The present invention relates to the art of interconnecting microelectronic packages and components.
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The applications in microelectronic packaging are more and more focused on the fine pitch capability, low-temperature bonding process, electrical, mechanical, and thermal performance. At the wafer level, low yields due to misalignment is today's biggest engineering quest as the interconnection pitch between driver IC and flex or substrate is significantly decreasing.
Anisotropic conductive films and adhesives, hereinafter “ACFs,” are adhesives currently used to provide a mechanical, electrical and thermal connection between electrical components. Anisotropic conductive films consist of conducting particles in an adhesive resin-type polymer film. One of the limitations of ACF materials is that they do not meet the need for fine pitch capability, low-temperature curing and strong adhesion requirements. Furthermore, since most ACF are made of single size metallized particles, connectivity depends on the contact between a few of the round particles and a flat contact pad.
Another issue with today's AFCs, is that pressure needs to applied to sensitive integrated circuits (IC) chips to contact the underlying metallized pads. Thus, the more pressure is asserted on to the chip the greater the connectivity against the pad. The issue with this is that the yields decrease as many of the sensitive IC's are crushed against the substrate.
Another interconnecting technology at the wafer level is flip chip bumping. In order to increase input/output density of IC's, it also means that interconnect densities must also increase apace. This in turn makes it necessary to shorten pitch geometries from around a 30-micron pitch to as narrow as a 10-micron pitch. Today's conventional mounting technologies like gold bumping cannot form such a fine pitch. Manufacturers are having to resort to multiple rows of bumps at higher pitches as a costly solution, and again low yield becomes an issue.
Bumping the IC given that an effective electrical connection is predicated on a certain area of bump material being in contact with the particular conductive film creates conductivity and bonding issues. Reliability decreases if the width of the bump is reduced to accommodate a finer pitch. Decreasing the gap between adjoining bumps is no answer either, for that can cause new problems such as short-circuiting.
After bumping, alignment is also a big concern for surface mount and flip chips. Pads and bumps are never precisely aligned, and the difference between the artwork and the actual pads, can vary significantly. Lot-to-lot variations are also a major yield issue. Furthermore, misaligned ICs create cracks, connectivity, and related reliability issues.
There is nothing in today's marketplace that incorporates fine pitch capability, a low-temperature bonding process, with high electrical, mechanical, and thermal performance. Furthermore, there is a need in the microelectronic arts to interconnect an IC with a substrate, or heat sink, without the use of pressure. Moreover, in the ACF industry, it would be desirable to progress from mechanically connecting large static conductive particles, to a pressure-less higher conductivity connection without sacrificing high yields.
The foregoing summary, as well as the following detailed description of the technology, will be better understood when read in conjunction with the appended drawings. For illustrating the technology, the figures are shown in the embodiments that are presently preferred. It should be understood, however, that the technology is not limited to the precise arrangements and instrumentalities shown. In the drawings:
The present technology depicts an inventive solution to the fore mentioned issues related to anisotropic conductive films and adhesives.
Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. In some cases, terms with commonly understood meanings are defined herein for clarity and/or for ready reference, and the inclusion of such definitions herein should not necessarily be construed to represent a substantial difference over what is generally understood in the art. Many of the techniques and procedures described, or referenced herein, are well understood and commonly employed using conventional methodology by those skilled in the art. As appropriate, procedures involving the use of commercially available kits and reagents are generally carried out in accordance with manufacturer defined protocols and/or parameters, unless otherwise noted.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, or should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as only one of or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term or as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
“Magnetic nanoparticles” as used herein, and in the claims, shall be interpreted as a class of nanoparticle which can be manipulated using magnetic field. Such particles commonly comprise; Paramagnetic elements such as, Al, Pt, Cr, manganese, crown glass, and Ferromagnetic such as; iron, nickel, and cobalt and a number of their alloys. Furthermore, “nanoparticles” as use herein shall be interpreted as magnetic particles with sizes from a few nanometers up to micrometers. Typically the particles range from 1 nano meter to 10 micron meters in size, and may display superparamagnetism, a size at which materials display different properties to the bulk material. As used herein in the specification and in the claims, there is no strict dividing line between “nanoparticles” and “non-nanoparticles,” material dependent particles are hereby and in the claims also interpreted as particles with much larger in size than 10 micron meters.
Magnetic Anisotropic Conductive Adhesive 105, hereinafter “MACA”, first developed by one of the afore-captioned inventors, is a low temperature, lead free interconnect for flip chip and 3D packaging as seen in
MACA technology enables low cost flip chip assembly by eliminating steps such as patterning of the adhesive, under bump metallization, bumping and flip chip bonding. For 3D packaging such as in
The technology described herein may be used in conjunction, and is not limited to the following electronic packages: ball-grid array type packages mounted on substrate, semiconductor integrated circuit and corresponding package such as dual-in-line (DIP), SMT DIP, BGA, chip-scale package, semiconductor integrated circuit mounted directly on a circuit board (flip-chip) and a semiconductor integrated circuit mounted on one or more integrated circuits of the same or different dimensions, multiple stacked integrated circuits, flat panel display modules for high-resolution, out lead bonding (OLB), flex to printed circuit board bonding (PCB), chip-on-glass (COG), and chip-on-film (COF).
A person skilled in the art may use other types of microelectronic packages or a combination thereof for the same purpose or to achieve similar result. For example, any individual semiconductor device such as an LED die, transistor, diode, or other device mounted in any of the aforementioned constructions. The connection of an electrical assembly such as an LCD, plasma, OLED, LED, or other display and connecting substrate, such as, printed circuit board or ceramic substrates. MACA 105 solves all the aforementioned issues and provides for high mechanical reliability, good electrical performance at high-frequency range and effective thermal conductivity for high current density.
In at least one embodiment of the technology, the MACA 105 material comprise at least one adhesive binder 102 such as an, epoxy, epoxies, polyurethanes, polyimides, polymeric materials, silicone, adhesive, (any combination thereof), and at least one conductive filler
The path of the conductivity is formed using an external magnetic field 201 which causes the particles 602, 603, 604 to orient in regular columns
The technology described herein involves at least one type of filler particle used as the filler material as seen in
In at least one embodiment of the technology, the MACA 105 material may contain at least one magnetic nano-particle of the type disclosed in
As seen in
In another embodiment of the invention, different sized particles are used in combination to achieve a better packing structure of columns 100, and
A person skilled in the art may use other types of Paramagnetic, Ferromagnetic particles or a combination thereof for the same purpose or to achieve similar result. Examples of nano-material particles include Al, Pt, Cr, manganese, crown glass, MgO2, and Ferromagnetic such as; iron, nickel, and cobalt, alloys such as Ni—Fe/SiO2, Co/SiO2, Fe—Co/SiO2, Fe/nickel-ferrite, Ni—Zn-ferrite/SiO2, Fe—Ni/polymer, and Co/polymer magnetic nano-composites, ferrites, and iron oxide.
Nanoparticles as seen in
A first preferred embodiment includes between 10-40 wt % of 3 micron iron particles coated with silver in a polymer binder. The polymer binder is formed from reaction product of between 82% and 91% by weight of a compound and no more than about 6% by weight of a catalyst. The compound includes about 85% by weight of urethane and epoxy acrylates such as those available from Cytec Industries Inc, about 5% by weight of a vinyl monomer such as those available from International Specialty Polymer, and no more than 10% by weight of a UV curable modifier such as the IRGACURE PhotoInitiators available from Ciba Specialty Chemicals. The MACA 105 was applied as a paste dispensed on a coating thickness 100 μm on a ceramic substrate 101 without any pressure and then cured with UV light in a magnetic field 201 of 2000 gauss. This resulted in the self-assembly of conductive columns 100 at regular intervals
A second preferred embodiment includes between 10-40 wt % of 3 micron iron particles coated with silver in a polymer binder. The polymer binder is formed from reaction product of between 82% and 91% by weight of a compound and no more than about 6% by weight of a catalyst. The compound includes about one-third by weight of each of an aromatic epoxy resin, a dimer fatty acid diglycidyl ester and an oxirane. Suitable aromatic epoxy resins include, but are not limited to diglycidyl ethers of bisphenol-A and bisphenol-F and other such resins, such as EPON resins available from Hexion Specialty Chemicals. Solvent Dibasic Ester-1 was used to target a viscosity of 53,000 cP. The MACA 105 was screen printed using a 325 WPI Stainless Steel Mesh, 1.5 mil diameter wire, 0.5 mil emulsion for a coating thickness 100 μm on a PWB substrate 101. It was then heat cured at 60 min at 70° C. or at 1-2 min at 150° C. in a magnetic field 201 of 2500 gauss. This resulted in the self-assembly of conductive columns 100 at regular intervals
A third preferred embodiment includes between 10-20 wt % of 10 nanometer iron particles coated with silver and 10-20 wt % of 100 nanometer iron particles coated with silver in a polymer binder. The polymer binder is formed from reaction product of between 82% and 91% by weight of a compound and no more than about 6% by weight of a catalyst. The compound includes about one-third by weight of each of an aromatic epoxy resin, a dimer fatty acid diglycidyl ester and an oxirane. Suitable aromatic epoxy resins include, but are not limited to diglycidyl ethers of bisphenol-A and bisphenol-F and other such resins, such as EPON resins available from Hexion Specialty Chemicals. Solvent Dibasic Ester-1 was used to target a viscosity of 53,000 cP. The MACA 105 was screen printed using a 325 WPI Stainless Steel Mesh, 1.5 mil diameter wire, 0.5 mil emulsion for a coating thickness 100 μm on a PWB substrate 101. It was then heat cured at 60 min at 70° C. or 1-2 min at 150° C. in a magnetic field 201 of 2500 gauss. This resulted in the self-assembly of conductive columns 100 at regular intervals
The typical properties of cured MACA 105 are:
In another embodiment of the technology, the inventors herein, proved that the electrical and thermal conductivity of the MACA 105 may be improved by coating 801 the particles with a conductive material such as silver, gold, copper, or nickel. Multi-layered particles such as double 801, 802 and triple-layered particles were developed to prevent silver migration and/or prevent surface oxidation. The core 803, was made of Paramagnetic, Ferromagnetic materials, thus creating the bulk driving magnetic force of the particles.
A person skilled in the art may use other types of magnetic nanoparticle shapes or a combination thereof for the same purpose or to achieve similar result. Typical particles claimed herein are spherical
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this technology is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present technology.