Disclosure of Invention
Problems to be solved by the invention
When such an electromagnetic wave shielding film is disposed on a printed circuit board and then components are mounted by reflow soldering or the like, there is a problem in that interlayer adhesion between an adhesive layer and a metal layer of the electromagnetic wave shielding film is broken and interlayer peeling occurs.
The reason why the above-described interlayer peeling occurs is considered to be based on the following mechanism.
Fig. 3A and 3B are explanatory views schematically showing a mechanism of interlayer separation between an adhesive layer and a metal layer when a shield printed circuit board is manufactured using a conventional electromagnetic wave shielding film.
As shown in fig. 3A, in manufacturing a shielded printed circuit board, an electromagnetic wave shielding film 510 in which an adhesive layer 520 and a shielding layer 530 formed of a metal layer are laminated in this order is heated by heating pressing and solder reflow.
By this heating, volatile components (mainly, moisture) 560 are generated from the adhesive layer 520 or the like of the electromagnetic wave shielding film 510, and are accumulated between the adhesive layer 520 and the shielding layer 530.
When intense heating such as reflow soldering is performed for component mounting in such a state, as shown in fig. 3B, the volatile component 560 accumulated between the adhesive layer 520 and the shielding layer 530 expands, and interlayer adhesion between the adhesive layer 520 and the shielding layer 530 is broken, and interlayer peeling occurs.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electromagnetic wave shielding film and a method for producing the electromagnetic wave shielding film, in which the interlayer adhesion between an adhesive layer and a shielding layer is not easily broken even when the film is heated by reflow soldering or the like.
Solution for solving the problem
The present inventors have found that the reason why volatile components accumulate between the adhesive layer and the shielding layer is that the adhesive layer absorbs moisture in the air during storage of the electromagnetic wave shielding film, and the problem can be solved by reducing the hygroscopicity of the adhesive layer, and have found the present invention.
That is, the electromagnetic wave shielding film of the present invention is characterized by comprising a conductive adhesive layer and a shielding layer laminated on the conductive adhesive layer, wherein the conductive adhesive layer contains 50 wt% or less of a conductive filler, and the specific surface area of the conductive filler is 0.9m2/g or less.
In the electromagnetic wave shielding film of the present invention, since the conductive adhesive layer contains 50 wt% or less of the conductive filler, conductivity can be imparted to the conductive adhesive layer, and the adhesive strength of the conductive adhesive is increased.
In the electromagnetic wave shielding film of the present invention, as will be described later, volatile components are less likely to enter the periphery of the conductive filler. Therefore, by containing the conductive filler, the hygroscopicity of the entire adhesive layer decreases. Therefore, in the electromagnetic wave shielding film of the present invention, even when heated by reflow soldering or the like, the interlayer adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily broken.
The reason why the volatile components in the electromagnetic wave shielding film of the present invention are less likely to enter the periphery of the conductive filler will be described.
In the electromagnetic wave shielding film of the present invention, the specific surface area of the conductive filler is 0.9m2/g or less.
When the specific surface area of the conductive filler is within the above range, the angle of the surface of the conductive filler becomes small (for example, the surface is close to a sphere), and volatile components such as moisture are less likely to accumulate around the conductive filler.
When the specific surface area exceeds 0.9m2/g, the surface of the conductive filler is uneven, surface branches are increased, and volatile components such as moisture are easily accumulated between the branches. Therefore, the hygroscopicity of the entire conductive adhesive layer is easily improved.
In the electromagnetic wave shielding film of the present invention, the tap density of the conductive filler is preferably 1g/cm3 or more.
When the tap density is 1g/cm3 or more, the volume of the conductive filler becomes low, and the contact points between the conductive fillers become small, so that volatile components are less likely to accumulate between the conductive fillers, and interlayer damage due to the heating is less likely to occur.
If the tap density is less than 1g/cm3, the volume of the conductive filler increases, and the number of contacts between the conductive fillers increases, so that volatile components tend to accumulate between the conductive fillers, and it becomes difficult to suppress interlayer damage due to the above-mentioned heating.
The tap density of the conductive filler is the density of powder obtained by knocking a container under a predetermined condition, and is a value measured according to JIS Z2512:2012 (metal powder-tap density measurement method).
In the electromagnetic wave shielding film of the present invention, it is preferable that an insulating layer is further laminated on the shielding layer.
By forming the insulating layer, the shielding layer and the adhesive layer can be protected. In addition, the presence of the insulating layer can prevent the shielding layer from contacting other conductive members.
The method for producing an electromagnetic wave shielding film is characterized by comprising a step of mixing a conductive filler and a resin, a step of preparing a conductive adhesive containing 50 wt% or less of the conductive filler, and a step of forming a conductive adhesive layer by applying the conductive adhesive to a shielding layer, wherein the specific surface area of the conductive filler is 0.9m2/g or less.
In the method for producing an electromagnetic wave shielding film of the present invention, since the conductive adhesive contains 50 wt% or less of the conductive filler, the conductive adhesive layer can be provided with conductivity, and the adhesive strength of the conductive adhesive can be increased.
In the method for producing an electromagnetic wave shielding film of the present invention, since the specific surface area of the conductive filler is 0.9m2/g or less, the interlayer adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily broken even when the electromagnetic wave shielding film is heated by reflow soldering or the like, as in the case of the electromagnetic wave shielding film of the present invention.
In the method for producing an electromagnetic wave shielding film of the present invention, the tap density of the conductive filler is preferably 1g/cm3 or more.
When the tap density is 1g/cm3 or more, interlayer failure due to the heating is less likely to occur as in the case of the electromagnetic wave shielding film of the present invention.
If the tap density is less than 1g/cm3, it becomes difficult to suppress interlayer failure due to the above-mentioned heating, as in the case of the electromagnetic wave shielding film of the present invention.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide an electromagnetic wave shielding film and a method for producing an electromagnetic wave shielding film, in which the interlayer adhesion between an adhesive layer and a shielding layer is not easily broken even when heated by reflow soldering or the like.
Detailed Description
Hereinafter, the electromagnetic wave shielding film and the method for producing the electromagnetic wave shielding film according to the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and can be applied with appropriate modifications within the scope of not changing the gist of the present invention.
Fig. 1 is a cross-sectional view schematically showing an example of an electromagnetic wave shielding film of the present invention.
The electromagnetic wave shielding film 10 shown in fig. 1 includes a conductive adhesive layer 20 and a shielding layer 30 laminated on the conductive adhesive layer 20, and an insulating layer 40 is further laminated on the shielding layer 30.
The conductive adhesive layer 20 contains a resin and a conductive filler.
In the electromagnetic wave shielding film 10, since the conductive adhesive layer 20 contains 50 wt% or less of the conductive filler, the conductive adhesive layer 20 can be given conductivity, and the adhesive strength of the conductive adhesive is increased.
In the electromagnetic wave shielding film 10, the specific surface area of the conductive filler is 0.9m2/g or less.
Since the conductive filler has such a characteristic, volatile components are less likely to enter the periphery of the conductive filler. Therefore, by containing the conductive filler, the hygroscopicity of the entire conductive adhesive layer 20 decreases. Therefore, even when the electromagnetic wave shielding film 10 is heated by reflow soldering or the like, the interlayer adhesion between the conductive adhesive layer 20 and the shielding layer 30 is not easily broken.
The reason why the volatile component is less likely to enter the periphery of the conductive filler when the conductive filler has the above-described characteristics will be described below.
When the specific surface area of the conductive filler is 0.9m2/g or less, the angle of the surface of the conductive filler becomes small (for example, the surface is close to a sphere), and volatile components such as moisture are less likely to accumulate around the conductive filler.
When the specific surface area exceeds 0.9m2/g, the surface of the conductive filler is uneven, surface branches are increased, and volatile components such as moisture are easily accumulated between the branches. Therefore, the hygroscopicity of the entire conductive adhesive layer is easily improved.
The specific surface area of the conductive filler is preferably 0.25m2/g or more and 0.9m2/g or less, more preferably 0.25m2/g or more and less than 0.8m2/g, and still more preferably 0.25m2/g or more and 0.5m2/g or less.
The specific surface area of the conductive filler can be measured by a nitrogen adsorption method using an elemental analyzer VARI EL III (manufactured by Elementar).
In the electromagnetic wave shielding film 10, the tap density of the conductive filler is preferably 1g/cm3 or more, more preferably 1.5g/cm3 or more and 5.0g/cm3 or less, and still more preferably 2.0g/cm3 or more and 5.0g/cm3 or less.
When the tap density is 1g/cm3 or more, the volume of the conductive filler becomes low, and the contact points between the conductive fillers become small, so that volatile components are less likely to accumulate between the conductive fillers, and interlayer damage due to the heating is less likely to occur.
If the tap density is less than 1g/cm3, the volume of the conductive filler increases, and the number of contacts between the conductive fillers increases, so that volatile components are easily accumulated between the conductive fillers, and it becomes difficult to suppress interlayer damage due to the above-mentioned heating.
A conductive filler having a tap density of 5.0g/cm3 or less is easy to manufacture.
In the electromagnetic wave shielding film 10, the conductive adhesive layer 20 contains 50 wt% or less of a conductive filler, preferably 3 wt% or more and 39 wt% or less of a conductive filler, more preferably 3 wt% or more and 35 wt% or less of a conductive filler, and still more preferably 3 wt% or more and 30 wt% or less of a conductive filler.
If the proportion of the conductive filler exceeds 50% by weight, the proportion of the resin in the conductive adhesive layer becomes relatively small, and the adhesive strength of the conductive adhesive layer tends to be lowered. Further, since the conductive fillers are easily in contact with each other (current is easily flowing in the plane direction), electrical characteristics such as transmission characteristics are easily lowered.
When the proportion of the conductive filler is 3% by weight or more and 39% by weight or less, anisotropic conductivity can be imparted to the conductive adhesive layer 20.
If the proportion of the conductive filler is less than 3% by weight, the conductive filler becomes less likely to exhibit conductivity.
In this way, the conductive adhesive layer 20 may have isotropic conductivity in which an electrically conductive state is ensured in all three dimensions including the thickness direction, the width direction, and the length direction, or may have anisotropic conductivity in which an electrically conductive state is ensured only in the thickness direction, but preferably has anisotropic conductivity.
As described later, the electromagnetic wave shielding film 10 is disposed on a printed circuit board.
When the conductive adhesive layer 20 has anisotropic conductivity, the transmission characteristics of the high-frequency signal transmitted through the signal circuit of the printed circuit board are improved as compared with the case of having isotropic conductivity.
In the electromagnetic wave shielding film 10, the particle diameter (D50) of the conductive filler is preferably 3.0 μm or more and 15 μm or less, more preferably 5.0 μm or more and 11 μm or less, still more preferably 5.0 μm or more and 8.0 μm or less.
If the particle diameter (D50) of the conductive filler is less than 3.0 μm, the conductive adhesive layer 20 is thicker than the conductive filler, and the conductive filler may not be in contact with the ground circuit, and conductivity may not be obtained.
If the particle diameter (D50) of the conductive filler exceeds 15 μm, the conductive filler may puncture the insulating layer 40 (may cause poor appearance).
The conductive filler in the electromagnetic wave shielding film 10 is not particularly limited, and may be metal particles, carbon nanotubes, carbon fibers, metal fibers, or the like.
In the case where the conductive filler is a metal particle, the metal particle is not particularly limited, and may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by silver plating copper powder, polymer particles coated with a metal, glass beads, or the like.
Among these, copper powder or silver-coated copper powder that can be obtained at low cost is preferable from the viewpoint of economy.
The shape of the conductive filler is not particularly limited, and may be appropriately selected from a sphere, a flat, a scale, a branch (dendrimer), a rod, a fiber, and the like.
In the electromagnetic wave shielding film 10, the thickness of the conductive adhesive layer 20 is preferably 5 to 50 μm, more preferably 5 to 30 μm.
If the thickness of the conductive adhesive layer is less than 5 μm, the adhesion is reduced due to the thinness.
If the thickness of the conductive adhesive layer exceeds 50 μm, the conductive adhesive layer becomes thicker, making it difficult to miniaturize the electromagnetic wave shielding film.
In the electromagnetic wave shielding film 10, the material of the resin of the conductive adhesive layer 20 is not particularly limited, and a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, a thermoplastic resin composition such as an imide resin composition, an amide resin composition, an acrylic resin composition, a phenol resin composition, an epoxy resin composition, a polyurethane resin composition, a melamine resin composition, a thermosetting resin composition such as an alkyd resin composition, and the like can be used.
The resin material may be 1 kind of these alone or a combination of 2 or more kinds thereof.
The electromagnetic wave shielding film 10 may contain, in addition to the resin and the conductive filler, a curing accelerator, an adhesiveness-imparting agent, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity regulator, and the like, as necessary.
In the electromagnetic wave shielding film 10, the shielding layer 30 is preferably formed of a metal layer.
In addition, the metal layer preferably contains at least 1 metal selected from the group consisting of copper, silver, gold, aluminum, nickel, tin, palladium, chromium, titanium, and zinc. In addition, the metal layer may be formed of an alloy of at least 2 selected from the group thereof.
The shielding layer 30 formed of these metals can appropriately shield electromagnetic waves.
In the electromagnetic wave shielding film 10, when the shielding layer 30 is formed of a metal layer, the metal layer may be a rolled metal foil, a metal plating layer, or a metal vapor plating layer.
In the electromagnetic wave shielding film 10, when the shielding layer 30 is formed of a metal layer, the thickness thereof is preferably 0.1 to 10 μm, more preferably 0.5 to 6 μm.
If the thickness of the shielding layer is less than 0.1 μm, the shielding layer is too thin, and thus the strength of the shielding layer becomes low. Therefore, the bending resistance is lowered. In addition, it is difficult to sufficiently reflect and absorb electromagnetic waves, so that the electromagnetic wave shielding characteristics are liable to be degraded.
If the thickness of the shielding layer exceeds 10 μm, the electromagnetic wave shielding film becomes thick as a whole, and it becomes difficult to handle.
In the electromagnetic wave shielding film 10, the insulating layer 40 is not particularly limited as long as it has sufficient insulation properties and can protect the shielding layer 30 and the conductive adhesive layer 20, and is preferably composed of, for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray-curable composition, or the like.
The thermoplastic resin composition is not particularly limited, and examples thereof include a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, an imide resin composition, and an acrylic resin composition.
The thermosetting resin composition is not particularly limited, and examples thereof include phenol resin compositions, epoxy resin compositions, polyurethane resin compositions, melamine resin compositions, alkyd resin compositions, and the like.
The active energy ray-curable composition is not particularly limited, and examples thereof include polymerizable compounds having at least 2 (meth) acryloyloxy groups in the molecule.
The insulating layer 40 may be made of 1 material alone or 2 or more materials.
The insulating layer 40 may further contain a curing accelerator, an adhesiveness-imparting agent, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling agent, a filler, a flame retardant, a viscosity regulator, an antiblocking agent, and the like as necessary.
The pigment is not particularly limited, and examples thereof include black pigments such as carbon black.
The thickness of the insulating layer 40 is not particularly limited, and may be appropriately set as required, and is preferably 1 to 15 μm, more preferably 3 to 10 μm.
If the thickness of the insulating layer 40 is less than 1 μm, it becomes difficult to sufficiently protect the shielding layer 30 and the conductive adhesive layer 20 due to the excessive thinness.
If the thickness of the insulating layer 40 exceeds 15 μm, the electromagnetic wave shielding film 10 is not easily bent due to the excessive thickness, and the toughness of the insulating layer 40 is lowered. Therefore, it is difficult to apply to a member requiring bending resistance.
In the electromagnetic wave shielding film of the present invention, the insulating layer may be formed as needed, or the insulating layer may not be formed.
Next, a method for producing the electromagnetic wave shielding film of the present invention will be described.
The method for producing an electromagnetic wave shielding film comprises a step of mixing a conductive filler and a resin, a step of preparing a conductive adhesive containing 50 wt% or less of the conductive filler, and a step of forming a conductive adhesive layer by applying the conductive adhesive to a shielding layer, wherein the specific surface area of the conductive filler is 0.9m2/g or less.
In the method for manufacturing an electromagnetic wave shielding film according to the present invention, the step of forming the shielding layer on the insulating layer is performed before the step of forming the conductive adhesive layer, whereby the electromagnetic wave shielding film 10 can be manufactured.
Hereinafter, each step will be described in detail.
(Conductive adhesive preparation step)
In this step, a conductive adhesive containing 50 wt% or less of a conductive filler is prepared by mixing the conductive filler with a resin. Here, the specific surface area of the conductive filler is 0.9m2/g or less.
Since the conductive adhesive contains 50 wt% or less of the conductive filler, conductivity can be imparted to the conductive adhesive layer, and the adhesive strength of the conductive adhesive becomes high.
Further, since the specific surface area of the conductive filler is 0.9m2/g or less, the interlayer adhesion between the conductive adhesive layer as the adhesive layer and the shielding layer is not easily broken even when heated by reflow soldering or the like.
As described above, the specific surface area of the conductive filler is preferably 0.25m2/g or more and 0.9m2/g or less, more preferably 0.25m2/g or more and less than 0.8m2/g, and still more preferably 0.25m2/g or more and 0.5m2/g or less.
As described above, the conductive adhesive preferably contains 3% by weight to 39% by weight of the conductive filler, more preferably contains 3% by weight to 35% by weight of the conductive filler, and still more preferably contains 3% by weight to 30% by weight of the conductive filler.
As described above, the tap density of the conductive filler is preferably 1g/cm3 or more, more preferably 1.5g/cm3 or more and 5.0g/cm3 or less, and still more preferably 2.0g/cm3 or more and 5.0g/cm3 or less.
Preferred materials of the conductive filler and the resin have already been described, and therefore description thereof is omitted here.
(Step of Forming a Shielding layer)
In this step, a shielding layer is formed on the insulating layer.
In this case, the metal vapor deposition layer may be formed on the insulating layer by vapor deposition, a rolled metal foil may be attached to the insulating layer, or a metal plating layer may be formed on the insulating layer by electroplating.
Preferred materials for the insulating layer and the shielding layer have already been described, and therefore description thereof is omitted here.
(Conductive adhesive layer Forming step)
After the shield layer forming step, in this step, a conductive adhesive is applied to the shield layer to form a conductive adhesive layer.
As a method of disposing the conductive adhesive layer, conventionally known coating methods such as a gravure coating method, a kiss coating method, a die coating method, a lip coating method, a comma coating method, a knife coating method, a roll coating method, a knife coating method, a spray coating method, a bar coating method, a spin coating method, a dip coating method, and the like are exemplified.
Through the above steps, the electromagnetic wave shielding film 10 can be manufactured.
Next, a shield printed circuit board using the electromagnetic wave shield film of the present invention will be described.
Fig. 2 is a cross-sectional view schematically showing an example of a shield printed circuit board using the electromagnetic wave shielding film of the present invention.
The shield printed circuit board 1 shown in fig. 2 includes a printed circuit board 50 and an electromagnetic wave shielding film 10.
The printed circuit board 50 includes a base film 51, a printed circuit 52 disposed on the base film 51, and a cover layer 53 disposed so as to cover the printed circuit 52.
In the printed circuit board 50, the printed circuit 52 includes a ground circuit 52a, and an opening 53a exposing the ground circuit 52a is formed in the cover layer 53.
In the shield printed circuit board 1, the electromagnetic wave shielding film 10 is disposed on the printed circuit board 50 so that the cover layer 53 contacts the conductive adhesive layer 20.
In the shield printed circuit board 1, the conductive adhesive layer 20 fills the opening 53a of the cover layer 53 and contacts the ground circuit 52 a. By forming such a structure, the shielding characteristics of the electromagnetic wave shielding film 10 can be improved.
Examples
Hereinafter, examples of the present invention will be described more specifically, but the present invention is not limited to these examples.
Example 1
As the insulating layer, an insulating layer formed of epoxy resin having a thickness of 5 μm was prepared.
Then, electroplating was performed on the insulating layer to form a copper layer having a thickness of 2.0 μm. The copper layer functions as a shield layer.
Next, a polyester thermosetting resin as a resin and silver powder (particle diameter D50: 10.8 μm) as a conductive filler were mixed so that the total amount of the conductive filler relative to the conductive adhesive became 20% by weight, to prepare a conductive adhesive of example 1. Table 1 shows parameters such as specific surface area of the conductive filler used and conductivity of the conductive adhesive produced.
Next, the conductive adhesive was applied to the shielding layer so as to have a thickness of 20 μm, thereby producing an electromagnetic wave shielding film of example 1.
TABLE 1
(Examples 2) to (example 6) and (comparative examples 1) to (comparative example 9)
Electromagnetic wave shielding films of examples 2 to 6 and comparative examples 1 to 9 were produced in the same manner as in example 1 except that the proportions of the conductive fillers were changed using the materials shown in table 1 as the conductive fillers.
(Evaluation of the presence or absence of delamination)
The electromagnetic wave shielding films of each example and each comparative example were bonded to a printed circuit board by hot pressing. Next, the printed circuit board was left in a constant temperature and humidity tank at 30 ℃ and 60% rh for 1 day, and then exposed to a temperature condition at the time of reflow soldering, and the presence or absence of interlayer peeling was evaluated. The temperature of up to 260 ℃ was set as a temperature condition at the time of reflow soldering. Further, the presence or absence of interlayer peeling was evaluated by visually observing the presence or absence of swelling of the printed circuit board with the shielding film attached to the solder bath by floating 3 times in the solder bath. Here, a case where the shielding film does not swell at all is referred to as "excellent", a case where the shielding film only has a part of swell, and a case where the shielding film has a remarkable swell over the whole surface are referred to as "" x ". The results are shown in Table 1.
(Evaluation of adhesive Strength)
The electromagnetic wave shielding films of examples and comparative examples were used to evaluate the adhesive strength in the following manner.
Fig. 4A is a cross-sectional view schematically showing a sample used in an evaluation test of adhesive strength.
As shown in fig. 4A, first, each electromagnetic wave shielding film 10 in which the insulating layer 40, the shielding layer 30, and the conductive adhesive layer 20 are laminated in this order is pressed against the polyimide film base material side of a copper-clad laminate (polyimide film base material/adhesive layer/electroless gold plated copper foil) as the base material 61 under conditions of 2MPa, 170 ℃,10 sec, and 180 sec. Next, the electromagnetic wave shielding film 10 attached to the base material 61 was pressed against the bonding film 62b side of the reinforcing film 62 (polyimide film base 62 a/bonding film 62 b) under conditions of 3MPa, 170 ℃ for 3 minutes. Thereafter, these laminates were heated at 150 ℃ for 60 minutes to post-cure. Finally, the reinforcing film 62 of these laminates was attached to the double-sided tape 63b side of the fixing plate 63 (glass epoxy substrate 63 a/double-sided tape 63 b), and a sample 60 having a width of 10mm was prepared.
Fig. 4B is a cross-sectional view schematically showing a sample in an evaluation test of adhesive strength.
Then, the base material 61 was stretched under conditions of a stretching speed of 50mm/min and a stretching angle of 180 ° with the sample 60 fixed as shown in fig. 4B, whereby the base material 61 and the electromagnetic wave shielding film 10 were peeled off, and the average peeling force at this time was measured. The evaluation test was performed 5 times. The results are shown in Table 1.
The evaluation criteria were as follows. When the average peel force is 4N/10mm or more, the electromagnetic wave shielding film is suitable for practical use, and when the average peel force is less than 4N/10mm, the electromagnetic wave shielding film is not suitable for practical use.
Excellent in that the average peel force is 5N/10mm or more
The average peel force is more than 4N/10mm and less than 5N/10mm
X average peel force of less than 4N/10mm
As shown in table 1, it is clear that almost no interlayer peeling occurred in the electromagnetic wave shielding films of the respective examples.
Description of the reference numerals
1. Shielded printed circuit board
10. 510 Electromagnetic wave shielding film
20. Conductive adhesive layer
30. 530 Shielding layer
40. 540 Insulating layer
50. Printed circuit board with improved heat dissipation
51. Base film
52. Printed circuit
52A ground circuit
53. Cover layer
53A opening part
60. Sample of
61. Base material
62. Reinforced film
62A polyimide film substrate
62B bonding film
63. Fixing plate
63A glass epoxy substrate
63B double-sided tape
520. Adhesive layer
560. Volatile components.