Patent Application
20170018525
Embodiments pertain to packaging of integrated circuits. Some embodiments relate to solder bonds for packaged integrated circuits.
Electronic devices often include integrated circuits (ICs) that are connected to a subassembly such as a substrate or motherboard. The ICs can be inserted into an IC package to form a first level assembly before it is incorporated into a higher level assembly. The first level assembly can includes first level interconnect (FLI) that provides electronic continuity from contact pads of one or more IC die to contact pads of the IC package.
As electronic system designs become more complex, it is a challenge to meet the desired size constraints of electronic devices. Some manufactures include FLI in IC packages that have a finer pitch than IC die being packaged. As the feature spacing is reduced, the current methods used to attach IC die to IC packages becomes more challenging and includes increased risk. This can result in low yield of the packaging process. Thus, there are general needs for devices, systems and methods that address the spacing challenges for packaging of ICs yet provide a robust and cost effective design.
In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, the various examples discussed in the present document.
A conventional approach to attaching ICs to die packaging includes forming solder balls or bumps on the IC die (Solder on Die or SoD) and then bonding the solder balls to bond pads of a substrate of the IC package. Problems can occur as feature size of the IC package substrate becomes finer to accommodate denser packaging. For instance, multiple IC dice may be included in a single IC package, such as a processor IC and a memory IC. The feature size of FLI between the die may need to be smaller than the feature size of the individual IC die. The mismatch in feature size may lead to bridging between solder bumps.
In the example of
Returning to
Although only one IC die is shown in the examples of
Different approaches can be used to form the solder-wetting protrusions described previously herein. According to some examples, a solder-wetting protrusion can be formed on a bond pad by laser direct deposition of the solder-wetting protrusion onto the bond pad.
In the example shown in
Rapid vaporization at the interface of the transparent material and the solder-wetting material causes the solder-wetting material to be propelled onto a bond pad. Solder flux can be applied to the bond pad of the IC package substrate prior to laser deposition of the solder-wetting protrusion. The addition of solder flux can improve adhesion of the wetting material to the bond pad. The spatial size of the transfer material can be as small as the laser spot size and the spatial size can be of the order of tens of microns. The spatial size can also be determined by the thickness of the transfer material on the film and by the distance of the film from the bond pads. Some advantages of laser direct deposition process in forming the protrusions is that the process is mask-less and has the capability to be implemented using a variety of material. The laser energy can also be used to melt or reflow the material on the package substrate bond pads as well.
The laser energy source can be movable relative to the work piece or the work piece can be moveable relative to the laser energy source. In some examples, the laser energy source 750 is scannable to positions on the film of solder-wetting material 755 opposite the bond pads 725. Pulses of laser energy can be applied to the film of solder-wetting material to transfer the solder-wetting material to the plurality of bond pads. In certain examples, both the laser energy source and the work piece are substantially stationary and the laser energy is scanned over the film of solder-wetting material by controlling a lens or mirror to direct the laser energy to positions on the film to transfer the solder-wetting material. In certain examples, the laser energy is raster scanned (e.g., by a galvo mechanism) over the film at a fast speed. For raster scanning of the laser energy, several thousand points or positions may be scanned per second.
In some examples, the work piece can be moveable relative to the laser energy source. The platform may scan the film of solder-wetting material and the one or more IC package substrates passed the laser energy source. The pulses of laser energy are applied to the film of transparent material to transfer the solder-wetting material onto a bond pad when it is positioned opposite the laser energy source. This approach of moving the work piece relative to the laser energy source is typically slower than the raster scan approach.
Other methods can be used to form the protrusions of solder-wetting material on band pads. According to some examples, a solder-wetting protrusion can be formed on a bond pad of the IC package substrate by laser direct writing of the solder-wetting protrusion onto the bond pad. Direct laser writing or three-dimensional (3D) laser lithography refers to scanning arbitrary 3D structures using photosensitive material. In other examples, a solder-wetting protrusion can include solder paste and the protrusion can be formed on a bond pad by solder paste printing. In certain examples, a solder-wetting protrusion can include a metal, and the protrusion can be plated onto the bond pad, such as by an IC masking and metal deposition process. Other methods of forming the protrusion on the bond pad include wire-stud bonding solder-wetting material to the bonding pad, attaching a solder-wetting micro-ball to the bond pad, attaching a solder-wetting microdot to the bond pad, solder jetting the solder-wetting material onto the bond pad, and injection molding the solder-wetting material onto the bond pad.
An example of an electronic device using semiconductor chip assemblies and solder-wetting protrusion as described in the present disclosure is included to show an example of a higher level device application.
An electronic assembly 810 is coupled to system bus 802. The electronic assembly 810 can include any circuit or combination of circuits. In one embodiment, the electronic assembly 810 includes a processor 812 which can be of any type. As used herein, “processor” means any type of computational circuit, such as but not limited to a microprocessor, a microcontroller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a graphics processor, a digital signal processor (DSP), multiple core processor, or any other type of processor or processing circuit.
Other types of circuits that can be included in electronic assembly 810 are a custom circuit, an application-specific integrated circuit (ASIC), or the like, such as, for example, one or more circuits (such as a communications circuit 814) for use in wireless devices like mobile telephones, personal data assistants, portable computers, two-way radios, and similar electronic systems. The IC can perform any other type of function.
The electronic device 800 can also include an external memory 820, which in turn can include one or more memory elements suitable to the particular application, such as a main memory 822 in the form of random access memory (RAM), one or more hard drives 824, and/or one or more drives that handle removable media 826 such as compact disks (CD), flash memory cards, digital video disk (DVD), and the like.
The electronic device 800 can also include a display device 816, one or more speakers 818, and a keyboard and/or controller 830, which can include a mouse, trackball, touch screen, voice-recognition device, or any other device that permits a system user to input information into and receive information from the electronic device 800.
Demand for smaller electronic device size together with demand for increased device functionality creates challenges for IC packaging. As explained previously, problems can occur as feature size of the IC packages becomes finer to accommodate denser packaging. For instance, the feature size of FLI between the die may need to be smaller than the feature size of the individual IC die. The mismatch in feature size may lead to bridging between solder bumps. Solder-wetting using one or more protrusions of solder-wetting material on bond pads of the IC package substrate may avoid bridging between solder bumps despite the mismatch in feature size.
To better illustrate the methods and apparatuses disclosed herein, a non-limiting list of examples is provided below.
Example 1 can include subject matter (such as a method, means for performing acts, or a machine readable medium that can cause the machine to perform acts) including forming a solder bump on a bond pad of an IC die, forming a solder-wetting protrusion on a bond pad of an IC package substrate, and bonding the solder bump of the IC die to the solder-wetting protrusion of the IC package substrate.
In Example 2, the subject matter of Example 1 optionally includes forming a solder-wetting protrusion on the bond pad of the IC package substrate includes laser direct deposition of the solder-wetting protrusion onto the bond pad of the IC package substrate.
In Example 3, the subject matter of Example 2 optionally includes arranging a film of solder-wetting material opposite the bond pad of the IC package substrate, and applying laser energy to the film of solder-wetting material to transfer the solder-wetting material to the bond pad of the IC package substrate.
In Example 4, the subject matter of example 2 optionally includes arranging, opposite the bond pad of the IC package substrate, a film having the solder-wetting material on one side and a transparent material on the other side, and applying laser energy to the transparent side of the film.
In Example 5, the subject matter of one or any combination of Examples 3 and 4 optionally includes arranging the film of solder-wetting material opposite a plurality of bond pads of one or more IC package substrates, and scanning a laser energy source to positions on the film of solder-wetting material opposite the plurality of bond pads and applying pulses of laser energy to the film of solder-wetting material to transfer the solder-wetting material to the plurality of bond pads.
In Example 6, the subject matter of one or any combination of Examples 3 and 4 optionally includes arranging the film of solder-wetting material opposite a plurality of bond pads of one or more IC package substrates, and scanning the plurality of bonds passed the laser energy source and applying a pulses of laser energy to the film of transparent material to transfer the solder-wetting material onto a bond pad when it is positioned opposite the laser energy source.
In Example 7, the subject matter of one or any combination of Examples 2-6 optionally includes applying solder flux to the bond pad of the IC package substrate prior to laser deposition of the solder-wetting protrusion.
In Example 8, the subject matter of one or any combination of Examples 1-7 optionally includes laser direct writing of the solder-wetting protrusion onto the bond pad of the IC package substrate.
In Example 9, the subject matter of one or any combination of Examples 1-8 optionally includes at least one of wire-stud bonding solder-wetting material to the bonding pad, attaching a solder-wetting micro-ball to the bond pad, attaching a solder-wetting microdot to the bond pad, solder jetting the solder-wetting material onto the bond pad, or injection molding the solder-wetting material onto the bond pad.
In Example 10, the subject matter of one or any combination of Examples 1-9 optionally includes at least one of solder paste printing the solder-wetting protrusion on the bond pad or plating the solder-wetting protrusion on the bond pad.
In Example 11, the subject matter of one or any combination of Examples 1-10 optionally includes heating the solder bump to form a molten solder bump and contacting the molten solder bump with the solder-wetting protrusion.
In Example 12, the subject matter of one or any combination of Examples 1-11 optionally includes heating the solder bump to form a molten solder bump and pressing the molten solder bump of the IC die to the solder-wetting protrusion of the IC package substrate.
Example 13 can include subject matter, or can optionally be combined with one or any combination of Examples 1-12 to include subject matter (such as an apparatus), including means for forming a solder bump on a bond pad of an integrated circuit (IC) die, means for forming a solder-wetting protrusion on a bond pad of an IC package substrate, and means for bonding the solder bump of the IC die to the solder-wetting protrusion of the IC package substrate.
In Example 14, the means for forming a solder-wetting protrusion on the bond pad of Example 13 optionally includes an automatic laser direct deposition station.
In Example 15, the subject matter of Example 14 optionally includes a film of solder-wetting material on a transparent substrate and arranged opposite the bond pad of the IC package substrate, and a laser energy source to apply laser energy to the transparent substrate to transfer the solder-wetting material onto the bond pad of the IC package substrate.
In Example 16, the subject matter of one or any combination of Examples 14-15 optionally includes a film of solder-wetting material arranged opposite a plurality of bond pads of one or more IC package substrates, and the applied laser energy is optionally scannable to positions on the film of transfer material opposite the plurality of bond pads.
In Example 17, the subject matter of one or any combination of Examples 14-15 optionally includes film of solder-wetting material is arranged opposite a plurality of bond pads of one or more IC package substrates, wherein the film of solder-wetting material and the one or more IC package substrates are movable relative to the laser energy source to position a bond pad and solder-wetting material opposite the applied laser energy.
In Example 18, the means for bonding the solder bump of the IC die to the solder-wetting protrusion of the IC package substrate of any one of Examples 13-17 optionally includes an automatic thermal compressive bonding (TCB) station configured to bond the IC die to the IC package substrate.
Example 19 can include subject matter, or can optionally be combined with one or any combination of Examples 1-18 to include subject matter (such as an electronic assembly including an integrated circuit (IC) package substrate, a number of bond pads on the IC package substrate, wherein a bond pad includes a surface for electrical connection to an IC die, and one or more protrusions of solder-wetting material extending away from the surface of one or more of the number of bond pads.
In Example 20 the subject matter of Example 19 can optionally include a solder-wetting protrusion that includes a base and an apex, wherein a width of the base is greater than a width of the apex.
In Example 21, the subject matter of claim 20 can optionally include a solder-wetting protrusion having a base width of one hundred micrometers (100 microns) or less.
In Example 22, the subject matter of one or any combination of Examples 19-21 optionally includes a solder-wetting protrusion having a width less than a width of the surface of the bond pad of the IC package substrate.
In Example 23, the subject matter of one or any combination of Examples 19-22 optionally includes a solder-wetting protrusion that includes at least one of tungsten, gold, copper, or silver.
In Example 24, the subject matter of one or any combination of Examples 19-23 optionally includes a solder-wetting protrusion that includes solder paste.
In Example 25, the subject matter of one or any combination of Examples 19-23 optionally includes the IC die bonded to the IC package substrate, wherein the IC die includes at least one of a processor and a memory.
Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples.
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the disclosure can be practiced. These embodiments are also referred to herein as “examples.” In the event of inconsistent usages between this document and any documents incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code can form portions of computer program products. Further, the code can be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAM's), read only memories (ROM's), and the like. In some examples, a carrier medium can carry code implementing the methods. The term “carrier medium” can be used to represent carrier waves on which code is transmitted.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/032136 | 3/28/2014 | WO | 00 |
