1. Field
Packaging for microelectronic devices.
2. Description of Related Art
Microelectronic packaging technology, including methods to mechanically and electrically attach a silicon die (e.g., a microprocessor) to a substrate or other carrier continues to be refined and improved. Bumpless Build-Up Layer (BBUL) technology is one approach to a packaging architecture. Among its advantages, BBUL eliminates the need for assembly, eliminates prior solder ball interconnections (e.g., flip-chip interconnections), reduces stress on low-k interlayer dielectric of dies due to die-to-substrate coefficient of thermal expansion (CTE mismatch), and reduces package inductance through elimination of core and flip-chip interconnect for improved input/output (I/O) and power delivery performance.
Portable electronics such as mobile phones, personal digital assistance, and digital cameras are becoming more compact while their functionalities increase. The demand for more features in processing power, coupled with a need for smaller integrated circuit package outlines has driven assembly technologies into such electronics. Examples include flip-chip or direct chip attach. Embedded die packages (e.g., BBUL packages) is a packaging technology that provides many advantages over flip-chip or direct chip attach technologies. Such advantages include cost, z-height, improved bump pitch scalability and reduction in x-, y-form factor.
Manufactures and consumers of portable electronic devices desire that the chip or package used in a device contain identification marks such as company logos, pin orientation, manufacturing history such as lot number, time/date traceability, etc., so that a particular chip and/or package can be identified. Traditionally, identification marks are placed on the exterior package with laser marking in wafer form. Miniaturization of devices makes the traditional package disappear and leaves little room for the traditional identification marks.
Die backside films are used in packaging technologies, including packaging technologies related to mobile phones and tablet platforms. These films provide many functionalities such as die crack protection as well as a laser markable surface for unit level identification. To provide quality identification marks on a die backside film, the mark should be readable. This provides the highest comfort level in a manufacturing plant as it can always be verified on a production floor if needed. For identification marks to be readable, a suitable level of contrast is required for both humans and machine vision systems. In die embedded package technologies such as BBUL, a die backside film is used to bond a die to panels prior to substrate build up. After depaneling and separation of a package from a sacrificial core, however, the die backside film surface has been found to no longer be a suitable laser markable surface due principally to the thermal mechanical process operations used during assembly of a BBUL package. As a result, a viable strategy for maintaining unit level identification in BBUL packaging does not exist.
In one embodiment, die 110 is a silicon die or the like having a thickness of approximately 150 micrometers (μm). In another example, die 110 can be a silicon die or the like that has a thickness less than 150 μm such as 50 μm to 150 μm. It is appreciated that other thicknesses for die 110 are possible. In another embodiment, die 110 may be a through silicon via (TSV) die with contacts on a back side of die 110.
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In one embodiment, the filler material includes particles having a mean particle size on the order of 100 nanometers (nm) or less. In another embodiment, a mean particle size of filler material is less than 100 nm. In a further embodiment, a mean particle size of filler material is 50 nm or less. Without wishing to be bound by theory, it is believed that the filler and its particle size effects a modulus of the material and its markability properties, specifically with regard to laser marking In one embodiment, the filler, such as a silica nanometer filler has a mean particle size of 50 nm and is present in an amount of 20 weight percent to 50 weight percent of the total material composition. In another embodiment, the filler is present in an amount of 20 weight percent to 40 weight percent. Again without wishing to be bound by theory, it is believed that the presence of the nanometer silica enhances contrast due to the increased surface area of silica particles relative to, for example, micron size particles thereby significantly increasing scattering in a laser marked region versus an underlying background. As described herein, laser marked contrast refers to the gray value differential achieved by two dimensional (2D) ID reader illumination light scatterings from a mark and no scattering from ambient film surface. In a laser marking process, it is believed that a laser, such as a 2D ID electromagnetic radiation source (e.g., neodymium-doped yttrium aluminum garnet (Nd:YAG) laser) burns the organic material in DBF 160 thereby exposing the filler material. In one embodiment, a marking process is based on thermal laser ablation with an ablation threshold fluence below ablation of the filler material (e.g., silica particles) and above an ablation of the organic polymer. As a result of ablation, the organic polymer is ablated but light scattering filler material (e.g., silica particles) remains integrated in the film. The filler material provides the light contrast.
The presence of the nanometer silica particles also tends to modulate a film etch rate in processing steps such as a wet blast process used to separate a completed package from a sacrificial substrate. The modulation in film etch rate is seen in a greater etch rate selectivity for a die backside film compared to organic layers in an embedded package.
In one embodiment, DBF 160 includes a organic dye with a maximum light absorption or lambda max in the visible wavelength region. Generally, a dye or a pigment is a colorant that is used in DBF 160 to provide laser mark contrast. Examples of organic dyes include an organic dye with reactive functional groups, e.g., amine/epoxy/azo functional groups may also act as a curing accelerator.
In one embodiment, a composition of DBF 160 may also include an adhesion promoter and a solvent.
The following is a representative embodiment of a suitable DBF for BBUL applications including suitable markability (“BBUL DBF”).
The BBUL DBF uses filler particles (silica particles) having a particle size significantly smaller than filler particles in prior art DBF (e.g., 100 nm or 50 nm versus 0.5 μm). The BBUL DBF also uses a higher percentage of dye (7 percent versus 3.5 percent). It has been found that a dye tends to interact with other chemicals during the package build-up process and may also be physically transferred (e.g., physically transferred to a sacrificial substrate on which the package is formed). To account for any loss of -dye due to interaction or transfer of the dye, in one embodiment, a greater weight percentage of dye is used (e.g., a percentage greater than the present in prior art DBF. Representative amounts of dye are 5 percent to 10 percent with the amount of the dye effecting laser markability not contrast. In another embodiment, functional groups such as amine (e.g., —NH2, —NHR) and hydroxyl (—OH) groups can be appended to a dye to make the dye more reactive with other DBF components (e.g., resin, filler, elastomer) to reduce a loss of the dye. In that instance, a lesser amount of dye can be utilized to achieve acceptable markability (e.g., 3.5 percent or less).
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In one embodiment, the structure is separated from sacrificial substrate 210, copper foils 215A and 215B, and copper foils 220A and 220B by a wet blast process. In one embodiment, a wet blast process includes multiple passes of an etchant (e.g., an etchant of one or more of the following: aluminum, titanium, silicon oxides). A first pass may separate copper foils 215A and 215B from copper foils 220A and 220B, respectively, leaving die 240A and die 240B connected to copper foils 215A and 215B, respectively, through DBF 250A and 250B. A second wet blast process pass may then be used to remove copper foils 215A and 215B from DBF films 250A and 250B, respectively. Where a dielectric material is present on the copper foils prior to introduction of DBF 250A and DBF film 250B, a wet blast process may be used to remove the dielectric material from the DBF. Such process may take on the order of 40 to 50 passes to remove a dielectric material like ABF from DBF 250A and DBF 250B. It has surprisingly been found that a DBF film material including nanometer sized filler particles, such as silica particles of 50 nanometers or less, is more resistant to removal by a wet blast process than DBF films including micrometer sized filler particles. Accordingly, a DBF film including nano sized particles has greater selectivity than a DBF film including micrometer sized filler particles relative to a wet blast process.
By removing the individual package portions from sacrificial substrate 210,
Depending on its applications, computing device 500 may include other components that may or may not be physically and electrically coupled to board 502. These other components 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, 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 506 enables wireless communications for the transfer of data to and from computing device 500. 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 506 may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. Computing device 500 may include a plurality of communication chips 506. For instance, a first communication chip 506 may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip 506 may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.
Processor 504 of computing device 500 includes an integrated circuit die packaged within processor 504. In some implementations, the package formed in accordance with embodiment described above utilizes BBUL technology with carrier including a body having a die embedded therein and DBF film of a material including a mark contrast of at least 20 percent and, optionally a DBF that is marked with identification information. The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory.
Communication chip 506 also includes an integrated circuit die packaged within communication chip 506. In accordance with another implementation, package is based on BBUL technology and incorporates a primary core surrounding a TSV or non-TSV integrated circuit die that inhibit package warpage. Such packaging will enable stacking of various devices, including but not limited to, a microprocessor chip (die) with a memory die with a graphics die with a chip set with GPS.
In further implementations, another component housed within computing device 500 may contain a microelectronic package that incorporates a primary BBUL carrier implementation such as described above.
In various implementations, computing device 500 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, computing device 500 may be any other electronic device that processes data.
In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. The particular embodiments described are not provided to limit the claims but to illustrate it. The scope of the claims is not to be determined by the specific examples provided above. In other instances, well-known structures, devices, and operations have been shown in block diagram form or without detail in order to avoid obscuring the understanding of the description. Where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.
It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, “one or more embodiments”, or “different embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.