Leadframe design ready for die attach adhesive

Abstract

The integrated circuit package includes a die attach pad (503) and a number of conductors (504) formed from a leadframe material (501). A cavity is formed in the top surface (502) of the die attach pad (505). A die attach adhesive (507) is disposed within the cavity (506). A top surface (507a) of the die attach adhesive (507) is flush with the top surface (502a) of the die attach pad (505). A semiconductor die is mounted on the die attach pad (505) using the die attach adhesive (507). The semiconductor die is electrically connected to the number of conductors (504) via a set of bond wires. A bottom surface of the semiconductor die is flush with the top surface (502a) of the die attach pad. A molding compound covers a portion of the leadframe, the semiconductor die, and the set of bond wires.

Description

[Technical field]

[0001] A semiconductor package is a metal, plastic, glass, or ceramic enclosure that contains one or more semiconductor dies or components. It is well known that packaging plays an important role in the operation and performance of components such as semiconductor integrated circuits (ICs) or dies. A conventional method of manufacturing a semiconductor die package typically involves attaching a semiconductor die to a substrate having a plurality of electrical conductors or conductive fingers, which includes the appropriate application of a selected die attach material. The selected die attach material is applied by the device manufacturer to a substrate such as a lead frame provided by a separate vendor. The die attach material is cured, followed by wire bonding the bond pads of the semiconductor die to the conductors of the substrate using bond wires. An encapsulation material is applied to the structure covering at least a portion of the die and at least a portion of the substrate including the bond wires. Summary of the Invention

[0002] An integrated circuit package includes a leadframe with a pre-applied die attach adhesive, replacing the traditional epoxy dispensed die pad. In one example, a die attach film is attached to the leadframe after etching via a tape lamination process, such as using a pre-cut tape design based on the die pad dimensions. In another example, adhesive is applied to the leadframe, such as by spraying or screen printing, onto a cavity created via an additive etching process, allowing the adhesive to be flush with the die pad.

[0003] In one example, a semiconductor package includes a leadframe including a die attach pad and a plurality of conductors. A cavity is formed in a top surface of the die attach pad. A die attach material is disposed within the cavity. A semiconductor die is mounted on the die attach pad with the die attach material. The semiconductor die is electrically connected to the plurality of conductors via a set of bond wires. A molding structure covers a portion of the leadframe, the semiconductor die, and the set of bond wires. A top surface of the die attach material may be coplanar with a top surface of the die attach pad. A bottom surface of the semiconductor die may be coplanar with a top surface of the die attach pad. An edge of the die attach material may be located on the top surface of the die attach pad adjacent all sides of the semiconductor die.

[0004] In another example, an integrated circuit package includes a die attach pad and a plurality of conductors formed from a leadframe material. A cavity is formed in a top surface of the die attach pad. A die attach adhesive is disposed within the cavity. A top surface of the die attach adhesive is coplanar with the top surface of the die attach pad. A semiconductor die is mounted on the die attach pad with the die attach adhesive. The semiconductor die is electrically connected to the plurality of conductors via a set of bond wires. A bottom surface of the semiconductor die is coplanar with the top surface of the die attach pad. A molding compound covers a portion of the leadframe, the semiconductor die, and the set of bond wires. An edge of the die attach material may be located on the top surface of the die attach pad adjacent all sides of the semiconductor die.

[0005] An exemplary method for manufacturing a semiconductor package includes a plurality of steps, including providing a leadframe having a plurality of die attach pads, each die attach pad having a top surface with a pre-deposited layer of die attach material, adhering a semiconductor device to each die attach pad with the die attach material, attaching wire bonds from contacts on each semiconductor device to leads on the leadframe, and covering at least a portion of the semiconductor device, the die attach pad, the die attach material, the wire bonds, and the leads with a mold compound. Cavities may be etched into the top surface of each die attach pad on the leadframe, and a pre-deposited layer of die attach material is disposed within each of the cavities. The method may include activating the die attach material with heat or UV energy prior to adhering the semiconductor device. The method may include removing a protective material from the leadframe prior to adhering the semiconductor device. [Brief description of the drawings]

[0006] Having now described the invention in general terms, reference is now made to the accompanying drawings, in which:

[0007] [Figure 1] FIG. 2 is a top view of a portion of a conductive leadframe strip.

[0008] [Diagram 2] 2 illustrates a detailed view of a portion of the conductive leadframe strip from FIG. 1, such as for a QFN (Quad Flat No-lead) package;

[0009] [Diagram 3] FIG. 3 is a side view of an integrated circuit package singulated from a leadframe sheet such as the portion shown in FIG. 2.

[0010] [Figure 4A]1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 4B] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 4C] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film.

[0011] [Figure 5A] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 5B] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 5C] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 5D] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film. [Figure 5E] 1 illustrates a process for the manufacture of leadframe strips having a pre-applied die attach film.

[0012] [Figure 6] 1 illustrates an alternative example of a preformed leadframe sheet.

[0013] [Figure 7] 1 is a flow chart illustrating steps of an exemplary process for manufacturing a semiconductor package. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present disclosure will be described with reference to the accompanying drawings. The drawings are not drawn to scale and are provided merely to illustrate the present disclosure. Several aspects of the present disclosure are described hereinafter with reference to example applications for explanation. It should be understood that many specific details, relationships, and methods are shown for the purpose of understanding the present disclosure. The present disclosure is not limited by the described order of acts or events, as some acts may occur in different orders and / or simultaneously with other acts or events. Also, not all described acts or events are required to implement a methodology in accordance with the present disclosure.

[0015] Corresponding numbers and symbols in different drawings generally refer to corresponding parts unless otherwise indicated. The drawings are not necessarily drawn to scale. In the drawings, like reference numbers indicate like elements throughout, and the various features are not necessarily drawn to scale. In the following discussion and claims, the terms "including," "includes," "having," "has," "with," or variations thereof are intended to be inclusive, similar to the term "comprising," and therefore should be interpreted to mean "including, but not limited to." Additionally, the terms "coupled" and / or "couple" are intended to include indirect or direct electrical or mechanical connections, or combinations thereof. For example, when a first device is coupled to or electrically coupled with a second device, the connection may be through a direct electrical connection or through an indirect electrical connection via one or more intervening devices and / or connections. The terms "top," "bottom," "front," "back," "on," "above," "below," and "lower" may be used in this disclosure. These terms should not be construed as limiting the location or orientation of structures or elements, but should be used to provide a spatial relationship between structures or elements.

[0016] The term "semiconductor device" is used herein. A semiconductor device may be a discrete semiconductor device such as a bipolar transistor, several discrete devices such as a pair of power FET switches fabricated together on a single semiconductor die, or the semiconductor die may be an integrated circuit comprising multiple semiconductor devices such as multiple capacitors in an A / D converter. A semiconductor device may include passive devices such as resistors, inductors, filters, sensors, or active devices such as transistors. A semiconductor device may be an integrated circuit comprising hundreds or thousands of transistors coupled to form a functional circuit such as a microprocessor or memory device. A semiconductor device may also be referred to herein as a "semiconductor die."

[0017] The term "integrated circuit package" is used herein. An integrated circuit package has at least one semiconductor device electrically coupled to terminals and a package body that protects and covers the semiconductor device. In some arrangements, multiple semiconductor devices may be packaged together. For example, a power field effect transistor (FET) semiconductor device and a second semiconductor device (such as a gate driver die or controller die) may be packaged together to form a single packaged electronic device. Additional components, such as passive components, may be included in the packaged electronic device. The semiconductor device is mounted with a package substrate that provides conductive leads. Some of the conductive leads form the terminals for the packaged device. In a wire-bonded integrated circuit package, bond wires connect the conductive leads of the package substrate to bond pads on the semiconductor device. The integrated circuit package may have a package body formed by a thermosetting epoxy resin molding compound in a molding process or by the use of an epoxy, plastic, or resin that is liquid at room temperature and subsequently hardened. The package body may provide a hermetic package for the packaged device. The package body may be formed in a mold using an encapsulation process, but some of the leads of the package substrate are not covered during encapsulation. These exposed lead portions form terminals for the integrated circuit package, which may also be referred to herein as a "semiconductor package" or a "sensor package."

[0018] A package substrate is a substrate arranged to receive and support a semiconductor die in a completed semiconductor device package. Package substrates useful in this configuration include conductive lead frames, which may be formed from copper, aluminum, stainless steel, steel, and alloys such as alloy 42 and copper alloys. The lead frame may include a die pad with a die side surface for mounting the semiconductor die, and conductive leads disposed near and spaced from the die pad for coupling to bond pads on the semiconductor die using wire bonds, ribbon bonds, or other conductors. In an exemplary configuration, a heat slug is attached to the package substrate, the heat slug having a die mounting area for mounting the semiconductor device. The lead frame may be provided in a strip or array. The conductive lead frame may be provided as a panel with a strip or array of rows and columns of unit device portions. The semiconductor devices may be placed on each unit device portion in the strip or array. The semiconductor devices may be placed on the die mounting area for each packaged semiconductor device. The semiconductor devices may be mounted using a die attach or die adhesive. In a wire bond package, bond wires may couple bond pads on the semiconductor device to leads of a lead frame. The lead frame may have portions plated in areas designated for wire bonding, such as, for example, silver, nickel, gold, or palladium plating. After the bond wires are in place, a portion of the package substrate, the semiconductor device, and at least a portion of the die pad may be covered with a protective material, such as a mold compound. The package substrate may carry multiple semiconductor devices per unit.

[0019] As used herein, the term "die attach pad" is used. A die attach pad is a portion of a metal leadframe adapted to mount a semiconductor device or die. The semiconductor device may be mounted on the die attach pad by a layer of die attach material that electrically and physically connects the semiconductor device to the leadframe.

[0020] The term "bond pad" is used herein. A bond pad is an area on a semiconductor device that allows the semiconductor device to be electrically coupled to an external circuit, such as by wire bonding to a lead frame or printed circuit board. Bond pads may be formed from a variety of materials, such as aluminum, gold, or copper, and may have a variety of configurations.

[0021] FIG. 1 is a top view of a portion of a conductive leadframe strip 101, which may be formed from copper, aluminum, stainless steel, steel, and alloys such as alloy 42 and copper alloys. The leadframe strip 101 has a die attach pad (DAP) portion 102 that is held in place and spaced apart by various tie bar portions 103. The DAP portion has a die side surface for mounting a semiconductor die. The tie bar portions 103 may include conductive leads 104 disposed near and spaced apart from the DAP portion 102. The conductive leads 104 are for bonding to bond pads on a semiconductor die using wire bonds, ribbon bonds, or other conductors. The conductive leads may be plated for improved wire bonding, for example, silver, nickel, gold, or palladium plating may be used. The leadframe strip 101 may be provided, for example, by a leadframe supplier used in the manufacture of semiconductor devices. The leadframe may be provided in a strip or an array.

[0022] FIG. 2 illustrates a detailed view of a portion 201 of the conductive leadframe strip 101 from FIG. 1, such as for a QFN (Quad Flat No-lead) package. A semiconductor die 202 is mounted on the DAP portion 102. The semiconductor die 202 has an active surface 203 with several bond pads 204. The bond pads 204 are coupled to the conductive leads 104, for example, using bond wires 205. The conductive leadframe 101 may be provided as a panel with a strip or array of DAP portions 102 in rows and columns. A semiconductor device 202 may be placed on each DAP portion 102 in the strip or array. After the bond wires are in place, a portion of the package substrate, the semiconductor devices, and at least a portion of the die attach pads may be covered with a protective material, such as a mold compound, and the leadframe strip 101 may be singulated into individual integrated circuit packages.

[0023] 3 is a side view of an integrated circuit package 301 singulated from a leadframe sheet such as portion 201 of FIG. 2. In the illustrated example, the semiconductor die 202 is large and generally fills the area of ​​the DAP portion 102. A die attach adhesive 302 or die attach film (DAF) can be used to mount the semiconductor device 202 onto the DAP portion 102. Fillet and bleed require a minimum keep-out zone around the semiconductor die 202. Devices with semiconductor die areas close to the die attach pad area are prone to epoxy contamination on the backside 302 of the DAP portion due to excess epoxy material applied during the die attach process. The excess epoxy and bleed out can flow over the edges of the DAP portion 102 and onto the backside 302 of the leadframe 101.

[0024] In one example, a die attach film may be pre-applied to the die attach pad area during leadframe fabrication to avoid the die attach overflowing the die attach pad. Figures 4A-4C illustrate a process for the fabrication of leadframe strips with a pre-applied die attach film. Figure 4A illustrates a base leadframe material 401, such as a copper plate, having a top surface 402 and a bottom surface 403. Figure 4B illustrates the leadframe material 401 after an etching process. For example, a photoresist material, such as a dry film resist (DFR), is laminated onto the top surface 402 and the bottom surface 403 of the leadframe material 401. The photoresist material is irradiated, such as with a visible light laser, in the form of a desired leadframe pattern image. The photoresist material is then exposed to a developer that selectively dissolves any unirradiated portions of the negative tone photoresist material or the irradiated portions of the positive tone photoresist material, thereby exposing some areas 404 of the leadframe material 401. The masked leadframe material 401 is then subjected to a wet or dry etching process. Areas 404 of the leadframe material 401 that are not covered by the mask are etched away. Areas of the leadframe material 401 that are covered by portions of the mask are not etched and remain after the etching process. These unetched portions form conductive lead regions 405 and die attach portion regions 406.

[0025] FIG. 4C illustrates a die attach film 407, such as a fully cured epoxy, attached to the die attach pad 406 after the etching process. The die attach film 407 may be applied using, for example, a tape lamination process. The die attach film 407 may be a pre-cut tape with a design based on the dimensions of the die attach pad 406. The pre-cut tape 407 is applied to the leadframe material 401 to form a leadframe sheet 400 ready for the die attach process. The leadframe sheet 400 may be used in semiconductor device assembly without requiring a separate step of applying die attach in the assembly process. Instead, the assembly process may start with a die mounting step and proceed to wire bonding and molding. This may increase the leadframe cost due to the additional step of adding the die attach film, but the die bond process is simplified by eliminating the epoxy dispensing step. The amount of die attach film 407 applied in FIG. 4C can be controlled during leadframe fabrication so that the die attach film does not overflow die attach pad 406 when a semiconductor device is mounted on die attach pad 406 using die attach film 407.

[0026] In one example, die attach pad 406 has a width W1 of 3 mm and leadframe material 401 has a thickness H1 of 0.2 mm. Connection leads 405 and die attach pad 406 have half-etched edges 408 with a thickness H2 of 0.1 mm. Die attach film 407 may have a thickness H3 of 0.02 mm.

[0027] In another example, die attach pad adhesive may be pre-applied to the die attach pad area during leadframe fabrication to prevent the die attach from overflowing the die attach pad. Figures 5A-5E illustrate a process for the fabrication of leadframe strips with pre-applied die attach adhesive. Figure 5A illustrates a base leadframe material 501, such as a copper sheet, having a top surface 502 and a bottom surface 503. Figure 5B illustrates the leadframe material 501 after an etching process, such as that described in connection with Figure 4B. The unetched portions form conductive lead regions 504 and die attach portion regions 505.

[0028] FIG. 5C illustrates the result of a second etching step in which a cavity 506 is etched into the top surface 502a of the die attach pad 505. The cavity 506 is then filled with a die attach adhesive 507, such as an epoxy applied by screen printing or spraying. FIG. 5D illustrates the cavity 506 filled with die attach adhesive 507, which may be any suitable adhesive used to attach a semiconductor chip to the die attach pad 505. The die attach adhesive may be electrically insulating and / or thermally conductive. The depth of the cavity 506 and the amount of die attach adhesive 507 may be selected such that the top surface 507a of the die attach adhesive 507 is flush with the top surface 502a of the die attach pad. The cavity 506 has a surface area defined by a length and a width across the top surface 507a. The surface area of ​​the cavity may be selected to be equal to the bottom surface of the semiconductor die. The surface area of ​​the cavity may be larger than the surface area of ​​the bottom of the semiconductor die such that a portion of the die attach material 507 surrounds the semiconductor die when mounted on the leadframe sheet 500. The leadframe sheet 500 may be provided to a semiconductor device manufacturer for package assembly without the need for a separate step of applying die attach.

[0029] The amount of die attach adhesive 507 applied in FIG. 5D can be controlled during leadframe fabrication such that when a semiconductor device is attached onto die attach pad 505 with die attach adhesive 507, die attach adhesive 507 does not overflow die attach pad 505.

[0030] In one example, by controlling the depth of cavity 506 and the amount of die attach 507 deposited, a lower overall package thickness can be achieved when a semiconductor die is mounted on die attach pad 505 with die attach 507. The bottom surface of a semiconductor die attached to die attach pad 505 above cavity 506 is flush with the top surface of die attach pad 505. Cavity 506 and pre-applied die attach material 507 eliminate the need for a die attach layer located on top of the die attach pad, such as layer 302 in FIG.

[0031] FIG. 5E illustrates an alternative example of a leadframe sheet 510 in which die attach 508 is used to fill cavity 506, with a portion of die attach 508a overlapping top surface 502a of the die attach pad. In one example, a stencil or mask may be used when the die attach is sprayed or screen printed onto the die attach pad. The stencil or mask allows die attach 508 to fill cavity 506 and partially overlap the edge of cavity 506. In this example, die attach 508 is not flush with top surface 502a of the die attach pad. The overlapping die attach 508 forms a ring or rim around cavity 506 on top surface 502a. The amount of overlap 508a is controlled to prevent excess die attach 508 from spilling over the die attach pad when the semiconductor die is mounted.

[0032] 5D and 5E provide an opportunity to reduce the height of a semiconductor package because the top 507a of the die attach adhesive 507 is generally flush with the top 502a of the die attach pad. Thus, a semiconductor die can be mounted with its bottom surface generally flush with the top 502a of the die attach pad.

[0033] 6 illustrates a further alternative example of a pre-formed leadframe sheet 600. Leadframe sheet 600 has leadframe material 601, such as copper or a copper alloy, that is etched to create conductive leads 602 and die attach pad 603. Die attach pad 603 is further etched to create a cavity 604 that is filled with die attach adhesive 605. The open areas of leadframe sheet 600 are then filled with molding compound 606, such as epoxy or plastic. In the exemplary leadframe sheet 600, molding compound 606 is applied such that the top and bottom surfaces of molding compound 606 are flush with the top and bottom surfaces of conductive leads 602, die attach pad 603, and die attach adhesive 605.

[0034] Pre-formed leadframe sheet 600 is similar to leadframe sheet 500 (FIG. 5D). In other examples, molding compound may also be applied to other leadframe sheets, such as leadframe sheet 400 (FIG. 4C) and leadframe sheet 510 (FIG. 5E).

[0035] The leadframe sheet with the pre-applied die attach film or die attach adhesive can be provided by the leadframe manufacturer to the semiconductor device manufacturer for package assembly without the need for a separate step of applying the die attach. During shipping or transport of the leadframe sheet with the pre-applied die attach material, a sheet or film, such as a plastic material, can be applied to the surface of the leadframe sheet to protect the die attach material. The protective sheet or film is removed by the semiconductor device manufacturer, after which the semiconductor device is attached to the leadframe sheet.

[0036] In some instances, a die attach film or adhesive that has been pre-applied to the leadframe sheet is activatable. The die attach material may not be tacky when applied to the leadframe sheet, but when activated by heating or exposure to UV radiation, the die attach material becomes tacky and a semiconductor device can be mounted onto the leadframe sheet. This allows semiconductor device manufacturers to stage the leadframe sheet and then activate the die attach material when the process is ready to mount the semiconductor die.

[0037] 7 is a flow chart illustrating steps of an example process for manufacturing a semiconductor package. In step 701, a lead frame having a plurality of die attach pads is provided. Each die attach pad has a top surface with a pre-deposited layer of die attach material. In some examples, the die attach material is a die attach adhesive disposed in a cavity etched into the top surface. The top surface of the die attach adhesive is flush with the top surface of the die attach pad. In other examples, the die attach material is a die attach tape on the top surface. The die attach tape is cut to dimensions selected based on the dimensions of the semiconductor device to be mounted on the die attach pad.

[0038] At step 702, some leadframe examples require that protective material be removed from the leadframe prior to attaching the semiconductor device.

[0039] At step 703, some examples of die attach materials require activating the die attach material with heat or UV energy to adhere the semiconductor device to the die attach pad.

[0040] At step 704, a semiconductor device is attached to each die attach pad with a die attach material. When a die attach adhesive is used, the bottom surface of the semiconductor device may be flush with the top surface of the die attach adhesive and the top surface of the die attach pad. In another example, when the die attach material is a die attach adhesive, the top surface of the die attach pad may include an additional portion of die attach material that forms a ring or rim that surrounds the cavity and the sides of the semiconductor device.

[0041] In step 705, wire bonds are attached from the contacts on each semiconductor device to the leads on the leadframe.

[0042] At least a portion of the semiconductor device, the die attach pad, the die attach material, the wire bonds, and the leads are covered with a mold compound in step 706. In some examples, the lead frame provided in step 701 may be pre-molded with the mold compound pre-placed in spaces between the conductive lead portions and the die attach pad portions of the lead frame.

[0043] An exemplary method of assembling a semiconductor package includes providing a leadframe having a plurality of die attach pads, each die attach pad having a top surface with a pre-applied layer of die attach material. A semiconductor device is attached to each die attach pad with the pre-applied die attach material. Wire bonds extending from contacts on each semiconductor device are attached to leads on the leadframe. At least a portion of the semiconductor device, the die attach pads, the die attach material, the wire bonds, and the leads are covered with a mold compound.

[0044] In some examples, a cavity is etched into the top surface of each die attach pad on the leadframe. A pre-deposited layer of die attach material is placed into each of the cavities. The top surface of the die attach material is coplanar with the top surface of the die attach pad. The top surface of the die attach pad may include a portion of the die attach material that surrounds the cavity.

[0045] The pre-applied layer of die attach material may be a die attach tape cut to dimensions selected based on the dimensions of the semiconductor device.

[0046] The die attach material may be activated using heat or UV energy prior to attaching the semiconductor device. A protective material may be attached to the lead frame, which is removed prior to attaching the semiconductor device.

[0047] An exemplary method for manufacturing a leadframe includes providing a leadframe material having a top surface and a bottom surface, etching the leadframe material to create a leadframe strip having a plurality of die attach pad areas and a plurality of conductive leads adjacent each die attach pad area, etching the top surface of each die attach pad area to create a cavity, and depositing die attach material in the cavity of each die attach pad area, the top surface of the die attach material being coplanar with the top surface of the leadframe material. The amount of die attach material deposited in the cavity of each die attach pad is selected to prevent the die attach material from overflowing the die attach pad when a semiconductor die is mounted on the die attach pad with the die attach material. The amount of die attach material applied to the die attach pad is selected to minimize the height or thickness of the final semiconductor package.

[0048] The die attach material on the lead frame may be a die attach film cut to fit within the cavity.

[0049] In some examples, depositing the die attach material in the cavity includes spraying the die attach material into the cavity.

[0050] In some examples, depositing the die attach material in the cavity includes screen printing the die attach material into the cavity. The die attach material can be an ink residue that is printed into the cavity.

[0051] The die attach material on the lead frame may require activation using heat or UV energy before bonding the semiconductor device to the die attach pad area.

[0052] A process for manufacturing a leadframe can include applying a protective material to a leadframe sheet, the protective material being configured for removal prior to bonding the semiconductor device to the die attach pad.

[0053] A process for manufacturing the leadframe may include depositing excess die attach material on a top surface of each die attach pad, the excess die attach material forming a rim surrounding a cavity on each die attach pad.

[0054] An exemplary leadframe sheet includes a plurality of leadframe segments configured for singulation into separate units, each leadframe segment having a die attach pad and a plurality of conductors. A cavity is formed in a top surface of each die attach pad. A die attach material is disposed within the cavity. The die attach material is adapted for mounting a semiconductor die onto the die attach pad. The top surface of the die attach material is coplanar with the top surface of each die attach pad. A film is applied to the top surface of the leadframe sheet. The protective film is configured to protect the die attach material disposed within the cavity during transport of the leadframe sheet.

[0055] The leadframe may include a border of additional die attach material on the top surface of the die attach pad and surrounding all sides of the cavity.

[0056] The leadframe sheet may include an amount of die attach material deposited in the cavity of each die attach pad selected to prevent the die attach material from overflowing the die attach pad when a semiconductor die is mounted on the die attach pad with the die attach material.

[0057] The leadframe sheet may further include a molding material applied between the plurality of die attach pads and the plurality of conductors, the molding material having top and bottom surfaces coplanar with the top and bottom surfaces of the leadframe sheet.

[0058] Although various examples of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Many modifications to the disclosed examples can be made in accordance with the disclosure herein without departing from the spirit or scope of the present disclosure. Modifications can be made to the described embodiments, and other embodiments are possible, all within the scope of the present disclosure. Thus, the breadth and scope of the present invention should not be limited by any of the above examples. Rather, the scope of the present disclosure is defined according to the following claims and their equivalents.

Claims

1. 1. A method of assembling a semiconductor package, comprising: providing a leadframe having a plurality of die attach pads, each die attach pad having a top surface with a layer of pre-applied die attach material; adhering a semiconductor device to each die attach pad with said layer of pre-applied die attach material; attaching wire bonds from contacts on each semiconductor device to leads on the leadframe; covering at least a portion of the semiconductor device, the die attach pad, the die attach material, the wire bonds, and the leads with a molding compound; A method comprising:

2. 2. The method of claim 1, wherein a cavity is etched into the top surface of each of the die attach pads on the leadframe, and a layer of the pre-deposited die attach material is disposed within each of the cavities.

3. 3. The method of claim 2, wherein a top surface of the die attach material is coplanar with the top surface of the die attach pad.

4. 3. The method of claim 2, wherein the top surface of the die attach pad comprises a portion of the die attach material that surrounds the cavity.

5. 10. The method of claim 1, wherein the layer of pre-applied die attach material is a die attach tape cut to dimensions selected based on dimensions of the semiconductor device.

6. 10. The method of claim 1, further comprising activating a die attach material with heat or UV energy prior to bonding the semiconductor device.

7. 10. The method of claim 1, further comprising removing a protective material from the leadframe prior to bonding a semiconductor device.

8. 1. A method for the manufacture of a lead frame, comprising: providing a leadframe material having a top surface and a bottom surface; Etching the leadframe material to produce a leadframe strip having a plurality of die attach pad areas and a plurality of conductive leads adjacent each die attach pad area; etching the top surface of each die attach pad area to create a cavity; depositing a die attach material in the cavity in each die attach pad area; Including, The method, wherein the top surface of the die attach material is coplanar with the top surface of the leadframe material.

9. 9. The method of claim 8, wherein the die attach material is a die attach film that is cut to fit within the cavity.

10. 9. The method of claim 8, wherein depositing the die attach material in the cavity comprises spraying the die attach material into the cavity.

11. 9. The method of claim 8, wherein depositing the die attach material in the cavity comprises screen printing the die attach material into the cavity.

12. 9. The method of claim 8, wherein the die attach material is an ink residue printed into the cavity.

13. 10. The method of claim 8, wherein the die attach material requires activation with heat or UV energy prior to bonding a semiconductor device to the die attach pad area.

14. 10. The method of claim 8, further comprising applying a protective material to a leadframe sheet, the protective material configured for removal prior to bonding a semiconductor device to the die attach pad.

15. 9. The method of claim 8, wherein depositing the die attach material further comprises depositing excess die attach material on the top surface of each die attach pad, the excess die attach material forming a rim surrounding the cavity on each die attach pad.

16. 10. The method of claim 8, wherein an amount of die attach material deposited in the cavity of each die attach pad is selected to prevent the die attach material from overflowing the die attach pad when a semiconductor die is attached onto the die attach pad with the die attach material.

17. A lead frame sheet, a plurality of leadframe segments configured for singulation into separate units, each leadframe segment having a die attach pad and a plurality of conductors; a cavity formed in a top surface of each die attach pad; a die attach material disposed within the cavity, the die attach material adapted for mounting a semiconductor die on the die attach pads, a top surface of the die attach material being flush with the top surface of each die attach pad; a protective film applied to a top surface of the leadframe sheet, the protective film configured to protect the die attach material disposed within the cavities during transportation of the leadframe sheet; a lead frame sheet comprising:

18. The lead frame sheet according to claim 17, the leadframe sheet further including a border of additional die attach material on the top surface of the die attach pad and surrounding all sides of the cavity.

19. The lead frame sheet according to claim 17, an amount of die attach material deposited in the cavity of each die attach pad is selected to prevent the die attach material from overflowing the die attach pad when a semiconductor die is mounted on the die attach pad using the die attach material; Lead frame sheet.

20. The lead frame sheet according to claim 17, a molding material applied between the plurality of die attach pads and the plurality of conductors, the molding material having top and bottom surfaces that are coplanar with the top and bottom surfaces of the leadframe sheet. Lead frame sheet.

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