U.S. patent application number 10/937454 was filed with the patent office on 2005-06-30 for microwave-absorbing form-in-place paste.
Invention is credited to Johnson, Richard N., Loret, Christophe.
Application Number | 20050139282 10/937454 |
Document ID | / |
Family ID | 34273048 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139282 |
Kind Code |
A1 |
Johnson, Richard N. ; et
al. |
June 30, 2005 |
Microwave-absorbing form-in-place paste
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.
Inventors: |
Johnson, Richard N.;
(Encinitas, CA) ; Loret, Christophe;
(Fontainebleau, FR) |
Correspondence
Address: |
PITNEY HARDIN LLP
7 TIMES SQUARE
NEW YORK
NY
10036-7311
US
|
Family ID: |
34273048 |
Appl. No.: |
10/937454 |
Filed: |
September 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60501488 |
Sep 9, 2003 |
|
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|
Current U.S.
Class: |
141/1 |
Current CPC
Class: |
H01Q 17/00 20130101 |
Class at
Publication: |
141/001 |
International
Class: |
B65B 001/04 |
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 silicide; 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 system; 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.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Description of the Prior Art
[0004] 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.
[0005] 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.
[0006] 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
[0007] 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.
[0008] 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.
[0009] 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 situ in the housing.
[0010] 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.
[0011] 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
[0012] FIG. 1 shows a dispensing system for the microwave-absorbing
material; and
[0013] FIGS. 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
[0014] 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.
[0015] 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.
[0016] 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 silicide; a ferrite (a compound of ferric oxide with another
oxide); PERMALLOY.RTM. (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.
[0017] The microwave-absorbing material is loaded into a dispensing
system, such as one incorporating a syringe-like dispenser, in
tubes. Such a system is shown in FIG. 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.
[0018] 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.
[0019] 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.
[0020] 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 FIGS. 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.
[0021] 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.
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