
Further, in this embodiment, the angle 238 of the cantilevering region 236A is smaller because of the wire bond type chip that is supported at the bottom of the chip 214. It is also appropriately designed to center the die 214 such that resulting stresses on die 214 are minimum.
While a number of exemplary aspects and embodiments of a package 16, 216 have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
The application claims priority on U.S. Provisional Application Ser. Nos. 61/676,867 filed on Jul. 27, 2012, entitled “LOW STRESS NO-LEADS PACKAGE FOR AN INTEGRATED CIRCUIT”. As far as is permitted, the contents of U.S. Provisional Application Ser. No. 61/676,867 are incorporated herein by reference.
Number | Date | Country | |
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61676867 | Jul 2012 | US |