Double-layer flexible circuit board structure and manufacturing method thereof

Abstract

The invention discloses a double-layer flexible circuit board structure and a manufacturing method thereof. The double-layer flexible circuit board structure comprises a top micro-column hollowed-out covering layer module, a top micro-column hollowed-out covering layer module and a top micro-column hollowed-out covering layer module, the top reactive hollow conductive layer module is used for bearing top layer electrical connection; the honeycomb core insulating substrate module is used for isolating the top reactive hollow conducting layer module from the bottom reactive hollow conducting layer module and providing a flexible supporting substrate; by means of the parts, the material consumption can be greatly reduced, the overall weight is greatly reduced compared with that of a traditional rigid circuit board, dot matrix supporting is formed by the micro supporting columns, and the hollow conducting layer can be prevented from being deformed due to external force; the hexagonal structure of the honeycomb holes utilizes the mechanical principle to enhance the extrusion resistance of the substrate, so that the edge stress concentration phenomenon is reduced, and the falling resistance and friction resistance can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of double-layer flexible circuit board, in particular to a double-layer flexible circuit board structure and a manufacturing method thereof. BACKGROUND

[0002] The double-layer flexible circuit board structure refers to a circuit integrated structure with excellent bending flexibility and spatial adaptability, in which two layers of conductive circuits etched from copper foil are separated by an insulating substrate, the upper and lower surfaces are covered with a cover film or a coating layer as a protective layer, and electrical connection is achieved between the layers through through-hole metallization.

[0003] However, in use, the traditional double-layer flexible circuit board structure has no hollow design in the conductive layer, the copper foil is fully covered, the insulating substrate is a solid structure, the upper and lower cover films have no micro-pillar support, and the weight and thickness are significantly increased, the installation space is limited, and the portability is poor. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the prior art, and provides a double-layer flexible circuit board structure and a manufacturing method thereof, which can greatly reduce the amount of material by using hollow grid holes and honeycomb holes, and replace the traditional full adhesive layer with micro-pillar connection, and form an air cavity in the space except the micro-pillar, so that the overall weight is greatly reduced compared with the traditional rigid circuit board, and the micro-pillar forms a dot matrix support between the cover layer and the conductive layer, which can avoid deformation of the hollow conductive layer due to external force; the hexagonal structure of the honeycomb hole enhances the extrusion resistance of the substrate by using the principle of mechanics, reduces the edge stress concentration phenomenon, and improves the drop resistance and friction resistance.

[0005] The present application also provides a double-layer flexible circuit board structure and a manufacturing method thereof, which comprises: a top micro-pillar hollow cover layer module for protecting the top conductive circuit from mechanical damage; a top non-functional hollow conductive layer module for bearing the electrical connection of the top layer; a honeycomb core insulating substrate module for isolating the top non-functional hollow conductive layer module and the bottom non-functional hollow conductive layer module, and providing a flexible support base; a bottom non-functional hollow conductive layer module for bearing the electrical connection of the bottom layer; a bottom micro-pillar hollow cover layer module for protecting the bottom conductive circuit from mechanical damage; and a hollow via connection module for realizing vertical conduction of the upper and lower layers, wherein the top non-functional hollow conductive layer module and the bottom non-functional hollow conductive layer module are provided with hollow grid holes, and the top micro-pillar hollow cover layer module and the top non-functional hollow conductive layer module, and the bottom micro-pillar hollow cover layer module and the bottom non-functional hollow conductive layer module are provided with a plurality of micro-pillars, and the honeycomb core insulating substrate module is provided with a plurality of honeycomb holes.

[0006] The manufacturing method of the double-layer flexible circuit board structure comprises the following steps:

[0007] S1: Honeycomb core insulating substrate manufacturing:

[0008] 1) Substrate material pre-processing, laser scanning measurement of substrate flatness, cutting into 300mm x 300mm large plates;

[0009] 2) Honeycomb core structure forming, CO2 laser micro-machining: cutting honeycomb holes at a speed of 100 μm / s, edge chamfer R0.1 mm;

[0010] 3) Hot pressing, pressing at 180°C, 2MPa pressure for 10 minutes, restoring the micro-warping of the PI film caused by laser processing.

[0011] S2: Top / bottom non-functional hollow conductive layer manufacturing:

[0012] 1) Copper foil patterning pre-processing, double-sided coating of adhesive to enhance adhesion with PI, coating of photosensitive dry film with a thickness of 25 μm, 80°C pre-baking for 15 minutes to form a resist layer;

[0013] 2) Non-functional area hollow grid hole etching, core trace area is shielded by film, ultraviolet exposure for 30 seconds, developing solution removes non-functional area dry film, alkaline copper chloride etching solution, temperature 50°C, spray pressure 0.3MPa, etching hollow grid, hole diameter 0.3mm, hole spacing 0.5mm, after stripping, cleaning and drying, AOI detects the edge burrs of the hollow area.

[0014] S3: Top / bottom micro-column hollow cover layer manufacturing:

[0015] 1) Micro-column array mold preparation, silicon-based template, diameter 50 μm, height 20 μm cylindrical array, spacing 100 μm, processed by photoresist micro-molding technology;

[0016] 2) Micro-column structure transfer molding, heating the mold to 120°C, pressing to the cover layer adhesive surface at a pressure of 0.5MPa for 30 seconds, forming PI micro-columns after demolding, leaving the adhesive layer not pressed area as air cavity;

[0017] 3) Cover layer bonding, positioning by automatic placement machine, precisely bonding with the corresponding area of the conductive layer micro-column, hot pressing and curing: 150°C, 1MPa pressure for 5 minutes, forming mechanical anchoring between the micro-column and the conductive layer copper foil.

[0018] S4: Hollow via connection module manufacturing:

[0019] 1) Drilling positioning: laser / mechanical drilling, hole alignment with upper and lower conductive layer traces;

[0020] 2) Hole wall conductive: chemical copper deposition: depositing a thin copper layer on the hole wall to form a conductive path; thickness-limited electroplating: controlling the thickness of the copper layer to keep the hole hollow and not fill the internal space.

[0021] S5: whole board integration and post-processing:

[0022] 1) Laminated compression: according to the order of "top micro-column hollow cover layer module→top non-power hollow conductive layer module→honeycomb core insulating substrate module→bottom non-power hollow conductive layer module→bottom micro-column hollow cover layer module", stack and heat press to form a whole;

[0023] 2) Shape processing: laser cutting circuit board shape, edge chamfering to prevent stress concentration.

[0024] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the aperture of the hollow grid hole is set in the interval of 0.2-0.5 mm, and the hole spacing of the hollow grid hole is set in the interval of 0.3-1 mm.

[0025] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the diameter of the micro pillar is 50 microns, and the height of the diameter of the micro pillar is 20 microns.

[0026] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the side length of the honeycomb hole is 0.5-1 mm, and the hole spacing of the honeycomb hole is set in the interval of 20-30 mm.

[0027] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the material of the honeycomb core insulating substrate module is a polyimide film, and the thickness of the polyimide film is 50 microns.

[0028] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the material of the top non-power hollow conductive layer module and the bottom non-power hollow conductive layer module is an electrolytic aluminum foil.

[0029] According to the double-layer flexible circuit board structure and the manufacturing method thereof provided by the application, the material of the top micro-column hollow cover layer module and the bottom micro-column hollow cover layer module is a PI film.

[0030] Compared with the prior art, the double-layer flexible circuit board structure and the manufacturing method thereof can greatly reduce the material usage through the hollow grid hole and the honeycomb hole, cooperate with the micro pillar connection, replace the traditional full glue layer, and form an air cavity in the space except the micro pillar, so that the overall weight is greatly reduced compared with the traditional rigid circuit board. The micro pillar forms a dot matrix support between the cover layer and the conductive layer, which can avoid deformation of the hollow conductive layer due to external force; the hexagonal structure of the honeycomb hole enhances the extrusion resistance of the substrate by using the mechanical principle, reduces the edge stress concentration phenomenon, and can improve the anti-falling and friction resistance. BRIEF DESCRIPTION OF DRAWINGS

[0031] The application will be further described below in combination with the drawings and examples;

[0032] Fig. 1 Structure flow chart of the double-layer flexible circuit board structure and the manufacturing method thereof;

[0033] Fig. 2 Manufacturing method flow chart of the double-layer flexible circuit board structure and the manufacturing method thereof. DETAILED DESCRIPTION

[0034] This part will describe the specific embodiments of the present application in detail, the preferred embodiments of the present application are shown in the drawings, the role of the drawings is to supplement the description of the text part with graphics, so that people can intuitively and visually understand each technical feature and the overall technical scheme of the present application, but it cannot be understood as a limitation on the protection scope of the present application.

[0035] Reference Figs. 1-2 The double-layer flexible circuit board structure and the manufacturing method thereof, comprising: a top micro-column hollow cover layer module for protecting the top conductive circuit from mechanical damage, a bottom micro-column hollow cover layer module for protecting the bottom conductive circuit from mechanical damage, a plurality of micro-pillars are arranged between the top micro-column hollow cover layer module and the top non-functional hollow conductive layer module, and between the bottom micro-column hollow cover layer module and the bottom non-functional hollow conductive layer module, the diameter of the micro-pillar is 50 microns, the height of the diameter of the micro-pillar is 20 microns, and the material of the top micro-column hollow cover layer module and the bottom micro-column hollow cover layer module is PI film.

[0036] Specifically: the top / bottom micro-column hollow cover layer (PI film material) reduces the amount of material through the hollow grid, and reduces the overall weight; the micro-pillars are distributed in the form of a dot matrix between the cover layer and the conductive layer, forming a composite structure of "rigid support point + flexible matrix"; the anti-damage mechanism: when external mechanical force acts, the micro-pillar disperses the pressure to the entire conductive layer surface through the rigid support, avoiding single-point stress concentration (traditional full glue layer only relies on flexible glue film buffering, with high risk of stress concentration).

[0037] The top non-functional hollow conductive layer module for bearing the top layer electrical connection, the bottom non-functional hollow conductive layer module for bearing the bottom layer electrical connection, the material of the top non-functional hollow conductive layer module and the bottom non-functional hollow conductive layer module is electrolytic aluminum foil, the top non-functional hollow conductive layer module and the bottom non-functional hollow conductive layer module are provided with a hollow grid hole, the aperture of the hollow grid hole is set in the interval of 0.2-0.5mm, and the hole spacing of the hollow grid hole is set in the interval of 0.3-1mm.

[0038] Specifically: the electrolytic aluminum foil is etched by a hollow grid to form a conductive circuit, the hollow area does not affect the conduction of the circuit, only the non-functional copper foil is removed, the integrity of the conductive track is preserved, and the electrical connection between the top layer and the bottom layer is realized; the hollow grid divides the large-area copper foil into flexible units, and each unit can independently deform elastically when bending to release the bending stress (when the traditional full copper foil is bent, the stress is concentrated on the edge, which is easy to produce micro cracks); at the same time, the hollow design reduces the weight of the copper foil, and reduces the pulling effect of the inertial force on the flexible substrate.

[0039] A honeycomb core insulation substrate module is used to isolate the top non-functional hollow conductive layer module and the bottom non-functional hollow conductive layer module, and provide a flexible support base. The honeycomb core insulation substrate module is provided with a plurality of honeycomb holes, the side length of the honeycomb hole is 0.5-1mm, the hole spacing of the honeycomb hole is set in the interval of 20-30mm, and the material of the honeycomb core insulation substrate module is polyimide film. The thickness of the polyimide film is 50 microns.

[0040] Specifically: the honeycomb hole (side length 0.5-1mm, hole spacing 20-30mm) on the polyimide film (thickness 50μm) adopts a hexagonal structure, and uses the principle of geometric mechanics (the load can be uniformly dispersed to each side when the hexagonal vertex is stressed), so that the extrusion resistance of the substrate is improved (the extrusion resistance of the traditional solid substrate depends on the material itself, and there is no structural enhancement); the air cavity formed by the honeycomb hole can also reduce the weight of the substrate.

[0041] A hollow via connection module is used to realize the vertical conduction of the upper and lower layers of the circuit.

[0042] Specifically: the via penetrates the honeycomb core substrate, and the inner wall forms a conductive channel through metallization treatment (such as chemical copper plating), so as to realize the vertical conduction of the top and bottom conductive layers; the hollow structure reduces the amount of via material, and avoids the risk of cracking caused by the difference in thermal expansion when filled with solid.

[0043] The manufacturing method of the double-layer flexible circuit board structure comprises the following steps:

[0044] S1: honeycomb core insulation substrate manufacturing:

[0045] 1) Substrate material pretreatment, laser scanning measurement of substrate flatness, cutting into 300mm×300mm large plate;

[0046] 2) Honeycomb core structure forming, CO2 laser micro machining: cutting honeycomb holes at a speed of 100μm / s, edge chamfer R0.1mm;

[0047] 3) Heat pressing, pressing for 10 minutes at 180℃, 2MPa pressure, recovering the micro-warping of the PI film caused by laser processing.

[0048] S2: top / bottom non-functional hollow conductive layer manufacturing:

[0049] 1) Copper foil patterning pretreatment, double-sided coating of primer to enhance adhesion and PI, coating of photosensitive dry film, thickness 25 pm, pre-baking at 80 °C for 15 minutes to form a resist layer;

[0050] 2) Etching of non-functional area hollow grid, core trace area shielded by film, UV exposure for 30 seconds, development of non-functional area dry film in developer, alkaline copper chloride etching solution, temperature 50 °C, spray pressure 0.3 MPa, etching of hollow grid, aperture 0.3 mm, pitch 0.5 mm, after film removal, cleaning and drying, AOI detection of edge burrs in the hollow area.

[0051] S3: Top / bottom micro-column hollow cover layer manufacturing:

[0052] 1) Micro-column array mold preparation, silicon template, diameter 50 pm, height 20 pm cylindrical array, pitch 100 pm, processed using photoresist micro-molding technology;

[0053] 2) Micro-column structure transfer molding, heating the mold to 120 °C, pressing to the cover layer surface at a pressure of 0.5 MPa for 30 seconds, after demolding, PI micro-columns are formed, leaving the un-pressed area of the adhesive layer as an air cavity;

[0054] 3) Cover layer lamination, positioning by automatic placement machine, precise lamination with the corresponding area of the conductive layer micro-column, thermal compression curing: 150 °C, 1 MPa pressure for 5 minutes, forming mechanical anchoring between the micro-column and the conductive layer copper foil.

[0055] S4: Hollow via connection module manufacturing:

[0056] 1) Drilling positioning: laser / mechanical drilling, hole alignment with upper and lower conductive layer traces;

[0057] 2) Hole wall conductive: chemical copper deposition: depositing a thin copper layer on the hole wall to form a conductive path; thickness-limited electroplating: controlling the thickness of the copper layer to maintain the hollow inside the hole and not fill the internal space.

[0058] S5: Whole plate integration and post-processing:

[0059] 1) Lamination: stacking in the order of "top micro-column hollow cover layer module → top non-functional hollow conductive layer module → honeycomb core insulating substrate module → bottom non-functional hollow conductive layer module → bottom micro-column hollow cover layer module", and thermal compression curing to form a whole;

[0060] 2) Shape processing: laser cutting of the circuit board shape, edge chamfering to prevent stress concentration.

[0061] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims

1. Double-layer flexible circuit board structure, characterized in that: include: A top micro-pillar hollow cover layer module for protecting the top conductive line from mechanical damage; A top non-reactive hollow conductive layer module for carrying top electrical connections; A honeycomb core insulating substrate module is used to isolate the top non-reactive hollow conductive layer module from the bottom non-reactive hollow conductive layer module and provide a flexible support base; a bottom non-reactive hollow conductive layer module is used to carry the bottom electrical connection; a bottom micro-column hollow covering layer module is used to protect the bottom conductive line from mechanical damage; and a hollow via connection module is used to achieve vertical conduction between the upper and lower circuits; The top non-reactive hollow conductive layer module and the bottom non-reactive hollow conductive layer module are both provided with hollow grid holes, a plurality of micro pillars are both provided between the top micro-column hollow covering layer module and the top non-reactive hollow conductive layer module, and between the bottom micro-column hollow covering layer module and the bottom non-reactive hollow conductive layer module, and a plurality of honeycomb holes are provided on the honeycomb core insulating substrate module.

2. The double-layer flexible circuit board structure according to claim 1, characterized in that: The aperture of the hollow grid holes is set in the range of 0.2-0.5 mm, and the hole spacing of the hollow grid holes is set in the range of 0.3-1 mm.

3. The double-layer flexible circuit board structure according to claim 1, characterized in that: The diameter of the micro pillars is 50 microns, and the height of the diameter of the micro pillars is 20 microns.

4. The double-layer flexible circuit board structure according to claim 1, characterized in that: The side length of the honeycomb holes is 0.5-1 mm, and the hole spacing of the honeycomb holes is set in the range of 20-30 mm.

5. The double-layer flexible circuit board structure according to claim 1, characterized in that: The honeycomb core insulating substrate module is made of a polyimide film, and the thickness of the polyimide film is 50 microns.

6. The double-layer flexible circuit board structure according to claim 1, characterized in that: The top non-reactive hollow conductive layer module and the bottom non-reactive hollow conductive layer module are made of electrolytic aluminum foil.

7. The double-layer flexible circuit board structure according to claim 1, characterized in that: The material of the top micro-column hollow covering layer module and the bottom micro-column hollow covering layer module is PI film.

8. A method for manufacturing a double-layer flexible circuit board structure, comprising the following steps: S1: Honeycomb core insulation substrate manufacturing: 1) Pre-process the substrate material, measure the flatness of the substrate by laser scanning, and cut it into 300mm×300mm large panels; 2) Honeycomb core structure molding, CO2 laser micromachining: cutting honeycomb holes at a speed of 100μm / s, with edge chamfers of R0.1mm; 3) Hot pressing: Press at 180℃ and 2MPa pressure for 10 minutes to restore the micro-warping of the PI film caused by laser processing. S2: Top / bottom non-reactive hollow conductive layer manufacturing: 1) Pre-process the copper foil pattern, apply primer on both sides to enhance adhesion with PI, apply photosensitive dry film with a thickness of 25μm, and pre-bake at 80℃ for 15 minutes to form an anti-corrosion layer; 2) Etch the hollow grid holes in the non-functional area, block the core wiring area with film, expose to UV for 30 seconds, remove the dry film in the non-functional area with developer, use alkaline copper chloride etching solution, temperature 50°C, spray pressure 0.3MPa, etch the hollow grid, pore size 0.3mm, pore spacing 0.5mm, clean and dry after film removal, and use AOI to detect burrs on the edge of the hollow area. S3: Fabrication of top / bottom micro-pillar hollow cover layer: 1) Preparation of micro-pillar array mold: silicon-based template, 50 μm diameter, 20 μm height cylindrical array, 100 μm spacing, processed by photoresist micro-molding technology; 2) Transfer molding of micro-column structure: heat the mold to 120℃, press it to the adhesive surface of the cover layer at a pressure of 0.5MPa, hold it for 30 seconds, and form PI micro-columns after demoulding, leaving the unembossed area of ​​the adhesive layer as an air cavity; 3) The cover layer is fitted and positioned by the automatic placement machine, accurately fitted with the corresponding area of ​​the conductive layer micro-pillars, and hot pressing and curing: maintain pressure at 150°C and 1MPa pressure for 5 minutes to form a mechanical anchor between the micro-pillars and the conductive layer copper foil. S4: Hollow via connection module manufacturing: 1) Drilling positioning: laser / mechanical drilling, the hole position is aligned with the upper and lower conductive layer routing; 2) Conductivity of hole wall: Chemical copper deposition: deposit a thin copper layer on the hole wall to form a conductive path; limited thickness electroplating: control the thickness of the copper layer, keep the hole hollow, and do not fill the internal space. S5: Whole board integration and post-processing: 1) Lamination and pressing: stack in the order of "top micro-column hollow covering layer module → top non-reactive hollow conductive layer module → honeycomb core insulation substrate module → bottom non-reactive hollow conductive layer module → bottom micro-column hollow covering layer module", and heat press and solidify to form a whole; 2) Shape processing: Laser cutting the circuit board shape and chamfering the edges to prevent stress concentration.

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