Integrated circuit with improved ball bond adhesion
By forming recesses on the surface of the bonding liner and adopting improved capillary tip configuration and low-temperature wire bonding process, the crack problem caused by stress between the ball joint and the die in the integrated circuit is solved, achieving higher adhesion and structural integrity.
Patent Information
- Application Number
- CN202411490866.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-08-30
- Filing Date
- 2024-10-24
- Publication Date
- 2025-02-28
AI Technical Summary
In the wire bonding process of integrated circuits, stress between the ball bonding member and the die leads to cracks and gaps around, impairing structural integrity and operation.
By forming recesses or cavity on the surface of the bonding liner, the adhesion area between the ball joint and the bonding liner is increased, and an improved capillary tip configuration and cryogenic wire bonding process is adopted to ensure that the ball joint is evenly adhered to the bonding liner.
It effectively reduces the gap between the ball joint and the joint pad, improves adhesion and reduces the occurrence of cracks, thereby improving the structural integrity and operational reliability of the integrated circuit.
Smart Images
Figure CN119542304A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an electronic device, and more particularly to an integrated circuit package that includes increased ball bonding surface area to improve adhesion. Background Art
[0002] Leaded and leadless integrated circuits include wire bonds that provide connections between the die and the leads of the lead frame. The wire bonds are bonded or fixed to the active surface of the die via ball bonds. However, during the attachment and curing process of the wire bonds, stress occurs at the bond wires, that is, at the interface between the ball bonds and the bonding surface (e.g., bonding pads) on the surface of the die. The stress causes cracks to appear around the perimeter of the ball bonds. As a result, gaps are formed around the perimeter of the ball bonds at the bond wires, thereby compromising the structural integrity and operation of the integrated circuit. Summary of the invention
[0003] In the described examples, an electronic device includes a substrate and a die, the die having an active surface, the die being disposed on the substrate. A bonding pad is disposed on the active surface of the die. The bonding pad includes a recess defined in a top surface of the bonding pad. A ball bond is disposed in the recess of the bonding pad, and a wire bond is attached to the ball bond and the substrate. A molding compound encapsulates the die, the bonding pad, the ball bond, and the wire bond. In addition, the molding compound covers all surfaces of the substrate except one surface, wherein the uncovered one surface faces away from the die.
[0004] In another described example, a method includes: providing a die having an active surface; and forming a bonding pad on the active surface of the die. Forming a recess in a top surface of the bonding pad. Placing the die on a substrate, and attaching a wire bond from the bonding pad to the substrate. Forming a molding compound over the die.
[0005] In yet another described example, a method includes manufacturing a die assembly, which includes providing a die having an active surface, and forming a photoresist material layer over the active surface of the die, wherein the photoresist material layer includes an opening patterned therein. A metal plating layer is deposited in the opening of the photoresist material layer to form a bonding pad on the active surface of the die. A recess is formed in a top surface of the bonding pad. The die is placed on a die pad of a lead frame, and a wire bond is attached from the bonding pad to the lead frame. A molding compound is formed over the die. BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Figure 1A is a cross-sectional view of an example electronic device.
[0007] Figure 1B Is from Figure 1A A close-up view of the bonding pads of an example electronic device.
[0008] Figure 2 It is shown for Figure 1A A block diagram flow chart of a manufacturing process of an electronic device.
[0009] Figure 3A is a top view of a wafer containing die.
[0010] Figure 3B Shown in the early stages of manufacturing of the die assembly from Figure 3A Cross-sectional view of a die singulated from a wafer.
[0011] Figure 3C Show Figure 3B A cross-sectional view of a die assembly after undergoing patterning of a photoresist material layer.
[0012] Figure 3D Shows the electroplating process Figure 3C Cross-sectional view of a die assembly.
[0013] Figure 3E After removing the photoresist material layer Figure 3D Cross-sectional view of a die assembly.
[0014] Figure 3F After the etching process Figure 3E Cross-sectional view of a die assembly.
[0015] Figure 3G A cross-sectional view of a leadframe-based substrate is shown at an early assembly stage of an electronic device.
[0016] Figure 3H Shown after deposition of die attach material Figure 3G Cross-sectional view of a leadframe-based substrate.
[0017] Fig. 3I A cross-sectional view of an electronic device is shown, wherein Figure 3F The die assembly is attached to the lead frame.
[0018] Figure 3J After undergoing the wire bonding process Fig. 3I A cross-sectional view of an electronic device.
[0019] Figure 3K After the molding compound is formed, Figure 3J A cross-sectional view of an electronic device.
[0020] Figures 4A-4E Shown is a process of attaching wire bonds to the die and terminal leads using a capillary instrument.
[0021] Figures 5A-5C is an illustration of an example single internal chamfer capillary tip configuration.
[0022] Figures 6A-6C is an illustration of an example double internal chamfer capillary tip configuration.
[0023] Figures 7A-7C is an illustration of an example convex internal chamfer capillary tip configuration. DETAILED DESCRIPTION
[0024] Wire bonds in an integrated circuit (IC) provide a connection between a die and the leads of a lead frame. The wire bonds are bonded or fixed to the active surface of the die via ball bonds. However, during the wire bonding and curing process, stress occurs at the bonding wire, i.e., at the interface between the ball bonds and the bonding surface (e.g., bonding pad) on the surface of the die. The stress causes cracks to appear around the perimeter of the ball bonds. Therefore, gaps are formed around the perimeter of the ball bonds at the bonding wires, thereby compromising the structural integrity and operation of the integrated circuit.
[0025] Disclosed herein is an electronic device (e.g., an integrated circuit package) comprising an increased ball bonding surface area, and a method of bonding a ball bonding piece to a bonding pad to improve adhesion between the ball bonding piece and the die, thereby reducing cracks and thus overcoming the aforementioned shortcomings. The electronic device comprises a die attached to a lead frame and a bonding pad disposed on the active surface of the die. The surface of the bonding pad is modified to increase the adhesion area between the ball bonding piece and the bonding pad. Specifically, a recess or cavity is formed in the surface of the bonding pad. The formation of the recess increases the bonding pad surface area, to which the ball bonding piece can adhere after an inline bonding process. Specifically, during the inline bonding process, the ball bonding piece is deposited in the recess and subjected to heat and pressure. Therefore, the ball bonding piece adheres to the bottom surface and sidewalls of the recess.
[0026] The method includes: attaching a wire bond wire to a bonding pad using an improved capillary tip configuration; and performing a low temperature wire bonding process to adhere a ball bond to the bonding pad. The improved capillary tip configuration includes either a double internal chamfer or a convex internal chamfer. The improved capillary tip more evenly distributes a force vector generated by deposition of the ball bond across the ball bond. The even distribution of the force vector forces the ball bond to enter the recess more evenly, thereby mitigating the formation of a gap between the ball bond and the bonding pad.
[0027] The method further includes providing a low wire bonding temperature during the wire bonding process. Current methods use high wire bonding temperatures (e.g., approximately 180° C.), which contributes to the cracks and gaps at the bonding wires mentioned above. The method disclosed herein uses a low wire bonding temperature (e.g., less than 120° C.). Since the ball bond can be copper plated, the low wire bonding temperature mitigates oxidation.
[0028] Figure 1A 1 is a cross-sectional view of an example electronic device (e.g., integrated circuit) 100, which includes a substrate 102, a die 104 disposed on the substrate 102, wire bonds 106, and a molding compound 108. The electronic device 100 may include a leaded or leadless integrated circuit (IC), including but not limited to a quad flat no-lead (QFN) package, a quad flat package (QFP), a dual in-line package (DIP), a single in-line package (SIP), etc. Although Figure 1A The example electronic device 100 in FIG. 1 is an example illustration of a QFN package, but Figure 1A The illustrated electronic device 100 is for illustrative purposes only and is not intended to limit the scope of the present invention.
[0029] The substrate 102 includes a lead frame including a die pad 110 and conductive terminals 112 (e.g., leads, contacts). In alternative examples, the substrate may include a laminate substrate or a printed circuit board-based substrate. For illustrative purposes only, a lead frame-based substrate will be described herein and shown in the drawings. The die pad 110 may include a thermal pad exposed on an attachment side 114 of the electronic device 100. The thermal pad creates an effective thermal path from the electronic device 100 to the board (e.g., printed circuit board). In addition, the exposed thermal pad or die pad 110 also enables a ground connection to the board. The die 104 is attached to the die pad 110 via a die attach material 116.
[0030] Still viewing Figure 1A Also see Figure 1B , bonding pads 118 are disposed on an active surface 120 of the die 104 . Figure 1B1 is a close-up view of one of the bonding pads 118 attached to the active surface 120 of the die 104. The bonding pad 118, which is made of copper or aluminum, provides a connection to the die 104 for the wire bond 106. A recess or cavity 122 is formed in the bonding pad 118, thereby forming a sidewall 124 in the bonding pad 118. The recess 122 is configured to receive a ball bond (e.g., melted / molten wire bond material) 126. The recess 122 increases the surface area of the bonding pad 118 to increase the bonding adhesion between the bonding pad 118 and the ball bond 126. More specifically, the ball bond 126 not only adheres to the top surface of the bonding pad 118 and the bottom surface of the recess 122, but the ball bond 126 also adheres to the inner surface 128 of the sidewall 124. Therefore, the inner surface 128 of the sidewall provides additional bonding pad surface area for the adhesion of the ball bond 126. The additional surface area provided by the recess 122 mitigates the occurrence of gaps at the line of joint 130 (ie, at the interface between the ball joint 126 and the joint pad 118 ).
[0031] Wire bonds 106 are connected to ball bonds 126 and provide connections between active surface 120 of die 104 and conductive terminals 112. In the example shown, molding compound 108 covers all but one surface of substrate 102, with the uncovered one surface facing away from die 104 and electronic device 100. In addition, molding compound 108 encapsulates die 104, wire bonds 106, bonding pads 118, and ball bonds 126.
[0032] Figure 2 is a block diagram flow chart illustrating a manufacturing process 200, and Figures 3A-3K Show and form Figure 1A Specifically, Figures 3A-3D Shown with Figure 1A The manufacturing process associated with the formation of the die assembly of the electronic device 100 shown, and Figure 3G-3K The manufacturing process associated with placing the die assembly on the substrate and the manufacturing process thereby Figure 1A The molding process of the electronic device 100 shown. Although depicted sequentially for convenience, at least some of the actions shown may be performed in a different order and / or in parallel. Alternatively, some embodiments may only perform some of the actions shown. Furthermore, although Figure 2-3K The example shown is a diagram showing Figure 1A The exemplary method of the exemplary configuration is shown, but other methods and configurations are also possible. It should be understood that although Figure 2-3KThe method shown in exemplifies the manufacturing process of a single electronic device, but the process is applicable to an array of electronic devices. Therefore, after the array of electronic devices is manufactured, the array is singulated to separate each electronic device 100 from the array.
[0033] See also Figure 2 and Figures 3A-3F , Figure 1A The manufacturing process of the die assembly of the electronic device 100 shown begins at 202 with a wafer 300, such as Figure 3A Specifically, Figure 3A 300 according to various examples. For example, the wafer 300 may be a silicon wafer. The wafer 300 includes a plurality of dies 302. The manufacturing techniques described below may be performed on individual dies 302 (after singulation), or the techniques may be performed more efficiently at a certain quality scale, such as simultaneously performing on a plurality of dies 302 (before singulation) of the wafer 300. For convenience and clarity, the remaining figures show one die 302, and it should be understood that the processes described herein as being performed on a die 302 may also be performed on the remaining dies 302 of the wafer 300 (e.g., sequentially, simultaneously).
[0034] Figure 3B A cross-sectional view of a single die 302 of wafer 300 is shown. Figure 3C At 204, a photoresist material layer 304 overlies the die 302 and is patterned and developed to expose openings 306 in the photoresist material layer 304 according to a pattern. The photoresist material layer 304 may have a thickness that varies corresponding to the wavelength of radiation used to pattern the photoresist material layer 304. The photoresist material layer 304 may be formed over the die 302 via a spin coating or spin casting deposition technique, selectively irradiated (e.g., via deep ultraviolet (DUV) irradiation) and developed to form the openings 306.
[0035] At 206, Figure 3C The configuration in FIG. 302 undergoes an electroplating process 370 to deposit a metal plating layer (eg, copper, aluminum) in the opening 306 to form a bonding pad 308 on the active surface 310 of the die 302, thereby producing Figure 3D Once the plating process 370 is completed, the photoresist material layer 304 is removed via a solvent stripping process 380, thereby producing Figure 3E At 208, Figure 3E The configuration in FIG. 3 is subjected to an etching process 390 to form a recess or cavity 312 in each bonding pad 308, thereby producing Figure 3F Alternatively, Figure 3E The configuration in may undergo an additional (second) plating process to structure the sidewalls of the bonding pad 308 to form the recess 312 . Figure 3F The configuration in shows a single die assembly 314 including a die 302 and a bonding pad 308 having a recess 312 .
[0036] Figure 3G-3K The manufacturing process associated with the process of placing the die assembly 314 on the substrate and the molding process of manufacturing the electronic device 100 shown in Figure 1 are shown. In the following description, the substrate includes a lead frame. It should be understood that in alternative examples, the substrate may include a laminate substrate or a printed circuit board-based substrate. For illustrative purposes only, a lead frame-based substrate will be described herein and shown in the drawings.
[0037] Still viewing Figure 2 At 210, a lead frame 320 is provided, such as Figure 3G The lead frame 320 includes a die pad 322 and conductive terminals 324 (eg, leads, contacts). At 212, a die attach material 326 is deposited on the surface of the die pad 322, thereby producing Figure 3H For simplicity, reference is made to a dispense die attach technique, however, other die attach techniques may be utilized, such as using a die attach film pre-applied to the back side of the wafer. At 214, the die assembly 314 is then picked up and placed on the die attach material 326, thereby creating Fig. 3I Configuration in .
[0038] At 216, using a capillary instrument described below, a first end 328 of a wire bond 330 is attached via a ball bond (e.g., melted / molten wire bond material) 334 to a recess 312 of a bond pad 308 disposed on an active surface 310 of the die 302, and a second end 332 of the wire bond 330 is attached to a surface of each of the conductive terminals 324 (e.g., melted / molten wire bond material), thereby producing Figure 3JConfiguration in. The wire bonding process is a welding-type operation that uses heat and pressure to attach the wire bonding member 330. More specifically, during the wire bonding process, the wire bonding member 330 and the ball bonding member 334 are heated to a predetermined wire bonding temperature. The predetermined wire bonding temperature is a low temperature (e.g., approximately 90°C-120°C), and the low temperature alleviates the oxidation of the ball bonding member 334 because the ball bonding member 334 can be copper-plated. During the wire bonding process, as the ball bonding member 334 is heated, the pressure from the capillary instrument described below forces the ball bonding member 334 to enter the recess 312 and surround the recess to form a bonding wire 336 (i.e., at the interface between the ball bonding member 334 and the bonding pad 308). During this process, the ball bonding member 334 will adhere to the bottom surface of the recess 312 and the inner surface of the side wall of the recess 312. The ball bonding member 334 will also adhere to the top surface of the bonding pad 308 adjacent to the recess 312. Thus, the recess 312 increases the surface area of the joint pad 308 to provide adhesion for the ball joint 334 .
[0039] At 218, a molding compound 338 is formed over the die assembly 314. The molding compound 338 encapsulates the die 302 including the bonding pads 308, the ball bonds 334, and the wire bonds 330, thereby producing Figure 3K In the example shown, the molding compound 338 covers all surfaces of the lead frame 320 except one surface, wherein the uncovered one surface faces away from the die assembly 314 .
[0040] Figures 4A-4E A process 400 is shown of attaching wire bonds 402 to a die 404 and terminal leads 406 using a capillary instrument 408. Figure 4A In FIG. 4 , a wire bond 402 is clamped into a capillary instrument 408 via a wire clamp 410 and a ball bond (eg, melted / molten wire bond material) 412 is attached to a first end 414 of the wire bond 402. Figure 4B , capillary instrument 408 is lowered until ball bond 412 contacts bond pad 416 on die 404 (cavity not shown for simplicity and clarity). Figure 4C In FIG. 4 , capillary instrument 408 is raised away from die 404, attaching ball bonds 412 and wire bonds 402 to bond pads 416. Figure 4D In the embodiment, the capillary instrument 408 is lowered onto the terminal lead 406 and the second end 418 of the wire bond 402 is attached to the terminal lead 406. Figure 4E In the embodiment of the present invention, the wire bond 402 is cut and the capillary instrument is raised away from the terminal lead 406 so that the second end 418 of the wire bond 402 is attached to the terminal lead 406 .
[0041] Figures 5A-5C, 6A-6C and 7A-7C are illustrations of three different example capillary instrument tip configurations. When the ball joint is attached to the joint pad, a force vector is generated by the capillary instrument and distributed toward the ball joint. However, the distribution of the force vector across the ball joint will vary based on the configuration of the capillary tip. For example, Figures 5A-5C An example of a capillary instrument 500 including a single internal chamfer tip configuration 502 is shown (in Figure 5B ). Figure 5C As shown, force vectors 504 converge at a single central location, as indicated by the intersection of the two force vectors 504. Figure 5C In the example shown, only two force vectors are shown for simplicity and clarity. However, it should be understood that the number of force vectors is greater than two. Therefore, Figure 5C The examples shown in are for illustrative purposes only and are not intended to limit the scope of the invention. Thus, when the bonding ball is attached to the bonding pad, the ball bonding pieces are unevenly distributed across the bonding pad, thereby creating a gap at the bonding line (i.e., at the interface between the ball bonding piece and the bonding pad).
[0042] Figures 6A-6C Another example of a capillary instrument 600 including a double internal chamfer tip configuration 602 is shown (in Figure 6B ). Figure 6C As shown, the force vectors 604 converge in a pair of locations, as indicated by the intersection points of the four force vectors 604. Figure 6C In the example shown, only four force vectors are shown for simplicity and clarity. However, it should be understood that the number of force vectors is greater than four. Therefore, Figure 6C The example shown in is for illustrative purposes only and is not intended to limit the scope of the invention. Thus, in this example, when the bonding ball is attached to the bonding pad, the ball bonding pieces are more evenly distributed across the bonding pad, thereby alleviating the occurrence of cracks and gaps at the bonding line (i.e., at the interface between the ball bonding piece and the bonding pad).
[0043] Figures 7A-7C Another example of a capillary instrument 700 is shown, which includes a convex inner chamfer tip configuration 702 (in Figure 7B ). Figure 7C As shown, due to the convex shape of the tip 702, the force vectors 704 converge in a plurality of locations indicated by the intersection points of the eight force vectors 704. Figure 7C In the example shown, only eight force vectors are shown for simplicity and clarity. However, it should be understood that the number of force vectors is greater than eight. Therefore, Figure 7CThe example shown in is for illustrative purposes only and is not intended to limit the scope of the invention. Thus, in this example, when the bonding ball is attached to the bonding pad, the ball bonding pieces are evenly distributed across the bonding pad, thereby alleviating the occurrence of cracks and gaps at the bonding line (i.e., at the interface between the ball bonding piece and the bonding pad).
[0044] The examples of the present disclosure are described above. Of course, it is not possible to describe every conceivable combination of components or methods for the purpose of describing the present disclosure, but a person of ordinary skill in the art may recognize that many other combinations and arrangements of the present disclosure are possible. Therefore, the present disclosure is intended to cover all such changes, modifications and variations that fall within the spirit and scope of the appended claims. In addition, where the present disclosure or claims describe "one", "one", "first" or "another" element or its equivalent, it should be interpreted as including one or more such elements, neither requiring nor excluding two or more such elements. In addition, insofar as the term "comprising" is used in a specific embodiment or in the claims, this term is intended to be inclusive of endpoints in a manner similar to the term "including", as explained when "including" is used as a transition word in the claims. Finally, the term "based on" is interpreted to mean at least partially based on.
Claims
1. An electronic device, comprising: substrate; a die having an active surface, the die being disposed on the substrate; a bond pad disposed on the active surface of the die, the bond pad including a recess defined in a top surface of the bond pad; a ball joint disposed in the recess of the joint pad; a wire bond attached to the ball bond and the substrate; as well as A molding compound encapsulates the die, the bond pads, and the ball bonds, the molding compound covering all surfaces of the substrate except one surface, wherein the uncovered one surface faces away from the die. 2 . The electronic device of claim 1 , wherein an interface between the ball joint and the bonding pad forms a bond line that is substantially free of cracks and gaps. 3 . The electronic device according to claim 1 , wherein the recess has a depth of approximately 1-3 μm and a width of approximately 30-110 μm.
4. The electronic device of claim 1, wherein the substrate is a lead frame, the lead frame comprising a die pad and conductive terminals, the die being attached to the die pad via a die attach material, and the wire bonds being attached to the conductive terminals.
5. A method comprising: providing a die having an active surface; forming bonding pads on the active surface of the die; forming a recess in a top surface of the bonding pad; placing the die on a substrate; attaching a wire bond from the bond pad to the substrate; as well as A molding compound is formed over the die.
6. The method of claim 5 , wherein forming a bonding pad on the active surface of the die comprises: forming a layer of photoresist material over the active surface of the die, the layer of photoresist material having openings patterned therein; and depositing a metal plating layer in the openings of the layer of photoresist material. 7 . The method of claim 5 , wherein forming a recess in a top surface of the bonding pad comprises performing an etching process to form the recess. 8 . The method of claim 5 , wherein forming a recess in a top surface of the bonding pad comprises performing a first electroplating process to form the bonding pad, and performing a second electroplating process to build up a sidewall of the bonding pad to form the recess.
9. The method of claim 5, wherein attaching a wire bond from the bonding pad to the substrate comprises: attaching a first end of the wire bond to a ball bond; depositing the ball bond in the recess of the bonding pad via a capillary instrument; and attaching a second end of the wire bond to the substrate via the capillary instrument.
10. The method of claim 9, wherein attaching the wire bonds from the bond pads to the substrate is performed at a low temperature in the range of approximately 90°C - 120°C.
11. The method of claim 9, wherein the capillary instrument has a double internally chamfered tip to evenly distribute a force vector across the ball bond when attaching the first end of the wire bond to the bond pad.
12. The method of claim 9, wherein the capillary instrument has a convex internal chamfered tip to evenly distribute a force vector across the ball bond when attaching the first end of the wire bond to the bond pad.
13. The method of claim 9, wherein the molding compound encapsulates the die, the bonding pads, the ball bonds, and the wire bonds, the molding compound covering all surfaces of the substrate except one surface, wherein the uncovered one surface faces away from the die.
14. A method comprising: Manufacturing of bare die assemblies, including: providing a die having an active surface; forming a layer of photoresist material over the active surface of the die, the layer of photoresist material having openings patterned therein; depositing a metal plating layer in the openings of the layer of photoresist material to form bonding pads on the active surface of the die; and forming a recess in a top surface of the bonding pad; placing the die on a die pad of a lead frame; attaching wire bonds from the bond pads to the lead frame; and A molding compound is formed over the die. 15 . The method of claim 14 , wherein forming a recess in a top surface of the bonding pad comprises performing an etching process to form the recess. 16 . The method of claim 14 , wherein forming a recess in a top surface of the bond pad comprises performing a first electroplating process to form the bond pad, and performing a second electroplating process to build up a sidewall of the bond pad to form the recess.
17. The method of claim 14, wherein attaching the wire bonds from the bond pads to the lead frame is performed at a low temperature in the range of approximately 90°C - 120°C.
18. The method of claim 14, wherein attaching a wire bond from the bonding pad to the lead frame comprises: attaching a first end of the wire bond to a ball bond; depositing the ball bond in the recess of the bonding pad via a capillary instrument; and attaching a second end of the wire bond to the lead frame via the capillary instrument.
19. The method of claim 18, wherein the capillary instrument has a double internally chamfered tip to evenly distribute a force vector across the ball bond when attaching the first end of the wire bond to the bond pad.
20. The method of claim 18, wherein the capillary instrument has a convex internal chamfered tip to evenly distribute a force vector across the ball bond when attaching the first end of the wire bond to the bond pad.