WO2005023916A2 - Microwave-absorbing form-in-place paste - Google Patents

Microwave-absorbing form-in-place paste Download PDF

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Publication number
WO2005023916A2
WO2005023916A2 PCT/US2004/029726 US2004029726W WO2005023916A2 WO 2005023916 A2 WO2005023916 A2 WO 2005023916A2 US 2004029726 W US2004029726 W US 2004029726W WO 2005023916 A2 WO2005023916 A2 WO 2005023916A2
Authority
WO
WIPO (PCT)
Prior art keywords
resin system
microwave
liquid resin
filler
absorbing material
Prior art date
Application number
PCT/US2004/029726
Other languages
French (fr)
Other versions
WO2005023916A3 (en
Inventor
Richard N. Johnson
Christophe Loret
Original Assignee
Laird Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Laird Technologies, Inc. filed Critical Laird Technologies, Inc.
Priority to CN2004800258450A priority Critical patent/CN1849726B/en
Publication of WO2005023916A2 publication Critical patent/WO2005023916A2/en
Publication of WO2005023916A3 publication Critical patent/WO2005023916A3/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems

Definitions

  • the present invention relates to the electronics industry, and more particularly, to the absorption of undesired radio-frequency (RF) emissions, such as microwave radiation, from electronic equipment, such as computers, telecommunications equipment, and the like.
  • RF radio-frequency
  • the present invention provides an alternative to the pads of the prior art, enabling a housing for electronic equipment to be provided with microwave-absorbing material in a more straightforward and convenient manner.
  • the present invention is a microwave- absorbing material which can be dispensed from standard form-in-place dispensing equipment. Such equipment may include a syringe-like applicator of the variety used to produce form-in-place gaskets and the like.
  • the microwave-absorbing material comprises a liquid resin system and a magnetic or lossy dielectric filler.
  • the liquid resin system is a silicon resin system and the magnetic filler is iron carbonyl powder.
  • the present invention is also a method for absorbing radio-frequency (RF) emissions in electronic equipment.
  • RF radio-frequency
  • the method comprises the steps of providing a liquid resin system; dispersing a magnetic or lossy dielectric filler in the liquid resin system; dispensing the liquid resin system having the filler into a housing for the electronic equipment; and curing the liquid resin system having the filler thereby forming a radio-frequency (RF) absorbing pad in si tu in the housing.
  • RF radio-frequency
  • the microwave-absorbing material that is, the liquid resin system having the filler is self-leveling and may be dispensed into a cavity in the housing. Alternatively, because of its thixotropic properties, the microwave- absorbing material may be dispensed onto a surface in the housing, where it will form a pad when cured.
  • FIG. 1 shows a dispensing system for the microwave- absorbing material
  • Figures 2A and 2B are perspective and side views, respectively, of a dispensing system depositing microwave- absorbing material onto a surface.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Accordingly, the present invention is a microwave- absorbing material which can be dispensed from standard form-in-place dispensing equipment. That is to say, it may be dispensed from a syringe-like applicator of the variety used to produce form-in-place gaskets and the like.
  • the microwave-absorbing material comprises at least two components, the first being a liquid resin system, which may be a silicone resin system. Alternatively, the liquid resin system may be a urethane, epoxy or other organic resin system.
  • the other component is a filler, such as a magnetic or lossy dielectric filler.
  • the magnetic filler is a filler material having a high magnetic permeability and a high electrical resistivity.
  • the magnetic filler material may be iron carbonyl powder.
  • the magnetic filler material may be iron powder; iron suicide; a ferrite (a compound of ferric oxide with another oxide) ; PERMALLOY ® (an alloy containing 78.5% nickel and 21.5% iron and having a high magnetic permeability and electrical resistivity) ; SENDUST (an alloy containing 85% iron, 9.5% silicon and 5.5% aluminum); carbon, that is, conductive carbon powder; fibers, such as graphite or metal fibers; and other fillers with electromagnetic (EM) properties, that is, high magnetic permeability and high electrical resistivity.
  • the microwave-absorbing material is loaded into a dispensing system, such as one incorporating a syringelike dispenser, in tubes.
  • a dispensing system 10 dispenses the microwave- absorbing material 12 into a cavity 14 in a housing for electronic equipment.
  • the microwave- absorbing material 12 self-levels to a desired thickness, thereby forming an RF (radio-frequency) absorbing pad in the cavity 14 when cured.
  • the thickness desired is predetermined to be that required to attenuate surface currents and EMI (electromagnetic interference) within the housing.
  • the microwave-absorbing material 12 of the present invention has a viscosity sufficient to maintain the filler material in a suspended state in the liquid resin system.
  • the amount of filler material used, and the thickness of the microwave-absorbing material 12, deposited in the cavity 14, are controlled to optimize the absorption of microwave energy at a given frequency or frequencies .
  • the microwave-absorbing material 12 of the present invention also has thixotropic properties. Thixotropy is the ability of certain colloidal gels to liquefy when agitated and to return to the gel form when at rest. In other words, gels of this type hold their shape when at rest and not under pressure, but flow freely on application of slight pressure. This property may be exploited to produce a pad of the microwave-absorbing material within a housing without the presence of a cavity.
  • FIGS 2A and 2B are perspective and side views, respectively, of a dispensing system 10 depositing microwave-absorbing material 12 onto a surface 16 in a housing for electronic equipment to form a pad 18 thereof. Because of its thixotropic properties, the microwave-absorbing material 12 maintains its shape as a pad 18 on the surface 16 and cures while keeping that shape . Modifications to the above would be obvious to those of ordinary skill in the art, but would not bring the invention so modified beyond the scope of the appended claims .

Abstract

A microwave-absorbing material which can be dispensed from standard form-in-place dispensing equipment combines a liquid resin system with a magnetic or lossy dielectric filler. In a preferred embodiment, the liquid resin system is a silicone resin system and the magnetic filler is iron carbonyl powder. The microwave-absorbing material is dispensed into a housing for electronic equipment. It may be dispensed into a cavity in the housing where it self-levels and cures. Alternatively, it may be dispensed onto a surface in the housing where, because of its thixotropic properties, it holds its shape and forms a pad of cured microwave-absorbing material thereon.

Description

MICROWAVE-ABSORBING FORM-IN-PLACE PASTE BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to the electronics industry, and more particularly, to the absorption of undesired radio-frequency (RF) emissions, such as microwave radiation, from electronic equipment, such as computers, telecommunications equipment, and the like.
2. Description of the Prior -Art Problems caused by stray electromagnetic (EM) fields and radio frequency (RF) emissions in electronic equipment, such as computers and telecommunications equipment, are well known in the art. A variety of approaches are taken to shield housings for such equipment to reduce the emissions coming from components within the housings, and to prevent emissions originating outside the housings from penetrating inside and interfering with the operation of the components within. Among the approaches is to reduce radio-frequency (RF) emissions, such as microwave radiation, by including radiation-absorbing pads within the housings. Pads of this type have traditionally been cut from large rolls or sheets of the pad material and sized to fit cavities, spaces or areas within the housings. The pads may have a high magnetic permeability and a high electrical resistivity. The present invention provides an alternative to the pads of the prior art, enabling a housing for electronic equipment to be provided with microwave-absorbing material in a more straightforward and convenient manner. SUMMARY OF THE INVENTION Accordingly, the present invention is a microwave- absorbing material which can be dispensed from standard form-in-place dispensing equipment. Such equipment may include a syringe-like applicator of the variety used to produce form-in-place gaskets and the like. The microwave-absorbing material comprises a liquid resin system and a magnetic or lossy dielectric filler. In a preferred embodiment, the liquid resin system is a silicon resin system and the magnetic filler is iron carbonyl powder. The present invention is also a method for absorbing radio-frequency (RF) emissions in electronic equipment. The method comprises the steps of providing a liquid resin system; dispersing a magnetic or lossy dielectric filler in the liquid resin system; dispensing the liquid resin system having the filler into a housing for the electronic equipment; and curing the liquid resin system having the filler thereby forming a radio-frequency (RF) absorbing pad in si tu in the housing. The microwave-absorbing material, that is, the liquid resin system having the filler is self-leveling and may be dispensed into a cavity in the housing. Alternatively, because of its thixotropic properties, the microwave- absorbing material may be dispensed onto a surface in the housing, where it will form a pad when cured. The present invention will now be described in more complete detail, with reference being made to the figures identified hereinbelow. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a dispensing system for the microwave- absorbing material ,- and Figures 2A and 2B are perspective and side views, respectively, of a dispensing system depositing microwave- absorbing material onto a surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Accordingly, the present invention is a microwave- absorbing material which can be dispensed from standard form-in-place dispensing equipment. That is to say, it may be dispensed from a syringe-like applicator of the variety used to produce form-in-place gaskets and the like. The microwave-absorbing material comprises at least two components, the first being a liquid resin system, which may be a silicone resin system. Alternatively, the liquid resin system may be a urethane, epoxy or other organic resin system. The other component is a filler, such as a magnetic or lossy dielectric filler. The magnetic filler is a filler material having a high magnetic permeability and a high electrical resistivity. The magnetic filler material may be iron carbonyl powder. Alternatively, the magnetic filler material may be iron powder; iron suicide; a ferrite (a compound of ferric oxide with another oxide) ; PERMALLOY® (an alloy containing 78.5% nickel and 21.5% iron and having a high magnetic permeability and electrical resistivity) ; SENDUST (an alloy containing 85% iron, 9.5% silicon and 5.5% aluminum); carbon, that is, conductive carbon powder; fibers, such as graphite or metal fibers; and other fillers with electromagnetic (EM) properties, that is, high magnetic permeability and high electrical resistivity. The microwave-absorbing material is loaded into a dispensing system, such as one incorporating a syringelike dispenser, in tubes. Such a system is shown in Figure 1, where a dispensing system 10 dispenses the microwave- absorbing material 12 into a cavity 14 in a housing for electronic equipment. Within the cavity 14, the microwave- absorbing material 12 self-levels to a desired thickness, thereby forming an RF (radio-frequency) absorbing pad in the cavity 14 when cured. The thickness desired is predetermined to be that required to attenuate surface currents and EMI (electromagnetic interference) within the housing. The microwave-absorbing material 12 of the present invention has a viscosity sufficient to maintain the filler material in a suspended state in the liquid resin system. The amount of filler material used, and the thickness of the microwave-absorbing material 12, deposited in the cavity 14, are controlled to optimize the absorption of microwave energy at a given frequency or frequencies . The microwave-absorbing material 12 of the present invention also has thixotropic properties. Thixotropy is the ability of certain colloidal gels to liquefy when agitated and to return to the gel form when at rest. In other words, gels of this type hold their shape when at rest and not under pressure, but flow freely on application of slight pressure. This property may be exploited to produce a pad of the microwave-absorbing material within a housing without the presence of a cavity. Referring to Figures 2A and 2B, which are perspective and side views, respectively, of a dispensing system 10 depositing microwave-absorbing material 12 onto a surface 16 in a housing for electronic equipment to form a pad 18 thereof. Because of its thixotropic properties, the microwave-absorbing material 12 maintains its shape as a pad 18 on the surface 16 and cures while keeping that shape . Modifications to the above would be obvious to those of ordinary skill in the art, but would not bring the invention so modified beyond the scope of the appended claims .

Claims

What Is Claimed Is :
1. A microwave-absorbing material comprising a liquid resin system and a magnetic or lossy dielectric filler.
2. A microwave-absorbing material as claimed in claim 1 wherein said liquid resin system is selected from the group consisting of silicone, urethane and epoxy resin systems .
3. A microwave-absorbing material as claimed in claim 1 wherein said liquid resin system is an organic resin system.
4. A microwave-absorbing material as claimed in claim 1 wherein said magnetic filler is selected from the group consisting of iron carbonyl; iron powder; iron suicide; ferrite; an alloy of nickel and iron; an alloy of iron, silicon and aluminum; carbon; fibers; and other fillers with electromagnetic (EM) properties.
5. A microwave-absorbing material as claimed in claim 1 wherein said liquid resin system is a silicone resin system and said magnetic filler is iron carbonyl powder.
6. A method for absorbing radio-frequency (RF) emissions in electronic equipment, said method comprising the steps of: providing a liquid resin systems- dispensing a magnetic or lossy dielectric filler in said liquid resin system,- dispensing said liquid resin system having said filler into a housing for said electronic equipment; and curing said liquid resin system having said filler thereby forming a radio-frequency (RF) absorbing pad in said housing.
7. A method as claimed in claim 6 wherein said liquid resin system having said filler is self-leveling and is dispensed into a cavity in said housing.
8. A method as claimed in claim 6 wherein said liquid resin system having said filler has thixotropic properties and is dispensed onto a surface in said housing.
PCT/US2004/029726 2003-09-09 2004-09-09 Microwave-absorbing form-in-place paste WO2005023916A2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN2004800258450A CN1849726B (en) 2003-09-09 2004-09-09 Microwave-absorbing form-in-place paste

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US50148803P 2003-09-09 2003-09-09
US60/501,488 2003-09-09

Publications (2)

Publication Number Publication Date
WO2005023916A2 true WO2005023916A2 (en) 2005-03-17
WO2005023916A3 WO2005023916A3 (en) 2005-06-02

Family

ID=34273048

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2004/029726 WO2005023916A2 (en) 2003-09-09 2004-09-09 Microwave-absorbing form-in-place paste

Country Status (4)

Country Link
US (1) US20050139282A1 (en)
CN (1) CN1849726B (en)
TW (1) TWI357425B (en)
WO (1) WO2005023916A2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103183924A (en) * 2011-12-29 2013-07-03 北京有色金属研究总院 Microwave absorption composite material of hollow glass microspheres plated with Al and carbonyl iron powder, and preparation method thereof
RU2791276C2 (en) * 2021-02-15 2023-03-07 ООО "РТ-технологии" Elastomer-absorber of electromagnetic waves

Families Citing this family (8)

* Cited by examiner, † Cited by third party
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CN100363130C (en) * 2005-11-10 2008-01-23 北京科技大学 Method for preparing core-shell structure Fe-PAn by in-situ synthesis process
CN101810886A (en) * 2010-03-17 2010-08-25 清华大学 New application of carbonyl iron powder
CN102304347B (en) * 2011-06-08 2013-08-14 浙江大学 SiC/carbonyl iron nanometer composite material prepared from agricultural wastes through microwave composite and method thereof
CN103658640B (en) * 2013-12-27 2016-08-17 安徽华东光电技术研究所 Preparation, coating and sintering method of iron-silicon-aluminum absorption paste for klystron
CN105331331B (en) * 2014-06-30 2017-03-15 比亚迪股份有限公司 A kind of microwave absorbing material and preparation method thereof
CN104861753B (en) * 2015-05-08 2017-05-31 湖北大学 A kind of bituminous epoxy coating with electromagnetic wave absorption function and preparation method thereof
CN105017948A (en) * 2015-08-05 2015-11-04 普罗旺斯科技（深圳）有限公司 Wave absorbing sheet and manufacturing method thereof
CN111286225A (en) * 2020-02-22 2020-06-16 东莞市鹏威能源科技有限公司 Graphene wave-absorbing film coating and preparation method and application thereof

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DE10115192A1 (en) * 2000-03-29 2001-10-25 Yazaki Corp Electrically conducting paste, useful for electronic machines, contains an electroconductive filler comprising a thermoplastic or thermosetting resin, compounded with copper micro-fibers
US20030044623A1 (en) * 2001-05-07 2003-03-06 Ikuo Sakurai Electromagnetic wave absorber

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US4003840A (en) * 1974-06-05 1977-01-18 Tdk Electronics Company, Limited Microwave absorber
US4538151A (en) * 1982-03-31 1985-08-27 Nippon Electric Co., Ltd. Electro-magnetic wave absorbing material
US5552455A (en) * 1995-08-31 1996-09-03 Lockheed Corporation Radar absorbing material and process for making same
DE19949631A1 (en) * 1998-10-15 2000-05-18 Riken Tokio Tokyo Kk Composite absorber used for electromagnetic waves from electronic products consists of ferrite plates and upper absorbers joined to each other
DE10115192A1 (en) * 2000-03-29 2001-10-25 Yazaki Corp Electrically conducting paste, useful for electronic machines, contains an electroconductive filler comprising a thermoplastic or thermosetting resin, compounded with copper micro-fibers
US20030044623A1 (en) * 2001-05-07 2003-03-06 Ikuo Sakurai Electromagnetic wave absorber

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103183924A (en) * 2011-12-29 2013-07-03 北京有色金属研究总院 Microwave absorption composite material of hollow glass microspheres plated with Al and carbonyl iron powder, and preparation method thereof
RU2791276C2 (en) * 2021-02-15 2023-03-07 ООО "РТ-технологии" Elastomer-absorber of electromagnetic waves

Also Published As

Publication number Publication date
WO2005023916A3 (en) 2005-06-02
CN1849726B (en) 2012-04-04
TW200526716A (en) 2005-08-16
US20050139282A1 (en) 2005-06-30
CN1849726A (en) 2006-10-18
TWI357425B (en) 2012-02-01

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