Thermally conductive materials for electronic devices

Abstract

A non-conductive film (109) comprising an oligomer containing an arylene repeat unit or a heteroarylene repeat unit is disposed between a chip (105), such as a flip chip, and a functional layer (101), such as a printed circuit board, and is electrically connected to the chip by conductive interconnects (107). The oligomer may be crosslinked.

Description

[Background technology]

[0001] Thermally conductive materials are used in a variety of applications, including in underfills for flip chips, to reduce thermally induced stresses after the flip chip is applied.

[0002] "A novel high thermal conductive underfill for flip chip application" by Mary Liu and Dr. Wusheng Yin, http: / / yincae.com / assets / wp-1000-03 2013.pdf, discloses an underfill containing diamond powder.

[0003] Islam et al., "Enhanced Thermal Conductivity of Liquid Crystalline Epoxy Resin using Controlled Linear Polymerization," ACS Macro Lett. 2018, 7, 10, 1180-1185, discloses liquid crystal epoxy resins with 2-D boron nitride fillers.

[0004] WO 2019 / 143823 discloses thermally conductive quinoid conjugated polymer thin films produced by oxidative chemical vapor deposition. Summary of the Invention

[0005] In some embodiments, an electronic device is provided, comprising: a first chip having a first surface, a functional layer having a surface facing the first surface of the first chip, conductive interconnects between the first chip and the functional layer, and a non-conductive film disposed in a region between the first surface of the first chip and the first surface of the functional layer and in a region between the interconnects, wherein the non-conductive film comprises an oligomer having an arylene repeat unit or a heteroarylene repeat unit.

[0006] Optionally, the oligomer is a rigid rod oligomer.

[0007] Optionally, the oligomer is crosslinked.

[0008] Optionally, the thermal conductivity of the non-conductive film is at least 0.2 Wm -1 K -1 is.

[0009] Optionally, the functional layer is selected from a printed circuit board, an interposer, and a second chip.

[0010] Optionally, the electronic device comprises a 3D chip stack.

[0011] In some embodiments, a method of forming an electronic device as described herein is provided, wherein conductive features on a first surface of a first chip are contacted with conductive features on a first surface of a functional layer, and forming a non-conductive film includes introducing a formulation including oligomers dissolved in one or more solvents into a region between the first chip and the functional layer.

[0012] In some embodiments, a method of forming an electronic device as described herein is provided, the method including forming a non-conductive film over conductive features on a first surface of a first chip, and contacting the conductive features on the first surface of the first chip with conductive features on the first surface of a functional layer.

[0013] Optionally, forming the non-conductive film includes cross-linking the oligomer.

[0014] Optionally, the crosslinking comprises reaction of reactive substituents of the oligomer.

[0015] Optionally, the reactive substituent is a first reactive group X 1 and a second reactive group X 2 Contains X 1 is X 2 can react with to form a covalent bond.

[0016] In some embodiments, a method of forming a film is provided that includes depositing onto a surface a formulation that includes oligomers dissolved or dispersed in one or more solvents, evaporating the one or more solvents, and reacting reactive substituents on the oligomers to form covalent bonds between the oligomer chains.

[0017] Optionally, the reactive substituent is a first reactive group X 1 and a second reactive group X 2 Contains X 1 is X 2 can react with to form a covalent bond. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows a polythiophene oligomer. [Figure 2] FIG. 1 is a schematic diagram showing the bonds between oligomer chains. [Figure 3] 1A-1C are schematic diagrams illustrating electronic devices according to some embodiments that include a flip chip electrically connected to a substrate. [Figure 4A] 4A-4C are schematic diagrams illustrating methods according to some embodiments for forming the electronic device of FIG. 3, in which an underfill layer is formed between the substrate and the flip chip. [Figure 4B] 4A-4C are schematic diagrams illustrating methods according to some embodiments for forming the electronic device of FIG. 3, in which a non-conductive film is applied to the flip chip before bonding to a substrate. [Figure 5] 1A-1D are schematic diagrams illustrating 3D chip stacks according to some embodiments. [Figure 6] FIG. 1 is a diagram schematically illustrating a substrate for measuring the thermal conductivity of a film. [Figure 7A] FIG. 7 is a diagram showing a schematic diagram of an apparatus for measuring thermal conductivity including the substrate of FIG. 6. [Figure 7B] FIG. 7 is a diagram showing a schematic diagram of an apparatus for measuring thermal conductivity including the substrate of FIG. 6.

[0019] The drawings are not drawn to scale and employ various viewpoints and perspectives. The drawings are of several implementations and examples. Furthermore, some components and / or operations may be separated into different blocks or combined into a single block for purposes of illustrating some of the embodiments of the disclosed technology. Moreover, while the technology is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are described in detail below. However, the intention is not to limit the technology to the specific implementations described. On the contrary, the technology is intended to cover all modifications, equivalents, and alternatives falling within the scope of the technology as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0020] Unless the context clearly requires otherwise, throughout the description and claims, words such as "comprises," "including," and the like, should be construed in an inclusive sense, i.e., "including, but not limited to," rather than an exclusive or exhaustive sense. Furthermore, the words "herein," "on," "under," and words of similar meaning, when used in this application, refer to this application as a whole, not to specific portions of this application. Where the context permits, words in the detailed description using the singular or plural can also include the plural or singular, respectively. The word "or" in connection with a list of two or more items extends to all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. As used in this application, a reference to a layer "on" another layer means that the layers may be in direct contact, or that there may be one or more intervening layers. As used in this application, a reference to a layer "on" another layer means that the layers are in direct contact.

[0021] The teachings of the technology provided herein may be applied to other systems, not necessarily the system described below. Elements and acts of the various examples described below may be combined to provide further implementations of the technology. Some alternative implementations of the technology may include fewer elements as well as additional elements to the implementations shown below.

[0022] These and other changes can be made to the technology in light of the following detailed description. While the description describes particular examples of the technology and sets forth the best mode contemplated, no matter how detailed the description may appear, the technology can be practiced in many ways. As noted above, specific terms used when describing particular features or aspects of the technology should not be construed as meaning that the terms are redefined herein to be limited to the particular characteristics, features, or aspects of the technology to which they relate. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless such terms are expressly defined in the Detailed Description section. Thus, the actual scope of the technology encompasses not only the disclosed examples but also all equivalent ways of practicing or implementing the technology according to the claims.

[0023] To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but applicants contemplate various aspects of the technology in any number of claim forms.

[0024] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the disclosed technology. However, it will be apparent to one skilled in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

[0025] The inventors have discovered that high thermal conductivity structures can be formed by solution deposition of rigid-rod oligomers. Optionally, the thermal conductivity of the oligomers as described herein is at least 0.2 Wm -1 K -1 , optionally at least 0.3 Wm -1 K -1 , 0.4Wm -1 K -1 or 0.5Wm -1 K -1 is.

[0026] The oligomers can be substituted with groups to link the oligomer chains together, eg, hydrogen bonds or covalent bonds, to enhance the long-range order of the oligomer.

[0027] Oligomers as described herein are preferably at least partially crystalline.

[0028] Oligomers as described herein preferably comprise arylene or heteroarylene groups which may be unsubstituted or substituted with one or more substituents.

[0029] Oligomers such as those described herein, when deposited as films, can undergo π-π stacking.

[0030] The oligomers as described herein have the formula (I): [ka] wherein Ar 1 is arylene or heteroarylene, n is at least 2, and R in each occurrence 1 is independently H or a substituent, and R in each occurrence 2 are independently H or a substituent, and p is 0 or a positive integer.

[0031] Optionally, n is 2-10.

[0032] Optionally, p is 0, 1, 2, 3, or 4.

[0033] Ar 1 is C 6~20 It can be arylene or 5- to 20-membered heteroarylene.

[0034] Ar 1 can be monocyclic or polycyclic arylene or heteroarylene.

[0035] In some embodiments, each Ar 1 is the same.

[0036] In some embodiments, the oligomer comprises two or more different Ar 1 According to these embodiments, the oligomer preferably contains two different Ar groups. 1 It contains groups (A and B) in an alternating (ABAB...) arrangement.

[0037] Exemplary Ar 1 Groups include, but are not limited to, paraphenylene, thiophene, furan, benzobisoxazole, and combinations thereof. Exemplary oligomers include oligo-p-phenylene, oligothiophene, and oligo-(phenylenebenzobisoxazole).

[0038] Preferably, Ar 1 The groups are joined by aromatic carbon bonds.

[0039] Preferably, the oligomer is a rigid rod oligomer.

[0040] Rigid-rod oligomers as described herein may be formed by combining each Ar of the oligomer as shown in FIG. 1 It may have a structure in which a conceptual line can be drawn through the group.

[0041] Optionally, each bond angle θ between a notional line and each bond of Ar1 to an adjacent repeat unit is 45 degrees or less.

[0042] R 1 Groups and R 2 The number and identity of the groups can be selected according to the desired solubility and / or reactivity of the oligomer.

[0043] Optionally, R 1 teeth, H; F; CN; NO2; One or more non-adjacent C atoms are O, S, or NR 3 , SiR4 2 , C=O or COO [wherein R 3 is H or a substituent, preferably H or C 1~20 R in each occurrence is a hydrocarbyl group. 4 are independently substituents, optionally C 1~20 A branched, linear, or cyclic C may be replaced by a hydrocarbyl group. 1~20 alkyl; an aryl or heteroaryl group Ar that is unsubstituted or substituted with one or more substituents; 3 and a first reactive moiety X 1 and a second reactive moiety X 2 a first reactive moiety X that can react to form a covalent bond 1 and a second reactive moiety X 2 The reactive group is selected from the group consisting of:

[0044] Exemplary Hydrocarbyl Groups R 3 and R 4 As for C 1~20 alkyl; unsubstituted phenyl; and one or more C 1~12 These include, but are not limited to, phenyl substituted with an alkyl group.

[0045] Ar 3 The substituents, if present, are such that one or more non-adjacent C atoms are O, S, NR 3 or SiR 4 2 can be replaced by C 1~20It may be selected from alkyl.

[0046] Optionally, R 2 is selected from the groups described for R1, excluding H.

[0047] R 1 Groups and / or R 2 The groups are R 1 Between groups, R of different oligomer chains 1 Group and R 2 between groups and / or R of different oligomer chains 2 It can be selected to cause bonding between the groups.

[0048] Preferably, the same R 1 groups and / or the same R 2 The group is capable of forming a bond.

[0049] In some embodiments, the oligomer comprises an R group capable of forming hydrogen bonds between the oligomer chains. 1 Groups and / or R 2 group, preferably R 2 Contains a group.

[0050] Groups capable of hydrogen bonding include groups having an NH or OH group, such as groups of the formula -Sp-OH or -Sp-NHR 3 Sp is a flexible spacer group, e.g., an alkylene chain or a phenylene-alkylene chain; R 3 is H or a substituent.

[0051] In some embodiments, the oligomer comprises an R group capable of forming a covalent bond between the oligomer chains. 1 Groups and / or R 2 group, preferably R 2 Contains a group.

[0052] Figure 2 shows the X 1 and X 2 reactive groups X that can react with each other to form covalent bonds 1 and X2 Schematic diagram of an oligomer chain substituted with a substituent containing both X and X of one oligomer chain. 1 The X group of another oligomer chain 2 reacts with one unreacted X 1 group and one unreacted X 2 The base may remain.

[0053] Unresponsive X 1 Groups and X 2 The group X of the further oligomer chain 1 Groups and X 2 groups, thereby producing crosslinked oligomers.

[0054] X on different oligomer chains 1 Groups and X 2 The groups can first hydrogen bond before reacting to form a crosslinked structure.

[0055] In some embodiments, X 1 is a quinone-containing group, and X 2 is a diamine-containing group. The quinone group and the diamine group can react to form an imide, as shown in Scheme 1. [ka]

[0056] A wide range of X groups are available that can react to form covalent bonds, including, but not limited to, groups that undergo elimination, substitution, or cycloaddition reactions. 1 Groups and X 2 It will be understood that groups are known to those skilled in the art.

[0057] Film formation The oligomers of formula (I) described herein are preferably soluble. The oligomers of formula (I) preferably have a solubility in xylene at 50° C. and atmospheric pressure of at least 0.1 mg / mL, optionally at least 0.5 mg / mL, or at least 1 mg / mL.

[0058] The oligomeric film can be deposited from a formulation that includes the oligomer and any other components of the film dissolved or dispersed in one or more solvents.

[0059] Formulations as described anywhere herein may be deposited by any suitable solution deposition technique, including, but not limited to, spin coating, dip coating, drop casting, spray coating, and blade coating.

[0060] The formulation can be deposited onto an alignment layer, for example, a rubbed polyimide.

[0061] Following deposition of the formulation, the formulation can be treated during or after solvent evaporation to promote ordering of the oligomer chains, for example, by stretching or rubbing the film.

[0062] The solvent can be selected according to its ability to dissolve or disperse the oligomer and any other components of the formulation. Examples of solvents include those having one or more substituents, optionally C 1~12 Alkyl, C 1~12 Examples of suitable solvents include, but are not limited to, benzene or naphthalene substituted with one or more substituents selected from alkoxy, F and Cl; ethers; esters; halogenated alkanes; and mixtures thereof. Examples of suitable solvents include, but are not limited to, 1,2,4-trimethylbenzene, mesitylene, 1-methylnaphthalene, 1-chloronaphthalene, diiodomethane, anisole, and 1,2-dimethoxybenzene.

[0063] The membrane may consist of an oligomer or may comprise one or more additional materials, optionally one or more amorphous polymers, for example polystyrene, polyethylene or polypropylene.

[0064] Applicable Films including oligomers as described herein can be used as non-conductive films, such as underfills, for flip chips, including but not limited to 3D stacked multi-chips.

[0065] 3 shows an electronic device comprising a chip 105, a substrate 101, such as a printed circuit board, and conductive interconnects 107 between conductive pads 103 on the surface of the substrate 101 and the chip 105. An underfill 109, including or consisting of an oligomer as described herein, fills the area between the chip 105 and the substrate 101. Optionally, the oligomer is crosslinked.

[0066] 4A , in some embodiments, forming an electronic device includes contacting conductive bumps 107′, such as, for example, solder bumps, with conductive pads 103 disposed on a substrate 101, such as, for example, a printed circuit board, to form interconnects 107 from the conductive bumps 107′. Forming an underfill 109 including an oligomer as described herein includes applying a formulation including the oligomer to the overlap region between the chip 105 and the substrate 101. Optionally, the oligomer is crosslinked after application of the formulation, for example, by heat and / or UV treatment.

[0067] Referring to FIG. 4B, in some embodiments, a film 109 including an oligomer is applied onto the surface of a chip 105 bearing conductive bumps 107′. While FIG. 4B shows complete coverage of the conductive bumps 107′, it should be understood that the conductive bumps 107′ can be partially covered such that portions of the conductive bumps 107′ protrude from the surface of the film 109. The conductive bumps 107′ are then contacted with conductive pads 103 disposed on a substrate 101, such as a printed circuit board, to form conductive interconnects between the substrate and the chip. Formation of the conductive interconnects may include the application of heat and / or pressure.

[0068] If the oligomers of film 109 are cross-linked, the cross-linking can occur before, during, or after conductive bump 107 ′ contacts conductive pad 103 .

[0069] Two or more chips can be bonded with a film including an oligomer as described herein disposed between the chips. Figure 5 shows a 3D stack of chips 105 according to some embodiments, where the chips 105 are sandwiched between an interposer 111 and a non-conductive film 109 disposed between adjacent interposers and the chip surface, and between a substrate 101, e.g., a printed circuit, and the first chip in the 3D stack. At least one non-conductive film 109 includes an oligomer as described herein. Through vias 115 are formed through the chips 105 and the interposer. The 3D stack can include a heat sink 113 disposed on the surface.

[0070] In some embodiments, a film comprising or consisting of an oligomer as described herein can be disposed between an electronic device and a heat sink. [Example]

[0071] Thermal conductivity measurement The sensor substrate 600 (approximately 25 mm x 25 mm) shown in Figure 6 was used for thermal conductivity measurements as described herein. The substrate has a polyethylene naphthalate (PEN) film (Dupont Teonex Q83, 25 μm) with a 200 nm thick heating structure consisting of a 20 micrometer wide heater wire 610 for applying current, a 500 micrometer wide bus bar 620, and contact pads 640. The sensing structure is very similar to the heating structure, except that the heater wire is replaced with a 200 micrometer wide sensor wire 630.

[0072] Referring to Figures 7A and 7B, the sensor substrate 600 carrying the film to be measured is placed on a temperature-controlled aluminum block, regulated by a PID system so that the temperature can be controlled by software. A long notch 720, 1 mm wide and approximately 1 mm deep, is cut into the aluminum block. The sensor substrate 600 is placed on the notch so that the central heater wire 610 is aligned with the center of the notch 720 and the sensor wire 630 is aligned with the edge of the notch. A PMMA sheet 730 (2 mm thick) with a notch cut that matches the notch cut in the aluminum block 710 is placed on top, and an additional piece of PMMA sheet 740 (4 mm thick) without the cut is placed on top to surround the device. The entire assembly is secured using bolts and nuts at position 750. The heater wire is connected to a source meter unit (Keithley 2400) using a four-wire measurement setup. The sensor wires are coupled to a multimeter unit (Keithley2000) using a four-wire setup.

[0073] The temperature of the assembly is first stabilized at a predetermined temperature. The resistance of the heater wire and temperature sensor is then measured. To measure the resistance of the heater wire without causing excessive heating, a low current is applied and the voltage is measured in short pulses, with time between pulses to allow the heat to dissipate. A constant DC current is then applied to the heater wire, causing resistive heating. The placement of the substrate within the assembly causes heat to flow through the substrate and film to an aluminum block, which acts as a heat sink, resulting in a nearly one-dimensional steady-state heat flux. The power dissipated in the heater wire and the resistance of the heater wire and temperature sensor are then further measured. This process is repeated to increase the source current, and the complete process is repeated at the next temperature setpoint.

[0074] The resistances of the heater and sensor wires at different temperature setpoints and with no heat flux are used as calibration data in a linear fit of resistance versus temperature, allowing the temperature of the resistive element to be determined under steady-state heat flux conditions. In this way, the temperature gradient ΔT between the heater wire and the temperature sensor (aligned with the heat sink) can be calculated. The power dissipated in the heater wire is assumed to be completely converted to thermal energy Q. A linear fit is then performed between dT and Q using additional parameters for the length of the heater wire over which power is measured (L, 14.4 mm), the distance between the voltage sensing points, and the gap width (2w, 1 mm). This provides a measure of the conductance C of the device under test, which is affected by losses associated with conductive heat transfer within the board and convective and radiative heat transfer to the environment (h).

[0075] To calculate the thermal conductivity κ, the same measurement process is performed on the substrate without the test film (substrate only). It is assumed that the losses are approximately the same when measuring coated and uncoated substrates. The measured values ​​of the device (C F+S ) to the substrate conductance (C S ) to adjust for these losses. Then, the thermal conductivity (k F ) is the conductance of the obtained film alone, multiplied by the film thickness (d F The film thickness is calculated by measuring the total thickness using a digital micrometer and subtracting the thickness of the substrate. [ka]

[0076] Film formation Paraterphenyl and polystyrene (M.W. 650000) (4:1 w / w) were dissolved in 1-methylnaphthalene at a concentration of 30 mg / mL. Polystyrene was added to the formulation to act as a binder between crystalline domains and promote adhesion to the substrate. The solution was heated to 80 °C to achieve complete dissolution. The hot solution was drop-cast onto a 25-micrometer PEN substrate and left overnight at 50 °C to allow for solvent evaporation and crystal formation. The presence of a crystalline film was confirmed by the use of polarized optical microscopy. The crystalline film was then heated at 120 °C for 30 minutes to remove residual solvent.

[0077] Pure polystyrene: approx. 0.15Wm -1 K -1 In light of this, for a film about 6 to 10 micrometers thick, the -1 K -1 The thermal conductivity of

[0078] Without wishing to be bound by any theory, the rigid-rod oligomers self-assemble into ordered domains after solution deposition, and this long-range order increases the thermal conductivity compared to amorphous films.

[0079] Oligomer Reactions Amino-p-terphenyl and p-terphenyl-carboxaldehyde were reacted by sequentially depositing each component onto a glass substrate from a xylene solution and drying at ambient conditions after each deposition to remove the solvent. The combined component film was then heated to 120 °C on a hotplate. The solid was then removed from the substrate and analyzed by FTIR, which confirmed the presence of imine bonds and the loss of carbonyl and amine functionalities. The product exhibited a new peak at 1620 cm-1, which was not present in any of the FTIR spectra of the starting materials and was attributed to the imine bonds, confirming the occurrence of an imine condensation reaction. A decrease in the intensity of the C=O stretching mode at 1700 cm-1, characteristic of the p-terphenyl-carboxaldehyde starting material, was observed. The N-H stretching mode at 3200-3400 cm-1, characteristic of the amino-p-terphenyl starting material, was absent in the FTIR of the product. These observations indicate that the starting oligomers had reacted to form imine bonds between oligomer chains.

[0080] Crosslinking The reaction between phenanthrenequinone and phenylenediamine, as shown in Scheme 1, was carried out in both solution and solid state. After heating to 120 °C, the formation of the reaction product was confirmed by FTIR and NMR.

[0081] FTIR of the product showed a new peak at 1605 cm-1 attributed to the C=N amide bond. Furthermore, the characteristic N-H stretching peaks at 3000-3200 cm-1 of the phenyldiamine starting material and the C=O stretching peak at 1674 cm-1 of the phenanthrequinone starting material were absent in the FTIR of the product, indicating the occurrence of an imine condensation reaction.

Claims

1. 1. An electronic device comprising: a first chip having a first surface; a functional layer having a surface facing the first surface of the first chip; conductive interconnects between the first chip and the functional layer; and a non-conductive film disposed in a region between the first surface of the first chip and the first surface of the functional layer and in a region between the conductive interconnects, the non-conductive film comprising covalently bonded oligomers, each oligomer comprising an arylene repeat unit or a heteroarylene repeat unit, and imine groups disposed between the oligomers.

2. The electronic device of claim 1 , wherein the oligomer is a rigid-rod oligomer.

3. The electronic device of claim 1 , wherein the oligomer is crosslinked.

4. The non-conductive film has a thermal conductivity of at least 0.2 Wm －１ K －１ The electronic device according to any one of claims 1 to 3, wherein

5. The electronic device according to any one of claims 1 to 4, wherein the functional layer is selected from a printed circuit board, an interposer, and a second chip.

6. The electronic device of any one of claims 1 to 5, wherein the electronic device comprises a 3D chip stack.

7. 7. A method for forming an electronic device according to claim 1, wherein conductive features on the first surface of the first chip are brought into contact with conductive features on the first surface of the functional layer, and forming the non-conductive film comprises introducing a formulation comprising the oligomer dissolved in one or more solvents into the region between the first chip and the functional layer.

8. 7. A method for forming an electronic device according to claim 1, comprising: forming the non-conductive film over conductive features on the first surface of the first chip; and contacting the conductive features on the first surface of the first chip with conductive features on the first surface of the functional layer.

9. The method of claim 7 or 8, wherein the formation of the non-conductive film comprises cross-linking the oligomer.

10. 1. A method of forming a film comprising depositing onto a surface a formulation comprising oligomers dissolved or dispersed in one or more solvents, evaporating the one or more solvents, and reacting reactive substituents of the oligomers to form covalent bonds comprising imine groups between oligomer chains.

11. The reactive substituent is a first reactive group X １ and a second reactive group X ２ Including X １ is X ２ 11. The method of claim 10, wherein the imine group can be reacted with

Images