U.S. patent application number 16/623939 was filed with the patent office on 2020-12-31 for electromagnetic interference shielding film, circuit board, and preparation method for electromagnetic interference shielding film.
The applicant listed for this patent is GUANGZHOU FANG BANG ELECTRONIC CO., LTD.. Invention is credited to Zhi Su.
Application Number | 20200413577 16/623939 |
Document ID | / |
Family ID | 1000005272745 |
Filed Date | 2020-12-31 |
United States Patent
Application |
20200413577 |
Kind Code |
A1 |
Su; Zhi |
December 31, 2020 |
ELECTROMAGNETIC INTERFERENCE SHIELDING FILM, CIRCUIT BOARD, AND
PREPARATION METHOD FOR ELECTROMAGNETIC INTERFERENCE SHIELDING
FILM
Abstract
Disclosed are an Electromagnetic Interference shielding film, a
circuit board and a preparation method of the electromagnetic
Interference shielding film. The electromagnetic Interference
shielding film includes: a first shielding layer, a second
shielding layer, an adhesive film and multiple convex particles,
wherein the first shielding layer includes a first surface and a
second surface opposite to each other; the second surface is a flat
surface; the multiple convex particles are adhered on the second
surface of the first shielding layer; the second shielding layer is
disposed on the second surface of the first shielding layer and
covers the multiple convex particles, thereby forming a protrusion
portion at a position corresponding to the convex particles on an
outer surface of the second shielding layer and forming a gentle
portion at other positions; and the adhesive film is disposed on
the outer surface of the second shielding layer.
Inventors: |
Su; Zhi; (Guangzhou,
Guangdong, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GUANGZHOU FANG BANG ELECTRONIC CO., LTD. |
Guangzhou, Guangdong |
|
CN |
|
|
Family ID: |
1000005272745 |
Appl. No.: |
16/623939 |
Filed: |
March 22, 2018 |
PCT Filed: |
March 22, 2018 |
PCT NO: |
PCT/CN2018/080019 |
371 Date: |
December 18, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K 9/0084 20130101;
H05K 1/0216 20130101; B32B 2307/212 20130101; B32B 3/085 20130101;
B32B 2457/08 20130101; H05K 9/0088 20130101; H05K 9/0083
20130101 |
International
Class: |
H05K 9/00 20060101
H05K009/00; B32B 3/08 20060101 B32B003/08; H05K 1/02 20060101
H05K001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2018 |
CN |
201810210836.2 |
Claims
1. An Electromagnetic Interference shielding film, comprising a
first shielding layer, a second shielding layer, an adhesive film
layer and multiple convex particles, wherein the first shielding
layer comprises a first surface and a second surface opposite to
each other; the second surface is a flat surface; the multiple
convex particles are adhered on the second surface of the first
shielding layer, the second shielding layer is disposed on the
second surface of the first shielding layer and covers the multiple
convex particles, thereby forming a protrusion portion at a
position corresponding to the convex particles on an outer surface
of the second shielding layer and forming a gentle portion at other
positions; and the adhesive film layer is disposed on the outer
surface of the second shielding layer.
2. The electromagnetic Interference shielding film as claimed in
claim 1, wherein the convex particles comprise one or more of
conductor particles, semiconductor particles, insulator particles
and coated compound particles.
3. The electromagnetic Interference shielding film as claimed in
claim 1, wherein the height of the convex particles is within a
range of 0.1 .mu.m to 30 .mu.m.
4. The electromagnetic Interference shielding film as claimed in
claim 1, wherein multiple conductive protrusions are further formed
on the outer surface of the second shielding layer.
5. The electromagnetic Interference shielding film as claimed in
claim 4, wherein the conductive protrusions are intensively
distributed on the protrusion portion.
6. The electromagnetic Interference shielding film as claimed in
claim 1, wherein the adhesive film layer comprises an adhesion
layer containing conductive particles.
7. The electromagnetic Interference shielding film as claimed in
claim 1, wherein the adhesive film layer comprises an adhesion
layer not containing conductive particles.
8. The electromagnetic Interference shielding film as claimed in
claim 1, wherein both the first shielding layer and the second
shielding layer comprise one or more of a metal shielding layer, a
carbon nano tube shielding layer, a ferrite shielding layer or a
graphene shielding layer.
9. The electromagnetic Interference shielding film as claimed in
claim 8, wherein the metal shielding layer comprises a single metal
shielding layer and/or an alloy shielding layer; the single metal
shielding layer is made of any one of aluminum, titanium, zinc,
iron, nickel, chromium, cobalt, copper, silver or gold, and the
alloy shielding layer is made of any two or more of aluminum,
titanium, zinc, iron, nickel, chromium, cobalt, copper, silver or
gold.
10. The electromagnetic Interference shielding film as claimed in
claim 1, wherein the electromagnetic Interference shielding film
further comprises a protective film layer, the protective film
layer being formed on the first surface of the shielding layer.
11. A circuit board, comprising a printed circuit board and the
Electromagnetic Interference shielding film according to claim 1,
wherein the electromagnetic Interference shielding film is
laminated with the printed circuit board through an adhesive film
layer; and a protrusion portion punctures the adhesive film layer
and extends to a ground layer of the printed circuit board.
12. A preparation method for an Electromagnetic Interference
shielding film, applied to preparing the electromagnetic
Interference shielding film according to claim 1 and comprising the
following steps: S1. forming first shielding layer, wherein the
first shielding layer includes a first surface and a second surface
opposite to each other, and the second surface is a flat surface;
S2. forming multiple convex particles on the second surface of the
first shielding layer, S3. forming a second shielding layer on the
second surface having the convex particles, wherein a protrusion
portion is formed at a position corresponding to the convex
particles on an outer surface of the second shielding layer, and a
gentle portion is formed at other positions; and S4. forming an
adhesive film layer on the outer surface of the second shielding
layer.
13. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, wherein the first shielding
layer is formed in the step S1 by means of the following manners:
forming a protective film layer on a carrier film, and forming the
first shielding layer on the protective film layer, wherein the
first surface is laminated with the protective film layer, or
forming a peelable layer on a carrier film, forming the first
shielding layer on a surface of the peelable layer, and after the
projective film layer is formed on the first surface of the first
shielding layer, peeling the carrier film layer.
14. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, before forming an adhesive
film layer on the outer surface of the second shielding layer,
further comprising: forming multiple conductive protrusions on the
outer surface of the second shielding layer via one or more
processes of physical roughening, chemical plating, physical vapor
deposition, chemical vapor deposition, evaporation plating,
splutter plating, electroplating or mixed plating.
15. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, wherein the forming an
adhesive film layer on the outer surface of the second shielding
layer in step S4 specifically comprises: coating the adhesive film
layer on a release film, and then laminating and transferring the
adhesive film layer to the outer surface of the second shielding
layer so as to form the adhesive film layer on the outer surface of
the second shielding layer, or, directly coating the adhesive film
layer on the outer surface of the second shielding layer so as to
form the adhesive film layer on the outer surface of the second
shielding layer.
16. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 13, before forming an adhesive
film on the outer surface of the second shielding layer, the
preparation method further comprising: forming multiple conductive
protrusions on the outer surface of the second shielding layer via
one or more processes of physical roughening, chemical plating,
physical vapor deposition, chemical vapor deposition, evaporation
plating, splutter plating, electroplating or mixed plating.
17. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, wherein the convex particles
comprise one or more of conductor particles, semiconductor
particles, insulator particles and coated compound particles.
18. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, wherein the height of the
convex particles is within a range of 0.1 .mu.m to 30 .mu.m.
19. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 12, wherein multiple conductive
protrusions are further formed on the outer surface of the second
shielding layer.
20. The preparation method for the electromagnetic Interference
shielding film as claimed in claim 19, wherein the conductive
protrusions are intensively distributed on the protrusion portion.
Description
TECHNICAL FIELD
[0001] The disclosure relates to the field of electronics, and more
particularly to an Electromagnetic Interference shielding film, a
circuit board, and a preparation method for an electromagnetic
Interference shielding film.
BACKGROUND
[0002] With the rapid development of an electronic industry,
electronic products further develop to small size, light weight and
high assembly density, and greatly promote the development of
flexible circuit boards, thereby achieving integration of element
device and wire connection. The flexible circuit boards may be
widely applied to industries such as mobile phones, liquid crystal
displays, communications and aerospace.
[0003] Under the promotion of an international market, a functional
flexible circuit board plays a dominant role in a flexible circuit
board market. An important indicator for evaluating the functional
flexible circuit board is electromagnetic Interference (EMI)
shielding. With the integration of functions of communication
equipment such as a mobile phone, internal components thereof are
subjected to sharp high frequency and high speed. For example, the
mobile phone has a necessary function namely a photography function
in addition to an original audio propagation function, a Wireless
Local Area Networks (WLAN) function, a Global Positioning System
(GPS) function and a networking function have been popularized, and
it will inevitably tend to sharp high-frequency and high-speed
components in conjunction with the future integration of sensing
components. The problems of EMI inside and outside a component,
signal transmission attenuation, insertion loss and jitter caused
by high-frequency and high-speed drive are gradually severe.
[0004] At present, a shielding film commonly used for an existing
circuit board includes a shielding layer and a conductive adhesive
layer. The conductive adhesive layer is connected to a ground layer
of the circuit board by means of the shielding layer, thus guiding
an interference charge to the ground layer of the circuit board and
implementing the shielding. However, during high-frequency
transmission, a conductive particle in the conductive adhesive
layer has an eddy-current loss, so that the insertion loss of the
circuit board is increased to affect the integrity of a signal in
transmission.
SUMMARY
[0005] An objective of the embodiments of the disclosure is to
provide an Electromagnetic Interference (EMI) shielding film, a
circuit board, and a preparation method for an EMI shielding film,
which can reduce the insertion loss and is effectively applied to
ultrahigh frequency transmission.
[0006] To achieve the above-mentioned objective, the embodiments of
the disclosure provide an EMI shielding film, including a first
shielding layer, a second shielding layer, an adhesive film layer
and multiple convex particles, wherein the first shielding layer
includes a first surface and a second surface opposite to each
other, the second surface is a flat surface; the multiple convex
particles are adhered on the second surface of the first shielding
layer, the second shielding layer is disposed on the second surface
of the first shielding layer and covers the multiple convex
particles, thereby forming a protrusion portion at a position
corresponding to the convex particles on an outer surface of the
second shielding layer and forming a gentle portion at other
positions; and the adhesive film layer is disposed on the outer
surface of the second shielding layer.
[0007] As an improvement of the above-mentioned solution, the
convex particles include one or more of conductor particles,
semiconductor particles, insulator particles and coated compound
particles.
[0008] As an improvement of the above-mentioned solution, the
height of the convex particles is within a range of 0.1 .mu.m to 30
.mu.m.
[0009] As an improvement of the above-mentioned solution, multiple
conductive protrusions are further formed on the outer surface of
the second shielding layer.
[0010] As an improvement of the above-mentioned solution, the
conductive protrusions are intensively distributed on the
protrusion portion.
[0011] As an improvement of the above-mentioned solution, the
adhesive film layer includes an adhesion layer containing
conductive particles.
[0012] As an improvement of the above-mentioned solution, the
adhesive film layer includes an adhesion layer not containing
conductive particles.
[0013] As an improvement of the above-mentioned solution, both the
first shielding layer and the second shielding layer include one or
more of a metal shielding layer, a carbon nano tube shielding
layer, a ferrite shielding layer or a graphene shielding layer.
[0014] As an improvement of the above-mentioned solution, the metal
shielding layer includes a single metal shielding layer and/or an
alloy shielding layer, wherein the single metal shielding layer is
made of any one of aluminum, titanium, zinc, iron, nickel,
chromium, cobalt, copper, silver or gold, and the alloy shielding
layer is made of any two or more of aluminum, titanium, zinc, iron,
nickel, chromium, cobalt, copper, silver or gold.
[0015] As an improvement of the above-mentioned solution, the EMI
shielding film further includes a protective film layer, the
protective film layer being formed on the first surface of the
shielding layer.
[0016] Compared with the related art, according to the EMI
shielding film disclosed by the embodiments of the disclosure, a
protrusion portion is formed at a position corresponding to convex
particles on an outer surface of a second shielding layer and a
gentle portion is formed at other portions, and an adhesive film
layer is disposed on the outer surface of the second shielding
layer, so the protrusion portion guarantees that the shielding
layers smoothly puncture the adhesive film layer in a lamination
process, and an interference charge is guided out normally;
meanwhile, the gentle portion also can reduce the insertion loss in
use; and therefore, the EMI shielding film is applied to ultrahigh
frequency transmission.
[0017] The embodiments of the disclosure also provide a circuit
board. The circuit board includes a printed circuit board and the
EMI shielding film according to any one of the above-mentioned
contents, wherein the EMI shielding film is laminated with the
printed circuit board through an adhesive film layer; and a
protrusion portion punctures the adhesive film layer and extends to
a ground layer of the printed circuit board.
[0018] Compared with the related art, according to the circuit
board provided by the embodiments of the disclosure, the circuit
board includes a printed circuit board and the EMI shielding film
according to any one of the above-mentioned contents, wherein the
EMI shielding film is laminated with the printed circuit board
through an adhesive film layer, and a protrusion portion punctures
the adhesive film layer and extends to a ground layer of the
printed circuit board to guide an interference charge out smoothly;
meanwhile, a gentle portion also can reduce the insertion loss in
use; and therefore, the circuit board is applied to ultrahigh
frequency transmission.
[0019] The embodiments of the disclosure also correspondingly
provide a preparation method for an EMI shielding film, which is
applied to preparing the EMI shielding film according to any one of
the above-mentioned contents and includes the following steps:
[0020] S1. A first shielding layer is formed, wherein the first
shielding layer includes a first surface and a second surface
opposite to each other, and the second surface is a flat
surface.
[0021] S2. Multiple convex particles are formed on the second
surface of the first shielding layer.
[0022] S3. A second shielding layer is formed on the second surface
having the convex particles, wherein a protrusion portion is formed
at a position corresponding to the convex particles on an outer
surface of the second shielding layer, and a gentle portion is
formed at other positions.
[0023] S4. An adhesive film layer is formed on the outer surface of
the second shielding layer.
[0024] As an improvement of the above-mentioned solution, the first
shielding layer is formed in S1 by means of the following
manners.
[0025] A protective film layer is formed on a carrier film, and the
first shielding layer is formed on the protective film layer,
wherein the first surface is laminated with the protective film
layer or,
[0026] a peelable layer is formed on a carrier film, the first
shielding layer is formed on a surface of the peelable layer, and
after the projective film layer is formed on the first surface of
the first shielding layer, the carrier film layer is peeled.
[0027] As an improvement of the above-mentioned solution, before an
adhesive film layer is formed on the outer surface of the second
shielding layer, the method further includes the following
step:
[0028] Multiple conductive protrusions are formed on the outer
surface of the second shielding layer via one or more processes of
physical roughening, chemical plating, physical vapor deposition,
chemical vapor deposition, evaporation plating, splutter plating,
electroplating or mixed plating.
[0029] As an improvement of the above-mentioned solution, the step
that an adhesive film layer is formed on the outer surface of the
second shielding layer in S4 specifically includes:
[0030] a release film is coated with an adhesive film layer, and
then the adhesive film layer is laminated and transferred to the
outer surface of the second shielding layer so as to form the
adhesive film layer on the outer surface of the second shielding
layer, or,
[0031] the outer surface of the second shielding layer is directly
coated with an adhesive film layer so as to form the adhesive film
layer on the outer surface of the second shielding layer.
[0032] Compared with the related art, according to the preparation
method for the EMI shielding film provided by the embodiments of
the disclosure, multiple convex particles are formed on a second
surface of a first shielding layer, and a second shielding layer is
formed on the second surface having the convex particles, so that a
protrusion portion is formed at a position corresponding to the
convex particles on an outer surface of the second shielding layer,
and a gentle portion is formed at other positions. As a result, it
may be ensured that the shielding layers smoothly puncture an
adhesive film layer in a lamination process, the reliable grounding
is achieved, and the practicality is strong; meanwhile, the
insertion loss in use is reduced; and therefore, the preparation
method is applied to ultrahigh frequency transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a structure diagram of an EMI shielding film in
Embodiment 1 of the disclosure;
[0034] FIG. 2 is a structure diagram of an EMI shielding film in
Embodiment 2 of the disclosure;
[0035] FIG. 3 is a structure diagram of a circuit board in
Embodiment 3 of the disclosure;
[0036] FIG. 4 is a structure diagram of a circuit board in
Embodiment 4 of the disclosure; and
[0037] FIG. 5 is a flowchart of a preparation method for an EMI
shielding film in Embodiment 5 of the disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0038] The technical solutions in the embodiments of the disclosure
will be clearly and completely described herein below with the
drawings in the embodiments of the disclosure. Obviously, the
described embodiments are only part of the embodiments of the
disclosure, not all of the embodiments. On the basis of the
embodiments of the disclosure, all other embodiments obtained on
the premise of no creative work of a person of ordinary skill in
the art fall within the scope of protection of the disclosure.
[0039] Referring to FIG. 1, a structure diagram of an EMI shielding
film in Embodiment 1 of the disclosure is shown. As shown in FIG.
1, the EMI shielding film includes a first shielding layer 1, a
second shielding layer 2, an adhesive film layer 3 and multiple
convex particles, wherein the first shielding layer 1 includes a
first surface 11 and a second surface 12 opposite to each other,
the second surface 12 is a flat surface; the multiple convex
particles are adhered on the second surface 12 of the first
shielding layer 1; the second shielding layer 2 is disposed on the
second surface 12 of the first shielding layer 1 and covers the
multiple convex particles, thereby forming a protrusion portion 212
at a position corresponding to the convex particles 4 on an outer
surface 21 of the second shielding layer 2 and forming a gentle
portion 211 at other positions; and the adhesive film layer 3 is
disposed on the outer surface 21 of the second shielding layer
2.
[0040] Both the first shielding layer 1 and the second shielding
layer 2 have a function of conducting free electrons, and the
materials thereof may be the same and may also be different. The
first shielding layer 1 and the second shielding layer 2
specifically include one or more of a metal shielding layer, a
carbon nano tube shielding layer, a ferrite shielding layer or a
graphene shielding layer. The metal shielding layer includes a
single metal shielding layer and/or an alloy shielding layer,
wherein the single metal shielding layer is made of any one of
aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper,
silver or gold, and the alloy shielding layer is made of any two or
more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt,
copper, silver or gold. In addition, the adhesive film layer 3 is
preferably made of the followings: modified epoxy resins, modified
acrylates, modified rubbers, modified thermoplastic polyimides and
modified polyesters.
[0041] In the embodiment, the convex particles 4 are distributed on
the second surface 12 of the first shielding film (the second
surface 12 is the flat surface), and function as enabling the outer
surface 21 of the second shielding film to form a protrusion
portion 212, so that when the EMI shielding film is laminated with
a printed circuit board, the protrusion portion 212 can puncture
the adhesive film layer 3 and a ground layer of the printed circuit
board smoothly to implement reliable grounding. The convex
particles 4 include one or more of conductor particles,
semiconductor particles, insulator particles and coated compound
particles (conductor coated insulator particles, or another
insulator particles coated by an insulator, etc.), and further
include large particles agglomerated by small particles. In actual
application, the convex particles 4 are diamond powder, titanium
dioxide, silicon powder, silicide powder, silicon dioxide powder,
aluminide powder, graphene powder, iron powder, nickel powder,
copper powder, nickel-plated diamond powder, metal-plated inorganic
powder, etc. It is to be noted that the shape of the convex
particles 4 in the disclosure is not limited by graphical
representation, the material is also not limited by the above
materials, and particles which enable the outer surface 21 of the
second shielding layer to form the protrusion portion 212 are all
included in a protrusion scope of the disclosure.
[0042] In order to form the protrusion portion 212 puncturing the
adhesive film layer 3 sufficiently on the outer surface 21 of the
second shielding layer, the height of the convex particles 4 is
within a range of 0.1 .mu.m to 30 .mu.m. In addition, a
proportional relationship between the thickness of the adhesive
film layer 3 and the undulation degree of the outer surface 21 of
the second shielding layer (equivalent to the height of the
protrusion portion 212) is preferably 0.8-2, so as to ensure
sufficient puncture strength and adhesive receiving amount. In
specific implementation, on the one hand, the phenomenon of
delamination caused by insufficient adhesive receiving amount due
to too small thickness of the adhesive film layer 3 relative to the
undulation degree of the outer surface 21 of the second shielding
layer is prevented; and on the other hand, the phenomenon of
grounding failure caused by insufficient puncture strength due to
too small undulation degree of the outer surface 21 of the second
shielding layer relative to the thickness of the adhesive film
layer 3. It is to be noted that the undulation degree of the outer
surface 21 of the second shielding layer is a distance between a
highest point and a lowest point on the outer surface 21 of the
second shielding layer.
[0043] Based on the above structure, a protrusion portion 212 is
formed at a position corresponding to convex particles 4 on an
outer surface 21 of a second shielding layer 2 and a gentle portion
211 is formed at other portions, and an adhesive film layer 3 is
disposed on the outer surface 21 of the second shielding layer 2,
so the protrusion portion 212 on the outer surface 21 of the second
shielding layer 2 guarantees that the second shielding layer
smoothly punctures the adhesive film layer 3 in a lamination
process, and an interference charge is guided out normally;
meanwhile, the gentle portion 211 also can reduce the insertion
loss in use; and therefore, the EMI shielding film is applied to
ultrahigh frequency transmission.
[0044] Preferably, the adhesive film layer 3 is an adhesion layer
not containing conductive particles, so that the insertion loss of
a circuit board in use is reduced, the shielding effect is
accelerated, and the bendability of the circuit board is
improved.
[0045] In another preferred embodiment, the adhesive film layer 3
is an adhesion layer containing conductive particles, so that the
adhesive film layer 3 has an adhesive action to tightly adhere the
circuit board and the EMI shielding film, and further has a
conductive function to quickly guide the interference electron to
the ground layer of the circuit board in cooperation with the
second shielding layer 2. The conductive particles may be mutually
separated conductive particles, and may also be large agglomerated
conductive particles. When the conductive particles are the
mutually separated conductive particles, the area of electric
contact may be further improved to improve the evenness of the
electrical contact; and when the conductive particles are large
agglomerated conductive particles, the puncture strength may be
increased.
[0046] Preferably, the EMI shielding film further includes a
protective film layer, the protective film layer being formed on
the first surface 11 of the shielding layer 1. The protective film
layer has an insulated action to guarantee the shielding effect
between the first shielding layer 1 and the second shielding layer
2. The protective film layer is one of a Polyphenylene Sulfite
(PPS) film layer, a Polythylene Naphtalate (PEN) film layer, a
polyester film layer, a polyimide film layer, a film layer formed
after curing of epoxy resin ink, a film layer formed after curing
of polyurethane ink, a film layer formed after curing of modified
acrylic resin, and a film layer formed by curing of polyimide
resin.
[0047] It is to be noted that the first shielding layer 1 and the
second shielding layer 2 in the drawings of the present embodiments
may be of a single-layer structure or a multi-layer structure. In
addition, the first shielding layer and the second shielding layer
in the drawings of the present embodiment may be set to be
latticed, foamed or the like according to actual production and
application needs.
[0048] Referring to FIG. 2, a structure diagram of an EMI shielding
film in Embodiment 2 of the disclosure is shown. As shown in FIG.
2, the EMI shielding film includes a first shielding layer 1, a
second shielding layer 2, an adhesive film layer 3 and multiple
convex particles 4, wherein the multiple convex particles 4 are
disposed between the first shielding layer 1 and the second
shielding layer 2; the first shielding layer 1 includes a first
surface 11 and a second surface 12 opposite to each other; the
second surface 12 is a flat surface; the multiple convex particles
4 are adhered on the second surface of the first shielding layer;
the second shielding layer 2 is disposed on the second surface 12
of the first shielding layer 1 and covers the multiple convex
particles 4, thereby forming a protrusion portion 212 at a position
corresponding to the convex particles 4 on an outer surface 21 of
the second shielding layer 2 and forming a gentle portion 211 at
other positions; the adhesive film layer 3 is disposed on the outer
surface 21 of the second shielding layer 2; and multiple conductive
protrusions 5 are further formed on the outer surface 21 of the
second shielding layer 2.
[0049] The conductive protrusions 5 include one or more of metal
protrusions, carbon nano tube protrusions and ferrite protrusions.
The metal protrusions include single metal protrusions and/or an
alloy metal protrusions, wherein the single metal protrusions are
made of any one of aluminum, titanium, zinc, iron, nickel,
chromium, cobalt, copper, silver or gold, and the alloy metal
protrusions are made of any two or more of aluminum, titanium,
zinc, iron, nickel, chromium, cobalt, copper, silver or gold. It is
to be noted that the materials of the conductive protrusions 5, the
first shielding layer 1 and the second shielding layer 2 may be the
same, and may also be different.
[0050] The conductive protrusions 5 are preferably distributed on
the protrusion portion 212 intensively, so that the second
shielding layer 2 punctures the adhesive film layer 3 more easily
in a lamination process and thus the grounding is implemented and
the EMI shielding quality is improved.
[0051] Both the first shielding layer 1 and the second shielding
layer 2 have a function of conducting a free electron, and the
materials thereof may be the same and may also be different. The
first shielding layer 1 and the second shielding layer 2
specifically include one or more of a metal shielding layer, a
carbon nano tube shielding layer, a ferrite shielding layer or a
graphene shielding layer. The metal shielding layer includes a
single metal shielding layer and/or an alloy shielding layer,
wherein the single metal shielding layer is made of any one of
aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper,
silver or gold, and the alloy shielding layer is made of any two or
more of aluminum, titanium, zinc, iron, nickel, chromium, cobalt,
copper, silver or gold. In addition, the adhesive film layer 3 is
preferably made of the followings: modified epoxy resins, modified
acrylates, modified rubbers, modified thermoplastic polyimides and
modified polyesters.
[0052] In the embodiment, the convex particles 4 are distributed on
the second surface 12 of the first shielding film (the second
surface 12 is the flat surface), and function as enabling the outer
surface 21 of the second shielding film to form a protrusion
portion 212, so that when the EMI shielding film is laminated with
a printed circuit board, the protrusion portion 212 can puncture
the adhesive film layer 3 and a ground layer of the printed circuit
board smoothly to implement reliable grounding. The convex
particles 4 include one or more of conductor particles,
semiconductor particles, insulator particles and coated compound
particles (conductor coated insulator particles, or another
insulator particles coated by an insulator, etc.), and further
include large particles agglomerated by small particles. In actual
application, the convex particles 4 are diamond powder, titanium
dioxide, silicon powder, silicide powder, silicon dioxide powder,
aluminide powder, graphene powder, iron powder, nickel powder,
copper powder, nickel-plated diamond powder, metal-plated inorganic
powder, etc. It is to be noted that the shape of the convex
particles 4 in the disclosure is not limited by graphical
representation, the material is also not limited by the above
materials, and particles which enable the outer surface 21 of the
second shielding layer to form the protrusion portion 212 are all
included in a protrusion scope of the disclosure.
[0053] In order to form the protrusion portion 212 puncturing the
adhesive film layer 3 sufficiently on the outer surface 21 of the
second shielding layer, the height of the convex particles 4 is
within a range of 0.1 .mu.m to 30 .mu.m. In addition, a
proportional relationship between the thickness of the adhesive
film layer 3 and the sum of the undulation degree of the outer
surface 21 of the second shielding layer (equivalent to the height
of the protrusion portion 212) and the height of the conductive
protrusions 5 is preferably 0.8-2, so as to ensure sufficient
puncture strength and adhesive receiving amount. In specific
implementation, on the one hand, the phenomenon of delamination
caused by insufficient adhesive receiving amount due to too small
thickness of the adhesive film layer 3 relative to the sum of the
undulation degree of the outer surface 21 of the second shielding
layer and the height of the conductive protrusions 5 is prevented;
and on the other hand, the phenomenon of grounding failure caused
by insufficient puncture strength due to too small sum of the
undulation degree of the outer surface 21 of the second shielding
layer and the height of the conductive protrusions 5 relative to
the thickness of the adhesive film layer 3. It is to be noted that
the undulation degree of the outer surface 21 of the second
shielding layer is a distance between a highest point and a lowest
point on the outer surface 21 of the second shielding layer.
[0054] Based on the above structure, a protrusion portion 212 is
formed at a position corresponding to convex particles 4 on an
outer surface 21 of a second shielding layer 2 and a gentle portion
211 is formed at other portions, an adhesive film layer 3 is
disposed on the outer surface 21 of the second shielding layer 2
and multiple conductive protrusions 5 are further formed on the
outer surface 21 of the second shielding layer 2, so the protrusion
portion 212 on the outer surface 21 of the second shielding layer
is cooperated with the conductive protrusions 5 thereon to enhance
the puncture function and guarantee that the second shielding layer
2 smoothly punctures the adhesive film layer 3 in a lamination
process, and an interference charge is guided out normally, thus
implementing the reliable grounding; meanwhile, the gentle portion
211 also can reduce the insertion loss in use; and therefore, the
EMI shielding film is applied to ultrahigh frequency
transmission.
[0055] Preferably, the adhesive film layer 3 is an adhesion layer
not containing conductive particles, so that the insertion loss of
a circuit board in use is reduced, the shielding effect is
accelerated, and the bendability of the circuit board is
improved.
[0056] In addition, the conductive protrusions 5 are preferably
distributed on the protrusion portion 212 intensively, so that the
second shielding layer 2 punctures the adhesive film layer 3 more
easily in a lamination process and thus the grounding is
implemented and the EMI shielding quality is improved.
[0057] In another preferred embodiment, the adhesive film layer 3
is an adhesion layer containing conductive particles, so that the
adhesive film layer 3 has an adhesive action to tightly adhere the
circuit board and the EMI shielding film, and further has a
conductive function to quickly guide the interference electron to
the ground layer of the circuit board in cooperation with the
second shielding layer 2. The conductive particles may be mutually
separated conductive particles, and may also be large agglomerated
conductive particles. When the conductive particles are the
mutually separated conductive particles, the area of electric
contact may be further improved to improve the evenness of the
electrical contact; and when the conductive particles are large
agglomerated conductive particles, the puncture strength may be
increased.
[0058] Preferably, the EMI shielding film further includes a
protective film layer, the protective film layer being formed on
the first surface 11 of the shielding layer 1. The protective film
layer has an insulated action to guarantee the shielding effect
between the first shielding layer 1 and the second shielding layer
2. The protective film layer is one of a Polyphenylene Sulfite
(PPS) film layer, a Polythylene Naphtalate (PEN) film layer, a
polyester film layer, a polyimide film layer, a film layer formed
after curing of epoxy resin ink, a film layer formed after curing
of polyurethane ink, a film layer formed after curing of modified
acrylic resin, and a film layer formed by curing of polyimide
resin.
[0059] It is to be noted that the first shielding layer 1 and the
second shielding layer 2 in the drawings of the present embodiments
may be of a single-layer structure or a multi-layer structure. In
addition, the first shielding layer and the second shielding layer
in the drawings of the present embodiment may be set to be
latticed, foamed or the like according to actual production and
application needs.
[0060] Referring to FIG. 3, a structure diagram of a circuit board
in Embodiment 3 of the disclosure is shown. The circuit board
includes a printed circuit board 6 and the EMI shielding film in
Embodiment 1, wherein the EMI shielding film is laminated with the
printed circuit board 6 through an adhesive film layer 3; and a
protrusion portion 212 punctures the adhesive film layer 3 and
extends to a ground layer of the printed circuit board 6.
[0061] In the embodiment, the implementation manner of the EMI
shielding film may be referred to the description in Embodiment 1
and will not be repeated herein.
[0062] Preferably, the printed circuit board 6 is one of a flexible
single-side board, a flexible double-side board, a flexible
multi-layer board or a rigid combined board.
[0063] By means of the above-mentioned structure, in a lamination
process, the adhesive film layer 3 is punctured by using the
protrusion portion 212 of the second shielding layer 2, so at least
part of the outer surface 21 of the second shielding layer 2 is
connected to the ground layer of the printed circuit board. Thus,
the interference charge in the first shielding layer 1 and the
second shielding layer 2 is guided into the ground, thereby
avoiding influence on normal operation of the circuit board caused
by forming of an interference source due to gathering of the
interference charge. Meanwhile, the gentle portion 211 also can
reduce the insertion loss in use. Therefore, the circuit board is
applied to ultrahigh frequency transmission.
[0064] Referring to FIG. 4, a structure diagram of a circuit board
in Embodiment 4 of the disclosure is shown. The circuit board
includes a printed circuit board 6 and the EMI shielding film in
Embodiment 2, wherein the EMI shielding film is laminated with the
printed circuit board 6 through an adhesive film layer 3; and a
protrusion portion 212 punctures the adhesive film layer 3 and
extends to a ground layer of the printed circuit board 6.
[0065] In the embodiment, the implementation manner of the EMI
shielding film may be referred to the description in Embodiment 2
and will not be repeated herein.
[0066] By means of the above-mentioned structure, in a lamination
process, the protrusion portion 212 are cooperated with the
conductive protrusions 5 thereon to puncture the adhesive film
layer 3, so at least part of the outer surface 21 of the second
shielding layer 2 is connected to the ground layer of the printed
circuit board. Thus, the interference charge in the first shielding
layer 1 and the second shielding layer 2 is guided into the ground,
thereby avoiding influence on normal operation of the circuit board
caused by forming of an interference source due to gathering of the
interference charge. Meanwhile, the gentle portion 211 also can
reduce the insertion loss in use. Therefore, the circuit board is
applied to ultrahigh frequency transmission.
[0067] Referring to FIG. 5, a flowchart of a preparation method for
an EMI shielding film in Embodiment 5 of the disclosure is shown.
The method is applied to preparation of the EMI shielding film in
Embodiment 1, and includes the following steps:
[0068] S1. A first shielding layer is formed, wherein the first
shielding layer includes a first surface and a second surface
opposite to each other, and the second surface is a flat
surface.
[0069] The first shielding layer is formed in step S1 by means of
the following manners.
[0070] A protective film layer is formed on a carrier film, and the
first shielding layer is formed on the protective film layer,
wherein the first surface is laminated with the protective film
layer or,
[0071] a peelable layer is formed on a carrier film, the first
shielding layer is formed on a surface of the peelable layer, and
after the projective film layer is formed on the first surface of
the first shielding layer, the carrier film layer is peeled.
[0072] S2. Multiple convex particles are formed on the second
surface of the first shielding layer.
[0073] S3. A second shielding layer is formed on the second surface
having the convex particles, wherein the second shielding layer is
formed on the second surface having the convex particles, a
protrusion portion is formed at a position corresponding to the
convex particles on an outer surface of the second shielding layer,
and a gentle portion is formed at other positions.
[0074] S4. An adhesive film layer is formed on the outer surface of
the second shielding layer.
[0075] The step that an adhesive film layer is formed on the outer
surface of the second shielding layer in S4 specifically includes
the following step:
[0076] a release film is coated with an adhesive film layer, and
then the adhesive film layer is laminated and transferred to the
outer surface of the second shielding layer so as to form the
adhesive film layer on the second surface of the shielding layer;
or,
[0077] the outer surface of the second shielding layer is directly
coated with an adhesive film layer so as to form the adhesive film
layer on the outer surface of the second shielding layer.
[0078] It is to be noted that the formation of the first shielding
layer, the convex particles, the second shielding layer or the
glass layer may preferably use a chemical playing manner, PVD, CVD,
evaporation plating, splutter plating, electroplating or mixed
plating.
[0079] In another preferred embodiment applied to the preparation
of the EMI shielding film in Embodiment 2, prior to the step 4, the
method further includes the following step:
[0080] multiple conductive protrusions are formed on the outer
surface of the second shielding layer via one or more processes of
physical roughening, chemical plating, physical vapor deposition,
chemical vapor deposition, evaporation plating, splutter plating,
electroplating or mixed plating.
[0081] The above description is a preferred implementation manner
of the disclosure. It should be noted that those of ordinary skill
in the art may also make some improvements and modifications
without departing from the principle of the disclosure. These
improvements and modifications fall within the scope of protection
of the disclosure.
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