Packaging structure and forming method thereof

Abstract

A package structure is provided. The packaging structure comprises a substrate; a package component bonded to the substrate; a cap disposed over the package assembly and the substrate; and an interface structure sandwiched between the package components. The package assembly includes: a first die; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent the first die and the second die. The interface structure includes an adhesive layer disposed over the underfill and the molding compound; and a thermal interface material (TIM) layer over the adhesive layer, the first die, and the second die. The embodiment of the invention also relates to a packaging structure and a forming method thereof.

Description

Technical Field

[0001] Embodiments of the present application relate to a packaging structure and a method for forming the same. Background Art

[0002] In some three-dimensional integrated circuits (3DICs), the device die is bonded to a package substrate to form a package. The heat generated by the device die during operation needs to be dissipated to prevent performance degradation or even physical damage. To dissipate heat, a metal cap may be bonded to the package substrate to bond the device die. The device die may experience warping due to temperature changes. Warping may strain the bond between the device and the metal cap. Summary of the invention

[0003] Some embodiments of the present application provide a packaging structure, comprising: a substrate; a packaging assembly bonded to the substrate and comprising: a first die; a second die laterally spaced apart from the first die by a bottom filler; and a molding compound adjacent to the first die and the second die; a cover disposed over the packaging assembly and the substrate; and an interface structure sandwiched between the packaging assembly and the cover, the interface structure comprising: an interface layer disposed over the bottom filler and the molding compound; and a thermal interface material (TIM) layer located over the interface layer, the first die, and the second die.

[0004] Other embodiments of the present application provide a packaging structure, comprising: a substrate; a packaging assembly bonded to the substrate and comprising: a first die; a second die laterally spaced apart from the first die by a bottom filler; and a molding compound adjacent to the first die and the second die; a cover disposed above the packaging assembly and the substrate; and an interface structure sandwiched between the packaging assembly and the cover, wherein the cover includes a convex surface that partially extends into the interface structure.

[0005] Still other embodiments of the present application provide a method for forming a packaging structure, comprising: bonding a packaging assembly to the front side of a substrate, the packaging assembly comprising: a first die; a second die laterally spaced apart from the first die by a bottom filler; and a molding compound adjacent to the first die and the second die; selectively dispensing an adhesive layer over the bottom filler and a top surface of the molding compound; depositing a thermal interface material (TIM) over the adhesive layer, the first die, and the second die; after the deposition, placing a cover over the packaging assembly and the substrate; and curing the adhesive layer and the thermal interface material. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The disclosed embodiments are best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with standard practice in the industry, the various components are not drawn to scale and are only used for illustration purposes. In fact, the size of the various components may be arbitrarily increased or reduced for clarity of discussion.

[0007] Figure 1 A flow chart of a method for forming a package structure according to various aspects of an embodiment of the present disclosure is shown.

[0008] Figures 2 to 8 The process of various aspects according to the embodiments of the present disclosure is shown. Figure 1 Partial cross-sectional views or top views of a work-in-progress (WIP) structure at various steps of the method.

[0009] Fig. 9 A flow chart of a method for forming a package structure according to various aspects of an embodiment of the present disclosure is shown.

[0010] Figures 10 to 12 The process of various aspects according to the embodiments of the present disclosure is shown. Fig. 9 Partial cross-sectional views of a work-in-progress (WIP) structure at various steps of the method.

[0011] Fig.13 A flow chart of a method for forming a package structure according to various aspects of an embodiment of the present disclosure is shown.

[0012] Figures 14 to 17 The process of various aspects according to the embodiments of the present disclosure is shown. Fig.13 Partial cross-sectional views of a work-in-progress (WIP) structure at various steps of the method.

[0013] Figures 18 to 23 An alternative package structure manufactured using the methods described herein according to various aspects of embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0014] The following disclosure provides many different embodiments or examples for realizing the different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the disclosed embodiments. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly contacted, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the disclosed embodiments may repeat reference numerals and / or characters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0015] For ease of description, spatially relative terms such as "below," "beneath," "lower," "above," "upper," etc. may be used herein to describe the relationship of one element or component to another (or additional) elements or components as shown in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.

[0016] In addition, when "about," "approximately," etc. are used to describe a value or a range of values, as understood by one of ordinary skill in the art, the terms are intended to encompass values ​​within a reasonable range that takes into account variations that inherently occur during manufacturing. For example, based on known manufacturing tolerances associated with manufacturing components having properties associated with the value, a value or range of values ​​encompasses a reasonable range that includes the described value, such as within + / - 10% of the described value. For example, a material layer having a thickness of "about 5 nm" may include a size range from 4.25 nm to 5.75 nm, where the manufacturing tolerance associated with depositing material layers known to one of ordinary skill in the art is + / - 15%.

[0017] Semiconductor packaging technology was once considered a back-end process that facilitated the connection of chips to external circuits. This is no longer the case. Computing workloads are evolving so rapidly that they have brought packaging technology to the forefront of innovation. Modern packaging provides for the integration of multiple chips or dies into a single semiconductor device. Depending on the level of stacking, modern semiconductor packages can have a 2.5D structure or a 3D structure. In a 2.5D structure, at least two dies are coupled to a redistribution layer (RDL) structure or an interposer that provides chip-to-chip communication. At least two dies in a 2.5D structure are not stacked vertically one above the other. In a 3D structure, at least two dies are stacked one above the other and interact through through-silicon vias (TSVs). Depending on the process used, 2.5D structures and 3D structures can have an integrated fan-out (InFO) configuration or a chip-on-wafer-on-substrate. To provide additional structural integrity and to improve heat dissipation, a metal cover may be attached to the package structure. The die in the package assembly may warp during thermal cycling. The die warping creates strain on the bonding interface between the package structure and the metal cover. When the bond fails, the metal cover may partially delaminate from the package assembly, thereby interrupting heat dissipation. Because the top surface of the package structure includes different material interfaces, delamination may occur at the weaker bonding interface.

[0018] The disclosed embodiments provide different interface structures between the metal cover and the packaging structure to reduce or minimize the delamination caused by die warping. In some embodiments, the packaging assembly is bonded to the front side of the substrate. The packaging assembly includes a first die, a second die spaced laterally from the first die by an underfill, and a molding compound adjacent to the first die and the second die. An adhesive layer is selectively distributed above the top surface of the underfill and the molding compound. A thermal interface material (TIM) is deposited above the adhesive layer, the first die, and the second die. After depositing the TIM, a cover is placed above the packaging assembly and the substrate. The adhesive layer and the TIM are finally cured. The adhesive layer is well bonded to the underfill, the molding compound, and the TIM, and thus delamination is prevented. In some optional embodiments, one or more metal layers may be deposited above the packaging assembly or the metal cover to prevent delamination.

[0019] Various aspects of the disclosed embodiments will now be described in more detail with reference to the accompanying drawings. Figure 1 , Fig. 9 and Fig.13 FIG. 2 is a diagram showing various aspects of a work-in-progress (WIP) structure 200 ( Figures 2 to 8 , Figures 10 to 12 and Figures 14 to 17 Flowcharts of methods 1000, 1100, and 1200 of forming a package structure on a substrate (shown in FIG. 1 ). Methods 1000, 1100, and 1200 are merely examples and are not intended to limit the disclosed embodiments to those explicitly shown in methods 1000, 1100, or 1200. Additional steps may be provided before, during, and after methods 1000, 1100, or 1200, and some of the steps described may be replaced, eliminated, or moved around for additional embodiments of the methods. For simplicity, not all steps are described in detail herein. Figures 2 to 8 Describing method 1000, Figures 2 to 8 FIG. 1 is a partial cross-sectional view and a top view of a WIP structure 200 at different manufacturing stages according to various embodiments of the method 1000. Figures 10 to 12 Describing method 1100, Figures 10 to 12 1 is a partial cross-sectional view or top view of the WIP structure 200 at different manufacturing stages according to various embodiments of the method 1100. Figures 14 to 17 Describing method 1200, Figures 14 to 17 1 is a partial cross-sectional view or top view of a WIP structure 200 at different manufacturing stages according to various embodiments of the method 1200. Because the WIP structure 200 will be manufactured into a package structure, the WIP structure 200 may be referred to herein as a package structure 200 as the context requires. For the avoidance of doubt, Figures 2 to 8 , Figures 10 to 12 and Figures 14 to 17The X, Y and Z directions are perpendicular to each other. Throughout the embodiments of the present disclosure, the same reference numerals represent the same components unless otherwise explicitly described.

[0020] refer to Figure 1 , Figure 2 and Figure 3 The method 1000 includes block 1002 , in which the package assembly 300 is bonded to the front side surface 202F of the package substrate 202 . Figure 2 A schematic top view of the package assembly 300 over the package substrate 202 is shown. Figure 3 Shown along Figure 2 2 is a cross-sectional view of section AA' in FIG. In some embodiments, the package substrate 202 may include a printed circuit board (PCB) or the like. Figure 3 . In order to electrically couple to the package assembly 300, the package substrate 202 may include a plurality of contact pads above the front side surface 202F. In order to electrically couple to the solder components above the back side surface 202B, the package substrate 202 may also include a plurality of contact pads or under bump metallization (UBM) components above the back side surface 202B. At least one passive component 204 may be bonded to the package substrate 202. At least one passive component 204 may include a capacitor or a resistor. The package assembly 300 is a multi-die package (or multi-chip package) that may include more than one device die. The device die may also be referred to as a die or a chip. In Figure 2 and Figure 3 In the depicted embodiment shown in , the package assembly 300 includes a first die 220, a second die 230, a third die 240, a fourth die 250, a fifth die 260, and an interposer 210. Figure 2In some embodiments shown in , each of the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 is bonded to the interposer 210 by a plurality of microbumps 212. The space between the interposer 210 and each of the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 230 can be filled with a first bottom filler 214. The first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 are arranged side by side above the interposer 210. In order to provide structural integrity and improve stress absorption, the upper edge of the package assembly 300 is surrounded by a molding compound 216. The space between the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 can be filled with a first bottom filler 214. The molding compound 216 can also be referred to as a sealing layer 216. The package assembly 300 also includes a plurality of connection components 206 to interface with the package substrate 202. In some embodiments, the plurality of connection components 206 may include controlled collapse chip connection (C4) bumps or other solder bumps. The space between the package assembly 300 and the front side surface 202F of the package substrate 202 may be filled with a second bottom filler 208. Figure 2 In some embodiments shown in , the second underfill 208 can wrap around the sidewalls of the interposer 210 and the sidewalls of the first underfill 214. The molding compound 216 can be disposed on the second underfill 208 and in direct contact with the second underfill 208.

[0021] The interposer 210 may include a semiconductor material or glass. In one embodiment, the interposer 210 includes silicon (Si). In some optional embodiments, the interposer 210 includes silicon germanium (SiGe) or silicon carbon (SiC). Each of the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 may be a system on chip (SoC) die, a logic die, an application specific integrated circuit (ASIC) die, or a high bandwidth memory (HBM) die. In one embodiment, the first die 220 is a SoC die, and each of the second die 230, the third die 240, the fourth die 250, and the fifth die 260 is an HBM die. Each of the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 may include a plurality of transistors, such as a planar transistor, a fin field effect transistor (FinFET), a full-ring gate (GAA) transistor, a nanowire transistor, a nanosheet transistor, or other multi-gate transistors. The first bottom filler 214 and the second bottom filler 208 may include a polymer or an epoxy resin. The molding compound 216 may include a base material and a filler embedded in the base material. In some embodiments, the base material of the molding compound 216 may include a polymer, a resin, or an epoxy resin, and the filler may include spherical particles of silicon oxide (silicon dioxide) or aluminum oxide.

[0022] refer to Figure 2 , Figure 2 A top view of package assembly 300 is provided. Figure 2 In some embodiments shown in , the spaces between the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 can be filled with a first bottom filler 214, and the upper portion of the package assembly 300 can be surrounded by a molding compound 216. Each of the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260 can have a flip chip configuration, wherein their back sides of their device substrates are exposed on the top surface of the package assembly 300. In some embodiments, the device substrate may include silicon (Si). Therefore, different materials may be exposed on the top surface of the package assembly 300. The molding compound 216 exposed on the top surface of the package assembly 300 may include a polymer, a resin, an epoxy resin, silicon oxide (silicon dioxide), aluminum oxide, or a combination thereof. The first bottom filler 214 exposed on the top surface of the package assembly 300 may include a polymer or an epoxy resin.

[0023] In block 1002, the package assembly 300 is placed over the package substrate 202 such that the connection features 206 are vertically aligned with the contact pads on the front side surface 202F of the package substrate 202. A reflow process is performed such that the connection features 206 electrically couple the interposer 210 of the package assembly 300 to the package substrate 202. After the reflow process, the liquid precursor of the second underfill 208 is allowed to fill the gap between the interposer 210 and the front side surface 202F of the package substrate 202 by capillary action. Figure 2 and Figure 3 The package substrate 202 and package assembly 300 shown in FIG. 1 may be collectively referred to as a work-in-progress (WIP) structure 200 . During operations in the various blocks of method 100 , components may be added to WIP structure 200 , and the disclosed embodiments will continue to refer to the resulting structure as WIP structure 200 .

[0024] refer to Figure 1 and Figures 4 to 5 , the method 1000 includes a block 1004, wherein the interface adhesive 402 is selectively dispensed over the molding material 216 and the first underfill 214 exposed on the top surface of the package assembly 300. Figure 2 As described, the top surface of the package component 300 includes different exposed material surfaces. It has been observed through experiments and quality control data that the thermal interface material (TIM) cannot be well bonded to the surface of the molding compound 216 or the first bottom filler 214. The interface between the TIM and the molding compound 216 and between the TIM and the first bottom filler 214 may become a weak point with less than ideal bonding. When the package component 300 is subjected to thermal cycles, the first tube core 220, the second tube core 230, the third tube core 240, the fourth tube core 250 and the fifth tube core 260 may warp and not warp, thereby applying stress at the interface between the top surface of the package component 300 and the TIM. Weak points tend to fail prematurely and cause the TIM to delaminate from the package component 300. Such delamination may destroy the heat conduction path and hinder the heat from the package component 300. Dissipation.

[0025] In block 1004, the interface adhesive 402 is selectively deposited over the exposed surfaces of the molding compound 216 and the first bottom filler 214. In some embodiments, the selective dispensing can be implemented using a precision dispensing system. The precision dispensing system includes a precision dispensing head 400 that dispenses or injects the interface adhesive 402 in gel form, liquid form, or paste form. The stepper of the precision dispensing system can accurately move the precision dispensing head 400 over the exposed surfaces of the molding compound 216 and the first bottom filler 214, and dispense a suitable amount of the interface adhesive 402 via the precision dispensing head 400. In some embodiments, the interface adhesive 402 may include a die attach film (DAF) gel, silicone, polyimide (PI), or epoxy. Because the main function of the interface adhesive 402 is bonding, rather than heat dissipation / conduction, the interface adhesive 402 does not include a high thermal conductivity material, such as beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, metal (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite. The absence of these highly thermally conductive materials allows the interface adhesive 402 to have better adhesion to the molding compound 216 or the first underfill 214 than a TIM including highly thermally conductive materials. In addition, the absence of these highly thermally conductive materials also allows the interface adhesive 402 to have a smaller Young's modulus than a TIM including highly thermally conductive materials. As deposited, the interface adhesive 402 can have a thickness T. In some examples, the thickness T is between about 0.5 μm and about 30 μm.

[0026] In addition to the interface adhesive 402, adhesive 404 may also be dispensed over the bonding area of ​​a cover 410 (described below) on the package substrate 202. Since adhesive 404 is used to attach the cover to the top surface of the package substrate 202, adhesive 404 is also dispensed on the top surface of the package substrate 202. In some embodiments, adhesive 404 may include a die attach film (DAF) gel, silicone, polyimide (PI), or epoxy. Figure 4 In some embodiments shown in , adhesive 404 can be deposited on package substrate 202 using a dispensing system. The dispensing system includes a dispensing head 450 that dispenses or injects adhesive 404 in gel form, liquid form, or paste form. The stepper of the dispensing system can move the dispensing head 450 over the bonding area of ​​the cover 410 on the package substrate 202. Compared with the interface adhesive 402 that needs to be accurately dispensed to avoid hindering thermal conduction, the adhesive 404 does not need to be accurately deposited over the bonding area. Due to those reasons, the viscosity of the adhesive 404 can be greater than the viscosity of the interface adhesive 402. In order to accommodate the greater viscosity of the adhesive 404, the orifice diameter of the dispensing head 450 for the adhesive 404 is greater than the orifice diameter of the accurate dispensing head 400 for the interface adhesive 402.

[0027] refer to Figure 5, the exposed first underfill 214 between two adjacent dies may have a first dimension D1. It is desirable that the interface adhesive 402 dispensed in block 1004 completely covers the exposed first underfill 214 because the interface adhesive 402 adheres better to the first underfill 214 than the TIM layer 408 (described below). In some examples, the interface adhesive 402 over the exposed first underfill 214 should have a second dimension D2 that is equal to or greater than the first dimension D1.

[0028] refer to Figure 1 and Figure 6 to Figure 7 , method 1000 includes frame 1006, wherein a thermal interface material (TIM) layer 408 is deposited over the package assembly 300. For the purpose of the embodiments of the present disclosure, TIM refers to a material placed between an electronic device and a heat sink to improve the heat dissipation of the electronic device. Because voids and gaps introduce air into the heat conduction path, and air has a low thermal conductivity, one of the functions of the TIM is to fill the gap between the electronic device and the heat sink so as to reduce the voids and gaps. In order to perform the gap filling function well, the TIM or the precursor of the TIM should have reasonable fluidity or flexibility. In addition, the TIM should have sufficient thermal conductivity to promote thermal conduction. In addition, it is expected that the TIM has good stress absorption properties to protect the electronic device and prevent delamination. According to the embodiments of the present disclosure, in frame 1006, the TIM layer 408 can be applied in a gel form, a liquid form, or a paste form. In some embodiments, the TIM layer 408 can include a base material and a thermally conductive filler. In some examples, the base material for the TIM layer 408 may include silicone, resin, or epoxy, and the thermally conductive filler for the TIM layer 408 may include beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, metal (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite. Figure 6 As shown in FIG, a TIM layer 408 is deposited over the package assembly 300, including the backside of the device substrate for the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260, and the interface adhesive 402 using a dispensing system having a dispensing head 500. Because the interface adhesive 402 has been deposited to cover the molding compound 216 and the first underfill 214, the TIM layer 408 is spaced apart from the molding compound 216 and the first underfill 214 by the interface adhesive 402. In this regard, the interface adhesive 402 serves as an interface layer between the TIM layer 408 and the molding compound 216 on the one hand, and as an interface layer between the TIM layer 408 and the first underfill 214 on the other hand. In some embodiments, the TIM layer 408 may have a thickness between about 50 μm and about 150 μm.

[0029] Although adhesive 404 is described as being dispensed over packaging substrate 202 in block 1004 , it should be understood that it may also be dispensed over packaging substrate 202 in block 1006 before or after deposition of TIM layer 408 .

[0030] refer to Figure 1 and Figure 8 , method 1000 includes frame 1008, in which a cover 410 is placed over the package component 300 and the package substrate 202 to bond the adhesive 404 and the TIM 408. In some embodiments, the cover 410 can be formed of a metal or alloy, such as aluminum (Al), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), or their alloys. Exemplary alloys may include aluminum-copper alloys, iron-nickel alloys, or iron-nickel-cobalt alloys. Because the cover 410 is formed of a metal or a metal alloy, it can be referred to as a metal cover. The cover 410 has at least three functions. First, it acts as a heat sink to dissipate heat from the package component 300 through the TIM layer 408. Second, it provides structural rigidity to the package substrate 202 to prevent or reduce warping. Third, it creates a sealed environment to protect the package component 300. In block 1008, lid 410 is placed over package assembly 300 and package substrate 202 such that its bottom edge engages adhesive 404 on package substrate 202 and its bottom surface presses on and engages TIM layer 408. Figure 8 As shown in , because the interface adhesive 402 is precisely dispensed over the exposed molding compound 216 and the first underfill 214 in the dies (i.e., the first die 220, the second die 230, the third die 240, the fourth die 250, and the fifth die 260), the TIM layer 408 bonds most of the device substrate of the die and the lid 410. This allows the TIM layer 408 (which includes a highly thermally conductive material and is more thermally conductive than the interface adhesive 402) to conduct heat from the die to the lid 410.

[0031] refer to Figure 1 and Figure 8 , method 1000 includes block 1010, wherein interface adhesive 402, adhesive 404, and TIM 408 are cured. In some embodiments, interface adhesive 402, adhesive 404, and TIM layer 408 are heat curable. In these embodiments, Figure 8 The WIP structure 200 shown in FIG. 1 may be subjected to an annealing process 10 to cure the interface adhesive 402, the adhesive 404, and the TIM layer 408. In some embodiments, the annealing process 10 for curing the interface adhesive 402, the adhesive 404, and the TIM layer 408 may include a curing temperature between about 100° C. and about 200° C. and a curing time between about 1 hour and about 2 hours.

[0032] In the method 1000 described above, the interface adhesive 402 is dispensed over the exposed surfaces of the molding compound 216 and the first underfill 214 to serve as an interface layer to improve the adhesion between the TIM layer 408 and the molding compound 216 and the first underfill 214. Because the interface adhesive 402 is precisely dispensed, the TIM layer 408 still bonds to most of the surface of the die to maintain satisfactory thermal conduction to the lid 410. Fig. 9 The method 1100 shown in FIG. 1 differs from the method 1000 in at least three aspects. First, the method 1100 does not dispense any interface adhesive 402 over the package component 300. Second, the TIM layer 502 is dispensed over the package component 300 in such a manner that the thickness of the TIM layer 502 along the periphery of the package component 300 is greater than the thickness around the geometric center of the package component 300 to resist die warpage. Third, a convex cap having a convex bottom surface is used to adapt to the contour of the TIM layer 502.

[0033] refer to Fig. 9 and Figure 2 , the method 1100 includes a block 1102, in which the package assembly 300 is bonded to the front side surface 202F of the package substrate 202. The operations in block 1102 are substantially similar to those in block 1002 of the method 1000 described above. For this reason, the details of the operations in block 1102, the package assembly 300, and the package substrate 202 are omitted for brevity.

[0034] refer to Fig. 9 and Fig.10 , method 1100 includes box 1104, in which a TIM layer 502 is deposited over the package component 300 so that the TIM layer 502 is thicker around the periphery of the package component 300 than at the center of the top surface of the package component 300. In box 1104, the TIM layer 502 is dispensed as a liquid, gel, or paste using a dispensing system. The dispensing system includes a dispensing head 550 that dispenses or injects the TIM layer 502 (or its precursor) and an ultraviolet (UV) emitter 560 to emit UV rays 15 on the dispensed TIM layer 502. The stepper of the precision dispensing system can move the dispensing head 550 and the UV emitter 560 over the top surface of the package component 300, which can be rectangular or square in top view. In some embodiments, the precision dispensing system injects more TIM material along the periphery of the top surface of the package component 300 than around the geometric center of the top surface of the package component 300. When the TIM layer 502 is deposited, the UV emitter 560 emits UV rays 15 on the TIM layer 502 to partially cure the TIM layer 502. Partial curing allows the deposited TIM layer 502 to be fixed or maintain its shape. Fig.10In some embodiments shown in , the TIM layer 502 has a center thickness Tc and a peripheral thickness Tp. The peripheral thickness Tp is greater than the center thickness Tc. In some instances, the peripheral thickness Tp may be between about 100 μm and about 150 μm, and the center thickness Tc may be between about 30 μm and about 50 μm. In some instances, the thickness of the TIM layer 502 may increase linearly or parabolically from the center thickness Tc to the peripheral thickness Tp. Experimental and simulation results show that the stress caused by die warping is greater around the periphery of the package assembly than at the center of the package assembly. A larger peripheral thickness Tp provides more buffering to absorb additional stress along the periphery of the package assembly 300. In some embodiments, the TIM layer 502 may include a base material and a thermally conductive filler. In some examples, the base material for the TIM layer 502 may include silicone, resin, or epoxy, and the thermally conductive filler for the TIM layer 502 may include beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, metal (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite.

[0035] refer to Fig. 9 and Fig.10 , method 1100 includes frame 1106, wherein adhesive 404 is dispensed over packaging substrate 202. As will be described below, method 1100 attaches first convex cap 412 or second convex cap 414 to packaging component 300 and packaging substrate 202. First convex cap 412 or second convex cap 414 engages packaging component 300 through TIM layer 502, and is attached to the top surface of packaging substrate 202 through adhesive 404. In frame 1106, adhesive 404 is selectively deposited over the bonding area on the top surface of packaging substrate 202. When cap 410 is placed over packaging substrate 202, the lower edge of cap 410 will engage adhesive 404 in the bonding area. In some embodiments, selective dispensing of adhesive 404 can be implemented using a dispensing system. The dispensing system includes a dispensing head 450 that dispenses or injects adhesive 404 in gel form, liquid form, or paste form. The stepper of the dispensing system can accurately move the dispensing head 450 over the bonding area. In some embodiments, adhesive 404 may include a die attach film (DAF), silicone, polyimide (PI), or epoxy. Since the primary function of adhesive 404 is bonding, rather than heat dissipation / conduction, adhesive 404 does not include highly thermally conductive materials such as beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, metals (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite.

[0036] refer to Fig. 9 , Fig.11 and Fig.12 , method 1100 includes block 1108, wherein the convex cap ( Fig.11The first convex cover 412 or Fig.12 The second convex cap shown in FIG. 5 is placed over the package component 300 and the package substrate 202 to bond the adhesive 404 and the TIM layer 502. In some embodiments, the convex cap is Fig.11 In some other embodiments, the convex cap is Fig.12 . The first convex cap 412 and the second convex cap 414 can both be formed of a metal or alloy, such as aluminum (Al), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), or alloys thereof. The first convex cap 412 and the second convex cap 414 both have a convex bottom surface 4120 protruding from the bottom surface. Exemplary alloys may include aluminum-copper alloys, iron-nickel alloys, or iron-nickel-cobalt alloys. The first convex cap 412 includes a flush / flat top surface. The second convex cap 414 includes a concave top surface 4140. In frame 1108, the first convex cap 412 or the second convex cap 414 is placed over the package assembly 300 and the package substrate 202 so that its lower edge engages the adhesive 404 on the package substrate 202 and its convex bottom surface is pressed against and engages the TIM layer 502.

[0037] refer to Fig. 9 , Fig.11 and Fig.12 , method 1100 includes block 1110, wherein adhesive 404 and / or TIM layer 502 are cured. In some embodiments, adhesive 404 and TIM layer 502 are heat curable. In these embodiments, Fig.11 or Fig.12 The WIP structure 200 shown in FIG. 1 may be subjected to an annealing process 10 to cure the adhesive 404 and the TIM layer 502. In some embodiments, the annealing process 10 for curing the adhesive 404 and the TIM layer 502 may include a curing temperature between about 100° C. and about 200° C. and a curing time between about 1 hour and about 2 hours. In block 1110, the annealing process 10 fully cures the TIM layer 502, which was partially cured by the UV rays 15 in block 1104.

[0038] In the method 1000 described above, the interface adhesive 402 is dispensed over the exposed surfaces of the molding compound 216 and the first underfill 214 to serve as an interface layer to improve the adhesion between the TIM layer 408 and the molding compound 216 and the first underfill 214. Because the interface adhesive 402 is precisely dispensed, the TIM layer 408 still bonds to most of the surface of the die to maintain satisfactory thermal conduction to the lid 410. Fig.13 The method 1200 shown in FIG. 1 differs from the method 1000 at least in that the method 1200 utilizes an interfacial metal layer to improve adhesion.

[0039] refer to Fig.13 and Figure 2 , the method 1200 includes a block 1202, in which the package assembly 300 is bonded to the front side surface 202F of the package substrate 202. The operations in block 1202 are substantially similar to those in block 1002 of the method 1000 described above. For this reason, the details of the operations in block 1202, the package assembly 300, and the package substrate 202 are omitted for brevity.

[0040] refer to Fig.13 and Fig.14 , method 1200 includes block 1204, in which a first interface metal layer 602 is deposited over a top surface of package component 300. Although not explicitly shown in the figure, the first interface metal layer 602 is deposited over the top surface of package component 300 before package component 300 is singulated from a wafer. Before cutting the wafer including package component 300, the first interface metal layer 602 is deposited over the wafer by physical vapor deposition (PVD). After the singulation process, each of package components 300 includes the first interface metal layer 602 before it is mounted on package substrate 202. In some embodiments, the first interface metal layer 602 includes a metal or a metal nitride, such as silver (Ag), gold (Au), titanium (Ti), titanium nitride (TiN), copper (Cu), or tin (Sn). In an optional embodiment, the first interface metal layer 602 is selectively deposited on package component 300 after package component 300 is mounted on package substrate 202. In an alternative embodiment, a template may be placed over WIP structure 200, with the top surface of package component 300 exposed. Then, a PVD deposition process, such as sputtering, is performed to selectively deposit first interface metal layer 602 on the exposed top surface of package component 300. After deposition, the template is removed. Because first interface metal layer 602 is deposited using PVD, first interface metal layer 602 has a thickness of less than 2 μm, such as between about 1 μm and about 2 μm.

[0041] refer to Fig.13 and Fig.15, method 1200 includes box 1206, in which a second interface metal layer 604 is deposited over the bottom surface of the cover 410. The composition of the second interface metal layer 604 can be similar to the composition of the first interface metal layer 602. In some embodiments, the second interface metal layer 604 may include silver (Ag), gold (Au), titanium (Ti), titanium nitride (TiN), copper (Cu), or tin (Sn). In some embodiments, the second interface metal layer 604 can be deposited over the bottom surface of the cover 410 using PVD or electroplating. In order to selectively deposit the second interface metal layer 604 over a predetermined bonding area over the bottom surface of the cover 410, a template can be placed over the bottom surface of the cover 410, wherein the bonding area is exposed. Then, a PVD deposition process or an electroplating process is performed to deposit the second interface metal layer 604 over the bonding area. The deposited second interface metal layer 604 may have a surface area larger than the top surface of the package component 300. Fig.15 In some embodiments not explicitly shown in FIG. 4 , the entire bottom surface of the cover 410 is coated with the second interface metal layer 604. This ensures that the second interface metal layer 604 is located between the package component 300 and the bottom surface of the cover 410. When the second interface metal layer 604 is deposited using PVD, the second interface metal layer 604 has a thickness of less than 2 μm, such as between about 1 μm and about 2 μm. When the second interface metal layer 604 is deposited using electroplating, the second interface metal layer 604 has a thickness between about 1 μm and about 3 μm.

[0042] refer to Fig.13 and Fig.16 , method 1200 includes box 1208, where a TIM layer 606 is deposited over the first interface metal layer 602. In box 1208, the TIM layer 606 can be deposited over the first interface metal layer 602 in a gel form, a liquid form, or a paste form. In some embodiments, the TIM layer 606 can include a base material and a thermally conductive filler. In some examples, the base material for the TIM layer 606 can include silicone, resin, or epoxy, and the thermally conductive filler for the TIM layer 606 can include beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, a metal (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite. Fig.16As shown in , the TIM layer 606 is deposited over the first interface metal layer 602 above the package component 300 using a dispensing system having a dispensing head 500. Because the first interface metal layer 602 has been deposited to cover the package component 300, the TIM layer 606 is separated from the molding compound 216, the first bottom filler 214, and the tube core by the first interface metal layer 602. At this point, the first interface metal layer 602 is used as an interface layer between the TIM layer 606 and the molding compound 216, the first bottom filler 214 on the one hand, and as an interface layer between the TIM layer 606 and the tube core on the other hand. In some embodiments, the TIM layer 606 can have a thickness between about 50μm and about 150μm. In some instances, due to different deposition methods, the thickness of the TIM layer 606 can be about 50 to about 100 times the thickness of the first interface metal layer 602 or the second interface metal layer 604.

[0043] refer to Fig.13 and Fig.16 , method 1200 includes block 1210, where adhesive 404 is dispensed over packaging substrate 202. As will be described below, method 1200 attaches lid 410 to packaging component 300 and packaging substrate 202. Lid 410 engages packaging component 300 through first interface metal layer 602, TIM layer 606, and second interface metal layer 604, and is attached to the top surface of packaging substrate 202 through adhesive 404. In block 1210, adhesive 404 is selectively deposited over a bonding area on the top surface of packaging substrate 202. When lid 410 is placed over packaging substrate 202, a lower edge of lid 410 will engage adhesive 404 in the bonding area. In some embodiments, selective dispensing of adhesive 404 can be implemented using a dispensing system. The dispensing system includes a dispensing head 450 that dispenses or injects adhesive 404 in gel form, liquid form, or paste form. A stepper of the dispensing system can precisely move dispensing head 450 over first interface metal layer 602. In some embodiments, adhesive 404 may include a die attach film (DAF), silicone, polyimide (PI), or epoxy. Since the primary function of adhesive 404 is bonding, rather than heat dissipation / conduction, adhesive 404 does not include highly thermally conductive materials such as beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, metals (i.e., silver, copper, tin, or indium), diamond, graphene, carbon nanotubes, or graphite.

[0044] refer to Fig.13 and Fig.17 , method 1200 includes block 1212, where a lid 410 is placed over package assembly 300 and package substrate 202. In block 1212, lid 410 including a second interface metal layer 604 on a bottom surface thereof is placed over package assembly 300 and package substrate 202. Fig.17As shown in FIG. 4 , the lower edge of the cover 410 engages the adhesive 404 on the package substrate 202, and the second interface metal layer 604 on the bottom surface is pressed on and engages the TIM layer 606. The cover 410 is attached to the package substrate 202 by the adhesive 404, and is thermally coupled to the package assembly 300 by the first interface metal layer 602, the TIM layer 606, and the second interface metal layer 604. Because the first interface metal layer 602, the TIM layer 606, and the second interface metal layer 604 are all formed of a highly thermally conductive material, the heat generated in the package assembly 300 can be dissipated through the cover 410.

[0045] refer to Fig.13 and Fig.17 , method 1200 includes block 1214, wherein adhesive 404 and / or TIM layer 606 are cured. In some embodiments, adhesive 404 and TIM layer 606 are heat curable. In these embodiments, Fig.17 The WIP structure 200 shown in FIG. 4 may be subjected to an annealing process 10 to cure the adhesive 404 and the TIM layer 606. In some embodiments, the annealing process 10 for curing the adhesive 404 and the TIM layer 606 may include a curing temperature between about 100° C. and about 200° C. and a curing time between about 1 hour and about 2 hours.

[0046] Fig.13 The method 1200 in the embodiment may be modified or combined with the method 1100 or the method 1000 to form Figures 18 to 23 An alternative packaging structure 200 is shown in FIG. Fig.18 and Fig.19 An alternative package structure 200 is shown in which a first interface metal layer 602 is deposited over package component 300 before TIM layer 502 is deposited over package component 300. That is, operations in block 1204 of method 1200 are performed on WIP structure 200 before method 1100 deposits TIM layer 502 in block 1104. Fig.18 The first interface metal layer 602 in the embodiment can be used to further improve the adhesion and stress absorption between the package component 300 and the TIM layer 502. In order to adapt to the concave profile of the TIM layer 502, the first convex cover 412 ( Fig.18 ) or the second convex cover 414 ( Fig.19 ) may be placed over the WIP structure 200 to engage and accommodate the concave profile of the TIM layer 502 .

[0047] Fig. 20 and Fig.21An alternative package structure 200 is shown in which a first interface metal layer 602 is deposited over the package component 300 before the TIM layer 502 is deposited over the package component 300, and a third interface metal layer 608 is deposited over the convex bottom surface of the convex cap. The convex cap may be Fig. 20 The first convex cover 412 or Fig.21 The third interface metal layer 608 can be similar to the second interface metal layer 604 in terms of deposition method and composition, but follows the convex shape of the bottom surface of the convex cap. That is, before the method 1100 deposits the TIM layer 502 in block 1104, the operations in blocks 1204 and 1206 of the method 1200 are performed on the WIP structure 200. Fig. 20 or Fig.21 Either the first interface metal layer 602 or the third interface metal layer 608 can be used to further improve the adhesion and stress absorption between the package component 300 and the TIM layer 502 .

[0048] Fig. 22 Yet another alternative package structure 200 is shown, in which the second interface metal layer 604 is omitted, and the TIM layer 606 is in direct contact with the bottom surface of the lid 410. Although the die in the package assembly 300 may warp and not warp during thermal cycles to cause delamination, the lid 410 does not substantially warp during thermal cycles. In some embodiments, the second interface metal layer 604 is omitted to reduce process steps.

[0049] Fig.23 A further alternative package structure 200 is shown, in which the interface adhesive 402 covering the molding compound 216 and the first underfill 214 is replaced with a fourth interface metal layer 610. Fig.23 In the package structure 200 in block 1004, the interface adhesive 402 is not selectively dispensed over the exposed surfaces of the molding material 216 and the first underfill 214. Instead of omitting the interface adhesive 402, a fourth interface metal layer 610 is selectively deposited over the exposed surfaces of the molding material 216 and the first underfill 214 using PVD and a template that exposes the molding material 216 and the first underfill 214 on the package assembly 300. Like the first interface metal layer 602 and the second interface metal layer 604, the fourth interface metal layer 610 may include a metal or a metal nitride, such as silver, gold, titanium, aluminum, titanium nitride, copper, or tin.

[0050] The present disclosure provides many embodiments. In one aspect, the present disclosure provides a packaging structure. The packaging structure includes: a substrate; a packaging assembly bonded to the substrate and including: a first tube core; a second tube core, which is laterally spaced apart from the first tube core by a bottom filler; and a molding compound, adjacent to the first tube core and the second tube core; a cover, which is disposed above the packaging assembly and the substrate; and an interface structure, which is sandwiched between the packaging assembly and the cover. The interface structure includes: an interface layer, which is disposed above the bottom filler and the molding compound; and a thermal interface material (TIM) layer, which is located above the interface layer, the first tube core, and the second tube core.

[0051] In some embodiments, the interface layer includes a metal layer. In some embodiments, the Young's modulus of the interface layer is less than the Young's modulus of the TIM layer. In some embodiments, the thermal conductivity of the TIM layer is greater than the thermal conductivity of the interface layer. In some embodiments, the interface layer includes a die attach film (DAF), a silicone resin, a polyimide, or an epoxy resin. In some embodiments, the TIM layer includes beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene, or graphite. In some embodiments, the cover includes aluminum (Al), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), an aluminum-copper alloy, an iron-nickel alloy, or an iron-nickel-cobalt alloy. In some instances, the TIM layer is separated from the bottom filler and the molding compound by the interface layer.

[0052] In another aspect, an embodiment of the present disclosure provides a package structure. The package structure includes: a substrate; a package assembly bonded to the substrate and including: a first die; a second die laterally spaced apart from the first die by a bottom filler; and a molding compound adjacent to the first die and the second die; a cover disposed above the package assembly and the substrate; and an interface structure sandwiched between the package assembly and the cover. The cover includes a convex surface that partially extends into the interface structure.

[0053] In some embodiments, the interface structure includes: a first metal layer located above the package component; and a thermal interface material (TIM) layer located above the first metal layer. In some embodiments, the first metal layer is in direct contact with the bottom filler, the molding compound, the first tube core and the second tube core. In some embodiments, the thickness of the TIM layer is between about 50 times and about 100 times the thickness of the first metal layer. In some embodiments, the TIM layer includes beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene or graphite. In some embodiments, the interface structure also includes a second metal layer above the TIM layer, so that the TIM layer is sandwiched between the first metal layer and the second metal layer. In some instances, the second metal layer includes silver (Ag), gold (Au), titanium (Ti), titanium nitride (TiN), copper (Cu) or tin (Sn).

[0054] In yet another aspect, embodiments of the present disclosure provide a method. The method includes: bonding a package assembly to a front side of a substrate, the package assembly including: a first die; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; selectively dispensing an adhesive layer over a top surface of the underfill and the molding compound; depositing a thermal interface material (TIM) over the adhesive layer, the first die, and the second die; after deposition, placing a cover over the package assembly and the substrate; and curing the adhesive layer and the TIM.

[0055] In some embodiments, depositing the TIM includes depositing the TIM directly on the top surface of the first die and the second die. In some embodiments, after depositing the TIM, the TIM is separated from the top surface of the bottom fill and the molding compound by an adhesive layer. In some embodiments, the adhesive layer includes a die attach film (DAF), silicone, polyimide, or epoxy, and the TIM includes beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene, or graphite. In some embodiments, curing includes a curing temperature between about 100° C. and about 200° C. and a curing time between about 1 hour and about 2 hours.

[0056] Some embodiments of the present application provide a package structure, comprising: a substrate; a package assembly bonded to the substrate and comprising: a first die; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; a cover disposed over the package assembly and the substrate; and an interface structure sandwiched between the package assembly and the cover, the interface structure comprising: an interface layer disposed over the underfill and the molding compound; and a thermal interface material (TIM) layer over the interface layer, the first die, and the second die. In some embodiments, the interface layer comprises a metal layer. In some embodiments, the Young's modulus of the interface layer is less than the Young's modulus of the thermal interface material layer. In some embodiments, the thermal conductivity of the thermal interface material layer is greater than the thermal conductivity of the interface layer. In some embodiments, the interface layer comprises a die attach film (DAF), silicone, polyimide, or epoxy. In some embodiments, the thermal interface material layer comprises beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene, or graphite. In some embodiments, the cover comprises aluminum (Al), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), aluminum-copper alloy, iron-nickel alloy, or iron-nickel-cobalt alloy. In some embodiments, the thermal interface material layer is separated from the underfill and the molding compound by the interface layer.

[0057] Some other embodiments of the present application provide a package structure, comprising: a substrate; a package assembly bonded to the substrate and comprising: a first die; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; a cover disposed over the package assembly and the substrate; and an interface structure sandwiched between the package assembly and the cover, wherein the cover comprises a convex surface that partially extends into the interface structure. In some embodiments, the interface structure comprises: a first metal layer over the package assembly; and a thermal interface material (TIM) layer over the first metal layer. In some embodiments, the first metal layer is in direct contact with the underfill, the molding compound, the first die, and the second die. In some embodiments, the thickness of the thermal interface material layer is between about 50 times and about 100 times the thickness of the first metal layer. In some embodiments, the thermal interface material layer comprises beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene, or graphite. In some embodiments, the interface structure further comprises a second metal layer above the thermal interface material layer, so that the thermal interface material layer is sandwiched between the first metal layer and the second metal layer. In some embodiments, the second metal layer comprises silver (Ag), gold (Au), titanium (Ti), titanium nitride (TiN), copper (Cu) or tin (Sn).

[0058] Some other embodiments of the present application provide a method of forming a package structure, comprising: bonding a package assembly to a front side of a substrate, the package assembly comprising: a first die; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; selectively dispensing an adhesive layer over the underfill and the top surface of the molding compound; depositing a thermal interface material (TIM) over the adhesive layer, the first die, and the second die; after the deposition, placing a cover over the package assembly and the substrate; and curing the adhesive layer and the thermal interface material. In some embodiments, depositing the thermal interface material comprises depositing the thermal interface material directly on the top surface of the first die and the second die. In some embodiments, after depositing the thermal interface material, the thermal interface material is spaced apart from the underfill and the top surface of the molding compound by the adhesive layer. In some embodiments, the adhesive layer comprises a die attach film (DAF), silicone, polyimide or epoxy, wherein the thermal interface material comprises beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene or graphite. In some embodiments, the curing comprises a curing temperature between about 100° C. and about 200° C. and a curing time between about 1 hour and about 2 hours.

[0059] The features of several embodiments are summarized above so that those of ordinary skill in the art can better understand the aspects of the embodiments of the present disclosure. Those of ordinary skill in the art should understand that they can easily use the embodiments of the present disclosure as a substrate to design or modify other processes and structures for performing the same purposes and / or achieving the same advantages as the embodiments introduced herein. Those of ordinary skill in the art should also be aware that such equivalent constructions do not depart from the spirit and scope of the embodiments of the present disclosure, and that they can make various changes, substitutions, and modifications herein without departing from the spirit and scope of the embodiments of the present disclosure.

Claims

1. A packaging structure, comprising: substrate; A package assembly is bonded to the substrate and includes: a first tube core; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; a cover disposed over the package assembly and the substrate; and An interface structure, sandwiched between the packaging component and the cover, the interface structure comprising: an interface layer disposed over the bottom filler and the molding compound; and A thermal interface material (TIM) layer is located over the interface layer, the first die, and the second die.

2. The packaging structure according to claim 1, wherein: The interface layer includes a metal layer.

3. The packaging structure according to claim 1, wherein: The Young's modulus of the interface layer is smaller than the Young's modulus of the thermal interface material layer.

4. The packaging structure according to claim 1, wherein: The thermal conductivity of the thermal interface material layer is greater than the thermal conductivity of the interface layer.

5. The packaging structure according to claim 1, wherein: The interface layer includes a die attach film (DAF), silicone, polyimide or epoxy.

6. The packaging structure according to claim 1, wherein: The thermal interface material layer includes beryllium oxide, aluminum oxide, zinc oxide, aluminum nitride, hexagonal boron nitride, copper, aluminum, diamond, graphene or graphite.

7. The packaging structure according to claim 1, wherein: The cover includes aluminum (Al), copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), an aluminum-copper alloy, an iron-nickel alloy, or an iron-nickel-cobalt alloy.

8. The packaging structure according to claim 1, wherein: The thermal interface material layer is separated from the underfill and the molding compound by the interface layer.

9. A packaging structure, comprising: substrate; A package assembly is bonded to the substrate and includes: a first tube core; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; a cover disposed over the package assembly and the substrate; and an interface structure sandwiched between the packaging component and the cover, Wherein, the cover includes a convex surface that partially extends into the interface structure.

10. A method for forming a packaging structure, comprising: A package assembly is bonded to the front side of the substrate, the package assembly comprising: a first tube core; a second die laterally spaced apart from the first die by an underfill; and a molding compound adjacent to the first die and the second die; selectively dispensing an adhesive layer over the underfill and a top surface of the molding compound; depositing a thermal interface material (TIM) over the bonding layer, the first die, and the second die; After said depositing, placing a cover over said package assembly and said substrate; and The adhesive layer and the thermal interface material are cured.

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