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WO2019110096A1 - Lead frame, method for manufacturing a lead frame and semiconductor device with a lead frame - Google Patents

Lead frame, method for manufacturing a lead frame and semiconductor device with a lead frame Download PDF

Info

Publication number
WO2019110096A1
WO2019110096A1 PCT/EP2017/081702 EP2017081702W WO2019110096A1 WO 2019110096 A1 WO2019110096 A1 WO 2019110096A1 EP 2017081702 W EP2017081702 W EP 2017081702W WO 2019110096 A1 WO2019110096 A1 WO 2019110096A1
Authority
WO
WIPO (PCT)
Prior art keywords
lead frame
main surface
groove
groove wall
adjoining
Prior art date
Application number
PCT/EP2017/081702
Other languages
French (fr)
Inventor
Ismail ITHNAIN
Chee-Eng Ooi
Mooi Hiong LING
Original Assignee
Osram Opto Semiconductors Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Osram Opto Semiconductors Gmbh filed Critical Osram Opto Semiconductors Gmbh
Priority to PCT/EP2017/081702 priority Critical patent/WO2019110096A1/en
Publication of WO2019110096A1 publication Critical patent/WO2019110096A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/495—Lead-frames or other flat leads
    • H01L23/49541—Geometry of the lead-frame
    • H01L23/49544—Deformation absorbing parts in the lead frame plane, e.g. meanderline shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
    • H01L21/4814—Conductive parts
    • H01L21/4821—Flat leads, e.g. lead frames with or without insulating supports
    • H01L21/4842—Mechanical treatment, e.g. punching, cutting, deforming, cold welding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3107—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape the device being completely enclosed
    • H01L23/3142—Sealing arrangements between parts, e.g. adhesion promotors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/484—Connecting portions
    • H01L2224/4847—Connecting portions the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
    • H01L2224/48472—Connecting portions the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181—Encapsulation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/181—Encapsulation
    • H01L2924/183—Connection portion, e.g. seal
    • H01L2924/18301—Connection portion, e.g. seal being an anchoring portion, i.e. mechanical interlocking between the encapsulation resin and another package part

Definitions

  • Embodiments of the present invention are related to a lead frame, a method for manufacturing a lead frame and a
  • Packages for electronic devices usually comprise an
  • electrically conducting carrier as, for example, a lead frame, onto which at least one semiconductor chip is mounted.
  • the semiconductor chip and parts of the lead frame are covered by a molding material.
  • typical molding materials like PPA (polyphthalamide) and PCT
  • various methods are known to improve the mold adhesion, for example variously shaped grooves, for instance U-shaped or V-shaped grooves, in the lead frame, as described in prior art documents US 6,465,274, US 6,882,048 and US 2002/0084518.
  • the grooves described in the prior art fail to provide sufficient locking or gripping strength for the molding material, in particular in a vertical direction.
  • Certain embodiments of the invention specify a lead frame with at least one anchoring structure. Further embodiments specify a method for manufacturing such lead frame and a semiconductor device having such lead frame.
  • a lead frame has a first main surface and a second main surface.
  • the second main surface is located remote from the fist main surface.
  • a direction perpendicular to the first and the second main surfaces can be denoted as a vertical direction so that the first and second main surfaces can extend in a respective plane perpendicular to the vertical direction.
  • Directions perpendicular to the vertical direction can be denoted as lateral directions.
  • the first and the second main surfaces can delimit the lead frame in the vertical direction, meaning that the first main surface can be an upper side of the lead frame and the second main surface can be a lower side of the lead frame.
  • the lead frame has at least one anchoring structure.
  • the anchoring structure can be advantageously embodied to at least partly fix a plastic material, which can be applied onto the first main surface, to the lead frame.
  • the anchoring structure can be embodied to provide at least partial fixing of the plastic material in a vertical direction, meaning that the at least one anchoring structure can at least partly prevent the plastic material from being torn apart from the lead frame in a vertical direction.
  • the lead frame can have more than one anchoring structure, each of the anchoring structures having one or more features as explained before and in the following.
  • a lead frame in a method for manufacturing a lead frame with at least one anchoring structure a lead frame is provided, the lead frame having a first main surface and a second main surface being located remote from the first main surface.
  • the anchoring structure comprises at least one groove in the first main surface.
  • This can in particular mean that the first main surface is not completely flat but is interrupted by the at least one groove.
  • the groove can stretch across the first main surface, running in one or more lateral directions.
  • the at least one groove can have a first groove wall and a second groove wall, wherein a first part of the first main surface can adjoin the first groove wall and a second part of the first main surface can adjoin the second groove wall. Accordingly, the first part and the second part of the first main surface can be separated from each other by an opening in the first main surface, the opening being formed by the upper part of the groove.
  • the first groove wall and the second groove wall can adjoin each other at a bottom part of the groove, wherein the bottom part is located, in a vertical direction, between the first main surface and the second main surface. Consequently, the groove can reach into the lead frame from the first main surface toward, but not reaching, the second main surface.
  • the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface.
  • the at least one groove reaches into the lead frame in a direction tilted to the vertical direction.
  • the bottom part of the groove, where the first and second groove walls can adjoin each other is laterally offset with respect to the upper part of the groove and, in particular, with respect to the opening in the first main surface. Consequently, the groove can have a cross-section that is asymmetric.
  • the at least one groove can reach into the lead frame in a direction tilted to a direction perpendicular to the first main surface by an angle between and including 30° and 60°, for example about 45° .
  • the second groove wall and the part of the first main surface adjoining the second groove wall can form an overhang. This can mean that, as seen along the vertical direction, a part of the first main surface is arranged over a part of the groove and therefore also over a part of the second groove wall and a part of the first groove wall.
  • the second groove wall and the part of the first main surface adjoining the second groove wall can enclose an angle of more than 0° and less than 90°. This can mean that the part of the first main surface adjoining the second groove wall and the second groove wall meet at an acute angle, thereby forming an acute- angled edge delimiting the groove opening on the side of the second groove wall.
  • the first groove wall and the part of the first main surface adjoining the first groove wall enclose an angle of more than 90° and less than 180°. This can mean that the part of the first main surface adjoining the first groove wall and the first groove wall meet at an obtuse angle, thereby forming an obtuse-angled edge delimiting the groove opening on the side of the first groove wall .
  • the groove has a vertical depth which can be equal to or less than 1/2 of the thickness of the lead frame, which is the vertical distance of the first main surface to the second main surface.
  • the thickness of the lead frame as well as the depth of the groove can preferably be measured on the side of the first groove wall.
  • the depth of the groove can be equal to or more than 1/3 of the thickness of the lead frame.
  • the opening of the groove in the first main surface can have a lateral width of equal to or less than 1/2 of the thickness of the lead frame.
  • the lateral distance between the edge formed by the first main surface and the first groove wall and the edge formed by the first main surface and the second groove wall can be equal to or less than 1/2 of the thickness of the lead frame.
  • the lateral width of the opening of the groove can be equal to or more than 1/3 of the thickness of the lead frame.
  • the part of the first main surface adjoining the second groove wall is at a lower height, as seen in a vertical direction from the second main surface of the lead frame, as compared to the part of the first main surface adjoining the first groove wall, thereby defining a height difference.
  • the edge formed by the second main surface and the first groove wall is, as seen in a vertical direction, closer to the second main surface than the edge formed by the first main surface and the first groove wall.
  • the height difference can be between and including 1/4 to 1/2 of the vertical depth of the groove. This can also mean that the height difference can be about 1/3 of the vertical depth of the groove.
  • the anchoring structure has at least two grooves.
  • Each of the grooves can have one or more features as described before.
  • the grooves can be formed similarly and/or at the same time.
  • each of the grooves can have a first and a second groove wall and can reach into the lead frame along a
  • each of the directions is tilted to a direction perpendicular to the first main
  • the lead frame can have a pedestal in the first main surface, the pedestal having an upper surface being part of the first main surface, and sidewalls being formed by the second groove walls .
  • the upper surface of the pedestal is at a lower height, as seen in a vertical
  • the lead frame can be provided preferably with substantially or completely flat first and second main surfaces.
  • a first punching tool is used to create at least one groove in the first main surface, wherein the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface, the at least one groove having a first groove wall and a second groove wall.
  • the first punching tool can be a chisel, which is driven into the first main surface at a tilted angle with respect to the vertical direction.
  • the tilted angle can preferably be between and including 30° and 60°, for example about 45°.
  • the first punching tool can have a triangular cross-section, so that it can produce a
  • the produced triangular groove is also tilted about the same angle as the tool.
  • a second punching tool is used to punch a part of the first main surface adjoining the second groove wall so that the second groove wall and the part of the first main surface adjoining the second groove wall form an overhang.
  • the second punch tool can for example be stamp-like.
  • the punched part of the first main surface adjoining the second groove wall is at a lower height, as seen in a vertical direction from the second main surface of the lead frame, as compared to the part of the first main surface adjoining the first groove wall.
  • the first groove wall can be straight and without any curvature in a direction from the groove opening to the groove bottom, while the second groove wall can have a curvature, in particular a concave curvature, in a direction from the groove opening to the groove bottom.
  • the curvature of the second groove wall can be the result of the second punching step.
  • At least two grooves of an anchoring structure can be formed by a respective first punching tool.
  • the first punching tool can have a chisel as explained above.
  • a respective part of the first main surface adjoining each of the second groove walls of the grooves can be punched.
  • pedestal can be formed by the first punching step, which is then punched in the second punching step to form the
  • each of the grooves can have a first and a second groove wall and reach into the lead frame at a respective angle, wherein each of the angles is tilted to a direction perpendicular to the first main surface, wherein the second groove walls are at a smaller distance to each other than the first groove walls, and wherein each of the second groove walls and the
  • the lead frame can be plated with at least one metal layer.
  • the plating step can be performed preferably after the second punching step.
  • the lead frame can comprise a bulk material, which can be copper.
  • the lead frame can be provided as a bulk metal lead frame like, for instance, a copper lead frame.
  • one or more metals forming one or more metal layers can be applied to at least one side of the lead frame.
  • the plating can be performed on the upper side of the lead frame, i.e., the side of the lead frame with the at least one anchoring structure.
  • the one or more metals can be chosen for example from Ag, Al, Au, Ni, Pd and Sn.
  • a semiconductor device comprises a lead frame with at least one anchoring structure according to the embodiments described above.
  • the semiconductor device can comprise at least one semiconductor chip that is mounted on the first main surface of the lead frame.
  • the at least one semiconductor chip can be mounted laterally offset to the at least one anchoring structure.
  • the semiconductor device can comprise a plastic material formed over the semiconductor chip and the at least one anchoring structure, wherein the plastic material fills the at least one groove of the at least one anchoring structure.
  • the plastic material can be held in an interlocking manner, since the overhang of the at least one groove reaches over a part of the plastic material, so that a vertical holding force can be applied to the plastic material by the lead frame. Consequently, the at least one anchoring structure can provide the advantage that the plastic material can be enabled to interlock completely into the groove, leading to an increased gripping power between the lead frame and the plastic material as compared to usual lead frames. Thus, also seepage can be prevented and a prolonged product reliability can be obtained.
  • FIGS 1A to 1G show schematic illustrations of process
  • FIGS. 2A to 2G show schematic illustrations of process
  • Figures 3A and 3B show schematic illustrations of a
  • Figure 4 shows a schematic illustration of a semiconductor device having a lead frame according to another embodiment .
  • Figures 1A to 1G show schematic illustrations of process steps of a method for manufacturing a lead frame 1 according to an embodiment, the lead frame 1 having at least one anchoring structure 2.
  • a lead frame 1 is provided, the lead frame 1 having a first main surface 11 and a second main surface 12 being located remote from the first main surface 11.
  • the lead frame 1 is provided with substantially and, preferably, completely flat first and second main surfaces 11, 12, which extend in lateral
  • the lead frame 1 is preferably provided as a bulk metal lead frame.
  • the lead frame 1 is a copper lead frame, which can have a preferred thickness of equal to or greater than 0.2 mm.
  • a lead frame thickness of about 0.3 mm is typically used.
  • the lead frame 1 can also have a greater thickness.
  • the lead frame 1 can be formed mechanically and/or chemically, for example by stamping and/or etching, to have a desired shape.
  • Figure 1A merely shows a part of the lead frame 1.
  • a first punching tool 91 is used to create at least one groove 20 in the first main surface 11.
  • the first punching tool 91 can be a chisel or a similar tool that is driven into the first main surface 11 at a tilted angle Q with respect to the vertical direction, which is indicated by the dashed line and which is perpendicular to the first main surface 11.
  • the tilted angle Q can preferably be between and including 30° and 60°, for example about 45°.
  • the first punching tool 91 can have, as shown, a triangular cross-section, so that it can produce a triangular groove 20 in the lead frame 1.
  • the produced triangular groove 20 is also tilted about the same angle as the tool. Consequently, the groove 20 reaches into the lead frame 1 in a direction tilted to a direction perpendicular to the first main surface 11.
  • the first punching tool can have other shapes, thereby creating grooves with corresponding other shapes.
  • the groove 20 has a first groove wall 21 and a second groove wall 22. Due to the tilted application of the first punching tool 91, the first groove wall 21 and a part of the first main surface 11 adjoining the first groove wall 21 form an edge with an angle of more than 90° and less than 180°, i.e., an obtuse-angled edge, while the second groove wall 22 and a part of the first main surface 11 adjoining the second groove wall 22 form an edge with an angle of more than 0° and less than 90°, i.e., an acute- angled edge. Both edges delimit a groove opening in the first main surface 11. Furthermore, the first and second groove walls 21, 22 adjoin each other at a bottom part of the groove 20.
  • the bottom part is located, in a vertical direction, between the first main surface 11 and the second main surface 12 and can be laterally offset from the groove opening, so that, as seen along the vertical direction, a part of the first main surface 11 can be arranged over a part of the groove 20 and therefore also over a part of the second groove wall 22 and a part of the first groove wall 21.
  • the second groove wall 22 and a part of the first main surface 11 adjoining the second groove wall 22 can form an overhang .
  • a second punching step is performed, as shown in Figures ID and IE as well as in Figure IF in a magnified view.
  • a second punching tool 92 is used to punch a part of the first main surface 11 adjoining the second groove wall 22 so that the overhang 14 formed by the second groove wall 22 and the part of the first main surface 11 adjoining the second groove wall 22 is formed to be present in a more pronounced manner, thereby forming the anchoring structure 2.
  • the punching tool 92 can for example be stamp-like and can be applied along a vertical direction.
  • the punched part of the first main surface 11 adjoining the second groove wall 22 is at a lower height, as seen in a vertical direction from the second main surface 12 of the lead frame 1, as compared to the part of the first main surface 11 adjoining the first groove wall 21.
  • the first groove wall 21 can be straight and without any curvature in a direction from the groove opening to the groove bottom, while the second groove wall 22 can have a curvature, in particular a concave curvature, in a direction from the groove opening to the groove bottom.
  • the curvature of the second groove wall 22 is the result of the second punching step.
  • the structure 2 has a vertical depth H which can be equal to or less than 1/2 of the thickness of the lead frame 1.
  • the thickness of the lead frame 1 as well as the vertical depth H of the groove can preferably be measured on the side of the first groove wall 21, which is unaffected by the punching steps and therefore also by the anchoring structure 2.
  • the depth H of the groove 20 can be equal to or more than 1/3 of the thickness of the lead frame 1.
  • the opening of the groove 20 in the first main surface 11 can have a lateral width LI of equal to or less than 1/2 of the thickness of the lead frame 1.
  • the lateral distance between the obtuse-angled edge formed by the first main surface 11 and the first groove wall 21 and the acute- angled edge formed by the first main surface 11 and the second groove wall 22 can be equal to or less than 1/2 of the thickness of the lead frame 1.
  • the lateral width LI of the opening of the groove 20 can be equal to or more than 1/3 of the thickness of the lead frame 1.
  • the part of the first main surface 11 adjoining the second groove wall 22 is at a lower height, as seen in a vertical direction from the second main surface 12 of the lead frame 1, as compared to the part of the first main surface 11 adjoining the first groove wall 21, thereby defining a height difference D, which can be between and including 1/4 to 1/2 of the vertical depth H of the groove 20. Particularly preferably, the height difference D can be about 1/3 of the vertical depth H of the groove 20.
  • Figure 1G also the angle of the acute-angled edge and the angle b of the obtuse-angled edge are shown, which are as explained in connection with Figures IB and 1C. Moreover, after the second punching step the angle can be smaller than after the first punching step. Furthermore, the
  • Figures 2A to 2G illustrate another embodiment of a method for manufacturing a lead frame 1 with at least one anchoring structure 2. In contrast to the method explained in
  • the anchoring structure 2 of this embodiment has two grooves 20, wherein each of the grooves 20 can have one or more features as described before.
  • the grooves 20 can be formed similarly and/or at the same time, as it becomes apparent from Figures 2B to 2E.
  • each of the grooves 20 has a first and a second groove wall 21, 22 and reaches into the lead frame 1 along a respective direction, wherein each of the directions is tilted to a direction perpendicular to the first main surface 11, wherein the second groove walls 22 of the two grooves 20 are at a smaller distance to each other than the first groove walls 21, and wherein each of the second groove walls 22 and a respective part of the first main surface 11 adjoining the second groove walls 22 form a respective overhang 14. Consequently, the anchoring structure 2 has a pedestal 16 in the first main surface 11, the pedestal 16 having an upper surface 17 being part of the first main surface 11, and sidewalls being formed by the second groove walls 22.
  • L3 is preferably equal to LI.
  • the width L2 of the pedestal 16 can preferably be given by LI ⁇ L2 ⁇ 3> ⁇ L1.
  • the width L2 can be equal or substantially equal to 2> ⁇ L1.
  • the lead frame 1 can be plated with at least one metal layer (not shown) in a further method step.
  • the plating step can be performed preferably after the second punching step.
  • the plating can be performed on the upper side of the lead frame 1, i.e., the side of the lead frame 1 with the at least one anchoring structure 2, thereby covering the first main surface 11 and the anchoring structure (s) 2, or additionally also on the second main surface.
  • the at least one metal layer can comprise one or more metals in one or more layers.
  • the one or more metals can be chosen for example from Ag, Al, Au, Ni, Pd and Sn.
  • Figures 3A and 3B show a semiconductor device 100 having a lead frame 1 as explained in connection with the foregoing embodiments.
  • Figure 3B shows a magnified part of Figure 3A.
  • the lead frame 1 comprises anchoring structures 2 as explained in connection with Figures 2A to 2G .
  • the semiconductor device 100 comprises at least one semiconductor chip 3 that is mounted on the first main surface 11 of the lead frame 1.
  • the at least one semiconductor chip 3 is mounted laterally offset to the anchoring structures 2 and, in particular, between the anchoring structures 2.
  • the semiconductor chip 3 can be for example a light-emitting diode chip, so that the
  • semiconductor device 100 can be a light-emitting device.
  • the semiconductor device 100 comprises a plastic material 4 formed over the semiconductor chip 3 and the anchoring structures 2.
  • the plastic material 4 can be, for example, PPA, PCT or WEMC or other suitable plastic material.
  • the plastic material 4 can be applied, for example, by a molding process or a casting process. If necessary, a de flashing step, for example in the case of epoxy-based plastic material, can be performed afterwards.
  • the plastic material 4 fills the groove 20 of the anchoring structures 2. Since the grooves 20 form offset-interlocking grooves 20, the anchoring structures 2 can provide a vertical fixation of the plastic material 4 on the lead frame 1, thereby preventing an
  • the grooves 20 of the anchoring structures 2 can be placed in positions suitable for locking the plastic material 4. This can also mean that the grooves 20 partly or substantially completely surround the at least one
  • Figure 4 shows a further embodiment of a semiconductor device 100 having a lead frame 1 with anchoring structures 2 as explained in connection with the foregoing embodiments.
  • the lead frame 1 again comprises anchoring structures 2 as explained in connection with Figures 2A to 2G.
  • the semiconductor device 100 comprises at least one semiconductor chip 3, which can be a light-emitting semiconductor chip and which is mounted on the first main surface 11 of the lead frame 1 between the semiconductor chip 3, which can be a light-emitting semiconductor chip and which is mounted on the first main surface 11 of the lead frame 1 between the semiconductor chip 3, which can be a light-emitting semiconductor chip and which is mounted on the first main surface 11 of the lead frame 1 between the semiconductor chip 3, which can be a light-emitting semiconductor chip and which is mounted on the first main surface 11 of the lead frame 1 between the
  • the semiconductor device 100 shown in Figure 4 comprises a plastic material 4 that forms a reflector
  • the plastic material 4 which can be applied, for example, by a molding process or a casting process, can be, for example, PPA, PCT or WEMC or other suitable plastic material.
  • the encapsulant 5 can also comprise a plastic material, which is transparent for light that can be emitted by the semiconductor chip 3 when
  • the encapsulant 5 can comprise a silicone and/or an epoxy resin.
  • the anchoring structures 2 can provide a vertical fixation of the reflector housing formed by the plastic material 4 on the lead frame 1, thereby preventing an undesired delamination of the reflector housing from the lead frame 1. Furthermore, it could be possible that the lead frame 1 has one or more anchoring structures for a fixation of the encapsulant 5.
  • the embodiments shown in the figures can comprise further features described in the general part of the description.
  • features and embodiments of the figures can be combined with each other, even if such combination is not explicitly described.
  • the invention is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

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Abstract

A lead frame (1) is described, the lead frame comprising a first main surface (11) and a second main surface (12) being located remote from the fist main surface, and having at least one anchoring structure (2) with at least one groove (20) in the first main surface, wherein the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface, the at least one groove having a first groove wall (21) and a second groove wall (22), wherein the second groove wall and a part of the first main surface adjoining the second groove wall form an overhang (14). Furthermore, a method for manufacturing a lead frame and a semiconductor device with a lead frame are described.

Description

Description
LEAD FRAME, METHOD FOR MANUFACTURING A LEAD FRAME AND
SEMICONDUCTOR DEVICE WITH A LEAD FRAME
Embodiments of the present invention are related to a lead frame, a method for manufacturing a lead frame and a
semiconductor device with a lead frame.
Packages for electronic devices usually comprise an
electrically conducting carrier as, for example, a lead frame, onto which at least one semiconductor chip is mounted. The semiconductor chip and parts of the lead frame are covered by a molding material. However, typical molding materials like PPA (polyphthalamide) and PCT
(polycyclohexylenedimethylene terephthalate) as well as WEMC (white epoxy mold compound) tend to have a low adhesion to lead frame surfaces, especially to surfaces that are formed by an Ag or Au plating. The low adhesive strength can cause a gap between the molding material and the lead frame,
resulting in a risk of seepage of molding material, which can lead to solderability problems. Furthermore, there may be a risk of contamination of the chip due to penetration of harmful external materials through the gap.
Various methods are known to improve the mold adhesion, for example variously shaped grooves, for instance U-shaped or V-shaped grooves, in the lead frame, as described in prior art documents US 6,465,274, US 6,882,048 and US 2002/0084518. However, the grooves described in the prior art fail to provide sufficient locking or gripping strength for the molding material, in particular in a vertical direction. Certain embodiments of the invention specify a lead frame with at least one anchoring structure. Further embodiments specify a method for manufacturing such lead frame and a semiconductor device having such lead frame.
According to at least one embodiment, a lead frame has a first main surface and a second main surface. The second main surface is located remote from the fist main surface. A direction perpendicular to the first and the second main surfaces can be denoted as a vertical direction so that the first and second main surfaces can extend in a respective plane perpendicular to the vertical direction. Directions perpendicular to the vertical direction can be denoted as lateral directions. The first and the second main surfaces can delimit the lead frame in the vertical direction, meaning that the first main surface can be an upper side of the lead frame and the second main surface can be a lower side of the lead frame.
According to a further embodiment, the lead frame has at least one anchoring structure. The anchoring structure can be advantageously embodied to at least partly fix a plastic material, which can be applied onto the first main surface, to the lead frame. In particular, the anchoring structure can be embodied to provide at least partial fixing of the plastic material in a vertical direction, meaning that the at least one anchoring structure can at least partly prevent the plastic material from being torn apart from the lead frame in a vertical direction. Furthermore, the lead frame can have more than one anchoring structure, each of the anchoring structures having one or more features as explained before and in the following. According to at least one further embodiment, in a method for manufacturing a lead frame with at least one anchoring structure a lead frame is provided, the lead frame having a first main surface and a second main surface being located remote from the first main surface. The features described before and in the following apply equally to the lead frame and to the method for manufacturing the lead frame.
According to a further embodiment, the anchoring structure comprises at least one groove in the first main surface. This can in particular mean that the first main surface is not completely flat but is interrupted by the at least one groove. The groove can stretch across the first main surface, running in one or more lateral directions.
The at least one groove can have a first groove wall and a second groove wall, wherein a first part of the first main surface can adjoin the first groove wall and a second part of the first main surface can adjoin the second groove wall. Accordingly, the first part and the second part of the first main surface can be separated from each other by an opening in the first main surface, the opening being formed by the upper part of the groove. The first groove wall and the second groove wall can adjoin each other at a bottom part of the groove, wherein the bottom part is located, in a vertical direction, between the first main surface and the second main surface. Consequently, the groove can reach into the lead frame from the first main surface toward, but not reaching, the second main surface.
According to a further embodiment, the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface. In other words, the at least one groove reaches into the lead frame in a direction tilted to the vertical direction. This can mean that the bottom part of the groove, where the first and second groove walls can adjoin each other, is laterally offset with respect to the upper part of the groove and, in particular, with respect to the opening in the first main surface. Consequently, the groove can have a cross-section that is asymmetric. Particularly preferably, the at least one groove can reach into the lead frame in a direction tilted to a direction perpendicular to the first main surface by an angle between and including 30° and 60°, for example about 45° .
Moreover, the second groove wall and the part of the first main surface adjoining the second groove wall can form an overhang. This can mean that, as seen along the vertical direction, a part of the first main surface is arranged over a part of the groove and therefore also over a part of the second groove wall and a part of the first groove wall.
According to a further embodiment, the second groove wall and the part of the first main surface adjoining the second groove wall can enclose an angle of more than 0° and less than 90°. This can mean that the part of the first main surface adjoining the second groove wall and the second groove wall meet at an acute angle, thereby forming an acute- angled edge delimiting the groove opening on the side of the second groove wall.
According to a further embodiment, the first groove wall and the part of the first main surface adjoining the first groove wall enclose an angle of more than 90° and less than 180°. This can mean that the part of the first main surface adjoining the first groove wall and the first groove wall meet at an obtuse angle, thereby forming an obtuse-angled edge delimiting the groove opening on the side of the first groove wall .
According to a further embodiment, the groove has a vertical depth which can be equal to or less than 1/2 of the thickness of the lead frame, which is the vertical distance of the first main surface to the second main surface. The thickness of the lead frame as well as the depth of the groove can preferably be measured on the side of the first groove wall. Furthermore, the depth of the groove can be equal to or more than 1/3 of the thickness of the lead frame. Moreover, the opening of the groove in the first main surface can have a lateral width of equal to or less than 1/2 of the thickness of the lead frame. In other words, the lateral distance between the edge formed by the first main surface and the first groove wall and the edge formed by the first main surface and the second groove wall can be equal to or less than 1/2 of the thickness of the lead frame. Furthermore, the lateral width of the opening of the groove can be equal to or more than 1/3 of the thickness of the lead frame.
According to a further embodiment, the part of the first main surface adjoining the second groove wall is at a lower height, as seen in a vertical direction from the second main surface of the lead frame, as compared to the part of the first main surface adjoining the first groove wall, thereby defining a height difference. In other words, the edge formed by the second main surface and the first groove wall is, as seen in a vertical direction, closer to the second main surface than the edge formed by the first main surface and the first groove wall. In particular, the height difference can be between and including 1/4 to 1/2 of the vertical depth of the groove. This can also mean that the height difference can be about 1/3 of the vertical depth of the groove.
According to a further embodiment, the anchoring structure has at least two grooves. Each of the grooves can have one or more features as described before. Preferably, the grooves can be formed similarly and/or at the same time. In
particular, each of the grooves can have a first and a second groove wall and can reach into the lead frame along a
respective direction, wherein each of the directions is tilted to a direction perpendicular to the first main
surface, wherein the second groove walls of the two grooves are at a smaller distance to each other than the first groove walls, and wherein each of the second groove walls and a respective part of the first main surface adjoining the second groove walls form a respective overhang. Consequently, the lead frame can have a pedestal in the first main surface, the pedestal having an upper surface being part of the first main surface, and sidewalls being formed by the second groove walls .
According to a further embodiment, the upper surface of the pedestal is at a lower height, as seen in a vertical
direction, as compared to the parts of the first main surface adjacent to the first groove walls. In particular, the features described above in connection with the part of the first main surface adjoining the second groove wall being at a lower height as compared to the part of the first main surface adjoining the first groove wall apply also to the upper surface of the pedestal. For manufacturing the at least one anchoring structure in the first main surface of the lead frame, the lead frame can be provided preferably with substantially or completely flat first and second main surfaces.
According to a further embodiment, in a first punching step a first punching tool is used to create at least one groove in the first main surface, wherein the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface, the at least one groove having a first groove wall and a second groove wall. In particular, the first punching tool can be a chisel, which is driven into the first main surface at a tilted angle with respect to the vertical direction. The tilted angle can preferably be between and including 30° and 60°, for example about 45°. The first punching tool can have a triangular cross-section, so that it can produce a
triangular groove in the lead frame. Since the first punching tool is tilted, the produced triangular groove is also tilted about the same angle as the tool.
According to a further embodiment, in a second punching step a second punching tool is used to punch a part of the first main surface adjoining the second groove wall so that the second groove wall and the part of the first main surface adjoining the second groove wall form an overhang. The second punch tool can for example be stamp-like. As a consequence of the second punching step, the punched part of the first main surface adjoining the second groove wall is at a lower height, as seen in a vertical direction from the second main surface of the lead frame, as compared to the part of the first main surface adjoining the first groove wall. According to a further embodiment, the first groove wall can be straight and without any curvature in a direction from the groove opening to the groove bottom, while the second groove wall can have a curvature, in particular a concave curvature, in a direction from the groove opening to the groove bottom. The curvature of the second groove wall can be the result of the second punching step.
Furthermore, in the first punching step at least two grooves of an anchoring structure can be formed by a respective first punching tool. For example, for producing each groove the first punching tool can have a chisel as explained above. Moreover, in the second punching step a respective part of the first main surface adjoining each of the second groove walls of the grooves can be punched. In particular, a
pedestal can be formed by the first punching step, which is then punched in the second punching step to form the
overhangs. Consequently, as explained above, each of the grooves can have a first and a second groove wall and reach into the lead frame at a respective angle, wherein each of the angles is tilted to a direction perpendicular to the first main surface, wherein the second groove walls are at a smaller distance to each other than the first groove walls, and wherein each of the second groove walls and the
respective part of the first main surface adjoining the second groove walls form an overhang.
According to another embodiment, the lead frame can be plated with at least one metal layer. The plating step can be performed preferably after the second punching step. In particular, the lead frame can comprise a bulk material, which can be copper. Before the first and second punching steps, the lead frame can be provided as a bulk metal lead frame like, for instance, a copper lead frame. After the second punching step, one or more metals forming one or more metal layers can be applied to at least one side of the lead frame. In particular, the plating can be performed on the upper side of the lead frame, i.e., the side of the lead frame with the at least one anchoring structure. The one or more metals can be chosen for example from Ag, Al, Au, Ni, Pd and Sn.
According to at least one further embodiment, a semiconductor device comprises a lead frame with at least one anchoring structure according to the embodiments described above.
Furthermore, the semiconductor device can comprise at least one semiconductor chip that is mounted on the first main surface of the lead frame. In particular, the at least one semiconductor chip can be mounted laterally offset to the at least one anchoring structure. Furthermore, the semiconductor device can comprise a plastic material formed over the semiconductor chip and the at least one anchoring structure, wherein the plastic material fills the at least one groove of the at least one anchoring structure.
Due to the shape of the at least one groove of the at least one anchoring structure, in particular due to the overhang- structure of the at least one groove, the plastic material can be held in an interlocking manner, since the overhang of the at least one groove reaches over a part of the plastic material, so that a vertical holding force can be applied to the plastic material by the lead frame. Consequently, the at least one anchoring structure can provide the advantage that the plastic material can be enabled to interlock completely into the groove, leading to an increased gripping power between the lead frame and the plastic material as compared to usual lead frames. Thus, also seepage can be prevented and a prolonged product reliability can be obtained.
Further features, advantages and expediencies will become apparent from the following description of exemplary
embodiments in conjunction with the figures.
Figures 1A to 1G show schematic illustrations of process
steps of a method for manufacturing a lead frame having at least one anchoring structure according to an embodiment,
Figures 2A to 2G show schematic illustrations of process
steps of a method for manufacturing a lead frame having at least one anchoring structure according to another embodiment,
Figures 3A and 3B show schematic illustrations of a
semiconductor device having a lead frame according to another embodiment, and
Figure 4 shows a schematic illustration of a semiconductor device having a lead frame according to another embodiment .
In the figures, elements of the same design and/or function are identified by the same reference numerals. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale .
In the following, specific details are set forth, such as specific features and advantageous effects of a lead frame, a method for producing a lead frame and a semiconductor device having a lead frame, in order to provide a thorough
understanding of embodiments of the invention. It will be apparent to one skilled in the art that embodiments of the invention may be put into practice without these specific details. In other instances, well-known related apparatuses, such as the host of varieties of applicable semiconductor chips, are not described in detail in order to not
unnecessarily obscure embodiments of the invention.
Figures 1A to 1G show schematic illustrations of process steps of a method for manufacturing a lead frame 1 according to an embodiment, the lead frame 1 having at least one anchoring structure 2.
In a first step, as shown in Figure 1A, a lead frame 1 is provided, the lead frame 1 having a first main surface 11 and a second main surface 12 being located remote from the first main surface 11. As depicted, the lead frame 1 is provided with substantially and, preferably, completely flat first and second main surfaces 11, 12, which extend in lateral
directions. The lead frame 1 is preferably provided as a bulk metal lead frame. In an embodiment, the lead frame 1 is a copper lead frame, which can have a preferred thickness of equal to or greater than 0.2 mm. For various semiconductor devices as, for instance, light-emitting devices with a light-emitting semiconductor chip mounted on the lead frame, a lead frame thickness of about 0.3 mm is typically used. Alternatively, the lead frame 1 can also have a greater thickness. The lead frame 1 can be formed mechanically and/or chemically, for example by stamping and/or etching, to have a desired shape. Figure 1A merely shows a part of the lead frame 1. In a further step, which is, as shown in Figures IB and 1C, a first punching step, a first punching tool 91 is used to create at least one groove 20 in the first main surface 11. The first punching tool 91 can be a chisel or a similar tool that is driven into the first main surface 11 at a tilted angle Q with respect to the vertical direction, which is indicated by the dashed line and which is perpendicular to the first main surface 11. The tilted angle Q can preferably be between and including 30° and 60°, for example about 45°. The first punching tool 91 can have, as shown, a triangular cross-section, so that it can produce a triangular groove 20 in the lead frame 1. Since the first punching tool 91 is tilted, the produced triangular groove 20 is also tilted about the same angle as the tool. Consequently, the groove 20 reaches into the lead frame 1 in a direction tilted to a direction perpendicular to the first main surface 11.
Alternatively, the first punching tool can have other shapes, thereby creating grooves with corresponding other shapes.
As shown in Figure 1C, the groove 20 has a first groove wall 21 and a second groove wall 22. Due to the tilted application of the first punching tool 91, the first groove wall 21 and a part of the first main surface 11 adjoining the first groove wall 21 form an edge with an angle of more than 90° and less than 180°, i.e., an obtuse-angled edge, while the second groove wall 22 and a part of the first main surface 11 adjoining the second groove wall 22 form an edge with an angle of more than 0° and less than 90°, i.e., an acute- angled edge. Both edges delimit a groove opening in the first main surface 11. Furthermore, the first and second groove walls 21, 22 adjoin each other at a bottom part of the groove 20. The bottom part is located, in a vertical direction, between the first main surface 11 and the second main surface 12 and can be laterally offset from the groove opening, so that, as seen along the vertical direction, a part of the first main surface 11 can be arranged over a part of the groove 20 and therefore also over a part of the second groove wall 22 and a part of the first groove wall 21. In other words, the second groove wall 22 and a part of the first main surface 11 adjoining the second groove wall 22 can form an overhang .
In order to further pronounce the overhang or, in the case the first punching tool has not yet produced an overhang, in order to produce an overhang, a second punching step is performed, as shown in Figures ID and IE as well as in Figure IF in a magnified view. In the second punching step a second punching tool 92 is used to punch a part of the first main surface 11 adjoining the second groove wall 22 so that the overhang 14 formed by the second groove wall 22 and the part of the first main surface 11 adjoining the second groove wall 22 is formed to be present in a more pronounced manner, thereby forming the anchoring structure 2. The second
punching tool 92 can for example be stamp-like and can be applied along a vertical direction. As a consequence of the second punching step, the punched part of the first main surface 11 adjoining the second groove wall 22 is at a lower height, as seen in a vertical direction from the second main surface 12 of the lead frame 1, as compared to the part of the first main surface 11 adjoining the first groove wall 21. Moreover, as can be seen for example in Figure IF, the first groove wall 21 can be straight and without any curvature in a direction from the groove opening to the groove bottom, while the second groove wall 22 can have a curvature, in particular a concave curvature, in a direction from the groove opening to the groove bottom. The curvature of the second groove wall 22 is the result of the second punching step.
As shown in Figure 1G, the groove 20 of the anchoring
structure 2 has a vertical depth H which can be equal to or less than 1/2 of the thickness of the lead frame 1. The thickness of the lead frame 1 as well as the vertical depth H of the groove can preferably be measured on the side of the first groove wall 21, which is unaffected by the punching steps and therefore also by the anchoring structure 2.
Furthermore, the depth H of the groove 20 can be equal to or more than 1/3 of the thickness of the lead frame 1. Moreover, the opening of the groove 20 in the first main surface 11 can have a lateral width LI of equal to or less than 1/2 of the thickness of the lead frame 1. In other words, the lateral distance between the obtuse-angled edge formed by the first main surface 11 and the first groove wall 21 and the acute- angled edge formed by the first main surface 11 and the second groove wall 22 can be equal to or less than 1/2 of the thickness of the lead frame 1. Furthermore, the lateral width LI of the opening of the groove 20 can be equal to or more than 1/3 of the thickness of the lead frame 1. Due to the second punching step, the part of the first main surface 11 adjoining the second groove wall 22 is at a lower height, as seen in a vertical direction from the second main surface 12 of the lead frame 1, as compared to the part of the first main surface 11 adjoining the first groove wall 21, thereby defining a height difference D, which can be between and including 1/4 to 1/2 of the vertical depth H of the groove 20. Particularly preferably, the height difference D can be about 1/3 of the vertical depth H of the groove 20. In Figure 1G also the angle of the acute-angled edge and the angle b of the obtuse-angled edge are shown, which are as explained in connection with Figures IB and 1C. Moreover, after the second punching step the angle can be smaller than after the first punching step. Furthermore, the
direction T of the groove 20 is indicated, which is tilted to the vertical direction as explained in connection with
Figures IB and 1C.
Figures 2A to 2G illustrate another embodiment of a method for manufacturing a lead frame 1 with at least one anchoring structure 2. In contrast to the method explained in
connection with Figures 1A to 1G, the anchoring structure 2 of this embodiment has two grooves 20, wherein each of the grooves 20 can have one or more features as described before. In particular, the grooves 20 can be formed similarly and/or at the same time, as it becomes apparent from Figures 2B to 2E. In particular, each of the grooves 20 has a first and a second groove wall 21, 22 and reaches into the lead frame 1 along a respective direction, wherein each of the directions is tilted to a direction perpendicular to the first main surface 11, wherein the second groove walls 22 of the two grooves 20 are at a smaller distance to each other than the first groove walls 21, and wherein each of the second groove walls 22 and a respective part of the first main surface 11 adjoining the second groove walls 22 form a respective overhang 14. Consequently, the anchoring structure 2 has a pedestal 16 in the first main surface 11, the pedestal 16 having an upper surface 17 being part of the first main surface 11, and sidewalls being formed by the second groove walls 22. As shown in Figure 2G, the dimensions LI, H and D as well as the angles of the edges of the grooves 20 can be as explained in connection with Figure 1G. Consequently, L3 is preferably equal to LI. The width L2 of the pedestal 16 can preferably be given by LI < L2 < 3><L1. Preferably the width L2 can be equal or substantially equal to 2><L1.
Although in each of the embodiments of Figures 1A to 1G and 2A to 2G only one anchoring structure is shown, also a plurality of anchoring structures 2 can be formed in the lead frame 1. After forming the anchoring structure (s) 2, the lead frame 1 can be plated with at least one metal layer (not shown) in a further method step. The plating step can be performed preferably after the second punching step. The plating can be performed on the upper side of the lead frame 1, i.e., the side of the lead frame 1 with the at least one anchoring structure 2, thereby covering the first main surface 11 and the anchoring structure (s) 2, or additionally also on the second main surface. The at least one metal layer can comprise one or more metals in one or more layers. The one or more metals can be chosen for example from Ag, Al, Au, Ni, Pd and Sn.
Figures 3A and 3B show a semiconductor device 100 having a lead frame 1 as explained in connection with the foregoing embodiments. Figure 3B shows a magnified part of Figure 3A.
By way of example, the lead frame 1 comprises anchoring structures 2 as explained in connection with Figures 2A to 2G .
Furthermore, the semiconductor device 100 comprises at least one semiconductor chip 3 that is mounted on the first main surface 11 of the lead frame 1. In particular, the at least one semiconductor chip 3 is mounted laterally offset to the anchoring structures 2 and, in particular, between the anchoring structures 2. The semiconductor chip 3 can be for example a light-emitting diode chip, so that the
semiconductor device 100 can be a light-emitting device.
Alternatively, also other semiconductor chips can be
possible .
Moreover, the semiconductor device 100 comprises a plastic material 4 formed over the semiconductor chip 3 and the anchoring structures 2. The plastic material 4 can be, for example, PPA, PCT or WEMC or other suitable plastic material. The plastic material 4 can be applied, for example, by a molding process or a casting process. If necessary, a de flashing step, for example in the case of epoxy-based plastic material, can be performed afterwards.
As can be seen in Figures 3A and 3B, the plastic material 4 fills the groove 20 of the anchoring structures 2. Since the grooves 20 form offset-interlocking grooves 20, the anchoring structures 2 can provide a vertical fixation of the plastic material 4 on the lead frame 1, thereby preventing an
undesired delamination of the plastic material 4 from the lead frame 1. The grooves 20 of the anchoring structures 2 can be placed in positions suitable for locking the plastic material 4. This can also mean that the grooves 20 partly or substantially completely surround the at least one
semiconductor chip 3.
Figure 4 shows a further embodiment of a semiconductor device 100 having a lead frame 1 with anchoring structures 2 as explained in connection with the foregoing embodiments. As in the case of the foregoing embodiment, by way of example the lead frame 1 again comprises anchoring structures 2 as explained in connection with Figures 2A to 2G.
As in the foregoing embodiment, the semiconductor device 100 comprises at least one semiconductor chip 3, which can be a light-emitting semiconductor chip and which is mounted on the first main surface 11 of the lead frame 1 between the
anchoring structures 2. In contrast to the foregoing
embodiment, the semiconductor device 100 shown in Figure 4 comprises a plastic material 4 that forms a reflector
housing, which is formed over the anchoring structures 2, but which has a recess accommodating the semiconductor chip 3 and being filled with an encapsulant. The plastic material 4, which can be applied, for example, by a molding process or a casting process, can be, for example, PPA, PCT or WEMC or other suitable plastic material. The encapsulant 5 can also comprise a plastic material, which is transparent for light that can be emitted by the semiconductor chip 3 when
operated. For example, the encapsulant 5 can comprise a silicone and/or an epoxy resin.
Since the plastic material 4 fills the groove 20 of the anchoring structures 2, the anchoring structures 2 can provide a vertical fixation of the reflector housing formed by the plastic material 4 on the lead frame 1, thereby preventing an undesired delamination of the reflector housing from the lead frame 1. Furthermore, it could be possible that the lead frame 1 has one or more anchoring structures for a fixation of the encapsulant 5.
Alternatively or additionally to the features described in connection with the figures, the embodiments shown in the figures can comprise further features described in the general part of the description. Moreover, features and embodiments of the figures can be combined with each other, even if such combination is not explicitly described. The invention is not restricted by the description on the basis of the exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.
Reference numerals
1 lead frame
2 anchoring structure
3 semiconductor chip
4 plastic material
5 encapsulant
11 first main surface
12 second main surface
14 overhang
16 pedestal
17 upper surface
20 groove
21 first groove wall
22 second groove wall
91 first punching tool
92 second punching tool 100 semiconductor device D height difference
H vertical depth
LI, L2 , L3 width
T direction
, b, e angle

Claims

Claims
1. Lead frame (1), having a first main surface (11) and a second main surface (12) being located remote from the fist main surface, and having at least one anchoring structure (2) with at least one groove (20) in the first main surface,
wherein the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface, the at least one groove having a first groove wall (21) and a second groove wall (22), wherein the second groove wall and a part of the first main surface adjoining the second groove wall form an
overhang ( 14 ) .
2. Lead frame according to claim 1, wherein the second
groove wall and the part of the first main surface adjoining the second groove wall enclose an angle of more than 0° and less than 90°.
3. Lead frame according to one of the preceding claims, wherein the first groove wall and the part of the first main surface adjoining the first groove wall enclose an angle of more than 90° and less than 180°.
4. Lead frame according to one of the preceding claims, wherein a part of the first main surface adjoining the second groove wall is at a lower height as compared to a part of the first main surface adjoining the first groove wall, thereby defining a height difference.
5. Lead frame according to the preceding claim, wherein the height difference is between and including 1/4 to 1/2 of a vertical depth of the groove.
6. Lead frame according to one of the preceding claims, wherein the at least one groove reaches into the lead frame in a direction tilted by an angle between and including 30° and 60° to a direction perpendicular to the first main surface.
7. Lead frame according to one of the preceding claims, wherein the anchoring structure has at least two
grooves, each of the grooves having a first and a second groove wall and reaching into the lead frame along a respective direction, wherein each of the directions is tilted to a direction perpendicular to the first main surface, wherein the second groove walls are at a smaller distance to each other than the first groove walls, and wherein each of the second groove walls and a respective part of the first main surface adjoining the second groove walls form an overhang.
8. Lead frame according to the preceding claim, wherein the lead frame has a pedestal (16) in the first main
surface, the pedestal having an upper surface (17) being part of the first main surface and sidewalls being formed by the second groove walls.
9. Lead frame according to one of the two preceding claims, wherein the upper surface of the pedestal is at a lower height as compared to the first main surface adjacent to the first groove walls.
10. Lead frame according to one of the preceding claims, wherein the lead frame has more than one anchoring structure .
11. Lead frame according to one of the preceding claims, wherein the second main surface is substantially flat.
12. Method for manufacturing a lead frame (1) with an
anchoring structure (2), comprising the steps of:
- providing a lead frame having a first main surface (11) and a second main surface (12) being located remote from the fist main surface,
- using a first punching tool (91) in a first punching step to create at least one groove (20) in the first main surface, wherein the at least one groove reaches into the lead frame in a direction tilted to a direction perpendicular to the first main surface, the at least one groove having a first groove wall (21) and a second groove wall (22),
- using a second punching tool (92) in a second punching step to punch a part of the first main surface adjoining the second groove wall, wherein the second groove wall and the part of the first main surface adjoining the second groove wall form an overhang (14) .
13. Method according to the preceding claim, wherein the
lead frame is plated with at least one metal layer after the second punching step.
14. Method according to one of the two preceding claims, wherein, in the first punching step, at least two grooves are formed, wherein each of the grooves has a first and a second groove wall ,
wherein the second groove walls are at a smaller distance to each other than the first groove walls,
wherein, in the second punching step, a respective part of the first main surface adjoining each of the second groove walls is punched,
wherein each of the grooves reaches into the lead frame at a respective angle, wherein each of the angles is tilted to a direction perpendicular to the first main surface, and
wherein each of the second groove walls and the respective part of the first main surface adjoining the second groove walls form an overhang.
15. Semiconductor device (100) comprising
- a lead frame (1) with at least one anchoring structure (2) according to one of claims 1 to 11,
- a semiconductor chip mounted on the first main surface of the lead frame, and
- a plastic material formed over the semiconductor chip and the anchoring structure, wherein the plastic material fills the at least one groove of the anchoring
structure .
PCT/EP2017/081702 2017-12-06 2017-12-06 Lead frame, method for manufacturing a lead frame and semiconductor device with a lead frame WO2019110096A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2017/081702 WO2019110096A1 (en) 2017-12-06 2017-12-06 Lead frame, method for manufacturing a lead frame and semiconductor device with a lead frame

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2017/081702 WO2019110096A1 (en) 2017-12-06 2017-12-06 Lead frame, method for manufacturing a lead frame and semiconductor device with a lead frame

Publications (1)

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US11664328B2 (en) 2018-03-27 2023-05-30 Intel Corporation Warpage compensating RF shield frame

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