Source: http://www.google.com/patents/US20100187483?dq=6,219,045
Timestamp: 2014-03-14 23:35:23
Document Index: 614825472

Matched Legal Cases: ['Application No. 61', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

Patent US20100187483 - Voltage switchable dielectric composition using binder with enhanced ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA binder for VSD composition is selected to have enhanced electron mobility in presence of high electric fields....http://www.google.com/patents/US20100187483?utm_source=gb-gplus-sharePatent US20100187483 - Voltage switchable dielectric composition using binder with enhanced electron mobility at high electric fieldsAdvanced Patent SearchPublication numberUS20100187483 A1Publication typeApplicationApplication numberUS 12/692,573Publication dateJul 29, 2010Filing dateJan 22, 2010Priority dateJan 23, 2009Also published asCN102361920A, EP2389410A1, WO2010085709A1Publication number12692573, 692573, US 2010/0187483 A1, US 2010/187483 A1, US 20100187483 A1, US 20100187483A1, US 2010187483 A1, US 2010187483A1, US-A1-20100187483, US-A1-2010187483, US2010/0187483A1, US2010/187483A1, US20100187483 A1, US20100187483A1, US2010187483 A1, US2010187483A1InventorsRobert Fleming, Ning Shi, Pragnya SarafOriginal AssigneeRobert Fleming, Ning Shi, Pragnya SarafExport CitationBiBTeX, EndNote, RefManPatent Citations (3), Classifications (18), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetVoltage switchable dielectric composition using binder with enhanced electron mobility at high electric fieldsUS 20100187483 A1Abstract A binder for VSD composition is selected to have enhanced electron mobility in presence of high electric fields.
a binder comprising a polymer material that has a characteristic of being capable of carrying at least 1.0 E-9 amps in presence of a electric field that is equivalent to 400 volts per mil; and one or more types of particles dispersed in the binder; wherein the particles and the binder form the composition to be non-conductive in absence of an electric field that exceeds a threshold value, and conductive in presence of the electric field that exceeds the threshold value. 2. The composition of claim 1, wherein the binder has the characteristic of being capable of carrying at least 2.0 E-09 amps in presence of electric field that is equivalent to 400 volts per mil.
3. The composition of claim 2, wherein the binder comprises polyacrylate.
4. The composition of claim 3, wherein the binder comprises Hexanedioldiacrylate.
5. The composition of claim 1, wherein the binder comprises one or more binders selected from (i) Polyaninlne, (ii) Polybd, or (iii) Hexanedioldiacrylate.
6. The composition of claim 5, wherein the binder further comprises epoxy.
7. The composition of claim 1, wherein a collective concentration level of the particles dispersed in the binder is below a percolation threshold of the binder.
8. The composition of claim 1, wherein the one or more types of particles include a concentration of metal particles.
9. The composition of claim 1, wherein the one or more types of particles include a concentration of semiconductive fillers that are dispersed in the binder in advance of the concentration of metal particles.
10. The composition of claim 1, wherein the concentration of semiconductive fillers include carbon nanotubes.
11. The composition of claim 1, wherein the concentration of semiconductive fillers include antimony in oxide (ATO).
12. The composition of claim 1, wherein the concentration of semiconductive fillers include zinc oxide.
13. A binder for use in a VSD composition, the binder comprising:
polymer material; one or more concentrations of nano-dimensioned semiconductive particles, the one or more concentrations of particles being mixed with the polymer material in advance of conductive particles and other particle constituents that are to comprise the VSD composition; wherein the binder is formulated to conduct at least 1.0 E-09 amps in presence of an electric field that is equivalent to 400 volts per mil. 14. The binder of claim 13, wherein the one or more concentrations of nano-dimensioned semi-conductive particles include carbon nanotubes.
15. The binder of claim 13, wherein the one or more concentrations of nano-dimensioned semi-conductive particles include antimony in oxide (ATO).
16. The binder of claim 13, wherein the one or more concentrations of nano-dimensioned semi-conductive particles include antimony in oxide (ATO) and carbon nanotubes.
17. The binder of claim 13, wherein the polymer material includes Hexanedioldiacrylate.
18. The binder of claim 13, wherein the binder is formulated to conduct at least 1.0 E-06 amps in presence of an electric field that is equivalent to 1000 volts per mil.
19. The binder of claim 13, wherein the one or more concentrations of nano-dimensioned semi-conductive particles include zinc oxide.
20. The binder of claim 13, wherein the one or more concentrations of nano-dimensioned semi-conductive particles include Bismuth Oxide (Bi2O3). Description
RELATED APPLICATIONS This application claims benefit of priority to Provisional U.S. Patent Application No. 61/147,055; the aforementioned priority application being hereby incorporated by reference in its entirety.
This application also claims benefit of priority to U.S. patent application Ser. No. 11/829,946; which claims benefit of priority to Provisional U.S. Patent Application No. 60/820,786; Provisional U.S. Patent Application No. 60/826,746; and Provisional U.S. Patent Application No. 60/949,179; all of the aforementioned priority applications being hereby incorporated by reference.
This application also claims benefit of priority to U.S. patent application Ser. No. 11/829,948; which claims benefit of priority to Provisional U.S. Patent Application No. 60/820,786; Provisional U.S. Patent Application No. 60/826,746; and Provisional U.S. Patent Application No. 60/949,179; all of the aforementioned priority applications being hereby incorporated by reference.
TECHNICAL FIELD Embodiments described herein pertain generally to voltage switchable dielectric (VSD) material, and more specifically to VSD material that uses a binder with enhanced electron mobility at high electric fields.
BACKGROUND Voltage switchable dielectric (VSD) materials are materials that are insulative at low voltages and conductive at higher voltages. These materials are typically composites comprising of conductive, semiconductive, and insulative particles in a polymer matrix. These materials are used for transient protection of electronic devices, most notably electrostatic discharge protection (ESD) and electrical overstress (EOS). Generally, VSD material behaves as a dielectric, unless a characteristic voltage or voltage range is applied, in which case it behaves as a conductor. Various kinds of VSD material exist. Examples of voltage switchable dielectric materials are provided in references such as U.S. Pat. No. 4,977,357, U.S. Pat. No. 5,068,634, U.S. Pat. No. 5,099,380, U.S. Pat. No. 5,142,263, U.S. Pat. No. 5,189,387, U.S. Pat. No. 5,248,517, U.S. Pat. No. 5,807,509, WO 96/02924, and WO 97/26665.
FIG. 2A and FIG. 2B depict conductivity versus electric field for epoxy (Epon) based polymer binders used in compositions of VSD material, as a basis of comparison for binder compositions that enhance electron mobility in presence of high electric fields.
FIG. 3A illustrates the conductivity versus electric field measurements for a HFC polymer, under an embodiment.
FIG. 3B and FIG. 3C depict conductivity versus electric field measurements for suitable alternative polymer materials that exhibit improved electron mobility at high electric fields, according to additional embodiments or variations.
FIG. 4 illustrates conductivity versus electric field measurements for a polymer-based matrix that includes various fillers, according to various embodiments.
DETAILED DESCRIPTION According to various embodiments, a binder for VSD composition is selected to have enhanced electron mobility in presence of high electric fields (such as resulting from an applied voltage measuring hundreds or thousands of volts). In some embodiments, polymer binder material is selected for exhibiting the characteristic of having greater electron mobility when high electric fields are present. As an addition or variation, some embodiments provide that the polymer binder is enhanced with semiconductive fillers to form a binder with improved electron mobility when high electric field is present.
According to embodiments, the binder or matrix for VSD material is formed from polymer material that has the characteristic of exhibiting relatively high electron mobility or conductivity when a high field is present. Such polymer materials are alternatively referenced as high field conductive (�HFC�) polymers. The HFC polymer matrix or binder enable VSD material to be formulated that has improved electrical characteristics, including reduced clamp and trigger voltages, as compared to non-conductive polymers typically used in VSD compositions (e.g. Epon 828).
Additionally, according to some embodiments, a composition of VSD material includes a polymer matrix with fillers that are thoroughly mixed into a polymer resin to form a binder for VSD material. As described with an embodiment of FIG. 4, the presence of fillers enhances the overall electron mobility of the VSD material, so as to reduce clamp and trigger voltages of VSD compositions formed from the binder. Additional particles, such as conductive material (e.g. metal particles) can be added to the binder. The total particle concentration of the resulting VSD material may be below the percolation threshold.
With regard to polymer composition in VSD material, it is believed that when a sufficiently high electric field is present (e.g. one that surpasses a characteristic threshold) an internal field between conductive particles becomes high enough to conduct electrons from one conductive particle through the polymer to the next conductive polymers. As mentioned elsewhere, the internal field for VSD material can be of an order of magnitude or more greater than the applied field to the VSD material, as the result the applied external field is amplified by the conductive particles in the VSD composition. In VSD material, the polymer (or binder) acts as a �semiconductor� with an effective �bandgap�. Embodiments recognize that polymers for use as binder can be selected based on the assumption that if the high field electron mobility of the polymer matrix increases, the characteristic �turn on� voltage would decrease. In other words, if the polymer binder is selected or designed to have high field electron mobility, the corresponding composition of VSD material can be anticipated to have relatively lower trigger and clamp thresholds.
Embodiments further recognize that traditional undoped �conductive polymers� are not necessarily in the category of polymers that can be considered to have high field conductivity. In fact, undoped polymers that, under conventional considerations, are considered to be conductive polymers, do not necessarily conduct under high fields more than other polymers such as epoxy (e.g. Epon). Moreover, conventional conductive polymers typically �conduct� (i.e. have lower resistance than other polymers) at low fields and therefore do not promote a characteristic �off-state� which is requisite for use in the composition of VSD. HFC polymers, on the other hand, are relatively non-conductive at low voltages and are considered �conductive� with application of a relatively high field. It should be appreciated that the term �conductive�, in the context of describing the electrical resistance characteristic of a polymer, is a relative term that is specific to polymers as a class of material. A �conductive polymer� is a non-conductive material, but conductive relative to polymers as a class.
According to an embodiment, an HFC polymer has the following characteristics: such polymer can carry at least one nano-amp of current in presence of a field that is equivalent to or exceeds 400 volts per mil. For reference, some examples are presented with accompanying figures that present current versus field values when voltage is applied across a 2.5 mil gap. While some embodiments described herein incorporate an HFC polymer, other embodiments incorporate polymer material that has enhanced electron mobility at high field. Thus, embodiments recognize that even modest improvements to the binder's high field electron mobility can have benefit to the resulting electrical properties of the VSD material.
Many compositions of VSD material provide desired �voltage switchable� electrical characteristics by dispersing a quantity of conductive materials in a polymer matrix to just below the percolation threshold, where the percolation threshold is defined statistically as the threshold by which a conduction path is likely formed across a thickness of the material. Other materials, such as insulators or semiconductors, are dispersed in the matrix to better control the percolation threshold. Still further, other compositions of VSD material, including some that include particle constituents such as core shell particles or other particles may load the particle constituency above the percolation threshold.
According to embodiments described herein, the matrix binder 105 is formulated from polymer material that has enhanced electron mobility at high electric fields. In some embodiments, the polymer material used for binder 105 includes HFC polymers, such as a polyacrylate (e.g. Hexanedioldiacrylate). As an addition or alternative, the polymer material includes blends or mixtures of polymers (monomers) with high electron mobility with polymers (monomers) with low electron mobility. Such polymers (or blends) with enhanced electron mobility are capable of carrying 1. 0E-9 current at approximately 400 volts per mil (extrapolated from empirical data at 1000 volts and across 2.5 mil gap). According to variations, the polymer binder 105 may also include mixtures of standard polymers (e.g. Epon or GP611) with HFC polymers or polymers with enhanced electron mobility under high field, the polymer binder 105 may be enhanced with use of nano-dimensioned particles 130, which are mixed into the binder to form a doped variant of the binder 105.
The nano-dimensioned particles 130 may be of one or more types. Depending on the implementation, at least one constituent that comprises a portion of the nano-dimensioned particles 130 are (i) organic particles (e.g. carbon nanotubes (CNT), graphenes, C60 fullerenes); or (ii) inorganic particles (metallic, metal oxide, nanorods, or nanowires). The nano-dimensioned particles may have high-aspect ratios (HAR), so as to have aspect ratios that exceed at least 10:1 (and may exceed 1000:1 or more). Specific examples of such particles include copper, nickel, gold, silver, cobalt, zinc oxide, in oxide, silicon carbide, gallium arsenide, aluminum oxide, aluminum nitride, titanium dioxide, antimony, Boron-nitride, antimony in oxide, indium in oxide, indium zinc oxide, bismuth oxide, cerium oxide, and antimony zinc oxide. In at least some embodiments, the nano-dimensioned particles correspond to semiconductive fillers that form part of the binder. Such fillers can be uniformly dispersed in the polymer matrix or binder at various concentrations. As mentioned with an embodiment of FIG. 4, some of the nano-dimensioned particles (e.g. Antimony in oxide (ATO), CNT, zinc oxide, bismuth oxide (Bi2O3)) enhance the electron mobility of the binder 105 at high electric fields.
Polymer Binder with Enhanced High Field Electron Mobility
FIG. 2A through FIG. 4 graphically display experimental results in which conductivity versus electric field for various polymer resins have been measured. The measurements were made for a 2.5 mil gap with 45 mil inner pad diameters. The measurements have been used to identify polymers that exhibit high field electron mobility (e.g. HFC polymers).
With reference to the figures, FIG. 2A and FIG. 2B depict conductivity versus electric field for a standard epoxy (Epon828) based polymer binders, including pure Epon (FIG. 2A) and the mixture of Epon and an epoxidized silicone resin (GP611). In considering the high field electron mobility of the binder, a VSD material designer may be motivated to select the mixture of Epon and GP611) in combination with HFC materials as in FIG. 3A. Thus, FIG. 2B illustrates an improved polymer binder for VSD material, when considering the parameter of electron mobility.
In contrast to FIG. 2A and FIG. 2B, FIG. 3A illustrates the conductivity versus electric field measurements for a HFC polymer. In the example shown, the HFC polymer is a polyacrylate type, and more specifically, Hexanedioldiacrylate (HDDA). As depicted by FIG. 3A, the high field conductivity of the HFC polymer is greater than that of pure Epon, in that HDDA is able to carry current that is measured in the range of approximately 1.5E-09 (at about 400 volts) to 4.0E-09 amps (at about 1000 volts). In contrast, pure Epon carries 5.0E-11 (at about 400 volts) to 1.5E-10 amps (at about 1000 volts).
FIG. 3B and FIG. 3C depict conductivity versus electric field measurements for suitable alternative polymer materials that exhibit improved electron mobility at high electric fields. Surprisingly, in FIG. 3C, Polyaninlne/Epoxy 1:1, is shown to carry current of about 1.8 to 2.0E-10 at 1000 volts, which is much less current than that of HFC polymers such as HDDA Embodiments described herein anticipate that polymers with carbonyl groups, such as hexanedioldiacrylate, have improve high field conductivity.
With regard to the conductivity versus electric field measurements depicted for various polymer materials, it should be noted that in a VSD application, the actual amount of electric field that is present is significantly higher than that provided from an externally applied voltage. As previously mentioned, conductive particles within the VSD composition amplify the externally applied electric field. For example, an electrical event measuring in the neighborhood of 1000 volts may generate an internal electric field within the material that is in the range of tens of thousands of volts.
FIG. 4 illustrates conductivity versus electric field measurements for a polymer-based matrix that includes various fillers. The examples provided use the following nano-dimensioned particles: carbon-nanotubes (CNT), Antimony in oxide (ATO), zinc-oxide (ZnO) and Bismuth Oxide (Bi2O3). In each example, the particles are thoroughly mixed into the polymer resin (e.g. Epon&GP611) in advance of receiving metal particles or other particles and compounds that result in the compound having its switchable electrical characteristic. Results show that the polymer-based matrix has improved electron mobility at high electric fields. The polymer matrix with ATO and CNT shows higher conductivity in contrast to the pure polymer resin and polymer matrix with other semiconductor filler. It is anticipated that the polymer matrix with larger conductivity under high electric field results in reducing the clamp and trigger voltages of the resulting VSD material.
Table 1 lists experimental values for VSD composite that includes various types of polymer binders. Each of the VSD composites listed in Table 1 includes the same general concentrations of conductive and semi-conductive particles (see Table 2 for precise concentrations). The primary variance between each composition is that the polymer-based binder is changed. All depicted voltages are across a 2.5 mil gap.
Gap-PAD
10 ns Clamp
&GP611(3:1)
Standard VSDM
HDDA & PolyBD
HDDA& PolyBD&
GP611(1:1:0.5)
HDDA with
Epon(1:1)
Table 1 shows that the electrical properties of the VSD material changes when different polymer based binders are used. Table 1 illustrates that the VSD compositions generally exhibit lower clamp and trigger voltages in relation to the polymer-based binder having increased electron mobility under high field. The VSD compositions that include the HFC polymer Hexanedioldiacrylate (HDDA) in its binder, such as (i) HDDA with polyBD, (ii) HDDA with EPON, or (iii) HDDA with both polyBD and GP611 show a trigger value of 80-100V (2.5 mil gap) lower than when standard binder systems (EPON &GP611) are used in polymer composites. Hexanedioldiacrylate (HDDA) when combined with other resins and used as a binder for polymer composites also switches faster than the standard binder system for VSD material.
According to one or more embodiments, VSD composition that incorporates HFC polymers (e.g. HDDA) may comprise of 25% metal particle fillers, 25% semiconductor fillers (micron sized or nano sized), optionally may include 1% nanoparticles (e.g. nanorods, nanowires or carbon nanotubes). Broader ranges of the particles may also be used. For example, VSD material may comprise of 10-40% metal particle filler, 10-45% semiconductor particles, and 0.1-15% nanoparticles. In such embodiments, the polymer matrix may correspond to a mixture of hexanedioldiacrylate and epoxy. The measured electrical properties of the sample, such as trigger voltage and clamp voltage are roughly 100-200V lower than the sample materials with pure epoxy as polymer resin. More specific compositions are also provided with Table 2.
The following lists one process for formulating a VSD composition using HDDA polymer mixture (see row 4 of Table 1). In a clean plastic 1000 ml beaker, 4.74 g of shorts graphitized (d>50 nm, l=0.2-1 um) carbon nanotubes (CNTs, manufactured by CHEAP TUBES INC.) are mixed with 65.9 g of epoxy (EPON 828) and 65.9 g of HDDA, added in liquid resin form. Next, 160 g of N-methyl-2-pyrrolidone (is added as the solvent to the above mixture. Then 20.1 g of dicyandiamide and 0.75 g of 1-Methyl imidazole are added as the curing agent and catalyst. The beaker is placed in a cold water bath to control the temperature during premixing. The mixture was mixed to make the solution a uniform mixture of CNTs, resin and solvent. The mixing was further remixed. Then 70.5 g of P25 (TiO2) is weighed out and 2.37 g of KR44 (isopropyl tri (N-ethylenediamino) ethyl titanate) is added to the powder to disperse the particles. The P25 powder is slowly added to the beaker mixture while mixing with the blade simultaneously. Additionally fillers are added: 564.4 g of wet-chemistry processed oxidized Ni, 76.4 g of TiO2, and 127.5 g of bismuth oxide (Bi2O3) are weighed out and then added slowly to the mixture containing the CNTs and the resin. Then 0.66 g of benzoyl peroxide is dissolved in 5 g of NMP and then added to the mixture, so as to initiate the free radical polymerization of HDDA. Next, the mixture was remixed.
Table 2 lists the compositions of each of the VSD compositions identified in Table 1, in greater detail.
GP611 (g)
epon:GP611 (3:1)-
polyBD:HDDA:GP611
HDDA:polyBD (1:1)
HDDA:epon828 (1:1)
catalyst (1-
dicy in
Bi2O3 (g)
Ni 4SP-10 (g)
KR44 (g)
While some variations exist amongst the listed VSD compositions in terms of the concentration of particle constituents, the difference in electrical characteristics of the various compositions (see clamp and trigger voltage values listed in Table 1) is significantly the result of the variation in the polymer constituent(s) of each compositions binder.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS4587140 *Sep 27, 1984May 6, 1986Uniroyal Chemical Company, Inc.Method for embedding electrical and electronic circuitryUS20060111008 *Jan 12, 2006May 25, 2006Arthur David JMethod for patterning carbon nanotube coating and carbon nanotube wiringUS20070126018 *Nov 21, 2006Jun 7, 2007Lex KosowskyLight-emitting device using voltage switchable dielectric material* Cited by examinerClassifications U.S. Classification252/506, 252/520.1, 252/519.5, 252/500, 252/518.1, 252/512, 977/773, 252/511, 977/742International ClassificationH01B1/22, H01B1/24, H01B1/20, H01B1/00Cooperative ClassificationH05K1/0257, H05K1/0373, H05K2201/0738, H05K1/0259European ClassificationH05K1/02C6CLegal EventsDateCodeEventDescriptionNov 20, 2012ASAssignmentOwner name: SHOCKING TECHNOLOGIES, INC., CALIFORNIAEffective date: 20121116Free format text: RELEASE BY SECURED PARTY;ASSIGNOR:SILICON VALLEY BANK;REEL/FRAME:029333/0469Owner name: LITTELFUSE, INC., ILLINOISFree format text: SECURITY AGREEMENT;ASSIGNOR:SHOCKING TECHNOLOGIES, INC.;REEL/FRAME:029340/0806Jul 23, 2010ASAssignmentOwner name: SILICON VALLEY BANK,CALIFORNIAEffective date: 20100721Free format text: SECURITY AGREEMENT;ASSIGNOR:SHOCKING TECHNOLOGIES, INC.;REEL/FRAME:24733/299Owner name: SILICON VALLEY BANK, CALIFORNIAFree format text: SECURITY AGREEMENT;ASSIGNOR:SHOCKING TECHNOLOGIES, INC.;REEL/FRAME:024733/0299Mar 9, 2010ASAssignmentOwner name: SHOCKING TECHNOLOGIES, INC.,CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FLEMING, ROBERT;SHI, NING;SARAF, PRAGNYA;REEL/FRAME:24053/573Effective date: 20100223Owner name: SHOCKING TECHNOLOGIES, INC., CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FLEMING, ROBERT;SHI, NING;SARAF, PRAGNYA;REEL/FRAME:024053/0573RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google