TWI394255B - Semiconductor device having a trench wire for limiting solder capillary phenomenon - Google Patents

Description

Semiconductor device having a trench wire for limiting solder capillary phenomenon

SUMMARY OF THE INVENTION The present invention generally relates to the field of semiconductor devices and processes, and more particularly to surface mount devices having wires having trenches for limiting solder capillary phenomena.

The leadframe of the semiconductor device provides a stable support pad to securely position the semiconductor wafer, typically an integrated circuit (IC) wafer, in a package. It is a common practice to manufacture a single piece lead frame from a thin (about 100 to 250 μm) piece of metal. For reasons of ease of manufacture, the initially selected metals are copper, copper alloys, iron-nickel alloys (such as the so-called "alloy 42") and aluminum. The desired shape of the lead frame is stamped or etched from the original sheet.

In addition to the wafer pad, the leadframe provides a plurality of conductive segments to bring various electrical conductors in close proximity to the wafer. The remaining gap between the inner end of the segments and the contact pads on the surface of the IC is bridged by a connector, typically a thin metal wire such as gold is individually bonded to the IC contact pads and the lead frame segments .

The ends of the wire segments that are remote from the IC chip ("outer" end) need to be electrically and mechanically connected to an external circuit such as a printed circuit board. This attachment is typically performed by conventional soldering using a lead/tin alloy solder at a reflow temperature above 200 °C. Therefore, the surface of the end of the outer section needs to have a metallurgical configuration suitable for reflow attachment to external components.

When lead-free solder must be used due to environmental factors, assembly difficulties have recently appeared, because such solders generally present a problem of solder capillary phenomenon. When a capillary phenomenon occurs, most of the solder, sometimes almost all of the solder, is pulled from the solder area by surface tension to portions of the wire that are not included in the attachment of the device. The board attachment of the device may thus become poorly controlled and unreliable.

Recent other technology trends have made the device attachment process worse. For example, package size and wire length are reduced to provide a smaller surface for solder attachment. Next, the need to use lead-free solder pushes the reflow temperature range to approximately 260 ° C, making it more difficult to suppress solder capillarity.

In addition, market pressures drive the cost reduction of wireframes and therefore emphasize the reduction of any expensive metals used in the wireframe. This is especially true for any precious metal such as gold or palladium that may be commonly used in wireframes. This cost reduction may have another detrimental effect on the capillary phenomenon problem.

Applicants have recognized a need for a low cost, yet reliable method of fabricating a surface mount device having a leadframe structure to avoid the risk of solder bristle of any solder and any leadframe material. In addition, the method needs to be suitable for such devices that are already in the final assembly stage of refurbishment and formation, and is suitable for new devices that still have the option of using built-in precautioned wire frames to first eliminate the threat of capillary phenomena. Technical advantages when the lead frame and its method of manufacture are flexible enough to be applied to different semiconductor product families and a wide range of design and assembly changes, and to improve the process yield and device reliability .

The applicant performs mechanical and metallurgical studies of the welding process of the wires of a pair of surface mount devices at elevated temperatures. When the liquid solder exhibits a capillary phenomenon, it is pulled under the solid surface by capillary force based on the surface tension. Applicant recognizes that the work of lifting the solder continues until the energy obtained by the surface is balanced with the energy required to lift the quality of the solder against gravity. When this balance is reached, there is no additional energy to pull the solder up and the capillary phenomenon ceases to develop. Applicants have discovered that the solder capillary phenomenon can be slowed down and stopped. When the solder creeps up the wires, the quality of the liquid solder is locally accumulated by collecting the solder in a cavity-like trap until the solder acts by lowering the temperature. And the solder is solidified and completely stopped.

One embodiment of the present invention is a surface mount semiconductor device having a package of lead frames having outer portions of the wires that are not sealed by the package. The outer segments have a width and a length; it is convenient to consider constructing the length into five abutting portions. The first portion projects approximately horizontally from the seal. The second portion forms a downward convex curvature. The third part is approximately straight down. The fourth portion forms an upward concave curve. The fifth part is horizontal and straight.

In this embodiment of the invention, there is a first groove spanning the width in the third portion of each segment; the groove may be located on the surface of the bottom segment, or it may be located on the surface of the top segment . In either case, the trench is preferably a thickness of about two wire frames vertically above the bottom surface of the first wire portion.

The trench may have an angular profile having a depth of between about 5 and 50 μm, preferably by embossing, or it may have an approximate semicircle having a depth of between about 50 and 125 μm. The contour of the shape is preferably made by etching. In addition to the first trench, a second trench can be located in the second segment portion; for some devices, a third trench can be located in the transition region from the third segment portion to the fourth segment portion.

Other embodiments of the present invention are methods of fabricating a semiconductor device that are distinguished by the techniques employed to create the trenches in the wires. The trenches can be stamped or etched. For the creation of such trenches by imprinting, the method first provides a metal leadframe having a top surface and a bottom surface, a thickness, and inner and outer sections. The outer segments are configured as wires having a width and a length; they are interconnected by a barrier. Next, a semiconductor wafer is mounted on the inner segments, and the wafer and the inner segments are enclosed in a plastic seal, leaving the wires unenclosed.

The barrier bars are then removed and the first trenches are embossed across the width of the wires into the bottom or top surface of the wires. The embossing is performed simultaneously with the removal of the barrier bars or subsequent removal of the barrier bars. The contours of the grooves have an approximate angular shape with a depth of between about 5 and 50 μm. Then, the length of the wires is formed as five abutting portions; a first portion that protrudes substantially horizontally from the seal; a second portion that forms a downward convex curvature; and a third portion that is downwardly Is approximately straight, wherein the third portion includes the groove; a fourth portion that forms an upward concave curvature; and a fifth portion that is horizontally straight. The trench is positioned to a thickness of about two wire frames vertically above the bottom surface of the fifth portion.

For the creation of the trenches by etching, the method first provides a metal lead frame having a top surface and a bottom surface and a thickness, and then forming an inner segment and an outer segment, wherein the outer segments are configured As a wire having a width and a length, and interconnected by a barrier bar. Next, a first trench is etched across the width of each of the wires, preferably having a semi-circular profile and a depth between 50 and 225 μm. The trench can be etched into the bottom or top surface of the leadframe.

A semiconductor wafer is mounted on the inner segments and the wafer and the inner segments are enclosed in a plastic seal, leaving the wires unenclosed. Removing the barrier rod and forming the length of the wires into five abutting portions: a first portion that protrudes substantially horizontally from the seal; a second portion that forms a downward convex curve; a third portion The downward direction is approximately straight, wherein the third portion includes the groove; a fourth portion that forms an upward concave curvature; and a fifth portion that is horizontally straight. The groove is positioned to a thickness of about two wire frames in a direction perpendicular to the bottom surface of the fifth portion.

The development of the technology represented by the specific embodiments of the present invention will become apparent when the following description of the exemplary embodiments of the invention is considered.

Figure 1 shows an exemplary embodiment of the invention. It describes a portion of a semiconductor device generally designated 100, which belongs to the family of surface mount products. These devices have an insulative package 120 having a raised metal segment 101 that is an outer package 120 and is therefore referred to as an outer segment 101. The outer segments are shaped and formed to attach to the surface of a substrate or plate 190 using solder 110; the shape shown in Figure 1 is generally referred to as a "gull-wing" shape. After soldering a surface mount device to the substrate, it is easy to visually inspect all solder reflow addresses to determine defect free attachment and contact - a major reason why surface mount devices are so popular in the semiconductor industry.

The metal component of device 100 includes pad 102 for stably positioning semiconductor wafer 103, metal outer segment 101, and metal segment 104 within package 120 ("inner" segment). The inner section 104 and the outer section 101 are part of the wires of the device 100 and are used to bring the power, ground and signals into close proximity to the wafers. The remaining gap between the top end of the inner segments 104 and the contact pads 105 on the surface of the wafer is typically bridged by thin wires 106 that are individually soldered to the wafer contact pads and the inner segments of the lead frames. Thus, wafer 103 is electrically connected to the inner segments 104 by bond wires 106. At the beginning of the assembly process, pad 102 and segments 101 and 104 are held together by a metal frame (not shown in Figure 1) and are therefore commonly referred to as components of the original device "wire frame." Moreover, at the beginning of the assembly process, the segments are mechanically stabilized by metal rails that are positioned such that they can also be used to resist any high pressure accidental extrusion of any plastic material used in the molding process. Barriers; therefore, these tracks are called "barrier bars."

For simple and cost-effective manufacturing, it is common practice to fabricate a single piece of wire frame from a thin flat sheet of metal such as copper, copper, aluminum, and iron/nickel alloy. The thickness of the sheet 107 and thus the normal range of the segments 101 and 104 is between about 100 and 250 μm. The wire frame sheets, and thus the wires comprising the outer segment 101, have a top surface 101a and a bottom surface 101b. The desired shape of the overall leadframe is etched or stamped from this original sheet. In this manner, an individual wire comprising an outer segment of the leadframe is in the form of a thin, flat elongated strip of metal having a particular length and width as determined by design. In the embodiment of FIG. 1, the width of the outer segments of device 100 are equal and designated as 108. The size of the width 108 varies greatly depending on the segment pitch between the centers. The pitch can vary from about 1.27 to 0.15 mm between various device types.

After the wafer is mounted on the lead frame, the assembled components are preferably sealed ("packaged") by a plastic molding technique. As a result, Figure 1 shows that the wafer 103 and the inner segment 104 are enclosed. In the package 120, the outer segments 101 are still unsealed at the same time. In the next process step, the metal frame (not shown in Figure 1) holding the wire frames together is mechanically removed ("trimming"). At the same time, the barrier bars between the segments are mechanically removed (not shown in Figure 1). In Figure 1, the position at the two adjacent segments of the barrier bar original interconnect is marked by cross hatch 130.

After the trimming process, but preferably in the same machine, a "forming" process is performed in which the length of the outer segment of the device is pressed into a particular shape such that the outer segments can be used as electrical conductors for the device and the device is Connect to external parts. Figure 1 shows the results of a forming process in accordance with the present invention which constructs the length of the outer segments into five contiguous portions.

The first portion designated 141 protrudes approximately horizontally from the seal 120 and extends to a position where the barrier bar is located. The length of portion 141 can vary from about 50 to 370 [mu]m. In the second portion 142, the segment forms a downward convex curvature; the second portion preferably has a length of between about 250 and 1250 μm.

The third portion 143 is approximately straight and oriented downward. The length of the portion can vary widely as it primarily determines the distance of the package 120 from the attached substrate. For many devices, the length of portion 143 is between about 250 and 1250 μm or exceeds it. The fourth portion 144 forms an upward concave curve. It is more curved than portion 142; its preferred length is between about 250 and 1000 μm. The fifth portion 145 is horizontally straight; its length can vary widely, but is preferably in the range of about 500 to 1500 μm.

Portions 145 and 144 of segment 101 were originally included in the solder attachment of device 100 to substrate 190. In order to facilitate the flow of the solder 110, a metal layer is preferably provided on at least the surface 101b of the portions 145 and 144 which have an affinity for the tin-solder solder. The preferred metal layer comprises nickel followed by an external palladium layer or a nickel of an external gold layer.

On the other hand, when the segment portion 143 and especially the segments 142 and 141 are covered by solder, the detrimental effect of the solder capillary phenomenon can be found. The solder is pulled away from portions 145 and 144 such that it needs to be used to attach solder where it is missing; it accumulates near the portions of package 120, which is completely useless here.

Shortly after the start of the soldering process, a flux used with the liquid solder forms a film along the surface of a wire segment that wets the surface of the segment. During this capillary phenomenon, energy is required to pull a certain amount of solder against the gravity (usually based on tin having a density of 7.3 g ‧ cm ^-3 ) while the surface energy is consumed by the flux film consuming the wet surface Released as part of it. At the beginning of the process, the released energy predominates; however, as the solder progresses upward, the energy required to lift the accumulated solder mass is close to the released energy, eventually reaching an equal amount. The segment trenches of the present invention serve to accumulate the location of the desired solder mass to outperform the capillary phenomenon process. In many assembly applications, the solder is kept in a liquid state for a short period of time such that the slowing down of the capillary phenomenon caused by the grooves is sufficient to suppress any detrimental capillary phenomenon before the temperature drops again and the solder solidifies.

To avoid solder capillary phenomenon, Figure 1 shows conductors 101 having at least one trench across the width 108 of the segment. Similarly, in the embodiment of FIG. 2, each of the wires 101 has at least one groove that spans the width 108 of the segment. In FIG. 1, a first trench 151a is located in the third segment portion 143; a more specific feature of the location is the trench centerline. The trench 151a has a depth and a profile; in Figure 1, the depth of the trench 151a extends from the bottom surface 101b into the segment of metal. Similarly, in Figure 2, a first trench 151b is located in the third segment portion 143; a more specific feature of this location is the trench centerline. The groove 151b has a depth and a profile, wherein the depth extends from the top surface 101a into the segment of metal.

The centerlines of the grooves 151a and 151b extend across a width 108 that is perpendicular to the edges of the segments. Preferably, the groove centerline is located at about two wire frame thicknesses 107 vertically above the bottom surface 101b of the fifth segment portion 145. This position has a distance 109 from one of Figures 1 and 2.

The depth of the grooves depends on the method used to create the grooves (see below); each method produces a characteristic profile of the grooves. When the grooves are created by embossing, as is preferred in the package refurbishing-forming operation, they have an approximately angular profile. A more detailed description of this profile is depicted in Figure 3. In the case of an angular profile, the preferred depth is between about 5 and 50 μm, preferably less than half of the segment thickness 107.

On the other hand, when the trenches are produced by an etch, as is typically done in the fabrication of the leadframe, it has an approximately semi-circular profile. A more detailed description of this profile is depicted in Figure 4. In this case, the preferred groove depth is between about 50 and 125 [mu]m, about half the thickness of the segment 107.

It should be noted that in Fig. 2, the solder 111 not only wets the bottom surface 101b of the segment portions 144 and 145 but also wets the top surface 101a. Thus solder 111 can be effectively stopped by extending from top surface 101a into the trenches of the segment of metal.

As shown in Figures 1 and 2, in many device applications, it is preferred to have more than one trench in each segment to reliably avoid solder capillary phenomena; such additional trenches can be fabricated without additional cost. The location of the additional trenches can be carefully selected; as an example, in Figure 1, a second trench 152a is located in the second segment portion 142, approximately in the middle of the convex curvature of portion 142; 151a, a groove 152a is formed on the bottom surface 101b of the outer segment. In contrast, in Figure 2, the second trench 152b is fabricated on the top surface 101a of the outer segment. The location of the second trench can be carefully selected. Figure 2 depicts trench 152b in the second portion 142 about midway between the convex curvature of portion 142.

As another example of an additional trench, one of the third trenches 153a in FIG. 1 is located at a transition from the second portion to the third portion of the outer portion; however, it should be noted that the position of the third trench is Flexible. Like the groove 151a, the groove 153a is formed on the bottom surface 101b of the outer section. Conversely, in Figure 2, the third groove 153b is fabricated on the top surface 101a of the outer segment. Although the position of the third groove is flexible, Figure 2 depicts the groove 153b at the transition from the second portion to the third portion of the outer segment.

A system within the scope of the present invention can apply a plurality of additional grooves from the surface of the bottom segment into or out of the metal into the metal. Furthermore, the contours of the additional grooves may be angular or semi-circular.

The schematic cross-sectional view of FIG. 3 repeats the groove position and angular profile of FIG. 1 and allows for comparison with the semi-circular groove profile of FIG. Preferably, the groove shape of Figure 3 is produced by embossing a relatively shallow profile during the trim-forming package step of device fabrication. These grooves can therefore be applied to products that are already present, almost completed. Conversely, the trench shapes of Figure 4 are preferably produced in an earlier step in the fabrication of the leadframe by etching a relatively deep profile.

For ease of comparison, the positions of the angular grooves in FIG. 3 are the same as those of the angular grooves in FIG. 1; the grooves in FIG. 3 have also been assigned corresponding to the grooves in FIG. .

Conversely, the semi-circular grooves in Fig. 4 are at positions corresponding to the equiangular grooves in Figs. 1 and 3, but have been given different designations (161a, 162a, 163a) because of Etc. not only have different profiles, but are also manufactured in different processes in the manufacturing process (see below).

More particularly, Figures 1, 2 and 3 illustrate a method for fabricating a semiconductor device having an angular trench from which a metal wire frame strip is provided, the leadframe strip having a top The surface and a bottom surface, a thickness and a plurality of assembly sites having inner and outer segments. The outer segments have a width and a length and are interconnected by a barrier bar. A semiconductor wafer is then provided.

A semiconductor wafer is assembled (e.g., using an adhesive) at each of the assembly sites and attached to the inner segments. The assembled wafers and the inner segments are then enclosed in a plastic seal, leaving the outer segments unenclosed. The addresses are then singulated from the strip (eg by sawing).

The barrier bars are then removed (by punching) in the wireframe refurbishing machine. Further, in this machine, a first groove is embossed across the width of each of the wires. The embossing tool can have its indentations enter the bottom surface of the segments or into the top surface. The embossing of the groove can be performed simultaneously with the removal of the barrier bar, or the subsequent steps of removing the barrier bar. The trench has a profile (preferably angular for the imprint technique) and a depth. For embossing, the depth is preferably between about 5 and 50 μm. Additionally, the trench has a centerline; as described below, the centerline has a preferred location relative to the bottom surface of the segment.

In the following process steps, the formation of an unsealed section is performed in a forming machine. Forming the length of the outer segments into five abutting portions: a first portion that protrudes substantially horizontally from the seal; a second portion that is bent downwardly with a convex bend; a third portion The orientation is approximately straight down and includes a groove (embossed into or into the surface of the top section); a fourth portion that forms an upwardly concave curve and enters a fifth portion that is horizontally straight The transition. Preferably, the centerline of the trench is about two wire frame thicknesses vertically above the bottom surface of the fifth portion.

In addition to the first trench, the same process allows for the fabrication of a second trench, a third trench, or more trenches. For example, the embossing step can include embossing a second trench on the bottom surface (or the top surface) across the width of the segment, wherein the second trench is preferably located in the second portion of the outer segment section. In addition, the embossing step may further include imprinting a third trench on the bottom surface (or the top surface) across the width of the segment, wherein the third trench is preferably located from the outer segment The transition from the second part to the third part.

Another embodiment of the present invention is a method for fabricating a semiconductor device having a semi-circular trench, and FIG. 4 shows the method for providing a top surface from the surface of the bottom segment or the surface of the top segment. a bottom surface and a sheet of metal. A wire frame strip is formed to include a plurality of assembly addresses having wires having inner and outer segments. The outer segments have a width and a length and are interconnected by a barrier bar. Next, a first trench is etched across the width of each outer segment, preferably by means of a mask. This etching can be performed into the bottom surface of the metal sheet or into the top surface. For most leadframe metals, the trenches have an approximately semi-circular profile and preferably have a depth of between about 50 and 125 [mu]m. The grooves further have a centerline; as will be described below, the centerline has a preferred location relative to the bottom surface of the segments.

A semiconductor wafer is then provided. A wafer is assembled (e.g., by using an adhesive) at each of the assembly sites and joined (e.g., by wire bonding) to the inner segments. The assembled wafers and the inner segments are then enclosed in a plastic seal, leaving the outer segments unenclosed. The addresses are then singulated from the strip. The barrier bars are then removed in a refinishing machine, for example by punching.

In the following process steps, the formation of an unsealed section is performed in a forming machine. Forming the length of the outer segments into five abutting portions: a first portion that protrudes substantially horizontally from the seal; a second portion that is bent downwardly with a convex bend; a third portion Oriented to be approximately straight down and include a groove (etched into or into the surface of the top segment); a fourth portion that forms an upward concave bend and enters a fifth portion that is horizontally straight transition. Preferably, the centerline of the trench is about two wire frame thicknesses vertically above the bottom surface of the fifth portion.

In addition to the first trench, the same process allows for the fabrication of a second trench, a third trench, or more trenches. For example, the etching step can include etching a second trench over the bottom surface (or the top surface) across the width of the segment, wherein the second trench is preferably located in a second portion of the outer segment. In addition, the etching step may further include etching a third trench on the bottom surface (or the top surface) across the width of the segment, wherein the third trench is preferably located from the second portion of the outer segment To the transition of the third part.

The present invention is applicable to products using any type of semiconductor wafer, discrete circuit or integrated circuit, and the material of the semiconductor wafer may include germanium, antimony telluride, gallium arsenide or any other semiconductor material used in integrated circuit fabrication. Or compound material. Instead of a single wafer mounted within the seal, the device can employ a wafer stack and the assembly can employ flip chip technology. Additionally, the wafer assembly address can be metal of another material.

Embodiments having one or more of these various features or combinations of steps described in the context of an exemplary embodiment having all or only some such features or steps are intended to be encompassed herein. It will be apparent to those skilled in the art that many other embodiments and modifications are possible within the scope of the invention.

100. . . Semiconductor device

101. . . segment

101a. . . Top surface

101b. . . Bottom surface

102. . . pad

103. . . Semiconductor wafer

104. . . Inner section

105. . . Contact pad

106. . . Welding wire

107. . . thickness

108. . . width

109. . . distance

110. . . solder

111. . . solder

120. . . Package

130. . . Cross hatch

141. . . first part

142. . . the second part

143. . . the third part

144. . . fourth part

145. . . the fifth part

151a. . . First groove

151b. . . First groove

152a. . . Second groove

152b. . . Second groove

153a. . . Third groove

153b. . . Third groove

161a. . . Trench

162a. . . Trench

163a. . . Trench

190. . . Substrate/board

Figure 1 is a schematic perspective view of a portion of a surface mount device having a plurality of wire segments in accordance with the present invention, the wire segments being characterized by grooves in the bottom surface;

Figure 2 is a schematic perspective view of a portion of a surface mounting device having a plurality of wire segments in accordance with the present invention, the wire segments being characterized by grooves in the top surface;

Figure 3 is a schematic cross-sectional view of a portion of a surface mount device having a plurality of wire segments, the wire segments being characterized by angular contoured grooves on the bottom surface;

Figure 4 is a schematic cross-sectional view of a portion of a surface mount device having a plurality of wire segments characterized by a semi-circular profiled groove on the bottom surface.

100. . . Semiconductor device

101. . . segment

101a. . . Top surface

101b. . . Bottom surface

102. . . pad

103. . . Semiconductor wafer

104. . . Inner section

105. . . Contact pad

106. . . Welding wire

107. . . thickness

108. . . width

109. . . distance

110. . . solder

120. . . Package

130. . . Cross hatch

141. . . first part

142. . . the second part

143. . . the third part

144. . . fourth part

145. . . the fifth part

151a. . . First groove

152a. . . Second groove

153a. . . Third groove

190. . . Substrate/board

Claims (12)

A semiconductor device comprising: a metal lead frame having a top surface and a bottom surface, a thickness, and a plurality of inner and outer segments; a semiconductor wafer coupled to the inner segments; the wafer and the The inner segment is enclosed in a plastic seal, the outer segments are unenclosed; the outer segments have a width and a length configured as five abutting portions: a first portion protrudes substantially horizontally from the seal; The second portion forms a downward convex curvature; a third portion is approximately straight downward; a fourth portion forms an upwardly concave portion; and a fifth portion is horizontally straight; and each of the wires has a width across the width One of the first trenches is in the third segment, the trench having a centerline, a depth, and a contour. The device of claim 1 wherein the groove is on the bottom or top surface of the lead frame. The apparatus of claim 1, wherein the groove centerline is located at two wire frame thicknesses vertically above the bottom surface of the fifth portion. The device of claim 1, wherein the trench has an approximately angular profile and a depth between 5 and 50 μm; or wherein the trench has an approximately semi-circular profile and a between 50 and 125 μm The depth between. The device of claim 1, further comprising a first one located in the outer segment The second groove of the two parts. The device of claim 1 further comprising a third trench located at a transition from the second portion of the outer segment to the third portion. A method for fabricating a semiconductor device, the method comprising the steps of: providing a metal wire frame strip having a top surface and a bottom surface, a thickness, and a plurality of inner and outer segments Mounting addresses of the plurality of wires; the outer segments having a width and a length, and interconnected by a plurality of barrier bars; positioning a semiconductor wafer on each of the mounting sites and connecting the wafer to the inner segments Enclosing the wafers and the inner segments in a plastic seal, leaving the outer segments unenclosed; singulating the addresses from the strip; removing the barrier bars; spanning the wires The width is imprinted with a first groove having a center line, a contour and a depth; and the length of the outer segments is formed as five abutting portions, the abutting portions comprising: a first portion The seal is horizontally convex; a second portion forms a downward convex curvature; a third portion is approximately straight downward, the third portion includes the groove; and a fourth portion forms an upward concave curve; A fifth portion is horizontally straight, whereby the groove centerline is located at two wire frame thicknesses vertically above the bottom surface of the fifth portion. The method of claim 7, wherein the groove is imprinted into the bottom or top surface of the lead frame. The method of claim 7, wherein the trench has an approximately angular profile and a depth between 5 and 50 μm. The method of claim 7, wherein the embossing step is further included on the bottom surface or the top surface and embossing a second trench across the width of the segment, the second trench being positioned to be located at the second outer Section part. The method of claim 7, wherein the embossing step is further included on the bottom surface or the top surface and embossing a third trench across the width of the segment, the third trench being positioned to be located from the outer segment The second portion is transitioned to one of the third portions. The method of any one of claims 7 to 11, wherein the step of providing a metal lead frame comprises providing a metal sheet having the top surface and a bottom surface, a thickness; and forming a lead frame strip, the lead frame The strip includes a plurality of mounting addresses having a plurality of wires having a plurality of inner and outer segments; the outer segments having a width and a length and interconnected by a plurality of barrier bars.