In
In
While the conventional process flow just described is adequate to form a semiconductor device package, it may offer certain drawbacks. In particular, the partial etching step shown in
Accordingly, there is a need in the art for a process for forming a semiconductor device package which avoids the need for a partial etching step.
Embodiments of the present invention relate to the use of stamping to form features on a lead frame of a semiconductor device package. The lead frame can include a plurality of terminals with stamped features at edges of the terminals. The stamped features can include flattened portions that are thinner than other portions of the terminals and extend laterally beyond the edges of the terminals. Such stamped features can help mechanically interlock the terminals with the plastic molding of the package body. The stamped features can include patterns and/or other features that may further increase interlocking between the terminals and the package body.
According to one embodiment, a semiconductor device package is provided. The semiconductor device package includes a die and a plurality of terminals configured to be in electrical communication with the die through one or more bond structures. Each of the plurality of terminals includes a first portion extruding from the device package and a second portion disposed outside a plane of the first portion and having stamped feature at an edge of the second portion. The stamped feature extends laterally beyond the edge of the second portion and is thinner than the edge of the second portion. The semiconductor device package further includes a package body encapsulating the die, the one or more bond structures, and the second portion of each of the plurality of terminals.
According to another embodiment, a method for manufacturing a semiconductor device package is provided. The method includes providing a die, providing a lead frame with a plurality of terminals configured to be in electrical communication with the die through one or more bond structures, and stamping the plurality of terminals to form, for each of the terminals (1) a first portion of the terminal that is displaced along a certain dimension in relation to a second portion of the terminal, the first portion of the terminal being electrically connected with the second portion of the terminal via a connecting portion, and (2) a stamped feature at an edge of the first portion of the terminal. The stamped feature extends laterally beyond the edge of the first portion of the terminal and is thinner than the edge of the first portion of the terminal. The method further includes encapsulating the die, the one or more bond structures, and the first portion of each of the plurality of terminals in a package body.
According to yet another embodiment an integrated circuit package is provided. The integrated circuit package includes a die having a plurality of electrical contacts disposed along a surface of the die, and a plurality of terminals configured to be in electrical communication with the die. Each of the plurality of terminals includes one or more bond structures electrically connecting the terminal with one or more of the plurality of electrical contacts, a first portion extruding from the device package, and a second portion disposed outside a plane of the first portion and having stamped feature at an edge of the second portion. The stamped feature extends laterally beyond a part of the second portion that is not stamped and is thinner than the part of the second portion that is not stamped. The integrated circuit package also includes a package body encapsulating the die, the one or more bond structures, and the second portion of each of the plurality of terminals.
These and other embodiments of the present invention, as well as its features and some potential advantages are described in more detail in conjunction with the text below and attached figures.
FIGS. 2CA-2CC show end views of various complex cross-sectional profiles that may be imparted by stamping according to embodiments of the present invention.
Embodiments of the present invention relate to the formation of semiconductor device packages utilizing stamping. In one embodiment, portions of the lead frame such as pins are moved out of the horizontal plane of a diepad by stamping. In certain embodiments, the pins of a package may be imbued with a chamfered or other complex cross-sectional profile by a stamping process. Other techniques, employed alone or in combination, may facilitate fabrication of a package by stamping.
In
In
Also defined during the punching step of
Specifically,
Another lead frame feature shown in
According to certain embodiments, the stamping process may raise the pin portions 208a to a height Z above the surface of the diepad 204, where Z corresponds approximately to an expected thickness of a die supported on the diepad, and a conducting adhesive material between the die and the diepad.
Still another feature which may be imparted to a lead frame during the stamping of
In the particular embodiment of FIGS. 2CA-CB, the middle pin portion 208b exhibits a chamfered profile, with sides positioned at an angle relative to the vertical disposition of the sides of the other portions of the pin. In this embodiment, the complex cross-sectional profiles imparted to the lead frame by stamping according to embodiments of the present invention, enhances mechanical interlocking of the pins within the plastic body of the package. In addition, the stamped cross-sections allow the pins to offer a larger surface area to the surrounding molding material, thereby further enhancing mechanical interlocking between lead frame and package body. Moreover, the complex stamped cross-sectional profiles may allow the pins to better relieve physical stress during the subsequent singulation step, thus avoiding damage at the interface between the pin and the plastic package body.
While FIG. 2CA shows the complex cross-sectional profile as being a chamfer, this is not required by the present invention. In other embodiments, the cross-sectional profile imparted by stamping could be hour-glass shaped, T-shaped, H-shaped, angled or curved concave or convex, or saw tooth shaped, as shown in FIG. 2CC.
The various features formed by stamping in
Specifically, electroplated material 222 may be formed on the die attach portion 204b of the diepad 204 that is expected to receive the die. Where the die to be supported by the diepad has an electrical contact on its lower surface (such as the drain of a MOSFET), the electroplated material 222 will likely contain silver (Ag).
Another location of electroplated material is at an end of the elevated portion 208a of the pin 208 proximate to the diepad 204. As discussed in detail below, these electroplated regions are expected to receive the electrically conducting bond wire, bond ribbon, or bond clip from the top surface of the supported die.
The composition of the electroplated material 222 may be dictated by the composition of the bond wire/ribbon/clip with which the electroplated material will be in contact. The following TABLE provides a listing of electroplated materials under different conditions.
During the package singulation process shown in
The package singulation process in
While the particular embodiment shown above depicts fabrication of a package housing a single die, the present invention is not limited to such a package. Alternative embodiments in accordance with the present invention could be used to form packages housing two, three, or even larger numbers of die.
In a second step 304 of process 300, holes are punched completely through to remove material from the metal role and thereby define the pattern of the diepad and pins.
In a third step 306, the patterned metal roll is subjected to one or more stamping processes to create features on the pin and diepad portions of the package. As discussed in detail above, examples of such features include indentations on the underside of the diepad, pin portions exhibiting a chamfered cross-sectional profile, and raised pin portions.
In a fourth step 308, portions of the lead frame may optionally be electroplated with an appropriate metal. Examples of such electroplated regions include the die attach area, and the raised portions of the pins that are expected to receive an end of a bond structure such as a wire, ribbon, or clip having its other end in contact with the die.
In a fifth step 310, the stamped lead frame is exposed to an oxidizing ambient. A result of this exposure to the oxidizing ambient is the formation of brown oxide on all exposed portions of the lead frame surface. As discussed previously, this oxidation may desirably lead to the formation of an oxide guard band circumscribing the die attach area.
In a sixth step 312, brown oxide on the bottom surface of the pins and diepad may be removed. In certain embodiments, this oxide removal may be accomplished by physically lapping the bottom of the lead frame. In other embodiments, this oxide removal may be accomplished by exposure to a chemical etching environment.
The oxide removal step may occur immediately following the oxidation step, as indicated in
In a seventh step 314, the die is attached to the die attach area. In certain embodiments, this die attach step may include prior application of an electrically conducting adhesive material to the die attach area of the diepad. Alternative embodiments may utilize a die having its back side already coated with the electrically conducting adhesive material.
In an eighth step 316, the appropriate bonding structure(s) are attached between the surface of the die and the appropriate pin, which may be electroplated. As discussed above, the bond structure may be a conducting clip, wire, or ribbon.
In a ninth step 318, the die, bond structure, and portions of the pins and diepad are encapsulated within a plastic molding material to form the body of the package.
During this step, the diepad and pins remain fixed to the surrounding metal matrix of the original metal roll.
In a tenth step 320, the individual package is singulated from the surrounding metal matrix by punching through the metal. During this singulation process, a chamfered or other complex cross-sectional profile imparted to the pins by stamping, may enhance mechanical interlocking of the pins within the package body, and allow the pins to relieve physical stress resulting from the shearing of the metal.
In additional steps (not shown), the package may be attached to an underlying PC board utilizing solder. The previous removal of brown oxide by lapping may facilitate the performance of this step.
The process described above represents only one particular embodiment of the present invention. Other embodiments may omit certain steps, include additional steps, or perform the steps in a specific order other than that indicated.
For example, the selective electroplating step is not required, and according to certain embodiments the bonding structure may be in contact with the bare metal of the roll rather than an electroplated feature. Moreover, the use of a bonding clip is not required by the present invention and certain embodiments could employ only bonding ribbons or wires to establish electrical connection with contact(s) on the top of the die.
Embodiments in accordance with the present invention offer a number of possible advantages over conventional package fabrication processes. In particular, by avoiding the need for complex and difficult-to-achieve steps of forming raised/recessed features on the lead frame by marking and partial etching, embodiments in accordance with the present invention offer cost savings.
Comparison of
However, various other aspects of processes according to embodiments of the present invention may serve to offset any smaller size of the diepad and die. For example, the formation of the brown oxide guard band circumscribing the die attach area, effectively constrains the flow of the electrically conducting adhesive material during the die attach process. This in turn allows reduction in the peripheral area of the diepad that must be allocated to avoid the flowed material from undesirably affecting regions outside the die attach area.
Moreover, certain embodiments involve the use of clips instead of bond wires. Such use of a bond clip may allow for a reduced resistance electrical connection between the die contacts and the surrounding pins. This may in turn permit the use of a smaller die having performance comparable to a larger one.
Similarly, the use of selective electroplating may also offer a reduced resistance electrical connection between the die contacts and the surrounding pins. Again, this offers the possibility of a smaller die exhibiting performance comparable to a larger die.
The above figures present an exemplary embodiment only, and the present invention is not limited by this particular embodiment. For example, while the above figures show a diepad having indented features formed by stamping, this is not required by the present invention. According to other embodiments, a diepad could have raised features formed by stamping, such as raised features on a periphery of the diepad.
Moreover, while the specific embodiment shown above includes pin portions proximate to the diepad that are elevated by stamping, the present invention is not limited to this approach. In accordance with alternative embodiments, portions of the pins distal from the diepad could be inclined downward by stamping, thereby offering an embodiment wherein the bottom of the diepad is not exposed following encapsulation of the package body.
In addition, while the above figures describe an embodiment of a package configured to house a single die, this is not required by the present invention. Alternative embodiments of packages according to the present invention can be configured to house two or more die.
For example,
The lead frame 403 of the particular embodiment of
Specifically, the stamped end frame 403 of package 420 comprises three diepads 404, 407, and 409, respectively supporting first MOSFET die 412, second MOSFET die 455, and integrated circuit (IC) die 460. Diepad 404 is the largest of the three, having an elongated die attach area 404a configured to support MOSFET die 412.
The pins of the package offer contact with three discrete portions of the first MOSFET die 412. Specifically, ganged pin nos. 21-27 are in low resistance communication with the source contact located on the top surface of the die 412, through clips 450. Pins 16, 20, and 28-31 are integral with the diepad 404, and hence offer a low resistance electrical communication with the drain of the MOSFET through a contact in the bottom surface of the die. The gate of the MOSFET is in electrical communication with a contact of the integrated circuit (IC) die 409 through bond wire 452.
Similarly, the pins of the package 420 offer contact with three discrete portions of the second MOSFET die 455. Specifically, ganged pin nos. 34-36 are in low resistance communication with the source contact located on the top surface of the die 455, through bonding clips 450. Pins 1-2, 4, and 33 are integral with the diepad 407, and hence offer a low resistance electrical communication with the drain of the MOSFET through a contact in the bottom surface of the die. The gate of the MOSFET is in electrical communication with pin 3 through bond wire 452.
Unlike the MOSFET die just described, the IC die 460 features a large number of contacts on its top surface. These various contacts are in electrical communication with the following pin nos.: 5, 7-9, 11-13, 15, and 17-18.
IC die 460 may or may not have an electrical contact in its lower surface. If it does, pins 6, 10, and 14 integral with the diepad 409 provide for low electrical resistance communication with that underside contact.
The multi-die embodiment of the QFN package 420 of
Another feature of the multi-die embodiment of the QFN package 420 of
Yet another feature of the multi-die embodiment of the QFN package 420 of
As previously indicated, the multi-die embodiment of the QFN package 420 includes an IC die which may or may not have an electrical contact on its back side. Such an IC die would not be expected to generate as much heat as other dies such as MOSFETs. Accordingly, an epoxy die attach film may be used to adhere the IC die to the diepad. Such an epoxy film may be formed as a solid, and would not be expected to flow or spread during the die attach step. Accordingly, for embodiments of the present invention where a package is fabricated housing only an IC die, formation of a brown oxide guard band followed by lapping, may not be necessary.
While the embodiments described above illustrate the use of stamping to impart a chamfered cross-sectional profile to pin portions, this particular cross-sectional profile is not required by embodiments of the present invention. According to alternative embodiments, stamping could imbue pins with other cross-sectional profiles and remain with the scope of the invention. Examples of such other cross-sectional profiles include but are not limited to hourglass shaped, angled or curved concave, angled or curved convex, or saw tooth.
During conventional package fabrication processes, the diepad may be secured to the surrounding metal of the roll utilizing tie-bar structures. These conventional tie-bar structures stabilize the diepad during die attach, and encapsulation steps, and are then severed during the package singulation.
One advantage of embodiments in accordance with the present invention, is the dispensing of the need for a tie-bar structure. Specifically, the embodiment of
The absence of tie-bars offer a number of advantages. One advantage is having more area in the corners of a package to place more pins. Another advantage is that there is no exposed part of tie bars on a surface of a package.
While the embodiment of
The embodiment of
Types of features other than those explicitly described above, can be formed on a lead frame by coining according to alternative embodiments of the present invention. For example,
The embodiment of
In addition, the holes 602 serve to isolate and preserve rim/runway area 606 (from the die to the edge of the die-pad) for down bonding. In particular the presence of the holes serves to contain unwanted bleeding or overflow of die attach material during the die attach step. For example, in one embodiment where the diepad has an overall width of 5.1 mm, the hole may have a width of 0.2 mm, and may be separated from the diepad edge by a distance of 0.2 mm forming the down bond runway.
Lead frames according to embodiments of the present invention may combine multiple features that are formed by coining. For example, the lead frame shown in
As a further example of a lead frame having multiple coined features,
Specifically, the lead frame 700 of the embodiments of
According to the embodiment illustrated in
The lead frame can also include a second portion 930 internal to the device package that includes stamped features 932. These stamped features 932, which can be located at the edges of the terminals, can be formed by stamping and/or coining the lead frame. The stamping and/or coining can flatten portions of the lead frame, causing the stamped features 932 to be thinner than the other edges of the terminals that are not stamped and/or coined, and extend laterally beyond the edges of the terminals that are not stamped and/or coined. Such stamped features 932 can help the terminals interlock with the package body and hold them in place. To this end, the stamped features 932 also can include patterns and/or profiles (including complex cross-sectional profiles) that may further help the terminals interlock with the package body.
The lead frame can also include a third portion 910 internal to the device package that includes a plurality of fingers 912 configured to support and/or provide electrical connection to the die 900. The configuration of the fingers (e.g., size, length, number, etc.) can vary, depending on desired functionality. For example, the configuration of
The fingers 912 and/or contacts 940 can include bond structures to help ensure a good electrical connection between the fingers 912 and contacts 940. Such bond structures can include, for example, a land pattern, ball grid array (BGA), gold and/or copper pillar, and the like. A person of ordinary skill in the art will recognize numerous alterations, substitutions, and variations.
The lead frame of the device package 1015 further illustrates how embodiments can include a connecting portion 1050 that includes stamped feature that connects the first portion 1020 to the second portion 1030. (Note that, for clarity, only one of the two connecting portions 1050 of
As with other embodiments provided herein, the device package 1015 further illustrates how fingers 1012 can be connected to the contacts of the die 1000 via bond structures 1035. Again, bond structures can include one or more of a variety of structures configured to help ensure a good electrical connection between the fingers 1012 and contacts of the die 1000.
The method further includes stamping the plurality of terminals to form a first portion displaced along a certain dimension in relation to a second portion, and a stamped feature at an edge of the first portion (1230). As described above, the first portion of the terminals can be stamped such that the first portion is raised above a plane of a second portion (i.e., the portion that protrudes from the package body). The first and second portions of the terminal can be connected via a connecting portion. As explained above, the stamped feature at the edge of the first portion can extend laterally beyond an edge of the first portion of the terminal and is thinner than the edge of the first portion of the terminal. Additionally, as described elsewhere herein, the first, second, and/or connecting portions may include other stamped features to help the terminals mechanically interlock with a package body. Finally, the method includes encapsulating the die, the one or more bond structures, and the first portion of each of the plurality of terminals in a package body (1240). The package body can comprise one or more insulating materials, such as plastic.
It should be appreciated that the specific steps illustrated in
It can be noted that, while many embodiments described in reference to
While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention which is defined by the appended claims.
This application is a continuation-in-part of U.S. patent application Ser. No. 12/903,626, filed Oct. 13, 2010, which is a divisional application of U.S. patent application Ser. No. 12/191,527, filed Aug. 14, 2008, which issued as U.S. Pat. No. 7,838,339 on Nov. 23, 2010, which claims priority to U.S. Provisional Patent Application No. 61/042,602, filed Apr. 4, 2008, all of which are incorporated by reference in their entirety herein for all purposes. The following regular U.S. patent applications (including this one) are being filed concurrently, and the entire disclosure of the other applications are incorporated by reference into this application for all purposes: application Ser. No. ______, filed ______, entitled “SEMICONDUCTOR DEVICE PACKAGE HAVING FEATURES FORMED BY STAMPING” (Attorney Docket No. 86762-826617 (006030US)); andapplication Ser. No. ______, filed ______, entitled “SEMICONDUCTOR DEVICE PACKAGE HAVING CONFIGURABLE LEAD FRAME FINGERS” (Attorney Docket No. 86762-826616 (006040US)).
Number | Date | Country | |
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61042602 | Apr 2008 | US |
Number | Date | Country | |
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Parent | 12191527 | Aug 2008 | US |
Child | 12903626 | US |
Number | Date | Country | |
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Parent | 12903626 | Oct 2010 | US |
Child | 13348308 | US |