Patent Application
20150259584
Embodiments of the present disclosure generally relate to the field of integrated circuit package assemblies, and more particularly, to sealants for coupling integrated heat spreaders to package assemblies as well as package assemblies employing the sealants and methods of forming sealants.
As package assemblies become more complicated and incorporate multiple dies in close proximity to one another removing heat from the various elements has become more challenging. As design and complexity of heat spreaders develops to accommodate emerging package arrangements it is becoming necessary to utilize sealants with particular characteristics when mechanically coupling heat spreaders to package assemblies. Traditionally this required reformulation and using different constituents through time consuming and iterative processes to achieve the desired sealant characteristics.
Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.
Embodiments of the present disclosure describe sealants for coupling integrated heat spreaders to integrated circuit (IC) package assemblies. By identifying and controlling the ratio of crosslinker molecules to the chain extending molecules, the properties (in particular elongation and modulus) of the resulting sealant may be easily tuned and adjusted. Thus, using the same base materials in different ratios may result in a number of different sealants having varied characteristics desired for different applications. This may be both faster and less expensive than traditional sealant reformulation and is less likely to result in unwanted changes to other properties.
In the following description, various aspects of the illustrative implementations will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced with only some of the described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the illustrative implementations. However, it will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative implementations.
In the following detailed description, reference is made to the accompanying drawings which form a part hereof, wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.
For the purposes of the present disclosure, the phrase “A and/or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
The description may use perspective-based descriptions such as top/bottom, in/out, over/under, and the like. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of embodiments described herein to any particular orientation.
The description may use the phrases “in an embodiment,” “in embodiments,” or “in some embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous.
The term “coupled with” along with its derivatives, may be used herein. “Coupled” may mean one or more of the following. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term “directly coupled” may mean that two or more elements are in direct contact.
In various embodiments, the phrase “a first feature formed, deposited, or otherwise disposed on a second feature” may mean that the first feature is formed, deposited, or disposed over the second feature, and at least a part of the first feature may be in direct contact (e.g., direct physical and/or electrical contact) or indirect contact (e.g., having one or more other features between the first feature and the second feature) with at least a part of the second feature.
As used herein, the term “module” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a system-on-chip (SoC), a processor (shared, dedicated, or group) and/or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
IHS 110 may be coupled to substrate 102 via a sealant 112. TIM 108 may provide some level of mechanical coupling between IHS 110 and die 106, but sealant 112 is the primary mechanism for mechanically coupling IHS 110 to the package assembly 100. As discussed below different package assemblies and IHS configuration may necessitate sealants with varying characteristics. In particular, both the elongation and the modulus of the sealant are important. The modulus will determine the strength of the mechanical coupling, while the elongation will determine how the sealant will respond in dissipating stress due to thermally induced dimensional changes. As such, different applications may require sealants with different elongation and modulus values. Typically, this would require the use of different sealants or the reformulation of a sealant for a particular application. Embodiments of the present disclosure include sealants in which the elongation and modulus may be tuned based on ratios of precursor chemicals as opposed to using different chemicals or reformulation. Thus minor changes to constituent ratios during sealant formation may provide sealants with different and desirable characteristics.
As will be discussed in more detail below the presence of the vinyl functionality at the end of the polymer resin molecules is important to the tunability of the sealant. The vinyl functional groups may react with silyl hydride groups present in the crosslinker and/or chain extender molecules through platinum-catalyzed hydrosilylation to determine the degree of chain extension and cross linking that may occur.
Modulus and elongation properties may be tuned by varying the ratio of chain extender molecules to crosslinker molecules. Thus, by working with the same base components, but using different ratios thereof, one may create sealants with varying modulus and elongation values. In general the modulus of the sealants may be between 5 and 50 MPa, but other values may be used in some applications. In some embodiments the ratio of silyl hydride functional groups (associated with crosslinker and chain extender molecules) to vinyl functional groups (associated polymer resin) may be from 0.8 and 1.2. In some embodiments the ratio may approximately 1.0. Maintaining the ratio near 1.0 may prevent additional crosslinking from occurring after the sealant has cured. Such post curing crosslinking may cause unstable sealant properties. That said, the ratio may be varied in some instances to control curing kinetics and providing additional silyl hydride functional groups may increase curing speed.
The sealant may also include filler particles. Filler particles may reinforce the sealant and modulate the viscosity, thixotropy, and modulus of the sealant. Filler particles may make up 30% or more of the weight of the sealant. Filler particles may include, but are not limited to, silica, quartz, fumed silica, alumina, silicone, and/or polyester. Filler particles may have average particle diameters from 5-15 μm with maximum particle size less than 100 μm, and preferably less than 50 μm. Fillers having varying particles sizes and shapes may be used. For instance, smaller filler particles will generally increase sealant viscosity whereas larger particles may be used to define minimum bond-line thickness. As discussed below with reference to
When possible surface wetting agents having a boiling point above the curing temperature of the sealant should be utilized. This may decrease the volatility of the sealant, especially in instances where an abundance of surface wetting agents are present. If surface wetting agents have a boiling point below the curing temperature of the sealant it is possible that they may vaporize during curing and generate voids in the cured sealant. This may decrease the reliability of the sealant by reducing the interfacial contact area between the sealant and the components it is coupling to one another.
The sealant may contain additional additives that may make up from 0.1% to 5% of the weight of the sealant. These additional additives may include catalysts, inhibitors, solvents, coloring agents, and other components commonly used in polymer systems to control one or more of bulk properties, reaction mechanics, and final appearance.
At 702 the method 700 may include identifying a ratio of chain extender molecules to crosslinker molecules based at least in part on a desired modulus value or elongation value. The number of silyl hydride functional groups present in the crosslinker molecules may impact this determination. For instance, crosslinker molecules with more silyl hydride groups may lead to a greater degree of crosslinking on a per molecule basis. This operation may include determining a ratio of silyl hydride functional groups associated with crosslinker molecules as compared to silyl hydride functional groups associated with chain extender molecules.
At 704 the method 700 may include combining the chain extender molecules and crosslinker molecules in accordance with the identified ratio with a polymer resin.
At 706 the method 700 may include adding filler particles including at least one of silica, quartz, fumed silica, alumina, silicone, or polyester. The filler particles may be pretreated with other additives, such as surface wetting agents.
At 708 the method 700 may include adding at least one of an adhesion promoter or a surface wetting agent. As mentioned previously, in some embodiments the filler particles may be treated, as with surface wetting agents, such that the surface wetting agents are added to the filler particles before they are incorporated into the sealant. In some embodiments the adhesion promoter or a surface wetting agent may be added to the sealant during sealant formation. The method 700 may also include the addition of other additives including, but not limited to, catalysts, inhibitors, solvents, coloring agents, and other components commonly used in polymer systems to control one or more of bulk properties, reaction mechanics, and final appearance.
Embodiments of the present disclosure may be implemented into a system using any suitable hardware and/or software to configure as desired.
Depending on its applications, computing device 800 may include other components that may or may not be physically and electrically coupled to motherboard 802. These other components may include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, a Geiger counter, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth).
Communication chip 806 may enable wireless communications for the transfer of data to and from computing device 800. The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. Communication chip 806 may implement any of a number of wireless standards or protocols, including but not limited to Institute for Electrical and Electronic Engineers (IEEE) standards including Wi-Fi (IEEE 802.11 family), IEEE 802.16 standards (e.g., IEEE 802.16-2005 Amendment), Long-Term Evolution (LTE) project along with any amendments, updates, and/or revisions (e.g., advanced LTE project, ultra mobile broadband (UMB) project (also referred to as “3GPP2”), etc.). IEEE 802.16 compatible BWA networks are generally referred to as WiMAX networks, an acronym that stands for Worldwide Interoperability for Microwave Access, which is a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards. Communication chip 806 may operate in accordance with a Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. Communication chip 806 may operate in accordance with Enhanced Data for GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN). Communication chip 806 may operate in accordance with Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless Telecommunications (DECT), Evolution-Data Optimized (EV-DO), derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. Communication chip 806 may operate in accordance with other wireless protocols in other embodiments.
Computing device 800 may include a plurality of communication chips 806. For instance, a first communication chip 806 may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth, and a second communication chip 806 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
Processor 804 of computing device 800 may be packaged in an IC assembly (e.g., package assemblies 100 or 200 according to
Communication chip 806 may also include a die that may be packaged in an IC assembly (e.g., package assemblies 100 or 200 according to
In various implementations, computing device 800 may be a laptop, a netbook, a notebook, an ultrabook™, a smartphone, a tablet, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device 800 may be any other electronic device that processes data.
Various operations are described as multiple discrete operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent.
Some non-limiting examples are provided below.
Example 1 includes a sealant for bonding package assembly components, the sealant comprising: at least 5% by weight vinyl-terminated polymer resin; from 0.1% to 5% by weight chain extender molecules including terminal silyl hydride functional groups; and from 0.1% to 5% by weight crosslinker molecules including at least three silyl hydride functional groups.
Example 2 includes the sealant of example 1, wherein the vinyl-terminated polymer resin includes at least one of a vinyl-terminated silicone or a vinyl-terminated silicone-epoxy hybrid.
Example 3 includes the sealant of example 1, further comprising: from 0.1% to 5% by weight surface wetting agent molecules including functional silane groups and having a boiling point above a curing temperature of the sealant.
Example 4 includes the sealant of example 1, further comprising: from 0.1% to 5% by weight adhesion promoting molecules including at least a first functional group to interact with a surface of a substrate or heat spreader, at least a second functional group to interact with the vinyl-terminated polymer resin, and having a boiling point above a curing temperature of the sealant.
Example 5 includes the sealant of example 1, further comprising: at least 30% by weight filler particles including at least one of silica, quartz, fumed silica, alumina, silicone, or polyester.
Example 6 includes the sealant of any of examples 1-5, wherein: the crosslinker molecules include at least one additional functional group to interact with a surface of a substrate or heat spreader.
Example 7 includes the sealant of example 6, wherein: the additional functional group is a silane or epoxide functional group.
Example 8 includes the sealant of any of examples 1-5, wherein: the chain extender molecules include at least one additional functional group to interact with a surface of a substrate or heat spreader.
Example 9 includes the sealant of any of examples 1-5, wherein: the ratio of vinyl functional groups to silyl hydride functional groups is from 0.8 to 1.2.
Example 10 includes a package assembly comprising: a die; an integrated heat spreader thermally coupled to the die; at least one of a mold compound or a substrate; and a sealant to mechanically couple the integrated heat spreader to the at least one of a mold compound or a substrate; wherein the sealant comprises a crosslinked polymer including: at least 5% by weight polymer resin molecules coupled to one another at terminal locations by at least one of chain extender molecules coupled at terminal locations to two polymer resin molecules or crosslinker molecules coupled at non-terminal locations to at least three polymer resin molecules; wherein the chain extender molecules and the crosslinker molecules each form up to 5% by weight of the sealant.
Example 11 includes the package assembly of example 10, wherein the polymer resin includes at least one of a silicone or a silicone-epoxy hybrid.
Example 12 includes the package assembly of example 10, wherein: at least one of the chain extender molecules or the crosslinker molecules include at least one additional functional group to interact with a surface of a substrate or heat spreader.
Example 13 includes the package assembly of example 10, wherein: the ratio of polymer resin molecule terminal locations to polymer resin coupling locations associated with the chain extender molecules and the crosslinking molecules is from 0.8 to 1.2.
Example 14 includes the package assembly of any of examples 10-13, wherein the sealant further comprises at least 30% by weight filler particles including at least one of silica, quartz, fumed silica, alumina, silicone, or polyester.
Example 15 includes the package assembly of any of examples 10-13, wherein the sealant further comprises at least one of an adhesion promoter or a surface wetting agent and the at least one of an adhesion promoter or a surface wetting agent has a boiling point above a curing temperature of the sealant.
Example 16 includes a method of making a sealant for bonding package assembly components, the method comprising: identifying a ratio of chain extender molecules including terminal silyl hydride functional groups to crosslinker molecules including at least three silyl hydride functional groups based at least in part on a desired modulus value or elongation value; and combining the chain extender molecules and crosslinker molecules in accordance with the identified ratio with a vinyl-terminated polymer resin.
Example 17 includes the method of example 16, further comprising: adding filler particles, including at least one of silica, quartz, fumed silica, alumina, silicone, or polyester, to at least one of the chain extender molecules, the crosslinker molecules, or the vinyl-terminated polymer resin.
Example 18 includes the method of example 16, wherein identifying the ratio of chain extender molecules to crosslinker molecules comprises identifying a ratio of silyl hydride functional groups associated with the chain extender molecules to silyl hydride functional groups associated with the crosslinker molecules.
Example 19 includes the method of example 16, further comprising: adding at least one of an adhesion promoter or a surface wetting agent; wherein the least one of an adhesion promoter or a surface wetting agent has a boiling point above a curing temperature of the sealant.
Example 20 includes the method of any of examples 16-19, wherein: the vinyl-terminated polymer resin is from 5% to 25% of the total weight of the sealant.
Example 21 includes the method of any of examples 16-19, wherein: at least one of the crosslinker molecules or the chain extender molecules include at least one additional functional group to interact with a surface of a substrate or heat spreader.
Example 22 includes a computing device comprising: a circuit board; and a package assembly coupled with the circuit board, the package assembly including a die; an integrated heat spreader thermally coupled to the die; at least one of a mold compound or a substrate; and a sealant to mechanically couple the integrated heat spreader to the at least one of a mold compound or a substrate; wherein the sealant comprises a crosslinked polymer including: at least 5% by weight polymer resin molecules coupled to one another at terminal locations by at least one of chain extender molecules coupled at terminal locations to two polymer resin molecules or crosslinker molecules coupled at non-terminal locations to at least three polymer resin molecules; wherein the chain extender molecules and the crosslinker molecules each form up to 5% by weight of the sealant.
Example 23 includes the computing device of example 22, the sealant further comprising at least one of an adhesion promoter or a surface wetting agent and the at least one of an adhesion promoter or a surface wetting agent has a boiling point above a curing temperature of the sealant.
Example 24 includes the computing device of examples 22-23, wherein: the ratio of polymer resin molecule terminal locations to polymer resin coupling locations associated with the chain extender molecules and the crosslinking molecules is from 0.8 to 1.2.
Example 25 includes the computing device of any of examples 22-23, wherein: the computing device is a mobile computing device including one or more of an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, a Geiger counter, an accelerometer, a gyroscope, a speaker, or a camera coupled with the circuit board.
Various embodiments may include any suitable combination of the above-described embodiments including alternative (or) embodiments of embodiments that are described in conjunctive form (and) above (e.g., the “and” may be “and/or”). Furthermore, some embodiments may include one or more articles of manufacture (e.g., non-transitory computer-readable media) having instructions, stored thereon, that when executed result in actions of any of the above-described embodiments. Moreover, some embodiments may include apparatuses or systems having any suitable means for carrying out the various operations of the above-described embodiments.
The above description of illustrated implementations, including what is described in the Abstract, is not intended to be exhaustive or to limit the embodiments of the present disclosure to the precise forms disclosed. While specific implementations and examples are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present disclosure, as those skilled in the relevant art will recognize.
These modifications may be made to embodiments of the present disclosure in light of the above detailed description. The terms used in the following claims should not be construed to limit various embodiments of the present disclosure to the specific implementations disclosed in the specification and the claims. Rather, the scope is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.
