Lead frame with retention features

Abstract

The invention relates to a lead frame with retention features. Described examples relate to an IC package (100) that includes a lead frame (102) of conductive material that includes a die attach pad (110) and lead fingers (112) spaced apart from an edge of the die attach pad. The lead frame (102) has a first surface and a second surface opposite the first surface. The IC package (100) also includes a retention feature (122) on the lead fingers (112) at the second surface. The IC package (100) further includes a die (106) at the die attach pad (110) on the first surface. The IC package (100) also further includes a molding compound (108) that encapsulates the lead frame (102) and the die (106) and extends into and / or around the retention feature (122).

Description

Technical Field

[0001] This specification relates to semiconductor packages having a lead frame with retention features adapted to receive molding compound. Background Art

[0002] Due to the trend of miniaturization of electronic products such as mobile phones, tablet computers, digital cameras, etc., semiconductor package manufacturing has shown a trend towards smaller and more densely packaged semiconductor structures and semiconductor layers. Generally, semiconductor packages are built on a lead frame formed of a conductive material. The lead frame carries signals from the die to the semiconductor package or to different chips in a dual in-line package (DIP), quad flat package (QFP), and other semiconductor packages. Summary of the Invention

[0003] A first example relates to an integrated circuit (IC) package. The IC package includes a lead frame of a conductive material, the lead frame including die attach pads and lead fingers spaced apart from the edges of the die attach pads. The lead frame has a first surface and a second surface opposite the first surface. The IC package further includes retention features at the second surface on the lead fingers. The IC package further includes a die at the first surface at the die attach pads. The IC package further includes a molding compound that encapsulates the lead frame and the die and extends into and / or around the retention features.

[0004] A second example relates to a method of forming an integrated circuit (IC). The method includes providing a lead frame of a conductive material, the lead frame including lead fingers and die attach pads separated by a distance. The lead frame has a first surface and a second surface opposite the first surface. The method further includes forming retention features in the second surface of the lead frame at the lead fingers adapted to receive molding compound. The retention features are formed by adding and / or removing material relative to the second surface.

[0005] A third example relates to a device. The device includes a sheet of a conductive material having a first surface and a second surface opposite the first surface. Fabrication features extend along at least one of the first surface and the second surface in a first direction. The sheet includes die attach pads and a plurality of lead fingers. The plurality of lead fingers are spaced apart from the die attach pads and surround the die attach pads. An arrangement of retention features is formed in at least one of the lead fingers extending in a second direction substantially perpendicular to the first direction. Brief Description of the Drawings

[0006] Figure 1 An example of a semiconductor device ready for packaging is shown.

[0007] Figure 2AAn example showing a V-shaped holding feature at the lead fingers of a semiconductor device.

[0008] Figure 2B An example showing a U-shaped holding feature at the lead fingers of a semiconductor device.

[0009] Figure 2C An example showing a through-holding feature at the lead fingers of a semiconductor device.

[0010] Figure 2D An example showing a V-shaped holding feature and a protruding holding feature at the lead fingers of a semiconductor device.

[0011] Figure 3 A flowchart showing an example method for forming a semiconductor package including a lead frame having a holding feature.

[0012] Figure 4 An example showing a conductive sheet for forming a semiconductor package including a lead frame having a holding feature.

[0013] Figure 5 Showing Figure 3 An example of the first part of the method.

[0014] Figure 6 Showing Figure 3 An example of the second part of the method.

[0015] Figure 7 Showing Figure 3 An example of the third part of the method.

[0016] Figure 8 Showing Figure 3 An example of the fourth part of the method.

[0017] Figure 9 Showing Figure 3 An example of the fifth part of the method.

[0018] Figure 10 Showing Figure 3 An example of the sixth part of the method. Detailed Description

[0019] This specification relates to forming retention features at the surface of a lead frame to help reduce delamination of the molding compound of a packaged semiconductor device. The retention features are adapted to receive the molding compound or otherwise interlock with the molding compound, and provide additional surface area for improving the adhesion of the molding compound to the lead frame. The retention features may be disposed among the manufacturing features on the surface of the lead frame. For example, the retention features are arranged to extend in a direction transverse to the direction of the manufacturing features to increase the mechanical interlock force. As described herein, the retention features may be formed in various shapes and sizes to increase adhesion by providing a mechanical interlock structure for the molding compound applied to form the semiconductor package.

[0020] Figure 1 An example of a semiconductor device 100 ready for encapsulation is shown. The semiconductor device 100 includes a lead frame 102 formed of a conductive material, such as copper, palladium, gold, silver, or other suitable conductive metal or metal alloy having similar properties. For example, the lead frame 102 is formed from a copper sheet. A bonding layer 105 bonds the die 106 to the die attachment portion of the metal contact layer 104 of the lead frame 102. For example, the bonding layer 105 is a layer of adhesive (such as an epoxy resin). The lead frame 102, the bonding layer 105, and the die 106 are at least partially encapsulated in a molding compound 108 to form the packaged semiconductor device 100, such as an integrated circuit (IC) or a system-on-chip (SOC). The molding compound 108 is formed of one or more insulating materials, such as organic resins (e.g., epoxy resins), inorganic resins, and / or other suitable materials.

[0021] The lead frame 102 defines a plane extending through the lead frame 102. In some examples, the lead frame 102 includes a die attachment pad 110 spaced apart from one or more lead fingers 112. For example, a plurality of lead fingers 112 may be disposed around the die attachment pad 110 (e.g., surrounding the die attachment pad). The die attachment pad 110 provides an electrical connection between the die 106 and the lead fingers 112. During encapsulation, the semiconductor device 100 is singulated such that the lead fingers 112 form leads that are exposed to the external environment. The leads of the singulated semiconductor device 100 enable the die 106 to be electrically coupled to one or more other electrical components external to the semiconductor device 100.

[0022] The lead fingers 112 are separated from the edge of the die attachment pad 110 by a distance in a first direction 114 and are coplanar with the plane of the lead frame 102. Although Figure 1For clarity, a single lead finger 112 is shown, but multiple lead fingers are spaced apart from and surround the die attach pad 110. The lead fingers among the multiple lead fingers are also separated from each other in one or more directions coplanar with the plane of the lead frame 102. For example, a given lead finger 112 is separated from other lead fingers in a first direction 114, and the lead finger 112 extends in a second direction 116 (e.g., into the page), which is coplanar with and substantially perpendicular to the first direction 114. The distance between the lead finger 112 and the edge of the die attach pad 110 and / or other lead fingers among the multiple lead fingers is based on the shape of the lead finger 112. As an example, the lead finger 112 has a perimeter that defines the shape of the lead finger 112. The shape of the lead finger 112 can be rectangular, chamfered rectangular, T-shaped, L-shaped, E-shaped, U-shaped, and circular, among other shapes.

[0023] The lead frame 102 and thus the die attach pad 110 and the lead fingers 112 have a first surface 118 and an opposite second surface 120. A metal contact layer 104 is formed on the first surface 118 of the die attach pad 110 of the lead frame 102. The metal contact layer 104 can extend to the perimeter of the die attach pad 110 and the lead fingers 112. The metal contact layer 104 can additionally or alternatively include an oxide layer or a laminate layer.

[0024] The arrangement of the retention features 122 is formed at the second surface 120 on the lead frame 102. The arrangement of the retention features 122 is configured to provide a structure to which the molding compound can bond to increase the adhesion therebetween and reduce delamination of the molding compound from the lead frame, particularly at the lead fingers 112. As described herein, the retention features can have different shapes and / or sizes. In Figure 1 an example, the lead frame 102 has a lead frame thickness between the first surface 118 and the second surface 120. The retention features 122 extend from the second surface 120 towards the first surface 118 to a depth less than or equal to approximately 40% of the lead frame thickness. In some examples, the retention features 122 extend from an opening in the second surface 120 through the lead frame 102 to an opening in the first surface 118. The arrangement of the retention features 122 forms an array of retention features. The spacing between adjacent pairs of retention features in a set of retention features can be approximately 25 micrometers to 40 micrometers.

[0025] The retention features 122 can be formed in groups. For example, a set of retention features includes at least one retention feature. Although the retention features 122 are shown in Figure 1 as an array of retention features, the retention features 122 can include a single retention feature. For example, the retention feature 122 can include a single retention feature that is a groove extending the length of the lead finger 112.

[0026] Because the lead fingers 112 are separated from the die attach pads 110 by a distance and are exposed to the external environment during singulation, the lead fingers 112 are more prone to delamination. Thus, in one example, the retention feature 122 is formed as a first set of retention features 124 at the second surface 120 of the lead fingers 112, but the retention feature 122 is not formed at the second surface 120 of the die attach pads 110. Alternatively or additionally, the retention feature 122 is formed as a first set of retention features 124 and a second set of retention features 126. The second set of retention features is formed on at least a portion of the second surface 120 of the die attach pads 110. In some examples, the second set of retention features 126 is formed in the second surface 120 even if the first set of retention features 124 is not formed. Whether to form the first set of retention features 124, form the second set of retention features 126, or form both the first set of retention features and the second set of retention features is based on the application of the semiconductor device 100, the location of the manufacturing features at the second surface 120 of the lead frame 102, the type of molding compound 108, and / or the formation technique used to form the retention feature 122.

[0027] The retention feature 122 is formed to be adapted to receive the molding compound 108 and increase the surface area of the second surface 120. The additional surface area provides an increased adhesion force between the lead frame 102 and the molding compound 108. Additionally, the arrangement of the manufacturing features that can be formed on the second surface 120 tends to cause delamination. For example, manufacturing features located at the edges of the lead fingers 112 create seams at the interface between the lead frame 102 and the molding compound 108. The seams have a likelihood of delaminating. Thus, the manufacturing features extend in a first direction 114, and the retention feature includes spaced-apart grooves that longitudinally extend along the lead fingers 112 at the second surface 120 in a second direction 116 (e.g., shown as extending into the page) that is substantially perpendicular to the first direction 114 of the manufacturing features. In one example, the retention feature 122 is formed to extend in the second direction 116 and is positioned among the manufacturing features. The perpendicular placement of the retention feature 122 relative to the manufacturing features provides a mechanical interlocking force that reduces delamination. Thus, the retention feature 122 reduces the number of failures caused by delamination and increases the production yield.

[0028] The placement of the manufacturing features in the first direction 114 and the placement of the retention feature in the second direction 116 are examples of the relative perpendicular placement of the manufacturing features and the retention feature 122. The retention feature 122 can be formed in any substantially perpendicular arrangement relative to the manufacturing features at the second surface 120. As described herein, the retention feature is not limited to being arranged substantially perpendicular to the manufacturing features and can be formed in almost any arrangement at the second surface 120 that is configured to promote adhesion to the molding compound.

[0029] As Figures 2A - 2DAs shown, the retention features have various cross-sectional shapes. Turning to Figure 2A , the lead finger 200 (e.g., Figure 1 the lead finger 112 of Figure 1 ) has a retention feature 202 (e.g., Figure 1 the retention feature 122 of Figure 1 ) having a V-shaped cross-section. The lead finger 200 has a first surface 204 (e.g., Figure 1 the first surface 118 of Figure 1 ) and a second surface 206 opposite the first surface 204 (e.g., Figure 1 the second surface 120 of

[0030] ). The retention feature 202 has a first sidewall 208 and a second sidewall 210. The first sidewall 208 and the second sidewall 210 extend in a longitudinal direction from the second surface 206 towards the first surface 204.

[0030] The width of the retention feature 202 defined in a transverse direction is defined by the spacing between the opposing sidewalls 208 and 210 of the respective retention feature. In some instances, the width of the retention feature 202 includes a first width 212 defined at the second surface 206 by the distance between the sidewalls. For example, the first width 212 is continuous with the second surface 206. A second width 214 is located at a first depth from the second surface 206. Thus, the first width 212 is close to the second surface 206 and the second width 214 is remote from the second surface 206. In Figure 2A , the first width 212 is greater than the second width 214.

[0031] The opposing sidewalls 208 and 210 taper. For example, the first sidewall 208 forms a first angle with the second surface 206 and the second sidewall 210 forms a second angle with the second surface 206. The first angle and the second angle may be the same or different. The first angle and / or the second angle is an angle between 30 degrees and 89 degrees. In some instances, the first sidewall 208 and the second sidewall 210 extend towards each other and converge at a point spaced from the second surface 206.

[0032] In Figure 2B , the lead finger 220 (e.g., Figure 1 the lead finger 112 of Figure 1 ) has a retention feature 222 (e.g., Figure 1 the retention feature 122 of Figure 1 ) having a U-shaped cross-section. The lead finger 222 has a first surface 224 (e.g., Figure 1 the first surface 118 of Figure 1 ) and a second surface 226 opposite the first surface 224 (e.g., Figure 1 the second surface 120 of

[0033] In Figure 2CIn [example], the lead finger 240 (e.g., Figure 1 's lead finger 112) has a retention feature 242 that extends through the lead finger 240 (e.g., Figure 1 's retention feature 122). The lead finger 240 has a first surface 244 (e.g., Figure 1 's first surface 118) and a second surface 246 opposite the first surface 244 (e.g., Figure 1 's second surface 120). The retention feature 242 has a first sidewall 248 and a second sidewall 250. The first sidewall 248 and the second sidewall 250 extend from the second surface 246 to the first surface 244 in a longitudinal direction. The first sidewall 248 and the second sidewall 250 are substantially parallel and have a width 252. In other instances, the sidewalls may be skewed relative to each other, such as narrowing or widening the distance between the sidewalls extending from the second surface 246.

[0034] As Figure 2D shown, multiple retention features are used. For example, the lead finger 260 (e.g., Figure 1 's lead finger 112) includes a first retention feature 262 (e.g., Figure 1 's retention feature 122) and a second retention feature 264 (e.g., Figure 1 's retention feature 122). The lead finger 260 has a first surface 266 (e.g., Figure 1 's first surface 118) and a second surface 268 opposite the first surface 266 (e.g., Figure 1 's second surface 120). The first retention feature 262 has a V - shaped shape formed by removing material from the lead finger 260 (similar to the Figure 2A 's retention feature) to form a notch, recess, channel, groove, trench, hole, slit, slot, depression, etc. The second retention feature 264 is formed by adding material to the second surface 268 of the lead finger 260 and projects from the second surface 268 to form a bump, peak, fold, ridge, etc. Thus, the retention feature is formed by adding conductive material to the second surface 268 of the lead frame (e.g., Figure 1 's lead frame 102) and / or by removing conductive material from the lead frame.

[0035] In addition, various cross - sectional shapes are used for the retention feature. The cross - sectional shape of the retention feature can be based on the application of the semiconductor device (e.g., Figure 1 's semiconductor device 100), the position of the manufacturing feature at the second surface 268 of the lead frame, the type of molding compound (e.g., Figure 1 's molding compound 108), and / or the formation technique used to form the retention feature. Examples of some techniques that can be used to form the retention feature include rolling, stamping, grinding, cutting, punching, welding, deposition, etching, etc.

[0036] Figure 3 A method 300 for forming a semiconductor device (e.g., Figure 1 semiconductor device 100 having retention features) is shown. Figure 3 The method will be described with respect to examples of semiconductor device 100 shown at different stages of manufacturing method 300. For purposes of simplification, Figures 4 - 10 the same reference numerals are used to denote the same structures. Figures 4 - 10 At 302, method 300 includes providing a lead frame (e.g.,

[0037] lead frame 102). The lead frame is formed from a conductive sheet. For example, Figure 1 an example conductive sheet 400 formed from a conductive material such as copper is shown. Conductive sheet 400 includes a first surface 402 (e.g., Figure 4 first surface 118, Figure 1 corresponding first surfaces 204, 224, 244, and 266) and a second surface 404 opposite the first surface 402 (e.g., Figures 2A - 2D second surface 120, Figure 1 corresponding second surfaces 206, 226, 246, and 268). Conductive sheet 400 may include manufacturing features 406 extending in a first direction on the second surface 404. Manufacturing features 406 are features of the article forming conductive sheet 400. For example, manufacturing features 406 may be roller marks produced by rolling conductive sheet 400 to a desired thickness. As another example, manufacturing features 406 may be indentations produced by pressing conductive sheet 400. Figures 2A - 2D At 302,

[0038] the lead frame 500 (e.g., Figure 5 lead frame 102) shown in Figure 1 is formed from conductive sheet 400. For example, lead frame 500 is etched from conductive sheet 400. Etching is performed to form die attach pads 502 (e.g., Figure 1 die attach pads 110) and a plurality of lead fingers 504 (e.g., Figure 1 lead fingers 112), the plurality of lead fingers being arranged around a perimeter of die attach pad 502, coplanar with and spaced from the perimeter of the die attach pad. In some examples, a plurality of lead frames may be formed from conductive sheet 400. The lead fingers in the plurality of lead fingers 504 have corresponding surfaces having a lead finger shape, such as a rectangular shape, a T - shaped shape, or an L - shaped shape.

[0039] At 304, method 300 includes forming retention features in the second surface of the lead frame at the lead fingers that are adapted to bond to a molding compound. As Figure 6As shown in the example of, the lead frame 500 has a first surface 402 and a second surface 404 opposite the first surface 402, resulting in a modified lead frame 600. A set of retention features 602 (e.g., Figure 1 retention feature 122 of, Figure 2A retention feature 202 of, Figure 2B retention feature 222 of, Figure 2C retention feature 242 of, and Figure 2D retention features 262 and 264 of) are formed in the second surface 404 using a feature tool 604 in a second stage. The feature tool 604 adds conductive material to the second surface 404 of the lead frame 500 and / or removes conductive material from the second surface of the lead frame to form the retention features 602. For example, the feature tool 604 is a laser, a saw, etc., to scribe, saw, etch, deposit conductive material, thereby providing the retention features 602 at the second surface 404.

[0040] As described herein, the retention features 602 can have various shapes. In some examples, the retention features 602 are spaced-apart voids or recesses extending a depth from the second surface 404 toward the first surface 402. Thus, the retention features can include voids. The depth of the voids of the retention features 602 can be less than or equal to approximately 40% of the thickness of the lead frame 500. In one example, the retention features 602 have a V-shaped cross-section. For example, the V-shaped retention features 602 have spaced-apart sidewalls that taper along a direction extending from the second surface 404 toward the first surface 402.

[0041] Because the manufacturing features 406 are present on the second surface 404, the retention features 602 are disposed among the manufacturing features 406. In one example, the manufacturing features 406 extend in a first direction 606 (e.g., Figure 1 first direction 114 of). The first direction 606 extends in the plane defined by the lead frame 500 in a direction from the die attach pad 502 to the lead fingers 504. The retention features 602 longitudinally extend along the die attach pad 502 and the lead fingers 504 at the second surface 404. The retention features 602 longitudinally extend in a second direction 608 (e.g., Figure 1 second direction 116 of), which is coplanar with the first direction 606 and substantially perpendicular to the first direction. By adding the retention features to the lead fingers using the manufacturing features, as described herein, the combined features can form an interlocking structure to inhibit delamination caused by the manufacturing features.

[0042] At 306, method 300 includes attaching a die to the first surface. The die is attached to the die attach pad 502 using a bonding layer. As Figure 7 shown in the example of, the bonding layer 804 (e.g.,Figure 1 The bonding layer 105) is applied at least in a third stage to a metal contact layer 702 covering the die attachment pad 502 (e.g., Figure 1 the metal contact layer 104). Accordingly, the bonding layer 804 does not extend beyond the first surface 402 of the die attachment pad 502. The bonding layer 804 is an adhesive, such as an epoxy resin. Figure 8 illustrates a die 802 (e.g., Figure 1 the die 106) attached to the first surface 402 of the die attachment pad 502 via the bonding layer 804 in a fourth stage.

[0043] At 308, the method 300 includes attaching bonding wires from the die to the lead fingers. For example, Figure 9 illustrates bonding wires 902 attached at the die 802 and the lead fingers 504 in a fifth stage, thereby creating a semiconductor device 900 (e.g., Figure 1 the semiconductor device 100). Specifically, the top surface of the die 802 includes a first bonding pad, and the lead fingers 504 define a second bonding pad at the first surface 402. The bonding wires 902 are coupled between the first bonding pad and the second bonding pad. The bonding wires 902 form an electrical connection between the die 802 and the lead fingers 504.

[0044] At 310, the method 300 includes providing a molding compound to at least partially encapsulate the semiconductor device. For example, in Figure 10 the semiconductor device 900 is encapsulated in a molding compound 1002 (e.g., Figure 1 the molding compound 108) in a sixth stage. The molding compound 1002 at least partially encapsulates the die 802 and the second surface 404 of the lead frame 500. In some embodiments, the semiconductor device is a dual-mode body device, such as a small outline transistor (SOT) device, where the molding compound is on top and bottom of the semiconductor device. The retention feature 602 is adapted to receive the molding compound 1002 to increase the surface area of the second surface 404. The additional surface area provides additional adhesion. Additionally, the retention feature 602 can be configured and arranged to extend in a direction perpendicular to the direction of the manufacturing features to increase the mechanical interlock force with the molding compound. The increased mechanical interlock between the lead frame 500 and the molding compound 1002 reduces delamination and failures caused by delamination.

[0045] In this specification, unless otherwise specified, "about," "substantially," or "generally" before a parameter means within + / – 10% of the stated parameter. Within the scope of the claims, modifications may be made in the described embodiments, and other embodiments are possible.

[0046] In this specification, the term "coupled" may encompass a connection, communication, or signal path that enables a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first instance, device A is coupled to device B by a direct connection; or (b) in a second instance, device A is coupled to device B through an intermediate component C, provided that the intermediate component C does not change the functional relationship between device A and device B such that device B is controlled by device A via the control signal generated by device A.

[0047] In this specification, a device "configured to" perform a task or function may be configured (e.g., programmed and / or hardwired) by a manufacturer at the time of manufacture to perform the function, and / or may be configured (or reconfigured) by a user after manufacture to perform the function and / or other additional or alternative functions. The configuration may be performed by firmware and / or software programming of the device, by the construction and / or layout of the hardware components and interconnections of the device, or a combination thereof. Additionally, a circuit or device described herein as including specific components may actually be configured to be coupled to those components to form the described circuitry or device. For example, a structure described herein as including one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, and / or inductors), and / or one or more sources (e.g., voltage sources and / or current sources) may alternatively include only semiconductor elements (e.g., semiconductor die and / or integrated circuit (IC) packages) within a single physical device and may be configured to be coupled to at least some of the passive elements and / or sources to form the described structure at the time of manufacture or after manufacture, e.g., by an end user and / or a third party.

[0048] The phrase "based on" means "at least partially based on". Thus, if X is based on Y, then X may be a function of Y and any number of other factors.

[0049] Within the scope of the claims, modifications may be made to the described embodiments, and other embodiments are possible.

Claims

1. An integrated circuit IC package, comprising: a lead frame of conductive material, the lead frame comprising a die attach pad and lead fingers spaced apart from edges of the die attach pad, wherein the lead frame has a first surface and a second surface opposite the first surface; a retention feature located on the lead finger at the second surface; a die on the first surface at the die attach pad; and A molding compound encapsulates the leadframe and the die and extends into and / or around the retention features. 2 . The IC package of claim 1 , wherein the lead frame includes manufacturing features on the second surface, and the retention features are disposed among the manufacturing features.

3. The IC package of claim 2, wherein the retention features comprise a retention feature arrangement in the second surface.

4. The IC package of claim 3, wherein the manufacturing features extend in a first direction and the retention features include spaced apart grooves extending longitudinally along the lead fingers at the second surface in a second direction substantially perpendicular to the first direction. The IC package of claim 1 , wherein the lead fingers have a T-shape.

6. The IC package of claim 1, wherein the retention features are a first set of retention features and a second set of retention features are formed on the second surface at the die attach pad.

7. The IC package of claim 3, wherein the retention features comprise spaced-apart gaps extending a depth from the second surface toward the first surface, and the depth is less than or equal to approximately 40% of a thickness of the lead frame.

8. The IC package of claim 7, wherein at least one of the voids has spaced-apart sidewalls that taper in a direction extending from the second surface toward the first surface.

9. The IC package of claim 7, wherein at least one of the voids has a V-shaped cross-section.

10. The IC package of claim 1, wherein: The lead fingers include a plurality of lead fingers arranged around a perimeter of the die attach pad, coplanar with the perimeter of the die attach pad and spaced apart, Each of the lead fingers has a corresponding retention feature formed along the second surface thereof, and the molding compound extends into and / or around the corresponding retention feature.

11. A method of forming an integrated circuit IC, comprising: providing a lead frame of conductive material, the lead frame comprising lead fingers and a die attach pad separated by a distance, wherein the lead frame has a first surface and a second surface opposite the first surface; and Retention features adapted to receive molding compound are formed in the second surface of the lead frame at the lead fingers, wherein the retention features are formed by adding and / or removing material relative to the second surface.

12. The method of claim 11, wherein a top surface of the die comprises a first bonding pad, the lead fingers defining a second bonding pad at the first surface, the method further comprising: coupling a bond wire between the first bonding pad and the second bonding pad; attaching the die to the first surface at the die attach pads; as well as The molding compound is provided to encapsulate the lead frame, the bond wires, and the die, wherein the molding compound extends into and / or around the retention features.

13. The method of claim 11, wherein the lead finger comprises a plurality of lead fingers arranged around and spaced apart from the die attach pad, and forming the retention feature comprises forming a void along the second surface of each of the respective lead fingers. The method of claim 13 , wherein forming the void comprises etching the second surface using a laser to form the void.

15. The method of claim 13, wherein at least one of the voids has spaced-apart sidewalls that taper in a direction extending from the second surface.

16. The method of claim 11, wherein the lead frame includes fabricated features in the second surface extending in a first direction, and the retention features are located among the fabricated features extending in a second direction substantially perpendicular to the first direction.

17. The method of claim 11, wherein the spacing between adjacent pairs of the retention features is approximately 25 microns to 40 microns.

18. The method of claim 11, wherein the leadframe has a leadframe thickness between the first surface and the second surface, and the retention feature extends from the second surface toward the first surface to a depth less than or equal to approximately 40% of the leadframe thickness.

19. An apparatus comprising: A sheet of conductive material having a first surface and a second surface opposite the first surface, wherein fabrication features extend in a first direction along at least one of the first surface and the second surface, the sheet comprising: a die attach pad; and A plurality of lead fingers are spaced apart from and surround the die attach pad, wherein a retention feature arrangement is formed in at least one of the lead fingers extending along a second direction substantially perpendicular to the first direction.

20. The device of claim 19, wherein the sheet is a lead frame, and the device further comprises: a die attached to the first surface at the die attach pad; as well as A molding compound encapsulates the lead frame and the die and extends into the retention features of the retention feature arrangement.

21. The apparatus of claim 19, wherein the at least one lead finger has a T-shape and the retention feature is a groove.

22. The device of claim 19, wherein the retention feature arrangement comprises a void formed on the second surface at the die attach pad.

23. The device of claim 22, wherein at least one of the voids has spaced-apart sidewalls that taper in a direction extending from the second surface.

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