Thermocompression bonding tips and related apparatus and methods

Abstract

A bonding tip for thermocompression bonding a bottom surface is disclosed, comprising a die contact area and a low surface energy material covering at least a portion of the bottom surface. The low surface energy material may cover substantially the entire bottom surface, or only a peripheral portion surrounding the die contact area. The die contact area may be recessed relative to the peripheral portion to a depth at least as great as the thickness of a semiconductor die to be received in the recessed die contact area. A thermocompression bonding method is also disclosed.

Description

[0001] Priority claim

[0002] This application claims the benefit of the filing date of U.S. Patent Application No. 15 / 625,676, filed on June 16, 2017, for “Thermocompression Bond Tips and Related Apparatus and Methods.” Technical Field

[0003] Embodiments disclosed herein relate to bonding tips for thermocompression bonding. More particularly, embodiments disclosed herein relate to bonding tips for use with non-conductive films in thermocompression bonding between conductive elements of stacked electrical components, including but not limited to semiconductor dies and other substrates. Background Art

[0004] Thermocompression bonding (hereinafter also referred to simply as "bonding" for brevity) has been used in semiconductor packaging technology for quite some time. The process can be used to bond "flip chip" dies, which are configured with conductive elements protruding from the die surface (usually the active surface) in the form of bumps, balls, pillars or studs. The conductive elements can be configured as so-called "C4" bumps, which include solder balls on under-bump metallization (UBM); "C2" bumps, which include copper pillars with solder caps; and copper pillars for Cu-to-Cu diffusion bonding (also known as "direct" bonding).

[0005] As the pin count of semiconductor devices increases and the spacing between adjacent conductive elements decreases significantly, C4 technology exhibits an increased likelihood of shorting between adjacent solder bumps during reflow of the relatively large solder mass of the bumps. C2 technology achieves relatively high pin counts and tighter spacing with a lower tendency to short. Cu-to-Cu direct bonding also offers higher pin counts and tighter spacing than C4 technology, but requires higher precision component alignment.

[0006] The use of pre-assembled underfill applied to the components to be joined enables relatively tight post-to-post spacing for C2 and Cu diffusion bonding techniques, and enables narrower bond lines between components, as compared to post-assembly underfill, such as capillary underfill (CUF). The categories of pre-assembled underfill can be characterized as non-flow underfill (NUF), non-conductive paste (NCP) underfill, and non-conductive film (NCF) underfill, the latter of which may also be referred to as wafer-level underfill (WLUF). NUF or NCP may be applied at the die level to components such as semiconductor dies having C2 or Cu posts thereon and located on the die surface and above the posts, or applied at the wafer level to arrays of non-singulated semiconductor dies, by spin coating, needle dispensing, or vacuum assisted processes. NCF underfill is applied at the wafer level to semiconductor dies having C2 or Cu posts thereon by film lamination. In the case of C2 posts, the NCF may also include flux. Example sizes for C2 posts include 10 μm Cu posts initially topped with 40 μm Sn-Ag solder caps, 26 μm Cu posts capped with 2 μm Ni and 20 μm Sn, 15 μm Cu posts capped with 3 μm Ni and 15 μm Sn. It is also known to employ conductive elements comprising 5 μm Ni+Sn without copper posts. Post-to-post spacing with pre-assembled underfill (e.g., NUF, NCP, or NCF underfill) can be as small as 10 μm, and bond wires as thin as about 20 μm to about 30 μm when Cu posts are employed. If Cu posts are not employed, the bond wires can be 15 μm or less.

[0007] NCF underfill lamination on a wafer can be achieved relatively quickly, evenly distributed over, for example, the die surface, to enhance the ability to achieve uniform and void-free underfill. NCF materials are conventionally applied using a carrier film (e.g., a polyethylene terephthalate (PET) film), wherein the NCF material is pressed against the wafer surface using, for example, a roller. The carrier film is then peeled off, and a portion of the film depth can then optionally be removed (e.g., cut) to expose the solder of the cap. Even though NCF underfill requires less underfill material than NUF and NCP technologies, thereby reducing the possibility of excess underfill flowing out between stacked components, there is still enough risk of flowing out to contaminate the bonding tip, which can also be characterized as a bonding "tool" for a thermocompression bonding device during a bonding operation. Controlling the film thickness of the NCF material and the bonding process parameters has been used to reduce the possibility of forming an excessively large "round corner" of the underfill at the periphery of the bonding line, but has not been completely successful, thereby reducing product yield.

[0008] Figure 11 is a bottom elevation view of a conventional bonding tip 100, the bottom surface 102 of which contacts the back side of a semiconductor die that may carry an under-bump metallization layer (UBM) when in use. Conductive posts protrude from the opposite active surface of the semiconductor die. The bonding head of the thermocompression bonding equipment that fixes the bonding tip 100 applies heat and pressure through the bonding tip 100 to achieve mechanical and electrical connections between each post and the aligned conductive elements on the component below the die. The length and width of the conventional bonding tip used in the thermocompression bonding in conjunction with NCF (WLUF) are sized to correspond to not more than the length and width of the semiconductor die to be picked up, placed, heated and pressed against the substrate for bonding, so as to avoid contact of the exposed peripheral area of ​​the bottom surface 102 with the bottom filling material (e.g., NCF material). However, the size of the conventional bonding tip cannot be significantly smaller than the semiconductor die to be bonded, so as to place a uniform compressive force on the die for bonding and also avoid stress concentration that may crack very thin dies (e.g., about 50 μm or less) that are typically used in multi-die stacking and in mobile device chip assemblies. Die thicknesses as small as about 30 μm to about 40 μm are known. Additionally, conventional bonding tips cannot be sized significantly smaller than the semiconductor die to be bonded because temperature uniformity of a magnitude sufficient for bonding must be maintained across the entire die area, otherwise interconnects near the die edge, near or outside the periphery of the bonding tip may result in poorly formed and connected solder joints (commonly referred to as "cold joints").

[0009] The channel 104 in the bottom surface 102, which is in communication with the port 106, is used to apply a vacuum to pick up the semiconductor die to be bonded using the bonding head of the thermocompression bonding equipment, and place the die in a suitable position to be bonded to the conductive element of the substrate (which may, but is not limited to, include another semiconductor die). In the case of the C2 pillar, the applied heat is sufficient to melt the solder cap on the copper pillar, after which the bonding tip is rapidly cooled to solidify the solder. In the case of Cu to Cu direct bonding, the copper of the pillar is diffusion bonded to the copper conductive element of the substrate. During the bonding operation, the NCF laminated to the active surface of the semiconductor die may flow outward from the periphery of the die as a fillet and flow upward sufficiently to contact and contaminate the bonding tip, which not only damages the bonding tip but also risks damage to future components contacted by the bonding tip. In addition, if the fillet flows over the back side of the die or even flows onto the back side of the die, there is a risk of die cracking when additional components are stacked and bonded to the die.

[0010] One possible solution to bond tip contamination is to use a film in the form of a strip, a section of which is placed over the surface of the bond tip that contacts the electrical component (e.g., semiconductor die) to be bonded prior to bonding, and then marking the film strip after each bonding operation to cover the bond tip with a new film section. Applicants do not admit herein that the aforementioned apparatus or methods constitute prior art. Summary of the invention

[0011] In one embodiment, a thermocompression bonding apparatus includes a bonding tip having a bottom surface including a die contact area, and a low surface energy (LSE) material covering at least a portion of the bottom surface.

[0012] In another embodiment, a method for thermocompression bonding a semiconductor die including pillars protruding from a surface thereof includes picking up the semiconductor die using a die contact area of ​​a bottom surface of a bonding tip of a thermocompression bonding device, the semiconductor die carrying a non-conductive film (NCF) above the surface, the pillars protruding from the surface, the bottom surface having a length and width greater than that of the semiconductor die so that a peripheral portion of the bottom surface surrounding the die contact area is exposed. The semiconductor die is moved to a position where the posts are aligned with conductive elements of a substrate using the bonding tip; heat is applied to the semiconductor die and the NCF material is converted to a flowable state; a force is applied to the semiconductor die using the bonding tip during the application of heat to press the posts against the aligned conductive elements, fill the bond lines between the semiconductor die and the substrate with the flowable NCF material around and between the posts and cause at least one fillet of the flowable NCF material to extrude from at least a portion of the periphery of the semiconductor die and contact at least a portion of the exposed peripheral portion of the bottom surface of the bonding tip; the posts are bonded to the aligned conductive elements and the NCF material is at least partially cured. The bonding tip is retracted from the semiconductor die without bonding the fillet of the NCF material to the exposed peripheral portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a bottom elevation view of a conventional bonding tip of a thermocompression bonding apparatus;

[0014] Figure 2 is a bottom elevation view of an engagement tip according to an embodiment of the present invention;

[0015] Figure 3A During the bonding operation of semiconductor dies Figure 2 A schematic side view of a joint tip of ;

[0016] Figure 3BAfter bonding the semiconductor die Figure 2 A schematic side view of a joint tip of ;

[0017] Figure 4 is a bottom elevation view of an engagement tip according to another embodiment of the present invention;

[0018] Figure 5A yes Figure 4 A schematic cross-sectional side view of an embodiment of an engagement tip of;

[0019] Figure 5B yes Figure 4 A schematic cross-sectional side view of another embodiment of an engagement tip;

[0020] Figure 6 is a bottom elevation view of an engagement tip according to a further embodiment of the present invention;

[0021] Fig. 7A During the bonding operation of semiconductor dies Figure 6 A schematic partial cross-sectional side view of a joint tip of ;

[0022] Figure 7B After bonding the semiconductor die Figure 6 a schematic partial cross-sectional side view of a joining tip of ; and

[0023] Figure 8 is a simplified schematic perspective view of a thermocompression bonding apparatus employing a bonding tip of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following description provides specific details (such as size, shape, material composition and orientation) in order to provide a thorough description of embodiments of the present invention. However, it will be understood by those skilled in the art that embodiments of the present invention may be practiced without necessarily adopting these specific details. Embodiments of the present invention may be practiced in conjunction with conventional manufacturing techniques used in the industry. In addition, the description provided below does not form a complete process flow, structure or equipment. The following detailed description only describes the process actions and structures necessary for understanding embodiments of the present invention.

[0025] The drawings presented herein are for illustrative purposes only and are not intended to be actual views of any particular material, component, structure, device, or system. Variations in the shapes depicted in the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the embodiments described herein should not be construed as being limited to specific shapes or regions as described, but rather include shape deviations resulting from, for example, manufacturing. For example, an area described or described as box-shaped may have rough and / or nonlinear features, and an area described or described as circular may include some rough and / or linear features. In addition, the sharp angles between the illustrated surfaces may be rounded and vice versa. Therefore, the areas illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of the area and do not limit the scope of the claims. The drawings are not necessarily drawn to scale.

[0026] As used herein, the terms "comprising," "including," "containing," "characterized by," and their grammatical equivalents are inclusive or open-ended terms that do not exclude additional, unrecited elements or methodological actions, but encompass the more restrictive terms "consisting of," and "consisting essentially of," and their grammatical equivalents. As used herein, the term "may," with respect to a material, structure, feature, or methodological action, indicates that this is contemplated for use in implementations of embodiments of the invention and this term is used in preference to the more restrictive term "is" in order to avoid any suggestion that other compatible materials, structures, features, and methods that may be used in combination therewith should or must be excluded.

[0027] As used herein, the terms "longitudinal", "vertical", "lateral", and "horizontal" are relative to a major plane of a substrate (e.g., a base material, a base structure, a base construction, etc.) in or on which one or more structures and / or features are formed and are not necessarily defined by the earth's gravitational field. A "lateral" or "horizontal" direction is a direction substantially parallel to the major plane of a substrate, while a "longitudinal" or "vertical" direction is a direction substantially perpendicular to the major plane of a substrate. A major plane of a substrate is defined by a substrate surface having a relatively large area compared to other substrate surfaces.

[0028] As used herein, spatially relative terms (e.g., "below," "below," "lower," "bottom," "above," "up," "upper," "top," "front," "back," "left," "right," etc.) may be used to describe the relationship of an element or feature as illustrated in the figures to another (several) element or feature for ease of description. Unless otherwise specified, spatially relative terms are intended to encompass different material orientations other than the orientation depicted in the figures. For example, if the material in the figure is turned upside down, an element described as being "on" or "above" or "above" or "on top" of other elements or features would then be oriented "below" or "below" or "below" or "on bottom" of the other elements or features. Thus, the term "on" may encompass both above and below orientations, depending on the context in which the term is used, as will be apparent to one of ordinary skill in the art. The material may be oriented in other ways (e.g., rotated 90 degrees, inverted, inverted) and the spatially relative descriptors used herein interpreted accordingly.

[0029] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0030] As used herein, the terms "configured" and "configuration" refer to the size, shape, material composition, orientation, and arrangement of at least one structure and at least one device to facilitate operation of the structure and one or more of the devices in a predetermined manner.

[0031] As used herein, the term "substantially" with respect to a given parameter, property, or condition means and includes to the extent that one of ordinary skill in the art would understand that the given parameter, property, or condition meets a degree of variance (e.g., within acceptable manufacturing tolerances). For example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be met by at least 90.0%, met by at least 95.0%, met by at least 99.0%, or even met by at least 99.9%.

[0032] As used herein, the term "about" with respect to a given parameter is inclusive of the stated value and has the meaning dictated by the context (eg, it includes the degree of error associated with measurement of the given parameter).

[0033] A thermocompression bonding apparatus is disclosed that includes a bonding tip having a bottom surface including a die contact area and a low surface energy (LSE) material covering at least a portion of the bottom surface.

[0034] Now refer to the accompanying drawings Figure 2, illustrating a bottom surface 202 of a bonding tip 200 according to an embodiment of the present invention. Like the bonding tip 100, the bonding tip 200 includes access ports (not shown) for applying a vacuum to hold the semiconductor die SD (see Figure 3A and 3B ) to bond through the back side 204 of the semiconductor die SD against the bottom surface 202 (not shown). However, unlike the bonding tip 100, the bottom surface 202 of the bonding tip 200 is covered with a low surface energy (LSE) material 208. For example, the LSE material 208 may include a parylene HT or N material, a fluoropolymer (such as a polytetrafluoroethylene (PTFE) material or a perfluoroalkoxy (PFA) material), graphene, or diamond-like carbon (DLC). Specific materials of the foregoing type may or may be formulated to accommodate the application of heat and remain in a solid state without decomposing at temperatures of, for example, about 300° C. or higher as used in a thermocompression bonding process. Thermocompression bonding temperatures are known to be as high as about 400° C. and can theoretically be as low as about 220° C. (the melting point of Sn). By definition, such LSE materials resist wetting by liquids, exhibit large contact angles with droplets placed on the surface of the LSE material, and resist bonding to other materials. The LSE material 208 may cover the bottom surface 202 with a thickness of, for example, about 2 μm to about 10 μm, although other thicknesses may be used. For example, parylene may be conformally applied from a thickness between about 0.1 μm to about 76 μm. The drawings herein exaggerate the thickness of the LSE material for clarity and are therefore not necessarily drawn to scale.

[0035] Reference Figure 3A, depicting a bond tip 200 bonding a semiconductor die SD to a substrate S under applied heat and pressure, the pressure being indicated by arrows 210 as a bond head (not shown) to which the bond tip 200 is secured applies a downward force. Under the applied heat and pressure, posts P protruding from an active surface 212 of the semiconductor die SD penetrate NCF 214 that had been previously applied at the wafer level prior to singulation to make contact with aligned conductive elements C of the substrate S. As a result of the applied heat and pressure, the NCF material 214 (shown as transparent for clarity) becomes flowable and flows outwardly and upwardly from between the semiconductor die SD and the substrate S along a periphery 218 of the semiconductor die SD as fillets 216. With the bottom surface 202 of the bond tip 200 covered with LSE material 208, the LSE material 208 prevents contamination of the bond tip 200 as the fillet 216 may contact the bottom surface 202. It should be noted that, and unlike conventional bonding tips, due to the presence of LSE material 208 on bottom surface 202, bonding tip 200 may have a width and length greater than the width and length of semiconductor die SD, thereby preventing fillet 216 from reaching and contaminating the back side of semiconductor die SD. For example, bonding tip 200 may extend beyond periphery 218 of semiconductor die SD by as much as a lateral distance of about 1 mm or more. The ability to employ bonding tip 200 having dimensions significantly greater than conventional bonding tips enables one "oversized" bonding tip to be used for many semiconductor dies of different sizes and shapes, thereby saving processing costs.

[0036] like Figure 3B , after the bonding operation and the NCF material 214 has been partially solidified, the contact of the bonding tip 200 with the semiconductor die SD can be released when the bonded assembly is sufficiently cooled without adhering to and being contaminated by the NCF material of the fillet 216. Active cooling of the bonding tip 200 can be employed before the die is released, but may not be necessary to save cycle time because the partially solidified NCF can hold the semiconductor die SD in place so that the bonding tip cooling cycle can be started after the die is released and when the bonding head moves to pick up the next semiconductor die for bonding.

[0037] Reference Figure 4 , illustrating a bottom surface 302 of another embodiment of a bonding tip 300 according to the present invention. Like the bonding tip 200, the bottom surface 302 includes a vacuum channel that communicates with a vacuum port (not shown). Figure 2 , 3A However, the bottom surface 302 of the bonding tip 300 is only partially covered with the LSE material 208, which is only located outside the die contact area 308 on the peripheral portion 310. The semiconductor die SD is shown on the die contact area 308 with dashed lines.

[0038] like Figure 5A Described in Figure 5A 3 is a schematic cross-sectional side view of one embodiment of the bonding tip 300, the bottom surface 302 may include a recessed peripheral portion 310r outside the die contact area 308, the depth D1 of the recessed peripheral portion 310r substantially corresponding to the thickness T of the LSE material 208, so that the covered and uncovered portions of the bottom surface 302 are substantially coplanar. Figure 5A In the configuration, during bonding, the rounded corners (not shown) of the NCF material may contact the side surfaces of the semiconductor die SD (shown with dotted lines) and the LSE material 208 on the recessed peripheral portion 310r, but will be excluded from contacting the back side of the semiconductor die SD due to the contact with the LSE material 208 on the recessed peripheral portion 310r. When the bonding tip 300 is retracted, the rounded corners will be released from the LSE material 208 on the recessed peripheral portion 310r.

[0039] like Figure 5B Described in Figure 5B 3 is a schematic cross-sectional side view of another embodiment of a bonding tip 300, with a bottom surface 302 being substantially planar across its entire length and width, and a thickness T of LSE material 208 being applied to a peripheral portion 310 outside of a die contact area 308, such that the uncovered die contact area 308 of the bottom surface 302 is recessed relative to the outer surface of the LSE material. A semiconductor die SD is shown with dashed lines on the die contact area 308. Figure 5B In the configuration, the rounded corners (not shown) of the NCF material can be prevented from at least partial contact with the side of the semiconductor die SD adjacent to the die contact area 308 during bonding due to the presence of the LSE material 208 protruding from the bottom surface 302 above the peripheral portion 310, and will be released from the LSE material 208 on the peripheral portion 310 when the bonding tip 300 is retracted.

[0040] Reference Figure 6 , illustrating a bottom surface 402 of another embodiment of a bonding tip 400 according to the present invention. As with bonding tips 200 and 300, bottom surface 402 includes a vacuum channel that communicates with a port. Figures 2 to 5BThe LSE material 208 is described as being used on the bottom surface 402. However, like the bottom surface 302 of the bonding tip 300, the bottom surface 402 is only partially covered with the LSE material 208 at the periphery of the die contact area 408 and outside the die contact area 408, on a peripheral portion 410 of the bottom surface 402. Furthermore, as compared to the previous embodiments, the die contact area 408 may be substantially recessed compared to the peripheral portion 410 by a depth D2 that substantially corresponds to the thickness of the semiconductor die SD plus a distance that is less than the height of the pillars P protruding from the active surface of the semiconductor die SD (see Fig. 7A ). In other words, the maximum depth D2 may be as large as the thickness of the semiconductor die SD plus a value less than the height of the pillar. The minimum depth D2 may be less than the thickness of the semiconductor die SD, and the depth D2 depends slightly on the process. The length and width of the recess 414 are dimensioned to a close tolerance, for example, the length and width of the semiconductor die SD to be bonded plus about 50 μm to about 300 μm to substantially prevent the NCF fillet from flowing on the side of the semiconductor die SD and flowing to the back side of the semiconductor die SD. In addition, the transition region between each vertical sidewall 412 of the recess 414 of the external die contact region 408 and the adjacent region of the peripheral portion 410 may include a laterally outwardly extending bevel 416, which may prevent damage to the semiconductor die SD if there is a slight misalignment between the bonding tip 400 and the die when picking up the die from the singulated wafer on the film frame. The bevel 416 may be at an angle of, for example, about 30° to about 60° (eg, about 45°) with the associated sidewall 412 . The bevel 416 and the peripheral portion 410 of the bottom surface 402 are continuously covered with the LSE material 208 .

[0041] like Fig. 7A As shown in , when the bonding tip 400 applies heat and pressure to the semiconductor die SD (when bonded to another substrate S), a fillet 216 (shown as transparent for clarity) of the NCF material 214 may form around the periphery of the die, and an excess amount of the NCF material 214 from the fillet 216 may flow upward onto the bevel 416 as a peripheral protrusion 218. Unlike the bonding tips 200 and 300, the tight tolerance of the recess 414 relative to the semiconductor die SD constrains the possible upward extent of the fillet 216, so that the bevel 416 provides an additional volume of space into which the NCF fillet 216 may flow. Thus, the extent to which the NCF fillet 216 protrudes laterally beyond the sides of the semiconductor die SD may be limited by the extrusion of excess NCF material 214 into the additional volume of space, so that integrity is not compromised by subsequently encapsulating the encapsulant material on the semiconductor die SD with other dies in the stack or on an interposer or other substrate. As shown in FIG. Figure 7B, when the NCF material 214 is at least partially cured, the fillet 216 will be released from the LSE material 208. As described above, active cooling of the bond head and bond tip prior to die release is not necessary for implementation of embodiments of the present invention.

[0042] A method for thermocompression bonding a semiconductor die including pillars protruding from a surface thereof is disclosed, the method comprising: picking up the semiconductor die using a die contact area of ​​a bottom surface of a bonding tip of a thermocompression bonding apparatus, the semiconductor die carrying a non-conductive film (NCF) above the surface, the pillars protruding from the surface, the bottom surface having a length and a width greater than the length and the width of the semiconductor die so that a peripheral portion of the bottom surface surrounding the die contact area is exposed; moving the semiconductor die using the bonding tip to a position where the pillars are aligned with conductive elements of a substrate; applying heat to the semiconductor die and converting the NCF material into a flowable state; and During heat treatment, force is applied to the semiconductor die using the bonding tip to press the pillar against the aligned conductive element, fill the bonding line between the semiconductor die and the substrate with flowable NCF material around and between the pillars and cause at least one fillet of the flowable NCF material to extrude from at least a portion of the periphery of the semiconductor die and contact at least a portion of the exposed peripheral portion of the bottom surface of the bonding tip; bond the pillar to the aligned conductive element and at least partially cure the NCF material; and retract the bonding tip from the semiconductor die without bonding the fillet of the NCF material to the exposed peripheral portion.

[0043] Embodiments of the present invention may be used, for example but not limited to, to thermocompressively bond a semiconductor die to a supporting substrate such as an interposer, circuit board, or other higher level package, or to another semiconductor die. Non-limiting examples of the latter include thermocompressively bonding memory die to form stacks of, for example, four, eight, twelve, or sixteen die, and to form stacks of memory die on a logic die or a system-on-chip (SoC) die. One example of a multi-die assembly that may be fabricated using embodiments of the present invention is a hybrid memory cube comprising multiple (typically four) DRAM dies stacked on a controller die.

[0044] Thermocompression bonding equipment is well known in the art. For example, U.S. Patent Nos. 8,967,452, 9,093,549, 9,425,162, 9,426,898, 9,478,516, 9,576,928 and U.S. Patent Publication No. 2016 / 0343626 describe such equipment. The bonding tip according to embodiments of the present invention can be used with other conventional thermocompression bonding equipment without modifying the existing equipment (except for replacing the conventional bonding tip). Figure 8 A simplified schematic diagram of a thermocompression bonding apparatus 500 using a bonding tip 200, 300, or 400 is shown. Figure 8 5, a semiconductor die SD having a C2 pillar including a copper pillar 502 covered with solder 504 and protruding from an active surface 506 is aligned with a conductive element 508 in the form of a terminal pad of a substrate S. For example, the substrate S is depicted as being in the form of a circuit board, which is supported on a platform 510 for bonding. The bonding tips 200, 300, 400, shown in dashed lines for comparison with conventional bonding tips 512, have been used to pick up the semiconductor die SD and place it in alignment with the substrate S for bonding and apply a compressive force shown by arrows 514 to the semiconductor die SD. As previously described, the bonding tips 200, 300, and 400 exhibit a length and width that is greater than the length and width of the semiconductor die SD. Heat sufficient to cause the solder 504 to reflow may be applied through the platform 510, through the bonding tips 200, 300, 400 from a bonding head (not shown) to which the bonding tips 200, 300, 400 are fixed and / or from other sources. After bonding, the assembly of the semiconductor die SD and the substrate S is cooled, and removed from the platform 510 after retracting the bonding tips 200 , 300 , 400 .

[0045] Although certain illustrative embodiments have been described in conjunction with the figures, those of ordinary skill in the art will recognize and appreciate that the embodiments encompassed by the present invention are not limited to the embodiments explicitly shown and described herein. Rather, many additions, deletions, and modifications may be made to the embodiments described herein without departing from the scope of the embodiments encompassed by the present invention (e.g., the scope claimed below, including legal equivalents). Additionally, features from one disclosed embodiment may be combined with features of another disclosed embodiment while still being encompassed within the scope of the present invention.

Claims

1. A thermocompression bonding device, comprising: a bonding tip having a bottom surface including a die contact area; and A low surface energy (LSE) material covers substantially the entire bottom surface of the bonding tip and is completely positioned within the footprint of the bottom surface of the bonding tip, the LSE material being secured against removal during a thermocompression bonding operation, wherein the LSE material comprises a thickness in the range of 2 μm to 10 μm. 2 . The apparatus of claim 1 , wherein the bottom surface comprises a length and a width greater than a length and a width of the die contact area, and a peripheral portion of the bottom surface surrounds the die contact area.

3. The apparatus of claim 2, wherein the bottom surface comprises a single planar surface and the low surface energy material covering the bottom surface protrudes from the bottom surface. 4 . The apparatus of claim 1 , wherein the low surface energy material is selected from the group consisting of: polyparaxylene material, polytetrafluoroethylene (PTFE) material, perfluoroalkoxy (PFA) material, graphene, or diamond-like carbon (DLC).

5. The apparatus of claim 1, wherein the low surface energy material is formulated to accommodate the application of heat and remain substantially in a solid state without decomposing at temperatures desired for thermocompression bonding.

6. The apparatus of claim 5, wherein the temperature desired for thermocompression bonding is in the range of about 220°C to about 400°C.

7. The thermocompression bonding apparatus of claim 1, wherein the thermocompression bonding apparatus is configured to apply heat and pressure to a product passing through the bonding tip.

8. The thermocompression bonding apparatus of claim 7, wherein the LSE material is configured to remain on the bottom surface of the bonding tip before, while, and after the thermocompression bonding apparatus applies heat and pressure to the product.

9. A method of thermocompression bonding a semiconductor die including pillars protruding from a surface thereof, the method comprising: picking up the semiconductor die using a die contact area of ​​a bottom surface of a bonding tip of a thermocompression bonding device, the semiconductor die carrying a non-conductive film NCF above the surface, the pillars protruding from the surface, the bottom surface having a length and a width greater than the length and the width of the semiconductor die so as to expose a peripheral portion of the bottom surface surrounding the die contact area, the bottom surface having a low surface energy (LSE) material fixed on substantially the entire bottom surface of the bonding tip and completely positioned within a footprint of the bottom surface of the bonding tip, wherein the LSE material comprises a thickness in the range of 2 μm to 10 μm; moving the semiconductor die with the engagement tip to a position where the pillar is aligned with a conductive element of a substrate; applying heat to the semiconductor die and converting the NCF material into a flowable state; applying a force to the semiconductor die with the bond tip during the application of heat to press the posts against the aligned conductive elements, filling a bond line between the semiconductor die and the substrate with a flowable NCF material around and between the posts, and causing at least one fillet of the flowable NCF material to extrude from at least a portion of a periphery of the semiconductor die and contact the at least portion of the exposed periphery portion of the bottom surface of the bond tip; bonding the posts to the aligned conductive elements and at least partially curing the NCF material; and The bonding tip is retracted from the semiconductor die having the LSE material secured to the bottom surface thereof and without bonding the NCF material of the at least one rounded corner to any portion of the bottom surface to which the low surface energy LSE material is secured.

10. The method of claim 9, wherein bonding the pillar of the semiconductor die to the conductive element of the substrate comprises one of: reflowing solder of the pillar in contact with the conductive element by heating and cooling the solder to a solid state; and diffusion bonding the metal of the pillar to the conductive element by the heating and the cooling.

11. The method of claim 9, wherein moving the semiconductor die with the bonding tip to a position wherein the pillar is aligned with a conductive element of a substrate comprises: The semiconductor die is moved to a position where the pillar is aligned with a conductive element of another semiconductor die.

12. A thermocompression bonding apparatus configured to apply heat and pressure to a product, the thermocompression bonding apparatus comprising: An engagement tip comprising: a die contact area on a bottom surface of the bonding tip; and a low surface energy (LSE) material covering substantially the entire bottom surface of the bonding tip and being positioned entirely within a footprint of the bottom surface of the bonding tip, the LSE material being configured to remain covering the bottom surface before, while, and after the thermocompression bonding apparatus applies heat and pressure to the product, wherein the LSE material comprises a thickness in a range of 2 μm to 10 μm.

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