Shielded printed circuit board and method for manufacturing the same

Abstract

Provided is a shielded printed circuit board, which has excellent connection stability even when the opening area of ​​the through hole is small, and has a high degree of freedom in circuit design. The shielded printed circuit board 1 of the present invention includes a printed circuit board 10, an insulating layer 22, and a conductive adhesive layer 21 arranged between the printed circuit board 10 and the insulating layer 22, the printed circuit board 10 contains a base component 11, a circuit pattern 13 provided on the surface of the base component, and an insulating protective layer 14 covering the circuit pattern 13, the shielded printed circuit board contains a through hole 23 for external grounding connection that penetrates the insulating layer 22 and the conductive adhesive layer 21 in the thickness direction, and the conductive adhesive layer 21 contains an extension portion 21a that extends further into the through hole 23 than the insulating layer 22.

Description

Technical Field

[0001] The invention relates to a shielded printed circuit board and a method for manufacturing the shielded printed circuit board. Background Art

[0002] Printed circuit boards are often used to assemble circuits into mechanisms in electronic devices such as mobile phones, video cameras, and notebook personal computers. In addition, printed circuit boards are also used to connect movable parts such as print heads with control parts. Electromagnetic wave shielding measures must be taken in the above electronic devices, and shielded printed circuit boards that implement electromagnetic wave shielding measures are also used in printed circuit boards used in devices.

[0003] For example Figure 6 As shown, as the above-mentioned shielded printed circuit board, a substrate 100 with an electromagnetic wave shielding layer is disclosed, the substrate 100 contains an electromagnetic wave shielding laminate 120, the electromagnetic wave shielding laminate 120 is arranged between a circuit substrate 110 and a grounding portion 140 connected to a grounding portion 150 of a main body of an electronic device, an electromagnetic wave shielding layer 121 and an insulating layer 122 are sequentially laminated on an insulating protective film 111 of the circuit substrate 110, and contains a through hole 123 penetrating the electromagnetic wave shielding layer 121 and the insulating layer 122, a grounding portion 140 composed of a conductive adhesive layer 141 and a grounding connecting member 142 is placed on the upper side of the through hole 123, and the electromagnetic wave shielding layer 121 and the insulating layer 122 are laminated so that the electromagnetic wave shielding layer 121 and the grounding portion 140 are electrically connected via the through hole 123 (refer to patent document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent Application Publication No. 2018-041953. Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] In recent years, as signals have become faster and devices have become thinner and smaller, the gaps between lines have become narrower, requiring a higher degree of freedom in circuit design. In addition, there is a need for a technology that can more effectively prevent electromagnetic interference (EMI) associated with high-speed transmission.

[0009] Patent Document 1 states that the electromagnetic wave shielding laminate disclosed in the document can be electrically connected to a ground connection member via through holes penetrating the electromagnetic wave shielding layer and the insulating layer, thereby achieving an effect of reliably performing ground connection and improving the reliability of the ground connection.

[0010] In the substrate with an electromagnetic wave shielding layer disclosed in Patent Document 1, the conductive adhesive layer 141 of the grounding portion 140 needs to be physically connected to the electromagnetic wave shielding layer 121 and the conductive adhesive layer of the electromagnetic wave shielding laminate 120 to achieve electrical connection. Therefore, in the substrate with an electromagnetic wave shielding layer disclosed in Patent Document 1, in order to ensure the connection stability between the grounding portion and the shielding film, it is necessary to increase the opening area of ​​the through hole 123. However, if the opening area is increased, the freedom of circuit design will be reduced.

[0011] In view of the above, an object of the present invention is to provide a shielded printed wiring board having excellent connection stability even when the opening area of ​​the through hole is small and having a high degree of freedom in circuit design.

[0012] Another object of the present invention is to provide a method for easily manufacturing a shielded printed wiring board having excellent connection stability and high freedom of circuit design even when the opening area of ​​the through hole is small.

[0013] Technical means to solve technical problems

[0014] The inventor of the present application has made careful research to achieve the above-mentioned purpose and found that, in an electromagnetic wave shielding film having a through hole provided in a conductive adhesive layer and an insulating layer in a form penetrating in the thickness direction, a shielded printed wiring board laminated with an electromagnetic wave shielding film having a structure in which the conductive adhesive layer extends further into the through hole than the insulating layer has excellent connection stability and a high degree of freedom in circuit design even when the opening area of ​​the through hole is small. The present invention is completed based on the above-mentioned insights.

[0015] That is, the present invention provides a shielded printed circuit board, which includes a printed circuit board, an insulating layer, and a conductive adhesive layer arranged between the printed circuit board and the insulating layer, wherein the printed circuit board contains a basic component, a circuit pattern provided on the surface of the basic component, and an insulating protective layer covering the circuit pattern, the shielded printed circuit board contains a through hole for external grounding connection that penetrates the insulating layer and the conductive adhesive layer in the thickness direction, and the conductive adhesive layer contains an extension portion that extends further into the through hole than the insulating layer.

[0016] The shielded printed circuit board of the present invention includes a printed circuit board, a conductive adhesive layer, and an insulating layer. The shielded printed circuit board of the present invention contains a through hole for external ground connection that penetrates the insulating layer and the conductive adhesive layer in the thickness direction. In addition, the conductive adhesive layer contains an extension that extends further into the through hole than the insulating layer. The shielded printed circuit board of the present invention contains the extension as described above. When the conductive adhesive layer is electrically connected to the external ground using an external ground connection component, the contact area between the conductive material in the external ground connection component and the conductive adhesive layer is larger than when there is no extension. Therefore, even when the opening area of ​​the through hole is small, it has excellent connection stability. In addition, since the opening area of ​​the through hole can be reduced, the circuit design has a high degree of freedom.

[0017] Preferably, the angle formed by the lower side of the extension and the upper side of the extension at the terminal of the extension is an acute angle. Since the angle is an acute angle, the extension and the vicinity of the insulating protective layer are also easily filled when the conductive material of the external grounding connection member flows into the through hole by thermocompression bonding, and it is difficult to generate voids in the conductive material filled into the through hole. If there are voids, the shielded printed wiring board is heated in the subsequent component mounting process (reflow process) and the voids expand, and the connection between the conductive material and the shielding film may be damaged.

[0018] Preferably, the angle formed by the vertical plane relative to the lower side of the extension part at the starting end of the extension part and the upper side of the extension part is an acute angle. Since the angle is an acute angle, when the conductive material in the external grounding connection component flows into the through hole by thermocompression bonding, the extension part and the vicinity of the insulating layer are also easily filled, and it is difficult to generate voids in the conductive material filled into the through hole. If there are voids, the shielded printed circuit board is heated in the subsequent component installation process (reflow process) and the voids expand, and the connection between the conductive material and the shielding film and the grounding connection component may be damaged.

[0019] In addition, the present invention provides a method for manufacturing a shielded printed circuit board, the method for manufacturing a shielded printed circuit board comprising the following steps: a shielded printed circuit board body preparation step, preparing a shielded printed circuit board body, the shielded printed circuit board body comprising a printed circuit board containing a circuit pattern, an insulating layer, and a conductive adhesive layer (i) arranged between the printed circuit board and the insulating layer, and comprising a through hole for external grounding connection that penetrates the insulating layer and the conductive adhesive layer (i) in the thickness direction; an external grounding connection component lamination step, laminating an external grounding connection component including a conductive adhesive layer (ii) on the upper side of the through hole and making the conductive adhesive layer (ii) contact the shielded printed circuit board body; a hot pressing step, through hot pressing, making the conductive adhesive layer (i) extend further into the through hole than the insulating layer and making the conductive adhesive layer (ii) flow into the through hole, so that the conductive adhesive layer (i) abuts against the conductive adhesive layer (ii).

[0020] The manufacturing method of the shielded printed circuit board of the present invention includes a shielded printed circuit board body preparation process, an external ground connection component lamination process and a thermocompression bonding process. The shielded printed circuit board body preparation process is a process of preparing a shielded printed circuit board body including a printed circuit board, a conductive adhesive layer (i) and an insulating layer. The shielded printed circuit board body contains a through hole for external ground connection that penetrates the insulating layer and the conductive adhesive layer (i) in the thickness direction. The external ground connection component lamination process is a process of laminating an external ground connection component including a conductive adhesive layer (ii) on the upper side of the through hole so that the conductive adhesive layer (ii) contacts the shielded printed circuit board body. In addition, the thermocompression bonding process is a process of making the conductive adhesive layer (i) extend into the through hole and making the conductive adhesive layer (ii) flow into the through hole by thermocompression bonding. Through the thermocompression bonding process, the conductive adhesive layer (i) abuts against the conductive adhesive layer (ii).

[0021] The manufacturing method of the shielded printed circuit board of the present invention includes the thermocompression bonding step, and can make the conductive adhesive layer (i) soften and extend into the through hole by thermocompression bonding once, and at the same time make the conductive adhesive layer (ii) soften and flow into the through hole, so that the shielded printed circuit board including the extended portion can be easily manufactured. Therefore, even when the opening area of ​​the through hole is small, the shielded printed circuit board with excellent connection stability and high freedom of circuit design can be easily manufactured.

[0022] The conductive adhesive layer (i) preferably has a loss tangent of 0.1 to 0.7 at 150°C. When the loss tangent is 0.1 or more, excessive extension of the conductive adhesive layer (i) during thermocompression bonding can be suppressed. When the loss tangent is 0.7 or less, the conductive adhesive layer (i) easily extends during thermocompression bonding, thereby making it easier to manufacture a shielded printed wiring board including the extended portion.

[0023] Effects of the Invention

[0024] The shielded printed circuit board of the present invention has excellent connection stability even when the opening area of ​​the through hole is very small. Therefore, the circuit design can be freely performed compared with the conventional shielded printed circuit board. In addition, the manufacturing method of the shielded printed circuit board according to the present invention can easily manufacture a shielded printed circuit board that has excellent connection stability and high freedom of circuit design even when the opening area of ​​the through hole is very small. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [ Figure 1 ] A schematic cross-sectional view of an embodiment of a shielded printed circuit board of the present invention;

[0026] [ Figure 2 ] A schematic cross-sectional view of another embodiment of the shielded printed circuit board of the present invention;

[0027] [ Figure 3 ] Figure 2 A magnified view of the area around 21b;

[0028] [ Figure 4 ] A schematic cross-sectional view of an embodiment of a method for manufacturing a shielded printed circuit board of the present invention;

[0029] [ Figure 5 ] A cross-sectional schematic diagram of another embodiment of the method for manufacturing a shielded printed circuit board of the present invention;

[0030] [ Figure 6 ]A schematic cross-sectional view of an embodiment of a conventional shielded printed circuit board. DETAILED DESCRIPTION

[0031] [Shielded printed circuit board]

[0032] The shielding printed circuit board of the present invention includes a printed circuit board, a conductive adhesive layer, and an insulating layer. The conductive adhesive layer is arranged between the printed circuit board and the insulating layer. The printed circuit board contains a base component, a circuit pattern provided on the surface of the base component, and an insulating protective layer covering the circuit pattern. The shielding printed circuit board of the present invention contains a through hole for external grounding connection that penetrates the insulating layer and the conductive adhesive layer in the thickness direction. In addition, the conductive adhesive layer contains an extension portion that extends further into the through hole than the insulating layer. In addition, in this specification, the conductive adhesive layer in the electromagnetic wave shielding laminate is sometimes referred to as "conductive adhesive layer (I)".

[0033] An embodiment of the shielded printed wiring board of the present invention will be described below. Figure 1 It is a schematic cross-sectional view of one embodiment of the shielded printed wiring board of the present invention.

[0034] like Figure 1 As shown, the shielded printed wiring board 1 includes a printed wiring board 10, a conductive adhesive layer (conductive adhesive layer (I)) 21, and an insulating layer 22. The conductive adhesive layer 21 is arranged between the printed wiring board 10 and the insulating layer 22. The shielded printed wiring board 1 contains a through hole 23 for external ground connection that penetrates the insulating layer 22 and the conductive adhesive layer 21 in the thickness direction. In addition, the conductive adhesive layer 21 contains an extension portion 21a that extends further into the through hole 23 than the insulating layer 22. In addition, the laminate 20 including the conductive adhesive layer 21 and the insulating layer 22 containing the through hole 23 is sometimes referred to as an "electromagnetic wave shielding laminate". The shielded printed wiring board 1 also contains an external ground connection component 40 on the through hole 23.

[0035] (Printed Circuit Board)

[0036] The printed wiring board 10 includes a base member 11, a circuit pattern 13 partially provided on the surface of the base member 11, an insulating protective layer (cover film) 14 covering the circuit pattern 13 and insulating and protecting it, and an adhesive layer 12 for covering the circuit pattern 13 and bonding the circuit pattern 13 and the base member 11 to the insulating protective layer 14. The circuit pattern 13 includes a plurality of signal circuits.

[0037] The circuit pattern 13 is appropriately designed according to the purpose of the shielded printed wiring board. The circuit pattern 13 may contain a ground circuit in addition to a signal circuit.

[0038] The above-mentioned basic member in the above-mentioned printed circuit board is appropriately selected according to the type of the printed circuit board, and can be listed as a rigid substrate, a flexible substrate, and a rigid-flexible substrate. For example, the rigid substrate can be listed as an epoxy glass substrate, a composite glass substrate, a Teflon (registered trademark) substrate, a ceramic substrate, etc.

[0039] The constituent materials of the above-mentioned base member include well-known or commonly used engineering plastics, such as polyethylene terephthalate, polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyetherimide, polyphenylene sulfide, etc. The above-mentioned materials may be used alone or in combination of two or more.

[0040] The base member is preferably a polyester film from the viewpoint of cost, a polyphenylene sulfide film from the viewpoint of excellent flame retardancy, and a polyimide film, a polyamide film, or an epoxy glass film from the viewpoint of excellent heat resistance. The thickness of the base member is not particularly limited, but is preferably 5 to 100 μm.

[0041] The constituent materials of the above-mentioned circuit graphics are not particularly limited, and conductive materials such as metals such as Cu, Al, Au, Ag, Ni, Pd, Sn, Cr, W, Fe, Ti, and alloys of two or more of the above-mentioned metals such as SUS can be listed.

[0042] The insulating protective layer plays a role in protecting the circuit pattern and has insulating properties, and is a layer that can withstand the heat compression bonding process described later. The insulating protective layer can include inorganic films and organic films. The constituent materials of the inorganic film can include silicon oxide, silicon nitride, nitrogen-containing silicon oxide, etc. The constituent materials of the organic film can include resins and polybenzoxazoles, etc., which are examples of the constituent materials of the above-mentioned basic components. The insulating protective film can be a single layer or a multilayer.

[0043] The adhesive layer may use a well-known or commonly used bonding resin. Examples of the bonding resin include the resins exemplified as the binder resin used in the conductive adhesive layer (I) described below. The bonding resin may be used alone or in combination of two or more.

[0044] (Electromagnetic wave shielding laminate)

[0045] In the electromagnetic wave shielding laminate 20, the conductive adhesive layer 21 and the insulating layer 22 are sequentially laminated on the printed wiring board 10, specifically, laminated on the insulating protective layer 14 in the printed wiring board 10. The conductive adhesive layer 21 and the insulating layer 22 contain a through hole 23 that penetrates in the thickness direction (i.e., exposed on the surface of the printed wiring board 10). By containing the through hole 23, the conductive adhesive layer 21 and the conductive material 41 in the external grounding connection component 40 can contact and be electrically connected at the through hole 23. The bottom of the through hole 23 is the printed wiring board 10, specifically, the insulating protective layer 14. That is, the through hole 23 is formed by the side of the insulating layer 22, the upper side of the extension 21a, and the surface of the printed wiring board 10 (especially the insulating protective layer 14).

[0046] The conductive adhesive layer 21 includes an extension portion 21a that extends further into the through hole 23 than the insulating layer 22. The extension portion 21a is a portion of the conductive adhesive layer 21 without the insulating layer 22 on the upper portion, and the upper side surface is not covered by the insulating layer 22. By including such an extension portion 21a, when the conductive adhesive layer 21 is electrically connected to the external ground 50 described later by the external ground connection member 40, the contact area between the conductive material 41 in the external ground connection member 40 and the conductive adhesive layer 21 is larger than when there is no extension portion 21a (for example, Figure 6 The substrate 100 with the electromagnetic wave shielding layer shown is large, so it has excellent connection stability even when the opening area of ​​the through hole 23 (the area when the through hole 23 is viewed from the upper side) is small. In addition, since the opening area of ​​the through hole 23 can be reduced, the circuit design has a high degree of freedom.

[0047] The shape of the extension is not particularly limited and can be Figure 1 The extension 21a shown in the figure may be annular (hollow cylindrical, hollow prism, amorphous hollow column, etc.), or may be Figure 2 The thickness (height) of the extended portion 21b shown in the figure may be a shape (terraced, stepped, etc.) in which the thickness (height) decreases continuously or stepwise from the beginning to the end, or a shape combining the above shapes. In addition, the thickness of the extended portion may be the same as the thickness of the portion other than the extended portion of the conductive adhesive layer 21, or may be very thin.

[0048] The shape of the through hole 23 formed with such an extension 21a (the shape of the portion corresponding to the missing portion of the conductive adhesive layer 21) can be a roughly columnar shape (cylindrical, prism-shaped, amorphous columnar, etc.). In addition, the shape of the through hole 23 formed with the extension 21b can be a roughly truncated cone shape with the insulating protective layer 14 side as the upper base.

[0049] like Figure 2 As shown, the angle formed by the lower side surface of the extension portion and the upper side surface of the extension portion at the terminal portion of the extension portion (the portion where the extension of the conductive adhesive layer (I) into the through hole ends) is preferably an acute angle, more preferably 70° or less, further preferably 60° or less, and particularly preferably 45° or less. If the above angle is a right angle or an obtuse angle, when the conductive material in the external ground connection member is filled into the through hole, the conductive material will not be filled into the extension portion in the terminal portion and the vicinity of the insulating protective layer, resulting in a gap. In the subsequent component mounting process (reflow process), the shielded printed wiring board is heated and the gap expands, and the connection between the conductive material and the shielding film may be damaged.

[0050] In addition, the angle formed by the vertical plane relative to the lower side surface of the extension portion at the starting end portion of the extension portion (the portion where the conductive adhesive layer (I) starts to extend into the through hole) and the upper side surface of the extension portion is preferably an acute angle, more preferably 70° or less, further preferably 60° or less, and particularly preferably 45° or less. If the above angle is a right angle or an obtuse angle, when the conductive material in the external ground connection member is filled into the through hole, the conductive material will not be filled into the vicinity of the extension portion and the insulating layer, resulting in a gap. In the subsequent component mounting process (reflow process), the gap expands after the shielded printed wiring board is heated, and the connection between the conductive material and the shielding film may be damaged.

[0051] exist Figure 3 Show Figure 2 The periphery of the extension 21b shown ( Figure 2 The extension portion 21b is an enlarged view of the portion surrounded by a circle (in the figure). The extension portion 21b is an area surrounded by the lower side surface f1, the upper side surface f2 and the vertical surface f3 relative to the lower side surface f1 of the extension portion. The angle r2 formed by the lower side surface f1 of the extension portion and the upper side surface f2 of the extension portion in the terminal portion 21b-1 of the extension portion 21b is an acute angle. In addition, the angle r1 formed by the vertical surface f3 relative to the lower side surface f1 of the extension portion and the upper side surface f2 of the extension portion in the starting end portion 21b-2 of the extension portion 21b is an acute angle.

[0052] The shape of the opening of the through hole (the shape when the through hole is viewed from the upper side) is not particularly limited and can be set to a perfect circle, a circle such as an ellipse, a polygon such as a quadrilateral, etc. as needed. The opening area of ​​the through hole is preferably 0.01 to 100 mm2, more preferably 0.1 to 80 mm2, and further preferably 0.1 to 50 mm2. By making the opening area of ​​the through hole within the above range, the connection stability and electromagnetic wave shielding with the external ground 50 described later can be further improved. When the opening is preferably circular, the diameter of the opening is preferably 0.5 to 5 mm, more preferably 0.5 to 3 mm, and further preferably 0.8 to 3 mm.

[0053] The number of through holes may be one or more, but from the viewpoint of further strengthening the ground connection, a plurality of through holes is preferable.

[0054] The ratio of the opening area of ​​the through hole to the attachment area of ​​the external ground connection member is preferably 0.1 to 90%, more preferably 1 to 70%. When the ratio is within the above range, the bonding strength of the conductive material in the external ground connection member and the grounding reliability are further improved.

[0055] The above-mentioned method for forming the extension portion can be listed as follows: a method using an electromagnetic wave shielding laminate having a pre-formed through hole and containing an extension portion; a method using an electromagnetic wave shielding film having a pre-formed through hole but no extension portion, and softening the conductive adhesive layer by thermal compression bonding and causing it to flow into the through hole to form the extension portion. In addition, the through hole in the electromagnetic wave shielding laminate can be formed before lamination to the printed wiring board, or it can be formed after lamination to the printed wiring board. The through hole can be formed by punching, laser processing, etc.

[0056] The conductive adhesive layer (I) in the electromagnetic wave shielding laminate plays a role in preventing electromagnetic waves generated from the circuit pattern from leaking to the outside and shielding the circuit from electromagnetic waves (noise) from the outside.

[0057] The conductive adhesive layer (I) preferably contains a binder resin and conductive particles. The binder resin has a function of binding other components in the conductive adhesive layer (I) to form a pattern.

[0058] The binder resin may include cured products of thermoplastic resins and thermosetting resins, and cured products of thermosetting resins are preferred from the viewpoint of excellent heat resistance in the reflow process. In addition, if there is no heating process such as the reflow process in the subsequent process, a thermoplastic resin is preferred. The binder resin may be used alone or in combination of two or more.

[0059] Examples of the thermosetting resins include phenolic resins, epoxy resins, polyurethane resins, melamine resins, alkyd resins, etc. Examples of the thermoplastic resins include polystyrene resins, polyvinyl acetate resins, polyester resins, polyolefin resins (such as polyethylene resins, polypropylene resins, etc.), polyimide resins, polyamide resins, rubber resins, acrylic resins, etc.

[0060] The binder resin is preferably a resin that is softened by heat, from the viewpoint that the components forming the conductive adhesive layer (I) can easily flow and extend into the through-hole by thermal compression bonding, and can easily flow into and fill the opening of the insulating protective layer provided on the upper part of the grounding circuit when the printed wiring board contains the grounding circuit.

[0061] Examples of the conductive particles include metal particles, metal-coated resin particles, carbon-based fillers, etc. The conductive particles may be used alone or in combination of two or more.

[0062] Examples of the metal constituting the coating of the metal particles and the metal-coated resin particles include gold, silver, copper, nickel, zinc, etc. The metals may be used alone or in combination of two or more.

[0063] Specifically, the metal particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, silver-coated alloy particles, etc. The silver-coated alloy particles include, for example, copper-containing alloy particles (such as copper alloy particles made of an alloy of copper, nickel and zinc) coated with silver, etc. The metal particles can be produced by electrolysis, atomization, reduction, etc.

[0064] The conductive particles may be spherical, flaky (scaly), dendritic, fibrous, amorphous (polyhedral), etc. Among them, flaky particles are preferred from the viewpoint of lower resistance of the conductive adhesive layer (I) and better shielding properties.

[0065] The insulating layer is provided on the surface side of the electromagnetic wave shielding laminated body more than the conductive adhesive layer (I), thereby insulating and protecting the conductive adhesive layer (I) and preventing short circuit when in contact with other conductive components. Preferably, the insulating layer contains a binder resin. The binder resin can include the resins exemplified and described as the binder resin in the conductive adhesive layer (I). The binder resin can be used alone or in combination of two or more.

[0066] The electromagnetic wave shielding laminate may contain a metal layer between the insulating layer and the conductive adhesive layer (I). When the metal layer is contained, the through hole penetrates the insulating layer, the metal layer and the conductive adhesive layer (I). When the conductive material is made to flow into the through hole for electrical connection so as to be connected to the external grounding connection component, the metal layer becomes the base of the reinforced insulating layer, so that the pressure during the hot pressing is easily transmitted to the conductive material, which can promote the flow and more effectively ensure the connection between the external grounding connection component and the conductive adhesive layer (I).

[0067] The electromagnetic wave shielding laminate may contain other layers in addition to the conductive adhesive layer (I) and the insulating layer. Examples of the other layers include a hard coat layer, a water vapor barrier layer, an oxygen barrier layer, a thermal conductive layer, a low dielectric constant layer, a high dielectric constant layer, and a heat resistance imparting layer.

[0068] (External ground connection member)

[0069] The external ground connection member 40 contains a conductive material 41 and a ground connection member 42, which is configured in the form of blocking the opening of the through hole 23 in the electromagnetic wave shielding laminate 20 so that the conductive adhesive layer 21 and the conductive material 41 are in contact and electrically connected. The conductive material 41 is arranged on the electromagnetic wave shielding laminate 20 side, and has the function of filling the through hole 23 and electrically connecting to the conductive adhesive layer 21 in the through hole 23. The ground connection member 42 is arranged on the external ground 50 side, and has the function of electrically connecting the external ground 50 and the conductive material 41.

[0070] The conductive material is preferably a conductive adhesive layer. In the present specification, the conductive adhesive layer in the external ground connection member may be referred to as a "conductive adhesive layer (II)".

[0071] The conductive adhesive layer (II) preferably contains a binder resin and conductive particles. The binder resin has a function of binding other components in the conductive adhesive layer (II) to form a pattern.

[0072] In addition, the content ratio of the conductive particles is not particularly limited, but is preferably 5% by mass or more relative to 100% by mass of the conductive adhesive layer (II), and more preferably 40% by mass or more. In addition, the above content ratio is preferably 95% by mass or less, and more preferably 90% by mass or less. When the above content ratio is 5% by mass or more, the connection stability between the conductive adhesive layer (II) and the conductive material is good. When the above content ratio is 95% by mass or less, the close adhesion between the conductive adhesive layer (II) and the insulating protective layer of the printed wiring board is good.

[0073] The binder resin may include the resins exemplified and described as the binder resin in the conductive adhesive layer (I). The binder resin may be used alone or in combination of two or more. Among them, a cured product of a thermosetting resin is preferred from the viewpoint of filling the through-hole and thermally curing by thermocompression bonding to achieve electrical connection with the conductive adhesive layer (I).

[0074] The binder resin is preferably a resin that softens by heat, from the viewpoint that the components forming the conductive adhesive layer (II) can easily flow and flow into and fill the through-holes by thermocompression bonding.

[0075] Examples of the conductive particles include the particles exemplified and described as the conductive particles in the conductive adhesive layer (I). The conductive particles may be used alone or in combination of two or more.

[0076] The conductive adhesive layer (II) may contain a tackifier. Examples of the tackifier include aliphatic hydrocarbon resins, C5 / C9 mixed resins, rosin, rosin derivatives, terpene resins, aromatic hydrocarbon resins, and thermo-reactive resins.

[0077] The ground connection member may be a metal plate made of gold, silver, copper, aluminum, iron, nickel, or an alloy of two or more of the above metals. Among them, copper, aluminum, nickel, and silver are preferred from the viewpoints of conductivity, cost, and chemical stability as a ground connection member.

[0078] The shielded printed wiring board 1 is designed to assemble a shielded printed wiring board body 30 with an external ground connection member 40, and connects and grounds the conductive adhesive layer (I) 21 to the external ground 50 through a conductive material 41 and a ground connection member 42. The ground connection member 42 and the external ground 50 are connected by a gasket and a conductive adhesive sheet (not shown).

[0079] (External ground)

[0080] The external ground (grounding portion) 50 is a conductive member and can be a conductive plate disposed inside the electronic device body, a metal plated portion of the housing, a metal plate attached to the housing, a cover that can be attached and detached, or the like.

[0081] The shielded printed circuit board of the present invention including an external grounding connection member and an externally grounded electronic device electrically connected to the external grounding connection member can strengthen the grounding connection and make the shielded printed circuit board body have shape retention by using the external grounding connection member. By attaching a certain area of ​​the external grounding connection member to the upper side of the electromagnetic wave shielding laminate, the force of the shape recovery of the laminate can be suppressed when the shielded printed circuit board is bent, and the shape of the bent state can be maintained. Therefore, it is preferred that the shielded printed circuit board of the present invention is a flexible printed circuit board (FPC).

[0082] [Method for manufacturing shielded printed wiring board]

[0083] The manufacturing method of the shielded printed circuit board of the present invention includes the following steps: a step of preparing a shielded printed circuit board body (shielded printed circuit board body preparation step), wherein the shielded printed circuit board body includes a printed circuit board containing a circuit pattern, an insulating layer, and a conductive adhesive layer (i) arranged between the above-mentioned printed circuit board and the above-mentioned insulating layer, and includes a through hole for external grounding connection that penetrates the above-mentioned insulating layer and the above-mentioned conductive adhesive layer (i) in the thickness direction; a step of laminating an external grounding connection component including a conductive adhesive layer (ii) on the upper side of the above-mentioned through hole and making the above-mentioned conductive adhesive layer (ii) contact the above-mentioned shielded printed circuit board body (external grounding connection component lamination step); a step of making the above-mentioned conductive adhesive layer (i) extend further into the through hole than the above-mentioned insulating layer and making the above-mentioned conductive adhesive layer (ii) flow into the through hole by hot pressing, so that the above-mentioned conductive adhesive layer (i) abuts against the above-mentioned conductive adhesive layer (ii) (hot pressing step). In addition, the manufacturing method of the shielded printed wiring board of the present invention may be simply referred to as "the manufacturing method of the present invention."

[0084] use Figure 4 One embodiment of the production method of the present invention will be described.

[0085] (Shielded printed circuit board body preparation process)

[0086] In the shielded printed circuit board main body preparation process, for example Figure 4 The shielded printed wiring board body 30' shown in (c) in the figure includes a printed wiring board 10 including a circuit pattern, an insulating layer 22, and a conductive adhesive layer (i) 21' arranged between the printed wiring board 10 and the insulating layer 22. In addition, the prepared shielded printed wiring board body 30' includes a through hole 23 for external ground connection that penetrates the insulating layer 22 and the conductive adhesive layer (i) 21' in the thickness direction. In addition, in this specification, a shielded printed wiring board that does not include a component for external ground connection (such as a shielded printed wiring board 30 composed of a printed wiring board 10 and an electromagnetic wave shielding laminate 20, and a shielded printed wiring board 30' composed of a printed wiring board 10 and an electromagnetic wave shielding film 20') is sometimes referred to as a "shielded printed wiring board body". However, the shielded printed wiring board body is also equivalent to the shielded printed wiring board.

[0087] like Figure 4 As shown in (a) in FIG. 1 , in one embodiment of the shielded printed wiring board main body preparation process, first, a printed wiring board 10 is prepared, wherein the printed wiring board 10 includes a base member 11, a circuit pattern 13 partially provided on the base member 11, an insulating protective layer 14 for insulating and protecting the circuit pattern 13, and an adhesive layer 12 for covering the circuit pattern 13 and bonding the circuit pattern 13 and the base member 11 to the insulating protective layer 14. Alternatively, a printed wiring board including a signal circuit and a ground circuit as the circuit pattern 13 and including a via formed in the insulating protective layer on the ground circuit may be used instead. Figure 4 The printed wiring board 10 shown in (a) in FIG. 1 can be formed by laser processing, for example. Alternatively, an insulating protective film having a via hole formed therein beforehand may be laminated.

[0088] Then, if Figure 4 As shown in (b), an electromagnetic wave shielding film 20' is laminated on the insulating protective layer 14 of the printed wiring board 10, and the electromagnetic wave shielding film 20' is a laminate of a conductive adhesive layer (i) 21' and an insulating layer 22. When a via hole is formed in the insulating protective layer of the printed wiring board, thermal compression bonding can be performed after lamination so that the conductive adhesive layer (i) 21' fills the via hole. For example, the electromagnetic wave shielding film is heated and pressurized by a thermal compression bonding machine to perform thermal compression bonding.

[0089] Then, if Figure 4As shown in (c), a through hole 23 is formed in the form of penetrating the conductive adhesive layer (i) 21' and the insulating layer 22 at a position corresponding to the mounting portion of the external ground connection member of the laminated electromagnetic wave shielding film 20'. The through hole 23 is formed by laser processing, for example. The conductive adhesive layer (i) 21' flows and solidifies during the thermocompression bonding in the thermocompression bonding step described later to form a conductive adhesive layer (I), and an electromagnetic wave shielding laminate is formed.

[0090] The loss tangent of the conductive adhesive layer (i) at 150°C is preferably 0.1 to 0.7, more preferably 0.1 to 0.4. When the above loss tangent is 0.1 or more, excessive extension of the conductive adhesive layer (i) during thermocompression bonding can be suppressed. When the above loss tangent is 0.7 or less, the conductive adhesive layer (i) is easy to extend during thermocompression bonding, so it is easier to manufacture a shielded printed circuit board containing the extended portion. The above loss tangent at 150°C can be obtained by measuring, for example, using a rheometer (product name "R302" manufactured by Anton Paar) in the range of 30 to 200°C. The measurement sample uses a disc-shaped object in which the conductive adhesive layer (i) is molded into a diameter of 25 mm and a thickness of 1 mm. In addition, the measurement conditions of the rheometer can be the following conditions:

[0091] Plate: D-PP25 / AL / S07, diameter 25mm

[0092] Amplitude: 0.1%

[0093] Frequency: 1Hz

[0094] Measuring range: 30~200℃

[0095] Heating rate: 6℃ / min.

[0096] The conductive adhesive layer (i) preferably contains a binder component and conductive particles. Examples of the binder component include binder resin components that may be contained in the conductive adhesive layer (I).

[0097] The binder component is preferably at least one of a thermoplastic resin and a thermosetting resin. Thermosetting resins are preferred from the viewpoint of excellent heat resistance in the reflow process, and thermoplastic resins are preferred when there is no heating process such as the reflow process in the subsequent process. The thermoplastic resin and the thermosetting resin can be exemplified and described as the thermoplastic resin and the thermosetting resin in the conductive adhesive layer (I). The binder component may be used alone or in combination of two or more.

[0098] Examples of the conductive particles include the particles exemplified and described as the conductive particles that may be contained in the conductive adhesive layer (I). The conductive particles may be used alone or in combination of two or more.

[0099] When the binder component includes a thermosetting resin, a curing agent for promoting a thermosetting reaction may also be included as a component of the binder component. The type of curing agent can be appropriately selected according to the type of functional group contained in the thermosetting resin. The curing agent can include, for example, isocyanate curing agents, phenol curing agents, imidazole curing agents, amine curing agents, cationic curing agents, etc. The curing agent can be used alone or in combination of two or more.

[0100] (External ground connection component lamination process)

[0101] In the external ground connection member laminating step, the external ground connection member 40 ′ including the conductive adhesive layer (ii) 41 ′ is laminated on the upper side of the through hole 23 so that the conductive adhesive layer (ii) 41 ′ contacts the shield printed wiring board body 30 ′ (eg, the insulating layer 22 ).

[0102] Specifically, if Figure 4 As shown in (d), in the external grounding connection member lamination step, the surface of the conductive adhesive layer (ii) 41 ′ of the external grounding connection member 40 ′ which is cut into any size by laminating the conductive adhesive layer (ii) 41 ′ and the grounding connection member 42 is arranged on the surface of the insulating layer 22 in such a manner as to block the opening of the through hole 23 .

[0103] (Thermocompression bonding process)

[0104] In the thermocompression bonding step, the conductive adhesive layer (i) 21 ′ is extended further into the through hole 23 than the insulating layer 22 and the conductive adhesive layer (ii) 41 ′ is flowed into the through hole 23 , so that the conductive adhesive layer (i) 21 ′ and the conductive adhesive layer (ii) 41 ′ are in contact with each other.

[0105] Specifically, in the thermocompression bonding process, the conductive adhesive layer (i) 21' softens and flows by heating and pressurizing, and extends further into the through hole 23 than the insulating layer 22. Then, it is solidified by subsequent cooling or thermal polymerization to form the conductive adhesive layer (I) 21, and the electromagnetic wave shielding laminate 20 containing the extended portion 21a is formed. In addition, by the above-mentioned heating and pressurizing, the conductive adhesive layer (ii) 41' also softens and flows, and flows into and fills the through hole 23 by the pressure during pressurization. Then, it is solidified by subsequent cooling or thermal polymerization to form the conductive adhesive layer (II) 41, and the external grounding connection component 40 is formed. In this way, the conductive adhesive layer (i) 21' and the conductive adhesive layer (ii) 41' flow and abut against each other by thermocompression bonding. Next, in the shielded printed wiring board 1 obtained by thermocompression bonding, the external ground connection member 40 and the electromagnetic wave shielding laminate 20 are electrically connected by contact between the conductive adhesive layer (I) 21 and the conductive adhesive layer (II) 41 .

[0106] Regarding the extension of the conductive adhesive layer (i) into the through hole, the combination of the loss tangent of the conductive adhesive layer (i) and the conditions during thermocompression bonding (pressure conditions, temperature conditions, etc.) is important.

[0107] The conditions of the heat pressing process such as pressure, temperature, and time can be appropriately selected according to the types of the conductive adhesive layer (i) and the conductive adhesive layer (ii) (especially the types of the adhesive component and the curing agent). The pressure during heat pressing is not particularly limited, and is preferably 1 to 5 MPa. Regarding the temperature during heat pressing, when a thermosetting resin is used as the adhesive component, it is not particularly limited, and is preferably 140 to 200°C. Regarding the heat pressing time, when a thermosetting resin is used as the adhesive component, it is not particularly limited, and is preferably 1 to 60 minutes. However, if the thermosetting resin can flow, it can also be cured before heat pressing.

[0108] In addition, Figure 5 Another embodiment of the production method of the present invention will be described.

[0109] Figure 5 The manufacturing method of the present invention shown in FIG. 1 has the following differences: in the shielded printed circuit board main body preparation step, as shown in FIG. Figure 5 As shown in (b) of FIG. 1 , an electromagnetic wave shielding film 20 ′ having through holes 23 formed therein beforehand is laminated instead of laminating Figure 4 The electromagnetic wave shielding film 20' shown in (b) does not include a through hole. In this embodiment, the through hole is formed in the electromagnetic wave shielding film before lamination to the printed wiring board, so the through hole can be formed not only by laser processing but also by easier punching processing, making it easier to form the through hole.

[0110] In addition to the above contents, the rest of this embodiment is the same as Figure 4The manufacturing method of the present invention is the same as shown. Figure 5 The stage of the printed wiring board 10 shown in (a) Figure 5 The external ground connection member lamination step shown in (c) and Figure 5 The heat pressing process shown in (d) is respectively Figure 4 The stage of the printed wiring board 10 shown in (a) Figure 4 The external ground connection member lamination step shown in (d) and Figure 4 The thermal compression bonding step shown in (e) is the same.

[0111] The shielded printed wiring board of the present invention can be manufactured as described above.

[0112] The manufacturing method of the present invention can make the conductive adhesive layer (I) extend further into the through hole than the insulating layer to form an extension portion by thermal compression, so there is no need to go through the process of forming the extension portion by punching and cutting. In addition, the above-mentioned extension portion can be formed by thermal compression once and the conductive adhesive layer (ii) can be made to flow into the through hole. Therefore, the shielded printed circuit board of the present invention can be easily manufactured. Therefore, according to the manufacturing method of the present invention, a shielded printed circuit board with excellent connection stability and high freedom of circuit design can be easily manufactured even when the opening area of ​​the through hole is small.

[0113] Reference numerals

[0114] 1 Shielded printed circuit board

[0115] 10. Printed Circuit Board

[0116] 11 Basic components

[0117] 12 Adhesive layer

[0118] 13 Circuit Graphics

[0119] 14 Insulation protective layer (covering film)

[0120] 20 Electromagnetic wave shielding laminate

[0121] 21 Conductive adhesive layer (conductive adhesive layer (I))

[0122] 22 Insulation layer

[0123] 23 Through Holes

[0124] 30 Shielded printed circuit board (shielded printed circuit board body)

[0125] 40 External ground connection member

[0126] 41 Conductive materials

[0127] 42 Ground connection member

[0128] 50 External ground

[0129] 20' EM wave shielding film

[0130] 21' Conductive adhesive layer (i)

[0131] 30' Shielded PCB (Shielded PCB Body)

[0132] 40' External ground connection member

[0133] 41' Conductive adhesive layer (ii)

Claims

1. A shielded printed circuit board (1), characterized in that The shielded printed circuit board (1) comprises: A printed circuit board (10), an insulating layer (22), and a conductive adhesive layer (21) disposed between the printed circuit board (10) and the insulating layer (22), wherein: The printed circuit board (10) comprises a base component (11), a circuit pattern (13) provided on a surface of the base component (11), and an insulating protective layer (14) covering the circuit pattern (13). The shielded printed wiring board (1) comprises a through hole (23) for external ground connection, which penetrates the insulating layer (22) and the conductive adhesive layer (21) in the thickness direction. The conductive adhesive layer (21) includes an extension portion (21a, 21b) extending further toward the inside of the through hole (23) than the insulating layer (22) in the horizontal direction.

2. The shielded printed circuit board (1) according to claim 1, characterized in that: The angle (r2) formed by the lower side surface (f1) of the extending portion and the upper side surface (f2) of the extending portion in the terminal portion (21b-1) of the extending portion (21b) is an acute angle.

3. The shielded printed circuit board (1) according to claim 1 or 2, characterized in that: The angle (r1) formed by the vertical plane (f3) at the starting end portion (21b-2) of the extending portion relative to the lower side surface (f1) of the extending portion and the upper side surface (f2) of the extending portion is an acute angle.

4. A method for manufacturing a shielded printed circuit board (1), characterized in that The method for manufacturing the shielded printed circuit board (1) comprises the following steps: A shielded printed circuit board body preparation step, preparing a shielded printed circuit board body, the shielded printed circuit board body comprising a printed circuit board (10) containing a circuit pattern, an insulating layer (22), and a first conductive adhesive layer (i) disposed between the printed circuit board (10) and the insulating layer (22), and comprising a through hole (23) for external ground connection that penetrates the insulating layer (22) and the first conductive adhesive layer (i) in a thickness direction; An external grounding connection component laminating step, laminating an external grounding connection component (40) including a second conductive adhesive layer (ii) on the upper side of the through hole (23) so that the second conductive adhesive layer (ii) contacts the shielding printed circuit board body; A thermocompression bonding step, through which the first conductive adhesive layer (i) is made to extend further into the through hole (23) than the insulating layer (22) in the horizontal direction to form an extension portion (21a, 21b) and the second conductive adhesive layer (ii) is made to flow into the through hole (23), so that the first conductive adhesive layer (i) abuts against the second conductive adhesive layer (ii).

5. The method for manufacturing a shielded printed circuit board (1) according to claim 4, characterized in that: The first conductive adhesive layer (i) has a loss tangent of 0.1 to 0.7 at 150°C.

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