Lead frame and method of manufacturing the same

Abstract

A leadframe includes a die pad having a top pad surface and a bottom pad surface opposite the top pad surface, a plurality of leads each having a top lead surface and a bottom lead surface opposite the top lead surface and disposed around the die pad, and a first molding compound disposed between the die pad and each of the leads. The first molding compound exposes the top pad surface of the die pad by covering a portion of a periphery of the top pad surface of the die pad. A method for manufacturing the leadframe is also disclosed.

Description

Technical Field

[0001] This disclosure relates to lead frames, and more particularly to pre-molded lead frames. Background Technology

[0002] There is a current need for semiconductor packages with a very large number of leads but a very small overall size. One component of a semiconductor package is the "lead frame," a conductive metal part with multiple leads for connecting to a semiconductor chip, such that when the semiconductor device is finally integrated into an electronic device, the leads extend from the package to connect to a circuit board. The lead frame will also have one or more bonding strips for assembling the leads into a single structure during the semiconductor manufacturing process.

[0003] The two main methods for producing leadframes are either stamping leadframes from metal strips or etching leadframes using a chemical etching process. In large quantities, chemical etching has so far been the more expensive alternative (given the much higher marginal cost of leadframes produced by chemical etching, compared to the substantial fixed cost of the dies used in stamping). Summary of the Invention

[0004] In some embodiments, this disclosure provides a lead frame comprising: a die pad having a top pad surface and a bottom pad surface opposite to the top pad surface; a plurality of leads, each lead having a top lead surface and a bottom lead surface opposite to the top lead surface and disposed around the die pad; and a first molding material disposed between the die pad and each of the leads. The first molding material exposes the top pad surface of the die pad by covering a portion of the periphery of the top pad surface of the die pad.

[0005] In some embodiments, this disclosure provides a lead frame comprising: a die pad having a top pad surface and a bottom pad surface opposite to the top pad surface; a plurality of leads disposed around the die pad, each of the leads including a top lead surface and a bottom lead surface opposite to the top lead surface; and a first molding material disposed between the die pad and each of the leads, the first molding material including a top molding surface and a bottom molding surface opposite to the top molding surface. In a cross-sectional view, the first molding material comprises an "I" shape by covering a portion of the top die surface and a portion of the top lead surface.

[0006] In some embodiments, this disclosure provides a method for manufacturing a lead frame, the method comprising: providing a die pad and a plurality of leads around the die pad; disposing a first patterned sacrificial layer above a top pad surface of the die pad and a top lead surface of each of the leads; disposing a molding material between the die pad and the plurality of leads and above the first patterned sacrificial layer; removing the molding material until the first patterned sacrificial layer is exposed; and removing the first patterned sacrificial layer above the top pad surface and the top lead surface. Attached Figure Description

[0007] Various aspects of this disclosure can be readily understood from the following detailed description, which is read in conjunction with the accompanying drawings. It should be noted that the various features may not necessarily be drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily increased or decreased.

[0008] Figure 1A A cross-sectional view of a lead frame according to some embodiments of the present disclosure is shown.

[0009] Figure 1B A cross-sectional view of a lead frame according to some embodiments of the present disclosure is shown.

[0010] Figure 1C A cross-sectional view of a lead frame according to some embodiments of the present disclosure is shown.

[0011] Figure 2A A cross-sectional view of a lead frame bar or matrix according to some embodiments of the present disclosure is shown.

[0012] Figure 2B A cross-sectional view of a lead frame bar or matrix according to some embodiments of the present disclosure is shown.

[0013] Figure 2C A cross-sectional view of a lead frame bar or matrix according to some embodiments of the present disclosure is shown.

[0014] Figures 3A to 3F Cross-sectional views of lead frame bars or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations.

[0015] Figures 4A to 4F Cross-sectional views of lead frame bars or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations.

[0016] Figures 5A to 5F Cross-sectional views of lead frame bars or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations.

[0017] Figure 6 A top view of a lead frame according to some embodiments of the present disclosure is shown.

[0018] Figures 7A to 7E A top view of a single lead frame unit according to some embodiments of the present disclosure is shown during various manufacturing operations. Detailed Implementation

[0019] Throughout the accompanying drawings and detailed description, the same reference numerals are used to indicate the same or similar components. Embodiments of this disclosure will be readily understood from the following detailed description taken in conjunction with the accompanying drawings.

[0020] Spatial descriptions such as "above," "below," "upward," "left side," "right side," "downward," "top," "bottom," "vertical," "horizontal," "side," "higher," "lower," "upper part," "above," and "below" are used to specify the orientation of a component or group of components or a plane of a component or group of components with respect to the orientation of said one or more components, as shown in the relevant figures. It should be understood that the spatial descriptions used herein are for illustrative purposes only, and actual embodiments of the structures described herein can be arranged in space in any orientation or manner, provided that such arrangement does not depart from the advantages of the embodiments of this disclosure.

[0021] One type of pre-molded leadframe (PMLF) has a molded sidewall structure surrounding the die pad on the lead pad. The sidewall structure helps limit adhesive overflow and facilitates the application of a metal or plastic cap over the semiconductor die. However, the molded sidewall structure occupies working areas, such as the lead bonding or die bonding areas, thus imposing more constraints on the die assembly. Furthermore, the molded sidewall structure must be formed using a dedicated mold with specific dimensions. When the PMLF design dimensions change or a new PMLF design becomes available, the mold must be changed or modified, thereby increasing the PMLF manufacturing cost.

[0022] Another type of PMLF has a flat surface without its corresponding molded sidewall structure. In a flat-surface PMLF, the working area (e.g., the wire bonding area or the die bonding area) can be increased, but the molding material connecting the die pads and the wire pads is prone to delamination from the metal portion of the PMLF, thereby reducing product reliability.

[0023] This disclosure provides a PMLF without molded sidewall structures. The PMLF of this disclosure uses a plate mold for molding operations, thus eliminating the need for modified mold sleeves when dimensions or designs change. The working area is increased, and manufacturing costs are reduced. The molding material of the PMLF of this disclosure extends above the periphery of the die-bonding region and the periphery of the wire-bonding region, thereby providing better handling of the PMLF strip template compared to its flat-surface PMLF counterpart. Furthermore, the thicker molding material covering the periphery of the wire-bonding region and the die-bonding region acts as a mold lock, thereby improving the reliability of the PMLF product.

[0024] refer to Figure 1A , Figure 1A A cross-sectional view of a lead frame 10A according to some embodiments of the present disclosure is shown. The lead frame 10A includes a die pad 100 and a plurality of lead pads 101 surrounding the die pad 100. In some embodiments, the die pad 100 is configured to hold a semiconductor die, and the lead pads 101 are connected to the semiconductor die using wire bonding. The die pad 100 has a top pad surface 100A and a bottom pad surface 100B opposite to the top pad surface 100A. By design, the top pad surface 100A is wider than the bottom pad surface 100B, as shown, and the top pad surface 100A is a surface for receiving the semiconductor die. Each lead pad of the lead pads 101 has a top lead surface 101A and a bottom lead surface 101B. By design, the top lead surface 101A is wider than the bottom lead surface 101B, as shown, and the top lead surface 101A is a surface for receiving wire bonding. In a cross-sectional view, the grain pad 100 is surrounded by two lead pads 101; however, in a top view, as... Figure 6 The solution is that the die pad 100 can be surrounded by two or more lead pads 101 from all sides of the die pad 10.

[0025] The molding material 105 is positioned between the die pad 100 and the lead pad 101, acting as a lead frame structure reinforcing agent. The molding material 105 fills the space between each lead pad in the die pad 100 and the lead pad 101. The molding material 105 has a top molding surface 105A and a bottom molding surface 105B opposite to the top molding surface 105A. The top molding surface 105A protrudes from the top pad surface 100A by a height difference H1 and extends above the periphery of the top pad surface 100A. Conversely, the top molding surface 105A protrudes from the top lead surface 101A by a height difference H1 and extends above the periphery of the top lead surface 101A.

[0026] In some embodiments, molding material 105 surrounds the die pad 100 from all sides of the die pad 100, a coverage area 100A2 on the top pad surface 100A of the die pad 100 is encapsulated by molding material 105, and a receiving area 100A1 for the semiconductor die on the top pad surface 100A of the die pad 100 is exposed from molding material 105. Alternatively, molding material 105 above the top pad surface 100A defines the receiving area 100A1 of the die pad 100. The area of ​​the receiving area 100A1 may be smaller than the area of ​​the semiconductor die to be placed thereon. The conductive adhesive used to attach the semiconductor die to the die pad 100 can be confined by the height difference H1 between the molding material 105 and the top pad surface 100A and will not overflow into the area outside the receiving area 100A1. In addition, a portion of the molding material 105 extending above the covering area 100A2 on the top liner surface 100A is used to support the semiconductor die to be attached and to prevent the semiconductor die from tilting during the bonding operation.

[0027] like Figure 1A As shown, from a cross-sectional perspective, the molding material 105 is I-shaped. The upper horizontal portion of the I-shape covers the coverage area 100A2 of the top pad surface 100A and the coverage area 101A2 of the top lead surface 101A, and the lower horizontal portion of the I-shape covers the recessed sidewall 100C connecting the top pad surface 100A and the bottom pad surface 100B, as well as the recessed sidewall 101C connecting the top lead surface 101A and the bottom lead surface 101B. Compared to a flat PMLF, besides the larger thickness of the molding material 105, the I-shape of the molding material 105 acts as a mold lock, thereby improving the reliability of the PMLF 10A of this disclosure.

[0028] In some embodiments, molding material 105 surrounds lead pad 101 from all sides of lead pad 101, a coverage area 101A2 on the top lead surface 101A of lead pad 101 is enclosed by molding material 105, and a receiving area 101A1 for lead engagement is exposed from molding material 105. Note that another molding material 105' is positioned above the periphery of lead pad 101. In some embodiments, molding material 105' may have sidewalls coplanar with the sidewalls of lead pad 101. Alternatively, molding material 105 and molding material 105' above the top lead surface 101A define the receiving area 101A1 of lead pad 101. The coverage of molding material 105 and molding material 105' can be adjusted according to the area required for lead engagement on the top lead surface 101A. The portions of molding material 105 and molding material 105' located above the coverage area 101A2 of the top lead surface 101A enhance the structural strength of the lead frame 10A. In some embodiments, the molding material 105 has a height difference H1 between the top molding surface 105A and the top lead surface 101A, and the molding material 105' has a substantially the same height difference H1 between the top molding surface 105A' and the top lead surface 101A.

[0029] In some embodiments, due to the release of the strip after the molding operation, the bottom molding surface 105B of the molding material 105 and the bottom liner surface 100B have a height difference H2, as disclosed herein. Figure 2A As described by the lieutenant general.

[0030] In some embodiments, a pre-plated frame (PPF) surface layer 103 is formed over the top pad surface 100A, the bottom pad surface 100B, the top lead surface 101A, and the bottom lead surface 101B. In some embodiments, a nickel-palladium-gold ultrathin film is used for the PPF surface layer 103 of the semiconductor lead frame. Furthermore, the PPF surface layer 103 may be formed on the side surfaces connecting the top pad side 100A and the bottom pad surface 100B, and on the side surfaces connecting the top lead surface 101A and the bottom lead surface 101B. In other words, the PPF surface layer 103 can be observed between the molding material 105 and the die pad 100, and between the molding material 105 and each lead pad in the lead pad 101. In some embodiments, an additional Ag plating layer is formed above the aforementioned surfaces to facilitate lead bonding.

[0031] refer to Figure 1B , Figure 1BA cross-sectional view of a lead frame 10B according to some embodiments of the present disclosure is shown. The lead frame 10B is similar to the lead frame 10A, except that an additional notch 101W is formed at the corner of each of the plurality of lead pads 101. A PPF facet layer is coated on the surface of the notch 101W. The notch 101W can be used to provide better wettability for soldering materials commonly used in automotive-related electronic applications. In some embodiments, for example, a sacrificial layer is filled in the notch 101W before the PMLF 10B is bonded to a ceramic substrate.

[0032] like Figure 1B As shown, from a cross-sectional perspective, the molding material 105 is I-shaped. The upper horizontal portion of the I-shape covers the coverage area 100A2 of the top pad surface 100A and the coverage area 101A2 of the top lead surface 101A, and the lower horizontal portion of the I-shape covers the recessed sidewall 100C connecting the top pad surface 100A and the bottom pad surface 100B, as well as the recessed sidewall 101C connecting the top lead surface 101A and the bottom lead surface 101B. Compared to a flat PMLF, besides the larger thickness of the molding material 105, the I-shape of the molding material 105 acts as a mold lock, thereby improving the reliability of the PMLF 10B of this disclosure.

[0033] Figure 1C A cross-sectional view of a lead frame 10C according to some embodiments of the present disclosure is shown. The lead frame 10C is similar to the lead frame 10B, except that the top molded surface 105A is substantially coplanar with the top pad surface 100A and the top lead surface 101A, and the bottom molded surface 105B protrudes beyond a height difference H3 from the bottom pad surface 100B and the bottom lead surface 101B due to the removal of a patterned sacrificial layer above the bottom pad surface 100B and the bottom lead surface 101B. An additional notch 101W is formed at the corner of each of the plurality of lead pads 101. A PPF topcoat is coated on the surface of the notch 101W. The notch 101W can be used to provide better wettability for soldering materials commonly used in automotive-related electronic applications. In some embodiments, for example, before bonding the PMLF 10C to a ceramic substrate, a sacrificial layer is filled in the notch 101W, as shown in the figure below. Figure 2C Further details are provided below.

[0034] refer to Figure 2A , Figure 2AA cross-sectional view of a lead frame strip or matrix 20A according to some embodiments of the present disclosure is shown. The lead frame strip or matrix 20A illustrates a stage prior to single-cutting of the lead frame, for example, with the single-cut point marked by dashed lines above one of the lead pads 101. After single-cutting of the lead frame, the strip 202 attached to the bottom pad surface 100B, the bottom lead surface 101B, and the bottom molded surface 105B is removed. Figure 2A As shown, since the strip 202 is made of a deformable material such as a polymer, a portion of the strip 202 can be deformed to extend a height difference H2' towards the top liner surface 100A and the top lead surface 101A before the molding material 105 is injected. After the strip 202 is removed, a height difference H2 remains between the bottom molding surface 105B and the bottom liner surface 100B, as previously described. Figure 1A As shown in the image.

[0035] refer to Figure 2B , Figure 2B A cross-sectional view of a lead frame strip or matrix 20B according to some embodiments of the present disclosure is shown. The lead frame strip or matrix 20B shows a stage prior to single-cutting of the lead frame, for example, with the single-cut point marked by dashed lines above one of the lead pads 101. After single-cutting of the lead frame, the strip 202 attached to the bottom pad surface 100B, the bottom lead surface 101B, and the bottom molded surface 105B is removed. Figure 2B As shown, since the strip 202 is made of a deformable material such as a polymer, a portion of the strip 202 can be deformed to extend a height difference H2' towards the top liner surface 100A and the top lead surface 101A before the molding material 105 is injected. After the strip 202 is removed, a height difference H2 remains between the bottom molding surface 105B and the bottom liner surface 100B, as previously described. Figure 1B As shown in the diagram. It should also be noted that a notch 101W filled with patterned sacrificial material 201 was applied prior to the application of the band 202. Although in Figure 2B Not shown, but in some embodiments, in addition to deforming along the recessed sidewalls 100C, 101C of the grain pad 100 and the lead pad 101, the strip 202 may also deform along the sidewall of the notch 101W to create a height difference (not shown) between the bottom of the patterned sacrificial material 201 and the bottom lead surface 101B after the strip 202 is removed.

[0036] refer to Figure 2C , Figure 2CA cross-sectional view of a lead frame strip or matrix 20C according to some embodiments of the present disclosure is shown. The lead frame strip or matrix 20C shows a stage prior to single-cutting of the lead frame, for example, with the single-cut point marked by dashed lines above one of the lead pads 101. No tape is applied above the bottom pad surface 100B or the bottom lead surface 101B prior to single-cutting. Figure 2C As shown, the bottom molding surface 105B protrudes from the bottom pad surface 100B or the bottom lead surface 101B by a height difference H3'. The height difference H3' is associated with the thickness of the patterned sacrificial material 201 applied above the bottom pad surface 100B and the bottom lead surface 101B prior to the molding operation. The patterned sacrificial material 201 may also fill one or more recesses 101W at the corners of the lead pad 101. In some embodiments, the height difference H3' between the bottom molding surface 105B and the bottom pad surface 100B is substantially the same as the thickness of the patterned sacrificial material 201 applied above the bottom pad surface 100B.

[0037] Figures 3A to 3F Cross-sectional views of lead frame strips or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations. Figure 3A In the process, a copper plate is etched with a lead frame pattern, including die pads 100 and lead pads 101. Die pads 100 can be surrounded by multiple lead pads 101. As described above, after the etching operation, the top pad surface 100A is wider than the bottom pad surface 100B, and the top lead surface 101A is wider than the bottom lead surface 101B. Figure 3B In this process, a PPF surface layer 103 is electroplated over the top pad surface 100A, the bottom pad surface 100B, the top lead surface 101A, the bottom lead surface 101B, and the sidewalls connecting the above surfaces. Optionally, an Ag film is electroplated over the above surfaces to promote lead bonding.

[0038] exist Figure 3CIn this process, a patterned sacrificial layer 200 is formed over the top pad surface 100A of the die pad 100 and the top lead surface 101A of the lead pad 101. In some embodiments, the patterned sacrificial layer 200 covers the central portion of the die pad 100. In some embodiments, prior to a single-cut operation, the patterned sacrificial layer 200 covers a portion of the lead pad 101 and exposes another portion of the lead pad 101. In some embodiments, the patterned sacrificial layer 200 covers the die bonding region and the lead bonding region designed for the leadframe. In some embodiments, the patterned sacrificial layer 200 may be made of a patternable material such as photoresist. In some embodiments, the patterned sacrificial layer 200 may be applied by stencil printing or screen printing. A curing operation or a soft bake operation may be performed after the formation of the patterned sacrificial layer 200.

[0039] exist Figure 3D In the process, prior to the overmolding operation, such as encapsulating die pad 100 and lead pad 101, a tape 202 is attached to the bottom pad surface 100B and the bottom lead surface 101B. After the molding operation, the top pad surface 100A, the top lead surface 101A, and the patterned sacrificial layer 200 are covered with molding material 105M. The molding material 105M has an upper surface 105A', which is higher than the upper surface of the patterned sacrificial layer 200. The tape 202 is applied to prevent the molding material 105M from overflowing onto the bottom pad surface 100B and / or the bottom lead surface 101B. As mentioned above, a portion of the tape 202 can be deformed to extend a height difference H2' towards the top pad surface 100A and the top lead surface 101A before the molding material 105M is injected. Figure 3D (Not shown in the image).

[0040] exist Figure 3E In this process, the molding material 105A' is ground until the upper surface of the patterned sacrificial layer 200 is exposed. After the grinding operation, the molding material 105 is obtained with the molding surface 105A substantially coplanar with the upper surface of the patterned sacrificial layer 200. In some embodiments, the grinding operation continues to thin the molding material 105A', thereby ensuring that the patterned sacrificial layer 200 is fully exposed. Figure 3F In this process, the exposed patterned sacrificial layer 200 is removed through appropriate cleaning operations, thereby exposing the receiving area 100A1 on the top pad surface 100A and the receiving area 101A1 on the top lead surface 101A. Note that the molding material 105 defines the receiving area 100A1, and the molding material 105 and the molding material 105' together define the receiving area 101A1.

[0041] Figures 4A to 4F Cross-sectional views of lead frame strips or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations. Figure 4A In this process, a copper plate is etched with a lead frame pattern, including die pads 100 and lead pads 101. The die pads 100 can be surrounded by a plurality of lead pads 101. As described above, after the etching operation, the top pad surface 100A is wider than the bottom pad surface 100B, and the top lead surface 101A is wider than the bottom lead surface 101B. Figure 4A As shown, a notch 101W is formed, for example, by etching at the corner of the lead pad 101 or at the bottom lead surface 101B. Figure 4B In this process, a PPF surface layer 103 is electroplated over the top pad surface 100A, the bottom pad surface 100B, the top lead surface 101A, the bottom lead surface 101B, the sidewalls connecting the above surfaces, and the recess 101W. Optionally, an Ag film is electroplated over the above surfaces to promote lead bonding.

[0042] exist Figure 4C In this process, a patterned sacrificial layer 200 is formed over the top pad surface 100A of the die pad 100 and the top lead surface 101A of the lead pad 101. In some embodiments, the patterned sacrificial layer 200 covers the central portion of the die pad 100. In some embodiments, prior to a single-cut operation, the patterned sacrificial layer 200 covers a portion of the lead pad 101 and exposes another portion of the lead pad 101. In some embodiments, the patterned sacrificial layer 200 covers the die bonding region and the lead bonding region designed for the lead frame. In some embodiments, the patterned sacrificial layer 200 may be made of a patternable material such as photoresist. In some embodiments, the patterned sacrificial layer 200 may be applied by stencil printing or screen printing. A curing operation or a soft baking operation may be performed after the formation of the patterned sacrificial layer 200. Subsequently, the patterned sacrificial layer 201 is formed in a notch 101W on the bottom lead surface 101B of the lead pad 101. In some embodiments, the patterned sacrificial layer 201 may be made of a patternable material such as photoresist. In some embodiments, the patterned sacrificial layer 201 may be applied by stencil printing or screen printing. A curing operation or a soft baking operation may be performed after the patterned sacrificial layer 201 is formed.

[0043] exist Figure 4DIn the process, prior to the overmolding operation, such as encapsulating die pad 100 and lead pad 101, a tape 202 is attached to the bottom pad surface 100B, the bottom lead surface 101B, and the patterned sacrificial layer 201. After the molding operation, the top pad surface 100A, the top lead surface 101A, and the patterned sacrificial layer 200 are covered with molding material 105M. The molding material 105M has an upper surface 105A', which is higher than the upper surface of the patterned sacrificial layer 200. The tape 202 is applied to prevent the molding material 105M from overflowing onto the bottom pad surface 100B and / or the bottom lead surface 101B. As mentioned above, a portion of the tape 202 can be deformed to extend a height difference H2' towards the top pad surface 100A and the top lead surface 101A before the molding material 105M is injected. Figure 4D (Not shown in the image).

[0044] exist Figure 4E In this process, the molding material 105A' is ground until the upper surface of the patterned sacrificial layer 200 is exposed. After the grinding operation, the molding material 105 is obtained with the molding surface 105A substantially coplanar with the upper surface of the patterned sacrificial layer 200. In some embodiments, the grinding operation continues to thin the molding material 105A', thereby ensuring that the patterned sacrificial layer 200 is fully exposed. Figure 4F In this process, the exposed patterned sacrificial layer 200 is removed through appropriate cleaning operations, thereby exposing the receiving area 100A1 on the top pad surface 100A and the receiving area 101A1 on the top lead surface 101A. Note that the molding material 105 defines the receiving area 100A1, and the molding material 105 and the molding material 105' together define the receiving area 101A1.

[0045] exist Figure 4F Subsequently, a semiconductor die (not shown) can be attached to the receiving area 100A1 of the top pad surface 100A, and the lead frame strip or matrix can be diced along the dicing point (not shown). A patterned sacrificial layer 201 filling the notch 101W prevents the formation of metal burrs during the dicing operation. After the lead frame is diced, the patterned sacrificial layer 201 can be removed from the notch 101W. For automotive-related electronic applications, solder paste can then be applied to fill the notch 101W and bond the lead frame with the semiconductor die to another carrier.

[0046] Figures 5A to 5F Cross-sectional views of lead frame strips or matrices according to some embodiments of the present disclosure are shown during various manufacturing operations. Figure 5AIn this process, a copper plate is etched with a lead frame pattern, including die pads 100 and lead pads 101. The die pads 100 can be surrounded by a plurality of lead pads 101. As described above, after the etching operation, the top pad surface 100A is wider than the bottom pad surface 100B, and the top lead surface 101A is wider than the bottom lead surface 101B. Figure 5A As shown, for example, a notch 101W is formed at the corner of the lead pad 101 or on the bottom lead surface 101B by an etching operation. Figure 5B In this process, a PPF surface layer 103 is electroplated over the top pad surface 100A, the bottom pad surface 100B, the top lead surface 101A, the bottom lead surface 101B, the sidewalls connecting the above surfaces, and the recess 101W. Optionally, an Ag film is electroplated over the above surfaces to promote lead bonding.

[0047] exist Figure 5C In this process, the lead frame is flipped up and down, and a patterned sacrificial layer 201 is formed in the notch 101W on the bottom lead surface 101B of the lead pad 101. In some embodiments, the patterned sacrificial layer 201 may be made of a patternable material such as photoresist. In some embodiments, the patterned sacrificial layer 201 may be applied by stencil printing or screen printing. A curing operation or a soft baking operation may be performed after the patterned sacrificial layer 201 is formed. In some embodiments, the patterned sacrificial layer 201 is also applied to the bottom pad surface 100B and the bottom lead surface 101B. In some embodiments, the patterned sacrificial layer 201 completely covers the bottom pad surface 100B and the bottom lead surface 101B.

[0048] exist Figure 5D In the process, an overmolding operation encapsulates the die pad 100 and the lead pad 101 from the bottom pad surface 100B and the bottom lead surface 101B. After the molding operation, the bottom pad surface 100B, the bottom lead surface 101B, and the patterned sacrificial layer 201 are covered by molding material 105M. The molding material 105M has an upper surface 105B', which is higher than the upper surface of the patterned sacrificial layer 201.

[0049] exist Figure 5E In this process, the molding material 105B' is ground until the upper surface of the patterned sacrificial layer 201 is exposed. After the grinding operation, the molding material 105 has a molding surface 105B that is substantially coplanar with the surface of the patterned sacrificial layer 201. In some embodiments, the grinding operation continues to thin the molding material 105A', thereby ensuring that the patterned sacrificial layer 201 is fully exposed. Figure 5FIn the middle, the lead frame is flipped up and down again to obtain a flat profile on the top pad surface 100A and the top lead surface 101A, while having a patterned sacrificial layer 201 with a filled notch 101W and disposed above the bottom pad surface 100B and the bottom lead surface 101B.

[0050] exist Figure 5F Subsequently, a semiconductor die (not shown) can be attached to the top pad surface 100A, and leadframe strips or matrices can be diced along the dicing points (not shown). A patterned sacrificial layer 201 filling the notch 101W prevents the formation of metal burrs during the dicing operation. After the leadframe is diced, the patterned sacrificial layer 201 can be removed from the notch 101W. For automotive-related electronic applications, solder paste can then be applied to fill the notch 101W and bond the leadframe with the semiconductor die to another carrier.

[0051] Figure 6 A top view of a lead frame according to some embodiments of the present disclosure is shown. References Figure 1A and Figure 6 The die pad 100 is surrounded, for example, by a plurality of lead pads 101 from its four sides. A molding material 105 covers the periphery of the die pad 100 and the periphery of the lead pads 101 adjacent to the die pad 100. A molding material 105' covers the periphery of the lead pads 101 away from the die pad 100. From a top view perspective, the molding materials 105 and 105' are connected by a molding material 105" which also covers a portion of the periphery of the lead pads 101.

[0052] Figures 7A to 7E A top view of a single lead frame unit according to some embodiments of the present disclosure during various manufacturing operations is shown. Figure 7A In this process, a copper plate is etched to form the grain pad 100, the lead pad 101, and the support lead 101'. Figure 7B In this process, a patterned sacrificial layer 200 is formed to cover the central portion of the grain pad 100 and a portion of the lead pad 101. Figure 7C In this process, molding material 105A' is applied over the patterned sacrificial layer 200 and encapsulates the entire lead frame unit. Figure 7D In the process, the grinding molding material 105A' is used to expose the patterned sacrificial layer 200 while keeping the grain pad 100 and lead pad 101 covered. Figure 7E In this process, the patterned sacrificial layer 200 is removed to expose a portion of the die pad 100 and lead pad 101. Figure 6 and Figure 1AThe positions of molding material 105 and molding material 105' are shown and described, and can be referenced to these positions.

[0053] As used herein and unless otherwise defined, the terms “substantially,” “basically,” “approximately,” and “about” are used to describe and explain small variations. When used in conjunction with an event or situation, the terms may cover instances where the event or situation occurs precisely as well as instances where the event or situation approximately occurs. For example, when used in conjunction with a numerical value, the terms may cover a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. The term “substantially coplanar” may refer to two surfaces whose positional difference along the same plane is within a few micrometers, such as within 40 μm, 30 μm, 20 μm, 10 μm, or 1 μm.

[0054] As used herein, unless the context clearly indicates otherwise, the singular forms “a / an” and “the” may include plural referents. In the description of some embodiments, the description of another component disposed “on” or “above” a component may cover the case where the preceding component is directly on (e.g., in physical contact with) the following component, as well as the case where one or more intermediate components are positioned between the preceding and following components.

[0055] While this disclosure has been described and illustrated with reference to specific embodiments thereof, such descriptions and illustrations are not limiting. Those skilled in the art will understand that various changes may be made and equivalents may be substituted without departing from the spirit and scope of this disclosure as defined by the claims. Illustrations may not necessarily be drawn to scale. There may be differences between artistic representations in this disclosure and actual devices due to manufacturing processes and tolerances. Other embodiments of this disclosure may exist that are not specifically shown. The description and drawings should be considered illustrative rather than limiting. Modifications may be made to adapt particular circumstances, materials, composition, methods, or processes to the objectives, spirit, and scope of this disclosure. All such modifications are intended to fall within the scope of the appended claims. While the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or rearranged to form equivalent methods without departing from the teachings of this disclosure. Therefore, the order and grouping of operations are not limiting unless expressly indicated herein.

Claims

1. A lead frame, comprising: A grain liner having a top liner surface and a bottom liner surface opposite to the top liner surface; Multiple leads, each having a top lead surface and a bottom lead surface opposite to the top lead surface, and disposed around the grain pad; as well as A first molding material is disposed between the die pad and each of the leads, wherein an upper horizontal portion of the first molding material covers a portion of the periphery of the top pad surface of the die pad to expose the surface of the die bonding region of the top pad surface of the die pad, and the upper horizontal portion also covers a portion of the periphery of the top lead surface and exposes the surface of the lead bonding region of the top lead surface.

2. The lead frame of claim 1, wherein the first molding material surrounds the die pad from all sides of the die pad and defines a first receiving region above the top pad surface of the die pad, the first receiving region being exposed from the first molding material to serve as the die bonding region.

3. The lead frame of claim 1, wherein the top pad surface of the die pad is larger than the bottom pad surface of the die pad, and the first molding material fills the space between the die pad and each of the leads.

4. The lead frame of claim 1, wherein the top pad surface of the die pad is larger than the bottom pad surface of the die pad, the top lead surface is larger than the bottom lead surface, and the first molding material fills the space between the die pad and each of the leads.

5. The lead frame of claim 1, wherein a pre-plated frame surface layer is formed above the top lead surface, and the first molding material contacts the pre-plated frame surface layer and covers a portion of the periphery of the top lead surface to expose the surface of the lead bonding region of the top lead surface.

6. The lead frame of claim 5, wherein the top lead surface is larger than the bottom lead surface, and the first molding material fills the space between the grain pad and each of the leads.

7. The lead frame of claim 1, wherein each of the leads includes a notch at the surface of the bottom lead, and wherein a patterned sacrificial layer is disposed in the notch.

8. The lead frame of claim 1, wherein the first molding material comprises a top molding surface and a bottom molding surface opposite to the top molding surface, and the lead frame further comprises a height difference between the top molding surface and the top pad surface.

9. The lead frame according to claim 8, further comprising: The height difference between the bottom molded surface and the bottom liner surface.

10. The lead frame according to claim 1, further comprising: A second molding material is disposed adjacent to the top lead surface, wherein the second molding material and the first molding material define a second receiving area above the top lead surface.

11. A lead frame comprising: A grain liner having a top liner surface and a bottom liner surface opposite to the top liner surface; Multiple leads are disposed around the die pad, each of the leads including a top lead surface and a bottom lead surface opposite to the top lead surface; as well as A first molding material is disposed between the die pad and each of the leads, the first molding material including a top molding surface and a bottom molding surface opposite to the top molding surface. In a cross-sectional view, the first molding material comprises an "I" shape by covering a portion of the periphery of the top liner surface and a portion of the periphery of the top lead surface. The upper horizontal portion of the "I" shape covers the portion of the periphery of the top pad surface and exposes the surface portion of the grain bonding region of the top pad surface, and the upper horizontal portion covers the portion of the periphery of the top lead surface and exposes the surface of the lead bonding region of the top lead surface.

12. The lead frame according to claim 11, further comprising: The height difference between the top molded surface and the top pad surface is used to limit the conductive adhesive that attaches the semiconductor die to the die pad.

13. The lead frame according to claim 12, further comprising: The height difference between the bottom molded surface and the bottom liner surface.

14. The lead frame of claim 11, wherein the first molding material defines a first receiving area above the top liner surface by covering the periphery of the top liner surface, wherein a pre-plated frame surface layer is formed above the top liner surface, and the first molding material contacts the pre-plated frame surface layer.

15. The lead frame of claim 11, wherein the first molding material surrounds the lead from all sides of the lead and defines a second receiving region above the top lead surface of each lead in the lead, the second receiving region being exposed from the first molding material to serve as the lead engagement region.

16. The lead frame of claim 15, wherein the periphery of the top lead surface outside the second receiving region is encapsulated by the first molding material.

17. A method for manufacturing a lead frame, comprising: Provide a grain pad and a plurality of leads around the grain pad; A first patterned sacrificial layer is disposed above the top pad surface of the die pad and the top lead surface of each of the leads, wherein the first patterned sacrificial layer covers a portion of the top pad surface and exposes another portion of the top pad surface, and the first patterned sacrificial layer also covers a portion of the top lead surface and exposes another portion of the top lead surface; Molding material is placed between the grain pads and the plurality of leads and above the first patterned sacrificial layer; Remove the molding material until the first patterned sacrificial layer is exposed; as well as Remove the first patterned sacrificial layer above the top pad surface and the top lead surface to expose the surface of the die bonding region of the top pad surface of the die pad and the surface of the lead bonding region of the top lead surface.

18. The method of claim 17, wherein each of the leads has the top lead surface and the bottom lead surface, and a second patterned sacrificial layer is disposed in a notch at the bottom lead surface.

19. The method of claim 17, wherein after the molding material is placed, the upper surface of the molding material is higher than the upper surface of the first patterned sacrificial layer, and after the molding material is removed, the upper surface of the obtained molding material is coplanar with the upper surface of the first patterned sacrificial layer.

20. The method of claim 17, further comprising: Before placing the molding material, attach tape to the bottom lead surface and the bottom liner surface.

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